• Transactions of the Korean Society of Automotive Engineers
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• v.9 no.1
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• pp.28-36
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• 2001

In this study, a zero-dimensional two zone model is developed to investigate the effects of valve overlap period and valve lift on combustion and gas exchange process in SI engine. The simulation results show that the predicted data has good agreements with experimental ones. The useful information of combustion and gas exchange process such as residual gas fraction, cylinder pressure, mass flow rate and volumetric efficiency can be obtained and the effects of engine variables on combustion processes and performances can be evaluated.

• Transactions of the Korean Society of Mechanical Engineers
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• v.16 no.1
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• pp.175-179
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• 1992

Generally speaking, natural gas possesses several characteristics that make it desirable as an engine fuel : for example (1) lower production cost, (2) abundant commodity and (3) cleaner energy source than gasoline. Due to the physical characteristics of natural gas, the volumetric efficiency and flame speed of a natural gas engine are lower than those of a gasoline engine, which results in a power loss of 10-20% when compared to a convensional gasoline engine. This paper describes the results of a research to improve the performance of a natural gas engine through the modification and controls of air/fuel ratio, spark timing advance and supercharging effect by forced air supply method.

• Transactions of the Korean Society of Automotive Engineers
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• v.11 no.6
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• pp.30-36
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• 2003

Variable valve timing(VVT) mechanisms are used widely for improving fuel consumption and reducing emissions. Most of application, however, are limited in the DOHC engine. Dual equal retard/advance strategy is relatively simple one and can be applied to both SOHC and DOHC engines. In this study, effects of dual equal valve timing retard/advance are investigated to observe the feasibility of VVT system on an SOHC SI engine. The result shows that fuel economy and emissions are improved in the dual retard condition due to increased internal EGR. Some amount of increase in volumetric efficiency can be achieved by advancing valve timing at low speed and by retarding at high speed. In this case, however, full load power is not so much improved as the volumetric efficiency increases because of severe knock. In the dual advance condition, there is no merit in the fuel economy and emission.

• The KSFM Journal of Fluid Machinery
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• v.2 no.4 s.5
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• pp.24-30
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• 1999

An analytical study has been carried out to investigate the effects of the check valve installation on the volumetric and adiabatic efficiencies in a scroll compressor. Both the valve displacement limit and the valve stiffness affected the valve motion, the pressure upstream of the valve, and the pattern of the mass flow through the valve to the discharge plenum. Nonetheless, the presence of the check valve did not cause any noticeable change in the volumetric efficiency. Only a slight increase in the compression work was needed to overcome the pressure increase in front of the valve. The pressure build-up upstream of the valve can be alleviated with the larger limit of the valve lift and a smaller valve stiffness.

• Microbiology and Biotechnology Letters
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• v.24 no.6
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• pp.738-742
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• 1996

An efficient packed-bed type biofilm reactor charged with immobilized phototrophs was developed to treat organic wastewater at an extremely high volumetric loading rate. The packed bed reactor (PBR) charged with porous ceramic beads was superior to a fluidized-bed reactor suspended with activated carbon powders in terms of many aspects such as BOD removal efficiency, operational stability, and overall economics. For wastewater with BOD concentration as high as 20, 000mg/l, the BOD removal efficiency was maintained above 90% when the hydraulic retention time (HRT) was longer than 1 day. The allowable volumetric BOD loading rate of this reactor (20gBOD/l day) is more than ten-folds higher than that of an ordinary activated sludge method. The behaviour of the reactor was represented well by a Monod type kinetic equation with a maximum specific BOD loading rate(P) of 22.2gBOD/l day and a half saturation constant(K$_{s}$) of 1, 750 mgBOD/l.

• Journal of Advanced Marine Engineering and Technology
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• v.17 no.4
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• pp.11-19
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• 1993

The experimental study was carried out to investigate the stability and the performance characteristics of the aero-valved pulsating combustion system with maximum operating capacity of 60KW. The effect of geometry of combustion system on the stable condition, the flammability limit, the total pressure oscillation amplitude, and the operating frequency can be identified, and the maximum turn-down-ratio is obtained up to 3.3. The total pressure oscillation amplitude can be controlled by tunning the length of the air inlet pipe. The empirical equation with which the operating frequency can be approximated is proposed and the discrepancy is within 5%. The volumetric efficiency is identified to be one of the important parameters determining the upper flammability limit and the maximum value of which is approximately 22%.

• Journal of Advanced Marine Engineering and Technology
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• v.22 no.1
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• pp.42-51
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• 1998

A 150 m$\^$3//hr, 30 kg/cm$\^$2/, air-cooled 3-stage reciprocating air compressor is designed to be used in starting large diesel engines of ships. A basic design procedure is presented to meet the targeted pressure and flow rate, and especially a volumetric efficiency of 80%. Temperature and stress analysis of the 1st stage cylinder are performed using axisymmetric FEM modelings. The dynamics of valve system is analyzed and stress at the 1st stage valve seat caused by valve impact is evaluated. To reduce friction loss and wear at the compressor engine system tribological design issues are reviewed and good design practices are suggested. Finally, forced-air pin-type interstage coolers are designed to dissipate generated compression heat at each stage.

• Proceedings of the SAREK Conference
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• 2005.11a
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• pp.564-569
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• 2005

Recently, from the viewpoint of global wanning, natural gas CO2 is considered as a main refrigerant for hot water system. The characteristics of CO2 is not toxic, not flammable, high pressure, and high refrigerating capacity. Also it is widely available as a byproduct of industrial processes. This paper describes the performance analysis program of the swash plate type compressor using CO2 refrigerant. Estimates of the refrigerant flow rate, compression work, discharge temperature and volumetric, compressor efficiencies of the CO2 swash plate type compressor are obtained from the various design parameter such as the inclination angle of the swash plate, discharge hole area and suction hole area.

• Transactions of The Korea Fluid Power Systems Society
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• v.8 no.1
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• pp.10-18
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• 2011

In the beginning of this study, pressure in a cylinder and flow rate from a cylinder of a rotating-cam and fixed-cylinder type radial piston pump are investigated through numerical simulations, so that the simulation results might be utilized as basements for examining physical phenomena occurring in the pump assembly. Then, for supplying basic knowledge on pump design, pressure, flow and leakage characteristics of the pump assembly under the variations of major design parameters are investigated through numerical simulations. At the end, key design parameters influencing upon volumetric efficiency of the pump are listed.

• Journal of Aquaculture
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• v.16 no.4
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• pp.203-209
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• 2003

Nitrification efficiency of fixed film biofilters with sand, loess bead, and styrofoam bead in biofilter columns of 1-m height and 30 cm width was studied. Synthetic wastewater was continuously supplied to the culture tank to maintain total ammonia nitrogen (TAN) concentration in the inflow water at around 8 mg/L. The hydraulic loading rate was set at 200 ㎥/$m^2$/day. TAN conversion was stabilized after about 90 day conditioning for all the selected filter media but with net accumulations of nitrite. On the volumetric basis, conversion rates of TAN and nitrite were the highest in styrofoam bead filter. Mean volumetric TAN conversion rates in the final samples were 682, 269, and 79 g TAN/㎥/day in the styrofoam bead, sand and loess bead filters, respectively. Low gravity and cost of styrofoam bead render the handling easier and more cost-effective.