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Any Thoughts About Installing CNG On a Light Piston Aircraft Engine?

03/03/2013 11:58 PM

I have read many posts about CNG vs. gasoline with automotive engines but I am curious as to your thoughts about installing a converison kit on an air cooled aircraft engine such as the IO-360 of 180 to 200 h.p.?

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#1

Re: Any thoughts about installing CNG on a light piston aircraft engine?

03/04/2013 12:41 AM

The tank may be too heavy.

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#6
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Re: Any thoughts about installing CNG on a light piston aircraft engine?

03/04/2013 12:09 PM

Then new 3M CNG tanks Type IV carbon fiber tanks offer up to "10% more capacity at up to 30% lower weight than conventional Type IV tanks of similar geometries." Another company's tanks (Quantum) are already within the realm of reason. For example one they have (#392L) is 136 lbs with a GGE of 24.5. Add the weight of 24.5 of CNG GGE and you get 138 lbs if I did the math right [1 Gasoline US gallon equivalent GGE means 2.567 kg (5.660 lb) of natural gas.]

So the total weight of 274 lbs for the 24.5 GGE. The 100LL AvGas it "replaces" (avoiding the efficiency argument for the moment) weighs 147.5 lbs. for a net tank/fuel increase of about 126.5 lbs. At the moment this component appears acceptable.

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#7
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Re: Any thoughts about installing CNG on a light piston aircraft engine?

03/04/2013 12:18 PM

You have avoided the miner inconvience of FAA certification, the decreased power and range produced by CNG.

I'd be interested about what GGE really means.

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#80
In reply to #6

Re: Any thoughts about installing CNG on a light piston aircraft engine?

03/07/2013 9:46 PM

No, thats a paying customer, or a few more miles. Not going to happen.

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#2

Re: Any thoughts about installing CNG on a light piston aircraft engine?

03/04/2013 12:42 AM

My first thoughts:

.

What are the FAA regulations relating to this?

.

Typically gasoline to CNG conversions see a small decrease power. How much of a drop is expected and how does this change with altitude?

.

CNG conversions are also known for decreasing power as the tank goes from full pressure to lower pressure. What kind of data is available on this?

.

CHG tanks tend to be above 3000psi when full, right? There are regulations governing pressures for Scuba tanks flying aboard aircraft that I think require at least reduced pressure. How heavy do the tanks need to be to assure performance at reduced pressure and temperature?

.

With reduced power and possibly added weight, will this be safe to fly?

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#8
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Re: Any thoughts about installing CNG on a light piston aircraft engine?

03/04/2013 12:29 PM

1. The aircraft would be placed in the "Experimental" category which means pretty much anything goes (within reason) from the FAA perspective.

2. There has been a fascinating discussion on the question of power output on another thread here (see: http://cr4.globalspec.com/thread/77987) with answers all over the place but "it depends" seems to be the best answer so far. That's one reason I mentioned the general engine type which is a fuel injected, four cylinder (compression ratio of 8.7:1) horizontally opposed aircraft engine. The altitude issue is not critical for the experimental aircraft but is a good question. The engine is, or can easily be, turbocharged.

3. I don't know the answer to full to low pressure question as I (perhaps naively) would assume that the regulator would take care of that until empty).

4. The tanks envisioned would be at the standard automotive pressure of 3600 lbs.

5. The aircraft would be generally within design limitations. The power output would be important in terms of performance though the power output question is not clearly resolved.

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#10
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Re: Any thoughts about installing CNG on a light piston aircraft engine?

03/04/2013 12:43 PM

Go for it.

Just remember to always have an alternate emergency landing area in sight.

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#14
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Re: Any thoughts about installing CNG on a light piston aircraft engine?

03/04/2013 2:25 PM

Since when are standard gasoline tanks rated at 3600 psi?

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#18
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Re: Any thoughts about installing CNG on a light piston aircraft engine?

03/04/2013 5:12 PM

He means CNG tanks

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#22
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Re: Any thoughts about installing CNG on a light piston aircraft engine?

03/04/2013 5:44 PM

The tanks envisioned would be at the standard **CNG** automotive pressure of 3600 lbs.

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#30
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Re: Any thoughts about installing CNG on a light piston aircraft engine?

03/04/2013 7:17 PM

Then how much do they weigh? See also post 1. You seem to be ignoring this issue.

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#33
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Re: Any thoughts about installing CNG on a light piston aircraft engine?

03/04/2013 9:16 PM

Read #6 again and if you still don't get it I will explain again.

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#44
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Re: Any thoughts about installing CNG on a light piston aircraft engine?

03/04/2013 10:45 PM

Sorry; I don't know how I missed that. Thanks. However, ~100 lb still sounds like a significant penalty for a small plane.

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#34
In reply to #30

Re: Any thoughts about installing CNG on a light piston aircraft engine?

03/04/2013 9:17 PM

He addressed that in #6 I think. He arrived at a weight penalty of something like 126 lbs I think.

.

If that isn't what you are talking about, then I can understand how the OP might have difficulty understanding what you are saying.

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#19
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Re: Any thoughts about installing CNG on a light piston aircraft engine?

03/04/2013 5:38 PM

#3 I think that even though the regulator is delivering the same pressure, because it is at higher pressure with the tank full, that there is a bigger drop in temperature to bring it to the same temperature. The cold NG cools the air allowing a more dense air fuel mixture to enter the cylinder.

When the tank is nearly empty, the change in pressure is much less the charge will not be as dense.

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#35
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Re: Any thoughts about installing CNG on a light piston aircraft engine?

03/04/2013 9:19 PM

Do you feel this will be the case given the regulators are heated?

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#36
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Re: Any thoughts about installing CNG on a light piston aircraft engine?

03/04/2013 9:33 PM

My suggestion was conjecture, I couldn't think of another reason why a pressure regulated system would have a performance decline near the end of the tank.

Depending on how the heaters on the regulator are controlled, the effect could be the same.

Assuming the heaters keep the gas leaving at a constant temps, it seems like it would make performance consistent.... i.e. giving up any benefit available at cooler temps.

.

Seems like keeping a more dense charge would be desirable.

.

Are the regulators heated because there is concern about the exterior icing over? Or is there actually danger of CGN getting cold enough to freeze? It has to be the first, right?

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#38
In reply to #36

Re: Any thoughts about installing CNG on a light piston aircraft engine?

03/04/2013 9:51 PM

From what I can see, all regulators in automotive systems are heated by the coolant systems. Coolant being routed through the regulators to avoid ice forming as a result of the pressure change that takes place in the regulator: "As gas flows by this valve it rapidly expands and cools. This phenomenon, the Joule Thomson expansion effect, can cause dramatic gas temperature drops. For example, if the gas enters the regulator at room temperature / 3000 psig and exits the regulator at 100 psig, the gas will cool to about -70° F." We need to explore this further but suffice it to say, automotive systems all seem to use "coolant" routed through the regulator for this purpose.

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#39
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Re: Any thoughts about installing CNG on a light piston aircraft engine?

03/04/2013 10:05 PM

Contact Jim Younkin at younkincng.com He is a big time independent conversion specialist in Utah. He might have some knowledge about this. He is a free spirit,and is open to new ideas. You might also benefit from cngchat.com.

