fuel pipe insulation

there are double layer pipes available in stainless steel with ceramic , plastic composite sandwitched google should help you

There is great stuff available for automotive racing. It's kind of a wrapping thing, like the doc puts on when u broke your arm/leg. It doesn't harden out and therefore stays flexible for life. I've seen a demonstration where they lay a wrapped, live fuel-line on top of a red glowing exhaust pipe /header of a formula 3 racecar. Can't remember the name of the company though, sorry.

The company in the US that sells the automotive thermal wrap is Thermo Tec.

Here is the link: http://www.thermotec.com/full.php

Ex-NASA engineers that worked on shuttle I believe.

Fantastic stuff. I use it in my Porsche 914 and have had no problems with overheating in the engine compartment with a V8 engine under the hood.

You can also just build a heat shield from a flat piece of metal, very thin. Heat shields are very effective. Please tell me, for safety what is your intent? To keep the fuel inside cool and hence have slightly more power, or are you vaporising the fuel ?

Dear Sir, thanks for reply. I want to keep the fuel inside the injection pipe cool. A metal shield will work, but I want to insulate the pipes as well. The other alternative is to insulate the exhaust pipe between the cylinder head and the turbo, but there is always a risk in overheating the turbo charger, thus I thougth it migth be the best to insulate the fuel pipes if possible.

Hi B.

But why do you want to keep the fuel cool? Just because it makes sense (bothers you), or are you trying to solve a problem such as power loss (fuel density changes) or fuel vaporisation (severe knocking noises and injection timing issues as the vapor compresses in the fuel lines). Or is it for fire protection? Careful with insulation for any type of fire protection shielding the hot surface, or, pipe shielded from the hot surface. Any hydrocarbon liquid that leaks may collect in the wetted insulation and cause what is termed a 'wick fire' where the fluid is held near the heat until is vaporises to a 'gas' and ignites when it changes phase finding the heat source more readily. I teach a class on 'Diesel and Natural Gas Engines for Use in Hazardous Zones'.

You will not overheat the turbo changer by insulating it. Another fact is by insulating the exhaust manifold prior to the turbocharger you improve the turbo performance slightly, but take on risk of a wick fire if your fuel lines are near by. If those are the injection lines leading to each injector they can have 700-2000 barg (10,000 - 30,000 psig) fuel pressure inside depending on the model of injection pump and load. If you want to feel how efficient a heat shield will be just pass a thin piece of card board or even thick paper between the exhaust and your hand momentarily and you will feel a tremendous change in heat transfer, instantly. Or do it with any heat source in your home. But as others point out, support it well as it will vibrate and break off.

A damn good post, totally agree....

I found signs of excessive heat on some of the injector nozzle needles. Some of the injector lines are clamped close to the exhaust pipe (before the turbo), there is also 'burning' signs on the piston crown as if the injection timing was too early, thus I thought to insulate the fuel line- in general it is very bad to run fuel supply lines next to the exhaust pipes. The injection pressure is 240 bar. When calculating it I found that each shot of fuel spend around 0.85-0.90 seconds at, max power, in that hot area before injected. I do not know what will the influence be on the injection timing if the fuel density changed (because of temperature) and it reach the point of fuel vaporisation.

Then I would try a heat shield. I'm not doubting your trouble shooting capability especially if you have a lot of experience with diesel engines (most of my recent experience is from 2,000 kWb to 10,000 kWb sizes and this may not apply here . . . . and experience 20 years ago with Cummins, DDAD, & Caterpillar 30 kWb to 2,000 kWb), but I will offer my experience. Vaporising the fuel is unlikely due to extreme pressures that will keep the fuel liquid unless you have very light load and the fuel is extremely hot in the injection pipes. Most hot fuel vapor lock flashing occurs BEFORE the injection pump and the injection pump tries to pump a gas/liquid. If it enters the injection pump liquid, I'm very sure it will stay liquid at your temperatures and pressures, even at light load where injection pressure is quite low. Super heated fuel MAY cause carbon deposits on the tips and deflect the spray. I don't think hot fuel would 'eat' away at orifices. The erosion of orifices it more a design issue with the exit edges not having a slight radius.

If this is a unit injection system where there is a high return line volume (several liters / minute) just measure the return line fuel temperature then steal your wife's cookie sheet and shove one between the turbo or exhaust pipes and the fuel lines and see if the return line temperature changes. I don't think it will change much, but it will be educational for me if it does.

If you are referring to the piston crown with a star burst spray burn pattern on it, this is normal.

Andy of Germany seems to have a great deal of wisdom on diesel engines (more than I do !) so maybe he will offer his thoughts.

Photos?

George

I agree with you mostly on all of your commentary, in a well running system, there should be no problems.

But there is a danger, that once Diesel has exceeded its flash point of just under 50°C, that a simple leak could turn into a horrendous fire within seconds.....a shield would not only keep the temperature down, but if well designed, should also prevent the (cold) leaking diesel actually hitting the hot exhaust pipe!!

Depending upon the size of the return tank, its insulation etc and the amount of hot diesel, it could also be possible that the temperature of the tank slowly rises over a long period!!! If above the flash point, nasty explosive vapours are produced....

Furthermore, with hot Diesel and US regulations (as in many countries) you must add a flash eliminator if the diesel rises I believe at any point above 47°C!!! Perhaps someone can get better infos here on that point please?

I feel that the fuel lines should be shielded to reduce the possible fire risk if something ruptures.....

usually radiant heat is the problem, like from a Catalytic converter. Most car manufacturers use reflective metal and an air gap to stop the heat going into the wrong bits, but you must have some airflow around the area too.

I would place two shields on the engine, one around the hot bits and another around the bits that should not get hot....stainless steel, firmly mounted, but with as big an air gap as possible.

There was a Blog about this already this year, that was the fix. Sorry I can't find it again.