• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.22 no.6
• /
• pp.460-468
• /
• 2021

This study investigated the enhanced combustion efficiency of an "air-cooled combustion system" with single F.D. fan, and performed a numerical analysis for the operation and design conditions to increase the combustion efficiency. The combustion efficiency in an actual combustor was compared before and after the structure modification. Numerical analysis for application of a single fan revealed the difficulty of forming a turbulence for circular combustion conditions. This is because the supply ratio of combustion air supplied into 2 flow paths becomes irregular in the combustion furnace due to a change in friction force and pressure in each flow path. Subsequently, two methods of supplying air into the combustion furnace were analyzed numerically to obtain the optimal combustion conditions of an air-cooled combustion system. The first method involved injecting the preheated combustion air after a 180~360 degree rotation from the outer wall, whereas in the second method, the combustion air was injected into the combustion furnace in a tangential direction after primary heat exchange outside the combustion furnace, by applying a rotatable vane structure in the combustion furnace. Results reveal that application of a single F.D. fan to the air injection into a rotatable combustion furnace is desirable for optimization of the combustion conditions for applying a duct structure having a dual cooling wall for the cooling of the outer wall of the combustion furnace, and for maintaining perfect mixing in the combustion furnace. We therefore confirmed enhanced combustion efficiency by comparing the actual combustion efficiency before and after structure modification.

• Transactions of the Korean hydrogen and new energy society
• /
• v.5 no.2
• /
• pp.91-98
• /
• 1994

In this study hydrogen gas and oxygen gas are used to make a pollution-free engine which is a closed system with the components such as a combustor, two turbines, a radiator and a compressor. One of the two turbines produces main power, and the other is used to drive a compressor to compress unburned gases and to return them to the combustor. Some of the water from the radiator is pumped to cool down the internal wall of the combustor and to be used as a working fluid which expands from liquid state to vapor state to get more expansion work. The possibility of operating the whole system is checked by the thermodynamic analysis to make the closed engine system. The calculations in the thermal analysis are based on the Brayton cycle and the Rankine cycle. The closed system in this study shows similar efficiency as usual internal combustion engines, but it produces water only without air pollution such as $NO_x$ and soot.

• Journal of the Korean Society of Visualization
• /
• v.15 no.3
• /
• pp.14-19
• /
• 2017

Increase of blood viscosity significantly changes the flow resistance and wall shear stress which are related with cardiovascular diseases. For measurement of blood viscosity, microfluidic method has proposed by monitoring pressure between sample and reference flows in the downstream of a microchannel with two inlets. However, it is difficult to apply this method to unknown flow conditions. To measure blood viscosity under unknown flow conditions, a microfluidic method based on micro particle image velocimetry(PIV) is proposed in this study. Flow rate in the microchannel was estimated by assuming velocity profiles represent mean value along channel depth. To demonstrate the measurement accuracy of flow rate, the flow rates measured at the upstream and downstream of a T-shaped microchannel were compared with injection flow rate. The present results indicate that blood viscosity could be reasonably estimated according to shear rate by measuring the interfacial width and flow rate of blood flow. This method would be useful for understanding the effects of hemorheological features on the cardiovascular diseases.

• Proceedings of the KSME Conference
• /
• 2001.06e
• /
• pp.542-547
• /
• 2001

A non-intrusive Planar Laser-Induced Fluorescence(PLIF) technique was applied to study the turbulent mixing process in a Rushton turbine reactor. Instantaneous and ensemble averaged concentration fields are obtained by measuring the fluorescence intensity of Rhodamine B tracer excited by a thin Nd:Yag laser sheet illuminating the whole center plane of the stirred tank. The gray level images captured by a 14-bit cooled CCD camera can be transformed to the local concentration values using a calibration matrix. The dye injection point was selected at the tank wall with three quarter height (3/4H) from the tank bottom to observe the mixing characteristics in upper bulk flow region. There exist distinct two time scales: the rapid decay of mean concentration in each region after the dye infusion reflects the large scale mixing while the followed slow decay reveals the small scale mixing. The temporal change of concentration probability functions conjectures the two sequential processes in the batch type mixing. An inactive column of water existed above the impeller disk, in which the fluid rotates with the shaft but is isolated from the mean bulk flow.

• Transactions of the Korean Society of Automotive Engineers
• /
• v.14 no.6
• /
• pp.1-8
• /
• 2006

One of the most important subjects to develop a LPDi engine is to suppress the bubble generated inside the liquid LPG direct injector. For the purpose of this, the analogy visualization injector to visualize the generation and behaviors of bubble is manufactured, and the bubbling phenomenon and behaviors of bubble are visualized and investigated according to the change of the temperature around an injector wall, fuel pressure and a needle configuration. As results, it was found that the bubble inside the injector is generated around an injector hole and after rising by buoyancy it disappears around the top of a nozzle. The number of bubbles generated is little changed regardless of the lapse of time but it remarkably increases as the temperature around the injector increases. Also, it was known that as the sac volume in LPDi injector decreases the generation of bubble is more active and the rising velocity of bubble generated is increased.