For general natural gas stories worldwide see my blog at ronwagnersrants.blogspot.com

My best story on aviation is about Boeings Sugar Freeze jet airliner plan. The Russians have also experimented with natural gas airplanes and helicopters. I have stories on that also. Here is the Boeing link:http://www.aviationweek.com/Blogs.aspx?plckBlogId=Blog:a68cb417-3364-4fbf-a9dd-4feda680ec9c&plckPostId=Blog%3Aa68cb417-3364-4fbf-a9dd-4feda680ec9cPost%3A00f49124-7f6b-4fec-9bdb-fae7095ba3b1

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#46
In reply to #38

Re: Any thoughts about installing CNG on a light piston aircraft engine?

03/05/2013 12:11 AM

Which raises a design issue as most small aircraft engines are air-cooled. You may be able to run the engine exhaust thru a heat exchanger but I don't think there are any suitable systems available commercially. The exhaust temperatures are much higher than the coolant temperatures in liquid-cooled IC engines.

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#47
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Re: Any thoughts about installing CNG on a light piston aircraft engine?

03/05/2013 12:23 AM

I have a simple idea for that.

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#3

Re: Any thoughts about installing CNG on a light piston aircraft engine?

03/04/2013 3:31 AM

The vehicle's insurers may have a view. Make the call.

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#9
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Re: Any thoughts about installing CNG on a light piston aircraft engine?

03/04/2013 12:39 PM

There are tens of thousands of "Experimental - Amateur-built" aircraft on the FAA registry, most are insured. There are other experimental aircraft used by manufacturers and aircraft are regularly placed into, and out of, the category for just such purposes.

If the conversion were successful application would have to be made to the FAA for the system to be approved and made available for new or existing aircraft. Once that is done insurance rates should approach "typical" -- which is still high.

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#4

Re: Any thoughts about installing CNG on a light piston aircraft engine?

03/04/2013 5:16 AM

Why would anybody in their right mind degrade the performance and range of their aircraft????

Is this type conversion certified by the FAA?

Why would anybody in their right mind degrade the performance and range of their aircraft????

How many FBO's are equipped to dispense CNG?

Why would anybody in their right mind degrade the performance and range of their aircraft????

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#11
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Re: Any thoughts about installing CNG on a light piston aircraft engine?

03/04/2013 1:05 PM

1. This is a Test and only a Test. The performance issues remain to be seen and the arguments still rage on the performance issue. Can an aircraft accept a 10% reduction in power - generally yes as most light aircraft seldom cruise at more than 75% power (and usually less). Takeoff or emergencies are when you want as much power as you can get. Even then it depends on the engine and many otherwise identical aircraft are offered with a choice of engine sizes.

2. FAA approval would be an option if it worked.

3. I doubt if any FBOs are currently equipped to dispense CNG.

4. There is a huge move afoot in the FAA to eliminate 100LL AvGas. This is because they are concerned about lead emissions [DON'T get me started]. This is one possible solution. In addition this morning at the St. Paul general aviation airport the cheapest AvGas was $6.75 per gallon, if the GGE price is $1.00 you can see the incentive even IF there is a slight reduction in performance. In addition, flight schools would benefit significantly for training aircraft which stay in the general vicinity of the home airport.

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#5

Re: Any Thoughts About Installing CNG On a Light Piston Aircraft Engine?

03/04/2013 9:13 AM

In short BOONDOGGLE!!! Same goes for hydrogen as a fuel for anything but rocket.

The only application I've seen MAYBE usable is for municipal bus, that has a known support crew to support 4500psi refueling and systems to compress and store. As well there's large areas under the floor for long high pressure tanks. But I would hate to have to pay the extra property tax to support this.

There have been companies that have come and gone making fueling stations, the hard part is metering over a large flow rate and velocity that includes super sonic.

Have you computed the volume needed for a 4 hour flight? How many pressure cycles before you will replace the pressure tank? The cost to certify? The cost to support once fielded with service bulletins, warranty to correct initial design errors. Law suites for wrongful death after a hard crash and fire ball, as well quick connect hose that fires off like a bullet from operator error, design error, maintenance error.

It's real hard to get past liquid hydrocarbons from an energy volume view, as well safety. Your competing with av gas at ~$5-$6/gallon. You don't hear of fire balls too often from refueling.

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#12
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Re: Any Thoughts About Installing CNG On a Light Piston Aircraft Engine?

03/04/2013 1:46 PM

According to a NASA study of single engine propeller operations: "88 percent of personal operations flights last less than 1.5 hr, and 75 percent less than 1 hr. The percentage of shorter flight durations was even higher for instructional airplanes, where 97 percent of the flights lasted less than 1.5 hr, and 86 percent less than 1 hr.

The average flight durations for airplanes in the two types of operations varied from 25 min to 1 hr 27 min for personal operations and from 19 min to 53 min for instructional operations."

Fatigue cycles to failure on Standard Resin Vessels are said to be roughly between 5,800 and 7,000 cycles. The new 3M Resin based vessels are between 9,500 and 11,000.

As mentioned above, I believe that given the increase cost of AvGas vs. the CNG/GGE (around 575% @ $1 vs. $6.75) the opportunity should be explored. In the case of training this would lower the out-of-pocket fuel cost per hour by 85%. Today, one of the greatest barriers to flight training is the cost-per-hour of flight time. Assume the typical training aircraft uses 10 gallons per hour; CNG could save the students $55-$60 per hour.

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#15
In reply to #12

Re: Any Thoughts About Installing CNG On a Light Piston Aircraft Engine?

03/04/2013 2:49 PM

If you think this to be a good idea, then make your aircraft experimental, modify it, flight test it, get the FAA to approve it, and then you can sell your STC, and then proceed to the next airframe type, and do this again. Or you can design a brand new AC and see about certifying it.

If all goes well you can make money. But all it's going to take is one accident with a catastrophic outcome. If you can prove that there will be less then one failure in one billion hours (10e-9 failures per hour) that results in a fatality, and have the FAA believe your analysis, then your good to go.

As for your numbers of very short flight hour operations, those are joy rides, or pilots trying to stay current. The pilots I know fly from Iowa to Florida, and Nebraska to Texas. With a Mooney at 150-160knots, your looking at 3-5 hour flight. sure if you want to fly a low speed Cessna 17x/18x and do barn storming or flyins, you have these short flights, you really don't want to do 2 or more landings for fuel. I also may have a incorrect belief, base on hanging with my pilot buddies.

I quit flying after 55 hours, didn't want to kill myself, and too expensive to rent, and owning even more.

I spent the last 30 years working on autopilots/FMS systems for bizjets, turbo props, and 100 seat and smaller regional's. Single engine private pilot stuff was way off our low end. It used to be easy to certify, now the FAA and EASA have turned into social welfare job organizations, and want to micro manage all aspects of aircraft/avionics design regulatory compliance. They spend all their time looking for typos in your documentation to prove their needed employment. Have fun trying to get this fuel change, especially now after Boeings boof of the Li-ion battery.

At any rate, it's a boondoggle, if it were practical, automobiles would have this already. If you think not, go and get something certified.

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#16
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Re: Any Thoughts About Installing CNG On a Light Piston Aircraft Engine?

