• Transactions of The Korea Fluid Power Systems Society
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• v.5 no.1
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• pp.6-12
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• 2008

ISO pneumatic cylinder reliability test requires air leakage measurement. Air cylinder has many parts and the leakage shall be measured before, during and after endurance test, and, the leakage should smaller than the specified value. The existing measurement method needs complex operation and the calibration of leak detector, and, has to separate the testing cylinder from endurance test device, which causes the change of contact condition of seal in the cylinder. Therefore, it is hard to evaluate the air leakage during endurance test, and guarantee the reliability of the conventional measurement method. In this paper, a new method for air leakage measurement using isothermal chamber, which does not requires calibration or temperature compensation, and, can measure air leakage accurately with quite simple operations, is proposed. As a result, reliability of air leakage measurement can be improved because the proposed method does not have to separate the testing cylinder from the endurance test device for air leakage measurement. The effectiveness of the proposed method is proved by error analysis of leak measurement from experimental result.

• International Journal of Automotive Technology
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• v.2 no.3
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• pp.93-101
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• 2001

Distribution of fuel-air mixture has a strong influence on performance and emissions of a compressed natural gas (CNG) engine. In this paper, parametric study is performed by KIVA-3V to investigate fuel-air mixture with respect to injection timing, cycle equivalence ratio and engine speed. With open-valve injection intensive mixing during intake and compression stroke results in relatively homogeneous mixture in the cylinder. Sequential induction of fuel-air mixture and fresh air results in stratification in the cylinder among the test cases at closed-valve injection. There is close similarity in the calculated distributions of the mixture in the cylinder with different cycle equivalence ratios and engine speeds. The results are compared against pressure traces and flame images obtained in a single cylinder engine converted from a 11L six-cylinder heavy duty diesel engine.

• Transactions of the Korean hydrogen and new energy society
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• v.20 no.2
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• pp.125-132
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• 2009

Cylinder shaped air-breathing PEMFC has been developed to have small volume, low contact resistance and better air accessibility to the open cathode. This cylinder shaped design consists of an anode cylinder with helical flow channel and a cathode current collector with slits. The pressure distribution measurement according to the shapes was performed. The test result indicated that cylinder shaped fuel cell has better pressure distribution compared with the planar shaped fuel cell. The better pressure distribution was connected to the higher performance. The maximum power density of cylinder shaped fuel cell was about 20% higher than the planar shaped fuel cell. The maximum power density of the developed cylinder shaped air-breathing PEMFC with dry hydrogen was $220\;mW/cm^2$ and with humidified hydrogen was $293\;mW/cm^2$.

• Transactions of the Korean Society of Automotive Engineers
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• v.11 no.3
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• pp.20-27
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• 2003

In this paper, the fuel transport characteristics during transient condition was studied by using a Fast Response Flame Ionization Detector(FRFID). The quantitative measurement method for the inducted fuel mass into cylinder is studied. The inducted fuel mass into the cylinder was estimated by using calculated air-fuel ratio by hydrocarbon concentration of cylinder and air flow model. In order to estimate the transportation of injected fuel from the intake port into cylinder, the wall wetting fuel model was used. The two coefficient $\alpha$,$\beta$) of the wall-wetting fuel model was determined from the measured fuel mass that was inducted into the cylinder at the first cycle after injection cut-off To reduce an air/fuel ratio fluctuation during rapid throttle opening, the appropriate fuel injection rate was obtain from the wall wetting model with empirical coefficients. Result of air/fuel ratio control, air/fuel excursion was reduced.

• Transactions of the Korean Society of Automotive Engineers
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• v.25 no.3
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• pp.336-343
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• 2017

Intake air conditions, such as air temperature, pressure, and humidity, are very important parameters that influence engine performance including combustion and emissions characteristics. The purpose of this study is to investigate the effects of intake air temperature on combustion and exhaust emissions characteristics in a single cylinder diesel engine. In this experiment, an air cooler and a heater were installed on the intake air line and a gas flow controller was installed to maintain the flow rate. It was found that intake air temperature induced the evaporation characteristics of the fuel, and it affects the maximum in-cylinder pressure, IMEP(indicated mean effective pressure), and fuel consumption. As the temperature of intake air decreases, the fuel evaporation characteristics deteriorate even as the fuel temperature has reached the auto-ignition temperature, so that ignition delay is prolonged and the maximum pressure of cylinder is also reduced. Based on the increase in intake air temperature, nitrogen oxides(NOx) increased. In addition, the carbon monoxide(CO) and unburned hydrocarbons(UHC) increased due to incomplete fuel combustion at low intake air temperatures.

