Fuel for cooling

[trinidefender]

Wondering if there is any advantage to running fuel through maybe part of the block or head before it enters the fuel pump/injection rail/injectors or whatever. To my knowledge this may have 3 advantages.
1. Helps remove some heat from the engine so therefore less work for the water based cooling system. Yes I know it may only be a few percent but in F1 teams are forever chasing very small gains.
2. As more throttle is used more fuel is used for cooling, therefore as more heat is generated by combustion more heat is removed from the engine as result of more fuel flowing through the engine used as cooling.
3. Hotter fuel should help the fuel atomise. Hence helping the fuel burn quicker and be more stable with more complete combustion. I will have to check my chemical engineer sources to verify this so don't quote me on it.

I got the idea because the helicopter I fly has a device that uses heat from the engine to pre-heat the fuel however the reason given by the manufacturer is to stop fuel jelling up in the fuel lines (in addition to a anti-ice additive)

Thoughts?

[Nuvolari_the_legend]

I think it is a good idea. But I don't have very much technical experiance.

I can see some problems, but I don't know if they are actualy problems or not.

A issue I think of is: doesn't fuel expand when it gets hotter and when it does, what effects will it have.

[Holm86]

You are expanding the fuel when heating it. This means the energy per volume decreases. So you either have to increase fuel pressure (there is a max pressure regulation) or you have to inject for a longer period. That is not great in a high rpm engine such as an F1 engine.

Plus the fuel is already cooling when its injected into the combustion chamber. So I dont see a point in trying.
The helicopter you run is a different matter. Is it even a piston engine??

[trinidefender]

You are expanding the fuel when heating it. This means the energy per volume decreases. So you either have to increase fuel pressure (there is a max pressure regulation) or you have to inject for a longer period. That is not great in a high rpm engine such as an F1 engine.

Plus the fuel is already cooling when its injected into the combustion chamber. So I dont see a point in trying.
The helicopter you run is a different matter. Is it even a piston engine??

You misunderstand my intention. It is mainly to remove some heat from the engine itself and take some load off of the conventional cooling system allowing it to be designed smaller. Well the fuel flow is measured by weight of fuel/time not volume so the fuel being at a lower density shouldn't be a problem with the amount fuel allowed being used. Saying the fuel is cooling by the time it reaches the combustion chamber is pointless is silly, the fuel will still be quite a bit hotter than it would have been when it left the tank.

I can see your point about fuel pressure limits and injection duration but I'm sure teams will be able to overcome this if not this year then in the coming years.

This is slightly irrelevant but the heli is not a piston. It is a gas turbine engine. I didn't say that the application between the F1 car and the heli would be the same just that that is where I got the idea from.

[flyboy2160]

The concept using fuel for cooling while also warming the fuel isn't unique to your helicopter. It's also used in high altitude UAVs when the fuel is too cold.

But it doesn't seem like good idea in F1. What are you going to do with the heat from the fuel? Dump it out in a fuel/water/air intercooler? Allow the fuel to get hotter and hotter? And what happens to the scheme as the fuel volume gets lower and lower?

[trinidefender]

The concept using fuel for cooling while also warming the fuel isn't unique to your helicopter. It's also used in high altitude UAVs when the fuel is too cold.

But it doesn't seem like good idea in F1. What are you going to do with the heat from the fuel? Dump it out in a fuel/water/air intercooler? Allow the fuel to get hotter and hotter? And what happens to the scheme as the fuel volume gets lower and lower?

I was thinking more of only allowing the fuel that is already on its way to the injectors to be used for cooling. Or maybe on a car with a water to air intercooler there can be a part of the intercooler (engine side) that uses fuel that is already on its way to the engine to cool the charge air.

[Lycoming]

Honda did this on their 1988 F1 engine. They stated that it actually decreases thermodynamic efficiency, but with the fuel they were using then, heating it a bit helped with vaporisation, so they actually had a net gain. It was simpler than what you suggest, they just run it up against the hot water as opposed to circulating it through the block/head.

I don't think that advantage is retained with modern fuels.

Commercial jet airliners do this for different reasons. They have a device called the fuel-oil heat exchanger. Cold fuel from the wing tanks needs to be heated, and hot engine oil needs to be cooled; using fuel to cool the oil also heats the fuel, thus killing two birds with one stone. F1 cars don't store fuel at -40 though.

[flyboy2160]

....
I was thinking more of only allowing the fuel that is already on its way to the injectors to be used for cooling. Or maybe on a car with a water to air intercooler there can be a part of the intercooler (engine side) that uses fuel that is already on its way to the engine to cool the charge air.

You'd have to run the numbers to be sure, but I doubt that the little bit of fuel being injected has enough mass to do any worthwhile cooling compared the mass of the water and oil flows. Heating that little bit of injected fuel for a fuel reason is a different issue from cooling the engine.

[langwadt]

....
I was thinking more of only allowing the fuel that is already on its way to the injectors to be used for cooling. Or maybe on a car with a water to air intercooler there can be a part of the intercooler (engine side) that uses fuel that is already on its way to the engine to cool the charge air.

You'd have to run the numbers to be sure, but I doubt that the little bit of fuel being injected has enough mass to do any worthwhile cooling compared the mass of the water and oil flows. Heating that little bit of injected fuel for a fuel reason is a different issue from cooling the engine.

gasoline is about 2.2 j/gK , so heating 100kg from 25 to 100'C => 100000*2.2*(100-25) = 16.5MJ
compare that to 100kg*45MJ = 4500MJ burned off

[turbof1]

There's some merit to it:

http://www.somersf1.blogspot.co.uk/2014 ... cture.html

This joined up thinking is also present with the way in which Mercedes have installed their cooling options for the WO5 with an air-liquid-air cooler residing somewhere within the area also occupied by the fuel cell (note I've placed it vertically in the image above but it may reside in another orientation, with the way fuel drains off and centre of gravity affected by this too), a shrewd option but one that will have clearly needed the assistance of their fuel supplier Petronas to provide them with a fuel that is able to regulate not only its own temperature requirements but those of the air-liquid-air cooler without causing major peaks or troughs in it's temperature. (It's worth noting that both Force India and Williams are using Petronas fuels this year too but their grade is likely somewhat different, Williams will move to Petrobas in 2015 I believe, due to their partnership with the team and Felipe Massa). The air-liquid-air cooler requires an additional water radiator which resides in the WO5's sidepod.

[Billzilla]

Useless trivia.
The SR-71 Blackbird spy plane used a system along those lines.
The airframe had multiple fuel tanks all over the place and the on-board computers would both sense the temperature of the fuel and also pump the fuel around to manage the centre of gravity. It would send the hottest fuel to the engines as the fuel was used as a heat-soak for the airframe, so the system used the fuel to cool the aeroplane and dump that heat out the exhaust of the engines. There were a few limits to the maximum speed & power the aeroplane could use and one of them was the fuel temperature into the engines; not a problem just after refuelling in the cruise when the fuel was still relatively cool but towards the end of the high-mach cruise segment where there was little fuel for cooling they may at times had to have reduced power.