Numerical prediction and measurement of pressure drop and heat transfer in a water‐cooled hollow‐shaft rotor for a traction motor application

Abstract

This article addresses the rotating effect on the pressure loss and heat transfer coefficient (HTC) of a hollow‐shaft rotor cooling system for an automotive traction motor. Firstly, a numerical model based on computational fluid dynamics (CFD) was established to fully understand the mechanism of rotational flow patterns. Experiments were then performed to measure and compare heat exchange and pressure loss between rotating and stationary conditions with the assistance of an analytical thermal model. Finally, trends of pressure drop and HTC at various rotational rates were explained in detail. Based on CFD simulations and experimental prototype testing, two opposite effects: boosting or diminishing on pressure drop and heat transfer due to rotation have been identified. Moreover, the rotation can significantly improve the overall HTC and pressure loss of an axial turbulent flow. As a result, a significant drop in terms of rotor temperature is identified for an automotive traction motor when such a rotor cooling system is implemented.

Experiment and Simulation Study on the Cooling Performance of Oil-Cooling PMSM with Hairpin Winding

“…The inlet flow is the mass flow, and the pressure outlet is located at the bottom. Because the oil flow is laminar, the standard k-ε method and the volume of fluid (VOF) model are used in this paper, and the equation of standard k-ε is expressed as follows [19]:…”

“…According to the requirements of the wall function, the y+ needs to meet 11.5 < y+ < 200. The y+ is the dimensionless wall distance [19], and it can be expressed as in Formula (4). After detailed meshing, the y+ at the surface of the end winding in this paper is 13, which meets the mesh requirements and the number of grids is 620,000.…”

“…The analysis methods of motor cooling systems are divided into two methods: the experimental method and the numerical simulation method [14][15][16]. Whether the motor cooling system is water-cooled, air-cooled or oil-cooled, the convective heat transfer area (CHTA), the average convective heat transfer coefficient (CHTC) and the convective thermal resistance (CTR) are the main standards for cooling performance [17][18][19][20]. Xintong Zhang et al [17] proposed the coupling method of computational fluid dynamics (CFD) and lumped parameter thermal network (LTPN) to calculate the CHTC of an air-cooling motor.…”

“…Peixin Liang et al [18] determined the cooling performance of the circumferential water jacket and axial water jacket by comparing the CHTC. Yaohui Gai et al [19] calculated the CHTC in the hollow shaft cooling system of the rotor with various speeds. F. Zhang et al [20] established the LPTN of the oil-cooling end winding, in which the CHTC and CTR are important parameters related to temperature rise.…”

A fast calculation method of transient hot spot temperature for the design of dry‐type on‐board transformers

“…Computational fluid dynamics, a numerical calculation method, combines the finite volume method with the principles of heat transfer to perform accurate HST calculations. Scholars widely recognise CFD's accuracy in transformer thermal modelling research, and simulation results can be equated to actual temperature rise experimental results [18][19][20][21][22][23][24][25][26]. For example, Ref.…”