Combustion And Emission Characteristics Of Flameproof Diesel Engine Fueled With F-T Diesel-PODE-methanol Mixed Fuel

Compared with the conventional diesel engine, the flameproof diesel engine installs intake fire barrier, exhaust water tank and exhaust fire barrier, which will increase the exhaust back pressure of the flameproof diesel engine, and affect the scavenging process, finally deteriorate combustion and emissions. This paper aims to improve the combustion and emissions of flameproof diesel engine by three measures, pre cleaning, machine cleaning and after cleaning. Coal chemical products PODE(Polyoxymethylene dimethyl ethers) and methanol are high oxygen fuel, which can make up the shortage of air intake, improve combustion and reduce pollutant emissions. Three different proportions of stable coal based mixed fuels, containing F-T diesel, PODE and methanol, were prepared by adding the auxiliary solvent. The combustion and emission characteristics of the mixed fuel in flameproof diesel engine were studied in the engine bench test by changing compression ratio, fuel supply time, EGR rate and DOC post treatment measures at n=1200r/min, BMEP=0.30 MPa, n=1800r/min, BMEP=0.30 MPa, 0.50 MPa three conditions. The results show that:(1)The increase of methanol proportion in the mixed fuel can increase the heat release rate and the pressure rise rate of the mixed fuel. The ignition delay period of 3# mixed fuel is shorter than that of 0# diesel and F-T diesel, and the heat release rate is close to or even more than 0#. The emission of PM, NOx, CO and SO2 of the coal based mixed fuel in the flameproof diesel engine was lower than that of 0# diesel engine with a maximum of 77%, 16%, 74% and 98%, but HC and HCHO emissions are higher than 0# diesel by 27% and 71%. The CoVpmax of 3# mixed fuel on flameproof diesel engine is 20% lower than that of 0# diesel at high load condition. The economic performance of the flameproof diesel engine fueled with coal based mixed fuel was slightly worse than that of the 0# diesel and F-T diesel because of the low calorific value of PODE.(2)Advancing fuel supply time can improve the combustion temperature, pressure rise rate and heat release rate of 3# mixed fuel. Increasing the compression ratio can shorten the ignition delay period and reduce the heat release rate. Advancing fuel supply timing, reducing compression ratio can extend the ignition delay period, and decrease PM by 90%, 75% when using 3# mixed fuel. The impact of fuel supply time on NOx, HC and CO emissions is not obvious.(3)Increasing EGR rate can extend the ignition delay period, and decrease PM by 71% when using 3# mixed fuel. After using EGR, the maximum combustion temperature is reduced by 72 K, and the average temperature is reduced by 12 K, and the maximum reduction of NOx is 97%. The HC is lower than 0# diesel after using DOC.The low emission of F-T diesel-PODE-methanol coal based mixed fuel on flameproof diesel engine makes up for the shortage of economy, work in with EGR low temperature combustion and DOC after treatment can overall reduce harmful emissions. Coal based clean mixed fuel has great potential to solve the flameproof diesel engine emission problem.