Papers by Keyword: Back Pressure

Abstract: This paper deals with characteristics of hot forging of twin roll cast magnesium alloyswhich have relatively high aluminum content. High tensile strength magnesium alloys containing 9 to12% aluminum, such as Mg-9%Al-1%Zn, Mg-10%Al-1%Zn, Mg-11%Al-1%Zn, andMg-12%Al-1%Zn have been made by twin roll casting. A new experiment was performed for hotforging of high strength magnesium alloys with high aluminum content was performed. From theresults, using magnesium alloys with high aluminum content yielded less compressive deformationresistance than AXM403. It was also demonstrated that hot forging of magnesium alloys with highaluminum content produces small magnesium crystals (about six micro meters) and crystallizedsubstances. The mean grain size of the microstructure of Mg-12%Al-1%Zn forged at 623K was lessten micrometers although that of the Mg-9%Al-1%Zn was about thirty micrometers. The small betaphase which precipitates in the twin roll cast Mg-12%Al-1%Zn was distributed uniformly comparingto Mg-9%Al-1%Zn. From the result of microscopic observation of the forged products, it has beenrecognised that the Hall-petch rule between mean grain size of forged materials and Vickers hardnesshas been proved. The effects of the dynamic recrystallization on the microstructures of the twin-rollcast products seem to be different in terms of aluminum content. Due to rapid cooling of twin-rollcasting process process, the fabricated magnesium material could be used for hot forging. By applyinga servo press machine, a hot-forging experiment was performed with development of high strengthmagnesium alloys. A novel material that show higher hardness have been fabricated by usingtwin-roll casting process. It has also been clarified that the aluminum content affect precipitation ofbeta phase as well as grain size.

Abstract: In order to minimize the sound transmission due to exhaust gases, the most common and important part of the engine system is muffler. A back pressure on engine is always produce due to the use of the exhaust muffler. This back pressure represents the extra static pressure exerted by the muffler on the engine through the restriction in flow of exhaust gases. The back pressure mainly depends on the internal shape and overall design of the exhaust muffler. Design of muffler is a complex function that affects noise characteristics, emission and fuel efficiency of engine. In this study, a combine model of response surface methodology (RSM) and desirability analysis is used for optimizing the back pressure of a motorcycle reactive muffler, in order to improve the performance of the muffler. For this optimization process, the design variable parameters are size of perforation, number of perforation and chamber size. To measure the back pressure 3D CFD based CAE software has been used. Prediction of acoustics transmission loss virtually is an important analysis required for the development of muffler at an initial design stage. For this reason, for the optimized design virtual acoustics transmission loss analysis is conducted. It is found that after optimizing the design of the muffler, the back pressure is decreased and the acoustics transmission loss is increased that can ensure the improvement of the muffler efficiency.

Abstract: In this present study Al-5083 alloy powders were prepared from elemental powders using high energy ball milling under optimized milling parameters. Various properties such as crystalline size, particle size and morphology have been studied using X-Ray diffraction analysis and Scanning Electron Microscopy. It was found that Al-5083 alloy was formed and nanocrystalline size particles were achieved. These nanocrystalline Al-5083 alloy powders were consolidated using equal channel angular pressing with and without application of back pressure. Physical and mechanical properties such as density and hardness are studied.

Abstract: This paper discusses the design and development of a low cost small engine dynamometer for engine testing to measure engine performance i.e. power, torque and specific fuel consumption. The data and result were achieved by using a small hydraulic engine dynamometer with specific considerations and standard followed in order to have good engine dynamometer. Small engine was used by coupling it with the hydraulic pump that come with the control valve and pressure gauge. Control valve was set to build back pressure inside the pumping area. When the engine starts, the pressure gauge will give a reading which can be used to calculate the engine torque. By using the engine torque, engine power can be obtained by multiplying the angular speed with engine torque. Specific fuel consumption can be defined, by dividing the brake engine power with the fuel rate. From the experiment data, the brake power of the single cylinder engine showed that it is almost similar to the specification given by the manufacturer. The low cost hydraulic engine dynamometer, which is less than RM 15,000 can be used to measure an engine performance. The engine power, torque, engine speed and air fuel ratio data can be achieved from our developed engine dynamometer.

