At the Institute of Internal Combustion Engines of the Technische Universitaet Muenchen a drivetrain for urban and commuter traffic is under development. The concept is based on a lean-burn air-cooled two-cylinder natural gas engine which is combined with a hydraulic hybrid system.
The engine is initially mechanically charged which results in an engine speed dependent torque. Turbocharging the natural gas fuelled engine derives increased engine torque especially at low engine speeds and exploits the potential of better knock resistance of natural gas compared to gasoline fuel.
The paper presents a turbocharging concept for the two-cylinder engine at first. The firing order of 180/540°CA due to the crank shaft design and the lean-burn combustion are challenging restrictions to cope with. The consequences of the uneven firing order are investigated using 1D-simulation and the matching of the exhaust gas turbocharger is shown. Afterwards, results of the engine test-bench at different engine operation points are opposed to the simulation results and evaluated. The results are compared to other approaches and assessed.
Altogether, the paper describes design, application, 1D-simulation and test bench results of a turbocharging concept for a two-cylinder lean-burn natural gas engine with an uneven firing order.