Turbocharger turbine performance under unsteady flow - a review of experimental results and proposed models

The conditions encountered by turbochargers turbines when they are fitted to engines are usually those of pulsating flow conditions, but the performance of these turbines is normally measured under steady flow conditions. This can mean that a turbine which performs well on the test bed does not live up to expectations in the application. A significant amount of work has been undertaken to assess the effect of pulsating flows on turbines, and this paper will summarise some of the recent work. It is concluded that turbines do not behave :in a quasisteady manner under unsteady flow conditions, but that the results are also affected by the measurement techniques. A method of simulating unsteady flow characteristics, which is used by a number of researchers, is described.