Comparative Performance Analysis of Range Extender Systems Using Various Micro Gas Turbine Layouts

The opportunity to employ small-scale gas turbines as prime movers in vehicles was exploited some decades ago, but only few prototypes were developed. Interest in micro gas turbines (MGTs) became mainly focused on combined heat and power (CHP) applications. Nevertheless, in recent years, MGTs have received renewed attention in the automotive sector as range extenders, owing also to their flexibility in operating with alternative fuels. In this context, the authors analyzed two different MGT layouts, to identify promising configurations for automotive applications in terms both of fuel flexibility and satisfactory performance levels. An intercooled, reheated and recuperated layout featuring an innovative burner configuration, assuming to operate in MILD (Moderate or Intense Low oxygen Dilution) combustion conditions, has been considered and compared with a simple recuperated layout of similar size. The potential of waste heat recovery has been also evaluated. The modeling approach combined a 0D thermodynamic model developed in Thermoflex with a dedicated combustion model capable of representing MILD conditions. Furthermore, the footprint in terms of weight and volume has been also considered concerning the heat exchangers. Results of simulations highlighted that the proposed Range-Extender MGT can achieve electrical efficiencies close to 36% while operating with methane, biogas, ammonia or hydrogen. Integrating an Organic Rankine Cycle increases the net efficiency to nearly 40%, though at the cost of almost doubling system weigh and volume.