• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.13 no.3
• /
• pp.1008-1013
• /
• 2012

Electro-hydraulic power steering (EHPS) system is the power-assisted steering which operates the hydraulic pump by BLDC motors for assisting the steering force. EHPS consists of BLDC motor, gear pump, oil-hydraulic circuit and steering system. Since EHPS is a convergence system consisting of electricity and electronic, hydraulic and mechanical system, it is difficult to establish the simulation model. In this paper, the mathematical model of EHPS system components were presented, and the simulations of the multi-domain system were performed by using AMESim. The trial and error of development would be reduced by using this simulation results, and it would be helpful for developing high-quality EHPS.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
• /
• 1998.04a
• /
• pp.321-327
• /
• 1998

This paper presented a case study on the application of on-line wear monitoring technique to a high duty air-turbo-compressor system. Main objects monitored were a gear unit and metal bearings, both shown frequent troubles due to the severe operation conditions at heavy dynamic load. The air-turbo-compressor system needs secure condition monitoring because it is one of the main utilities in steel making industry. Temperature and vibration characteristics have been mainly on-line monitored in this system for a predictive maintenance; however, it has been shown that they are not fairly good enough to give an early warning prior to the machine failure. In this work, an on-line Opto Magnetic Detector(OMD) was implemented for an on-line wear monitoring, which quantitatively measured the contamination level of both ferrous and non-ferrous wear particles by detecting the change in optical density of used oil. Results showed that the application of on-line OMD system was satisfactory in diagnosis of the machine system.

• Proceedings of the Korean Society of Marine Engineers Conference
• /
• 2005.11a
• /
• pp.240-241
• /
• 2005

The experiments were conducted without oil in a closed refrigerant loop which was driven by a magnetic gear pump. The main components of the refrigerant loop are a receiver, a variable-speed pump, a mass flow meter, a pre-heater and evaporator(test section). The test section was made of a horizontal stainless steel tube with the inner diameter of 4.57 mm, and length of 4 m. The experiments were conducted at mass flux of 200 to 700 kg/$m^2s$, saturation temperature of 0$^{circ}C$ to 20$^{circ}C$, and heat flux of 10 to 30 kW/$m^2$. The test results showed the evaporation heat transfer of $CO_2$ has great effect on more nucleate boiling than convective boiling. The evaporation heat transfer coefficients of $CO_2$ are highly dependent on the vapor quality, heat flux and saturation temperature. In comparison with test results and existing correlations, correlations failed to predict the evaporation heat transfer coefficient of $CO_2$, therefore, it is necessary to develop reliable and accurate predictions determining the evaporation heat transfer coefficient of $CO_2$ in a horizontal tube.

• Journal of the Korean Society for Precision Engineering
• /
• v.30 no.7
• /
• pp.667-672
• /
• 2013

This paper presents the development of a condition monitoring system that monitors the operating conditions of a reduction unit, such as the bearing temperature, gearbox vibration, and gear oil deterioration, and notifies the operator of potential problems or abnormal conditions. A series of field tests on high-speed rail and conventional lines was performed to identify the characteristics of temperature rise and vibration levels on the reduction unit during operation. The monitoring system was designed based on the proper sensor selection, measurement method, and signal analysis to optimize the interface with the operating system of high-speed trains. Application of this monitoring system to high-speed trains will play an important role in their proper maintenance and safe operation.

• Agricultural and Biosystems Engineering
• /
• v.6 no.2
• /
• pp.65-69
• /
• 2005

A windheat generation system with a Savonius windturbine was developed and the performance was evaluated through field tests. The system consisted of a heat generation drum, heat exchanger, water storage tank, and two circulation pumps. Frictional heat is created by rotation of a rotor inside the drum containing thermo oil, and was used to heat water. In order to estimate the capacity of this windheat generation system, weather data was collected for one year at the site near the windheat generation system. Wind Power from the savonius wind turbine mill was transmitted to the heat generation system with an one-to-three gear system. Starting force to rotate the savonius wind turbine and the whole system including the windheat generation system were 1.0 and 2.5 kg, respectively. Under the outdoor wind condition, maximum speed of the rotor in the drum was 75rpm at wind speed 6.5 m/sec, which was not fast enough to produce heat for greenhouse heating. Annual cumulative hours for wind speeds greater than 5 m/sec at height of 10, 20, 30 m were 190, 300 and 1020 hrs, respectively. A $5^{\circ}C$ increase in water temperature was achieved by the windheat generation system under the tested wind environment.

