Experimental Investigation of Combustion and Emission Characteristics of the Direct Injection Dimethyl Ether Enabled Micro-Flame Ignited (MFI) Hybrid Combustion in a 4-Stroke Gasoline Engine

Fu, Xue-Qing; He, Bang-Quan; Xu, Si-Peng; Li, Hongtao; Chen, Tao; Zhao, Hua

doi:10.4271/2018-01-1247

Cited by 4 publications

(4 citation statements)

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“…Comparing with the results in Figures 8 –10, it is found that the highest thermal efficiency is not obtained at the lowest HC and CO emissions in the MFI combustion. Ignition timing occurring around TDC and short combustion duration contribute to the increase of expansion work and hence improving the thermal efficiency, 23 although HC and CO emissions are slightly higher.…”

Section: Resultsmentioning

confidence: 99%

“…20 Besides, its lack of C–C bonds and high oxygen content can achieve soot-free combustion due to low formation and high oxidation rates. 21 When injected into the premixed high octane fuel and air mixture, DME can ideally provide multiple auto-ignition sites to control and accelerate the ignition and shorten main combustion processes in a lean-burn mixture, which leads to the research and development of multi-point micro-flame-ignited (MFI) hybrid combustion, 22,23 in which multi-point flames are formed by auto-ignition of directly injected DME, and its released heat induces the auto-ignition of unburned premixed gasoline mixture. As reported earlier, direct injection (DI) of DME can enhance flame propagation in the early stage of combustion 24 and directly trigger auto-ignition of premixed gasoline mixture with hot burned gases through exhaust throttling, 25 or intake re-breathing by pilot intake valve open during the exhaust stroke.…”

Section: Introductionmentioning

confidence: 99%

“…Effects of single and split DI of DME on the MFI combustion were experimentally investigated at part loads when the first injection timing of DME is kept at −220 °CA ATDC and the second injection timing of DME is changed in the range from −60 °CA to −40 °CA ATDC at an excess air coefficient (Lambda) of 1.6. 22,23 Although the thermal efficiency of the gasoline engine in MFI combustion is higher than that in SI combustion, the raw NOx emissions in MFI combustion are generally in the range from 300 to 400 ppm. 22,23…”

Section: Introductionmentioning

confidence: 99%

“…22,23 Although the thermal efficiency of the gasoline engine in MFI combustion is higher than that in SI combustion, the raw NOx emissions in MFI combustion are generally in the range from 300 to 400 ppm. 22,23…”

Section: Introductionmentioning

confidence: 99%

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Multi-point micro-flame ignited hybrid lean-burn combustion of gasoline with direct injection dimethyl ether

et al. 2019

International Journal of Engine Research

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Lean-burn combustion is effective in reducing fuel consumption of gasoline engines because of the higher specific heat ratio of the fuel lean mixture and reduced heat loss from lower combustion temperature. However, its application to real engines is hampered by the unstable ignition, high cyclic variability, and partial-burn due to slower combustion, as well as the restricted maximum lean-burn air/fuel ratio limit and the insufficiently low nitrogen oxides emission. Multi-point micro-flame-ignited hybrid combustion has been proposed and applied to extend the lean burn limit of premixed gasoline and air mixture. To achieve micro-flame-ignited combustion in premixed lean gasoline mixture formed by port fuel injection, a small amount of dimethyl ether is injected directly into the cylinder of a four-stroke gasoline engine to control and accelerate the ignition and combustion process so that the engine could be operated with the overall excess air coefficient (Lambda) of 1.9. The results show that heat release processes can be grouped into three forms, that is, ramp type, double-peak type, and trapezoid type. Regardless of single or split injections, direct injection timing of dimethyl ether dominates the features of heat release. The ramp type occurs at early injection timing while the double-peak type takes place at late injection timing. Trapezoid type appears between the above two types. Dimethyl ether injection timing controls the ignition timing and has less effect on combustion duration. Single injection of dimethyl ether leads to much earlier ignition timing and slightly longer combustion duration, forming higher nitrogen oxides emissions than the split injections. Ultra-low nitrogen oxides emissions and higher thermal efficiency are achieved in the ramp type combustion compared to the other two types of combustion in both injection approaches.

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Section: Resultsmentioning

confidence: 99%