• Journal of the Korean Society of Propulsion Engineers
• /
• v.23 no.5
• /
• pp.1-9
• /
• 2019

Infrared signal and exhaust gas temperature distribution with bypass ratio were measured using a micro turbojet engine. Micro turbojet engine was modified to simulate the turbofan engine behaviour. Core flow was simulated using the jet flow of the micro turbojet engine, and high-pressure air was supplied to its external duct to simulate bypass flow. The effects of bypass ratios (0.5, 1.0, and 1.4) were examined. The experimental results indicate that the infrared signal decreases as the bypass ratio increases. And also gas temperature decreases with bypass ratios. Additionally, Schlieren visualization of the exhaust gas plume was conducted. From the exhaust gas temperature distribution and Schlieren images, the structure of jet plume with various bypass ratios was understood.

• Journal of Energy Engineering
• /
• v.11 no.2
• /
• pp.130-135
• /
• 2002

Bypass air conditioning systems are divided into three types; outdoor air bypass, mixed air bypass and return air bypass system. Among bypass air conditioning systems, a return air bypass system is more effective than other two systems because it doesn't induce unconditioned outdoor air into conditioned room. The numerical study on the bypass air conditioning system shows this system can maintain indoor RH(Relative Humidity) less than a conventional CAV (Constant Air Volume) air conditioning system by adjusting face and bypass dampers at part load. A simulator was built to compare results of a numerical experiment and those of a simulator experiment. The results of the simulator experiment was nearly same as those of the numerical experiment; when a design sensible load (the ratio of sensible load to total sensible load) was 70 percent (at this time, RSHF=0.7), indoor relative humidity (in case of both numerical experiments and simulator experiments) was maintained below 60% specified by ASHRAE STANDARD 62-1999. The bypass air conditioning system is expected to be applied to many buildings where the Percentage of latent loads or air change tate is high.

• 기계와재료
• /
• v.22 no.1
• /
• pp.54-64
• /
• 2010

공작기계의 고속화, 다축화, 복잡화에 따른 열변형 오차가 공작기계에서 발생하는 오차의 대부분을 차지하고 있다. 이러한 열변형 오차를 최소화 하기 위해 공작기계의 발열부에 차가운 오일을 공급하여 냉각함으로써, 열변형을 제거하는 장치가 오일쿨러이다. 오일쿨러는 제어 방법에 따라 On-off, 가스 바이패스, 인버터 방식 등이 사용된다. 초정밀 공작기계에는 주로 가스 바이패스 및 인버터 방식이 사용되는데, 인버터 방식의 경우 고가(高價)인 관계로 주로 옵션 형태로 사용된다. 가스 바이패스 방식 오일쿨러는 인버터 방식에 비해 가격이 저렴하고 구조가 간다하며 정밀한 온도제어를 할 수 있지만 부하가 낮은 경우 구조적인 한계로 인해 온도제어 불안정을 발생시킨다. 본 연구에서는 기존 바이패스 방식 오일쿨러에서 나타나는 문제점을 해결하고 보다 정밀한 온도제어를 위해 2개의 전자밸브를 갖는 듀얼 밸브 방식 오일쿨러 시스템을 개발하였다. 개발된 듀얼 밸브 오일쿨러 시스템의 성능검증을 위해 정격운전, DIN 8602 규격, ISO/DIS 230-3 운전모드에서 성능을 비교/분석하였다.

• Journal of Chest Surgery
• /
• v.31 no.9
• /
• pp.877-883
• /
• 1998

Background: Cardiopulmonary bypass(CPB), a standard adjunct for open heart surgery, can also play an important role in treating patients with noncardiac diseases. Material and Method: We report a collective analysis of noncardiac applications of cardiopulmonary bypass experienced at Seoul National University Hospital from 1969 to 1996. Out of a total of 20 patients, 8 were treated for membranous obstruction of inferior vena cava(MOVC), 5 for malignant melanoma, 3 for pulmonary embolism, 1 for double lung transplantation, 1 for intracranial giant aneurysm(GA), 1 for renal cell carcinoma(RC), and 1 for liposarcoma. CPB was used to induce profound hypothermia with circulatory arrest in 6 patients(MOVC 4, GA 1, RC 1). Result: CPB time was 113 mins on average for MOVC, 161 mins for GA, and 156 mins for RC, while the lowest rectal temperature was 26$^{\circ}C$ on average in MOVC, and 19$^{\circ}C$ in GA and RC. Postoperative recovery was good in all MOVC patients. The patient with GA, who underwent reoperation for the removal of hematoma, died 14 days postoperatively. The patient with RC recovered from the operation in a good condition but died from metastatic spread 6 months later. CPB was instituted for pulmonary embolectomy in 3 patients, in whom postoperative courses were uneventful, except in 1 patient who showed transient neurologic symptoms. CPB was used in a patient with double-lung transplantation for hemodynamic and ventilatory support. The patient was weaned successfully from CPB but died from low output and septicemia 19 days postoperatively. CPB without circulatory arrest was used to treat in 4 patients with MOVC. These patients showed good postoperative courses. CPB was used to administer high concentrations of chemotherapeutic agents to the extremities in 6 patients(malignant melanoma 5, recurrent liposarcoma 1). CPB time was 153 mins on average. No complications such as edema and neurologic disability were found. Conclusion: Although CPB has a limited indication in noncardiac diseases, if properly applied, it can be a very useful adjunct in a variety of surgical cases.