03/04/2013 3:15 PM

Automobiles already do have it, and have since WWI. Many designs all over the world from the likes of Mercedes, Volkswagen, Fiat, GM, Ford, Dodge etc. In America the Big Three all offer pickup trucks with bifuel CNG/gasoline models. It is the future of vehicle fueling. See cngprices.com .

Heavy duty trucks stand to save the most money, and are catching on fast. Especially popular are waste management trucks, concrete trucks, local delivery trucks etc. Long haul class eight trucks, that are parts of fleets, are also becoming very popular.

Buses and taxis are mandated to use CNG in China. America is way behind in using CNG vehicles. Yet we have the lowest price natural gas outside of the Middle East.

I have 5,200 plus natural gas stories at ronwagnersrants.blogspot.com

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#17
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Re: Any Thoughts About Installing CNG On a Light Piston Aircraft Engine?

03/04/2013 4:17 PM

I'm not aware of any of the USA manufactures that have factory delivered CNG vehicles. I just googled this and not a single hit of any manufacture, but lots of after market conversion kits. The big 3 do offer Flex fuel, but that's another boondoggle that I have to subsidize to enable. I've not seen any local gasoline stations that have CNG available anywhere within 140 miles of me Grimes Iowa (the only place in Iowa with CNG) is a city near Des Moines).

As I said before, there are municipal bus conversions that have CNG. I know there are cities that have this, only the capital cite of Des Moines has this in Iowa.

And yes it might be the next big thing to happen with all the fracking going on through out the north american continent. That too comes with a cost of ground water contamination, and earthquakes.

What's more frustrating is the failure to have high MPG vehicles that once were available.

So let's see how long it takes for the big 3 to sell an off the shelf CNG vehicle. Then maybe we can see this become a single engine aircraft possibility. But the cost of private pilot flying is very quickly only going to be for the very wealthy.

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#20
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Re: Any Thoughts About Installing CNG On a Light Piston Aircraft Engine?

03/04/2013 5:41 PM

Honda sells the CNG Civic from dealers in 36 states. Dodge sells the Ram truck dual fuel from their dealers, it is made right on their line. 2500 series only. You can order Ford F-250s directly from the dealer. Look at cngprices.com for a map of stations with prices.

I live in a CNG desert too, and am working to change that. It may never benefit me personally, but I am working so that it will, and millions of others.

It is sad that you think fracking creates "eartquakes" or pollutes water. You have been taken in by the green extremists. You need to look up the earthquake scale. If you consider a subwoofer in front of your house for a minute, that would be the extent of the earthquake.

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#23
In reply to #15

Re: Any Thoughts About Installing CNG On a Light Piston Aircraft Engine?

03/04/2013 6:03 PM

IGNATOR RE: your #15 comment

Thanks, and I agree with much of what you say. I would like to clarify that I have no plans to profit financially from this effort. As for the number of hours in a typical flight, those noted numbers are scientifically derived and consistent with other studies. Most GA light piston flights simply are not long cross countries. While I don't want to over emphasize it, part of the issue with the declining pilot population is the cost of learning how to fly to begin with. Being able to significantly reduce the fuel cost in training would be a great help.

What I did no mention is that I am proposing a dual-fuel experiment where perhaps 30-50% of the total envisioned fuel weight can be dedicated regular AvGas.

There is no question that our automobile system has evolved using gasoline. That opens up another debate I don't want to pursue here. But I will say one thing: While I don't have a line plumbed into my hangar carrying gasoline - I do have one carrying natural gas.

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#26
In reply to #23

Re: Any Thoughts About Installing CNG On a Light Piston Aircraft Engine?

03/04/2013 6:29 PM

Now I'm getting ready to sheptical.

You can't possibly be suggesting a duel fuel aircraft????

You've just spent at least $30,000.00 to degrade the performance and range (And until we know for sure the safety and reliability) of a perfectly good airplane. Why?

You've also got electricity plumbed into that hanger. And you will still need a compressor to use your little pipeline to fill your CNG tanks.

You might be able to make a financial case for some general aviation airports like we have here in AZ.

Good luck.

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#37
In reply to #26

Re: Any Thoughts About Installing CNG On a Light Piston Aircraft Engine?

03/04/2013 9:42 PM

Oh yes I am! :)

"We cannot solve a problem by using the same kind of thinking we used when we created them."....Albert Einstein.

It's not near even $10k to install even for the single test ship. The performance issue is not at all resolved and will not be until tested. What would happen if we were all worried about leaving the house in the morning? Yes we also have electricity in the hangar. If this works we will have a System to implement it. BTW I own an airport in Arizona :). Love it there!

Ps.. Sorry the formatting does not work easily on an iPad.

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#13

Re: Any Thoughts About Installing CNG On a Light Piston Aircraft Engine?

03/04/2013 2:18 PM

You need to consider the list of priorities that are assigned to aviation. The number one consideration is safety for private and commercial aircraft and probably mission success for military aircraft.

Fuel economy takes a back seat to safety by a wide margin. If CNG does not offer equivalent safety performance to existing AV gas, there is little reason to consider it.

As others have pointed out, you can also expert a significant performance drop compared to AV gas, which is higher performance than pump gas for automobiles. The performance gap will also represent a decreased safety factor under adverse flight conditions.

Lastly, any economy gains achieved from CNG are not going to be seen as significant in the larger picture of private aircraft. Current fuel costs represent a very small fraction of the total operational and ownership costs. If you are at the point where the price of AV gas is cramping your aviation lifestyle you may better off considering sailplanes.

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#21
In reply to #13

Re: Any Thoughts About Installing CNG On a Light Piston Aircraft Engine?

03/04/2013 5:43 PM

Safety is always important. There is no reason to believe CNG would compromise safety. There As well, there is no real consensus on the question of performance (see: http://cr4.globalspec.com/thread/77987). FYI, many light piston aircraft are currently approved for operation using autogas.

As for required h.p., aircraft are frequently sold with various engine [power] options. As long as it is demonstrated that the power output of a given combination is sufficient, pilots are trained to operate within those parameters.

I beg to differ on most pilot's preference to pay 500%+ more than they need to for fuel. The industry abounds with statistics showing a decrease in GA activity attributed to increased fuel costs. . In any event, as perhaps I should have clarified my initial post: I am most interested in hearing more technical comments and possible CNG related engineering issues, not debating the wisdom of the pursuit.

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#24
In reply to #21

Re: Any Thoughts About Installing CNG On a Light Piston Aircraft Engine?

03/04/2013 6:16 PM

I think turbocharging is going to be imperative.

You are adding the weight of an additional small adult to the plane with the tanks, correct? (i wonder if there are any reasonable composite tanks)

That coupled with roughly a 12% decrease in power is really starting off on the wrong foot. Without turbocharging, the problem will quickly get worse with altitude.

.

Gaseous fuels take up about 12 more volume than liquid fuels finely dispersed. Using a turbo will help to make up for that displaced air, and will lessen any effects of altitude.

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#32
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Re: Any Thoughts About Installing CNG On a Light Piston Aircraft Engine?

03/04/2013 9:04 PM

I agree that some form of intake manifold boosting (turbo or super charging)will likely be mandatory. Remember that with increased altitude comes less ambient air to burn fuel. I do not like the general idea of taking a gasoline engine that has been optimized to convert a liquid fuel into mechanical energy and just blowing in a gaseous fuel into the intake air-stream. Some theoretical and experimental optimization work should be performed before somebody tries to fly with this. Fuel/air ratios, compression factor, stroke length, valve and ignition timing may need to be altered to get as much chemical energy into mechanical energy.

