Modeling of Two Charge-air Cooling Turbo-charging Systems for Spark Ignition Engines

Two charge-air cooling turbo-charging systems, named Turbo-Cool and T²C, have been introduced. Turbo-Cool employs an air turbine expander/suction-compressor unit in the intake side and a VGT in the exhaust side, while T²C employs an air turbine expansion in the intake side and an exhaust VGT with a same shaft with the air turbine. A Nissan SR20DET turbocharged gasoline engine with the two charge-air cooling turbo-charging systems have been modeled using GT-SUITE 6.0 engine simulation code. Modeling results show that either Turbo-Cool or T²C must be combined with exhaust VGT. The air turbine in both systems can be either VGT or fixed. Modeling results also show that the power at WOT and rated engine speed of the engine with the proposed charge-air cooling turbo-charging systems can be increased by 20∼30%, the maximum torque at WOT can be increased by 46∼71%, and the BSFC at WOT and rated engine speed can be decreased by 4∼5%. The large improvement of the torque at middle and low engine speed can result in an excellent torque back-up and correspondingly drivability for vehicle use.