Attempt to correlate simulations and measurements of turbine performance under pulsating flows for automotive turbochargers

Abstract

The paper attempts to correlate simulations and measurements of turbine performance under pulsating flows for automotive turbochargers. Under real automotive powertrain conditions, turbochargers are subjected to pulsating flows, due to the motion of the engine’s valves. Experiments on a purpose-built 2.2 L diesel engine gas-stand have allowed the quantification of unsteady pulsating turbine performance. Temperature, pressure and mass flow measurements are fundamental for the characterisation of turbine performance. An adequate sampling frequency of the instruments and acquisition rates are highly important for the quantification of unsteady turbomachine performance. In the absence of fast, responsive sensors for monitoring mass flow and temperature, however, appropriate considerations would have to be taken into account when making estimates of turbine performance under pulsating flows. A 1D model of the engine gas-stand has been developed and validated against experimental data. A hybrid unsteady/quasi-steady turbine model has been adopted to identify unsteadiness at the turbine inlet and outlet. To evaluate isentropic turbine efficiency and reduce the influence of external heat transfer upon measurements, the turbine inlet temperature has been measured experimentally in the vicinity of the turbine rotor in the inlet section, upstream of the turbine tongue. The hybrid unsteady/quasi-steady turbine model considers the presence of unsteady flows in the turbine inlet and outlet, leaving the rest of the turbine to react quasi-steadily. Virtual sensors and thermocouples have been implemented in a 1D model to correlate experimental time-averaged temperature measurements.

Numerical Analysis of Engine Exhaust Flow Parameters for Resolving Pre-Turbine Pulsating Flow Enthalpy and Exergy

“…However, these simulation-based approaches highly depend on the accuracy of engine models and the boundary conditions in use. Another approach for characterizing instantaneous flow energy is to integrate direct measurement with ICE flow simulation or estimation [32]. For instance, the flow exergy of exhaust pulsation is characterized, respectively, during blowdown and displacement phases of exhaust processes by Mahabadipour et al [15,33].…”

Dimensionless quantification of small radial turbine transient performance

“…The rotational speed of the shaft v shaft is governed by equation (3), using also the compressor power _ W c and the inertia of the shaft I shaft . The turbine model is linked to a quasi-steady compressor map via a simple shaft model.…”

“…1 The pulsating character of the system due to the reciprocating movement of the piston and opening and closure of the valves is a major underlying cause of the unsteady behaviour of the flow. 2,3…”

“…1 The pulsating character of the system due to the reciprocating movement of the piston and opening and closure of the valves is a major underlying cause of the unsteady behaviour of the flow. 2,3 Both 1D and 3D methodologies have been used to analyse turbocharger transient performance, complemented by specialist experimental techniques to capture and measure performance characteristics under these conditions. In the research of Benson 4 and Wallace and colleagues, 5,6 deviations were found by using quasisteady models to predict turbine averaged performance under unsteady flow.…”

Radial turbine sound and noise characterisation with acoustic transfer matrices by means of fast one-dimensional models

“…The volute can be discretised as a one-dimensional tapered duct with a lateral connection to the vanes of the stator or the vaneless space before the rotor, depending on the turbine stator characteristics. 21,22,17 It is also worth mentioning the difficulties in correlating turbine power with experiments as found in Avola et al 23…”