Question

Based on first order statistical jet engine model, we have been given a task to design a subsonic non afterburning engine which is operating at maximum Mach number of 0.7. Evaluate the approximate length required to build this engine. Given thrust at takeoff is 9600 unit.

(a) 81 unit

(b) 10 unit

(c) 20 unit

(d) 22 unit

I got this question in final exam.

The question is from Propulsion in section Propulsion and Fuel System Integration of Aircraft Design

Answer 1

Correct option is (a) 81 unit

Explanation: Given, Thrust = 9600unit, Mach number M = 0.7

Length L = 2.22*T^0.4*M^0.2 = 2.22*9600^0.4*0.7^0.2 = 2.22*39.165*0.9311 = 80.95 ∼ 81 unit.