Experimental and modelling investigation on unsteady effects in compressor and turbines of current and future Diesel engines

摘要

In actual scenario a precise knowledge of unsteady effects such as compressor surge, thermal transient or unsteady flow influence on turbocharger efficiency, is needed. In the paper the methodology followed at CMT-Motores Termicos, which is based on combining experimental facilities and models able to deal with these unsteady effects, is described. The paper describes such facilities that include steady and transient gas-stands, engine test beds and a thermal bench. Several methodologies have been developed to characterize properly unsteady phenomena in turbochargers. In the paper, several tests are proposed to measure properly surge inception limit as far as it depends on the actual engine operation conditions both on gas-stand and on engine test bed. An innovative methodology is presented that allows for measuring the pulsating effects in turbines, including the actual pulsating isentropic efficiency. The experimental work goes along with compressor and turbine models that account for the unsteady effects. These models, implemented in a 1D gas-dynamic code, become a powerful tool in turbocharging system development. The combination of experimental and modelling work gives a good description of all the relevant unsteady processes involved in current diesel engine turbochargers. Some selected results are presented and discussed in the paper.