Zhi Xia He

Simulation Research on Matching of Spray and Combustion Chamber Geometry in Diesel Engine

In order to investigate the influence of combustion chamber geometry on spray and combustion characteristics in diesel engine, universal CFD software STAR-CD is applied to simulate the combustion processes in three different types of combustion chambers of diesel engine. The effect of combustion chamber geometry on in–cylinder air motion, temperature field and exhaust emissions are researched in this paper. Comparing with experimental results, calculation models are proved to be validity. The results show that differences of combustion chamber shape change the characteristic of flow field in cylinder, which affects the formation of mixed gas and determines the combustion and emission characteristics.

Effect of Diesel Nozzle Geometry on Internal Cavitating Flow

The presence of cavitation and turbulence in a diesel injector nozzle has significant effect on the subsequent spray characteristics. However, the mechanism of the cavitating flow and its effect on the subsequent spray is unclear. The initiation, development and collapse of the cavity are strongly influenced not only by the injection pressure and back pressure but also by the nozzle geometry. The numerical simulation of cavitating flow in nozzle holes of a vertical multi-hole injector with mixture multi-phase cavitating flow model was carried out. The effects of sac geometry, hole entrance curvature radius and hole inclination angle on the cavitating flow in nozzle holes were investigated. It is finally concluded that the performance of IMPROVED nozzle is better than that of STD nozzle and VCO nozzle and small inlet turning angle of the orifice can enhance the atomization of the spray.

Finite Element Analysis of High-Pressure Common-Rail Injector Body

The high pressure common rail injection System is one of the most advanced technologies for the diesel engine to reduce fuel consumption exhaust emissions. While the design of the high pressure common rail injector is the key for the whole system. Considering that the working pressure of fuel in the injector, a more accurate injector body model was established with the modeling software Pro/Engineer in this study. Finite element analysis technology in Ansys software was applied to calculate the strength of injector body of the high pressure common rail system under different injection pressures. And then the rationality of structure parameters and material selection of the injector body can be analyzed and verified. The research conclusions can provide the theoretical basis for the optimization design of the injector.

Study on Catalytic Combustion Characteristics of Hydrogen inside Micro Scaled Tube

Catalytic combustion of hydrogen/air mixture inside micro-tube was numerically investigated with detailed gas phase and surface catalytic chemical reaction mechanisms. Combustion characteristics for different reaction models, inlet velocity, tube diameter on surface catalytic combustion reaction, and comparison of numerical and experimental studies were discussed. The Computational results indicate that the surface catalytic combustion restrains the gas phase combustion. The effect of the surface catalytic reaction on the gas phase reaction can be divided to three types. The existence of catalytic wall will help to reach complete reaction in the micro-tube. Some theoretical evidences are provided for the application of catalytic combustion to Micro-electromechanical System (MEMS) and the extension of the combustion limits.

Influence of Piston Initial State on HCCI Combustion in Micro Free-Piston Engine Using Experiment Images and CFD Analysis

The visualization experimental setup of micro free-piston engine has been built, the process of single shot compression combustion in micro combustion chamber has been observed by the high-speed digital camera; Based on the propane combustion kinetics, the numerical calculation method for combustion process coupling with the free-piston movement was put forward, through editing the dynamic mesh subroutine in STAR-CD, the process of homogeneous charge compression ignition (HCCI) in the micro chamber was studied; The influence of piston initial state on HCCI combustion process was analyzed , indicating that the piston mass directly affects the homogeneous gas compression ratio, ignition time, single combustion process cycle and the changes of combustion pressure and temperature, all this research can be the basic theories for designing the micro free piston engine .

Numerical Investigation on Water Flow in Engine Cooling-Water Jacket

The engine cooling water jacket has a major impact on the efficiency of the engine. In this paper the flow in the cooling water jacket of the six-cylinder four stroke water-cooled diesel engine was studied with the commercial software of STAR CCM+. Results of the simulation reveals that velocity has little effect on the flow field distributions. Dead zone in engine cylinder head appeared far away from the inlet of the flow. But it could be avoided or improved effectively by arranging the inlet and outlet at opposite side of the cooling water jacket. Further study suggests that a good flow field distribution can be achieved near the entrance if one inlet was put at the same side of the outlet and the other the opposite side, while the wall was impacted fierce due to the strong turbulence and eddy existed. Finally some advices were given to solve the problem.

Measurement of Diesel Nozzle Geometry with X-Ray Phase Contrast Imaging Technique

Diesel spray characteristic s is affected by nozzle geometry and then influences the subsequent combustion and emission, so its important to get the detail nozzle geometry dimensions. In this paper, the X-Ray phase contrast imaging technique was proposed to measure the nozzle geometry. With X-microtomography technique and three-dimension reconstruction technique, the internal structure of nozzle is constructed. The non-destructive measurement was performed and the detail structure of nozzle was got.

Numerical Study on Effect of Injection Rates on Combustion and Emission Performance

As a study of natural gas engine, three-dimensional numerical simulations of diesel injection rates were conducted by using AVL FIRE code. And particularly the effects of the injection rates in the pilot diesel jets on the engine combustion and emission were analyzed. It is found that injection rate in the pilot diesel jets plays an important role on the emission, and slow ending rate of the injection keeps lower NO and Soot.

Measurement of Thermal Conductivity of Liquid Based on Transient Double-Hot Wire Technique

A new experimental apparatus has been developed for measuring the thermal conductivity of liquid by the two transient hot-wire method, which is based on the theory of one-dimensional unsteady heat conduction in infinite medium. The glass tubes, the heating line source and temperature measurement devices are designed in this experiment. As the temperature controller, low-temperature bath provides a constant water bath environment and current calibrator is the power source. Wheatstone bridge is used to test the relation between the temperature changes and resistance. Data acquisition and control unit is data acquisition devices of the Wheatstone bridge. As the temperature coefficient of platinum wire resistance is calibrated. It can be used to measure 32 groups of data from 10°C to 40°C at the every 10°C according to the experimental steps.

Numerical Investigation of Effect Pilot Injection on Combustion Noise and Exhaust Emission of Diesel Engine

Numerical Investigation of Effect Pilot Injection on Combustion Noise and Exhaust Emission of Diesel Engine The traditional mechanical fuel supply system has already been no way to satisfy the requirement of more stringent fuel consumption and emission legislation. For the past few years, it has been a hot topic to improve performance of diesel engine combustion and emission through optimizing the fuel injection strategy. All kinds of spray, combustion and emission models were studied and then the numerical models for the single-injection combustion of 1015 diesel engine were setup and validated through comparing with results from experimental data. With the above verified models, different injection strategies were further investigated to get the effect mechanism of pilot injection (PI) timing and quantity on combustion noise and exhaust emission.