A numerical model is proposed to calculate both the contact pressure and the friction torque (FT) of the friction components considering the spline friction in a wet multidisc clutch, which is verified by the bench test. The results indicate that the spline friction of components is an important factor causing the axial attenuation of contact pressure on friction pairs. As the applied pressure increases, the attenuation amplitude of contact pressure increases gradually. In addition, the average single-pair FT decreases with the increasing number of friction pairs, thus leading to the decrease of the growth rate of total FT. Therefore, when the number of friction pairs reaches a certain number, it is not reliable to obtain a good torque enhancement, indicating that the effect of spline friction needs to be weakened to reduce the attenuation of contact pressure.
This paper investigates the influence of three-dimensional smooth humps with varying deflection angles (φ) on the linear stability of streamwise vortices over a yawed cone with a 7° half-angle at a 6° angle-of-attack, free-stream Mach number of 6, and unit Reynolds number of 1.0×107/m. The steady laminar flow is obtained using direct numerical simulations. The eN method based on global stability theory is used to predict the transition location of the streamwise vortices along the centerline on the leeward side of the cone. The results reveal that φ plays a significant role in the outward vortex generation location, with smaller values of φ effectively delaying the outward vortex generation. Moreover, there is a qualitative relationship between the instability of the streamwise vortices and the inward/outward vortex structure characteristics of the base flow over a yawed cone. Namely, the transition delay effect of the streamwise vortices is proportional to the delay in the generation location of the outward vortex, which provides insights into the control of the transition induced by streamwise vortices. In particular, the configuration based on a hump with φ=9° and a height of 0.57 times the local boundary layer thickness delays the transition by approximately 38.2% at the critical N-factor (Ntr=12.5) without significantly increasing the instability of the inner mode.
It is of great significance to study the friction characteristics in the process of slippage and friction of the wet clutch for optimizing vehicle start, improving vehicle driving comfort and prolonging the service life of the clutch. Based on the test data of wet multi-plate clutch under braking condition in SAE#2 test bench friction torque test, we analyze the influence of rotate speed and average pressure on the friction torque through the comparison of friction torque under two friction pairs. The results show that in the case of sufficient lubricating oil flow, the attenuation of multiple pairs of friction plates has nothing to do with the proportion of the groove area of friction plates. Friction torque attenuation will occur under any groove area, but different groove areas will affect the rotate speed and average pressure of this phenomenon. In general, the frictional torque attenuation of wet multi-plate clutch gradually increases with the increase of relative speed and decreases with the increase of average surface pressure.
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