• Journal of the Korean Society of Propulsion Engineers
• /
• v.25 no.6
• /
• pp.12-19
• /
• 2021

An experimental study was performed for a cavitating venturi supplying a constant rate of flow independent of downstream pressure fluctuations when providing liquid propellant. The venturi was designed and manufactured in order to figure out the performance of the cavitating venturi. Effects of the rear-end shape, upstream pressure, and back pressure on the ratio of downstream to upstream pressure of the venturi as well as the flow-rate were observed. As a result, critical pressure ratio of the venturi, which generally depends only on the configuration of the venturi, was kept at 0.74 regardless of the rear-end shape and the upstream pressure of the venturi.

• Journal of the Korean Society of Propulsion Engineers
• /
• v.19 no.4
• /
• pp.1-7
• /
• 2015

A cavitation venturi is a device that allows a liquid flow rate to be fixed or locked independent of a downstream pressure and has been successfully used in a liquid rocket engine system which requires a stable propellant flow rate. In the present research, four cavitation venturis which have same dimensions except for converging inlet angle and diverging outlet angle, were designed and manufactured. Flow rates through each venturi and upstream/downstream pressures were measured by changing the pressures. From the experimental data, the discharge coefficients and critical pressure ratios were calculated for each venturi. It was found that the inlet and outlet angles of the cavitation venturi affected the discharge coefficient, and the outlet angle influenced on the critical pressure ratio.

• Proceedings of the KAIS Fall Conference
• /
• 2011.12a
• /
• pp.262-265
• /
• 2011

본 연구는 탈진 기류 분사 시스템의 최적화 설계에 관한 기초 연구의 일환으로 전산유체역학(CFD)을 이용하여 일반 블로우 튜브와 단순 벤츄리 조합의 충격 기류(Pulse air jet) 방식의 탈진 장치에 대한 탈진 성능과 벤츄리 입구에 기류 유도용 구조물을 설치한 경우의 탈진 성능을 비교하였다. 각 Case별로 벤츄리 내부로 유입되는 탈진 공기량을 예측한 결과, case 2의 벤츄리 형상 개조시 case 1 보다 벤츄리로 유입되는 탈진 공기량이 약 20% 증폭되는 것으로 나타났다. 또한 필터백 표면에서의 탈진 기류 전달 분포를 예측한 결과, 모든 case가 필터백의 국한된 영역으로 탈진 기류가 집중됨을 알 수 있었다. 또한, case 2의 경우가 case 1보다 오히려 탈진 기류의 전달 수준이 불량함을 알 수 있다. 이는 case 2의 경우 벤츄리 입구에 기류 유도용 구조물을 설치한 것이 탈진 공기량을 증폭시키는데에는 도움이 되나, 오히려 벤츄리 내부로 유입된 탈진 기류의 직진성을 보완하여 필터백 내부에서 탈진 기류의 확장을 방해하기 때문인 것으로 판단된다.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.38 no.10
• /
• pp.865-871
• /
• 2014

This study was conducted with the aim of developing a venturi-type air supply system for a microbubble generator. In order to determine the influence of the varying geometry of the venturi tube on the flow characteristics, a computational fluid dynamics (CFD) simulation was performed using the commercial CFD software ANSYS CFX-15. Furthermore, in order to elucidate the effects of variation in major design dimensions such as the air supply hole size, position of holes, and number of holes on the air supply characteristics, two-phase multiflow CFD analysis was performed. The analysis results showed that the starting point of expansion on the venturi tube with 0.75 is the best hole position and that the air supply hole size and the number of holes are linearly proportional to the amount of air.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.16 no.2
• /
• pp.1571-1578
• /
• 2015

The cleaning characteristics of pulse air jet type cleaning system which is widely applied in the industries were identified by utilizing the computational fluid dynamics (CFD) and the cleaning performance in modified shape of dedusting unit was compared in this study. The review on each shape of cleaning part showed that the case of installing the nozzle on the blow tube (Case-3) and the case of installing the double intaking tube to the venturi (Case-4 and Case-5) were more excellent than the structure (Case-1). Also, the optimal venturi shape was designed and examined its applicability to the site in a pilot scale plant. A combined system of a blow tube and a venturi proposed by this study turned out to be very effective for concentrating an cleaning air compared to existing systems, such as using only blow tube and combines the blow tube and venturi. In addition, as a result of installing and testing a venturi proposed by this study, the cleaning frequency and cleaning time were much improved compared to a case of using a commercial venturi that is under use at the industrial sites.

