| In recent years, the underground rail transportation with explosion-proof diesel engine as the traction force has gradually become the mainstream. However, the diesel engine that the intake and exhaust system has been transformed to explosion-proof, will lead its power and emission characteristics can not be considered at the same time, especially the particulate matter emissions greatly increased. That is bound to threaten the physical and mental health of the staff in the mine, so it is urgent to improve the in-cylinder combustion process of the explosion-proof diesel engine and reduce the discharge of pollutants.PODE/methanol compound combustion mode has changed the traditional diesel engine’s in-cylinder combustion form, improved the content of combustion, and then improved the effective thermal efficiency. To some extent, it makes up the loss of power characteristics of explosion-proof diesel engine, and the combustion mode can largely reduce the particulate matter emissions. However, there is a large emission problem on CO and THC in the small load and a rough running problem in the heavy load.The high octane methanol was injected to the intake port to form the pre-mixture, which was ignited by the high cetane polyoxymethylene dimethyl ethers in the cylinder. Using methanol high antiknock and large latent heat of vaporization and PODE excellent ignition performance to widen the load limit of methanol in the explosion-proof diesel engine. The engine bench test was carried out to change the combustion processes by adjusting the factors of the methanol proportion, compression ratio, test fuel, fuel supply advance angle, as much as possible to reduce emissions in ensuring the premise of power by installing exhaust gas recycling and oxidation catalytic converter. The results show that PODE/methanol dual fuel combined combustion achieves the low particles emission and the effective thermal efficiency is slightly higher than the level of the original machine in the high load, the rough combustion under high load can be controlled greatly by reducing compression ratio and combining with EGR. The reduction of CO and THC emissions is more than 30% by using the DOC device, the change of fuel supply advance angle can improve the in-cylinder combustion process to a certain extent.Through the analysis of cylinder pressure oscillation and combustion noise, it is known that the influence of methanol proportion on that is related to the engine load. If the load is different, the combustion temperature in the cylinder will be different. The cylinder temperature is low in the small load, so it is very easy to cause pressure oscillation because of combustion instability. Under the heavy load, the combustion process in the cylinder is violent, the pressure rise rate rose sharply, which caused the pressure oscillation and the combustion noise, but the pressure oscillation and combustion noise could be reduced obviously by the increase of EGR rate. The effects of methanol proportion, compression ratio and fuel supply advance angle on the combustion and emissions characteristics were analyzed by means of orthogonal test method, the research shows that the proportion of methanol has great influence on it.The combined combustion mode was successfully applied to the explosion-proof diesel engine, and the corresponding measures were adopted to realize the application of dual fuel based coal in the explosion-proof diesel engine. It not only achieved the purpose of energy saving and emission reduction, but also achieved high efficiency of fuel based coal cleaning utilization, to provide a theoretical basis for the application of dual fuel combination combustion in explosion-proof diesel engine. |
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