Applied Mechanics and Materials Vol. 709

Abstract: Based on the research of air-duct system in ARJ21-700, insulation design is studied in this paper. Considering its specific characteristics, CFD method based on FLUENT is taken to its thermodynamic calculation. The result shows that diversion tunnels along the pipeline have remarkable effects on the skin temperature distribution of the heat-insulating layer, while differ with diversion tunnels’ amounts. These effects should be adopted into the engineering algorithm and these works would be helpful to the design and optimization of the air-duct system.

Abstract: This paper proposes a vertical assembled sprayer for supplying water and liquid fertilizer. This proposed sprayer consists of both iron structure and hardware modules, including a microcon-troller, LCD, keypad, batteries, nozzles, and diaphragm pumps. The height of this proposed sprayer ranges from 1.5 to 4.5 meters so as to be adjusted by a user. The water quantity and the nozzle numbers can be specified by a user’s demand. Moreover, either manual or automatic operations can also be selected by a user. The experimental results have been shown that the average spraying times for using 1 - 4 nozzles are equal to 95.2 sec, 48.41 sec, 32.3 sec, and 24.5 sec, respectively. Moreover, the average spraying times from the experiments are close to the calculated spraying time of microcontroller where the errors are less than 2%.

Abstract: Rotating detonation engines are studied more and more widely because of high thermodynamic efficiency and high specific impulse. Rotating detonation of hydrogen and oxygen was achieved in this study. Rotating detonation waves were observed by high speed cameras and detonation pressure traces were recorded by PCB pressure sensors. The velocity of rotating detonation waves is fluctuating during the run. Low frequency detonation instabilities, intermediate frequency detonation instabilities and high frequency detonation instabilities were discovered. They are relevant to unsteady heat release, acoustic oscillations and rotating detonation waves.

Abstract: The joint interface plays a significant role in machine tools and other machineries. A novel type of joint which consists of oily porous material was proposed in the paper. A test system for identifying the unit area dynamic characteristic parameters of Fe-based joint interfaces were represented. The stiffness and damping parameters were compare to the conversional structures. The result showed that the joint which contains an oil film interlayer formed by porous and steel was superior to the joint with non-media formed by steel in stiffness and damping characteristics. In the case of the same preload, the former’s stiffness is increased by about 50 %, and the damping is increased about five to six times.

Abstract: This paper studies a buffer overflow valve that is attached to a hydraulic rotary motor which could reduce high hydraulic impact when the hydraulic rotary motor starts, brakes or suddenly reverses. A rotary motor buffer overflow valve was modeled and simulated using a computer software, AMESim, and the relation of the buffer overflow valve to the hydraulic impact experienced by the motor was analyzed. The cushioning property of the buffer overflow valve of a rotary motor is verified by using an excavator. It is concluded that having a reasonable design of the buffer overflow valve’s maximum displacement for the buffer set and diameter size for the buffer damping hole, it can reduce the pressure impact experienced by the hydraulic rotary motor and improve its operating performance, which also improves the service life of the system or its hydraulic components.

Abstract: The methane combustion air coefficient is expected to reach nearly or over 1.2 drawn from previous studies, through rationally allocating the position of the Venturi tube when rotation angle in the 16-18° and tilt angle between 7-7.5°. This paper carries on the numerical simulation of combustion in porous media based on previous work by selecting the optimum conditions, in order to provide certain references for the improvement of porous burner.

Abstract: This paper has studied the influence of the different ratio on combustion process and emissions of air premixed methanol/diesel dual fuel engine. The research was based on 4B26 diesel engine, and the 3-D numerical simulation on combustion process and emissions of the diesel engine with intake premixed methanol was carried out using AVL FIRE software. The study showed that,with the compression ratio reducing,the ignition delay period prolonged, and the ignition timing delayed, the maximum firing pressure, the peak of pressure rise rate and the maximum combustion temperature in cylinder decreased, the crank angle postponed, the NOX emission decreased and the Soot emission increased obviously.

Abstract: In this paper, the experimental research of porous media combustion was carried on premixed combustion of multiple ejection/tangential burner, the ignition characteristic, the resistance characteristics and the temperature distribution in the burner were obtained, and the experimental results were analyzed in detailed, which can provide references for the improvements of novel porous medium burner.

Abstract: Metal extrusion is currently very beneficial for producing workpieces with long dimensions or when a uniform cross section area is required. Design of extrusion dies, which results to the shape, geometry and size of the workpiece, is the main factor for quality, productivity and durability of the products. Besides improving the bearing length, a die pocket is a good solution to effectively control the velocity of material flow into the die hole. Therefore, this study aimed to evaluate the structures of die pockets that influence the material flow in the extrusion process. Thus, the finite element method (FEM) was used to determine the parameters that affect the strength of the extrusion die due to the maximum stresses which occurred on the die and pocket. From this study, it was found that the circular shaped pocket with 31degrees pocket angle, 22 mm pocket die thickness and made of titanium alloy provided the maximum strengths and safety factors. This result from the simulations can sufficiently predict the risk of damages on the extrusion die and pocket for further extension of the tool’s life cycle.

Abstract: This article reviews the experience of determining stiffness and strength characteristics of structural joints for their further use in FEM models of long span structures for stages of nonlinear dynamic deformation and failure.