Numerical Evaluation of a Micro Gas Turbine Range Extender Vehicle in Worldwide Harmonized Light Vehicles Test Cycle (WLTC) Scenarios

The idea of using a Micro Gas Turbine (MGT) as range extender for Hybrid Electric Vehicles (HEVs) is discussed in the literature for several years now. It is regarded from an experimental as well as from a numerical point of view, both indicating superior exhaust gas emissions and performance compared to piston engines. This is commonly shown by applying a series of consecutive New European Drive Cycles (NEDC). In 2017, however, the new approval procedure Worldwide harmonized Light vehicles Test Procedure (WLTP) was introduced with a more realistic drive cycle and also a specific test procedure for HEVs. In this work, a drive cycle simulator is set up considering the essential vehicle components and incorporating a detailed model of the MGT steady-state as well as transient emission and performance behavior. The WLTP is applied to an MGT range-extended HEV considering different operating strategies and vehicle configurations. Further, a procedure depleting a fully charged battery and a full fuel tank based on the Worldwide harmonized Light vehicles Test Cycle (WLTC) is carried out in comparison. The evaluation of the different operation concepts and missions shows very low exhaust gas emissions. A clear relationship exists between the MGT load variations and the HEV emission behavior and efficiency. It also shows that there are significant differences in the results if either the official WLTP or the custom full-range mission is applied. These findings illuminate if the regarded procedures are suited to evaluate this range extender configuration and also provide information on future optimization targets for MGT HEVs.