• Journal of Pharmacopuncture
• /
• v.9 no.1
• /
• pp.21-32
• /
• 2006

Purpose : Bee Venom Acupuncture(BVA) is known to affect inflammation and immune system. This study examined the macroscopic, hormonal and immunological effects of BVA on rats with surgically induced endometriosis. Methods : Endometrial tissue was implanted in the serosal wall of the small intestine in rats. The rats were divided randomly into an experimental and control group. The experimental group was treated with BVA injection on kwanwon(CV4) three times per week, and the control group was given an oral dose of normal saline every day. 6 weeks later, the size of the ectopic uterine tissue was estimated, and the serum progesterone, estradiol and cytokine($TNF-{\alpha}$, IL-2, IL-4, IL-6, IL-l0) concentrations were analyzed. Results : The size of the ectopic uterine implants in the experimental group was much smaller than that in the control group. The estradiol, IL-2 concentrations were significantly lower and the IL-6, IL-I0 concentrations were significantly higher in the serum of the experimental group than in the control group, there was no significant difference in the concentration of the other cytokine. Conclusion : These results suggest that BVA is an effective treatment for endometriosis.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.26 no.8
• /
• pp.1145-1152
• /
• 2002

A non-intrusive Planar Laser-Induced Fluorescence(PLIF) technique was applied to study the turbulent mixing process in a Rushton turbine reactor. Instantaneous and ensemble averaged concentration fields was obtained by measuring the fluorescence intensity of Rhodamine B tracer excited by a thin Nd:Yag laser sheet illuminating the whole center plane of the stirred tank. The gray level images captured by a 14-bit cooled CCD camera could be transformed to the local concentration values using a calibration matrix. The dye injection point was selected at the tank wall with three quarter. height (3/4H) from the tank bottom to observe the mixing characteristics in upper bulk flow region. There exist distinct two time scales: the rapid decay of mean concentration after the dye infusion reflects the large scale turbulent mixing while the fellowed slow decay reveals the small scale molecular mixing. The temporal change of concentration variance field conjectures the two sequential processes for the batch type mixing. An inactive column of water is existed above the impeller disk, in which the fluid rotates with the shaft but is isolated from the mean bulk flow.

• Journal of Korea Technical Association of The Pulp and Paper Industry
• /
• v.36 no.5 s.108
• /
• pp.1-10
• /
• 2004

The geometry of headboxes is of great importance in obtaining good formation, even basis weight profile and fiber orientation. Therefore, many attentions have been made to examine the influence of the geometry of headboxes on the flow behavior. In this study, to evaluate flow behavior in headboxes, three types of turbulence generators were examined using pilot headbox. Velocity profiles in MD and CD were measured using a pressure monitoring system and flow in headboxes was visualized by dye injection method. CD velocity profiles at three different locations inside the slice of Type A headbox showed that the velocity increased downstream to slice exit and had a pattern with four humps due to the persisting wall effect of step diffusors. Results from the evaluation of normalized velocity profile and flow visualization showed that L-shaped Type C headbox caused a large pressure drop but it lacked in flow stabilizing ability.

• Journal of Korean Neurosurgical Society
• /
• v.57 no.2
• /
• pp.135-139
• /
• 2015

Spinal neurenteric cysts are uncommon congenital lesions, furthermore solitary neurenteric cysts of the upper cervical spine are very rare. A 15-year-old boy having an intraspinal neurenteric cyst located at cervical spine presented with symptoms of neck pain and both shoulders pain for 2 months. Cervical spine magnetic resonance (MR) imaging demonstrated an intradural extramedullary cystic mass at the C1-3 level without enhancement after gadolinium injection. There was no associated malformation on the MR imaging, computed tomography, and radiography. Hemilaminectomy at the C1-3 levels was performed and the lesion was completely removed through a posterior approach. Histological examination showed the cystic wall lined with ciliated pseudostratified columnar epithelium containing mucinous contents. Neurenteric cyst should be considered in the diagnosis of spinal solitary cystic mass.

• The Korean Journal of Physiology and Pharmacology
• /
• v.14 no.6
• /
• pp.377-384
• /
• 2010

The present study examined whether metformin treatment prevents isoporterenol-induced cardiac hypertrophy in mice. Chronic subcutaneous infusion of isoproterenol (15 mg/kg/24 h) for 1 week using an osmotic minipump induced cardiac hypertrophy measured by the heart-to-body weight ratio and left ventricular posterior wall thickness. Cardiac hypertrophy was accompanied with increased interleukin-6 (IL-6), transforming growth factor (TGF)-${\beta}$, atrial natriuretic peptide (ANP), collagen I and III, and matrix metallopeptidase 2 (MMP-2). Coinfusion of metformin (150 mg/kg/24 h) with isoproterenol partially inhibited cardiac hypertrophy that was followed by reduced IL-6, TGF-${\beta}$, ANP, collagen I and III, and MMP-2. Chronic subcutaneous infusion of metformin did not increase AMP-activated protein kinase (AMPK) activity in heart, although acute intraperitoneal injection of metformin (10 mg/kg) increased AMPK activity. Isoproterenol increased nitrotyrosine levels and mRNA expression of antioxidant enzyme glutathione peroxidase and metformin treatment normalized these changes. These results suggest that metformin inhibits cardiac hypertrophy through attenuating oxidative stress.