Ulrich Kramer

Experimental Determination of the Oxygen Concentration in the Start Cylinder of a Direct Started Engine

Spark ignited engines with direct fuel injection into the combustion chamber can be started by injecting fuel into the combustion chamber of the stopped engine and igniting it afterwards with the spark plug. The explosion of the air fuel mixture initially rotates the crankshaft. The engine is started without motoring the crankshaft with a starter device. The described start procedure is called Direct Start. For a successful Direct Start a maximum oxygen concentration in the Direct Start Cylinders (the cylinders utilized initially for the Direct Start) is required, because the oxygen concentration in the start cylinders determines the maximum amount of energy, which can be exploited to move the crankshaft over the following TDC (Top Dead Center). After the engine stop the Direct Start Cylinder valves are closed. Therefore the oxygen concentration has to be maximized during the preceding engine shut down. For the following Direct Start also an appropriate prediction of the oxygen concentration in the Direct Start Cylinders is important, with the aim to be able to meter a suitable amount of fuel for the Direct Start.

Review of combustion engine efficiency improvements and the role of e-fuels

Over next decade, SI engines might adopt a significant amount of design solutions from CI engines. Therefore none of both can be finally called the winner – they are merging into an optimized engine for future sustainability requirements and heavily depend on technology readiness and technology cost, customer acceptance as well as total cost of ownership assessments. The fuel of choice (e.g. E-methane and E-DME) might determine which engine type can deliver lowest CO2 emissions.