Quote:
Originally Posted by Harlan
An ultrasonic mister would work, but depending on your engine vacuum/coolant temp it would be unnecessary due to the lower boiling point at vacuum. Also water injection and steam injection act as internal coolants. You can quickly see your coolant temps drop off when injecting, so depending on amount injected/engine load you might run out of useable coolant heat as the thermostat pinches down. Also as stated before controlling the amount/moisture content of the injected steam is the devil in the details.
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Ultrasonic devices are fantastic at generating very small water droplets. Couple that with elevated temps, and the vacuum as you mention and it will provide for a very elegant way to transfer thermal mass from your coolant system directly to the combustion chamber. If I were designing a system like this I would create a device that would allow a useable and functional minimum of water vapor to be injected(or boiled by coolant temps at vacuum conditions) with the Ultrasonic off, and use the ultrasonic to help control the process to the desired setpoint from there. The ultrasonic could also be sized and activated so that during low vacuum conditions(acceleration) that minimums of water vapor content could be met. The ultrasonic misters can be controlled-simple on/off, or other by other more precise means(similar to a light dimmer on your wall for AC systems).
I wouldn't think that your temps wouldn't drop significant amounts, but perhaps stabilize at a slightly lower temp. Remember we are preheating the water to coolant temp before ultrasonically vaporizing it instead of injecting cold water like the systems that use pumps and all-I could see how the latter would decrease the coolant temps by a much larger amount. Also the water vapor in the combustion chamber would change the heat transfer characteristics of the combustion process(allow more combustion heat to potentially be rejected into the cylinder walls) and so a new coolant temperature might need to be investigated to get a coolant temperature which doesn't give or take away heat from the combustion event.
So all in all were taking thermal energy from the coolant system(that would otherwise be wasted through the radiator) adding it to water, vaporizing the water ultrasonically(which will cool the water a certain amount) and adding this to the intake stream. Essentially we are increasing the thermal mass of the intake air and more closely thermally bridging the intake, combustion, and coolant processes/systems.