• Transactions of the Korean hydrogen and new energy society
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• v.20 no.4
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• pp.344-351
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• 2009

A multi-zone model was used to predict the operating range of homogeneous charge compression ignition (HCCI) engine, the boundaries of the operating range were determined by knock (presented by ring intensity), misfire (presented by sensitivity of indicated mean effective pressure to the initial temperature). A HCCI engine fueled with Di-Methyl Ether (DME) was simulated under different initial temperature and equivalence ratios, and the operating range was well produced by the model. Furthermore, the model was applied to develop the operating range for thermal stratification in the preceding condition of initial temperature and equivalence ratios. The computations were conducted using Senkin application of the CHEMKINII kinetics rate code.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.20 no.10
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• pp.3251-3261
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• 1996

Flows were measured in an unshrouded centrifugal impeller. By using a single slanted hot-wire probe and a Kiel probe mounted on the impeller hub disk, the 3-D relative velocities and the rotary stagnation pressures were measured in seven circumferential planes between the inlet and outlet of the impeller rotating at 700 rpm, which diameter is 0.39 meter, and the static pressures and the slip factor at the impeller outlet were estimated from the measured values. Measurements were made for three flow rates corresponding to zero incidence and two others with the greater and the smaller one than zero. From the measured data in these flow rates, the followings were investigated in the impeller passage, the variation of the primary and secondary flows, the leakage flows, the wake's position and its size, the static pressure rise and the loss production mechanism. Furthermore the static pressure and the slip factor were compared with the results of inviscid Quasi-3D calculation.

• Transactions of the Korean Society of Automotive Engineers
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• v.18 no.4
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• pp.132-139
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• 2010

This paper describes an investigation of the performance and emission characteristics of a commercial cylinder direct injection diesel engine operating on natural gas with pilot diesel ignition. Engine tests for variations in the pilot injection timing were performed at an engine speed of 1500 rpm. This study showed that the performance of the dual-fuel diesel engine increased as the engine load increased and as the pilot diesel injection timing angle advanced. The peaks of cylinder pressure, pressure rise rate, and heat release rate all increased while the fuel ignition timing advanced with the pilot injection timing. The engine operation was stable, and the least smoke was produced at a pilot injection timing of $12^{\circ}$ before top dead center. NOx emissions were only exhausted under high-load conditions, and they increased as the pilot injection timing angle advanced.

• Journal of the Korean Society for Precision Engineering
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• v.11 no.1
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• pp.123-128
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• 1994

A high speed spindle system for machine tools can be used to reduce the machining time, to improve the machining accuracy, to perform the machining of light metals and hard materials, and to unite the cutting and grinding processes. In this study, a high speed spindle system is developed by applying the oil-air lubrication method, angular contact ball bearings, injection nozzles with dual orifices, cooling jacket and so on. And an air cooling experiment for evaluating the performance of the spindle system is carried out. Especially, in ofder to establish the air cooling conditions related to the development of a high speed spindle system, the effects of cooling air pressure, oil supply rate, air supply rate and rotational spindle speed are studied and discussed on the bearing temperature rise and frictional torque. Also the effects of cooling air pressure, rotational spindle speed and spindle system structure is investigated on the bearing temperature distribution. The experiment on the test model reveals the usefulness of the air cooling method.

• Journal of Veterinary Clinics
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• v.28 no.1
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• pp.40-45
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• 2011

Cardiovascular changes caused by $CO_2$ pneumoperitoneum during laparoscopic ovariohysterectomy (LOVH) were measured in nine healthy mixed breed dogs ($16.7{\pm}4.6kg$). The dogs were premedicated with the combination of atropine, acepromazine, and butorphanol. General anesthesia was induced with propofol and maintained with isoflurane in oxygen. Controlled ventilation maintained partial pressure of end-tidal $CO_2$ between 35-45 mmHg. The $CO_2$ pneumoperitoneum was maintained at a constant pressure of 12 mmHg and the dog was placed in the $15^{\circ}$ Trendelenburg position as LOVH was performed. Dorsal pedal artery was catheterized for measurements of heart rate (HR) and invasive arterial blood pressure (IBP). Prior to the intraperitoneal insufflation, baseline measurements of HR and IBP were made every minute for a total of 10 min. Then, measurements of HR and IBP were made every 5 min following intraperitoneal insufflation and were also made every 5 min following desufflation for a total of 10 min. The $CO_2$ pneumoperitoneum during LOVH resulted in a significant (P < 0.05) increase in systolic arterial blood pressure at the time of the onset of insufflation. In addition, diastolic and mean arterial blood pressure increased significantly (P < 0.05) at the time of the onset of insufflation and 5 min following insufflation. The mean heart rate did not change significantly during LOVH. Although IBP showed sharp initial rise following the $CO_2$ pneumoperitoneum, the changes were within physiological acceptable limits in these healthy, ventilated dogs.

