The wavy fins have been widely used in the heat exchangers in coolering system, aerospace system and automotive. Especially, an automobile has the wavy fin and flat tube heat exchanger for oil cooling system. The objective of this research is the performance comparison of wavy fins for battle vehicle diesel engine oil-cooler by numerical analysis. The real type fin is the wavy fin with corrugated structure, and the comparative fin surfaces are plain, louver, lateral perforation and parallel wavy fin. The non-dimensional values of f-factor, j-factor, area goodness factor and volume goodness factor was performed on the performance comparison. The plain and louver fin shows the highest performance in pressure drop and heat transfer respectively. In the area goodness factor and volume goodness factor results, the parallel wavy fin and louver fin show the highest values at each result.
In this study, a high speed Rigid Inflatable Boat(RIB) with about 10 meters length is developed. Design speed of the boat is 30 knots (15.43 m/s) using 250 hp twin engines and main material is aluminum. Resistance performance related to the free running attitude as trim and sinkage are discussed and wave patterns are observed to make clear the relationship between the performance and wave characteristics using model test and CFD analysis. The results show that not only wave patterns but also free running attitude of the boat have a strong influence on resistance performance. CFD results including free surface give good relative tendency for effective power and the attitude comparing model test results. CFD analysis used in this study can be used at initial ship design stage of high speed boat.
In the power steering systems used for automobiles, because of its small size and low noise, a balanced type hydraulic vane pump is mainly used as a power source. Therefore it is requested to research on the lubrication characteristics of a oil hydraulic vane pump which is the key part to improve its performance. The performance of a oil hydraulic vane pump is influenced by the lubrication characteristics of the critical sliding components. Thus, lubrication characteristics between the shaft and the journal bearing have to be researched for the design and the performance improvement of a oil hydraulic vane pump. Therefore, in this paper, it is theoretically investigated that the lubrication characteristics between the shaft and the journal bearing of a balanced type oil hydraulic vane pump for power steering systems. The results demonstrate that lubrication characteristics are significantly influenced by the clearance between the shaft and the journal bearing.
In this study, we studied the alignment characteristics of liquid crystal on polyimide substrate when irradiated with ion beam in oblique direction on uniformly coated polyimide substrate. The inclined irradiation angle of the ion beam was set to 30 degree, 45 degree and 60 degree and the characteristics were observed for 1 minute and 2 minutes at an ion beam irradiation intensity of 600 to 3,000 eV for each angle. The Alignment of the liquid crystals were observed using a polarized microscope after preparing antiparallel specimens. The pretilt angle of the liquid crystal using the crystal rotation method was measured, and the applicability to actual products was evaluated. Experimental results showed that uniformly aligned liquid crystals could be obtained in samples irradiated at 1 and 2 minutes with an ion beam intensity of 1200 eV or higher when irradiated with 30 degree and 45 degree tilted ion beams. And, at 60 tilted degree, It shows that uniformly aligned liquid crystals could be obtained in samples irradiated at 1 and 2 minutes with an ion beam intensity of 2400 eV or higher. The pretilt angle of the liquid crystal showed the best characteristics when irradiated with ion beam inclined at 45 degrees, and it was confirmed that the pretilt angle was 0.2 to 1.3 degrees, which is usable for horizontally oriented LCD.
This is an experimental study where the coefficient of friction between engine pulley and V-Belt is obtained. The experimental method is applied pulleys made of existing steel and aluminium materials. The relative friction workpiece is a v-belt incorporating rubber with cloth. The friction test uses a pin-on-disk friction modulator and measures the coefficient of friction depending on the number of revolutions in the disc. As a result, in the case of aluminum material, there was a sliding phenomenon because the coefficient of friction was small when accelerating and decelerating. Also, the variation of the friction coefficient was severe when the rotation speed was increased or decreased. Therefore, it is considered that the aluminum pulley is slippery even if it is fit to the structural rigidity. Therefore, in order to secure a stable friction coefficient, the pulley groove surface will be surface-treated, a special alloy is added, or a heat treatment is required.
Boundary element solution method is introduced for radiation heat transfer problem with objects inside a 2-D enclosure, where shadow zone exists. Surfaces are assumed as diffuse gray in a transparent medium. Boundary integral and boundary element equations were derived from radiation transfer equation, and their theory is reviewed. Also the process of solution methods to implement the boundary element method is analysed and explained with consideration of shadow effects. BEM solution results are compared with two test problems and are found to be good agreements with the both analytic and ANSYS Fluent numerical solutions. Therefore the current BEM analysis for radiation heat transfer problem can be considered as verified, and their efficacy with engineering applicability is established as a result.