Now that I've listed a wide group of concerns, I see nothing wrong with the concept. I see a lot of work needed for proper execution.

You might consider starting with small RC plane engines. This will probably give you the worst scale conversion for your fuel mass to performance to deal with. However, conquering this problem in a small scale with the immediate safety advantages of starting small may just be the right place to start.

Good Luck.

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#42
In reply to #32

Re: Any Thoughts About Installing CNG On a Light Piston Aircraft Engine?

03/04/2013 10:28 PM

I like these suggestions however don't have time to mess around with the models. We can prove it works or push a button and fly on with the AvGas we have on board!

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#40
In reply to #24

Re: Any Thoughts About Installing CNG On a Light Piston Aircraft Engine?

03/04/2013 10:09 PM

Yes, we are definitely thinking of turbocharging. That would be easy and good to test. The 3M tanks are very promising. We have considered the pilot weight and it looks good. People seem to be getting carried away with the power thing. I have an Aeronca C3 with a two cylinder engine of 36 h.p. that can carry two people, its not magic and its not the Space Shuttle. I have aircraft I would never take off with full power unless I was at 12,000 ft!

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#25
In reply to #21

Re: Any Thoughts About Installing CNG On a Light Piston Aircraft Engine?

03/04/2013 6:18 PM

You use this?????http://cr4.globalspec.com/thread/77987 as a reason for accepting the "no real consensus" argument???????

Those bozos don't ever agree on anything.

Here's why I'd not quit my day job:Battery powered plane gets a test flight - Elektra One - D-MELN ...

Soon, we'll have more frackin natural gas than we know what to do with so, maybe it'll be cheap enough to compete with batteries.

While I think it's totally dooable, I see no reason to do it. Don't forget the infra- structure needed. Airports already have electricity by the buckets full.

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#27
In reply to #25

Re: Any Thoughts About Installing CNG On a Light Piston Aircraft Engine?

03/04/2013 6:49 PM

Lyn:

'Why don't you knock it off with them negative waves? Why don't you dig how beautiful the possibilities are? Why don't you say something righteous and hopeful for a change? '

At the very least his ideas are worth of further research.

I seriously double electric airplanes are taking over any time soon. Batteries are heavy....and even when they can roll on the ground, they haven't taken over yet.....

...Just curious, Lyn, do you drive a Prius?

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#28
In reply to #27

Re: Any Thoughts About Installing CNG On a Light Piston Aircraft Engine?

03/04/2013 7:06 PM

Oh my!

Try as I might, to be like Oddball, I find that Moriarty is more my style.

Expect the worst and never be disappointed, I say.

The fact that I have no positive vibes here will not stop the progress of this discussion.

I just don't see what good will come of it.

Manned, battery powered planes are already flying.

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#29
In reply to #28

Re: Any Thoughts About Installing CNG On a Light Piston Aircraft Engine?

03/04/2013 7:11 PM

So then, are we to understand you do drive a Prius?

.

.

wait....or would that be too close to a dual fuel vehicle? Have you switched to a completely electric vehicle? If it makes sense for planes, even with the weight penalty, it MUST make sense for rolling around in your car, right?

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#31
In reply to #29

Re: Any Thoughts About Installing CNG On a Light Piston Aircraft Engine?

03/04/2013 7:17 PM

Sorry to disappoint.

My wife drives a Chevy V-8 van, or a V-8 Corvette and I drive a V-8 Ford 4 door pickup.

Got rid of the boat, couldn't afford the gas.

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#72
In reply to #31

Re: Any Thoughts About Installing CNG On a Light Piston Aircraft Engine?

03/06/2013 11:34 AM

Presumably the place you park your vehicles has plenty of access to cheap electricity....

....

but somehow the allure of electric automobiles (which can much more easily support the additional weight burden of going electric, compared to a plane) has not seduced you into foregoing that ICE nonsense?

.

Obviously ICE automobiles are dooable, but you have electricity available by the buckets full.

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#41
In reply to #25

Re: Any Thoughts About Installing CNG On a Light Piston Aircraft Engine?

03/04/2013 10:25 PM

I love the idea of battery powered flight. And in fact, I am on the Board of Directors of the Lindbergh Foundation which awards battery powered airplane efforts. In my humble opinion battery powered airplanes are not presently as good an answer as CNG aircraft may be. We must get off this single solution mantra in the U.S... Electricity is a great idea to explore but when you talk to the Greenies who suggest electricity is the answer... and it should ALL come from wind and solar... You start to wonder. If you give me 50 nuclear power plants, I promise to drop this and start buying batteries.

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#43
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Re: Any Thoughts About Installing CNG On a Light Piston Aircraft Engine?

03/04/2013 10:34 PM

I defer to you. Carry on.

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#58
In reply to #41

Re: Any Thoughts About Installing CNG On a Light Piston Aircraft Engine?

03/05/2013 12:14 PM

You can make greenies happy with biogas. It is carbon neutral and can be used just as any natural gas. This is going to be a big deal in California. They just funded a big biogas facility for Sacramento. They are trucking in biowaste from Bay Area restaurants. Biogas has that environmental cachet, and is very popular in Europe. Audi has even gone one step farther: http://green.autoblog.com/2012/12/22/audi-building-e-gas-plant-to-make-climate-friendly-vehicle-fuel/

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#56
In reply to #21

Re: Any Thoughts About Installing CNG On a Light Piston Aircraft Engine?

03/05/2013 11:30 AM

"There is no reason to believe CNG would compromise safety."

Until you actually try to prove that to the FAA I would not be so quick to make that statement.

My area of expertise is avionics design and my experience in that field has quickly taught me that the hoops you must go though to demonstrate acceptance are not trivial.

Like I said, if you can't afford the price of admission for private aircraft you really do not belong in that hobby. Sadly, I can't even afford to go racing at the track, let alone owning and operating (or even just the maintenance of) a small aircraft, even though I love to fly.

From a purely academic point I can understand the value of your question.

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#45

Re: Any Thoughts About Installing CNG On a Light Piston Aircraft Engine?

03/04/2013 11:03 PM

Gentlemen if my memory doesn't deceive me I believe that Roush racing was experimenting with CNG or propane for drag racing and doing pretty well with it as an alternative fuel. As I remember they overcame the horsepower loss with some optimization of the engine components just can't remember what it was they did at the time. I was intrigued at the time enough to check with a few friends that were using propane or CNG for their racing efforts One thing I remember was they raised the compression ratio considerably,and did an extensive porting work for flow in the heads. Their main goal at the time was to gain efficiency and less maintenance for the long haul of the season. All of them at the time were extremely happy with their gains.

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#53
In reply to #45

Re: Any Thoughts About Installing CNG On a Light Piston Aircraft Engine?

03/05/2013 11:05 AM

Actually Roush owns a company that converts vehicles to burn CNG (see: www.roushcleantech.com). The last I heard they were backed up for months. It's a huge business for them.

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#62
In reply to #45

Re: Any Thoughts About Installing CNG On a Light Piston Aircraft Engine?

