Question

If the given conditions for a nozzle are P01 = 1 atm, Pe = 0.3143 atm, then what is the ratio of exit area to throat area?

(a) 1.15

(b) 1.5

(c) 1.25

(d) 1.115

The question was posed to me in unit test.

This interesting question is from Nozzles topic in chapter Quasi-One-Dimensional Flow of Aerodynamics

Answer 1

Right choice is (d) 1.115

Explanation: Given, P01 = 1 atm, Pe = 0.3143 atm

To calculate – \(\frac {A_e}{A^*}\)

Stagnation pressures remain same P01 = P0e

\(\frac {P_{0e}}{P_e} = \frac {1}{0.3143}\) = 3.182

For \(\frac {P_{0e}}{P_e}\) = 3.182 we get Me = 1.4 (Using gas table)

For Me = 1.4, we get \(\frac {A_e}{A^*}\) = 1.115 (Using gas table)