Abstract: In this present work the elemental powders pertaining to composition of Al5083 alloy was milled using planetary ball mill (Insmart systems) for 20 h. The elemental powders are loaded in HSS vial with 10:1 ball to powder ratio at 250 RPM. Various parameters such as crystalline size, particle size and morphology have studied using X-ray diffraction analysis and scanning electron microscopy. The crystallite size of the powders determined using Williamson Hall analysis of XRD is 23 nm after 20 h of milling. These nanocrystalline Al-5083 alloy powders were consolidated using ECAP with and without application of back pressure. Physical and mechanical properties such as density and hardness values were measured for sintered and unsintered samples.

Abstract: A study was carried out on the influence of different back pressures on internal flow of diesel injector nozzles. For this study, a flow visualization experimental system equipped with a pressurized chamber was setup. Experimental results show that, with the injection pressure remain constant and increase back pressure leading to the cavitation area diminished gradually and even disappeared. With a same pressure difference, higher back pressure test condition promoted the outlet mean velocity and inhibited the occurrence of cavitation inception, which demanded a larger pressure difference to make it happen. Moreover, it also resulted in a relatively large flow losses to the single phase flow compared to the cavitating flow.

Abstract: Because of the gas slippage, the testing methods of stress sensitivity for gas reservoir should be different from that for oil reservoir. This text adopts the method that imposing back pressure on the outlet of testing core to weaken the gas slippage effect and tests the stress sensitivity of low permeability gas reservoirs, then analyzes the influence of permeability and water saturation on stress sensitivity. The results show that: low permeable and water-bearing gas reservoirs have strong stress sensitivity; the testing permeability has the power function relationship with net stress, compared to the exponential function, the fitting correlation coefficient is larger and more suited to the actual; the lower the permeability is and the higher water saturation is, the stronger the stress sensitivity is. The production of gas well is affected when considering the stress sensitivity, so the pressure dropping rate should be reasonable when low permeable gas reservoirs are developed. The results provide theoretical references for analyzing the well production and numerical simulation.

Abstract: The numerical simulation of equal channel angular extrusion (ECAE) with variable back pressure was researched by applying the commercial Deform-3D software, in which choosing the hard deformation materials of 7075 aluminum alloy, and comparing the traditional ECAE without back pressure process. The influence of back pressure on the mean stress and the effective strain rate in the shear deformation zone was studied. The results show that the extrusion force transformation laws were different in both load ways, with the increase of back pressure, extrusion force enhances increasingly, but the final load-time curves tended towards stability, but in ECAE without back pressure, the final load-time curves tended towards decreasing; thus the whole deformation process can be divided into different stages. In addition, the larger the absolute value of the hydrostatic stress at the corner, the more beneficial to refine grain and improve the plasticity. The back pressure makes the distribution of effective strain rate in plastic deformation area more uniform and improves the uniformity of deformation.

Abstract: Urea-SCR catalytic converter can effectively reduce the NOx emission of diesel engines, but meanwhile catalytic converter will cause some pressure loss in the exhaust system, which has negative influences on the engine performances. In this paper, the method of theoretical analysis calculated the pressure loss of the SCR catalytic converter, and designing a new type of exhaust gas pipe. Through the test to meet the design requirements,the results can provide a reference for optimum design of SCR catalytic converters and assembling.

Abstract: Jet pump has different basic characteristics when it is used in different working condition. According to the model of jet pump unloading system used in the oilfield, the lab experiment use high pressure pump to provide high power liquid and suction liquid, and also making use of throttle valve providing back pressure condition, to simulate the condition of oil well unloading system much better. The experiment tests pressure and flow of power liquid, suction liquid and mixture liquid , and achieve the basic characteristic curve of jet pump. The result show that according to the different application conditions, can change the jet pump efficient working area range when needed, by adjusting the distance between nozzle and throat, and the optimal distance is the diameter of nozzle 2~3 times.