The Rotary Fuel-Injection Pump as a Source of Cyclic Variation in Diesel Engines, and its Effect on Nitric Oxide Emissions

Abstract

Cyclic combustion variations have been demonstrated to exist in a direct injection Diesel engine to a surprisingly large extent. With the aid of an on-line computer engine-test facility statistical and correlation analyses were carried out to verify a strong relationship between the cyclic combustion variations and variations in the timing of fuel injection. The importance of these cyclic variations in the reduction of nitric oxide emissions from the engine is shown by experimental results and computer combustion model predictions. The overall effect on nitric oxide emissions is, however, small over most of the operating range of the engine.

The combustion of n-butanol/diesel fuel blends and its cyclic variability in a direct injection diesel engine

“…Sczomak and Henein [58], in an extensive experimental investigation on a CFR pre-chamber diesel engine running with various lowignition-quality fuels, tried to correlate cyclic pressure variations with ignition delay and dynamic injection timing and pointed out that low cetane number fuels may cause cyclic irregularity in the diesel engine. Their results seem to contradict, in some respects, those of Wing [56] concerning correlations. Kouremenos et al [42] have made an extensive investigation of this phenomenon in a single-cylinder DI engine operating on diesel fuel, at various loads and injection timings, using stochastic techniques, and found no correlation between cyclic pressure variations and the injection system.…”

“…The result of the analysis is that neither the injection process (through the dynamic injection timing), in contrast to the findings of Wing [56] for a special rotary-type fuel pump used, nor the kind of fuels used (through their cetane numbers) have any practical effect on the above cyclic variations, with the latter one being in accordance with the findings of Sczomak 16 Correlation coefficients between dynamic injection timing and maximum rate of pressure rise, dynamic injection timing and ignition delay, ignition delay and maximum rate of pressure rise, and maximum cylinder pressure and maximum rate of pressure rise, as a function of load, for the neat diesel fuel and the 24 per cent n-butanol in the blend cases and Henein [58] that can be attributed to the rather low contents of n-butanol in the blends.…”

“…16. The dynamic injection timing was chosen [56] as potential 'cause' of any influence of the injection process on the cyclic variation, while the ignition delay was chosen as corresponding potential 'cause' of any influence of the fuel via its cetane number [58]. Table 3 summarizes the values of mean (AVER) and standard deviation (SDEV) for the maximum cylinder pressure (PG), maximum cylinder pressure rate (DPG), dynamic injection timing (DINJ), and ignition delay (DIGN), for the net diesel fuel and the Bu24-D blend cases at the four engine loads considered.…”

“…A short literature review for this phenomenon in diesel engines has been presented by Rakopoulos et al [30], which deals with the engine in hand, the same operating conditions but with ethanol/diesel fuel blends. Wing [56] was the first to deal, in depth, with this aspect of diesel engine operation, and his experimental study concerns a multi-cylinder, fourstroke, DI diesel engine fitted with a rotary fuel injection pump, which was suspect as the source of cyclic pressure variation. Koizumi et al [57] dealt with a two-stroke IDI (indirect injection) diesel engine trying to connect the irregularity of injected fuel mass with the cycle-by-cycle variation of the indicated mean effective pressure.…”

A stochastic-experimental investigation of the cyclic pressure variation in a di single-cylinder diesel engine

“…Important studies of the cycle-by-cycle variations of pressure in diesel engines have been reported by Koizumi et al (1977), Sczomak and Henein (1979), and Wing (1975). Wing (1975) was the first to deal, in depth, with this aspect of diesel engine operation, and his experimental study concerns a multicylinder, four-stroke, DI diesel engine fitted with a rotary fuel injection pump which is suspected as the source of cyclic pressure variation. Koizumi et al (1977) deal with a two-stroke ID1 diesel engine trying to connect the irregularity of injected fuel mass with the cycle-by-cycle variation of the indicated mean effective pressure.…”