Abstract
Key words:
Exhaust emission, low environmental temperatures, catalyst start, mathematical model
Abstract:
The period of engine operation until the catalyst and engine reach their working temperature is called the engine cold start. During that period, there is a significantly increased emission of harmful engine gases, particularly at very low environmental temperatures. According to the references, during the engine cold start, at low environmental temperatures, there is 95 – 98% of the total HC and CO emission present during the driving test. Therefore, reducing of emission during that period is of great importance for the reduction of entire engine emission. This study was conducted to test the starting speed of the catalyst at low environmental temperatures. During the research, construction parameters of exhaust system were adopted and optimised at environmental temperature of 22oC. The proportion at which they were at their best, according to low environmental temperatures, was observed. The research was conducted by use of mathematical model and TERMO developed computer programme for calculation of non-stationary heat transfer in engine exhaust system. The results showed that the temperature in the environment did not have any significant influence on pre-catalyst light-off time. In the elementary catalyst, a significantly higher influence of temperature in the environment on the catalyst light-off time was noticed, because there was a greater external surface through which the heat was emitted and the heating capacity of the parts before the catalyst was greater.