Recently, the use of tubes in the manufacturing of the automobile parts has increased and therefore many automotive manufactures have tried to use hydro-forming technology. The hydro-forming technology may cause many advantages to automotive applications in terms of better structural integrity of the parts, lower cost from fewer part count, material saving, weight reduction, lower spring-back, improved strength and durability and design flexibility. In this study, the whole process of sub-frame parts development by tube hydro-forming using steel material is presented. At the part design stage, it requires feasibility study and process design aided by CAE (computer aided design) to confirm hydro-formability in details. Overall possibility of hydro-formable sub-frame parts could be examined by cross sectional analyses. All the components of prototyping tools are designed and interference with press is examined from the point of geometry and thinning.
The effects of intake system on turbulent kinetic energy for the in-cylinder flow of a four-valve SI engine were studied. For this study, the same head, cylinder, and the piston were used to examine turbulence characteristics in two different intake systems. In-cylinder flow measurements were conducted using three dimensional LDV system. The measurement method, which simultaneously collects 3-D velocity data, allowed a evaluation of turbulent kinetic energy inside a cylinder. High levels of turbulent kinetic energy were found in regions of high shear flow, attributed to the collisions of intake flows. These specific results support the more general conclusion that the slightly offset direction of the intake system produced higher in-cylinder velocities on the +x-axis side of the cylinder which caused some asymmetric flow patterns about the z-axis. Higher levels of turbulent kinetic energy prevailed in zones of mean velocity collisions and regions where significant directional changes in the mean velocity patterns occurred.
The autoignition characteristics of n-heptane/n-butanol were investigated both experimentally and numerically. The effects of oxygen concentration and exhaust gas recirculation rate on the autoignition characteristics were evaluated. A rapid compression machine was employed to measure ignition delay times of blended fuels. A numerical study on the ignition delay time was performed using the CHEMKIN-PRO software to calculate ignition delay time and predict the chemical species in the combustion process. The results revealed that the ignition delay time increased with decreasing oxygen concentration due to the thermal load effect of nitrogen. The oxidation reaction of n-heptane in a low temperature regime was limited with decreasing oxygen concentration. The ignition delay time sharply decreased with exhaust gas recirculation because of the intermediate species in the exhaust gas. Exhaust gas recirculation reduced first ignition delay dramatically. However, the time interval between the first and main ignition increased with increased exhaust gas recirculation.
Recently, uncertainty of demand and supply for energy has expanded as energy market change rapidly. Rapid accumulation storing of cold heat is a method for decreasing the gap between demand and supply of time, quantity and quality of heat energy. It is stored rapidly when electric power is on. And cold heat energy in heat is phase change material (PCM) heat storage is used when electric power is off. Porous media for cold heat is PCM. The present study has been conducted for improving performance of cold heat storage in refrigerator using characteristics on laten heat and phase change of PCM. This study provide basic data to improve performance of cold heat using characteristic of PCM. Also, this study predicts and measures specific points in PCM heat storage during process of phase change.
This study is to conduct the optimal design of the fluid mixing blades in the test fluid tank for sewage treatment process. The design was made with various shapes and angles of mixing blades. Fluid mixing blades in the tank are numerically analyzed with FLUENT V.13.0. Blade1 and Blade4 had the biggest fluid pressure difference of 8.1% around the blades. And, Blade1 and Blade3 had the least fluid pressure difference of 2.55%. The biggest turbulence kinetic energy of 12.5% existed around Blade1 and Blade4. Blade1 and Blade3 had the least turbulent kinetic energy difference of 4.8%. Blade4 is the optimal design shape due to the highest turbulent kinetic energy around the blades in comparison to the other cases.
Formulations for simulating trajectories of the pantograph and reaction forces at nodal points of the pantograph mechanism are presented to develop the mechanism analysis program for railway pantograph with one contact strip. By comparison between the developed program and Solid Works®, commercial CAD S/W for tilting angles of the contact strip simulated during its upward motions, the accuracy of the formulations is validated. An optimal pantograph mechanism can be obtained by using the developed program which can simulate the changes of major design parameters, such as tilting angles of a contact strip and driving moments of a lower arm, as the lengths of members are changed.
This paper investigates the relationship between the waveform area and fuel injection quantity. It is on developing on analysis method of waveform the effect of waveform area on fuel injection quantity of CRDI Diesel engine. The experimental methods using Pico oscilloscope and fuel injection tester are employed to measure current and voltage waveform and fuel injection quantity of solenoid injector. The one normal and two abnormal solenoid injectors are used. The experiment is carried out during no-load condition. A summary of the important results are as follows. 1) The area of the voltage and current waveform of the abnormal injector becomes larger than the that of normal injector, and the area of the current and voltage waveform is inversely proportional to the fuel injection quantity. 2) The area of the current waveform can be obtained more accurate results than that of voltage waveform. 3) It is possible to infer the fuel injection quantity by measuring the current waveform and calculating the area.