03/05/2013 1:39 PM

I have built a few propane based dual fuel and a single fuel propane only vehicle engines before that have seen regular to daily use for years now and I can confidently say that getting performance with fuel efficiency out of propane and CNG is rather easy.

Here's one. http://cr4.globalspec.com/thread/59332

Propane and CNG will tolerate mid teens compression ratios with ease where gasoline cant go much over 9:1 ratios without issues plus given their quicker smoother burn characteristics they will also run very well on what would be considered mildly to moderately aggressive cam shaft profiles and timing settings for gasoline fuel.

For performance engine applications those are the two primary ingredients to making power and fuel energy to mechanical energy conversion efficiency.

Although both fuels have less energy per volume than gasoline their different burn characteristics more than make up for that by being capable of considerably higher fuel energy to mechanical energy conversion values when the engine is designed specifically to favor those fuels.

One of the easiest to measure points of proof for that is the substantially cooler exhaust gas temps when compared to gasoline. One of my dual fuel vehicles is my 99 Ford F250 SD four door 4WD which when running on propane has the same fuel mileage and power as it does when running on gas but the ECM always logs in two error codes for the O2 senors. Too lean and too cold at proper engine operating temp.

Basically that means that more of the thermal energy given off during combustion is being converted into mechanical energy rather than being dumped out the exhaust! Even though the fuel has less energy per gallon its energy conversion ratios are far better and make up for the difference!

On top of that neither fuel requires any emission devices or special emissions compliance tuning either which in many modern engines represents a serious crippling effect on performance and fuel efficiency from what they could get to what they do get in normal working conditions for gasoline fuel.

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#63
In reply to #62

Re: Any Thoughts About Installing CNG On a Light Piston Aircraft Engine?

03/05/2013 2:07 PM

"Propane and CNG will tolerate mid teens compression ratios ..." "... mildly to moderately aggressive cam shaft profiles and timing settings for gasoline fuel." "... considerably higher fuel energy to mechanical energy conversion values when the engine is designed specifically to favor those fuels."

While I don't doubt that these statements are true, they don't fit well with my interpretation of, "... installing a conversion kit on an air cooled aircraft engine such as the IO-360 of 180 to 200 h.p." Virtually all common aircraft engines are low compression even compared to modern auto engines. Moreover, the emissions devices are required for road-going vehicles, at least in the US, but generally not a factor for aircraft. ("... neither fuel requires any emission devices ...")

I will make this "Off-Topic", since both the issues raised, and the reasons I'm raising them, seem to be OT to me.

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#65
In reply to #63

Re: Any Thoughts About Installing CNG On a Light Piston Aircraft Engine?

03/05/2013 2:42 PM

Ron: FYI; The aircraft engine contemplated is a fuel injected, four cylinder with an off the shelf compression ratio of 8.7:1.

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#66
In reply to #65

Re: Any Thoughts About Installing CNG On a Light Piston Aircraft Engine?

03/05/2013 4:05 PM

Pretty much what I figured. For comparison, I'm driving a 16-year-old dead stock econobox running more than 10:1 on the cheapest Regular gasoline. I read a couple of weeks ago that there are now TWO CNG stations open to the public in my state - though the local sheriff's department has run its squads on CNG for at least 15 years, and I know of taxi fleets, etc., doing the same. Sadly, if more outlets are provided, I'll bet money that the state will impose road-use taxes on CNG just as they do for gasoline, cutting the cost advantage. There ARE programs to get road tax money back if fuel is used for construction or agricultural equipment (off-road), but it's far too easy to "forget" to provide that option for any new source of revenue. The home machines to compress natural gas for fueling might be the answer for that.

Certainly, the CR could be increased with special pistons, longer rods, new heads, etc., and a new cam could be made for an IO-360 or comparable - but the cost would be high.

A much cheaper approach might be to look at something like an VW conversion engine (and, remember, some road-going versions had EFI right from the factory.) Check out http://www.eaa.org/experimenter/articles/2010-02_powerplants.asp and other sources. No, that won't work for a Cessna 172 - but there are complete airplanes out there designed to use the VW (Sonex, e.g.) that you can probably buy complete and ready to fly for the cost of a good IO-360. Lessons learned on the cheap airplane & engine should transfer fairly directly to the larger ones - just a suggestion. Test-stand work could even be done on junkyard or E-Bay used engines that you'd never consider flying [I'm a great believer in the Scotch-tape-&-baling-wire approach to testing concepts, in case you haven't already figured that out!]. "VW's are Lego", it is sometimes said, meaning that an enormous variety of aftermarket parts and services make it possible to mix-&-match to build up nearly anything you can imagine.

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#67
In reply to #63

Re: Any Thoughts About Installing CNG On a Light Piston Aircraft Engine?

03/05/2013 6:49 PM

The point I was trying to make is that CNG or propane are not weak fuels by any means however regardless of what the application of the IC engine is to get proper power and fuel efficiency from one it has to be set up properly mechanically to match the characteristics of the fuel.

Automotive, aircraft, industrial, lawn and garden it doesn't matter that much. If the engine is not designed to run on a specific fuel it always going to have limits and impracticalities associated with using a fuel it wasn't set up for.

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#68
In reply to #67

Re: Any Thoughts About Installing CNG On a Light Piston Aircraft Engine?

03/05/2013 11:41 PM

Yes. Good things to explore. I wonder if the manfacturers would be willing to do that?

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#69
In reply to #62

Re: Any Thoughts About Installing CNG On a Light Piston Aircraft Engine?

03/06/2013 9:43 AM

'....Basically that means that more of the thermal energy given off during combustion is being converted into mechanical energy rather than being dumped out the exhaust! Even though the fuel has less energy per gallon its energy conversion ratios are far better and make up for the difference!....'

.

That portion is not up to your usual standard. What you have proposed could possibly be the reason for the noted difference, but there are other explanations that are very likely. That was a pretty broad jump to an unsupported conclusion. Not typical for you.

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#70
In reply to #69

Re: Any Thoughts About Installing CNG On a Light Piston Aircraft Engine?

03/06/2013 10:13 AM

Really. That seems like a spot on analysis to me. Most of the thermal waste energy in any ICE goes out the exhaust port. On each ignition cycle the hot gasses do not linger long enough in the combustion chamber to transfer heat to the engine block. The one very reasonable assumption tcmtech implied but did not state is that the CNG goes through a complete combustion in the process and thus converted all of the available chemical energy in the process.

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#71
In reply to #70

Re: Any Thoughts About Installing CNG On a Light Piston Aircraft Engine?

03/06/2013 11:12 AM

As entertaining as the 'It has been undeniably proven because our supporting argument only used reasonable assumptions' club must be, I have to decline to membership.

.

As I stated, what he proposed reasonably might be part or most of the cause. I wasn't dinging him for the assumptions, only the statement as fact of the (incomplete) analysis.

.

I'm a bit surprised some of the other reasons haven't occurred to you. Here are two to get you started:

.

- Cold NG introduced cools things down a bit. CNG even with a heater on the regulator typically is introduced at a much cooler temp than a liquid fuel due to the NG expansion. Starting at a lower temperature if all other things were equal would naturally lead to resulting in a lower temperature.

.

