can a diesel engine be converted to natural gas?

CR4 is Conference Room 4.

Yes, possible. Practical, no. From Omnitek website:

In India is is mandatory for all taxis, three wheelers and buses to use Natural gas as fuel and thousands upon thousand vehicles are currently running on this system, both Gas engines and Diesels. The conversion is done locallyh in any city where the vehicles are and appears to be easy because not only 4000 but maybe 2 or 3 million vehicle are converted like this.

Thanks for the information. Do they use the same procedure as outlined here?

Right I am doing a project tryong to convert a diesel engine to work with treated biogas.

I just inject biogas in the air admission of the engine and limit the injection of diesel. Everything works fine and I can get the same power output for only 20% of the normal quantity of diesel injected.

The biogas I am injecteing is 60% methane and 40% CO2.

It is very easy to convert a gasoline fueled engine to run on natural gas. But I would be very wary of trying to do this with a diesel engine.

During the compression stroke of a diesel engine the air temperature is designed to climb dramatically above the flash point temperature of the fuel. If the injector leaked because of trying to hold back a gas instead of a liquid, during this part of the cycle one could very easily have significant pre-ignition problems. I would also wonder if enough natural gas could be injected to make enough power for the following power stroke.

Now if one was trying to design a natural gas fueled diesel cycle engine from scratch, that might be interesting. The compression ratio would not have to be so high to meet the lower flash point temperature. I wonder if you could get away with injecting the oxidizer and compressing the natural gas fuel instead? Ah fantasies.

The gas has to be compressed to a high pressure, but will not be as dense as a fluid, so a larger volume of gas charge is needed. Diesel systems prevent cylinder pressure from entering the fuel system, be they natural gas or oil based

problem

the presure needed to get gas to enter cylinder would be enormous.

diesl is a liquid and liquids for all intents cannot be compressed so injection is easier, but presure of fuel is now about 10 atmospheres.

for a gas it would have to be very much higher

I understand your point but air is added to the cylinder, maybe infuse NG into the air-stream?

there is a system here that fits a carburettor like device on the inlet mainfold so engine draws nt into engine and uses diesel ignition in the normal way there is a saving of diesel but not much.

http://www.afsglobal.com/faq/diesel-to-natural-gas-conversion.html

http://autospeed.com/cms/title_Natural-Gas-Fuelled-Diesels/A_108946/article.html

http://www.sae.org/technical/papers/911663

http://www.freepatentsonline.com/6910269.html

hope this all helps

I see some conversions reduce the compression ratio and add spark plugs. Of course, it is no longer a diesel at that point.

What is needed is a method that injects natural gas at high pressure, so it acts like a diesel fuel. The volume of the charge would be somewhat larger, since it is hard to compress a gas to the density of a fluid like diesel, but it could be done. Injecting liquified natural gas I dismiss as impractical on many cases, but could be done with ship diesels where the extra stuff needed would be a lesser burdenThis would preserve the diesel aspect as well as keep the natural gas at a high pressure.

the only way i an see would be to inject the gas first before top dead centre and then inject diesel fuel to the heated compressed air to ignite which would then ignite the gas, timing may be an issue as i dont know how long it would take for the gas to ignite.

assuming the diesel ignites immediatly followed by the gas.

there is also a danger that the gas could lower the temp inside the chamber meaning the diesel wont ignite.

i am sure with some experiment it could be done though

Direct conversion without modification is not possible since the working principles of the two engine is not the same.

In diesel engine, combustion air is compressed so that the temperature of the compressed air has attained the auto-ignition temperature (<300C) of diesel fuel. The diesel fuel is then atomized before injecting into the cylinder. The atomized diesel auto-ignited at that temperature. For natural gas the auto-ignition temperature is too high (>400C) and thus requires high compression ratio which is not achievable by the diesel engine. That is why gas engine or gasoline engine requires spark plug to initiate the combustion of fuel.

Modification is required for such conversion.

There was an method of inducing a metered amount of natural gas with the the air. This enabled the amount of diesel to be burned to be cut back. I am not sure how efficient this was, probably only good for turbo charged types of engines. at least it is simpler than a total rebuild.

I recall some years ago, diesel engines at sewage treatment works ran on something like 80% methane and 20% diesel fuel. The diesel fuel was necessary to lubricate the fuel injection pump(s) and injectors.

I see no major difference today, it would be no simple, or cheap conversion. Much easier and a lot cheaper to use petrol engines for running on natural gas..........however, as yet there are only a very small number of outlets at servos.

Admittedly you can get a home fuelling system for natural gas. That's OK if you are only using it for fairly short distances.

Most generator manufacturers make conversion kits for diesel to natural gas. Gas is not as efficient as diesel so there will be a loss in KVA. We have done it in eco sensitive areas where a fuel spill would not be allowed.

Just remember you will have a reduction in efficiency and you need a high pressure natural gas line to feed it. It will need a lot of fuel.

http://www.cicare.com.ar/fr_dieselgas.htm

the gas is not injected,is carburated as said uphere.Alittle mont of diesel fuel is necesary like for ralenti (this is injected)

And not only natural gas,liquified too.

you would have to lower the compresion ratio.

and i think introduce an ignition source as i dont think nat gas can be compresion ignited