Advanced Boost System Developing for High EGR Applications

Abstract

Project Objectives:• To support industry efforts of clean and efficient internal combustion engine development for passenger and commercial applications• This program focuses on turbocharger improvement for medium and light duty diesel applications, from complete system optimization percepective to enable commercialization of advanced diesel combustion technologies, such as HCCI/LTC.• Improve combined turbocharger efficiency up to 10% or fuel economy by 3% on FTP cycle at Tier II Bin 5 emission level.Results: Production Honeywell GT35 and IHIF55 turbochargers were used as donor turbo on which advanced compressor and mixed flow turbine wheels were designed and fabricated for MD and LD diesel applications, respectively. Flow bench tests demonstrated that the advanced compressor offers 38% extra flow capacity, 8-10% better efficiency over the MD donor turbo compressor. The mixed flow turbine gained 10-15% efficiency at low U/C areas. The engine dynamometer test has demonstrated that the advanced LD turbo (TS11) gained 3.3% thermal efficiency improvement over the base LD turbo on FTP cycle at T2B5 tailpipe emission level. Background:Advance combustion technologies, such as HCCI and LTC, are considered critical to reduce NOx and PM emission on future diesel engines. Over the past twenty years, tremendous effort and progress has been made in the investigation of HCCI and LTC. Ford Motor Company's internal investigations as well as external researches have demonstrated substantial benefit in NOx and PM reduction as well as BSFC improvement using HCCI/LTC and pHCCI technologies on diesel engines, compared to conventional heterogeneous combustion mode (A. Helmantel, et al, 2004; J. Olsson, et al, 2004; R. Buchwald, et al, 2004; R. Sun, et al, 2004; K. Akihama, et al, 2001; S. Kimura, et al, 2001; S. Kook, et al, 2004 [1, 3, 5, 12, 18, 20, 24, 28]. These Diesel HCCI is based on the concept that if the diesel combustion ignition delay were held long enough, allowing enough time for diesel droplets to be fully atomized, vaporized and mixed with air to form a truly homogenous mixture, spontaneous combustion could occur simultaneously throughout the entire combustion chamber that is heavily diluted by EGR and global combustion temperatures (well below the adiabatic flame temperature due to absorption of thermal energy by EGR that has very high thermal capacity C p ) are thus greatly reduced to levels below the NOx and soot formation threshold.Investigations by Ford and many other researchers, including Toyota, Mitsubishi, Caterpillar and IFP (Institute Français du Petrole) indicate that simultaneous reduction of soot and NOx is possible with low temperature combustion technology using large amount of cooled EGR under near stoichiometric and even in rich operating conditions. Different to conventional diesel engine where ignition timing and combustion events are mainly controlled by fuel injection, combustion phasing of a diesel HCCI engine, is largely kinetically controlled, and depending on the combination of mixture tem...