• 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.

• 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 Society of Automotive Engineers
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• v.7 no.7
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• pp.66-75
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• 1999

Many researchers have developed the measurement technique of in-cylinder flow. Recently, there are lots of studies on steady flow with different SCV geometries. In this study the flow characteristics of four-valve cylinder head were examined in a steady test rig for different SCV open ratios. Each swirl ratio of several SCV angle was quantified by swirl impulse meter and 2D-LDV measurement. The results showed that the swirl ratio was controlled between 2.3 and 3.8 based on SCV angles. The velocity distributions of in-cylinder flow field were measured by 2-D LDV test and visualized swirl and tumble flow pattern at different positions. In this engine , we found out that the swirl was dominant flow.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.30 no.11 s.254
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• pp.1066-1073
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• 2006

Recently, because the variable induction systems are adopted to intake system, in-cylinder flow induced by induction system is very complex. Therefore it is very difficult to describe the in-cylinder bulk flow characteristics using the conventional swirl or tumble coefficient. In this study, in order to clarify the 3-D angular flow characteristics of in-cylinder bulk motion in the developing process of variable induction system, we introduced the new 3-D angular flow index, angular flow coefficient($N_B$) Finally, to confirm the index, we carried out the steady flow rig test for intake port of test engine varying valve lift on the test matrix.

• Transactions of the Korean Society of Automotive Engineers
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• v.14 no.3
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• pp.178-185
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• 2006

This paper investigates the steady-state combustion characteristics of the Homogeneous charge compression ignition(HCCI) engine with variable valve timing(VVT) and dimethyl ether(DME) direct injection, to find out its benefits in exhaust gas emissions. HCCI combustion is an attractive way to lower carbon dioxide($CO_2$), nitrogen oxides(NOx) emission and to allow higher fuel conversion efficiency. However, HCCI engine has inherent problem of narrow operating range at high load due to high in-cylinder peak pressure and consequent noise. To overcome this problem, the control of combustion start and heat release rate is required. It is difficult to control the start of combustion because HCCI combustion phase is closely linked to chemical reaction during a compression stroke. The combination of VVT and DME direct injection was chosen as the most promising strategy to control the HCCI combustion phase in this study. Regular gasoline was injected at intake port as main fuel, while small amount of DME was also injected directly into the cylinder as an ignition promoter for the control of ignition timing. Different intake valve timings were tested for combustion phase control. Regular gasoline was tested for HCCI operation and emission characteristics with various engine conditions. With HCCI operation, ignition delay and rapid burning angle were successfully controlled by the amount of internal EGR that was determined with VVT. For best IMEP and low HC emission, DME should be injected during early compression stroke. IMEP was mainly affected by the DME injection timing, and quantities of fuel DME and gasoline. HC emission was mainly affected by both the amount of gasoline and the DME injection timing. NOx emission was lower than conventional SI engine at gasoline lean region. However, NOx emission was similar to that in the conventional SI engine at gasoline rich region. CO emission was affected by the amount of gasoline and DME.

• Transactions of the Korean Society of Automotive Engineers
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• v.15 no.3
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• pp.54-62
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• 2007

The knock characteristics in an engine were investigated under homogeneous charge compression ignition (HCCI) operation. Liquefied petroleum gas (LPG)and gasoline were used as fuels and injected at the intake port using port fuel injection equipment. Di-methyl ether (DME) was used as an ignition promoter and was injected directly into the cylinder near compression top dead center (TDC). A commercial variable valve timing device was used to control the volumetric efficiency and the amount of internal residual gas. Different intake valve timingsand fuel injection amounts were tested to verify the knock characteristics of the HCCI engine. The ringing intensity (RI) was used to define the intensity of knock according to the operating conditions. The RI of the LPG HCCI engine was lower than that of the gasoline HCCI engine at every experimental condition. The indicated mean effective pressure (IMEP) dropped when the RI was over 0.5 MW/m2and the maximum combustion pressure was over 6.5MPa. There was no significant relationship between RI and fuel type. The RI can be predicted by the crank angle degree (CAD) at 50 CA. Carbon monoxide (CO) and hydrocarbon (HC) emissions were minimized at high RI conditions. The shortest burn duration under low RI was effective in achieving low HC and CO emissions.

