04 / Engine Nozzle Gas Dynamics Simulation

PROBLEM STATEMENT

For this project, the scope was to simulate gas dynamics in a converging-diverging nozzle using ANSYS Fluent. It was also analyzed how variations in back pressure, diverging angle, and throat radius impacted key parameters like Mach number, static pressure, and mass flow rate.

First, the geometry of the converging-diverging nozzle (provided in problem statement) was constructed in Ansys Design Modeler .

SIMULATION VARIABLES

Next, simulation outputs were recorded as per Table on the left to observe the following:

The Mach number and static pressure contour and their variations plot along the nozzle (x-axis).

The mass flow rate and maximum Mach number along the Nozzle as Variable output parameters to monitor. These values for each iteration were recorded in Excel format and the outcome was analyzed.

Results Summary

Values of Parameters Across All Iterations

1. Back Pressure Reduction:

Reducing back pressure raises the maximum Mach number and mass flow rate.

2. Diverging Angle:

The performance measures are not significantly affected by altering the diverging angle (7° vs. 5°). However, decreasing the diverging angle reduces the outlet area, resulting in a lower Mach number at the nozzle exit.

3. Throat Radius:

Generally speaking, and especially at lower back pressures, a smaller throat radius (10 mm vs. 12 mm) increases the maximum Mach number and the mass flow rate.

As a typical example of the process for the simulations of each iteration, Iteration 1-1 is shown below as an example:

For detailed data on all the iterations, please refer to the full report pdf in the link here: Full report

Simulation Process: (Iteration 1-1)

MACH NUMBER CONTOUR, VARIATION PLOTS

STATIC PRESSURE CONTOUR, VARIATION PLOTS

INPUT AND OUTPUT PARAMETER VALUES

We discovered that reducing back pressure increased the Mach number, smaller throat radii enhanced flow performance, and changes in diverging angles had minimal effects.

Our work allowed us to explore phenomena such as choked flow, supersonic transitions, and shock wave behavior, providing valuable insights for optimizing nozzle designs in aerospace applications.

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