Impact of Ambient Temperature Conditions on Cold Start Combustion, Gaseous and Particle Emissions from Gasoline Engines 2017-01-2286

Ambient temperature conditions, engine design, fuel, lubricant and fuel injection strategies influence the cold start performance of gasoline engines. Despite the cold start period is only a very small portion in the legislative emission driving cycle, but it accounts for a major portion of the overall driving cycle emissions. The start ability tests were carried out in the weather controlled transient dynamometer - engine test cell at different ambient conditions for investigating the cold start behavior of a modern generation multi-point fuel injection system spark ignition engine. The combustion data were analyzed for the first 200 cycles and the engine performance and emissions were analyzed for 300 s from key-on. It is observed that cumulative fuel consumption of the engine during the first 60 s of engine cold starting at 10 °C was 60% higher than at 25 °C and resulted in 8% increase in the value of peak speed of the engine. The rate of pressure rise was significantly higher and prolonged for a number of cycles at 10°C compared to 25 °C and 45 °C. The cycle-to-cycle variation in the cylinder pressure at 10 °C was three times higher than at 25 °C. The first 60 sec of the cold start cumulative CO emission at 10 °C was approximately 3 times higher; cumulative HC emission was 3.5 times higher; cumulative NOx emission was 50% lower than that of at 25 °C. The particles in the size range of 50-200 nm are accounted for 60% at 10 °C and 6-8% at 25 °C & 45 °C ambient temperature conditions. The exhaust particles at the low ambient temperatures increased the exhaust particulate mass by 30 times at 10 °C in comparison with that of at 25 °C. The accumulated unburned fuel during the cold start period combusted abruptly and caused for the higher peak speed and exhaust emissions.