Question

What is the diffuser efficiency of a normal shock diffuser?

(a) 1

(b) 0

(c) Inifinty

(d) \(\frac {1}{2}\)

The question was asked in my homework.

I want to ask this question from Quasi-One-Dimensional Flow Diffusers in division Quasi-One-Dimensional Flow of Aerodynamics

Answer 1

Right answer is (a) 1

The best explanation: The diffuser efficiency compares the actual pressure ratio of a diffuser \(\frac {p_{d_{0}}}{p_0}\) and the total pressure ratio across a normal shock \(\frac {p_{0_{2}}}{p_{01}}\) . The formula is given by:

ηD = \(\frac {(\frac {p_{d_0}}{p_0})_{actual}}{(\frac {p_{0_2}}{p_{01}} )_{normal \, shock \, at \, M_e}}\)

The numerator will be equal to the denominator for a normal shock diffuser, hence the efficiency is one. For subsonic flow, the siffuder’s performance is lower resulting in efficiency which is less than unity. And for the hypersonic flow the efficiency is greater than unity since it has a better shock recovery.