An advanced turbocharger model for the internal combustion engine

Xiao Hu, Purdue University

Abstract

The two significant length scales of the unsteadiness in a turbocharger operation are those associated with engine-driven transients, for instance, engine acceleration and deceleration, and those associated with engine valve events. The engine-driven transients will primarily affect the compressor, because the surge line can be crossed. The engine valve events will primarily affect the turbine, and result in performance that deviates from steady-flow predictions. To address these issues, a lumped parameter model is first developed to show the essential features of the engine-driven transients on the performance of the turbocharger compressor. To improve the predictive tools for the effect of unsteady aerodynamics on these problems, a more advanced model is then developed using an approach based on the solution of the unsteady Euler equations with source terms (EEST). The model is then exercised against data obtained in on-engine studies of pulsed-turbocharged diesel engine turbocharger turbine performance. The EEST model proved able to accurately predict the turbine inlet velocity waveform for a twin-entry turbine under the influence of boundary conditions obtained from experimental data. The model also correctly predicted the shape of the unsteady turbine performance trajectory during a typical valve event. Based on successful validation of the model, an investigation of the design implications of these results in terms of a comparison of true unsteady versus quasi-steady efficiency assumptions is presented. This study demonstrates that the optimum efficiency operating point cannot be achieved with knowledge of only the steady-flow operating characteristics.

Degree

Ph.D.

Advisors

Lawless, Purdue University.

Subject Area

Mechanical engineering

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