1996 SAE International Congress & Exposition

Feb. 26-29, 1996, Detroit, MI

COMPUTER AIDED DESIGN OF AUTOMOTIVE ALTERNATOR FANS FOR IMPROVED COOLING PERFORMANCE AND NOISE

H. Didandeh, C. Toksoy, D. Johnson and A. Ecer, Technalysis Inc.

M. Hull and D. Buening, Delphi Energy & Engine Management Systems

Abstract

Development process of a set of duct fans for an automotive alternator is described. By computer modeling, one can estimate the airflow characteristics of a given fan for providing increased cooling performance and lower noise. The process includes identification of several fan geometries and definition of an optimum configuration. Test results are provided for the final design.

Introduction

For an air-cooled alternator, the heat generated by various electrical components of the alternator is removed by properly managing the airflow. The packaging requirements result in many restrictions for the airflow through the alternator. While the two fans on each end drives the airflow, the details of the geometry of the inlet, the electrical components and the rotor also strongly effect the cooling characteristics of an alternator. Especially, the details of the airflow on the regulator side of the alternator has to be studied carefully, in terms of the amount of air and its distribution as a function of fan performance and system restrictions. In the present paper, the design of dual internal fans for cooling of an alternator is discussed for both the Slip Ring End Fan (SRE) and the Drive End (DE) fans.

In this paper, the details of the design process for improving the airflow performance of automotive alternator is presented. Emphasis is given to the design of the fans. The objectives of the design involves controlling the flow, managing its distribution and reducing the flow induced noise. Only the details of the flow analysis is presented in this paper although similar analyses were performed for determining the heat transfer characteristics.

The DE Fan is designed to cool the rotor segment and the windings of an alternator. While for the previous designs, an external fan was employed for this purpose, the current design is based on an internal DE fan which is located on the side of the pulley and the drive end bearing. SRE fan is designed to cool the electrical components of the alternator and it is located on the opposite side of the drive end. The airflow entering through this fan controls the cooling performance of the electronics. The procedure includes both the study of an isolated fan and its installation.