Abstract
In turbocharger design, the accurate determination of thermally induced stresses is of particular importance for life cycle predictions. An accurate, transient, thermal finite element analysis (FEA) of turbocharger components requires transient conjugate heat transfer (CHT) analysis. However, due to the vastly different timescales of the heat transfer mechanisms in fluid and in solid states, unsteady CHT simulations are burdened by high computational costs. Hence, for design iterations, uncoupled CFD and FEA approaches are needed. The quality of the uncoupled thermal analysis depends on the local heat transfer coefficients (HTC) and reference fluid temperatures. In this paper, multiple CFD-FEA methods known from literature are implemented in a numerical model of a turbocharger. In order to describe the heat transfer and thermal boundary layer of the fluid, different definitions of heat transfer coefficients and reference fluid temperatures are investigated with regard to calculation time and accuracy. For the transient simulation of a long heating process, the combination of the CFD-FEA methods with the interpolation FEA approach is examined. Additionally, a structural-mechanical analysis is conducted. The results of the developed methods are evaluated against experimental data and the results of the extensive unsteady CHT numerical method.
Highlights
The growing competition, challenging requirements for an efficiency, and rigorous restrictions on exhaust emissions in a transportation sector are forcing the companies involved to deploy time and cost improved design procedures to increase the quality of individual vehicle components
Two main calculation approaches to transient fluid/solid heat transfer are described in literature: conjugate heat transfer (CHT) methods and uncoupled CFD-finite element analysis (FEA) methods
That was followed by the adiabatic Y-plus (AAY) method, this simulation approach resulted in relatively higher relative root mean square (RRMS) values at turbine wheel (TW)—under 7% for calculations with y+ equal to 60 and 250
Summary
The growing competition, challenging requirements for an efficiency, and rigorous restrictions on exhaust emissions in a transportation sector are forcing the companies involved to deploy time and cost improved design procedures to increase the quality of individual vehicle components. The further development of turbochargers, which significantly enhance the performance of the whole engine, perfectly conforms with the leading trends in automotive industry. In pursuit of improved engine performance, exhaust gas temperatures are being continuously increased. A high temperature of a flow at the inlet to the turbine, together with the transient operating conditions, unavoidably leads to high thermal stresses in the turbine housing and turbine wheel [1]. In order to account for the thermal stresses as part of the standard design process, fast calculation methods are required to determine transient temperature fields in a turbocharger.
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