Investigation of effects of spark plug's electrodes erosion on the required ignition voltage and performance of natural gas engine

In this research, the effect of electrode's configuration on the required voltage and performance of a natural gas fuel base engine is investigated using three types of spark plugs with the same heat range and different electrode's configuration. Then, durability of spark plugs is investigated in durability tests. Scanning electron microscope (SEM) is used to study mechanisms of electrode erosion. Also, sparking quality of spark plugs has been investigated by spark plug test rig. Finally, the effects of electrode erosion on the required voltage, performance and fuel consumption of engine will be investigated during combustion test. According to the results of new spark plugs, groove in ground electrode causes to 21% decline in required voltage. Considering results of durability tests, after 200 hours test, average of gap growth for nickel based electrodes seven times higher than platinum electrodes. SEM analysis of electrode's surface indicates many cracks and craters on the surface of nickel based electrodes. Initiation and growth of cracks and intrude of calcium oxide could lead to accelerate erosion of nickel based electrodes. Results of combustion test shows that if ignition coil could supply required voltage, electrode's erosion would not considerable effect on the amount of torque and brake specific fuel consumption (BSFC) of engine in operation with CNG.