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 that the heat transfer coefficients required were ultimately found to be mostly independent of the turbochargers tested.

Theoretical and experimental study of mechanical losses in automotive turbochargers

“…With these two actions, the turbocharger behavior is expected to be near adiabatic [14,15]. In this way, the energy absorbed by the lubrication oil will mainly come from the heat generated by friction, i.e.…”

Evaluation of different heat transfer conditions on an automotive turbocharger

“…Baines et al [3] carried out the same experiment as in those previous publications [1,2], but in their work three different turbochargers were run over a range of turbine inlet temperatures and external ventilation rates. The heat transfer coefficients required in their onedimensional heat transfer model were found to be mostly independent of the turbochargers tested [3].…”

“…The study of heat transfer in turbochargers has become an important aspect of turbocharged engine development, and there has been growing interest in the heat transfer analysis of automotive turbochargers [1,2,3,4,5,6,7]. Other issues in regards to heat transfer in turbochargers are also important, including the effect of heat transfer on the turbocharger performance [7,8,9], turbocharger performance correction for non-adiabatic conditions [9], and turbocharged engine simulations [10].…”

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

“…As the heat transfer only occurs after the impeller, the mechanical power measured in adiabatic conditions will be the same whatever will be turbine inlet temperature. The model proposed by Baines et al [17] is only focused in heat transfer phenomena of the turbocharger based on convection process. Using the same argument of comparing exposed areas, in the turbine the bigger heat transfer will take place up to turbine tongue and at volute and so before extracting power in the rotor.…”

“…If diabatic but One of the discrepancies between proposed one-dimensional models in the literature to characterize heat transfer phenomena in turbochargers is whether the heat flux is removed from the system after or before the extraction of power, or even a combination of both possibilities. Baines et al [17] assumes that the heat transferred from the compressed air to the surroundings and to the rest of the turbocharger unit occurs after the compression process, placed in the diffuser and the volute. This explanation is justified by the larger surface exposed to the air in this place compared to the impeller area.…”