Meanline Modeling of Radial Inflow Turbine With Twin-Entry Scroll

Abstract

Twin entry turbines are widely used in turbocharging as a means of using the exhaust pulse energy of multi-cylinder engines. For modern engines where high levels of EGR are required, an asymmetric twin-entry turbine has been shown to have considerable advantages. Such turbines require a more developed approach to analysis and design than usual. A meanline model for a radial inflow turbine with twin-entry scroll has been developed. Different total pressures and total temperatures may be specified at each entry. Each volute passage is solved separately from the inlet to the splitter location, where the static pressures of both passages are assumed to be the same. From the volute splitter to the rotor inlet, the two streams mix into one uniform flow following conservation laws of continuity, momentum and energy. Experiments have been conducted on a test stand with a radial turbine with an asymmetric twin-entry scroll, where the inlet conditions can be varied independently for each entry. The test results are compared with the model prediction. A good accuracy of prediction is achieved with a realistic set of modeling coefficients. In the future, insights gained from test data and CFD analysis will be used to develop further the volute mixing model and include explicit partial admission losses in the rotor.

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

“…Fredriksson et al [37] proposed a mean-line model for asymmetrical twin-entry turbine by specifying different flow conditions at each turbine inlet and static pressure at the outlet of a turbine. The methodology is to solve each turbine passage from inlet to the splitter location separately, and from the volute splitter to the rotor inlet, two streams mix into one uniform flow.…”

“…(Equation (31)) in Equation (35) to obtain total temperature and later on in apparent efficiency definition in Equation (5) to estimate the efficiency values similar to the experiments. By continuing the simplification of apparent efficiency (Equation (5)) using the final T MFR x 4t for both branches, it is possible to obtain the final apparent efficiency expressions for both branches as shown in Equations (36) and (37). It is worth noting that the final formulation shown in Equations (36) and (37) are a function of actual efficiencies (not apparent), expansion ratios, and total inlet temperature of both turbine branches to follow the mixed flow corrected approach to obtain the apparent efficiency measured in a gas stand.…”

“…If both branches have the same temperature at the inlet (as could be the case in some gas-stand tests), Equations (36) and (37) are significantly simplified and Equations (38) and (39) are obtained.…”

“…The z j coefficients are the same for the actual apparent efficiencies of two branches (η TE/DV Sh x /LV x and η TE/DV H x /SV x ) as the mixed turbine outlet temperature is common for both apparent efficiency definitions as expressed beforehand. In summary, both apparent efficiency equations (Equations (36) and (37)) have 11 fitting coefficients together and they are globally fitted using a non-linear fitting procedure for a given double entry turbine using the whole data points from the maps of the two branches (all available MFRs). For initial values, the fitting constants of mixed turbine outlet temperature model shown in Table 5 were used.…”

Development and Matching of Double Entry Turbines for the Next Generation of Highly Boosted Gasoline Engines

“…Fredriksson [15] and Hajilouy [16] present a 1D flow simulation model for double entry radial turbines. Furthermore, the simulation results are verified with test bench data.…”