• Journal of ILASS-Korea
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• v.16 no.1
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• pp.1-6
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• 2011

In recent years, the need for more fuel-efficient and lower-emission vehicles has driven the technical development of alternative fuels such as LPG (Liquefied Petroleum Gas) which is able to meet the limits of better emission levels without many modifications to current engine design. LPG has a high vapor pressure and lower viscosity and surface tension than diesel and gasoline fuels. These different fuel characteristics make it difficult to directly apply the conventional gasoline or diesel fuel pump. Self acting lubricated groove design or coating can be used in high-speed and high precision spindle system like a roller-vane type fuel pump, because of its advantages such as low frictional loss, low heat generation, averaging effect leading better running accuracy and simplicity in manufacturing. Those design method can also affect the atomization of fuel from the injector and the formation of fuel film on the intake manifold. In this study, experiments are carried out to get performance characteristics of initial and steady state operation, The characteristics of vane type fuel pump were investigated to access the applicability on LPLi engine.

• Journal of Advanced Marine Engineering and Technology
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• v.30 no.6
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• pp.693-701
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• 2006

The present work investigates the local heat transfer characteristics and the associated frictional loss in a rectangular channel with inclined solid and perforated baffles to obtain the basic design data for gas turbine. Five different geometries of baffles such as 1) solid (without hole), 2) three holes, 3) six holes, 4) nine holes, 5) twelve holes were covered. A combination of two baffles of same overall size is used. The flow Reynolds number is ranged from 28,900 to 70,100. The placement of baffles augments the overall heat transfer greatly by combining both jet impingement and the boundary layer separation. The present results show that the average Nusselt number distribution is strongly dependent on number of holes in the baffle plates, i.e., the average Nusselt number increases with increasing number of holes. The friction factor decreases also with increasing the number of holes. however. its value increases with increasing the Reynolds number.

• Proceedings of the Korean Society of Marine Engineers Conference
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• 2006.06a
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• pp.45-46
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• 2006

Experimental and numerical analysis on the heat transfer behaviors and the associated frictional loss in a rectangular channel with two inclined perforated baffles($\;5^{\circ}$) mounted on the bottom plate has been systematically performed. The parametric effects of perforated baffles (3, 6, 9 holes) and flow Reynolds number on heat transfer characteristics of the heated target surface are explored. A combination of two baffles of same overall size was considered and the flow Reynolds number for this study is varied between 28,900 and 61,800. Comparisons of the experimental data with the numerical results by commercial code CFX 5.7 are made. As for the investigation of heat transfer behaviors on local Nusselt number with the two baffles installed at $x/D_h=0.8\;and\;x/D_h=8.0$, it is evident that there exist an optimum perforation density to maximize heat transfer coefficients; i.e., the maximum Nusselt number decreases with increasing number of holes.

• Proceedings of the SAREK Conference
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• 2009.06a
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• pp.904-909
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• 2009

In this paper, a rolling piston rotary compressor having a combined vane and roller unit has been introduced. In a conventional rotary compressor, sliding motion takes place between the vane nose and roller. By combining the vane and the roller in one unit, gas leakage through a clearance between the vane nose and the roller can be eliminated, and the frictional loss between them can also be reduced to almost nought. Compressor model with the combined vane and roller has been fabricated and tested in a compressor calorimeter and computer simulation program has been developed to confirm merits of the new mechanism. In a test, cooling capacity has been found to be increased by 1.4%, and the compressor input decreased by 0.3%, resulting in 1.7% increased in EER. Simulation program confirmed the calorimeter test results and the merits of the new model as mentioned above.

• Transactions of the Korean Society of Automotive Engineers
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• v.17 no.1
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• pp.72-79
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• 2009

Recently, the internal combustion engines have focused on reducing the $CO_2$ gas in order to cope with severe regulations for fuel economy. Therefore, various new technologies have been developed. Among them, cooling system is spotlighted because it has great effect on fuel economy. In this study, we measured the friction losses of engine parts according to engine speed and oil temperature. We also obtained optimized oil temperature which has the minimum friction losses. Then, we selected optimized oil temperature range and gave informations of friction losses for each engine parts. In addition, we analyzed relationship between coolant temperature and oil temperature by using engine performance test system. From this experiment, we obtained the database for relationship between coolant temperature and oil temperature. Then, we found the optimal temperature about engine oil. We analyzed BSFC and exhaust emissions by controlling the high coolant temperture. If we controlled coolant temperature more higher, BSFC has a little difference but exhaust emissions such as THC and CO have reduced. By using these experimental results, we predicted that IC engine have more low fuel consumption and exhaust emissions by optimized cooling control strategy.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.26 no.4
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• pp.151-157
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• 2014

An algebraic scroll expander has been fabricated and tested in a R134a Rankine cycle with heat source of 20 kW. For the operating conditions of 20~26 bar and $90{\sim}93^{\circ}C$ at the expander inlet and 8~9 bar at the outlet, the expander produced the shaft output power of about 0.6~0.7 kW in the operating speed range of 1500~2000 rpm. These correspond to the expander efficiency of 40~45%. The volumetric efficiency increased with increasing of the expander speed, reaching to 80% at 2000 rpm. Comparing to numerical simulation results, mechanical efficiency from the test data was found to be considerably low by as much as 30%, indicating that reduction in the frictional loss should be made to improve the scroll expander efficiency.

