Uncoupled Turbocharged Engine-Compressor Circuit for improving the charge pressure limit of gasoline powertrains at low RPMs

Paper #:
  • 2017-01-1033

Published:
  • 2017-03-28
Abstract:
Conventional gasoline engine turbocharger circuits are equipped with waste-gates for uncoupling the turbine from the engine as a technique of regulating peak charge pressure. Electrically actuated waste-gates extend the functionality to emission control. These advantages are, however, offset by an increase in the amount of unpurged heat energy that is expelled to the environment. This paper introduces a passive engine bypass path that uncouples the engine from the compressor, thereby, allowing the sizing and operation of the waste-gate to be optimized. The layout was installed in a 2.0 liter Spark Ignition Direct Injection (SIDI) turbocharged engine. A three-way catalytic converter and a lambda control combustion strategy were employed as an Emissions After Treatment (EAT) system. Tests were conducted to estimate peak charge pressure and tailpipe emissions. The measurements include full load brake torque measurements and cold start emission traces. The data indicates a maximum improvement of 15% in brake torque at low RPMs while reducing cold start exhaust warm-up time. Consequently, the results indicate a reduction in cold tailpipe Nitrogen Oxide (NOx) emissions which dropped by 72%, Carbon Monoxide (CO) emissions were reduced by 90% and Unburnt Hydrocarbons (UHC) by 29%. The preliminary results demonstrate the potential benefits of uncoupling the engine from compressor as a technique of enhancing low-end charge pressure without compromising emissions.
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