Understanding the Twin Scroll Turbine: Flow Similarity

Abstract

The current study investigates the flow conditions of a twin scroll asymmetric turbine. This is motivated by the operating conditions of the turbine at a heavy-duty reciprocating internal combustion engine with exhaust gas recirculation. The flow conditions of the turbine at the engine can be described best with the turbine scroll interaction map. Standard hot gas measurements of a turbocharger turbine are presented and discussed. Due to the strong interaction of the turbine scrolls, further hot gas measurements are performed at partial admission conditions. The turbine inlet conditions are analyzed experimentally, in order to characterize the turbine performance. The turbine scroll pressure ratio is varied, leading to unequal twin turbine admission conditions. The flow behavior is analyzed regarding its ability for further extrapolation. Beyond scroll pressure ratio variations, unequal temperature admission conditions were studied. A way of characterizing the representative turbine inlet temperature, regarding the reduced turbine speed, is presented. The different scroll parameter ratios are evaluated regarding their capability of describing flow similarity under different unequal turbine admission conditions. In this content, turbine scroll Mach number ratio, velocity ratio and mass flow ratio are assessed. Furthermore, a generic representation of the turbine flow conditions at the engine is presented, based on standard turbine performance maps.

A Robust Adiabatic Model for a Quasi-Steady Prediction of Far-Off Non-Measured Performance in Vaneless Twin-Entry or Dual-Volute Radial Turbines

“…When the twin-entry/dual-volute turbine is working in an engine, the inlet conditions are changed in both branches due to the staggered firing orders in the cylinders [40] and corresponding interval opening of the cylinders valves [41]. Accordingly, it was assumed that the power produced by each turbine branch is different [12].…”

Experimental approach for the characterization and performance analysis of twin entry radial-inflow turbines in a gas stand and with different flow admission conditions

“…The operating behavior of twin entry turbines under the pulsating admission of the combustion engine can be divided into flow conditions. Brinkert et al [24] indicate that testing the twin entry turbines with the scroll pressure ratio as only control • Full/equal admission: This operation is possible to measure on the gas stand and occurs when each entry of the turbine is provided the same mass flow rate.…”

Effect of balance valve on an asymmetric twin-scroll turbine for heavy-duty diesel engine

“…10 Turbocharging technologies (two-stage turbocharging, variable geometry turbines (VGTs), symmetric twin-scroll turbines (STSTs), as well as asymmetric twin-scroll turbine (ATST)) apply to the tradeoff of the NO x emission and fuel consumption. 11 Two-stage turbocharging exhibits sufficiently high air fuel ratio and robust EGR drive capability, 12,13 whereas for the architecture of two-stage turbos and the connection pipes, the engine requires a larger space for installation. 14 VGT can significantly facilitate quick transient response, 15,16 wide turbine flow range and variable EGR drive capability 17,18 by regulating the gap of nozzle, whereas the nozzle and electronic actuator are relatively sophisticated and expensive.…”