Applied Mechanics and Materials Vols. 220-223

Abstract: Due to the change of application site, the box beam overhead crane's span needs restructuring. An overhead crane span’s increase restructuring was analyzed by mechanics analysis method. The detailed calculation and feasibility analysis was done. It provides a basic theory for the equipment's restructuring design and analysis work.

Abstract: To reduce the moisture content of coal gas in combined cycle power plant, a new type dehydration equipment is introduced. The curved plate dehydration equipment is composed of many pieces of stainless plate which has some collection hooks at every corner. Meanwhile, a new method on measuring moisture in gas by using superfine fibreglass is introduced.The gas-water separation efficiency was calculated by the difference of moisture content before and after the curved plate dehydration equipment. The dehydration efficiency of curved plate in combined cycle power plant system was tested under different operating load, the results show that gas velocity and gas/liquid ratio have a great influence on the coal gas dehydration efficiency. If the washing water flow rate and pressure are changed, the efficiency will change at the same time. The moisture content is low when the spraying nozle works at a high water pressure. The operation water pressure and working voltage of electrostatic precipitator have been proposed by testing and analysis. It will have great advantage to the safe operation of turbine.

Abstract: The performance tests of an electronically controlled high pressure common rail diesel engine and of the car mounted with an engine of this type fuelled by biodiesel–diesel mixed fuel with different mixing ratios are conducted, and its power outputs, fuel economies and emissions are measured and compared with the one of diesel operation. The results indicate that: when the load is 2200 r/min, the effective specific energy consumption decreases, NOx emission increases; smoke emission decreases at high load and keeps almost no change at low and middle loads; HC emission decreases at low and middle loads and keeps the same at high loads, and CO emission maintains the same; at full load characteristics, the power output increases slightly, HC and smoke emissions decrease, CO and NOx emissions increase.

Abstract: Electromagnetic railgun can perform precision strike in long range. It is obtained that the scatter of velocity must be exist because there are many effectors influencing launching process, for example, the manufacturing error, the initial value of launching parameters and uncertainty during launching process and so on. Among these factors, the parameters of armature are easy to adjust to ensure the consistence of velocity. So we attempt to apply Grey Analyzing Model to carry on the study, and then by means of the measurement of strain on the barrel to verify the model. The result shows that the reasonable matching of armature mass and diameter can be helpful to improve the consistence of armature muzzle with the other parameters the same. This method is a new attempt to study the stability and consistence of velocity of solid armature.

Abstract: Cosolvent is used and a fuel blend of diesel oil and methanol is made to help solve the problem of intermiscibility of the two. Comparative experiment is made on the power performance and emission characteristics of a 4102QB DI diesel engine with diesel and different proportion of fuel blend of 10%, 20% and 30% methanol respectively. Test results indicate that, providing there is no change to the diesel engine parameter and basic structure, the increased percent of methanol will cause drops of power performance and significant reduction of smoke emission density and CO, but amount of emission density of HC and NO_x is slightly increased. However, the emission density does not change too much.

Abstract: This paper presents a vacuum system design for extreme ultraviolet lithography (EUV) and studies the prediction of pump-down curves for vacuum chambers. Related basic theories include gas laws, conductance for several kinds of flow regimes, equivalent length for pipes, outgassing, diffusion, and permeation etc. The simulation program consists of a MFC module and a MATLAB module. The MFC module is used to input necessary parameters, including start and target pressure for pumping, volume and inner surface area of vacuum chambers, configuration of pumping lines, performance of vacuum pumps, and gas loads. The MATLAB module deals with the pump-down curve calculation based on related theories. The governing equation of the conservation of mass in a pumped vacuum chamber is derived from extended Temkin isotherm. The pump-down curve of vacuum chamber is predicted by four steps, including calculation of equivalent length for pipes, conductance of pipes, and effective pumping speed of pumps, and pump-down time. An empty vacuum chamber is used to test the developed program. The pump-down curve reaches 6.5E-8 torr with 42 hours pump-down time in experiment measurement, and the simulated curve reaches 5.79E-8 torr at the same time point. The developed program can predict pump-down curve with a good accuracy in the range from low vacuum pressure to high vacuum pressure.

Abstract: The double-acting air-oil intensifier designed in this paper can continuously output high pressure oil which meets the requirements of equipment that is high-pressure and with recirculation motion and it is driven by pneumatic substituting the independent hydraulic power source driven by electric motor. It consists of twin roller piston air cylinder, force amplifier, hydraulic cylinder and oil supercharger. The piston of air cylinder propelled by pressure gas makes cyclic motion and the driving force of piston increased by force amplifier pushes the piston of hydraulic cylinder and forces out hydraulic oil, then oil is input to the system after the second time when pressure amplification by oil superchargers. It has many advantages such as higher pressure ratio, compact structure, high efficiency, low cost and easy access to regulate pressure and flow rate.

Abstract: Detailed experimental study on the characteristics of false defrosting of a split type air-source heat pump (ASHP) has been made. The results show that the false defrosting is seriously detrimental to ASHP by comparing varied parameters of compressor such as shaft power, suction and discharge pressure, etc. in normal defrosting and false defrosting. This paper also analyzes a common defrosting control method for air conditioner of split ASHP room, i.e., with two temperature sensors set on indoor heat exchanger, the operating principle thereof and drawbacks in terms of causing false defrosting.

Abstract: The meridional channel has an important effect on the flow properties of centrifugal compressor. High performance meridional channel can be obtained by determining Bezier curves, which can realize local optimization to the airfoil expediently. Three kinds of meridional channel model are established basing on Bezier theory. A method to calculate the meridional channel width is proposed using the expression of UG and the distribution law of inscribed circle and stream surface is given as well. By means of numerical simulation, the effects on the flow capacity of different variation of inscribed circle and stream surface are compared in the same inlet and outlet geometric parameters. The result indicates that reasonable design of meridional channel increases the efficiency, improves the blockage point flow significantly, and provides with a broader and stable operating range to compressor.

Abstract: A coordinated control strategy based on Direct Yaw Moment Control (DYC) and slip rate control was proposed aiming at improving vehicle stability. The system was divided into two layers: an upper layer and a lower layer. DYC was the upper-layer control, which calculates the additional yaw moment exerted on the vehicle based on the working condition of the vehicle. A simplified arithmetic of transferring additional yaw moment to desired slip rate was adopted in order to achieve differential braking. Slip rate controller was the lower-layer control that exerts braking force on the braking wheels to achieve the desired slip rate and to achieve desired yaw moment.