Mathematical model of vehicle gearbox heat transfer

Constant fluctuations are observed on the fuel prices today due to increasing demand on fossil energy resources and the security problems experienced in energy supply chain. In addition to that, fuel consumption concerns have increased in the consumer market due to increasing environmental awareness and serious measures taken by governments regarding exhaust emissions. New regulations and customer expectations encourage automotive manufacturers to design vehicles with lower fuel consumption. In order to achieve lower aerodynamic resistance, which is an important factor in vehicle fuel economy, companies offer a wide range of component and vehicle designs. Popular underfloor panel applications at this point may cause rises on transmission operating temperatures by reducing air flow around the gearboxes, which needs more air flow due to increased engine powers. This application gives beneficial results in terms of fuel consumption up to a certain level, but it can also have an effect on the mechanical life of the gearbox if thermal characteristics are not under control. In this study, it was aimed to create a dimensionless mathematical model that can calculate the gearbox operating temperatures of a light commercial vehicle in the early stages of the project. During development phase of this model, necessary technical data were collected from the manufacturers, vehicle level CFD analyzes and full size wind tunnel tests were made to support model outputs. The resultant mathematical model can be used to calculate time-dependent gearbox operating temperatures for defined test cycle and vehicle specifications. In this way, the gearbox temperatures can be predicted during the computer-aided design phase of the project and the necessary design actions can be taken without p rototype & die costs. At the same time, fuel consumption effect of gearbox temperatures can also be calculated with additional engine data. This will also help to reduce team workloads on trade-off issues between fuel consumption and thermal attributes.