Question

A liquid propellant engine has the following characteristics: chamber pressure of 7 MPa, constant ratio of specific heats of 1.3, and a characteristic velocity of 1600 m/s. The nozzle has the following characteristics: throat area of 0.010 m2 and an expansion ratio of 10. Calculate the following:
1. Thrust coefficient at sea level
2. Specific impulse at sea level
3. Altitude at optimal expansion
4. Thrust coefficient at optimal expansion
5. Mass flux through the throat

Answer 1

Answer:

1. 1.55
2. 260 N.s
3. 3370 m
4. 1.6
5. 43.75 kg/s

Explanation:

1) Thrust coefficient at sea level.

Cfsl = TSL / Pca

TSL = Mp * Vc  + ( Pc - Pa )Ac

Mp = mass flux = 43.75 kg/s

∴ Cfsl  = Mp Vc / Pca  + ( Pc - Pa )/Pc * ( Ac / A* )

           = 1.6 - 0.04923 = 1.55

2) Specific impulse at sea

Isp = Vc / g = 2549.75 / 9.81

                   = 260 N.s

3) Altitude at optimal expansion

H = 3370 m

4) thrust coefficient at optimal expansion

CF = 1.6

attached below is the detailed solution

5) Mass flux through the throat

Mass flux = P1 * At / Cc

                = ( 7*10^6 * 0.01 ) / 1600

                = 43.75 kg/s