NOZZLE VALIDATION ANALYSIS More Information  Nozzle has been validated using over 45 test cases from the literature and text book examples. Presented here is one test case using Example 3-3 on page 56 from Rocket Propulsion Elements, Edition 6, by George P. Sutton. The problem is for the design of a nozzle for an ideal rocket motor operating with no shocks (PCRIT-3). To use Example 3-3 as a validation of the Nozzle program, it is more meaningful to start with the dimensions of the nozzle and then determine the thrust, mass flow rate and exit velocity of the rocket motor. Nozzle computes mass flow rate, thrust, and the remaining properties directly from the nozzle geometrical data. The exit velocity is computed from the following equation: Thrust = Mass Flow Rate * Exit Velocity + (Exit Pressure - Atmospheric Pressure) * Exit Area. In this example the Exit Pressure is equal to the Atmospheric Pressure for an ideal nozzle where no shocks are present and the flow exhausts directly into the atmosphere.

Rocket Nozzle Example
An ideal rocket motor operating 25 km above the surface of the Earth has a chamber pressure of 2.068 MPa (2.068 E+6 Pa) and a chamber temperature of 2,800 K. By assuming k = 1.3 and Rgas = 355.4 J / kg*K, determine exit pressure ratio, throat pressure ratio, exit temperature ratio, exit velocity, mass flow rate, thrust, throat area and exit area of the nozzle.

Nozzle 3.7 Input Data
(1) Entrance Temperature: 2800 K
(2) Entrance Pressure: 2068000 (Newtons/m^2)
(3) Atmospheric (back) Pressure: 2549.0 Pa (Newtons/m^2)
(4) Ratio of specific heats: 1.3
(5) Gas constant: 355.4 (J / kg*K = m^2 / sec^2*K)
(6) Nozzle length: 1.0 m
(7) Throat Diameter: 0.04202 m
(8) Throat location: 0.25 m
(10) Entry angle of conical section: 12 degrees
(11) Total number of grid points: 400

 Nozzle 3.7 Results Compared to Sutton's, Example 3-3 Exit Pressure Ratio [Pe/P0] Throat Pressure Ratio [Pt/P0] Exit Temperature Ratio [Te/P0] Exit Velocity [m/sec] Mass Flow Rate [kg/sec] Thrust [N] Throat Area [m^2] Exit Area [m^2] Example 3-3 .0012 .546 .2131 2605 1.919 5000.0 .001387 .06125 Nozzle 3.6 .0012 .543 .2132 2605 1.918 4997.2 .001387 .06127

Nozzle 3.7 Input Data Nozzle 3.7 Output Data 