RELATING BURNING RATE AND NO FORMATION TO PRESSURE DEVELOPMENT IN 2-STROKE DIESEL-ENGINES

A multizone thermodynamic method has been developed to determine combu stion rate and NO formation from measured cylinder pressures and perfo rmance of two-stroke diesel engines. Integral to the analytical method is a nonlinear fit to the combustion chamber heat loss; the fit is co nsistent with the overall energy balance and with measured fuel consum ption rate and exhaust temperature. The method assumes equilibrium com bustion properties except for NO, whose relatively slow formation is e stimated using the extended Zeldovich mechanism in the post-flame gas during a period of one mixing time. Application of the method to a 2-s troke diesel engine indicates a post-flame mixing time of 0.55 ms or 4 deg crank angle at 1250 rpm, yielding exhaust concentrations of NO co nsiderably less than what would have been expected from equilibrium-th en-sudden-freezing considerations.