Experiment And Numerical Simulation On The Flow Of Three Leg Pipe In Engine Exhaust System

The continuous improvement of the boost pressure of diesel engines,and gradually stricter emission regulations put forward higher requirementson the design of diesel engine exhaust system. Engine exhaust gas hascomplex three-dimensional flow in the three-way structure and there is aserious loss of local energy. Experiment is the most direct method of gettingflow loss data, with the long test time and the high cost; With thedevelopment of computer technology, numerical simulation play moreimportant role on flow analysis. Experiment study and numerical simulationhave been carried out on the three way structure.At first, a steady-state test bench has been made, and the steady-statetest at different operating conditions has been operated, using the total pressure loss coefficient to show the loss at the T tees, get the staticpressure loss coefficient and the total pressure loss coefficient with thechange of the mass flow ratio. Comparing incompressible flow theoreticalformula with test result, and it indicates that the theoretical formula doesnot apply, the formula need to be corrected with the actual flow test dataof the exhaust pipe; Secondly, process for the PIV test tee structure window,and build a test bench at different Mach number test for three-waystructure of the flow field measurement, analysis of measurement results,compare the flow field at different Mach numbers and different flow ratio.Three-dimensional modeling of the three-way structure, numericallysimulate it using FLUENT code, compare the difference between differentcalculation model and then compare with the experimental values and PIVtest, it shows that the high accuracy of k-omega SST turbulence modelmade it qualified to simulate the flow of exhaust gas in the three-waysjunctions; compare the loss coefficient at different Mach number, it showsthat loss coefficient has less relationship with compressibility. Calculate andcompare models of different degrees, and it shows that the bigger thedegree, the larger K₁₃and K₂₃. Calculate and compare models of differentarea ratio, it shows that the less the ratio, the larger K₁₃and the bigger the ratio, the larger K₂₃.