• International Journal of Fluid Machinery and Systems
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• 제6권3호
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• pp.160-169
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• 2013

Two-stage turbocharging is an important way to raise engine power density, to realize energy saving and emission reducing. At present, turbine matching of two-stage turbocharger is based on MAP of turbine. The matching method does not take the effect of turbines' interaction into consideration, assuming that flow at high pressure turbine outlet and low pressure turbine inlet is uniform. Actually, there is swirl flow at outlet of high pressure turbine, and the swirl flow will influence performance of low pressure turbine which influencing performance of engine further. Three-dimension models of turbines with two-stage turbocharger were built in this paper. Based on the turbine models, mechanism of swirl flow at high pressure turbine outlet influencing low pressure turbine performance was studied and a two-stage radial counter-rotation turbine system was raised. Mechanisms of the influence of counter-rotation turbine system acting on low-pressure turbine were studied using simulation method. The research result proved that in condition of small turbine flow rate corresponding to engine low-speed working condition, counter-rotation turbine system can effectively decrease the influence of swirl flow at high pressure turbine outlet imposing on low pressure turbine and increases efficiency of the low-pressure turbine, furthermore increases the low-speed performance of the engine.

• Journal of Mechanical Science and Technology
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• 제20권9호
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• pp.1483-1491
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• 2006

The pumping performance of molecular drag pumps (MDP) has been investigated experimentally. The exporimented MDPs are a disk-type drag pump (DTDP), helical-type drag pump(HTDP) and compound drag pump (CDP), respectively In the case of the DTDP, spiral channels of a rotor are cut on both upper surface and lower surface of a rotating disk, and the corresponding stator is a planar disk. In the case of the HTDP, the rotor has six rectangular grooves. The CDP consists with the DTDP, at lower part, and with the HTDP, at upper part. The experiments are performed in the outlet pressure range of $0.2{\sim}533Pa$. The inlet pressure and compression ratio are measured under the various conditions of outlet pressure and throughputs, and nitrogen is used for the test gas. At the outlet pressure of 0.2Pa, the ultimate pressure has been reached to $1.0{\times}10^{-2}Pa$ for the HTDP, $1.3{\times}10^{-4}Pa$ for the DTDP, and $3.6{\times}10^{-5}Pa$ for the CDP. The maximum compression ratio of the CDP is much higher than those of the DTDP or HTDP. Consequently, the ultimate pressure of the CDP is the lowest one.

• 전기학회논문지
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• 제59권1호
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• pp.138-143
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• 2010

This paper presents the analysis, the fabrication and the test results of a micro passive gas pressure regulator to keep the outlet pressure costant even for a widely-varying inlet pressure. This device is to regulate the outlet pressure according to the applied reference pressure based on the pressure balancing mechanism of the structure including a membrane and a valve. This regulator consists of four layers; a bulk-micromachined silicon substrate, a sandblasted glass substrate, a PDMS valve seat layer and a glass valve layer. The device size is $10\times13\times1.7 mm3$. The device was fabricated by micromachining. The characteristic of the device was analyzed and tested. The characteristic of the fabricated pressure regulator is similar to that obtained from the analysis. The pressure regulator of this paper is feasible for portable systems and miniature drug delivery systems.

• 한국추진공학회지
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• 제15권6호
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• pp.47-55
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• 2011

본 논문에서는 매니폴드 내의 튜브 라운드 적용에 따른 고온 고압 튜브형 열교환기에서의 압력강하와 열성능을 분석하기위해 전산해석을 수행하였다. 튜브형 열교환기에서의 압력강하와 열성능은 튜브라운드의 위치에 많은 영향을 받는다. 튜브 라운드에 따른 연구는 튜브 입구, 튜브 출구, 그리고 튜브 양쪽 세 가지 위치에 따라 수행하였다. 본 연구에서, 튜브 양쪽에 라운드를 적용한 경우에는 가장 낮은 압력강하와 감소된 열전달을 보였지만 튜브 출구에 라운드를 적용한 경우에는 압력강하와 열전달 모두 기본형상에 비하여 좋은 특성을 보였다.

