The paper concerns numerical study of fully developed laminar flow of a Newtonian water and non-Newtonian fluids, 0.2% aqueous of sodium carboxymethyl cellulose(CMC) solution in eccentric annuli with combined bulk axial flow and inner cylinder rotation. Pressure losses and skin friction coefficients have been measured when the inner cylinder rotates at the speed of 0～200 rpm. A numerical analysis considered mainly the effects of annular eccentricity and inner cylinder rotation. The present analysis has demonstrated the importance of the drill pipe rotation and eccentricity. In eccentricity of 0.7 of a Newtonian water, the flow field is recirculation dominated and unexpected behavior is observed. it generates a strong rotation directed layer, that two opposing effects act to create two local peaks of the axial velocity. The influences of rotation, radius ratio and working fluid on the annular flow field are investigated.
The flow rate analysis for sanitary fixtures has been studied to determine the water supply piping system and size. The study has been carried out to analyze for a various water supply pressure and piping size theoretically. Also, the study has been carried out to analyze for a various water supply piping system experimentally. The water supply pressure is varied from 0.01MPa to 0.07MPa, and the piping size is varied from 6mm to 15mm. The water supply piping systems are one-to-one, all-loop-type, and bathroom-loop-type water supply piping system. The results indicate that the piping size is able to supply water fully in case of smaller than 15mm if the water supply pressure keep an necessary minimum pressure. And the gap of flow rate is very little for the various water supply piping systems
The safety at this study is investigated by flow or stress analyses due to configuration or installation direction of fuel tank in the existing CNG bus. In case of the lower ceiling with sharp type, the equivalent stress due to the explosion of fuel tank is less than the type of flat or arc. it becomes safer on passenger. In case of the installation direction of fuel tank in the existing CNG bus, the stress applied on the lower ceiling at transverse direction becomes less than at longitudinal direction. It is more stable on the safety of passenger. The harm on the explosion accident can be prevented by use of the analysis result at this study.
본 연구는 산업용 열교환기 및 상용 파이프의 최적 설계를 위하여 열교환기 내의 사각형 단면 파이프의 shear-thickening 비뉴톤 유체의 압력강하 및 대류 열전달률을 수치해석적으로 수행하였다. shear-thickening 유체의 구성 방정식은 기존의 비뉴톤 유체 멱법칙을 보완한 확장 멱법칙 모델을 채택하였다. 파이프 내의 압력강하를 의미하는 마찰계수와 확장 레이놀즈 수의 곱은 기존 연구의 비교자료와 비교할 때 뉴톤 유체 영역과 멱법칙 영역에서 각각 0.018% 및 0.06% 내에서 일치함을 보였고, 대류 열전달률을 의미하는 뉴셀트 수는 문헌치와 비교할 때 뉴톤 유체 영역과 멱법칙 영역에서 각각 0.025% 및 0.14% 내에서 일치함을 보였다. 비뉴톤 확장 멱법칙 유체 모델의 형태를 띠는 shear-thickening 유체를 열교환기 또는 상용파이프 내의 사각형 단면 파이프 내에서 사용하면 유동지수(n)에 따라서 뉴톤 유체보다 최대 160%의 압력강하를 증가시켰고 최대 14%의 대류 열전달 감소를 발생시킬 수 있었다.
Smart Door(SD) is a human friendly power-assisted door system for passenger car doors. It offers comfort and safety to passengers and drivers by supplying additional power. In this study, dynamic system model and the equation of motion derivation are derived. And we propose the disturbance observer based collision detection algorithm for safety when opening the door. A disturbance caused by collision has a fast response compared to a friction, uncertainties and so on. The main idea this study is to estimate a variation of disturbance for stably and effectively detecting a collision. In order to evaluate a performance of collision detection, an experiment set up is constructed. The experimental results validate the usefulness of the proposed collision detection algorithm.
The purpose of this study is to investigate the actual field application of the super-charger for heavy equipment. In this paper, the numerical analysis and performance evaluating experiments were performed. ANSYS CFX program has been used to obtain the solutions for the problems of three-dimensional turbulent air flow in the super-charger. To evaluate the flow performance of the super-charger, the performance test facility and data acquisition system were manufactured. We obtained satisfactory results from CFD analysis and flow experiment.
