Abstract
The current investigation describes in detail a mass flow oriented model for extrapolation of reduced mass flow and adiabatic efficiency of double entry radial inflow turbines under any unequal and partial flow admission conditions. The model is based on a novel approach, which proposes assimilating double entry turbines to two variable geometry turbines (VGTs) using the mass flow ratio ( MFR ) between the two entries as the discriminating parameter. With such an innovative approach, the model can extrapolate performance parameters to non-measured MFR s, blade-to-jet speed ratios, and reduced speeds. Therefore, the model can be used in a quasi-steady method for predicting double entry turbines performance instantaneously. The model was validated against a dataset from two different double entry turbine types: a twin-entry symmetrical turbine and a dual-volute asymmetrical turbine. Both were tested under steady flow conditions. The proposed model showed accurate results and a coherent set of fitting parameters with physical meaning, as discussed in this paper. The obtained parameters showed very similar figures for the aforementioned turbine types, which allows concluding that they are an adequate set of values for initializing the fitting procedure of any type of double entry radial turbine.
Highlights
Along with the growing interest in global environmental issues, the automotive manufacturers are facing increasing challenges to reduce the gaseous emissions [1] coming from internal combustion engines as well as to meet the strict emission legislation year by year [2]
The results demonstrate that the mass flow parameters are well predicted for full and partial admission flow conditions and efficiencies were over-predicted in the case of lower turbo speeds and pressure ratios
If the error is examined against MFRx parameter and turbine reduced speed, as shown in Figure 22a,b, respectively, the error shows a comparatively parabolic trend with reduced turbine speed and the error decreases from full admission to partial admission conditions
Summary
Along with the growing interest in global environmental issues, the automotive manufacturers are facing increasing challenges to reduce the gaseous emissions [1] coming from internal combustion engines as well as to meet the strict emission legislation year by year [2]. The comparison of performance parameters between these two types of double entry turbines has been extensively discussed since Pischinger and Wunsche [10] until more recently, such as in the work by Romagnoli et al [11] Both turbines (twin-entry/dual-volute) have different geometries due to their designs, merely by the type of flow division, as explained below:. In previous work [12], a detailed analysis of experimental data and how to process the performance parameters of twin-entry radial-inflow turbine was shown for different steady flow admission conditions. Newton et al [35] proposed a method for extrapolating from the full admission map of the dual-volute turbine to obtain the unequal admission performances of both efficiency and mass flow parameters. The current paper demonstrates the methodology for modeling both twin-entry and dual-volute turbines to extrapolate the performance maps into off-design conditions for all the flow admission conditions.
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