Experimental investigation of coolant float sensor and engine switch off circuit unit to control engine overheating

Abstract

This thesis looks at devising a model to control engine overheating. A series of experiments were conducted on the engine/coolant sensors of a four-cylinder four stroke cycle diesel engine to assess their effectiveness in monitoring engine running temperatures. A magnetic float sensor circuit model was developed to monitor the coolant level in the radiator as a backup device to the temperature sensors. This backup model had the ability to turn off the engine in an event of coolant losses which could trigger overheating. The results show that, this model was sensitive to coolant levels in the radiator and prevented the engine starting or running under low coolant level. The results also showed that under low coolant engine running, both engine and coolant temperature sensors indicated a large temperature disparity, as high as 130OC and as low as 20OC respectively. However, they displayed a slight margin of difference under full coolant level at 45OC and 40OC respectively. The results further indicated that, at very low or dry coolant ran, the engine temperature sensor indicated higher figure (130OC) than the coolant temperature sensor (20OC); however, at high coolant level the opposite was the case. This was so because at high coolant level, the coolant absorbs more heat from the engine walls therefore runs at a higher temperature than the cylinder wall. Though the results show that the sensors worked well, they did not have the capacity to switch off the engine to prevent overheating during coolant lose because they are only able to sense the coolant temperature but not able to measure the system coolant level or quantity and this is a setback.