The Analysis of Heat Transfer in Automotive Turbochargers

Abstract

Heat transfers in an automotive turbocharger comprise significant energy flows, but are rarely measured or accounted for in any turbocharger performance assessment. Existing measurements suggest that the difference in turbine efficiency calculated in the conventional way, by means of the fluid temperature change, under adiabatic conditions differs considerably from the usual diabatic test conditions, particularly at low turbine pressure ratio. In the work described in this paper, three commercial turbochargers were extensively instrumented with thermocouples on all accessible external and internal surfaces in order to make comprehensive temperature surveys. The turbochargers were run at ranges of turbine inlet temperature and external ventilation. Adiabatic tests were also carried out to serve as a reference condition. Based on the temperature measurements, the internal heat fluxes from the turbine gas to the turbocharger structure and from there to the lubricating oil and the compressor, and the external heat fluxes to the environment were calculated. A one-dimensional heat transfer network model of the turbocharger was demonstrated to be able to simulate the heat fluxes to good accuracy, and the heat transfer coefficients required were ultimately found to be mostly independent of the turbochargers tested.

Heat transfer in turbocharger turbines under steady, pulsating and transient conditions

“…Cormerais et al (2006) presented the most extreme changes in operating conditions, varying turbine inlet temperature from 50°C to 500°C with a thermally insulated turbocharger and observed up to 15% points change in apparent compressor efficiency. Baines et al (2010) measured losses of 700 W at 250°C turbine inlet gas temperature (TIT) which is considerably lower than the 2.7 kW measured for a similar turbocharger by Aghaali and Angstrom with turbine inlet temperatures ranging 620-850°C (Aghaali and Angstrom, 2013). Baines et al (2010) also estimated heat transfer to ambient as 25% of total turbine heat transfer, however at 700°C TIT, where temperature gradients to ambient were much higher, Shaaban (2004) estimated this at 70%.…”

“…Baines et al (2010) measured losses of 700 W at 250°C turbine inlet gas temperature (TIT) which is considerably lower than the 2.7 kW measured for a similar turbocharger by Aghaali and Angstrom with turbine inlet temperatures ranging 620-850°C (Aghaali and Angstrom, 2013). Baines et al (2010) also estimated heat transfer to ambient as 25% of total turbine heat transfer, however at 700°C TIT, where temperature gradients to ambient were much higher, Shaaban (2004) estimated this at 70%.…”

“…A simplified heat transfer model was used based on similar approaches found in the literature (Cormerais et al, 2006(Cormerais et al, , 2009Shaaban, 2004;Baines et al, 2010;Olmeda et al, 2013;Romagnoli and Martinez-Botas, 2012) (Fig. 2).…”

“…The first studies focussed on quantifying the effects of heat transfer on steady flow gas stands by comparing the work transfers that would be measured based on temperature changes for different turbine inlet temperatures (Chesse et al, 2011;Cormerais et al, 2006;Shaaban, 2004;Serrano et al, 2007;Baines et al, 2010;Aghaali and Angstrom, 2013). Cormerais et al (2006) presented the most extreme changes in operating conditions, varying turbine inlet temperature from 50°C to 500°C with a thermally insulated turbocharger and observed up to 15% points change in apparent compressor efficiency.…”

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

“…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].…”