Direct simulation monte carlo model of low reynolds number nozzle flows

Numerical analysis of low Reynolds number nozzle flows is performed to investigate the loss mechanisms involved and to determine the nozzle wall contour that minimizes these losses. The direct simulation Monte Carlo method is used to simulate nitrogen flows through conical, trumpet-shaped, and bell-shaped nozzles at inlet stagnation temperatures of 300 and 1000 K. The Reynolds number of the flows based on throat diameter range from 90 to 125. The trumpet-shaped nozzle has the highest efficiency with the unheated flow. With the heated flow both the trumpet and bell-shaped nozzles have a 6.5% higher efficiency than the conical nozzle. The conical nozzle has the highest discharge coefficient, which is unaffected by the change in stagnation temperature; however, the increase in stagnation temperature increases the heat-transfer and viscous losses in the boundary layer. These results suggest that the trumpet-shaped wall contour performs most efficiently except near the throat region, where it incurs large viscous losses. However, the bell-shaped nozzle may increase its overall performance with an increase in stagnation temperature.