• Solar Energy
• /
• v.18 no.2
• /
• pp.91-104
• /
• 1998

This study carried out a numerical analysis on a heat pump assisted dryer using HFC134a. Under the constant degree of superheat and that of subcooling, we analyzed the performance of heat pump assisted dryer with varying an air mass velocity, bypass air ratio, compressor speed and an inlet bulb temperature of dryer. Simulation results were compared with experimental results, so they were maximally agreed in the range of 10%. There was the proper bypass air ratio with varying an air mass velocity. As for the effect of SMER having the inlet temperature $35^{\circ}C$ and compressor speed 1360rpm, bypass air ratio was 30% at the front velocity 0.5kg/s, 40% at the front velocity 0.7kg/s and 50% at the front velocity 0.9kg/s and 1.1kg/s. As the compressor speed was increased, SMER decreased and COP increased. As the inlet bulb temperature was increased, SMER and COP decreased.

• Resources Recycling
• /
• v.32 no.6
• /
• pp.18-24
• /
• 2023

This study undertook initial investigations into the carbonation of chlorine bypass dust, aiming to apply it as a raw material for cement and as an admixture for concrete. Various experimental methods, including XRD(X-ray diffraction), XRF(X-ray fluorescence), and particle size distribution analyses, were employed to verify the physical and chemical properties of chlorine bypass dust, with and without water washing. The mineral carbonation extent of chlorine bypass dust was examined by considering the dust type, stirring temperature, and experiment duration. Notably, a higher degree of mineral carbonation was observed in water-washed bypass dust than its non-water-washed counterpart, indicating an elevated calcium content in the former. Furthermore, an augmented stirring temperature positively impacted the initial stages of mineral carbonation. However, divergent outcomes were observed over time, contingent upon the specific characteristics of dust types under consideration.

• Journal of Chest Surgery
• /
• v.31 no.9
• /
• pp.867-872
• /
• 1998

Background: The fixed dose regimen with activated coagulation time(ACT) is the most commonly employed method for determining the required dosage of heparin and protamine during cardiopulmonary bypass(CPB). Material and Method: We performed a prospective study on a fixed dose regimen for analyzing adequate dosages of heparin and protamine, the incidence of heparin resistance and heparin-induced thrombocyt openia, factors affecting ACT during CPB, and changes of ACT during aprotinin usage. 300 units/kg of heparin were administered to patients, and ACTs were measured after 5 mins. ACTs were checked at 10 mins and 30 mins after the onset of CPB, and then at 30 min intervals thereafter. If the measured ACT was under 400 secs, we added 100 units/kg of heparin. The heparin was reversed with 1 mg of protamine for each 100 units administered. If the measured ACT was longer than 130 secs 30 mins after protamine administration or if there was definitive evidence of a coagulation defect, we administered a further 0.5 mg/kg of protamine. Result: We studied 80 patients(50 adults and 30 children) who underwent open heart surgery(OHS) at Seoul National University Hospital. Preoperative ACT was 114.3${\pm}$19.3 secs in adults, and 119.5${\pm}$18.2 secs in children. There were no differences in preoperative ACT due to age, body weight, body surface area, or sex. The preoperative ACT was not influenced by a positive past history of OHS. Ten adults(20%) and 3 pediatric patients(10%) needed additional doses of heparin to maintain the ACT above 400 secs. Additional protamine administration was needed in 9 adults(18%) and 10 children(33%). Heparin resistance was found in only two adults. Heparin-induced thrombocytopenia was detected in 2 adults and 1 child. During CPB, ACT was prolonged. 12 adult patients received a low dose of aprotinin and showed longer celite activated ACT compared to the control group.The kaolin activated ACT showed a lower tendency than the celite activated ACT in aprotinin users. Conclusion: In conclusion, fixed dose regimen of heparin and protamine can be used without significant problems, but the incidence of need of additional dosage remains unsatisfactory.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.27 no.8
• /
• pp.1251-1258
• /
• 2003

This paper presents a nonlinear robust approach to the slip control problem for a torque converter bypass clutch in a passenger car. The proposed nonlinear robust controller builds upon only the measurements avail-able from inexpensive sensors that are already installed in passenger cars for control. The issue of torque estimation problems for the implementation of the proposed controller is addressed. The stability of the internal dynamics is investigated, upon which a nonlinear robust controller is designed using input-output feedback linearization and Lyapunov redesign technique. The performance of the designed controller is validated by simulation studies.

• Journal of the Korean Society of Propulsion Engineers
• /
• v.24 no.5
• /
• pp.34-42
• /
• 2020

In modern air combat, infrared signals play an important role in the detection of opponents and must be reduced to improve survivability and stealth. In particular, IR signals generated in the wake of aircraft engines have high intensity and short wavelengths, so most heat-tracking missiles detect these signals. Accordingly, the measurement and characteristic analysis of Gas radiation signals from the engine's wake were carried out in this study. Micro turbojet engine has been configured to simulate a real aircraft turbofan engine, and the characteristics of IR signal reduction by adjusting the bypass ratio were identified. Through this, the IR signal characteristics for each wavelength are analyzed and verification of signal reduction technologies is performed.

• Resources Recycling
• /
• v.26 no.2
• /
• pp.11-17
• /
• 2017

Many problems are occurred by using industrial by-product and municipal solid waste in the cement manufacturing process. The main components of chlorine by-pass dust generated by the use of the wastes are $K^+$, $Cl^-$, and a slight amount of heavy metals is also contained. In terms of waste recycling, it is necessary to eliminate the heavy metals. Therefore, in this study, the experiments for the removal of heavy metals from KCl which was produced by chlorine by-pass dust were conducted. In order to find optimum conditions for the removal of heavy metals, we have controlled the amount of water and precipitator. The type and concentration of heavy metals in KCl were analyzed. The concentration of heavy metals decreased as amount of precipitator increased. The heavy metals such as Pb, Cd, and As were not detected in dust A and B, when the mixing ratios between dust A(B) and water were controlled to be 1:2 (1:2, 1:3.5) with the addition of 3% precipitator (NaOCl).