This research is to numerically perform the optimal design of the shutter valves in the two-stroke engine by analyzing flow resistance with four different design shapes. Shutter valves were numerically analysed for four different industry-design based cases using ANSYS FLUENT V.14. At the result, it was found that the most design-effective case was case 4 with dimensions of 4.5 cm radius and 26 cm length of cylinder with a sphere of 6 cm radius in the valve. Pressure loss of three cases is between 0.70% and 6.48% when compared to case 1. However, 0.16% of pressure loss increased as the rotational speed of valve increased with 1 rad/s. Thus, at lower rotational speed, the case 4 was possibly optimal shape design due to the lowest pressure loss.
In this study, the performance of a small - sized wave heat exchanger to be applied to the white smoke reduction system was experimentally confirmed. The heat transfer rate, drain and pressure drop were measured according to the air flow rate, water flow rate and relative humidity change of the wave heat exchanger for two kinds of pitch numbers. A constant temperature and humidity calorimeter and a constant temperature water bath were used to measure the performance of the wave heat exchanger. The heat transfer rate and drain increased gradually with changes of water flow rate. Case 2 showed more than 50% higher heat transfer rate and drain than Case 1. The increase of air heat transfer rate and drain according to air flow rate was greatly increased when the number of pitches was the same or increased, unlike the result of water flow rate change. In the temperature visualization using a thermal imaging camera, it can be seen that as the water flow rate and the number of pitches increase, the heat transfer becomes more effective in Case 2.
SUS hexagonal bar, which is manufactured by drawing process of SUS circular bar, have been widely used to make various adapters and fittings. The purpose of this study is to investigate the characteristics and stability of variable roll unit including stand module. Stand module is essential part of variable roll unit. Structural analysis was performed to predict the stability of stand module using 3 loads (50, 75, 100 Ton), thus it may be of help to the manufacture of stand module. As the results, internal ring of bearing showed maximum equivalent stress, and moreover bearing, shaft and roller had to be preferentially considered in order to maintain its stability. In cases of 50 and 75 Ton, there were no problems for stabilities, respectively, on the other hand, problem for stability may occur in case of 100 Ton.
In this study, the ion beam irradiation method on organic (polyamic acid and epoxy resin compound) overcoat layer was investigated. The use of ion beam on overcoat organic layer has the potential to replace conventional rubbing process. The traditional alignment layer is made by coating process and 2 times heat treatment on polyamic acid liquid. It requires many times and process steps. However, it is very economic and convenient process substitute polyimide alignment layer for organic overcoat. In order to characterize the LC alignment the polarized microscope image and pretilt angle measurement were investigated. The good LC aligning capabilities treated on the organic overcoat thin film surfaces with ion beam exposure of 45° at above ion beam energy density of 1200 eV were achieved.
The Air-shiter is a new product possible ventilation at the same time cooling or heating with combined refrigerator and heat recovery ventilator. And a key device of this system is the air shifter. The air shifter device is to convert the outdoor air, room air, supply air and exhaust air flow. Therefore, an experimental study has been carried out to investigate the operating performance for this system. The results, it is possible to ventilate at the same time of heating by outside air above 30℃ in summer. and of heating by outside air within 3℃ in winter. The indoor discharge temperature is over 40℃, and the coefficient of performance is 3.4 in winter.
An experimental investigation is performed to study the effect of jet to plate spacing and low Reynolds number on the local heat transfer distribution to normally impinging submerged circular air jet on a smooth and flat surface. A single jet from a straight circular nozzle of length to diameter ratio(l/d) of 83 is tested. Reynolds number based on nozzle exit condition is varied between 500 and 8,000 and jet to plate spacing between 0.5 and 8 nozzle diameter. The local het transfer characteristics are obtained using thermal images from infrared thermal imaging technique. It was observed that at lower Reynolds numbers, the effect of jet to plate distances covered during the study on the stagnation point Nusselt numbers is minimal. At all jet to plate distances, the stagnation point Nusselt numbers decrease monotonically with the maximum occurring at a z/d of 0.5 as opposed to the stagnation point Nusselt numbers at high Reynolds numbers which occur around a z/d of 6.