• Transactions of The Korea Fluid Power Systems Society
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• v.5 no.4
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• pp.17-25
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• 2008

This study presents an analytical model of the pneumatic circuit of an air suspension system to analyze the characteristics of vehicle height control. The analytical model was developed through the co-simulation of Simulink(air spring) and HyPneu(pneumatic circuit). Variant effective area of air spring and flow coefficients of pneumatic valves were estimated experimentally prior to the system test, and utilized in simulation. One-comer test apparatus was established using the components of commercial air suspension products. The results of simulation and experiment were so close that the proposed analytical model in this study was validated. However the frictional loss of conduit and heat dissipation which were ignored in this study need to be considered in future study. As an application example of proposed analytical model, an alternative pneumatic circuit of air suspension to conventional WABCO circuit was evaluated. The comparison of simulation results of WABCO circuit and alternative circuit show that proposed analytical model of co-simulation in this study is useful for the study of pneumatic system of automotive air suspension.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1999.05a
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• pp.434-437
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• 1999

An EM pump is used for the purpose of transporting the electrically conducting liquid sodium of the high temperature that is used as a coolant in the liquid metal reactor. In the present study, the pilot pump has been designed and manufactured for the high temperature of $600^{\circ}C$ by the equivalent circuit materials and the consideration of the materials and functions. The length and diameter of the pump are given as 84 cm and 10 cm each due to the fixed geometry of the circulation system to be installed. The characteristic of the developing pressure and efficiency is found out by using Laithewaite\`s standard design formula. It is shown that the developing pressure and efficiency are maximized at the frequency of 15 Hz from the curve. The annular channel gap of 3.95 mm is selected in the range of the reasonable hydraulic frictional loss. The components of the pump consist of the material for the high temperature. And then, the pump is manufactured to have the nominal flowrate of 40 1/min and developing Pressure of 1.3 bar.

• International Journal of Air-Conditioning and Refrigeration
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• v.16 no.4
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• pp.124-129
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• 2008

Design practice has been made on an oil-less scroll air compressor as an air supply device for a 2 kW fuel cell system where air pressure of 2 bar and flow rate of 120 liter/min are required. Basic structure of the scroll compressor includes double-sided scroll wrap for the orbiting scroll driven by two crankshafts connected to each other by a timing belt. These features can eliminate thrust surface which otherwise would produce frictional heat and jeopardize reliable operation of the orbiting scroll and the scroll element's deformation as well. This study focuses on optimum scroll wrap design; orbiting radius has been chosen as an independent design parameter. As the orbiting radius changes, scroll sizes such as scroll base plate and discharge port diameters change accordingly. Gas compression-related losses and mechanical loss also change with the orbiting radius. With a scroll base plate diameter of 120mm at most and discharge port of at least 10mm, the orbiting radius should be within the range of 2.5-4.0mm. With this range of the orbiting radius, it was estimated by performance analysis that the compressor efficiency reached to a maximum of ${\eta}_c$=96% at the orbiting radius of $r_s$=3.5mm for the scroll wrap height-to-thickness ratio of h/t=5.

• Tribology and Lubricants
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• v.35 no.5
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• pp.317-322
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• 2019

In spite of progress in tribological research, machine component failure due to friction and wear has been reported frequently. This failure may lead to secondary damage that can cause huge expense for maintenance and repair. To prevent economic loss, it is important to detect and predict the initial failure point. In this sense, various researchers have been tried to develop Condition Monitoring (CM) method using Acoustic Emission (AE) generated while the materials undergo failure. In this study, effect of particles on friction and wear was investigated using the pin-on-plate friction test and AE signal was recorded with a band-width type AE sensor. The experiments were performed in dry and lubricant conditions using steel and glass as specimens. After the experiment, 3D laser microscope image was captured to evaluate the wear behavior quantitatively. The AE signal was analyzed in time-domain and frequency-domain. The amplitude was compared with the frictional results. The results of this study showed that particle generation accelerate wear, generate high magnitude AE signal and change the frequency characteristics of the signal. Also, lubricant condition test results showed low coefficient of friction, low wear rate, and low magnitude of AE signal compared to the dry condition. It is expected that the results of this study will aid in better assessment of wear in CM technology