Impact of Turbocharger Non-Adiabatic Operation on Engine Volumetric Efficiency and Turbo Lag

Abstract

Turbocharger performance significantly affects the thermodynamic properties of the working fluid at engine boundaries and hence engine performance. Heat transfer takes place under all circumstances during turbocharger operation. This heat transfer affects the power produced by the turbine, the power consumed by the compressor, and the engine volumetric efficiency. Therefore, non-adiabatic turbocharger performance can restrict the engine charging process and hence engine performance. The present research work investigates the effect of turbocharger non-adiabatic performance on the engine charging process and turbo lag. Two passenger car turbochargers are experimentally and theoretically investigated. The effect of turbine casing insulation is also explored. The present investigation shows that thermal energy is transferred to the compressor under all circumstances. At high rotational speeds, thermal energy is first transferred to the compressor and latter from the compressor to the ambient. Therefore, the compressor appears to be “adiabatic” at high rotational speeds despite the complex heat transfer processes inside the compressor. A tangible effect of turbocharger non-adiabatic performance on the charging process is identified at turbocharger part load operation. The turbine power is the most affected operating parameter, followed by the engine volumetric efficiency. Insulating the turbine is recommended for reducing the turbine size and the turbo lag.

Impact of heat transfer on the performance of micro gas turbines

“…Heat fluxes between the different bodies, as well as heat fluxes between the working fluids and bodies are taken into account. Several studies on heat transfer inside automotive turbochargers of similar size have demonstrated that this approach provides adequate results [16,17,[19][20][21][22][24][25][26].…”

“…Components that are in close proximity can operate at significantly different temperatures, resulting in heat fluxes of the same magnitude as the energy involved in compression and expansion [16]. Research on turbochargers of similar size as the micro turbines investigated in this paper shows that the heat flux from the turbine to the compressor leads to a drop in turbine power of around 10% at design point conditions and up to 20 or even 45% at low rpms [17][18][19]. While the power delivered by the turbine drops, the compressor consumes more power because of additional reheat losses [20,21].…”

“…It also calculates the non-adiabatic flow in the radial compressor and turbine. A lumped capacitance network that consists of conventional correlations employed extensively in turbocharger heat transfer research [16,17,[19][20][21][22][24][25][26], is used here to predict the flow and heat transfer in complete micro turbines of different size, material, and configuration. The originality of the paper resides in the application of this type of heat transfer analysis to an entire micro turbine and in the comparison of two different configurations, thereby, for the first time, quantifying the impact of configuration selection on micro turbine performance.…”

Solvent Based Slurry Functional Graded Thermal Barrier Coating for Application in Automotive Turbocharger Turbine Volute Casing

“…Turbocharger used the extracted energy of the engine hot exhaust gas by expanding it through the turbine which in turn drives the compressor by a shaft and compress ambient air into the engine cylinder via the intake manifold. However, studies have shown that thermal energy transfer from the turbocharger turbine seriously affects the turbine power and in turn affects the overall turbocharger performance [4][5][6]. On the other hand, experimental data from several studies have shown that insulating the turbocharger turbine can significantly improve the non-adiabatic performance of the turbocharger and hence the overall engine efficiency [4,7,8].…”

Importance of Heat Transfer Phenomena in Small Turbochargers for Passenger Car Applications

“…In addition experimental instrumentation will be easier and so the validation of the model. Models proposed by Bohn [19] and Shaaban [15,20] make a distinction between the heat transfer that takes place after and before the rotor. With this level of detail, difficulties in instrumentation for experimental characterization increases.…”