• Transactions of the Korean Society of Automotive Engineers
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• v.4 no.3
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• pp.92-101
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• 1996

In a gasoline engine, the characteristics of air flow is very important not only for the design of the intake system geometry bout also for the accurate measurement of the induction air mass. In this study, an air flow rate measurement of the induction air mass. In this study, an air flow rate measurement was conducted by using the hot wire flow meter at the upstream of the intake port and the throttle. At the upstream of the throttle, the overshoot phenomena of the air flow rate by fast throttle opening were analyzed with choked flow. At the upstream of the intake port, the cylinder variation of the air flow rate and the difference between fast throttle opening and closing were showed during the unsteady state by the throttle step change. The results of this study can be used for the design of the throttle valve geometry and cylinder by cylinder control.

• The Magazine of the Society of Air-Conditioning and Refrigerating Engineers of Korea
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• v.8 no.2
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• pp.73-80
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• 1979

This study describes the conduction of heat in the discharge head of air compressor. It also gives a base for a finite elements analysis of two dimenional steady -state heat conduction in the cylinder head of air cooled type reciprocating compressor. Using a single cylinder compressor operated at a given speed, tests were made observing outside temperature, final pressure and discharge temperature of air in cylinder head. As a result, the following were obtained : (1) The rate oi heat flow from the inner surface of discharge head to outside wall reach 46. 328 kcal /h at a speed of 796rpm under the constant temperature of inlet air. (2) The compression work of air increase in accordance with temperature rise of inlet air.

• Journal of ILASS-Korea
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• v.28 no.4
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• pp.198-206
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• 2023

In this study, visualization of in-cylinder spray behavior and spark channel stretching by air flow characteristics depending on engine operating conditions were investigated. For in-cylinder spray behavior, increase in engine rpm did not alter the counter-clockwise air flow direction and location of in-cylinder dominant air flow but increased average air flow velocity, which hindered spray propagation parallel to the piston surface. When injection timing was retarded, direction of in-cylinder dominant air flow was changed, and average air flow velocity was reduced resulting in an increase in spray penetration length and change in direction. For spark channel stretching, increase in air flow speed did not affect spark channel stretch direction but affected length due to increase in spark channel resistance and limitation of energy ignition coil can handle. Change in air flow direction affected spark channel stretch direction where the air flow was obstructed by ground electrode which caused spark channel direction to occur in the opposing direction of air flow. It also affected spark channel stretch length due to change in air flow speed around the spark plug electrode from the interaction between the air flow and ground electrode.

• Journal of ILASS-Korea
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• v.26 no.1
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• pp.18-25
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• 2021

The objective of this study is to investigate the effect of cryogenic intake air temperature on the injected fuel droplet behavior in a compression ignition engine under the different start of energizing timing. To achieve this, the intake air temperatures were changed from -18℃ to 18℃ in steps of 9℃, and the result of fuel evaporation rate, Sauter mean diameter, and equivalence ratio distributions were compared. When the intake air temperature decreased in steps of 9℃, less fuel was evaporated by about 3.33% because the cylinder temperature was decreased. In addition, the evaporated fuel amount was increased with retarding the start of energizing timing because the cylinder temperature raised. However, the difference was decreased according to the retarded start of energizing timing because the cylinder pressure was also increased at the start of fuel injection. The equivalence ratio was reduced by 5.94% with decreasing the intake air temperature. In addition, the ignition delay was expected to longer because of the deteriorated evaporation performance and the reduced cylinder pressure by the low intake air temperature.

• 한국전산유체공학회:학술대회논문집
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• 2008.03b
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• pp.272-275
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• 2008

One of the important operating factors for the air-fuel pre-mixed conditions in an HCCI engine is an in-cylinder flow. In this study, unsteady in-cylinder air flow characteristics in a diesel engine as a reference engine of an HCCI engine development were numerically analysed. Unsteady flow analyses were conducted with the combination of 3 intake port inlets, then the in-cylinder air flow distribution and swirl ratio results from a case were compared with the results from the other cases.