This work presents the dynamic modeling of an automotive turbocharger in a hot gas test stand. The objective is to develop a methodology to determine the main turbocharger dynamic properties as moment of inertia, response time, static gain constant, frequency gain amplitude and phase shift. The turbocharger used is the Master Power APL-240 set. The moment of inertia is obtained through the deceleration curve from an instantaneous fuel cut-off in the combustion chamber. The response time and static gain constant, as well the frequency gain amplitude and phase shift curves in function of a signal frequency, are obtained through a step variation. The turbocharger is modeled as a first order system. It is also presented a turbocharger sine excitation by the combustion chamber, generating a rotational speed sine signal output that simulates an engine intermittent acceleration. The rotational speed signal frequency gain and phase shift are compared to the values obtained in the step curves. The rotational speed frequency gain amplitude and phase shift modeled through the step test presents deviation of 16% and 13%, respectively, from the values from sine test.
This work presents the experimental methodology used in turbochargers tests using a hot gas test stand. The test consists in recording the characteristic curves of the turbochargers, known as flow maps or performance maps. A tubular combustion chamber, designed to operate burning gaseous fuels, is used to drive the set. By using a hot gas generator it’s possible to simulate the real operational condition of the turbine. The experimental configuration allows reproducing the self-sustained turbocharger operation. The test stand instrumentation is based on virtual instrumentation, where acquisition of the sensors and control are made by computer. For the performance maps obtainment, the experimental data are treated through an empirical model based in a quadratic equation involving two variables, mass flow rate and rotational speed. The results present the performance and efficiency maps for the APL-240 Master Power turbocharger, used in commercial heavy trucks. With the results is made a comparison between the experimental maps with the maps gotten through a semi-empirical model based in modified Euler equation. The maximum deviation for compressor and turbine semi-empirical pressure ratios are respectively 8% and 14% in relation to the experimental data.
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