Temperature regime and energy capacity of bus friction clutches in urban operating conditions

Abstract

Friction clutches (FC) of motor vehicles operate under significant thermal and dynamic loads, especially in urban driving conditions characterized by frequent starts and stops. The reliability and service life of FC largely depend on the thermal state of friction pairs, which is influenced by the thermophysical properties of materials, clutch design, and heat transfer conditions. Existing methods for calculating and designing FC often do not sufficiently consider the interrelated dynamic, thermal, and frictional processes occurring during operation, which leads to a reduction in their service life and operational efficiency. Goal. The purpose of the work is to study the temperature regime and energy consumption of bus friction clutches in the urban operating cycle. Methodology. The temperature distribution in FC elements was described using the differential heat conduction equation in a cylindrical coordinate system with corresponding initial and boundary conditions. Due to the complexity of the clutch geometry and operating modes, a three-dimensional thermal model based on thermal resistance grids was developed. The slipping work of the friction clutch during operation of the Etalon bus under SAE-regulated driving modes was calculated to determine the boundary conditions of the second kind (heat generation). Boundary conditions of the third kind (heat transfer) were also substantiated. Numerical simulation was performed using the Fourier-2 x, y, z software package. Results. The study determined the temperature distribution in the friction pairs of the clutch under urban operating conditions and established the influence of heat transfer coefficients on the thermal state and energy consumption of the friction clutch. It was shown that changes in heat transfer conditions significantly affect the temperature indicators and operational characteristics of FC friction pairs. Originality. A three-dimensional thermal model of a bus friction clutch operating in an urban cycle was developed, taking into account the interrelated thermal and frictional processes as well as variable heat transfer conditions. The proposed approach allows a more accurate assessment of the thermal behavior and energy capacity of FC under real operating conditions. Practical value. The obtained results can be used in the design and optimization of bus friction clutches, improvement of their thermal reliability and durability, as well as in the selection of effective operating modes and materials for friction pairs.