Research On Experiment And Simulation Of Turbocharged Diesel Engine Mixed With Water

Oil shortage and environmental pollution are the two biggest problems influencing engine development. The main measures of the current response are to find clean alternative energy sources, improve the combustion process and take post-processing measures. Diesel mixed with water can improve the combustion process to reduce NOx emissions and improve fuel economy. This thesis focuses on the simulation study of diesel mixed with emulsified water-blended diesel and experimental study of inlet water injection, analyzed the impact of diesel fuel mixed with water to the engine power, economy, emissions and vibration characteristics.This article has set the4100QBZL turbocharged diesel engine simulation model with the software FIRE. By comparing the simulation results and experimental results, the accuracy of the model is proved. Numerical simulation results of water-emulsified diesel show that:water-emulsified diesel can reduce NOx emissions down10%-25%, soot emissions are also ameliorated. But when water blending proportion up to30%, NOx emissions was not changed obviously. The soot emissions was worsening and combustion become severer. Therefore, the appropriate proportion of water in water-emulsified diesel is20%.On the basis of the theory of analyzing combustion of diesel mixed with water, a set of water-injection system was designed with the nozzle fixed in the inlet directly. And the electronic control unit was designed to control the amount of water injection accurately. By tested on the4100QBZL turbocharged diesel engine with different amount of water injection, the result show that inlet water injection can increased the compressed negative power and extended the ignition delay period. With the proportion of water injection increasing, the cylinder temperature of pre-mixed combustion process can also reduced, and NOx emissions reduced by10%-30%. At low speed and low load, CO emissions increased while the soot and HC emissions remained unchanged. In addition engine power and fuel economy improved slightly when injected water in inlet.This thesis also analyzed the tested vibration signal. The Diesel engine cylinder block and cylinder head vibration signal were tested. Then transformed the signal with Fourier amplitude frequency characteristics, and analyzed the affect of water-injection in inlet on engine vibration, combing with the cylinder pressure rise rate. The result show that:with the quantity of inlet water injection increasing, turbocharged diesel engine cylinder pressure increase rate and the vibration of the cylinder block and cylinder head increased. The cylinder block and cylinder head vibration have the same change trend with engine pressure rise rate when change the quantity of the inlet water injection. We can use the vibration signal of the cylinder block and cylinder heads to preliminary analysis the impact of the inlet water-injected on the diesel combustion process.