• Journal of the Korean Society of Propulsion Engineers
• /
• v.6 no.2
• /
• pp.29-36
• /
• 2002

Experiments have been performed to investigate the effect of secondary venturi tip angle on flow and spray characteristics in gas turbine combustor with a swirl cup assembly. Three variations of secondary venturi tip angle are made: converging, straight and diverging angles. It is found that the variation of venturi tip angle results in the significant changes of flow and spray characteristics in gas turbine combustors, such as the size and location of recirculation zones. drop size and mass distribution affecting combustion efficiency and NOx emissions. In diverge case, central toroidal recirculation zone(CTRZ) exists near the exit, which is known to be beneficial for flame stability. But in converge case, the finest SMD distribution and uniform mass distribution are found and CTRZ is longer than other cases. Consequently, high combustion efficiency and low pollutant emission are expected in converge case.

• Journal of Korean Society of Environmental Engineers
• /
• v.32 no.12
• /
• pp.1119-1125
• /
• 2010

Most of the sludge pre-treatment methods to improve the anaerobic digestibility of sludge are not practied in the fields with low economical efficiency. The venturi cavitation system (VCS) adopting hydrodynamic cavitation is simple and requires low energy. This research was conducted to investigate the optimum design and operating conditions of the VCS. The experimental results indicated that the optimum number of venturi in series was three, and the suction mode operation of the pump yielded 1.6 times higher pre-treatment efficiency per unit energy consumption than the discharge mode. The combination of venturies with different throat sizes did not affect the pre-treatment efficiency. Also, the parallel installation of the three in series venture unit yielded 30% higher pre-treatment efficiency per unit energy consumption than the single unit. Under parallel conditions, the solubilization efficiency was 5.6 mg ${\Delta}SCOD/g$ TS/kWh, which is higher than the previously reported value.

• Proceedings of the KAIS Fall Conference
• /
• 2012.05a
• /
• pp.371-374
• /
• 2012

본 연구는 "사이클론과 관성충돌 및 백필터의 제진원리를 일체화한 고효율 멀티 제진시스템의 최적화 설계를 위한 수치 해석적 연구(I) : 집진기 입구 최적화 설계"에 이은 일련의 연구로서 앞선 연구에서 도출된 사이클론부 하단 벤츄리(Venturi)에서의 강한 하향 기류의 가속에 따른 분진 재비산 가능성에 대한 추가적 검토를 위한 연구이다. 사이클론부를 통과한 기류가 상향 흐름으로 방향을 전환할때 좀 더 가속시켜 빠르게 곡률반경을 형성하여 조대 입자의 분리를 극대화시키기 위한 목적으로 사이클론부 하단을 벤츄리 형상으로 설계하였으나, 유동장 분석 결과 벤츄리를 통과한 처리가스 흐름이 가속되면서 호퍼 하단까지 약 4~5 m/s의 강한 하향 흐름을 형성하고 호퍼 하부의 말단 부근에서 상향 흐름으로 방향 전환을 하고 있는 것으로 예측됨에 따라 설계 의도와는 달리 벤츄리 설치시 호퍼 하단에 포집된 분진의 재비산을 예방하는데는 크게 역할을 하지 못하는 것으로 나타났다.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.36 no.12
• /
• pp.1161-1169
• /
• 2012

A numerical study has been conducted to investigate the aerodynamic characteristics and behavior of a wing-tip vortex around a three-dimensional symmetric wing (NACA0015) in the vicinity of the ground. The aerodynamic characteristics and the wing-tip vortex change as a wing approaches the ground as a result of two different phenomena: the ground effect and the Venturi effect. The ground effect increases lift and decreases drag whereas the Venturi effect generates negative lift and increases drag suddenly. A symmetric airfoil experiences both phenomena with respect to changes in the angle of attack. In the case of a NACA0015 airfoil, the Venturi effect is dominant at small angles of attack but the ground effect is dominant at large angles of attack. Interestingly, both phenomena can be observed at the 4 degree of angle of attack. The vortex core moves inside a wing when the wing experiences the Venturi effect, whereas the vortex core moves outward when the wing experiences the ground effect.

• Proceedings of the Korean Society of Propulsion Engineers Conference
• /
• 2000.04a
• /
• pp.28-28
• /
• 2000

가스터빈 연소기의 역방향 이중 스월러의 두 번째 벤츄리 끝단 각도의 변이가 연소실내의 유동 특성에 미치는 영향에 대해 알아보았다. 벤츄리 끝단 각도가 수렴형, 직선형, 발산형의 세 형상에 대해 연료 분무가 없는 경우, 연료 분무는 있으나 연소는 없는 경우, 연소가 일어나는 경우에 대해 수치적 방법으로 연소실 내의 유동 특성에 대해 고찰하였다. 연료의 분무는 분무된 액적들이 갖는 운동량이 유입되는 공기의 운동량에 비해 적으므로 분무에 의한 유동 특성의 변화는 무시할 수 있는 반면 연소가 일어날 때는 유동 특성이 판이하게 달라짐을 확인할 수 있었다. 가스터빈 연소실 내의 유동 특성은 벤츄리 끝단 각의 변이에 따라 민감하게 변하고 있다.