- Smaller effective displacement.. Gaseous fuels take up about 12% more volume in the cylinder pre combustion than finely dispersed liquid fuels. This means at similar RPM and throttle input, CNG will be adding less heat and delivering less power ....so it isn't necessarily an efficiency thing. At idle the effect is probably larger since there is no load, the CNG system being effectively a smaller displacement, can probably save some fuel...that is an efficiency thing but not really the way it is most often discussed.

.

I bet you can think of another reason for the observed phenomena... go ahead.

.

Also while you are thinking about it, perhaps you could go into how it is that unburnt fuel leaving the tailpipe due to incomplete combustion would add heat to the engine as your comment suggests.

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#73
In reply to #71

Re: Any Thoughts About Installing CNG On a Light Piston Aircraft Engine?

03/06/2013 12:14 PM

I am not sure why you feel the need to nit pick my comments and observations but, Okay.

In the all mechanical type vapor fuel systems like I use the actual fuel vapors are being fed into the intake manifold system ahead of the throttle butterfly valve by means of a slight vacuum created in the vapor mixer unit by simple venturi effects.

That vacuum signal is what pulls the fuel vapor out of the vaporizer unit which BTW will not feed any fuel vapor out if there is no vacuum signal present and the primer bleed valve is turned off. That fuel vapor is heated to the same operating temp as the engine by coolant circulating through the vaporizer unit so it is by no means cold.

Now regarding that vacuum signal it's very low and the closest reference I can come up with is it's about equal to what our lungs produce when we breath in. Its also how I test new or rebuilt vaporizer units before installing them. I connect it to a 100 PSI clean air source and try taking a fast deep breath from the vapor output port. With the primer bleed valve turned of there should be no output but I should be able to take a deep breath and get full flow. If it cant keep up with that simple test it needs the main diaphragm counter balance pressure adjusted.

For CNG systems they use a first stage high pressure (5000 PSI or less) to medium pressure (50 - 150 PSI) regulator ahead of the vaporizer unit that is also heated by engine coolant as well. What all of this means is that the fuel vapors are entering the intake air stream at nearly the same temp as the engine and not cooler than the air being drawn in.

The thing is I don't consider any of my explanations to be loosely based theory. They are all based on well known and understood principals that are common knowledge in the propane and CNG fueled equipment industry.

Personally I have been working with and using these types of systems for around 12 years now and have lots of different systems on hand both new and used from numerous manufacturers for both propane and CNG that fit engines from as small as a 3 HP 1 cylinder push mower type engines up to my 400+ HP 460 CI V8 Ford and my 6.8l V10 Ford engines and every size in between.

They all use the same basic operating principles and show similar physical engine operating characteristics such as the exhaust gas temps being cooler than than their gasoline burning counterparts when set up properly.

Sorry but there is no new science here.

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#74
In reply to #73

Re: Any Thoughts About Installing CNG On a Light Piston Aircraft Engine?

03/06/2013 3:00 PM

Not not nit picking. I respect your knowledge of diesel and CGN. I simply thought you had missed something, not that you said anything incorrect. People do make mistakes.

This time it wasn't you, it was me. I have zero knowledge of a CNG conversion in practice, and my flawed assumption was that there was heating of the regulator to keep it from freezing, but that the advantage of being able to cool down the intake would still be a benefit.

.

So I am curious, and this is not some sort of leading question, or trying for an 'aha gotcha': Why is the NG warmed to coolant temp?

.

.

On the other side of this doesn't warming the NG mean it takes up even more volume, displacing air and therefor oxygen available to react?

Am I missing something, or doesn't that limit on the O2 in the cylinder at any time, mean that running diesel the engine can (and often would) be adding more heat per combustion cycle? Wouldn't that in itself equate higher EGTs, but not necessarily mean CNG is more efficient since there is also less power?

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#75
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Re: Any Thoughts About Installing CNG On a Light Piston Aircraft Engine?

03/06/2013 3:54 PM

I suppose it really doesn't have to at engine temp when it leaves the regulators and vaporizer unit but being they are plumbed directly into the engines cooling system that's just what they operate at.

Mostly the heating is to prevent they diaphragms and moving needle valves in the system from getting too stiff or jamming up and to prevent ice from forming inside the regulators and vapor units where it could create large enough crystals to poke holes through the paper thin diaphragm on the final stage that works on the very fine vacuum signal.

When that has happens on my propane units they have had a tendency to start dumping raw liquid fuel into the intake which over fuels the engine until it stalls. After that the liquid propane starts building up in the intake and air filter system which poses a minor fire hazard potential similar to having a leaking gasoline fuel line on a hot engine until the vapor dissipates after a few minutes.

On my pickups the vapor feed line between the vaporizer and the mixer unit will be too hot to touch once the system warms up but once the fuel vapor is mixed with the outside air going into the intake everything levels off and is fine. Also given that NG and propane have fairly low specific heats in vapor form plus that they get mixed at A/F ratios between 15.5:1 and 17.5:1 the actual heat that the fuel vapor is introducing into the intake in not significant enough to affect the burn rates or overall engine efficiency.

This link gives a far basic explanation of how the vapor mixer and regulators work.

http://www.propanecarbs.com/home.html

This is the home page and they have loads of links to different info relating to CNG and LPG fuel systems and terminology.

http://www.propanecarbs.com/

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#76
In reply to #75

Re: Any Thoughts About Installing CNG On a Light Piston Aircraft Engine?

03/06/2013 4:40 PM

Hey TCMTech,

Thank you for the knowledge upgrade. I appreciate your explanation.

.

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#77
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Re: Any Thoughts About Installing CNG On a Light Piston Aircraft Engine?

03/06/2013 5:27 PM

Glad to help. However reading it and being able to actually implement it are two very different things.

What knowledge I do have of CNG and LPG systems was hard won. Lots of reading re reading and hands on testing and experimenting before I got it right (or at least close enough to work)!

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#78
In reply to #77

Re: Any Thoughts About Installing CNG On a Light Piston Aircraft Engine?

03/06/2013 7:31 PM

Just a question. I am no mechanic, and would not try to do a CNG installation. Don't you think that the new CNG kits are much easier to install than those you have worked with in the past?

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#79
In reply to #78

Re: Any Thoughts About Installing CNG On a Light Piston Aircraft Engine?

03/06/2013 9:16 PM

I don't know much about the new all electronic injection type systems but the newer mechanical ones are just as easy as the old ones.

Relating to putting a system on a newer fuel injected vehicle the actual install is even easier than the old systems that had carburetors on.

My 99 Ford F250 SD was about a 5 hour conversion to change it over to dual fuel. Electrically all that was needed was to tap into the fuel injector power wire and re route it to a SPDT switch under the dash so that it would either send power to the fuel injectors or turn on the electric solenoid for the propane system and bring a separate power line over to the idle air control unit being it originally got its 12 volt power off of the fuel injector 12 volt supply line.

The vaporizer unit sits on a bracket right above the engine and gets heated by being in line with the heater coolant circuit. The vapor mixer fits inline in the air duct between the throttle body and the air filter.

I would post some pictures of the pickup conversion tomorrow but my wife has the pickup and wont give it back. She put the gas in last so she thinks she gets to drive it until it's empty. That is the 75 gallons of propane in the tank I filled and paid for is empty. Not the 13 gallons of gasoline she paid for.

Maybe this weekend.

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#48

Re: Any Thoughts About Installing CNG On a Light Piston Aircraft Engine?