In this study, the air-side cooling capacity and pressure drop of an evaporator for a refrigerator unit were experimentally investigated. Using the calorimeter, the performance of the evaporator was verified by changing the fin shape, fin pitch, tube row and air flow rate. The experimental apparatus consisted of the calorimeter which functioned as a constant temperature and humidity chamber and the refrigeration cycle. In order to select the heat exchanger suitable for the evaporator, both air-side cooling capacity and pressure drop should be considered at the same time. From the evaporator performance test by pin type, wavy pin was selected. The optimal performance of the evaporator was observed at the fin pitch of 5 mm, the tube row of 6 row, and the air flow rate of 40㎥/min.
In this study, a plate heat exchanger was developed for applying to a heat pump system using the heated effluent from a thermal power plant. Since seawater is used as a heat source and a heat sink in this heat pump system, Titanium was chosen as the heat plate material for its high corrosion resistance. One of the purposes of the study was to get an optimized distribution area in the heat plate in order that better thermal performances could be achieved through equal flow rates along the heat transfer area. It was revealed from the performance tests that the mean heat transfer rate and the overall heat transfer coefficient were enhanced by 2.9% and 7.7%, respectively, compared to those measured before the design optimization.
In this paper, we compared and analyzed the performance of the GPS L1/L2 signal with GPS L1 using the navigation system. Generally the GPS receiver calculates the position of the satellite by using the ephemeris data recevied from GSP Satellites, and also calculates the position of its own using the pseudorange. This paper provides an overview of the device which can receive an GPS L1/L2, and compares the GPS L1 with the GPS L2 signal power using the simulator. It was confirmed that the GPS L1/L2 receiver and the GPS L1 receiver met the requirements of standards and it is similar to the navigation performance of the GPS L1 Receiver with the GPS L1/L2 receiver. It was also confirmed that the GPS L2 band can not correct ionospheric error in the navigation system of the combat vehicle.
There is a need to reduce fuel consumption in order to reduce GHG emissions from the transport sector, which accounts for large volumes. In this study, the fuel consumption rate can be compared with the method using the CAN communication data in the engine controller through the OBD II interface and the direct measurement method using the fuel flow meter. For this purpose, we measured the fuel consumption rate in the engine controller and the fuel flow meter with the chassis dynamometer, and confirmed the reliable data of the fuel flow meter. As a result, the fuel consumption rate in the engine controller and the fuel consumption rate in the fuel flow meter were directly measured. After that, the running test was carried out using the chassis dynamometer and the reliability of the fuel consumption rate using the flow meter was confirmed.
The study on the tire noise due to the On-Board Sound Intensity test method. The object of this project is to prepare the countermeasure of the noise reduction according to collect tire/road noise data under various influencing factors by using On-Board Sound Intensity test method. To accomplish the object ; A automotive is used as a test platform to test tire/road noise by changing different types of tires and using On-Board Sound Intensity test system. The influence of inflation pressure, road, load, speed and pattern type on tire/road noise is compared and analyzed. At the same time, the mechanism of tire/road noise is analyzed, which provides a experimental basis for tire noise reduction.
According to the automobile industry has been developing day by day, traffic accidents are increasing and the rear-end collision is the second largest of the entire collision. Due to the high social cost caused by rear-end collision, several studies are in progress at home and abroad. Previous studies have shown that neck injury caused by rear-end collisions can be prevented by seat conditions. In this study, to find the condition that reduces neck injury, change of neck injury in rear-end collision is analyzed according to headrest height, seatback angle, and seatback torque using BioRID II dummy model and passenger behavior analysis program MADYMO. Therefore, it is expected that the condition of each variable to reduce the risk of injury to the neck can be applied to the seat design, which will reduce the injury and the social cost caused by the rear-end collision.
By analyzing the status of Korean tire labeling regulation and comparing the performance indicators of tire labeling in different countries, this paper expounds the serious impact of tire noise on traffic noise pollution, and puts forward that in order to improve the comfort of car ride, control traffic noise pollution and build a green tire industry, the tire labeling system should be improved, and the corresponding requirements for tire rolling noise should be put forward according to the road conditions in Korea.
Glass wool is a fiber made by melting sand and waste glass at high temperature. It has been used as an inorganic fiber for sound absorption, insulation, and non-combustible materials for automobiles, ships, and household appliances. However, the disadvantage comes from the moisture penetration through condensation and cleaning up so that it deteriorates insulation and soundproofing performance. In order to overcome the disadvantages of glass wool, we investigate the water repellency by plating metal on the surface of glass wool with Cu and Ti while coating stability is considered. The thickness of the deposited metal is about 300 nm. The deposition chemicals and the image of the specimen are analyzed by using SEM equipment. The electron microscopic result shows that quite amount of Cu and Ti metals are deposited on the glass wool surface.
