Turbogenerator transient energy recovery model

Significant exhaust enthalpy is wasted in gasoline turbocharged direct injection (GTDI) engines; even at moderate loads the WG (Wastegate) starts to open. This action is required to reduce EBP (Exhaust Back Pressure). Another factor is catalyst protection, placed downstream turbine. Lambda enrichment is used to perform this. However, the conventional turbine has a temperature drop across it when used for energy recovery.

Catalyst performance is critical for emissions, therefore the only location for any additional device is downstream of it. This is a challenge for any additional energy recovery, but a smaller turbine is a design requirement, optimised to work at lower operating pressure ratios.

A WAVE model of the 2.0L GTDI engine was adapted to include a TG (Turbogenerator) and TBV (Turbine Bypass Valve) with the TG in a mechanical turbocompounding configuration, calibrated with steady state dynamometer data to estimate drive cycle benefit. The model derived is used in the development of more advanced control system algorithms. Furthermore, transient verification with WAVE-RT in co-simulation is performed on drive cycles (NEDC, WLTP).

Analysis includes power and fuel consumption, and an additional knock impact assessment. It is shown on the WLTP that, depending on the calibration, up to 9% FC (Fuel Consumption) reduction is achievable with a 0.03kW thermodynamic power recovery, for a similar controller performance. Hints are given for further controller enhancements.

Prototype dynamometer testing or vehicle could be performed to verify design assumptions and simulation results. Electrical turbo-compounding, interfacing to the power-grid, and calibration optimisation, with combined WG and TBV settings is feasible based on this initial work.