Investigations on a Novel Supercharging and Impulse Turbo-Compounding of a Single Cylinder Diesel Engine 2022-01-1111

Single-cylinder engines in mass production are generally not turbocharged due to the pulsated and intermittent exhaust gas flow into the turbocharger and the phase lag between the intake and exhaust stroke. The present work proposes a novel approach of decoupling the turbine and the compressor and coupling them separately to the engine to address these limitations. An impulse turbine is chosen for this application to extract energy during the pulsated exhaust flow. Commercially available AVL BOOST software was used to estimate the overall engine performance improvement of the proposed novel approach compared to the base naturally aspirated (NA) engine. Two different impulse turbine layouts were analyzed, one without an exhaust plenum and the second layout having an exhaust plenum before the power turbine. The merits and limitations of both layouts are compared in the present study. An optimum nozzle area ratio of 50% for the first layout was arrived, which provided better net engine performance with 53.7% higher brake power output and 5.8% higher brake thermal efficiency. The second layout fared better with a nozzle area ratio of 13% and a plenum volume of 1 litre. The second layout delivered 52.8% higher brake power output and 5.5% higher brake thermal efficiency at rated power conditions. Both supercharged configurations produced 1.8 bar (absolute) boost pressure that increased airflow rate by 33% more than the NA configuration. This would improve combustion efficiency and reduce exhaust emission congruent with any charged engine. Thus, the present novel approach with both the layouts benefitted from charging the single-cylinder diesel engine, which was otherwise difficult in conventional turbocharging.