2018-01-0387 Published 0 3 Apr 2018 © 2018 SAE International. All Rights Reserved.Drag and Cooling Characteristics of Circular Pin- Fin Groove Pattern of a Multi-plate Clutch Pack Using CFD Bangalore Lingaraj Yashwanth Simerics Inc. Dinh Ngo and Debera Schroeder Allison Transmission Inc.Brian Hopson Force Control Industries Inc.De Ming Wang Simerics Inc. Citation: Yashwanth, B.L., Ngo, D., Schroeder, D., Hopson, B. et al., “Drag and Cooling Characteristics of Circular Pin-Fin Groove Pattern of a Multi-plate Clutch Pack Using CFD,” SAE Technical Paper 2018-01-0387, 2018, doi:10.4271/2018-01-0387. Abstract A numerical analysis of drag torque and cooling char - acteristics of a Multi-plate clutch pack with a circular pin fin shaped groove pattern is presented in this article. Simulations were performed using Simerics MP® platform to investigate the drag torque and heat transfer under various operating conditions. The performance characteristics of the circular pattern were later compared with various designs from the literature. Some of the groove pattern designs considered have been commonly used in transmission systems and some are from the patent literature. This study compares each design and later proposes the most efficient, that has the least drag and highest heat transfer characteristics. Introduction A wet clutch consists of multiple friction discs and reactor plates that rotate at different speeds. They have been widely used in transmissions, limited slip differ - ential in cars, as well as in heavy duty equipment (such as large agricultural tractors). They are also widely used for braking applications, such as dynamometers. Dynamometers are commonly used to test transmissions and engines, where the torque output is measured by applying some sort of braking. During braking, high heat is generated between the moving and stationary parts. In order to prevent overheating of components a fluid medium such as oil is used as a cooling/shearing media. Oil Shear Technology that is of the wet or hydroviscous type transmits torque between the drive plates and friction surfaces. Anderson and Knapp [ 1] defined the thermal failure modes of wet clutches, which include: coning, hot spotting of the steel plates, smearing of the friction material, and the breakdown of cooling oil properties. A major component of Oil Shear Technology is providing a film of transmission oil between the friction material and opposing reaction disc. In a brake the friction discs are splined and rotating with the output shaft and the reaction plates are locked to the housing. When engaged, the output shaft will be decelerated to a stop. A schematic of the entire assembly is shown in Figure 1 . Figure 2 illustrates all the components for one of the clutch pack pairs. Engagement consists of squeezing together the friction discs and reaction plates. This can be accomplished through a piston actuated by pneumatic or hydraulic pressure, or springs through a pressure plate. The higher the engagement pressure, the more torque is transmitted. Oil/Transmission fluid (TF) cools the wet clutch by flowing through the surfaces of the friction discs and steel plates. Friction plates have grooves that aid oil flow from the inner edge of that plate to the outer edge. Natsumeda and Miyoshi [2] reported a comprehensive numerical simulation of wet clutch engagement. Their model included the effect of surface roughness, permeability, and waviness in the friction-lining material. However, the groove effect was not considered in their analysis. Jang and Khonsari [ 3] provided a detailed parametric study and formulated the governing equations, boundary conditions, and numerical solution technique for modeling the thermal aspects of the engagement process in a wet clutch. A thermal analysis of a wet clutch is usually performed by creating a three-dimensional heat conduction finite element analysis model, ignoring the impact of grooves, and calculating the temperature