Förbränning av biogas/metan i en EcoMarathonmotor

Sammanfattning: This report is about the process of converting a petrol-fuelled Honda GX35 engine to runon methane gas. The future goal is to use the engine in the engineering competition ShellEco-marathon, where the aim is to drive a vehicle as far as possible with a set amount offuel.To enable methane fuelling, the carburator of the GX35 was replaced with a gas fuel injectorfrom the engine accessory company Ecotrons. This was attached to an aluminium intake pipeconstructed by the project group. A new flywheel was constructed, equipped with twelvemagnetic detection points instead of one for more accurate detection of the crankshaftposition. A magnet was also attached to the upper cam pulley to enable position detection.The original exhaust system was replaced by a holder of a lambda sensor and a straightexhaust pipe. Together with the engine control unit (ECU) KATLA, developed earlier for abachelor’s thesis at Chalmers, this enabled detailed control of ignition and fuel injection, aswell as measurement of the air-fuel ratio.In order to test the engine with a load, a brake device was constructed. A moped wasacquired, whose gearbox and rear brake was used to brake and gear down the output shaftof the methane engine. The flywheel of the methane engine was connected to the flywheel ofthe moped through a vibration reducing rubber disc and a steel adapter. The rear wheel ofthe moped was lifted from the ground with a support so that it could rotate freely. By doingthis, the load of the engine could be controlled with the rear brake pedal of the moped.Methane was not available for the project group, so the engine was tested with liquefiedpetroleum gas instead, which is another gaseous fuel. Before the engine was started, the flowrate through the gas injector was measured. This data was used to set the fuel parametersin the ECU. With some minor adjustments the engine ran well during testing.