Cooling System of a High-Pressure Centrifugal Compressor: Development and Impact on Wheel Temperatures

Abstract

High power density, low fuel consumption, and a compact design with competitive total costs of ownership are key requirements for internal combustion engines for conventional fuels and carbon-free or carbon-neutral future fuels. These requirements influence the development targets of charging systems and call for single-stage charging systems with increased charge air pressures. However, high compressor pressure ratios of the turbocharger lead to challenging material temperatures in aluminum alloy wheels. Consequently, creep becomes the fundamental lifetime-limiting damage mechanism for these wheels. In order to meet customer requirements regarding total costs of ownership, the lifetime is of major importance for the development of aluminum compressor wheels for turbochargers with pressure ratios beyond 6. This paper focuses on a high-pressure compressor (HPC) design with a water-cooling system for a new turbocharger generation. The development of its components and their validation based on numerically predicted and measured compressor wheel temperatures are discussed. After introducing the need for high-pressure ratios and the accompanying lifetime challenges, the paper presents the design strategy and methods of the development process. Finally, the paper summarizes the achievements obtained by this procedure. Detailed and rarely before documented temperature measurements from the rotating compressor wheel are published. As will be shown, the temperature measurements confirm the predictions from the predevelopment phase. A comparison of the temperature measurements from the recently developed compressor wheel with measurements carried out for a state-of-the-art wheel reveals the technological improvements achieved by this new generation of high-pressure compressor wheels.