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In this study, port premixed methanol compression ignition combustion was performed on a heavy-duty diesel engine. The effects of methanol to diesel ratio (R MD ) and DIT (diesel injection timing) on combustion, performance and emissions were comprehensively investigated. The experimental results demonstrated that R MD and DIT played important roles in combustion and emission control. With the increasing R MD , the ignition delay was prolonged and the combustion duration was shortened. And as DIT retarded, the ignition delay was also prolonged and the combustion duration basically remained unchanged at the beginning, and then followed by a slight decrease. The maximum in-cylinder mean temperature decreased with the retarding DIT and it was largely affected by the combine of R MD and DIT. The brake thermal efficiency remained stable at low R MD , but showed a slight decrease at high R MD. NO X and soot emissions and the RI (ringing intensity) were all decreased as RMD increase, while HC and CO emissions increased significantly. With the retarding DIT, HC emission firstly increased and then decreased, while CO emission always increased. It was more important that the trade-off relationship between NO X and soot was significantly improved with the increasing R MD and almost disappeared at R MD 1.54. [ABSTRACT FROM AUTHOR]

The combustion and emission characteristics of a dual fuel diesel engine with high premixed ratio of methanol (PR m ) were investigated. Experiments were performed on a 6-cylinder turbocharged, inter-cooling diesel engine. Methanol was injected through the intake port and ignited by direct injected diesel in the cylinder, the maximum PR m was over 70%. The experimental results showed that with high PR m , the maximum in-cylinder pressure increased from medium to high engine load but varied little or even decreased at low engine speed and load. High PR m prolonged the ignition delay but shortened the combustion duration and decreased the in-cylinder gas temperature at ignition timing. Hydrocarbons (HC), carbon monoxide (CO), formaldehyde emissions and the proportion of nitrogen dioxide (NO 2 ) in nitrogen oxides (NO X ) increased significantly with the increase of PR m while NO X and dry soot emissions were significantly reduced, which meant the trade-off relationship between NO X and soot emissions disappeared. The increased HC, CO and formaldehyde emissions could be effectively reduced by diesel oxidation catalyst (DOC) when the exhaust gas temperature reached the light off temperature of the DOC. After DOC, the NO 2 proportion in NO X was greatly reduced to less than that of baseline engine at methanol premixed mode but increased slightly at pure diesel mode. The maximum PR m was confined by in-cylinder pressure at high engine speed and load. But at low engine speed and load, it was confined by the high emissions of HC, CO and formaldehyde even after DOC. [ABSTRACT FROM AUTHOR]

An experimental study was conducted to investigate the operating range and combustion characteristics in a methanol fumigated diesel engine. The test engine was a six-cylinder, turbocharged direct injection engine with methanol injected into the intake manifold of each cylinder. The experimental results showed that the viable diesel methanol dual fuel (DMDF) operating range in terms of load and methanol substitution percent (MSP) was achieved over a load range from 6% to 100%. The operating range was restricted by four bounds: partial burning, misfire, roar combustion and knock. The lower bound of the operating range was the partial burn bound, which occurred under very low load conditions with high MSP. As the load increased to medium load, MSP reached its maximum value of about 76%, and the onset of misfire provided the right bound for normal operation. At medium to high load, maximum MSP began to decrease. DMDF combustion with excessive MSP was extremely loud with high pressure rise rate, which defined the roar combustion bound. As it increased to nearly full load, measured pressure traces in-cylinder showed strong acoustic oscillations. The appearance of knock provided the upper bound of the operating range. In general, as the load increased, the characters of the combustion changed from partial burn to misfire to roar combustion and to knocking. The range between these four bounds and the neat diesel combustion bound constituted the viable operating range. Over the viable operating range, DMDF combustion worsened the brake thermal efficiency (BTE) at light load while boosted it at medium and high load. [ABSTRACT FROM AUTHOR]

Highlights: [•] PM and dry-soot from turbo-charged diesel engine with DMDF were measured. [•] Relation on dry-soot emission and PM was analyzed. [•] Effects of DMDF, DOC and intake air temperature on PM and dry-soot were investigated. [•] Particle number and mass concentration on different loads with DMDF were realized. [ABSTRACT FROM AUTHOR]

A number of measurements have been provided to detect formaldehyde in the atmosphere, but there are no clear unified standards in engine exhaust. Nowadays, formaldehyde, an unregulated emission from methanol engine, has been attracting increasing attention by researchers. This paper presents the detection techniques for formaldehyde emitted from the engines applied in recent market, introducing the approaches in terms of unregulated emission tests of formaldehyde, which involved gas chromatography, liquid chromatography, chromatography-mass spectrometry, chromatography-spectrum, Fourier infrared spectroscopy and spectrophotometry. The author also introduces the comparison regarding to the advantages of the existing detection techniques based on the principle, to compare with engine exhaust sampling method, the treatment in advance of detection, obtaining approaches accessing to the qualitative and quantitative analysis of chromatograms or spectra. The accuratest result obtained was chromatography though it cannot be used continuously. It also can be utilized to develop high requirements of emissions and other regulations. Fourier infrared spectroscopy has the advantage of continuous detection for a variety of unregulated emissions and can be applied to the bench in variable condition. However, its accuracy is not as good as chromatography. As the conclusion, a detection technique is chosen based on different requirements. [ABSTRACT FROM AUTHOR]

This study is aimed to investigate the combined application of diesel methanol dual fuel (DMDF) and a simple after-treatment for reducing particulate matter (PM) emissions of a diesel engine. The effects of DMDF, a double diesel oxidation catalyst (DDOC) and a DOC closely coupled with a particulate oxidation catalyst (POC) in series (DPOC) on smoke emissions, particulate mass and number concentrations and size distributions were analyzed. Tests were conducted on a 4-cylinder turbo-charged, inter-cooling, mechanical in-line fuel injection pump diesel engine modified to DMDF combustion mode. Testing results showed that, before the DDOC and the DPOC, the dry-soot and smoke opacity efficiency decreases with the increase of substitution ratio of methanol at high engine load. There is a significant decrease of smoke opacity in DMDF mode after the DDOC, while the DPOC has a significant effect on the reduction in dry-soot emission. There is an average reduction in dry-soot by 25% in pure diesel fuel mode after the DDOC, while in DMDF mode, the average reduction is more than 60%, and the maximum reduction in dry-soot is up to 96%. There is a slightly reduction in PM emissions at low substitution ratio of methanol, while the high substitution ratio of methanol leads to more reduction in PM emissions. After the DDOC and the DPOC, particulate number and mass concentrations, especially nuclear particles, can be significantly reduced when the exhaust gas temperature is enough high. [ABSTRACT FROM AUTHOR]