Performance evaluation of low-pressure turbine, turbo-compounding and air-Brayton cycle as engine waste heat recovery method

This paper presents an equivalent comparison of waste heat recovery method on an internal combustion engine using low-pressure turbine (LPT), turbo compound (TC) & air-Brayton cycle (ABC). A 5.9 L, six cylinders turbocharged diesel engine is used for this case study. All recovery methods are simulated on AVL BOOST where the engine model, turbocharger and heat exchanger are validated with experimental data. It is found that all three methods cannot work effectively without at least reducing the turbocharger turbine size to amplify the compressor surplus power. It is done by using a commercially available turbocharger turbine with smaller area over radius (A/R) volute, hence ensuring the least possible engine hardware change. In all the cases, the engine is ensured to deliver its baseline brake power. It is shown that LPT can recover the most exhaust waste heat (up to 5.40 kW), followed by TC (up to 1.75 kW) and ABC (up to 0.64 kW)