The air blowers for fuel cell electric vehicle usually have big difference between inlet and outlet pressure. When the casing of the air blowers is designed, the stress analysis is required. (Approximately Inlet pressure is 0.5bar and outlet pressure is 2bar.) Gap distance between the casing and the impeller is 0.3mm. Therefore, if the amount of maximum deformation of casing is larger than 0.3mm, impeller crashed the casing. In order to avoid crashing, both the thickness and number of rims are changed and carried out simulations on each cases.
Recently, various efforts to make more speedy and precision machine tool to improve productivity and also various efforts to solve environmental problem are going on, so that dry cutting in manufacturing industry, which needs environmental conscious design and development of manufacturing technique, is becoming a very important assignment to solve. Because dry cutting does not use cutting fluid, we need other methods that can be used instead of cutting fluid, which does cooling, lubricating, chip washing, and anti-corrosion. Especially, because turning is a continuous work, the consideration of tool life and surface roughness due to continuous heat and poor lubrication is important. The purposes of this paper are the consideration of how well the compressed air can work instead of cutting fluid, and also the development of the method to select the optimum machining condition by the minimum numbers of experiments through the Taguchi method.
In this study, a experimental work to investigate the influence of a turbulent wake flow on the velocity distribution of a diffuser with PIV method. The turbulent wake is generated by a rectangular prism, which is installed at the inlet of a diffuser. The results show that the velocity recovery of the subsonic diffuser is dependent on the height and location of rectangular prism. It is found that a certain height of the rectangular prism to generate the turbulent wake give a better velocity recovery, compared with no rectangular prism.
Hull forms for catamaran type small fishing boat powered by electric motor are newly developed by experimental approaches. Model tests for two hull forms having different length are made at circulating water channel. Resistance performance and wave patterns are compared to carry out an analysis of the effect of extension of main body. The results show that the extension of main body can give better resistance performance above a certain velocity.
Earth to air heat exchangers made by iron, aluminium, copper and poly-ethylene pipe for single greenhouse heating were experimented and blowers. Earth to air heat exchanger was installed by pipelines in earth tube at 70cm depths and air blower was the heating capacity 3kW/h, As the result, Temperature difference due to temperature history of the inlet and outlet air on the various type in earth tube in greenhouse showed that air temperature at the various type in earth tube, comparison tube were make no difference respectively. Under the experimental condition, heat fluxes and heating load were showed 6,800Kcal/h, 19,699kcal/h generally yield of Lactuca Sativa cultured during days of sowing 90day in greenhouse using copper pipe was 170% incleased.
Tire manufactures have dealt with noise problem by varying the pitch of the tread. The various formulas for the variations are generally determined differently, however. Often these variations are based on a combination of trial and error, intuition, and economics. Some manufactures have models and analogs to test tread patterns and their variations. These efforts, however practical, do not determine the best variation beforehand or guarantee the best results. For this reason it was felt that a general mathematical approach for determining the best variation was needed. Moreover, the method should be completely general, easy to use, and sufficiently accurate. This paper discusses a mathematical method called Mechanical Frequency Modulation(MFM) which meets the above requirements. Thus, MFM pertains to computing an irregular time sequence of events so that the resulting excitation spectrum is shaped to a preferred form. The first part of this paper treats the theoretical basis for computing an optimum variation ; the second part discusses experimental results and simulation program which corroborate the theory.
Experimental analysis has been carried out to investigate thermal characteristics of hydraulic system in special vehicles. Hydraulic system performance is largely influenced by oil temperature, and there are considerable performance decline and malfunctions in the system for high temperature conditions caused by heavy load and continuous operation. Transient oil temperature and pressure variation are analyzed and heat generation rates in the several main system parts are compared for various flow rates. With the start of system operation oil temperature gradually increases, and viscosity deceases by about 70% as temperature increases from 20℃ to 80℃. Operation pressure in the hydraulic system decreases with oil temperature, and its variation rate becomes less steep as oil temperature increases. Heat generation rate in hydraulic pump also depends on the oil temperature, and it reaches maximum near 50℃. These results in this study can be applied to optimal design of efficient hydraulic system in special vehicles.