• Journal of the Korean Society of Manufacturing Process Engineers
• /
• v.18 no.10
• /
• pp.54-59
• /
• 2019

The final reduction drive in tactical vehicles has a wear-pad that helps to maintain adequate end floating when the hub assay operates. The input axis and sun gear move repeatedly with the axis when tactical vehicle is operating. The hub assay is designed so that the wear pads won't seize during operation. Seizure of the wear pads during operation results in oil leakage. In our study, the fault mechanism was analyzed to prevent the seizure of the wear pads and an optimal design for the shape and material of the wear-pad was explored. We then observed the changes in temperature, shape, and material of several important parts.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.16 no.12
• /
• pp.1134-1139
• /
• 2004

The evaporative heat transfer coefficient of $CO_2$ (R-744) in a horizontal tube was investigated experimentally. The experiments were conducted without oil in a closed refrigerant loop which was driven by a magnetic gear pump. The main components of the refrigerant loop are a receiver, a variable-speed pump, a mass flow meter, a pre-heater and evaporator (test section). The test section consists of a smooth, horizontal stainless steel tube of inner diameter of 7.75 mm. The experiments were conducted at mass flux of 200 to 500 kg/m$^2$s, saturation temperature of -5 to 5$^{\circ}C$, and heat flux of 10 to 40kW/m$^2$. The test results showed the heat transfer of $CO_2$ has a greater effect on nucleate boiling more than convective boiling. Mass flux of $CO_2$ does not affect nucleate boiling too much, and the effect of mass flux on evaporative heat transfer of $CO_2$ is much smaller than that of refrigerant R-22 and R-134a. In comparison with test results and existing correlations, correlations failed to predict the evaporative heat transfer coefficient of $CO_2$, therefore, it is necessary to develope reliable and accurate predictions determining the evaporative heat transfer coefficient of $CO_2$ in a horizontal tube.

• Journal of Biosystems Engineering
• /
• v.43 no.1
• /
• pp.1-13
• /
• 2018

Purpose: The development of compact tractors that can be used in dry fields, greenhouses, and orchards for pest control, weeding, transportation, and harvesting is necessary. The development and performance evaluation of power transmission units are very important when it comes to tractor development. This study evaluates the performance of a driving power transmission unit of a 50 kW multi-purpose narrow tractor. Methods: The performance of the transmission and forward-reverse clutch, which are the main components of the driving power transmission unit of multi-purpose narrow tractors, was evaluated herein. The transmission performance was evaluated in terms of power transmission efficiency, noise, and axle load, while the forward-reverse clutch performance was evaluated in terms of durability. The transmission's power transmission efficiency accounts for the measurement of transmission losses, which occur in the transmission's gear, bearing, and oil seal. The motor's power was input in the transmission's input shaft. The rotational speed and torque were measured in the final output shaft. The noise was measured at each speed level after installing a microphone on the left, right, and upper sides. The axle load test was performed through a continuous equilibrium load test, in which a constant load was continuously applied. The forward-reverse clutch performance was calculated using the engine torque to axle torque ratio with the assembled engine and transmission. Results: The loss of power in the transmission efficiency test of the driving power unit was 6.0-9.7 kW based on all gear steps. This loss of horsepower was equal to 11-18% of the input power (52 kW). The transmission efficiency of the driving power unit was 81.5-89.0%. The noise of the driving power unit was 50-57 dB at 800 rpm, 70-77 dB at 1600 rpm, and 76-83 dB at 2400 rpm. The axle load test verified that the input torque and axle revolutions were constant. The results of the forward-reverse clutch performance test revealed that hydraulic pressure and torque changes were stably maintained when moving forward or backward, and its operation met the hydraulic design standards. Conclusions: When comprehensively examined, these research results were similar to the main driving power transmission systems from USA and Japan in terms of performance. Based on these results, tractor prototypes are expected to be created and supplied to farmhouses after going through sufficient in-situ adaptability tests.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.39 no.12
• /
• pp.1237-1244
• /
• 2015

A gerotor can be manufactured in a miniature size because it has a high discharge per cycle and a simple structure. Gerotors are widely used for the lubrication oil of an engine and as the hydraulic source of an automatic transmission. Recently, improvements in fuel efficiency and noise reduction have come to the fore in the automobile industry, and it has been necessary for better fuel efficiency to continuously improve the flow rate and noise of internal gear pumps through the optimal design of the gerotor and port shape. In this study, gerotors were generated based on the equations derived for a lobe shape with multiple profiles (ellipse 1-elliptical involute-ellipse 2). The ranges of the design parameters were considered to prevent a cusp and loop. In addition, the optimal lobe shape was obtained by determining the influence of the lobe shape on the performances (flow rate, irregularity, etc.), according to the values of the design parameters.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.15 no.6
• /
• pp.4002-4006
• /
• 2014

The automotive exhaust gases generated by the vehicles containing carbon monoxide, hydrocarbons and lead, is a large concern because of their harm to human health or the living environment. To reduce exhaust gas, it is important to develop a variety of techniques that are currently being used by elemental analysis to determine the optimal conditions. In this study, the anti-freeze coolant contained in the exhaust gas was examined, which can affect the emissions. The effects of the commercially available coolant from five domestic companies on the HC, NOx and $CO_2$ emissions were analyzed to determine the optimal amount of antifreeze. In addition, antifreeze products from the five companies were analyzed with respect to driving time of the cooling fan and the correlation of the NOx emission analysis. The temperature of the engine oil was matched using a manual gear of small passenger inspection standard speed $40{\pm}2Km/h$ so the vehicle could meet the specifications for inspection $90{\sim}93^{\circ}C$. The Company D fan operation time resulted in the shortest antifreeze, $CO_2$ and NOx emissions.