Law handed me a sheet with three questions that I could look over and think about while waiting for the
other examiner to arrive. He is nice in the general, and asks good leading questions.
1.) What is the effect of pressure on the following:
a. Flame speed of a premixed flame
b. Adiabatic Flame Temperature
c. Droplet burning of a HC Fuel
d. Droplet burning of a monopropellant
e. Extinction due to radiation heat loss
Pretty Straightforward, one little trick was that pressure has no effect on the HC droplet burning, but
does affect monopropellant burning, because it works like a premixed flame. For the last part he
wanted me to know the equation with f*ln(f)=loss (or was it f^2 *ln(f^2)?) which I didn’t know
2.) What happens to a droplet burning in air as the air speed over the droplet is increased?
At U=0, you have standard spherical droplet burning. Increasing the speed distorts the flame, and also
causes fluid motion in the droplet. Increasing the speed more, there is no longer a flame in front of the
droplet, only behind it, in the wake. At this point he asked what is the criteria for the flame to move
from the front of the droplet to the back. Also, where is it stabilized in the back, and why. We also
talked a little about boundary layer separation and recirculation and how that affects the location of
stabilization. Next he asked if the flame can be stabilized even farther from the droplet, if the speed is
increased more. I didn’t really know, but we came to the conclusion that a tribrachial flame would be
stabilized far back in the wake, like a lifted Bunsen flame
3.) We didn’t actually get to this question because we ran out of time. I don’t remember what it
was