This paper presents a new type of optical silicon accelerometer using deep reactive ion etching (DRIE) and micro-stereolithography technology. Optical silicon accelerometer is based on a mass suspended by four vertical beams. A vertical shutter at the end of the mass can only moves along the sensing axis in the optical path between two single-mode optical fibers. The shutter modulates intensity of light from a laser diode reaching a photo detector. With the DRIE technique for (100) silicon, it is possible to etch a vertical shutter and beam. This ensures low sensitivity to accelerations that are not along the sensing axis. The microstructure for sensor packaging and optical fiber fixing was fabricated using micro stereolithography technology. Designed sensors are two types and each resonant frequency is about 15 kHz and 5 kHz.
On cold start operation of an SI engine, a catalyst shows poor performance before it reaches activation temperature. Therefore, fast warmup of the catalyst is very crucial to reduce harmful emissions. In this study, an appropriate control strategy is investigated to increase exhaust gas temperature through changes of spark timing. Combustion stability is also considered at the same time. Exhaust gas temperature and pressure of combustion chamber are measured to investigate the effects of spark timings on cold start and idle performance. Experiments showed that retarded spark timing promotes the combustion at the end of expansion stroke and increases exhaust gas temperature during cold start.
The ice tank is important facility to check the performance of the ship and offshore in ice condition before the construction. MOERI(Maritime & Ocean Engineering Research Institute) constructed ice model basin on the end of 2010. The ice technology to know the phenomena of ice near the ship and to estimate power of the ship in model scale is the main characteristic of the ice model basin. To achieve this goal in one ice sheet, making of test plan and feasibility check of test possibility have to review in the beginning stage of the every test. This paper describes the number of maximum resistance and self propulsion test in a sheet of level ice and proposes the methodology to optimize pack ice, rubble ice, brash ice and ice ridge test in MOERI ice tank. The feasibility of free running test to know maneuvering performance in ice field and some specific idea to measuring ice thickness and ice ridge shape was proposed.
A gear pump is a type of pump that displaces a volume of fluid by physical or mechanical action, or positive displacement pump. Power is applied to one of the gears and transmitted to a second driven gear via meshing teeth. This paper describes the hydraulic gear pump for an elevator. In gear pump, since geometrically special forms of gear tooth, ‘ulsations’is always caused in the delivery pressure and quantity. In other words, it is found that the number of delivery pressure pulsation per each revolution is always equal to that of the gear-teeth of the gear, which is coincident with the pulsation of the ideal delivery quantity. Some experimental results are given to verify the effectiveness of the developed pump.
Technological mode progress demands the use of materials at high temperature and pressure. Constant load creep tests have been carried out over the range of stresses at high temperatures. One of the most critical factors in considering such applications as the most critical one is the creep behavior. In order to investigate the creep behavior in this study, the stress exponents during creep were determined over the temperature range of 275℃ to 325℃ and the stress range of 36MPa to 72MPa. The applicability of modified Monkman-Grant relationship was also discussed.
In commercial vehicle, sub-frame which equipped in main frame supporting dump deck and oil tanker. This is the main structure for all equipment which including joint function. Sub-frame is made by welding process, this susceptible to deform and crack by its longitudinal size. Also various kind of sub-frame make it difficult to standardization in manufacturing process and exclusive jig is not adapted yet. Frame size is over 6~8m and weight is more than 300kg this make re-work more difficult. If manufacturing company made precise sub-frame, this is not only convenient for customers but also save the company money by reducing the working time. In this study manufacture the sub-frame be suitable for its main function and develop exclusive welding jig for obtain checking fixture function as well.
Driving mechanism, the central part of a robot, was designed in this study. Power for the motive drive was acquired by directly connecting the motor shaft in worm shape of the low-end DC motor, car window motor, to a decelerator. The decelerator consists of a worm gear to receive power from the motor shaft, a pinion gear to be connected in line with the worm gear, and an output shaft to be engaged to the pinion gear. Motion driving is achieved by the power from the motor shaft with the designed gears, transferred to the deceleration mechanism and to the output gear