A Variable Displacement Supercharger Performance Evaluation

Paper #:
  • 2017-01-0640

  • 2017-03-28
The Variable Displacement Supercharger (VDS) is a twin helical screw style compressor that has a feature to change the compression ratio actively during vehicle operation. This device can reduce the parasitic losses associated with supercharging and improve the relative fuel economy of a supercharged engine. Supercharging is a boosting choice with several advantages over turbocharging. There is fast pressure delivery to the engine intake manifold for fast engine torque response and the fun to drive feel. The performance delivered by a supercharger can enable engine fuel economy actions like engine downsizing and downspeeding. The cost and difficulty of engineering hot exhaust components is eliminated with using only an air side compressor. Faster catalyst warm up can be achieved when not warming the turbine housing of a turbocharger. To quantify these effects, a 2.0L engine is chosen for an analytical comparison of three boosting configurations: turbocharged, roots style supercharged, and twin screw compressor supercharged with variable internal compression. A number of partial load points were chosen to compare cycle averaged fuel consumption of the boost systems with weighting factors that represent a large SUV. The outcome of the simulation was that on an engine basis, the turbocharged motor had the best brake specific fuel consumption (bsfc). At the engine level, the VDS compressor configuration had 1.5% better fuel economy on the US06 cycle than the roots compressor configuration. Both were worse than the turbocharged motor; however, when installed in a vehicle, the final drive ratio can be adjusted to give show the VDS configuration achieves equal fuel economy and superior transient performance compared to the turbocharged configuration.
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