A sequential port injection, lean-burn, fully electronically-controlled compressed natural gas (CNG)/Diesel dual-fuel engine has been developed based on a turbo-charged and inter-cooled direct injection (D.I.) diesel engine. During the optimization of engine overall performance, the effects of pilot diesel and pre-mixed CNG/air mixture equivalence ratio on emissions (CO, HC, NOx, soot), knocking, misfire and fuel economy are studied. The rich and lean boundaries of the pre-mixed CNG/air mixture versus engine load are also provided, considering the acceptable values of NOx and THC emissions, respectively. It is interesting to find that there is a critical amount of pilot diesel for each load and speed point, which proved to be the optimum amount of pilot fuel. Any decrease in the amount of pilot diesel from this optimum amount results in an increase of NOx emissions, because the pre-mixed CNG/air mixture must be made richer, otherwise THC emissions would increase. However, the soot emissions remain almost unchanged at a very low level.

It is found that a thin and rich mixture layer on a wall is formed after impingement of a gas jet of fuel on the wall. The measured thickness of the mixture layer is about 2mm. and its dispersion rate after the end of injection is much lower, compared to that of a space gas jet. This phenomenon in a small D.I. diesel engine is known as "wall setting" or "wall fuel accumulation" which has an important influence on engine fuel consumption and emissions. This paper presents a technique for enhancing the near wall mixing of an impinging jet by means of a bump on the wall. The development of a wall jet formed after an impingement of a gas jet has been investigated by simultaneously measuring the near wall velocity and concentration distribution. It has been found that a wall jet is stripped off the wall and ejected as a secondary-jet when the wall jet encounters a bump of the wall. Effects of the bump height, the location of the 'bump and the impingement angle are studied at a number of-typical conditions. The distributions of velocity and concentration of a secondary jet are also investigated in detail and the non-dimensional distributions for velocity and concentration of a secondary jet are derived based on the data statistics. In addition, the concept of concentration mean dispersion rate is employed in data processing in order to understand the effects of the bump geometry on mixing rate. It has experimentally confirmed that a controllable mixing process of "space-wall-space" for an impinging jet may be realized by means of a bump setting on the wall.

采用气口顺序喷射、稀燃、全电控柴油/天然气双燃料发动机方案，对斯太尔WD615.64增压非中冷柴油机进行了改装。实验结果表明，改装后的发动机NOx、颗粒和NMHC排放均达到了欧II排放指标。CO和HC（含甲烷）可以通过后处理解决。

利用非线性规划理论，采用Lagrange-SUMT方法建立了电控发动机全工况范围内多变量、多目标的优化模型，并在全电控柴油引燃天然气发动机上进行了应用。实验结果证明，该方法可以减少优化参数的实验量，可以在较少的实验量基础上获得最优控制MAP。发动机的NOx，碳烟排放明显优于欧洲II排放标准，经济性与原柴油机相当。

FIRCRI-a flexible injection rate common rail injector was developed. This paper presents the working principle and the configuration of the injector. As key technologies in development of the injector, a new fast response solenoid valve was developed and 4 dimensionless design parameters of hydraulic system were presented by through computer simulation and experimental study. The solenoid valve was deliberately designed so as to eliminate the hydraulic force acting on the valve. Other configuration parameters were also optimized so that the response time of the solenoid valve is 0.3ms. It is interesting to find that the response time of the injector is not only determined by the solenoid valve, but all parameters of the hydraulic system of the injector. The injector can realize pilot injection, which is less than 2.5mm3, at a controllable phase and multi-injections. The injection rate of the injector can be regulated as echelon and boot shape, according to the requirement fitting engine combustion system by change some parts of the injector.