Single-Stage High-Pressure Turbocharging

Abstract

To meet the ever-increasing demands that will be made on engines, and especially on planned new engine generations, in the future, the power density of their turbochargers will have to be significantly increased. Raising the brake mean effective pressure, introducing Miller timing and providing support for exhaust-gas treatment all presuppose an increase in the turbo’s compressor pressure ratio while keeping the turbo unit as compact as possible. To fulfill all of these conditions with single-stage turbocharging, a new approach to future turbocharger design is needed, especially when additional expensive materials, such as titanium, are not to be used. On the compressor side, when using proven aluminum compressors, this requires additional cooling of the compressor wheels. But other turbocharger components too, such as the turbine, bearings, shaft seals and also the casings and their connections, are exposed to higher thermal and mechanical stresses as a result of the pressure ratios being far higher than those of turbochargers currently on the market. The challenge, which could also be called a balancing act, in dimensioning new turbochargers for single-stage high-pressure turbocharging with aluminum compressors is to design the components with the help of the available tools such that sufficient safety and component lifetime are achieved while performance and component efficiency are optimized. By using the available calculation tools, such as FEM or for the fluid dynamics CFD, it is now possible to achieve compressor pressure ratios of up to 5.8 in continuous operation with single-stage turbocharging while ensuring a compact turbocharger design and aluminum compressors. The paper describes how ABB Turbo Systems Ltd has successfully developed and qualified a new single-stage high-pressure turbocharger generation with radial turbine which allows compressor pressure ratios of up to 5.8 in continuous operation at 100% engine load. First successful engine tests with the new A100 radial turbocharger generation have been carried out both on medium- and on high-speed engines. The first frame sizes of the new A100 high-pressure turbocharger series have been released for market introduction, setting a significant new benchmark for turbocharging advanced diesel and gas engines.