An automotive engine charge-air intake conditioner system: analysis of fuel economy benefits in a gasoline engine application

A combination of analytical techniques has been used to quantify the potential fuel economy benefits of an automotive engine charge-air intake conditioner system applied to a spark-ignited gasoline engine. This system employs a compressor, intercooler, and expander to provide increased charge density with the possibility of reducing charge-air temperature below sink temperature. This reduction in charge-air temperature provides the potential for improved knock resistance at full load; thereby allowing the possibility of increasing compression ratio with corresponding benefits in thermodynamic cycle efficiency and part-load fuel economy. The four linked and interfaced models comprised a first-law thermodynamic model of the charge-air conditioner system, a one-dimensional engine cycle simulation, a two-zone combustion model, and a knock criterion model. An analysis was carried out under full load at 3000 r/min and showed that a charge-air conditioner system - with compressor, intercooler, and expander efficiencies of 0.8 - allowed the compression ratio to be increased by approximately half a ratio, which gave up to 1.5 per cent reduction in brake specific fuel consumption at 2000 r/min 2 bar brake mean effective pressure when compared with a conventional pressure charger intercooler system with no expander.