• Transactions of the Korean Society of Automotive Engineers
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• v.19 no.3
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• pp.23-28
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• 2011

To secure basic data for intake port design, effects of a port masking on the part load performance were investigated in a 4 valve SI engine. For this purpose, 9 kinds of masking, which have different shapes and masking ratio, are applied to the engine intake system. The characteristics of the performance were estimated through mixture response test at various engine load and speed. The results show that NOx emission, one of indexes for stratification, increases considerably in spite of retarded spark timing due to the stratification which is caused by unequal flow distribution between the two intake ports. The mechanism of stratification by masking is different from axial stratification and the fuel entering through masked port plays a very important role in this stratification process. In conclusion, the port masking method could be easily applied to engine intake system and be very effective for inducing the stratified charging without the change of port design.

• Journal of Chest Surgery
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• v.18 no.4
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• pp.692-699
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• 1985

Fifty cases of Open Heart Surgery due to congenital and acquired heart disease were done using the cardiopulmonary bypass in the Department of Thoracic and Cardiovascular surgery, Chosun University Hospital from November, 1980 to June, 1985. 1. The age of the congenital heart disease was from 7 to 29 years, the mean age was 14.5 years. In the acquired heart disease, the age was from 14 to 48 years, and the mean age was 22.3 years. The ratio of male to female was about 1.8:1. 2. The number of congenital cyanotic heart disease were 7 patients, congenital acyanotic heart disease were 17 patients and acquired valvular heart disease were 26 patients. All of the acquired heart disease was one or more valve disease. 3. Preoperative symptoms of the congenital heart disease were exertional dyspnea [cyanotic 100%, acyanotic 70.6%] and palpitation [cyanotic 28.6%, acyanotic 76.1%], and the acquired heart diseases were exertional dyspnea [92.3%], palpitation [34.1 %], and chest discomfort [30.8%]. 4. The method of the myocardial protection during the cardiopulmonary bypass were mild or moderate hypothermia, intermittent coronary perfusion of the cardioplegic solution, topical myocardial hypothermia with 4oC Hartmann`s solution. 5. In the cases of the valve replacement, postoperative oral anticoagulant therapy was started at oral intake of food using the warfarin and persantin, and the prothrombin time was maintained 30-50% of control value during 3-6 months for tissue valve replacement and permanently for metal valve replacement. 6. The postoperative complications were appeared in 24 cases and the complications were wound infection, occipital alopecia, hemorrhage etc. 7. The mortality after open heart surgery was 8 percents and the cause of death was low cardiac output syndrome, right heart failure, DIC, and Left ventricle rupture.

• Transactions of the Korean hydrogen and new energy society
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• v.8 no.3
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• pp.111-119
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• 1997

In this study, feasibility of expansion of BFL equivalence ratio are examined with change of injection location of hydrogen gas in intake pipe, coolant temperature, spark timing and amount of residual gas. As the results, BFL equivalence ratio is increased when injection location has some distance from intake valve. And it is decreased in accordance with increasing of coolant temperature and advance of spark timing. The amount of residual gas has little effect on BFL equivalence ratio.

• Transactions of the Korean Society of Automotive Engineers
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• v.22 no.3
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• pp.81-89
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• 2014

This study researched on the effect of HP/LP-EGR system to improve fuel consumption of Low Temperature Combustion Engine. Firstly, low temperature combustion engine with HP/LP-EGR system was established using 6.0L wastegate turbocharger HDDI engine. And suppliable EGR rate of the engine was proven to be enough to realize stable low temperature combustion. Then, optimum operating strategy was founded to develop fuel consumption of the engine. Control parameters were HP/LP-EGR valve and IPCV(Intake Pressure Control Valve) duty. Experiments method was that characteristics of the engine were measured and analyzed according to HP/LP-EGR strategies while EGR rate was fixed. Operating range for the strategy were divided into three parts, low load for low temperature combustion, high load for conventional diesel combustion, and transient condition. Finally, with the above strategy of this study, BSFC of the engine was improved about 2% compared to the base engine, and emission level, NOx and PM, met Tier4Final emission regulation.