03/05/2013 3:12 AM

I saw the weight penalty portion of the discussion, and observe that it will be worse than described, since super- or turbocharging will add to the penalty (and it would make sense to start with a turbo'ed engine to begin with, since it will eliminate a LOT of effort).

But I don't see any mention of shape and volume of the tanks. Every GA (general aviation) aircraft I'm familiar with has a tank or tanks shaped and sized to fit within the structure, often between wing ribs, or sometimes ahead of the instrument panel. Some have what are called "wet wings", where portions of the skin & structure ARE the tank(s). This is efficient engineering, making components do double duty, and it puts the tanks very near the center of gravity. This is critically important, because as the tanks empty, the reduced weight could move the CG out of its limits, possibly making the aircraft unstable or even uncontrollable in pitch. "Efficiently shaped" CNG tanks will likely be cylinders with hemispherical end caps, and it could be necessary to use several small ones plumbed together to obtain sufficient capacity without redesigning and rebuilding the structure of the wing or fuselage. This will necessarily increase the weight penalty, and probably the amount of unusable fuel as well.

Yes, there HAVE been airplanes with cylindrical tanks - for some reason, I think that the Junkers Ju52/3m might have been one of them - but I can't see how it could be practical unless it's a fairly large aircraft and one with a thick (low-speed) wing. Perhaps you could carry a tank externally, like a WW II drop tank, with an aerodynamic fairing around it - but that adds yet more weight and drag.

At best, I'm skeptical that this would ever be practical. BTW, I'm a retired mechanical engineer, a long-time EAA (Experimental Aircraft Association) member, and have a homebuilt project of my own. I'm in an active "builder" chapter, and have seen the inner workings of quite a few homebuilt, and some restored commercial airplanes, as well as phantom drawings or other descriptions of many more. That's my basis for commentary on the volume & structure issues.

I would suggest posting your question at http://eaaforums.org/forumdisplay.php?5-Homebuilders-Corner, where you'll have an audience far more focused on this sort of work.

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#54
In reply to #48

Re: Any Thoughts About Installing CNG On a Light Piston Aircraft Engine?

03/05/2013 11:20 AM

Great points Ron. We need to remember that this is an EXPERIMENT, an X-plane, we are not designing a production airplane out of the box. My reason for posting here is to get as much practical input as possible in preparation for the testing. The issue of tank shape and CG considerations will of course be addressed; possible locations for the TEST plane are in the cabin, in a cargo pod type configuration or in the floats J. I like your idea of the EAA forum as well. I will post it there. Greg (EAA Lifetime 402961)

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#59
In reply to #54

Re: Any Thoughts About Installing CNG On a Light Piston Aircraft Engine?

03/05/2013 12:50 PM

Hadn't thought about floats - but that makes sense as a location, shape-wise, and size should work.

I deliberately addressed only the question of practicality; I don't see any reason that it can't be done, but wonder as to what will be gained by such a test. It's not like, say, the human-powered flight contests, where the winning device had no practical use, but could contribute to our knowledge of low-speed aerodynamics, efficiency through drag- and weight-reduction, structural design, etc. This seems to have a built-in dead-end, given that pressurized tanks will outweigh unpressurized ones for the foreseeable future, and that CNG has an energy-content penalty. If there were another compressed fuel gas which exceeded the energy-per-weight and energy-per-volume, lessons learned here would likely transfer - but then, why not start by testing with that fuel?

Given that avgas is already only available at a relatively small number of locations, and that there is no incentive for anyone to build up an infrastructure offering CNG at airports (or marinas, for float-equipped airplanes), I don't see where this can lead. Finding an alternative to leaded aviation gasoline (avgas) doesn't seem to be making a lot of headway, but is needed for a huge fleet of existing aircraft which cannot be readily modified to use CNG, nor to switch to different engines, even though leaded fuel may not be available at all in a fairly short time, rendering them useless.

The better availability of Diesel and various jet/turbine fuels at airports worldwide has justified building aircraft engines which will run on any of them, using a Diesel cycle. For example, see http://www.deltahawkengines.com/. Other than satisfying personal curiosity (yes, a VERY legitimate reason to build an Experimental airplane!], I'm not seeing why you are pursuing this concept. I look forward to seeing your reasoning - THANKS!

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#60
In reply to #59

Re: Any Thoughts About Installing CNG On a Light Piston Aircraft Engine?

03/05/2013 1:17 PM

I can't think of better reasons than far lower fuel cost, and far cleaner emissions, less noise, and less engine wear.

If you favor diesel, a dual fuel diesel engine can run on any combination of diesel and CNG or LNG.

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#64
In reply to #59

Re: Any Thoughts About Installing CNG On a Light Piston Aircraft Engine?

03/05/2013 2:34 PM

Rosanoff: "Mr. Edison, please tell me what laboratory rules you want me to observe."

Edison: "There ain't no rules around here. We're trying to accomplish somep'n!"

- Thomas Edison

Thanks again Ron. Perhaps I should have posted the question on an inventor's site rather than an engineer's. I have continuously said here that the jury is still out on the performance issues - and the extent to which it really matters. As a pilot you know that if the performance is adequate it can be flown. The point is to explore our options knowing that progress can be made with promising discoveries.

So, on the power question, let's take the most successful mass-produced airplane in the history of the world: The Cessna 172. The airframe of this ship has remained essentially unchanged since it was introduced in 1956. There have been tweaks but the Max Gross Weight has remained between 2,200 lbs. and 2,400 lbs. for more than 50 years. In 1956 the 172 was powered by an 145 h.p. engine then 160 h.p. In 1963 that went up to 175 .hp. and later to 180 h.p. and finally in the 172XP up to 195 h.p.

Back to the future: In 2007 Cessna introduced a diesel powered C-172 (same airframe) using the Thielert diesel engine - of 155 h.p. - when Thielert ran into financial problems the project was put on hold with 100 aircraft on order. Then in 2010 Cessna announced that they were developing an electrically powered 172!

These Cessna 172 engine combinations range from 145 h.p. to 195 h.p., a difference of 29.4% on essentially the same airframe and all the while using the same modified NACA 2412 airfoil. These airplanes are flying every day all around the world on all of these various engines from 145 - 195 h.p.

I believe the power issue will not be a problem for this aircraft and I am glad to see you agree - so let's drop the energy-content argument for now until we have some real data. I firmly believe WILL be enough, certainly for our purposes. And it may also point the way for opportunities to improve performance whatever the baseline is.

As for the incentive portion of using this fuel, as I have said in earlier posts, it would be ideal for flight schools just for starters as CNG will be no more than quarter of the cost of Avgas… and not only flight schools but for many others.

The infrastructure is not a big deal. Right now there are appliances to fuel CNG cars right in your own garage. You can have the same think in your hangar. FBOs and flight schools would probably want something more robust which, in any event, would cost a small fraction of the investments in gasoline of diesel fuel tanks. They simply hook the fueling compressor system up to any natural gas line on the facility and go.

The configuration of tanks is clearly one factor but the world is a dynamic place and changes are taking plane today which are vastly improving things on the tank side. 3M for example: As stated above ten new 3M CNG tanks Type IV carbon fiber tanks offer up to "10% more capacity at up to 30% lower weight than conventional Type IV tanks of similar geometries." AGAIN: Type IV tanks are the latest and greatest and 3M has lowered the weight by 30% and increased the capacity by 10%. The world is not standing still.