• Proceedings of the KSME Conference
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• 2001.06e
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• pp.678-683
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• 2001

The present work has carried out experimental study on a cross-flow fan system with a simplified vortex wall scroll casing. A cross-flow fan test rig was constructed to obtain pressure rise and volume flow rate for various fan operating conditions. The performance estimation is using a wind tunnel with a motor driven damper for flow rate control and flows are quantitatively visualized by light scattering system with a pulsed laser. Min focus on the visualization is finding a eccentric vortex inside a fan which is a major factor reducing fan efficiency. Comprehensive engineering data are prepared for industrial applications and show a good agreement with a prior work by experimental measurements.

• Proceedings of the KSME Conference
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• 2003.11a
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• pp.840-844
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• 2003

A study for increase of fan flow rate by geometric modification has been conducted to decrease temperature rise of marine generator inner part. Through experiment of a real product, a performance curve for various flow resistances was obtained. Flow analyses for each cases were done by using commercial code-FLUENT and the results were very similar to experimental data (0.7% deviation at normal operating condition). Through flow analysis results for various design geometric modification, a scroll type fan was adopted as a best design geometry with 100Pa more pressure and 22% more flow rate than original fan.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.25 no.3
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• pp.373-380
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• 2001

In this study, a single Taylor bubble and a train of Taylor bubbles rising in a vertical tube were simulated numerically. A finite difference method was used to solve the mass and momentum equations for the liquid-gas region. The liquid-gas interface was captured by a level set function which is defined a signed distance from the interface. For a train of Taylor bubbles repeated periodically in space, the periodic conditions were imposed at the boundaries normal to the gravitational direction and the pressure boundary conditions were iteratively determined so that the computed flow rate should be equal to a given flow rate. Based on the numerical simulation, the calculated shape and rise velocity of a Taylor bubble were found to be in good agreement with the experimental data reported in the literature.

• Korean Chemical Engineering Research
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• v.61 no.1
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• pp.80-88
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• 2023

Ensuring safety in the designing of manufacturing and handling facilities for low-density polyethylene (LDPE) is difficult because there are no standards for the dust explosion characteristics of LDPE. In this study, a dust explosion test was performed on two dust samples collected from a bag filter (LDPE 1) during the LDPE manufacturing process and sedimentary dust (LDPE 2) leaked outside a facility such as a silo, and the LDPE 2 explosion test results were summarized. Particle size analysis showed that the volume-based particle diameter (median) was 95.04 ㎛ and the number density was 0-1 ㎛. The maximum explosion pressure (P_max) was 6.6 bar, and the maximum rate of explosion pressure rise was 366 [bar/s] at 1500 g/m³. Accordingly, the dust explosion index (K_st) was 99.4 bar·m/s, which was confirmed as ST-1 grade. Moreover, the minimum ignition energy and minimum ignition temperature was 10 mJ and 450 ℃, respectively. Currently, manufacturing and handling design is based on the characteristic values of high-density polyethylene (HDPE). However, as the test results show that LDPE 2 dust has a higher risk than HDPE (particle diameter 61.6 ㎛), caution is required when using the HDPE design criteria in the LDPE manufacturing process.

• Journal of the Korea Institute of Building Construction
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• v.15 no.3
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• pp.291-297
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• 2015

In this study, the evaluation and the analysis of the correlation between rheological properties and pumpability of high performance concrete, C80A which was applied to the height of from 200 m to 350 m in a super tall building, was carried out by measuring pumping pressure and flow rate, testing concrete properties at before and after pumping. As the results, C80A had satisfactory properties of fresh and hardened concrete to the requirements even after pumping and the maximum pumping pressure showed increase of 10~15% at every 50m higher pumping and the average flow rate showed the above $25m^3$ per hour which means proper productivity. Additionally it was verified that pumping pressure and friction factor in pipeline are inversely proportional to slump flow and showed a tendency to increase according to the higher T-500 value.