• Journal of Energy Engineering
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• v.14 no.3 s.43
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• pp.180-186
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• 2005

As an engine has a wide range of RPM $(3000\~12000\;RPM)$, variable control system is necessary in order to increase engine performance. SCV has been frequently referred to as a possible way to increase engine performance at low RPM. The purpose of this study is to investigate on the influence of SCV, specially at the range of lower revolution, in a high-speed small engine. Experiments were conducted on 4 Valves SOHC/air-cooling single cylinder engine and SCV shapes have been tested fur swirl intensity, the performance of power, fuel consumption and emission. As a result, we find to use SCV range be below 5000 RPM which fuel consumption decreased $9\%$.

• 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.

• Journal of Advanced Marine Engineering and Technology
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• v.25 no.1
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• pp.115-123
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• 2001

This study describes the combustion characteristics under various condition of air excess ratio and ignition timing in a 2-valve gasoline optically accessible engine with swirl control valve(SCV). It adapted three different types of SCA(open ration 72.5%, 78%, 89%) to strengthen a swirl flow. Pressure data were acquired using pressure sensor to investigate the effect of swirl flow on combustion, and from these pressure data, IMEP(indicated mean effective pressure) and MFB(mass fraction burnt)were calculated to explain burn rate and flame speed. From acquired flame images, inspected the flame propagation direction, flame area, and flame centroid, Flame propagation direction was shown different tendency between with/without SCV, and flame area with SCV was faster and larger than that of conventional engine. Finally, the representative flame image at each crank angle were acquired by PDF method to verify flame growth process. It is found that strengthened swirl flow is more beneficial for faster and stable combustion.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.25 no.12
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• pp.1692-1701
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• 2001

This study describes the combustion characteristics under various condition of air excess ratio and ignition timing in a 2-valve SI optically accessible engine with swirl control valve(SCV). It adapted three different types of SCV(open ratio 72.5%, 78%, 59%) to strengthen a swirl flow. Pressure data were acquired using pressure sensor to investigate the effect of swirl flow on combustion, and from these pressure data, IMEP(indicated mean effective pressure) and MFB(mass fraction burnt) were calculated to explain burn rate and flame speed. From acquired flame images, we inspected the flame propagation direction, flame area, and flame centroid. Flame propagation direction showed different tendency between with/without SCV, and flame area with SCV was faster and larger than that of conventional engine. Finally, the representative flame images at each crank angle were acquired by PDF method to verify flame growth process. It is found that strengthened swirl flow is more beneficial for faster and stable combustion.

• Transactions of the Korean Society of Automotive Engineers
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• v.14 no.1
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• pp.129-137
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• 2006

This paper studies the effects of the swirl for the variation of intake port configuration that is key parameters in the flow field of direct injection diesel engines. In-cylinder flow characteristics is known to have significant effects on air-fuel mixing, combustion, and emissions. To investigate the effects of the swirl flow, various rpm(250, 500, 750) and two different intake port were used. And to evaluate the swirl motion in the flow field visualization engine, steady state flow test was conducted. Helical port intake port and SCV(Swirl Control Valve) were selected as the design parameters to increase the swirl flow and parametric study was performed. In the case of non-SCV, intake flow rate and non-dimensional swirl ratio were higher than those of SCV for the swirl head type. So, we could strengthen the swirl in the flow field with the swirl head type and don't using SCV. From the results of steady state flow test, non-swirl head type has the most good advantage for intake flow rate, and also the flow rate could be increased by using the SCV slightly. The effects of the type of engine head on intake air flow capability are dominant with respect to the existence of the SCV. We could measure the qualitative grade of swirl by capturing the scattering signal of microballoon from ICCD camera in the visualization diesel engine.

• Journal of Mechanical Science and Technology
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• v.19 no.2
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• pp.704-715
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• 2005

In this study, to investigate in-cylinder tumble or swirl intake flow of a gasoline engine, the flow characteristics were examined with opening control valve (OCV) and several swirl control valves (SCV) which intensify intake flow through steady flow experiment, and also turbulent characteristics of in-cylinder flow field were investigated by 2-frame cross-correlation particle image velocimetry (PIV) method. In the investigation of intake turbulent characteristics using PIV method, the different flow characteristics were showed according to OCV or SCV figures. The OCV or SCV installed engine had higher vorticity and turbulent kinetic energy than a baseline engine, especially around the wall and lower part of the cylinder. Above all, SCV B type was superior to the others. About energy dissipation and reynolds shear stress distribution, a baseline engine had larger loss than OCV or SCV installed one because flow impinged on the cylinder wall. It should be concluded, from what has been said above, as swirl component was added to existing tumble flow adequately, it was confirmed that turbulent intensity was enlarged, flow energy was conserved effectively through the experiment. In other words, there is a suggestion that flow characteristics as these affected to in-cylinder combustion positively.

