In our previous paper, the steady-state test results of a mixed flow turbine with variable nozzle vanes for a turbocharger are reported. In this paper, the transient response of the same mixed flow...

Transient performance of the mixed flow and radial flow variable geometry turbines for an automotive turbocharger

A specific design of mixed flow variable geometry turbine for an automotive sub 1.5 litre diesel engine turbocharger is proposed in this paper. An experimental set up is developed for measuring the steady state and transient response behaviour of the turbine at different nozzle vane opening positions. The rotor speed, pressure and temperature before and after the turbine are measured and recorded using high frequency data logging system. The steady state performance for mass flow, efficiency, velocity ratio, specific speed and the transient response behaviour of the mixed flow variable geometry turbine (MFVGT) are compared against the same parameters of a radial flow variable geometry turbine (RFVGT) of similar dimensions. Typical result indicates that the transient response of the MFVGT is faster by about 350 milliseconds than the radial at turbine inlet pressure of 0.2 bar (g).Copyright © 2015 by ASME

Transient Response of Mixed Flow Variable Geometry Turbine for a Turbocharger

The turbine, an enabling component of turbochargers, is a seat of highly complex unsteady flow as well as varying gas compositions between diesel and gasoline engines. Thus, it is necessary to take into account different physical models when simulating such turbines. Researchers have often considered the turbine working gas as air, which may not lead to an accurate prediction of actual turbine characteristics. In the present work, the effect of the working gas on the performance of turbocharger turbines as well as on the turbo lag was investigated through a set of numerical simulations for six wastegate opening degrees from 0% up to 100% and under a wide range of the flow pulse frequency ranging from 33.33 up to 166.66 Hz. Four working fluids were involved in this study which are the gasoline burnt gas, diesel burnt gas, air with like gasoline engine waves, and air with like diesel engine waves. The performance of the turbine and its responsiveness quantified as the time lag with burnt gases from both diesel and gasoline engines were compared to those with air. Results showed totally deviated unsteady performance characteristics compared to the turbine working with air. Results also confirmed that considering the working fluid as air may not lead to a fair representation of the actual turbine performance characteristics. The findings of this work put emphasis on the importance of the gas composition when modeling such turbines by engineers especially during the design process where a good turbocharger-engine match has to be met.

Analysis of performance and time lag of turbocharger turbines fed with gasoline and diesel burnt gases and air under pulsating flow conditions

Influence of Blade-Flow Interactions on Flow Behaviours and Blade Loading of an Automotive Mixed-Flow Turbine

A new design of a mixed flow variable geometry turbine is developed for the turbocharger used in diesel engines having the cylinder capacity from 1.0 to 1.5 L. An equivalent size radial flow variab...

K Ramesh

Papers

A comparative study of the performance of the mixed flow and radial flow variable geometry turbines for an automotive turbocharger