Today, conventional CVT equipped vehicle controls engine torque and gear ratio by using engine torque map and shifting map. But this control process is difficult to optimize the fuel economy when the driving mode is changed arbitrary. In this study, I propose the real-time CVT control with considering the power loss of transmission system to improve vehicle fuel economy and drivability. The driving performance and fuel economy of the proposed control logic is analyzed by backward simulation and the validity of new control logic is verified.
An Automatic feed mechanism is one of the most important systems that make up the air defence gun. The System which consists of consecutive mechanisms from a magazine to the breech of automatic machine gun(Dual) carries ammunitions through the feeding pass with a high speed by the electric boosters to synchronize with gun firing speed. In order to feed the rounds smoothly without jamming, it is necessary to optimize the design of the driving torque needed to carry them and to get a proper distribution of power between rounds after performing mathematical calculation. In this study, in order to predict and prevent malfunctions of feeding and unloading ammunition, we have developed an optimal computational model using CATIA and multi-body dynamics software, ADAMS.
These days, the interests on the high speed handling robots are increasing because it is important to get down the unit cost of production to get the price competitiveness. The SCARA robot with simple mechanism is more suitable to implement the high speed robot system as well known. The moving parts of SCARA robot have to be designed for high speed. But the structural analysis is induced by the robot links because they drive in high acceleration and deceleration. In this reason, the structural analysis of the high speed SCARA robot is very important in the design process. In this paper, the study on the structural analysis of a high speed SCARA robot has been done and the research results will be introduced.
According to the nuclear safety act, the enforcement regulations and the notification of the atomic energy commission, a preliminary decommissioning plan must be submitted at all domestic nuclear facilities. In accordance with this preliminary decommissioning plan, it is required to prepare eleven items from the outline of the decommissioning plan of the nuclear facility to the fire protection. Currently, the nuclear fuel cycle facility operated by the Korea Atomic Energy Research Institute (KAERI) consists of a radioactive waste form test facility (RWFTF), a post irradiation examination facility (PIEF), a radioactive waste treatment facility (RWTF), and a radioactive waste storage facility (RWSF). The decommissioning strategies, decommissioning methods and dismantling activities of these nuclear facilities are described in this paper. The scope of decommissioning, the dismantling method, the final conditions of the site, the management of radioactive waste, and the cost of decommissioning are established in the decommissioning strategy. The decommissioning schedule, work order, basic principle and technical feasibility are determined at the method of decommissioning. The disinfection techniques and activity plans for facilities and sites contaminated with radioactive materials are described at the dismantling activity. Therefore, this paper describes the concept of decommissioning of the nuclear fuel cycle facilities and prepares a preliminary decommissioning plan to be prepared afterwards.
With the concerns of global climate change, the significant changes in rainfall patterns have aggravated the occurrence of pollutants from agricultural uplands. Heavy and intensive rainfalls have rinsed a variety of pollutants off the land, sending them into the neighboring water environments which further causes water pollution problems. Recently, the application of PAM(Polyacrylamide) in agricultural lands has gotten much attention for soil conditioning. Therefore, this study aimed to develop the automatic control system applying the chemical flocculant, liquid PAM in order to flocculate the suspended solids and deposit at the bottom of farmland water channel, so eventually minimize the amount of non-point pollutants discharged into receiving water. The optimum feed rate for liquid PAM was calculated through the experiment in artificial water channel and applied to the control system. As the results of the performance test of the automatic turbid water control system installed in the sloped field, the range of turbidity reduction rate was 25 to 33% with the average turbidity of 292 to 498 NTU in water channel.
In commercial vehicles. the pulsation noise when the power steering operating is the major item to make the complain for users. If this noise have related to vibration characteristics in steering system's parts or assembly, it makes the problem in vehicle quality. Recently, the users demand the high quality in commercial vehicles, and we must identified the relevance between the pulsation noise and the vibration characteristics. After the identification, we can design the power steering system for satisfaction the user’s needs. Finally, the identification of relevance in pulsation noise for analysing the vibration characteristics will be suggested advanced power steering system.
In this paper, the relationship between the frequency split and the mode-coupling in the disc doublet mode, which is expressed according to the pattern of the surface of the disc, is utilized by using of 3 types(Chaos, Vent-hole, Normal). As the frequency split between the doublet mode disc that is expressed in the model through the interpretation is larger, and analogy through interpretation mode-coupling instability also lower. Vent-hole, which has a relatively large frequency split of disc doublet mode in 3 types(Chaos, Vent-hole, Normal) model, showed a large value of critical coefficient of friction in which mode-coupling instability is expressed. In addition, it was confirmed by analysis that the Vent-hole had a relatively large frequency split than the other models by analyzing the change in contact stiffness. It can be concluded that the larger the frequency split of the disc doublet mode, the lower the instability due to the mode-coupling.