• Advances in pediatric surgery
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• v.4 no.1
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• pp.1-15
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• 1998

To evaluate the effectiveness of central venous catheters(CVCs) in children, 320 CVCs placed in 255 neonate and children over a 10-year period were analyzed retrospectively. CVC was placed by one pediatric surgeon for a total of 6, 116 patients days. Catheters were placed preoperatively for TPN or chemo in 223 cases. CVC was solely for TPN in 57 cases and for chemotherapy in 40. Local anesthesia was utilized in 71 cases, and the general anesthesia was administered in the remainder of the patients. The subclavian vein was catheterized(SCV) in 202 cases(82 infants and neonates), tunneled external jugular venotomy(EJV) was utilized in 38, tunneled internal jugular venotomy(UV) in 2, the facial venotomy(FV) was used in 3, and the umbilical vein was catheterized UVC) with vein transposition in 74 infants. In neonates, 72 UVCs were placed during laparotomy. SCV was increased with ages, from 3 kg of minimal body weight. The average catheter-periods over-all were 19.1 days, SCV 17 days, EJV 40, IJV 60 and UVC 14. Technical complications were; arterial puncture(6), puncture failure(5) and abnormal location(12) in SCV; insertion failure(3) in EJV; abnormal location in the portal vein(4) and the liver parenchyma(2) cystic fluid accumulations in UVC. Twelve migrations(3.8 %) out of position occurred; SCV(2), EJV(1) and UVC(9). There were 4 cases(1.2 %) of catheter obstruction and 11(3.4 %) of catheter infection(3 SCV, 2 EJV and 6 UVC). Rescue procedures were utilized with some success. There was one mortality(0.3 %) due to deep sedation in a 1.06 kg baby during placement of an EJV. The surgeon's experience, proper catheter selection and following safety rules are the most important factors for successful CVCs.

• Journal of Preventive Medicine and Public Health
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• v.32 no.1
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• pp.80-87
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• 1999

Objectives. The Study of Small Area Variation(SAV) is most interesting issue in the health care researches. Most studies of SAV have been concluded the existences of variation on the basis of the magnitude of variation without statistical testing. But it is difficult to explain the existence of variation with this way because variation indicies are easily influenced by several parameters and also their distribution are skewed. So, it needs for the study to investigate the distribution of these indices and develop the statistical testing model. Methods. This study was planned to analyze on the distribution of variation indices such as Extremal Quotient(EQ), Coefficient of Variation(CV), Systematic Component of Variation(SCV) and compare the statistical power among indicies. The simulations was performed on the basis of several assumptions and compared to the empirical data. Results. Main findings can be summarized as follows. 1. If other conditions are constant, the more number of regions, the larger 95 percentile of EQ. But under same situation, 95 percentile of CV and SCV were slightly decreased. 2. If the size of regional population or utilization rate were increased, 95 percentile of all statistics were decreased. Also in the cases of small population size and low utilization rate, 95 percentiles of EQ showed various change contrast to the little change of CV. 3. If the difference at the size of regional population were increased, 95 percentiles of EQ and SCV were increased contrast to the little different of CV. 4. If the utilization rate were increased, 95 percentiles of all indicies were increased. But under the same difference of utilization rate, the power of CV and SCV were increased comparing to no change of the power of EQ. 5. Usually the power of EQ were lower than that of CV or SCV and it is similar between CV and SCV. Conclusions. Therefore, we suggest that in selecting the variation indicies at the SAV, CV or SCV are superior than EQ in terms of significance level and power.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.24 no.2
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• pp.161-168
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• 2000

Lean combustion in a SI engine is one of the best solution for the improvement of fuel economy and reduction of pollutant emission. In order to access a lean combustion engine, stable combustion at lean AlF ratio is needed. In this paper, the effect of fuel injection timing on lean misfire limit has been investigated in an MPI engine. To investigate the interaction of injection timing and intake flow characteristics, three different swirl generating SCV(swirl control valve) configurations were considered, and investigated their effects on lean misfire limit and torque at full load operation. Also the effects of spark timing on lean combustion has been investigated. Lean combustion has been examined and the results are reported in this paper. SCV B has been developed to satisfy the requirements of sufficient swirl generation to improve lean combustion and stable performance. It is found that injection timing, spark timing and intake air motion govern the stable lean combustion.

• International Journal of Automotive Technology
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• v.6 no.5
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• pp.453-460
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• 2005

The tumble or swirl flow is used to promote mixing of air and fuel in the cylinder and to enlarge turbulent intensity in the end of the compression stroke. Since the in-cylinder flow is a kind of transient state with rapid flow variation, which is non-steady state flow, the tumble or swirl flow has not been analyzed sufficiently whether they are applicable to combustion theoretically. In the investigation of intake turbulent characteristics using PIV method, typical flow characteristics were figured out by SCV configurations. An engine installed SCV had higher vorticity and turbulent strength by fluctuation and turbulent kinetic energy than a baseline engine, especially near the cylinder wall and lower part of the cylinder. Above all, the engine with SCV 8 was superior to the others in aspect of vorticity and turbulent strength. For energy dissipation, a baseline engine had much higher energy loss than the engine installed SCV because flow impinged on the cylinder wall. Consequently, as swirl flow was added to existing tumble flow, it was found that fluctuation increased and flow energy was conserved effectively through the experiment.