Can Delaval Valves Reduce Diesel Engine Air Cooling?

[chhitiz]

the diesel cooling engines as produced by deutz have huge fans to deliver substantial amounts of air to the engine. they draw a lot of power from the engine. is it possible to use a mesh of delaval valves like a radiator that drops the temperature of passing air, thus, reducing the amount of air required and thus, using a fan that requires lower power?

 

[brewnog]

Do you mean an air cooled engine?

 

[chhitiz]

yes i do

 

[Mech_Engineer]

In general, air cooled engines have fins on the cylinder head and block to accomplish exactly what I think you are getting at.

Examples:

 

[famousken]

the diesel cooling engines as produced by deutz have huge fans to deliver substantial amounts of air to the engine. they draw a lot of power from the engine. is it possible to use a mesh of delaval valves like a radiator that drops the temperature of passing air, thus, reducing the amount of air required and thus, using a fan that requires lower power?

You could do that and use less power for the fans, but it would be pointless because any gains from the fans using less power is going to be largely offset by the power required to cool all the air passing through the motor.

 

[chhitiz]

You could do that and use less power for the fans, but it would be pointless because any gains from the fans using less power is going to be largely offset by the power required to cool all the air passing through the motor.

the aerodynamics would be at a disadvantage, yes, but by how much it increases the consumption of power in comparison to the reduction in power required by fans could only be found using a wind tunnel test or something, i guess.

In general, air cooled engines have fins on the cylinder head and block to accomplish exactly what I think you are getting at.

Examples:

i thought they only increase the area of contact.

 

[brewnog]

So you want to use the engine's power to chill its own cooling/ventilation air, so that lower air flow rates are needed, so that you reduce the power consumption of the ventilation fans?

I think you need to do some basic thermodynamics around this to prove to yourself that energy consumption would actually increase.

 

[chhitiz]

that's exactly what i want to do and that's exactly what i need to do, thank you. where am i to get the basic stats for these engines to do the maths?

 

[brewnog]

If you want heat rejection figures for the engine, look at the manufacturer's technical data sheet.

 

[russ_watters]

The compressor of an air conditioner uses a lot more energy than the fan, so this idea is fundamentally flawed. You don't gain efficiency by cooling the air, you lose it.

In addition, the approach temperature for an air cooled engine (the difference between the air temp and the heat exchanger surface temp) is so large that air conditioning the incoming air will have very little effect on the airflow required.

 

[russ_watters]

It sounds like you want to cool air by pressurizing it and then running it through a nozzle where it will expand and the temperature will drop. That is not an efficient method of cooling air. In particular, the energy used by a fan or compressor is a linear function of the flow rate and pressure. You should probably look into the thermodynamics of compressors and throttling valves/nozzles. A supersonic wind tunnel uses a huge amount of energy to compress the air enough to run it through a c-d nozzle.

 

[hhn2002]

the simple no mess, no fuss, no equation to seeing if it actually helps solution is to add fins or bigger fins. that way you know it would necessitate a lower fan speed thus lower power consumption. my mantra is the simpler the solution the better.

 

[chhitiz]

The compressor of an air conditioner uses a lot more energy than the fan, so this idea is fundamentally flawed. You don't gain efficiency by cooling the air, you lose it.

In addition, the approach temperature for an air cooled engine (the difference between the air temp and the heat exchanger surface temp) is so large that air conditioning the incoming air will have very little effect on the airflow required.

i am not using a compressor. the forward motion of the vehicle will cause the air to be forced through the nozzles, and so, expand and contract. i am really not sure if this is going to work.

 

[chhitiz]

In addition, the approach temperature for an air cooled engine (the difference between the air temp and the heat exchanger surface temp) is so large that air conditioning the incoming air will have very little effect on the airflow required.

that's a good point. this whole thing was a very stupid idea.

 

[russ_watters]

i am not using a compressor. the forward motion of the vehicle will cause the air to be forced through the nozzles, and so, expand and contract. i am really not sure if this is going to work.

Cars have fans on their radiators because they need to be able to cool themselves when stopped, but in either case, the energy to make the air move (via the fan or via the wind) comes from the engine.

 

[russ_watters]

that's a good point. this whole thing was a very stupid idea.

Don't look at it that way - look at it as a learning experience. Look into the actual thermodynamics of C-D nozzles and fans and prove to yourself whether it will or won't work.