Formation History Of Carbonyl Compounds During Combustion Process Fueled With Alcohols-diesel Blends

Formation history of carbonyl compounds has been investigated fueled with alcohols-diesel blends to obtain scientific means for controlling carbonyls emission. The experiments was carried out on the total cylinder dumping system fueled with methanol-diesel blends(M8,M13)and ethanol-diesel blends(E10,E20), and the indicator diagram was measuring. Meanwhile, the cylinder gas during combustion process has been gathered to analyse 14 kinds of carbonyl compounds by high-performance liquid chromatography. The major conclusions aimed at the combustion process and formation process of carbonyl compounds are listed as follows:1. Compared with neat diesel fuel, the maximums of cylinder pressure and temperature increased 5.3% and 1.1% for M8 and 4.9% and 3.2 % for M13 respectively. In addition, the ignition time advanced and heat release rate enhanced with the usage of M8 and M13, and the peak values in the plots of heat release rate increased 19.9% for M8 and 16.6% for M13 relevant to diesel fuel. As for ethanol -diesel blends, the maximum of cylinder pressure and temperature increased 7.18% and 4.01% for E10 and 16.75% and 8.92% for E20 respectively, and the corresponding crank angle varied from 5oCA (ATDC) to 4oCA (ATDC) and 3.5oCA (ATDC). The thermal efficiency of diesel engine was also improved for alcohols-diesel blends due to the advancement of ignition time and the increase of heat release rate.2. For the methanol-diesel blends, formaldehyde and acetaldehyde were the most abundant in carbonyl compounds during combustion process, followed by acrolein, propionaldehyde, butyraldehyde, cyclohexanone, p-tolualdehyde and hexaldehyde, and together accounted for 90% of total carbonyl compounds. Other carbonyl compounds were occasionally present in the samples. Peak value of 14 species carbonyls contents occurred in the highest cylinder temperature phser(10 oCA ATDC～14 oCA ATDC), and then the contents for these compounds declined with the combustion going on.3. The variation of carbonyl compounds for ethanol-diesel blends was similar to that for methanol-diesel blends. That is to say, the dominant aldehydes during combustion process also were formaldehyde, acetaldehyde, acrolein, acetone, propionaldehyde, butyraldehyde, cyclohexanone, p-tolualdehyde and hexaldehyde in turn, together accounted for 90% of total carbonyl compounds. The contents of 14 kinds carbonyls in combustion end phase was less than those in combustion initial phase, especially, formaldehyde and acetaldehyde only were 33.6 %. From18 oCA ( ATDC) to 50 oCA (ATDC), a decreasing trend was observed for the 14 kinds carbonyls .