Investigation On Physico-chemical Properties Of Methanol-diesel Blended Fuels And The Effects On Carbonyl Emissions From Diesel Engine

Although methanol/diesel blended fuel could reduce the regulated emissions from diesel engines, the carbonyl compounds (carbonyl) emissions were usually higher than conventional diesel fuel, which had negative impact on both environments and human beings. Therefore, it was essential to establish a systemic method to detect the carbonyl emissions and investigate the characteristics of carbonyl emissions from engines fueled with methanol/diesel blends. In this study, four different methanol/diesel blended fuels were prepared by means of adding the co-solvent and cetane booster. The physico-chemical properties of the blended fuels and the influence on engine performance were studied. Additionally, a method combining derivative sample pretreatment and high-performance liquid chromatography (HPLC) analysis technology had been used for determining the 13 kinds of aldehyde and ketone emissions. The effects of mixture ratio, engine speed and load on carbonyls emissions were evaluated. The major achievements are listed as follows:1) The macromolecule alcohol and nitric acid ester were used as additives, which could improve the dissolvability of the methanol in the diesel and enhance the cetane number, respectively. The tests with regard to physico-chemical properties of the methanol/diesel blends proved that the blended fuels prepared could meet the nation application standard of diesel fuel except for flash point.2) The derivatization method has the advantage of strong selectivity and the sampling efficiency of the solid adsorbent cartridge was more than 93%. Analyte identification and quantification of hydrazone derivatives were performed using HPLC. The linear range were 0.0021-13.333μg/mL, and the limits of detection were in the range 0.6~2.7ng/mL.On the other hand, the relatively standard deviation of parallel samples were 0.1~1.07% and the recoveries were 87.5% ~115.0%.3) The engine experimental results indicated that without any modification on the diesel engine, the power decreased with an increase of methanol content in the blends. Compared to neat diesel fuel, the brake specific fuel consumption (BSFC) grew up to some extent with the blended fuels. The brake specific energy consumption (BSEC) increased at low load, while at medium/high load, the BSEC were equivalent. As to the carbonyl emissions, it was found that whether neat diesel fuel or the methanol/diesel blends were burned, formaldehyde and acetaldehyde were abundant in carbonyl emissions. The highest brake specific formaldehyde and acetaldehyde were 93.6 and 159.3 mg/(kW·h), which predominated 1.1 and 2.1 times of that using diesel fuel, respectively. The more methanol in fuels, the more acetone emission. Acrolein emission had a link with engine speed and generally higher at high speed. The variable trends of other carbonyls were not obvious. With the increase of engine load, the total brake specific carbonyls reduced.