Experimental characterization and mean line modelling of twin-entry and dual-volute turbines working under different admission conditions with steady flow

Abstract

Despite the importance of radial in-flow twin-entry and dual-volute turbines for turbocharged engines, 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 to well-known single entry vanned or vaneless turbines. Moreover, the addition of the second inlet to the turbine volute brings extra complexity in determining the steady-state turbine performance parameters under unequal admission conditions. This thesis has a main novelty, which is a simple procedure for characterizing experimentally and elaborating characteristic maps of these turbines with unequal flow conditions. This method of analysis allows easy interpolating within the proposed distinctive maps or simple convincing models for calculating and extrapolating full performance parameters of twin-entry and dual-volute turbines.Finally, the models have been fully validated by coupling them with one-dimensional modelling software and simulated both the gas stand and the whole engine measured points. On the one hand, the validation results from the gas stand simulation show that the model can predict well all steady flow variables. On the other hand, the validation results from the whole engine simulation show that the model is able to produce all the full load engine variables like air mass flow and brake torque in a reasonable degree of agreement with the experimental data.

Evaluation of a Double-Entry Turbine Model Coupled With a One-Dimensional Calibrated Engine Model at Engine Full Load Curves

“…Aforementioned, the SCV opened tests were performed with totally opened valve, and accordingly, in the simulation, the valve is fixed to 100% for all engine speeds as shown in Figure 12A. As discussed by Samala (2020), the flow passing from long to short and vice versa for the same operating point in the turbine is different. Due to the pressure drop across the SCV section is not the same in each flow direction.…”

“…Whereas, reduced mass flow is considered at turbine tongue outlet (station A). In order to compare the instantaneous traces, they are plotted with the different steady-state admission extrapolated curves (counters) of every branch obtained from the CMT-DETCM model (Samala, 2020). It should be noted that, when MFR is increasing, the mass flow conditions in the long volute branch increases and short volute branch decreases.…”

“…Besides, when SCV opens, flow from one branch to another can communicate depending on the pulse in each branch. In order to have the same in the simulations, the SCV discharge coefficient model, which is developed in the previous work (Samala, 2020), has been used. The details of the model can be found in Annex.…”

“…The data was acquired with more accurate instrumentation, placing several thermocouples at the inlet and outlet of the turbine for temperature measurement. More details about this work can be found in (Samala, 2020). It is worth highlighting that the internal and external heat transfer models used in this work are previously developed and calibrated for a single/VGT turbocharger.…”

“…However, in this work, the heat transfer effects in doubleentry turbines were not the primary objective. Therefore, the first approximation of heat transfer in double-entry turbochargers was calculated in a similar way to the single entry turbocharger thermal model based on the electric analogy as described in (Samala, 2020).…”