Research on Clean Combustion Technology of EGR-based Flameproof Diesel Engine

In view of the serious pollution of NOx emissions from flame-proof diesel engines used in coal mines and its direct and indirect hazards that cannot be ignored, the combustion process of flame-proof diesel engines is analyzed and a combustion mathematical model is established. Subsequently, the clean combustion method based on exhaust gas recirculation (EGR) is adopted, and an EGR clean combustion device is designed, which meets the requirements of the coal mine standard Safety Regulations on Coal Mine . The design content involves: (i) Composition and structure design of EGR system meeting the requirements of flame-proof standards; (ii) The closed forced cooling cycle design of the EGR system. Specifically, the clean combustion process of flame-proof diesel engine based on EGR system is simulated and analyzed by fluid simulation analysis software, and the effects of EGR system on the performance and emission of flame-proof diesel engine under 15 operating modes of three rotational speeds and five loads are obtained. Then, the control strategy and control program of the EGR system of flame-proof diesel engine are compiled based on the mathematical model and simulation results. In addition, the bench test of the flame-proof diesel engine equipped with EGR device is carried out by using this control program in the laboratory, and the control program of EGR system is modified by analyzing the experimental data. Finally, the optimized bench test is carried out by selecting the control program that optimal matches the flame-proof EGR device and the flame-proof diesel engine. The test results suggest that: (i) Under the external characteristic working mode: after installing the EGR system, the power of the flame-proof diesel engine is 58.9kW under the optimized EGR opening, and the highest output torque is 252.3 Nm, and the power performance is slightly lower than that of the original engine; (ii) Under eight operating mode: after installing the EGR system, the weighted average CO emission of the flame-proof diesel engine under the optimized EGR opening is 0.0045%, and the volume concentration is increased by 0.0045% compared with that without the EGR system; the weighted average NOx emission of the flame-proof diesel engine under the optimized EGR opening is 93.35ppm, which is 56.17% lower than that without the EGR system, indicating that the EGR system technology has significantly improved the reduction of NOx emissions of the flame-proof diesel engine; (iii)Under eight operating mode: after installing EGR system, the HC emission of flame-proof diesel engine under optimized EGR opening is basically unchanged compared with that without EGR system, and the soot emission is slightly increased; and (iv) The EGR system meets the requirements of the coal mine standard, and this method and technology can improve the basis for reducing the NOx emission from the tail gas of the underground vehicles in the coal mine.