Thermal effect on cavitation characteristics of a hydraulic torque converter

Abstract

The performance of torque converters, which use hydraulic oil as the working medium to transmit power, are severely affected by the operating temperature because various oil properties, such as viscosity, density and saturated pressure, vary drastically with temperature change. To study the thermal effect on the cavitation characteristics of viscous oil, we developed a full flow passage geometry and computational fluid dynamics (CFD) model with cavitation based on the finite volume method (FVM) to predict and analyze cavitation behavior and thermal effect in a torque converter. The results show that the critical cavitation number and critical cavitation temperature of the tested torque converter are 9.2 and 30 °C, respectively, and increasing the temperature reduces the cavitation number and induces the generation and intensification of cavitation. Besides, although higher temperature improves the transmission efficiency and capacity constant of the torque converter, it greatly magnifies the influence of cavitation on the hydrodynamic performance. In severe cases, it reduces the hydraulic performance by 9.3% and the flow velocity by 11.8% at 100 °C. Meanwhile, the cavitation flow field and the configuration of cavitation are also greatly affected by temperature. About 11.9% of the surface of the stator blade was covered by cavitation bubbles with the vapor volume fraction of 88.1% at 100 °C. Moreover, 30–60 °C is the optimum operating temperature range in terms of cavitations effect with no pronounced cavitation occurrence or that the cavitation degree is too weak to affect the performance in the mentioned temperature range.

KEYWORDS:

• Cavitation flow
• interphase mass transfer
• thermal effect
• torque converter
• viscous oil

Authors’ contributions

The author’ contributions are as follows: Meng Guo performed the data analyses, designed and performed the experiments, and wrote the manuscript; Cheng Liu and Qingdong Yan contributed significantly to analysis and manuscript preparation; Jiahua Zhang and Shiqi Liu contributed to the conception of the study; Boo Cheong Khoo helped perform the analysis with constructive discussions.

Availability of data and materials

The datasets supporting the conclusions of this article are included within the article.

Conflict of interest

The authors declare that they have no conflict of interest.

Ethics approval and consent to participate

This article does not contain any studies with human participants or animals performed by any of the authors.

Data availability

The data that support the findings of this study are available from the corresponding author upon reasonable request.

Additional information

Funding

Supported by National Natural Science Foundation of China (NSFC) through Grant No. 51475041 and 51805027, Beijing Institute of Technology Research Fund Program for young Scholars (3030011181804), and Vehicular Transmission Key Laboratory Fund (6142213180407). The first author thanks the China Scholarship Council (CSC) for financial support (202006030045).