This research is about a study on the flow stress of Inconel 601 under hot deformation. For Inconel 601, hot compression tests on gleeble 3500 system under 925℃, 1050℃ and 1150℃ and 0.001/s, and 5/s of strain rates were done. The flow behavior of the Inconel 601 was studied and modeled. In this study, the flow stress was modeled using deep neural network and support vector regression algorithm. The flow stress of Inconel 601 was dependent on strain rate and temperature. It was found that both the deep neural network and support vector regression adequately described the flow stress variation of Inconel 601. However, the model by the support vector regression was found to be superior to the model by the deep neural network. The construction of the model by SVR was more efficient than the construction by DNN. Also the prediction accuracy of the model by SVR was better than the accuracy of the model by DNN. It is found that the MAPE(Mean absolute percentage error) of the DNN based model was 4.89% while the MAPE of the SVR based model was 1.98%.
Due to the concern on global warming, refrigerants having high GWP(Global Warming Potential) are being replaced to low GWP refrigerants. As for small slush maker, R-134a is being to replaced to R-290, whose GWP is 3. In this study, performance tests were conducted on the slush maker having dual evaporator, which was designed to operate using R-290. Results showed that the optimum refrigerant charge amount was 100g. At the charge amount, 61 minutes was needed to make a slush from a raw milk substance, which contained 10% sucrose. The power consumption was 0.89 kW, which yielded COP of 0.252. Tests were further conducted changing the outdoor air temperature. It was resulted that slush-making was possible at all outdoor temperatures except at an extreme temperature of 43°C. Even at the temperature, slush-making was possible if the machine operated with a single evaporator. The COP increased with the decrease of the outdoor temperature.
Glass wool is widely used as a typical soundproofing material because it has superior characteristics as a soundproofing material as well as excellent marketability. However, moisture penetration through condensation and cleaning up causes deterioration of insulation and soundproofing performance. In this study, we evaluate the wettability and sound absorption performance when the metal is deposited on the surface of glass wool. The performance is examined based on parameters such as the angle test, drying speed, the absorbency, the moisture content, the wettability. The wettability data shows that Cu coated glass wool is the best performance compaed to Ti coated one. The sound insulation characteristics are also compared by using the impedance tube. At the low frequency range, there is no difference among the test specimens, however, at the frequency above the 250 Hz range, Cu coating shows 10 % better in th sound asorption. Ti coating has almost same to the existing glasss wool performance. It turns out that metal coating on the glass wool seems to be very promising: the metal deposition reveals strong water repellency and sound absorption performance is equivalent to the existing glass wool.
In this study, the characteristics of the heat flow on SA(supply air) side of the white smoke reducing heat exchange system according to the change of SA velocity were analyzed in the winter condition (outside temperature 0℃). Also, the mixing process of SA and the EA(exhaust air) is presented in the psychrometric chart to confirm the possibility of reducing white smoke. Solidworks flow simulation was used to analyze the heat flow on the heat exchange system under uniform conditions. As the inflow velocity of SA increased, the temperature of SA decreased due to the convective heat transfer improvement due to the active flow in SA system. And the outlet temperature and absolute humidity of the mixing zone decreased significantly. At SA velocity 7 m/s, the outlet temperature and absolute humidity decreased to about 58% and 82%, respectively.
In this paper, we investigate the relationship between fuel injection quantity and voltage and current energy of Bosch system and Delphi system by measuring the high and low voltage waveform, current waveform, fuel injection quantity and fuel pressure of A and J-engines. Waveform measurements are made using the PICO scope and the CDS tester. The injectors of A and J engines were tested under no load condition using injector with normal fuel injection quantity, injector with small fuel injection quantity and injector with many fuel injection quantity. In case of normal injector, A-engine has higher fuel pressure, injection interval time, voltage energy, and current energy than J-engine. The current energy of the A-engine changed linearly compared to that of the J-engine. For over and under injectors, the change in the previous physical quantity was greater for the A-engine than for the J-engine. However, the duration time of maintaining to open the injector is controlled differently, and so the voltage and current energy values are changed, and the change of the current energy is larger than the voltage energy.
Hot forging is widely used to manufacture many industrial parts such as machine, automotive and so on. It is important to simulate the relations or characteristics between preform and die before designing the die. The purpose of this study is to investigate the forging characteristics of parking gear with nonlinear gear groove, thus the behaviors of preform can be predicted in advance and finally they can be applied to die design. As the results, since the distributions of high effective strain rate of parking gear were less than 3%, it was predicted that the manufacturing of parking gear with nonlinear gear groove might be possible. Furthermore it was observed that, in this study, the effective stress of bottom die was lower than that of top die.