• Journal of Biosystems Engineering
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• 제5권2호
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• pp.1-14
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• 1980

This study was carried out to investigate the effects of the counter-pressure setting and the roller speed of a rice whitening machine on the head rice recovery. milling capacity and milling efficiency, and also to find out the optimum operational conditions of the machine. The radial pressure inside the whitening chamber and the outlet axial pressure were measured to study their relationships with the head rice recovery, milling capacity and milling efficiency. The results of the study are summarized as follows. (1) The most important factor in rice whitening was the counter-pressure setting. It significantly affected the head rice recovery. (2) The roller speed significant affected the milling capacity and milling efficiency , but it did not affected the head rice recovery. (3) Both the radial pressure and the outlet axial pressure were affected by the counter-pressure setting but not by the roller speed. Both of them increased almost linearly with the counter-pressure setting. There was a significant correlation between the radial pressure and the outlet axial pressure. (4) The flow rate through the whitening chamber when the feed gate was fully opened increased with the roller speed, but it was not affected by the counter-pressure setting. (5) The head rice recovery decreased as the counter-pressure setting increased , but it was not affected by the roller speed. The reason could be explained by the fact that the radical pressure increased only with the counter-pressure setting. (6) The milling capacity increased with the counter-pressure setting and linearly with the roller speed. The milling efficiency generally increased with both the counter-pressure setting and the roller speed. However, the effect of roller speed was negligible at the higher counter-pressure setting. The temperature rise inside the whitening chamber was moderate with the mean of 11.3℃ (range 5.6-18.3℃) even though it increased slightly with the roller speed. Considering the head rice recovery and milling efficiency, the optimum operational conditions of the machine appeared to be the counter-pressure setting of 67g/㎠ and the roller speed of 1,050rpm. Neglecting the small difference in the head rice recovery , the greater milling capacity could be obtained at the counter-pressure setting of 85g/㎠ with the roller speed of 850-1050rpm.

• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 2004년도 유체기계 연구개발 발표회 논문집
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• pp.70-77
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• 2004

Comprehensive investigation on the outlet's geometric shapes of a centrifugal blower with higher inlet resistance than an atmospheric pressure is carried out for improvements of its performance. Most unwanted behaviors of such blower are pulsating flows because of unbalance between inflows and outflows in a scroll casing. In order to reduce this undesirable phenomenon a triump is made for both the shape of outlet duct and an accessory structure inserted in the outlet port of the blower. The modification on the shape is concerned with the contraction of cross sectional area and the attached structure is for an intentional obstruction to cause a flow resistance. The details of the modification are examined for different cases and results. The methodologies for the work are performance evaluations including noise level and velocity measurements with PIV Consequently, the performance of improved system is close to that of the system operating with atmospheric pressure at the inlet.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2008년도 추계학술대회B
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• pp.2495-2500
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• 2008

We simulated the mixing characteristics in micro T-channel using Lattice Boltzmann Method. We studied the relation a mixing length and pressure-drop due to inlet and outlet ration in Reynolds number 0.5, Peclet number 500 and Schmidt 1000. The ratio of a down-inlet to up-inlet was $0.5{\sim}1.5$ times, up-inlet to outlet was $1{\sim}3$ times and outlet length was 250 times to up-inlet. The mixing length decrease linearly as outlet ratio decreased, and pressure-drip increase non-linearly. Initial stage of micro channel mixture was fast by down-inlet ratio, however, the mixing length is not influence.

• 설비공학논문집
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• 제15권7호
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• pp.579-585
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• 2003

The ejector system is used for making a vacuum in an enclosed tank. This research represents the method to improve ejector performance by inserting a strut at the center of ejector outlet. This proposed ejector system is so simple and have a low cost to improve the ejector performance. There are many kinds of method for obtaining a lower vacuum pressure. The ejector is consists of nozzle, straight pipe and outlet diffuser and we focused on the outlet diffuser for high ejector performance. The strut is located at the center of ejector outlet diffuser. As the experimental result, we compared the vacuum pressure with and without a strut and without strut, and the ejector performance showed an improvement with 40% or more than the case without strut. This means that the stable fluid low energy loss was obtained by inserting the strut.

• Journal of Chest Surgery
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• 제28권2호
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• pp.206-208
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• 1995

Thoracic outlet syndrome presents with symptoms resulting from pressure on either the subclavian vessels or the lower trunk of the brachial plexus. It may be caused by a number of abnormalities, including degenerative or bony disorders, trauma to the cervical spine, fibromuscular bands, vascular abnormalities, and spasm of the anterior scalene muscle. We experienced a case of thoracic outlet syndrome [ caused by cervical rib .We report a case with review of literatures.

• 설비공학논문집
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• 제27권8호
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• pp.402-408
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• 2015

A series of numerical simulations have been carried out to study the performances of cyclone-type oil separators, which are designed for refrigeration-system compressors. The corresponding working fluid is R22, which is a typical refrigerant, whereby a mineral-oil droplet is supplied (Ed-highlight-My interpretation). The outlet-tube length in relation to the total chamber volume is considered a design parameter. Depending on the tube length, the separation efficiency varies from 98.7% to 99.3%, while the predicted pressure drop is between 5.1 kPa and 6.4 kPa. Considering both the pressure drop and separation efficiency, the length of the outlet-port tube of the separator is 152 mm.