Unsteady Simulation of Six-Inlet Pulsed-Flow Turbocharger Turbine 2020-01-2237

The turbochargers are driven by unsteady, pulsating flow. Such flow is generated by the exhaust phase of an internal combustion engine (ICE). A lot of turbocharger simulations are done during steady-state operation. Such simulations are favorable for turbocharger optimization at a certain operating point. However, the frequency and amplitude of exhaust pulses can heavily influence turbine performance. This paper presents the results of the three-dimensional (3-D) simulations of the six-inlet turbocharger turbine, under pulsating operation with a moving mesh approach. One of the key points of interest was the separation of the pressure pulses from the six-exhaust pipes during engine operation. The leakage between the exhaust pipes was analyzed at each time step at the different turbine speed. Another key point was the turbine response during pulsating flow at the different rotor speed. Parameter such as the turbine total-static efficiency under the single-pressure pulse was investigated. Also, the exhaust pipes were studied to check its filling-emptying behavior. The article is divided into three parts. The first part contains the in-depth literature review concerning turbochargers operation under pulsating flow. The second part contains a description of the problem and the computational approach. For the study, the 3-D transient simulation was considered. The last part contains the results and conclusions. The results showed, that the highest efficiency was achieved for the turbine speed of 60000 rpm. However, a deeper study is needed at higher turbine speeds. The most important fact is that the six-inlet turbine configuration successfully separated exhaust pulses from each cylinder, however, a minor leakage from one exhaust pipe to another was observed. Such a solution will be used in the exhaust system of a newly-designed opposed-piston engine.