Originally Posted by BobTurner
Evaporation of liquids is a very powerful cooling mechanism - that’s how most air conditioners work. As you point out, carb ice is a problem with the throttle closed - when air flow thru the venturi, and hence adiabatic cooling, is minimal. What happens is most of those fuel droplets hit the closed throttle plate, and evaporate right then and there, not spread out thru the induction system. Also, you might note that many (most?) fuel injection systems use a venturi to sense the air flow, but almost none of these systems have a ‘venturi heat’ system.
I am aware, Sir. Sorry if I'm being dense but I'm going to be stubborn here. Bare with me.
For a given RPM, the IC engine is a constant volume machine. (Probably) No one will argue that. The volumetric
flow through the venturi (thus ~ fluid speed) does not changep with throttle position alone. I’m aware that usually RPM will not stay that constant Air density on the other hand... Your position assumes that the static P effects are limited to the venturi. That is far from true. At some point of closure, the throttle losses become the predominant pressure loss; very high velocities occur around the butterfly valve. Static P drops proportionately to the square of this velocity.
So I'll ask again. Does anyone have data that supports the previous statement that fuel evaporative effects are the primary driver? I'll state again, the engine OEMs operation recommendations and the experiences posted here by others (at least anecdotally) backs that up as does axial compressors icing, i.e.closing inlet guide vanes increases this risk still without no latent heat effects.
Sorry for the back and forth. Respectfully submitted. I’m really trying to understand the entire proportional relationships.