Optimum droplet size?

[Aquaman]

Originally Posted by Richard L

My point was, super-fine droplets will only be effective up to a certain point. Similarly the water molecular in the induced air during the day has little effect on cooling compared to the mist on a cool evening (larger molecule).

Interesting point! Has anyone used ambient humidity sensors to modulate the flow volume of their water injection systems to maintain the "target" 15% water to fuel ratio without wasting precious reserves or over diluting the oil without benefit?

Is 165 degrees celsius/330 F an appropriate compressor outlet temperature for a 60% efficient turbo given 10 deg C/50 F ambient air?

I found an interesting website on evaporative cooling that is very similar to our discussion...

http://www.cheresources.com/cementkiln.shtml

if you knew the droplet size and boost pressure/charge pipe diameter to calculate air velocity couldn't you extrapolate from that information approximately how far a known mass of water would make it before being completely evaporated and where a second stage of water injection would be needed to make it into the combustion chamber? I guess port velocity would change based on throttle position but perhaps if calculations were based on WOT it would be more than adequate?

How would you know how much additional is needed in the combustion chamber? Wouldn't that cause more oil dilution and if temperature were dropped too much result in reduced efficiency? I am assuming that 15% target number builders shoot for has been derived from the NACA articles and those articles do mention excessive oil dilution if I remember correctly.

[Richard L]

Originally Posted by Aquaman

if you knew the droplet size and boost pressure/charge pipe diameter to calculate air velocity couldn't you extrapolate from that information approximately how far a known mass of water would make it before being completely evaporated and where a second stage of water injection would be needed to make it into the combustion chamber? I guess port velocity would change based on throttle position but perhaps if calculations were based on WOT it would be more than adequate?

How would you know how much additional is needed in the combustion chamber? Wouldn't that cause more oil dilution and if temperature were dropped too much result in reduced efficiency? I am assuming that 15% target number builders shoot for has been derived from the NACA articles and those articles do mention excessive oil dilution if I remember correctly.

Since you cannot separate the the effect of water during it's journey from the intake to the exhaust, the only control you have is the manipulating the droplet size. Although the enthalpy change at the inlet tract is minor compared to combustion chamber, it is significant. That said, it is not as easy as you think because of the large swing of conditions due to the varying environment change.

I believe a wmi system should track overall engine load rather than just boost, a single entity is subject to change depending on gearing and rpm. The aquamist system tracks fuel flow, has been extremely successful in keeping the flow from "over" and "under" cooling. At the same time, keeping the droplet as small as possible to maximise the effect of induction cooling. It is just speaking from past experiences.