According the actual structure and working principle of a fuel injector to build a model of the common-rail injector, including the control valve, the solenoid valve, and the needle valve of the injector. The model includes the leakage model for the control piston and needle valve that takes into account increasing leakage at high pressure. The performance of the fuel injector is investigated using a one-dimensional numerical model. Analyzing the effect of the system and structure parameters including common-rail pressure, injection pulse width, inlet and outlet hole diameter, and the injection nozzle on the injection characteristics of the fuel injector. Results show that the geometric parameter is the main property affecting the flow characteristic of the injector, which includes the flow rate of inlet and outlet hole, pressure waves in the control chamber and injection rate. The common-rail pressure, injection pulse width and the geometric parameters mainly affect the injection performance, such as the injection rate and injected volume. The investigation result can provide some useful information to improve the injection characteristic in follow-up studies.
Under reduced or micro gravity, bubble dynamic behaviors in liquid melts or liquid solutions are important and common problems on optimizing many processes in space science and technology. Due to limited availability experiments under reduced or micro gravity condition, the studies in this area is still quiet fragmentary. For this reason, we develop two pairs of Helmholtz-Maxwell (H-M) coils, which can produce a uniform gradient magnetic field for the ferrofluid filled in a closed Hele-Shaw cell, so as to achieve reduced or micro gravity condition. Afterwards, we establish the multi-physics mathematic model to calculate the magnetic field and the gravity compensation rate, which shows a 30mm×40mm well-distributed region for 90% gravity compensation rate exists.
The study carries out optimal design for the cam profile of the valve train in a high-specific-power diesel engine. The dynamic analysis on the original cam reveals that the original one, which leads to adequate fullness coefficient, is designed far from the material margins. The fullness coefficient and time area value are selected as the optimization objective, and the piecewise fucntion method is utilized to optimally design the cam profile. The restrictive contidons are applied to each section on the cam. Thus the function and the optimal coeficients are obtained. Then the dynamic analysis and working process simulation on the optimal valve train are carried out, and it proves that the dynamic and intake port performaces of the optimized one are greatly impoved.
In this study the dynamic Smagorinsky model (DSM model) and an algebraic model for the subgrid turbulent kinetic energy have been implemented into KIVA3VLES code to investigate the atomization and evaporation processes of diesel spray in a constant volume vessel. Based on the experimental results of the liquid and vapor phase distributions as well as the results obtained by the differential subgrid scale kinetic energy (K-equation) model, the paper reveals the influence of the turbulent kinetic energy model on the fuel spray prediction. Computational results show that by combining the DSM model and the algebraic subgrid turbulent energy model, the turbulent diffusion of droplets can be reasonably simulated, the liquid penetration and the predicted liquid and fuel vapor mass fraction contours are close to the experiment results. At the same time, the turbulent kinetic energy given by the DSM model is in agreement with the results by the K-equation model, but with less computational cost..
Based on the load and heat radiation area are directly influenced by the ratio of piston stroke to cylinder diameter (S/D).An optimized mathematical model is established, with the minimal heat radiation area as the object function and the S/D value as the variable. The optimum results are calculated by using the an Improved differential evolution algorithm method based on 1Stopt.The result shows that this method is of better convergence, high calculation efficiency and consistent with MTU890.
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