The Influence Of Coal-to-Oil Fuels On Combustion And Emission Characteristics In Compression Ignition Engine

With the increasing worldwide-attention to energy conservation,emission reduction and low-carbon economy,emission regulations and fuel consumption regulations have become increasingly stringent.In order to meet stringent emission and economic regulations,exploring the highly efficient and clean combustion technology of internal combustion engines has become the focus of research among researchers in the field of combustion of internal combustion engines.For the most of those technologies,the application of clean alt ernative energy can alleviate the shortage of resources in a way,and it is also an effective method to reduce the emissions of vehicle particles.As one of the main petroleum alternative fuels,coalto-liquid oil has become mature in technology and commercial operations,and it has a good application prospect as an alternative fuel for internal combustion engines.This research relies on the National Natural Science Foundation of China,for the purpose of meeting continuously increasing the demand for fuel oil and the stringent requirements.In order to explore efficient and clean alternative fuels for diesel vehicles and simultaneously reduce diesel engine nitrogen oxides(NOx)and ultra-fine particles,a study was conducted on the composite control technology of coal-based Fischer-Tropsch synthesis diesel(Coal-toOil,CTL),EGR and injection parameters.The influence of CTL on the performance,combustion and emission characteristics of the compression ignition engine is experimentally studied and compared with the national V petrochemical diesel.Through the fuel desig n,the mixed fuels of CTL,petrochemical fuels and ester oxygenated fuels were prepared,and the effects of different physical and chemical characteristics of fuels,the boundary conditions such as EGR and injection parameters on combustion and emissions are experimentally studied.Research results indicate:1.The physicochemical properties and proportion of fuel have a significant impact on engine performance,combustion process and emission characteristics.Compared with ordinary petrochemical diesel,the CTL engine torque is slightly reduced while economic efficiency is improved.CTL fuel has a good ignition in the combustion process,a short ignition delay period,reduced pressure rise rate,and has a positive effect on relieving diesel engine work rough and improving engine work stability.2.CTL fuel can reduce the emission of CO,HC,NOx and extinction smoke.The concentration of each modal particle and the concentration of total particulate matter are lower than that of National V diesel.Compared with the ordinary petrochemical diesel,the ECE R49 13-mode test cycle weighted average specific emissions of CO,HC,and NOx of CTL fuel are respectively reduced by 51.42%,45.62%,and 14.35%,and the extinction smoke reduction range is 33.33% to 80%.The concentration of nuclear particulates and total particulates in emissions can be reduced by more than 45%.3.With the introduction of recirculated exhaust gas(EGR),CTL's NOx is significantly reduced,and the use of CTL is more tolerant to the introduction of EGR to increased extinction smoke than National V diesel.Under the same EGR rate,the NOx,extinction smoke,and particle concentration in different particle size ranges of CTL are all lower than those of petrochemical diesel.4.For transient conditions,the NOx emissions of CTL is significantly lower than those of petrochemical diesel fuels.The peak smoke level of CTL in the early stage of the loadincreasing process is nearly 50% lower than that of the National V diesel fuel.At the end of the load-increasing process,the extinction smoke of CTL fuel is reduced by 44.50% when EGR is not introduced,and the extinction smoke reduction of CTL is 63.76% when EGR is introduced.Therefore,it can be found that the sensitivity of extinction smoke of CTL on transient conditions is lower than that of National V diesel,meanwhile the tolerance to EGR is better than that of transient process.5.The use of CTL as an additive in combination with ordinary petrochemical diesel can improve the physical and chemical characteristics of common petrochemical diesel,help improve economic efficiency,combustion,and reduce emissions of pollutants.At the same time,it can solve the problem of insufficient power of pure CTL fuel.Properly increasing the injection pressure and introducing a large proportion of EGR can simultaneously reduce the NOx emissions and particulate emissions of CTL/National V diesel mixed fuels.Compared with National V diesel,C60 which has 60% CTL fuel can achieve good performance and emission levels.Under the conditions of 120 MPa injection pressure and 30% EGR rate,the C60 NOx and extinction smoke reductions are respectively 9.42% and 27.27%.6.The addition of oxygenated fuel DMC contributes to further reduce CO,HC and particulate emissions of CTL fuel.In term of D15 fuel with 15% DMC,CO,HC,and extinction smoke decreased by 47.62%,62.07%,and 54.26% respectively,but NOx emissions increased by 10.28%.The introduction of EGR can further reduce NOx emissions and can reduce NOx emissions by nearly 75% under 30% EGR rate.At the same time,the use of D15 fuel can improve the degree of particulate emission degradation caused by the introduction of EGR.Compared with pure CTL,the extinction smoke and total particle concentration of D15 fuel respectively decreased by 61.17% and 42.76% under the same EGR rate(30%).It can be seen that by adjusting the CTL fuel characteristics to coordinately control the boundary conditions such as EGR and fuel injection parameters,the nitrogen oxides and part iculate emissions of the engine can be reduced at the same time,the contradictory relationship between the NOx and particulates of the diesel engine can be alleviated,and the efficient and clean utilization of the CTL fuel on the internal combustion engine can be promoted.