Numerical Simulation And Experimental Investigation Of A Twin-branch S-shaped Compressor Transition Duct

The twin-rotor structure is the mainstream of modern turbofan engine.The duct is the inter-stage component,which transmits the flow from the low-pressure compressor to the high-pressure compressor.The high-pressure compressor and low-pressure compressor are not at the same radius,so the compressor transition duct is designed to be the "S" type.In order to shorten the length of the compressor rotors,reduce the load of the rotors system and improve the reliability of the engine,the axial length of the compressor transition duct should be shortened.This paper carries out numerical simulation and experimental investigation on a twin-branch S-shaped compressor transition duct.First of all,the test plan of the twin-branch s-shaped compressor transition duct is carried out.The proportion of the test model was determined by the shrinkage effect of the model and the gas supply capacity.According to the requirements of the test plan and the structure of the test model,the test plan was determined.Then,the numerical results of a twin-branch S-shaped compressor transition duct are compared with the experimental results.It is founded that the numerical results are in good agreement with the distribution of the experimental results.Obviously,it proves that the numerical simulation method has considerable credibility.The test results of a twin-branch S-shaped compressor transition duct are analyzed.For the exit of core duct,the upstream horseshoe vortex develops into a channel vortex and the vortex near the hub region pumps the low total pressure fluid from the near-hub wall boundary into the mainstream passage,which cause a high pressure loss.For the exit of bypass duct,the horseshoe vortex has a large pressure loss in the casing-strut area.With the bypass ratio increases,the range of high total pressure loss near the end wall of the hub is enlarged.With the inlet Mach number increases,the total pressure loss range near the exit of the core duct and bypass duct is extended.Finally,the numerical results of a twin-branch S-shaped compressor transition duct with different thickness strut are analyzed.With the strut thickness increases,we find that the thick strut strengthens the secondary flow and enhances the horseshoe vortex on the surface of case and hub.The larger total pressure loss caused by the wake flow is significantly increased.