A Three-Dimensional Conjugate Heat Transfer Model of a Turbocharger Turbine Housing
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RESEARCH PAPER
A Three‑Dimensional Conjugate Heat Transfer Model of a Turbocharger Turbine Housing Sh. Alaviyoun1 · M. Ziabasharhagh1 · A. Mohammadi2 Received: 25 December 2019 / Accepted: 26 September 2020 © Shiraz University 2020
Abstract The turbine housing is subjected to thermal load which is essential to be taken into account in the design process. In this paper, a three-dimensional conjugate heat transfer simulation of a wastegated turbine housing has been performed. The model has been validated with data from thermocouple measurements and thermography pictures. Moreover, the effect of ventilation speed on temperature distribution of turbine housing is investigated. As the air velocity increases from 8 to 20 m/s, the turbine housing temperature decreases about 114 K. The wastegate valve could be gradually opened by stepping-up the speed of the engine. The ratio of wastegate flow to the turbine housing gas flow is near 30% for the high rotational speeds and loads. Therefore, the exhaust gas passes through the wastegate channel and the velocity reaches 538 m/s for 2° opening of the wastegate valve. Simulation results show that 1.5 mm decreasing the wall thickness of the volute wall causes 30 Kelvin higher temperature in the turbine housing wall. According to the results of the simulation, the impeller specific work of high gas flow condition was observed to be up to 2.5 times of low mass flow rate operation. Furthermore, the specific amount of gas heat transfer at a closed wastegate condition is significantly higher in comparison to the high gas flow rate and open wastegate condition. In addition, the results show that at low speed and closed wastegate condition, 15 percent of the specific heat transfer occurs before the turbine wheel. Keywords Turbocharger · Conjugate heat transfer · Turbine housing · Wastegate · Thermography List of Symbols CP Constant pressure heat capacity (J/kg K) h Enthalpy (J/kg) m Mass (kg) P Pressure (Pa) Q Heat transfer (J) S Source term T Temperature (K) t Time (s) V Flow velocity vector (m/s) Y+ Dimensionless wall distance Greek Symbols ƙ Thermal conductivity (W/m K) ρ Density (kg/m3)
* M. Ziabasharhagh [email protected] 1
Department of Mechanical Engineering, K.N. Toosi University of Technology, Tehran, Iran
Department of Mechanical Engineering, Shahid Rajaee Teacher Training University, Tehran, Iran
2
τ Shear stress tensor (Pa) Ω Rotational speed (rad/s)
1 Introduction Turbocharging is an important technology for the downsizing of internal combustion engines, which leads to lower specific fuel consumption (SFC). The turbocharger consists of a compressor and an exhaust gas-driven turbine. The exhaust gas expands in the turbine and generates the kinetic energy which drives the rotor shaft and compresses the air using the compressor. Heat transfer occurs due to the high-temperature difference between the turbine and the other components. However, it is important to limit the heat transfer from the turbine gases to the lubricating oil, because the extreme
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