Even without the 3M advances Quantum tanks are already within the realm of reason. Their #392L tank is 136 lbs with a GGE of 24.5. Add the weight of 24.5 of CNG GGE and you get 138 lbs. So the total weight of 274 lbs for the 24.5 GGE. The 100LL AvGas it "replaces" (avoiding the efficiency argument for the moment) weighs 147.5 lbs. for a net tank/fuel increase of about 126.5 lbs. At the moment this component appears acceptable for this experiment.

Once again the main thrust of this is to reduce costs, which CNG will do dramatically, while at the same time offering a much better environmental footprint that either gasoline of diesel fuel. We already understand the dynamics of gasoline and diesel but we clearly do not have a good grasp of the dynamics of CNG other that it clearly saves money and offers a cleaner solution.

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#57
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Re: Any Thoughts About Installing CNG On a Light Piston Aircraft Engine?

03/05/2013 11:32 AM

Right you are Ron..There are some "conversion " aircraft fitted with car engines but

the fuel burn would be higher with CNG not to mention the tank problem. As for aircraft engines, finding CNG at airports would be a real task and leaded CNG I have never seen. Did you notice the seaplane taking off at the kayaks?

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#49

Re: Any Thoughts About Installing CNG On a Light Piston Aircraft Engine?

03/05/2013 7:15 AM

I have read all of the posts and would like you to know that I have a solution to the heat source for the regulator on a normally aspirated engine using air for the cooling media.

The dimensions of the CNG tanks would have to be a concern as we normally place the Av Gas in the wings near the chord. Most of the tanks I have seen would not fit into a wing at the chord. They could be placed aft of the cabin as we put oxygen tanks there in the C-210s

Weight and balance would have to be a major factor in the placement of the tanks. Can it be done? I say Yes! Will it catch on? well remember all the problems we had when we wanted to go from a generator to the alternator. I was told by a 60 year old mechanic that the alternator would never work right. But, after time and improvements in how we rectified AC to DC every vehicle now has an alternator. (Remember the selenium rectifiers)

I am retired now and know that this project can work if you want to continue work on it. Yes I am a commercial pilot and have flow across the US several times in a 100 HP airplane. Flying 4 hours at a time between fuel stops. We do it and then we talk about it for years. Same with the changes to the systems we use in the airplane. I don't currently use celestial navigation but could it necessary. I now use GPS, easier but, years ago it wasn't available.

As for not being used now, wasn't many years ago that the only powerful engines were radial. Now we use jet engines????? When was the last time you flew on a commercial flight with radial engines?

Give it a try.

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#55
In reply to #49

Re: Any Thoughts About Installing CNG On a Light Piston Aircraft Engine?

03/05/2013 11:25 AM

Spot on! Thanks for the reply and confidence. No one yet has guessed what may be the best possible heat source for the regulator... I wonder if we are thinking of the same thing!

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#61
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Re: Any Thoughts About Installing CNG On a Light Piston Aircraft Engine?

03/05/2013 1:29 PM

I have thoughts I don't want to send to everyone on your project. email me and I will contact you directly.

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#50

Re: Any Thoughts About Installing CNG On a Light Piston Aircraft Engine?

03/05/2013 8:06 AM

Most GA aircraft require leaded fuel ie.100 LL, I know way behind times.

The new diesels burn jet fuel.

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#51
In reply to #50

Re: Any Thoughts About Installing CNG On a Light Piston Aircraft Engine?

03/05/2013 9:52 AM

Do I detect a little latent dyslexia?

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#52
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Re: Any Thoughts About Installing CNG On a Light Piston Aircraft Engine?

03/05/2013 10:00 AM

Yes Redferd, I think I have a little drain bamage this mourning..

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#81

Re: Any Thoughts About Installing CNG On a Light Piston Aircraft Engine?

03/08/2013 1:19 AM

What it comes down to in your desired application is that it is a commercial use. Meaning carrying people, freight, or services, for money. The government is going to have it's say on it one way or another, so you'd be well advised to look at far more than just the fuel characteristics and the conversion kit before putting yourself or another business owner on the hook for this, plus any possible consequences(FAA consequences=bad) or that might arise as a result for say, a given fire response training center that racks up tens of thousands of hours of flight time wants it for their small craft, but very well could experience unforeseen consequences due to variables specific to their field, or in performance issues versus altitude requirements, etc. The engineers on here ALL see some version of this at work when talking a new fuel for aircraft. Myself, I say that if you can get your requirements out of the fuel, and the difference in cost will pay for your conversion as well as pay for some unforeseen lowering of your efficiency estimates just due to lower fuel cost; then yeah, do it. Why not?

I take it that as of now at least, there is no ruling whatever on it's use as a fuel other than a minimum for a rated tank?

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#82
In reply to #81

Re: Any Thoughts About Installing CNG On a Light Piston Aircraft Engine?

03/11/2013 5:40 PM

Thanks. All the testing would be conducted within the FAA's rules. Any subsequent commercialization would also have the requisite approvals. There seems to be a general consensus to proceed. If we do so the first ship could be flying mid-summer. I will keep you posted.

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#83

Re: Any Thoughts About Installing CNG On a Light Piston Aircraft Engine?

04/05/2013 5:38 PM

Hopefully you have a long runway, because the power penalty and weight penalty will both bite you on takeoff!

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#84
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Re: Any Thoughts About Installing CNG On a Light Piston Aircraft Engine?

04/06/2013 2:14 PM

No weight penalty; well within the envelope. Plenty of power too!

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#85

Re: Any Thoughts About Installing CNG On a Light Piston Aircraft Engine?

12/03/2013 7:23 AM

It makes great sense to use CNG for automotive & large trucks cuz the weight is not a factor, but not so for aircraft. Maybe they would overcome some of that by using a higher pressure vessel so you could hold more cng tank .

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#86
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Re: Any Thoughts About Installing CNG On a Light Piston Aircraft Engine?

12/03/2013 1:36 PM

"The weight of storage tanks and associated plumbing is too great to provide practical utility in aviation....hmmm, what could be done about excess weight???? I know! Let's use tanks and associated plumbing rated to withstand greater pressure and hold more cng!!! Weight problem solved. Check, please."

.

I sometimes overhear conversations which seem equally liberated, but I am usually able to convince myself that what I overheard has more to do with my hearing than something expressed by someone else as a genuine. Now, what am I supposed to do when you write down something like the previous comment. I vision is fine.... what should I blame this on?

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#87

Re: Any Thoughts About Installing CNG On a Light Piston Aircraft Engine?

12/03/2013 5:28 PM

CNG tanks are getting lighter. Progress in actual use of graphene may help us out eventually. 3M is in the game, plus a lot of smaller companies. The other factor is that adsorption technology is being worked on by many large companies and universities. It would allow various shaped tanks and thinner walls. The adsorption material reduces the pressure exerted on the external wall.

Unfortunately I have no access to all of the progress that is being made in these areas. I would appreciate any tips on where to search for the latest information. Better and lighter tanks have an automatic market, if the price/value is there.

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#88

Re: Any Thoughts About Installing CNG On a Light Piston Aircraft Engine?

12/03/2013 5:35 PM
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