Experimental study of transient nitric oxide, smoke, and combustion noise emissions during acceleration of an automotive turbocharged diesel engine

The control of transient emissions from turbocharged diesel engines is an important objective for automotive manufacturers, since newly produced engines must meet the stringent criteria concerning exhaust emissions levels as dictated by the legislated Transient Cycles Certification. In the current study, experimental tests are conducted on an automotive, turbocharged diesel engine in order to investigate the formation mechanism of nitric oxide, smoke, and combustion noise emissions under various acceleration schedules experienced during daily driving conditions. To this aim, a fully instrumented test bed was set up in order to capture the development of key engine and turbocharger variables during the transient events. Analytical diagrams are provided to explain the behaviour of emissions development in conjunction with turbocharger and governor/fuel pump response. Turbocharger lag was found to be the main cause for the emission spikes during all test cases examined, with the engine calibration playing a vital role. The analysis was extended with a quasi-steady approximation of transient emissions using steady-state maps, in order to highlight the effect of dynamic engine operation on pollutants and combustion noise emissions.