Abstract
Mechanismes of nitric oxide formation and emission for a conventional high-speed direct-injection diesel engine have been studied by a stochastic model that takes chemical kinetics into account. In calculations cetene was used as a fuel and its initiation processes were expressed by a one-step global mechanism. Detailed reduced chemical mechanisms were employed for the processes of heat release and NO formation. The calculated NO concentration coincides with a value measured in an exhaust gas within ±10%. It is shown that most NO is formed locally at temperatures higher than 2200 K under a range of excess air ratios, 1 < ë < 3. In addition, the effects of water addition and EGR on reducing NO emission are discussed.