Simulation of a flow in a supersonic compressor cascade

Abstract

The design of modern aircraft engines cannot be imagined without numerical simulation methods. The advantages of numerical simulation at the first stages of creating engines are obvious: the ability to explore different geometric models in a fairly short time, while the accuracy of calculations reaches 5 ... 15%. An integral part of the numerical experiment is conducting test problems, because of which it is necessary to identify the necessary topology of the computational grid and the turbulent viscosity model. The current study conducts a test problem of flow simulation in a supersonic compressor cascade-based on the STFF rotor to select the topology of the computational grid and the turbulent viscosity model for closing the system of Navier-Stokes equations. In this work, four variants of the computational grid and four models of turbulent viscosity were studied. The time step was automatically changed. The maximum time over time was 0.00005…0.001 s. Control points were set in front of the grating and behind it, where the value of the Mach number was displayed. When calculating, the value of the Mach number in front of the grating was selected by changing the value of the velocity at the input. The calculation was terminated when the values of the Mach numbers at the input and output of the cascade were reached, as well as constant values of the residuals, which did not change during subsequent iterations. 4 variants of the structured type computational grid were built. Grid No. 3 was chosen for further calculations since it provides sufficient similarity with the test results, and it also has a smaller size, which makes it possible to speed up the calculation. Next, calculations are performed for different types of turbulence models. The turbulence models SST, SST GTT, k-ω and RNG k-ε were considered. For all turbulence models, the boundary layer height was chosen based on the condition Y+ < 1. An analysis of the calculation results showed that the smallest error was obtained in calculations with the SST GTT turbulence model. This paper presents a comparison of the density distribution in the cross-section of the cascade with a schlieren photograph obtained from a field experiment. A qualitative analysis of the obtained results shows that the flow patterns around the STFF-based compressor grate are of a similar nature, in particular, in the interblade channel and edge wakes behind the cascade. Thus, for further research to study the flow in the fan, the topology of the Mesh3 computational grid and the turbulent viscosity model SST GTT were chosen.