Investigation of turbocharged diesel engine operation, exhaust emissions, and combustion noise radiation during starting under cold, warm, and hot conditions

Abstract

Control of performance and transient emissions from turbocharged diesel engines is an important objective for automotive manufacturers, since stringent criteria for exhaust emissions must be met. In particular, (cold) starting is of exceptional importance owing to its significant contribution to the overall emissions during a transient test cycle. In the present work, experimental tests were conducted on a turbocharged and after-cooled bus–truck diesel engine in order to investigate the engine operating behaviour and the formation mechanisms of nitric oxide, smoke, and combustion noise during cold, warm, and hot starting. With this as a target, a fully instrumented test bed was set up, using ultra-fast response analysers capable of capturing the instantaneous development of emissions and various key engine and turbocharger parameters. The experimental test pattern included a variety of starting conditions, defined by the thermal status of the engine (i.e. the coolant temperature) and its idling speed. As expected, turbocharger lag was found to be the major contributor for the pollutant emissions spikes in all cases, with the thermal status of the engine and its idling speed playing important roles in the combustion (in)stability, turbocharger response, and noise radiation.