Okay, this may be somewhat of a new approach in some respects, but could those of you with some thermodynamics expertise bear with me on this one and give me some input.
Going right back to the beginning of this thread and trying to incorporate as much of the theory as I can from the wealth of knowledge that has followed on, I have grasped these main concepts.
(1) Pre-compressor injection is unique in that it can increase compressor efficiency by pushing compression away from adiabatic towards isothermic (I hope I got those terms correct);
(2) Whilst larger volumes of liquid injected pre compressor may reduce temperatures by a greater amount at the compressor, a point of diminishing returns can be reached because (a) this may reduce intercooler efficiency resulting in intercooler outlet temps increasing and (b) saturation occurs whereby no more water can evaporate and consequently no further heat can be absorbed.
(3) Therefore, ideally we want to inject just enough water to achieve (1) without inducing either of the diadvantages of (2);
(4) Water has the greatest ability of all substances injected to absorb latent heat; and finally
(5) In order to prevent or at least substantially reduce compressor blade damage we want to inject water droplets of the smallest size possible (ideally 10 microns or less and certainly no larger than 50 microns)
So, a few questions.
(1) Does a mist of water vapour at ambient temperature absorb any less heat when injected than say a mist of water that is chilled to 10 degrees celsius immediately prior to injection?
(2) If the answer to (1) is that cooler water absorbs more heat, then would water injected at it's lowest liquid temperature (i.e. 1 degree celsius) be more or less effective in absorbing heat than the same volume of an alcohol and water mixture that could be injected at below the freezing point of water?
The reason I ask this is that people have been injecting propane instead of water pre compressor for years. Propane enrichens the octane level of the final fuel mixture as well as expanding at a phenomenal rate which reputedly also helps distribute fuel in the combustion chamber better, which in turn leads to fewer hotspots.
As such it also suppresses detonation but NOT by reducing the temperature of the intake charge. Injected for the most part as a vapour all the cooling effect takes place at the propane container which becomes cold to the touch, but the cooling effect on the intake tract is minimal.
Okay, this is where it starts getting interesting. Forget safety issues for now, I am not interested in those for the purposes of this discussion. During actual application yes, but NOT here. I have a Propane Injection System which uses a solenoid at the injection point (like a nitrous system). The bottle is inverted and the delivery line once purged of vapour remains under pressure prior to injection. Propane is thus injected as a liquid. Propane 'boils' at -40 degrees (that coincidentally is roughly the same in either fahrenheit or degrees).
Since it becomes a gas almost instantaneously it probably won't absorb much latent heat - accepted
It does however have an octane rating of around 110 which means it really can replace any fuel it displaces although it takes up a considerable volume of 'airspace'.
So suppose we used a nitrous wet fogger injector which simultaneously injected liquid propane at 40 degrees below zero together with a water and alcohol mixture (composed of the greatest percentage of water possible that would not freeze) and injected it pre compressor.
I can see a number of possible issues;
(1) Catastrophic impeller damage created by a phenomenal change in temp from several hundred degrees to -40
(2) The mixture is unable to absorb heat;
(3) Temperature differential results in condensation and compressor damage;
(4) Loss of intercooler efficiency; and
(5) The fogging effect even under 400 plus psi fails to atomize the liquid to less than 50 microns.
However, given the number of devices used to reduce air intake temperatures and the advantages of isothermic compression, I would think that there must be some merit in this idea even if the injection point needs to be re-evaluated.
I'd value your comments.
Paul.
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