极品飞车17汽车分布:请帮我英译汉，译得好的有加分！

CO EMISSIONS – The cold start CO emissions showed a similar trend with ambient temperature to that of the HC emissions as shown in Fig.25. The influence of ambient temperature on CO emissions was greater than that on HC emissions. This was due to the nature of combustion process in SI engines. CO is an equilibrium combustion product for rich mixtures and rich mixtures are used under cold start conditions in Euro 1 SI
engines. Equilibrium CO emissions can be as high a 10% for mixtures that are 50% rich. The extent of the cold start over fuelling usually increases as the ambient temperature decreases. These equilibrium effects are in addition to any combustion inefficiency sources of CO emissions, which are related to the sources of HC emissions.The cold start CO emissions as a function ambient temperature in Fig.25 may be extrapolated from curve fit to enable the emissions at –7oC to be determined. This
is done in Fig.25 and the results are cold start CO emissions of 690 g/kg fuel. Comparison of this result with the legislated levels is made in Table 3 and this shows that these levels are well above the legislated levels by a factor of 4. Thus the new –7oC cold start CO standard is arduous to Euro 1 vehicles. NOx EMISSIONS - Fig.26 shows the NOx emissions as a function of ambient temperature for the cold start phase of Leeds urban test cycle. The NOx emissions with curve fits showed a different trend to those for HC and CO emissions. There were no consistent trends with temperature for both engine out and catalyst out
emissions. The reason was that engine out NOx emissions are reduced by cold conditions as the engine metal, water and lubrication oil temperatures are all cold and this cools the combustion, which decreases the NOx formation. Counteracting this trend is the increase in NOx due to the higher throttle angles required to overcome the increased friction losses as the ambient temperature becomes cooler. Set against these trends is
the increase in the catalyst activity for the rich mixtures used in cold starts, as the catalyst is warmed-up.
N2O EMISSIONS - There were only small changes in N2O emissions with ambient temperature upstream of catalyst. The curve fits shown indicate a small decrease in emissions as the ambient temperature increased, as shown in Fig.27. However, downstream of the catalyst there was a major impact of the ambient temperature on N2O emissions. Increasing the ambient temperature
resulted in the production of N2O by the TWC, as shown in Fig.27. The N2O emissions were more than doubled downstream of the catalyst for the most of ambient temperature conditions except -2°C. This was because as the ambient temperature increased under cold start conditions the temperature of catalyst was in the N2O formation range (250~350°C). At the –2oC cold start condition the catalyst was too cold in the first test and reached the critical temperature region for N2O
production during the second lap, as shown above.
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