The Effect of TDC Temperature and Density on the Liquid-Phase Fuel Penetration in a D. I. Diesel Engine

A parametric study of the liquid-phase fuel penetration of evaporating Diesel fuel jets has been conducted in a directinjection Diesel engine using laser elastic-scatter imaging. The experiments were conducted in an optically accessible Diesel engine of the ``heavy-duty`` size class at a representative medium speed (1200 rpm) operating condition. The density and temperature at TDC were varied systematically by adjusting the intake temperature and pressure. At all operating conditions the measurements show that initially the liquid fuel penetrates almost linearly with increasing crank angle until reaching a maximum length. Then, the liquid-fuel penetration length remains fairly constant although fuel injection continues. At a TDC density of 16.6 kg/m{sup 3} and a temperature of about 1000 K the maximum penetration length is approximately 23 mm. However, it varies significantly as TDC conditions are changed, with the liquid-length being less at higher temperatures and at higher densities. The corresponding apparent heat release rate plots are presented and the results of the liquid-phase fuel penetration are discussed with respect to the ignition delay and premixed bum fraction

Pulse combustion: The quantification of characteristic times

Measurements of the total ignition delay time in a pulse combustor have been made for several chemical kinetic ignition delay times and several fluid dynamic mixing times. These measured total ignition delay times are compared with calculated values of the characteristic time for mixing and with calculated values for the homogeneous ignition delay time. A chemical kinetic model was used to calculate the homogeneous chemical kinetic ignition delay time for conditions typical of an operating pulse combustor. Similarly, a fluid dynamic mixing model was used to estimate characteristic times for a transient jet of cold reactants to mix with an ambient environment of hot products to an ignition temperature. These calculated time scales compared well with measured values in both trend and magnitude. It has also been shown that a simple sum of the characteristic mixing times and chemical kinetics times provides a good first-order approximation to the total ignition delay time.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/28736/1/0000563.pd