Injection Parameter Effects on a Direct Injected, Pilot Ignited, Heavy Duty Natural Gas Engine with EGR

Experimental investigation on performance and heat release analysis of a pilot ignited direct injection natural gas engine

“…In addition, It can be noticed from the cumulative heat release rate that in the initial stages, cumulative heat release is relatively higher at injection intervals of 0.7 ms and 0.9 ms as the combustion of pilot diesel is more premixed, however, in later stages, cumulative heat release of smaller injection intervals is apparently higher due to the more rapid combustion of main fuel natural gas. McTaggart-Cowan et al [12] also had the similar findings. Fig.…”

“…On the basis of the modeling work, they concluded that the changing trends of the simulation results were not sensitive to the mechanism applied. McTaggart-Cowan et al assessed the effects of injection pressure, injection interval [11,12], fuel composition [13] as well as compression ratio [14] on the combustion behavior. Their experimental results suggested that the whole combustion duration of both fuels were shortened at higher injection pressures and the combustion events of diesel and natural gas were difficult to differentiate at shorter injection intervals.…”

Combustion process and emissions of a heavy-duty engine fueled with directly injected natural gas and pilot diesel

“…Moreover, at low engine speed, THC emissions suffer more from high pressure as a result of increased fuel injected into crevice and near-wall regions caused by longer penetration. However, at high engine speed, inconsistent trend is revealed, poor mixing quality incurred by excessively low injection pressure may lead to deteriorated THC emissions, which, however, is disagree with that displayed in the study of McTaggart-Cowan et al [28] on a single cylinder engine with EGR. Fig.…”

“…9b). Discrepancies can be found in the results of another work by McTaggart-Cowan et al [28], where both peak values of heat release raise as injection timing advances. The differences in EGR rates and injection separation may be responsible for this phenomenon.…”

“…Harrington et al [25] conducted developmental tests on a six-cylinder four-stroke engine over AVL 8 modes with three different operating strategies; their results suggested that highest cycle NOx reduction can be achieved by optimizing injection timing without sacrifice of thermal efficiency; however, as a result of the technique limitation, the injection pressure chosen was 21 MPa and in addition, they did not present the optimization process of the injection pressure. McTaggart-Cowan et al [26][27][28] investigated the effects of injection pressure on combustion and emission characteristics on a four-stroke single-cylinder engine by comparison of heat release rates and emissions at injection pressures of 21 MPa and 30 MPa; On the basis of their experimental results, conclusions were drawn that the ignition and combustion process of both fuels are shortened through the use of higher injection pressure; NOx emissions are slightly influenced when injection pressure raises while improved evidently by retarding injection timing; CO emissions show different changing tendencies for different engine speed with the increasing injection pressure; though they tried to interpret the combustion events by incylinder pressure traces and heat release rate, the explanations seem to be insufficient, it would be more convincing if the analyses of combustion parameters and fuel economy are added. Therefore, in order to get a thorough understanding of the combustion process and how combustion, emission characteristics and fuel economy are related to each other in engines fueled with directly injected natural gas and pilot diesel, a systematic study of this issue is essential.…”