An Experimental and Modelling Strategy for Obtaining Complete Characteristic Maps of Dual-Volute Radial Inflow Turbines

Despite the importance for turbocharged engines of radial inflow dual-volute turbines, their characteristic maps and fully predictive modelling using 1D gas dynamic codes are not well established yet. The complexity of the un-steady flow and the unequal admission of these turbines, when operating with pulses of engine exhaust gas, make them a challenging system. Mainly due to the unequal flow admission, an additional degree of freedom is introduced with respect to well-known single entry vanned or vaneless turbines.

This paper has as a main novelty a simple procedure for characterizing experimentally and elaborating characteristic maps of these turbines with unequal flow conditions. This method of analysis allows easily interpolating within the proposed characteristic maps or conceiving simple models for calculating and extrapolating full performance parameters of dual volute turbines.

Here are also described two innovative 0D mean-line models that require a minimum quantity of experimental data for calibrating both: i.e. the mass flow parameter model and the isentropic efficiency model. Both models are predictive either in partial or unequal flow admission conditions using as inputs: the mass flow ratio between branches; the total temperature ratio between branches; the blade to jet speed ratio in each branch and the pressure ratio in each branch. These five inputs are generally instantaneously provided by 1D gas-dynamics codes. Therefore, the novelty of the model is its ability to be used in quasi-steady way for dual volute turbines performance prediction. This can be done instantaneously when turbines are calculated operating at turbocharged engines under pulsating and unequal flow conditions.