Search Results

A novel Fast Response Chemiluminescence Detector and a Fast Flame Ionization detector have been used to examine the instantaneous NO and unburnt hydrocarbon concentration in the cylinder and exhaust port of a DI Diesel engine. The in-cylinder results indicate very high levels of NO in the premixed phase of combustion, followed by generally lower levels during the diffusion burning phase. Hydrocarbon signals also indicate significant detail. The in-cylinder uHC signal is consistent with the probe location being between two of the fuel sprays. Both in-cylinder and exhaust results indicate rather high cyclic variability in the NO levels at steady conditions. Variations in the timing and structure of the exhaust uHC signal during the valve open period with load may give insight into the fuel spray/air motion.

The control of transient emissions from turbocharged diesel engines remains an important objective to manufacturers, since newly produced engines must meet the stringent criteria concerning exhaust emissions levels as dictated by the legislated Transient Cycles. In the present work, experimental tests are conducted on a medium-duty, turbocharged and after-cooled diesel engine in order to investigate the behavior and formation mechanism of nitric oxide (NO), smoke and combustion noise emissions under various transient operating schedules including acceleration, load change and starting. To this aim, a fully instrumented test bed was set up in order to record and research key engine and turbocharger variables during the transient events. The main parameters measured were nitric oxide concentration and smoke opacity (both using ultra-fast response analyzers) as well as combustion noise.