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자동차용 터보차저의 오버헝 압축기 볼류트의 두 형태에 대한 유동장 특성
Zhou Tianjun,이근식(Geun Sik Lee) 대한기계학회 2014 大韓機械學會論文集B Vol.38 No.1
자동차용 터보차저 원심압축기의 오버헝 볼류트의 두 가지 타입에 대한 유동장 특성이 수치적으로 연구되었다. 볼류트의 성능을 높이기 위해서는 높은 압력회복계수와 낮은 손실계수를 갖도록 함이 필요하다. 본 연구에서는 디퓨저 입구각을 24°, 질량유량을 0.055 kg/s 로 유지하고 두 가지 타입의 오버헝 볼류트에 대한 유동장 특성을 조사하였다. 하나는 1 개의 원호로 이루어진 볼류트 단면(타입 1)이며, 다른 하나는 3 개의 원호로 이루어진 볼류트 단면(타입 2)이다. 타입 2 볼류트가 타입 1 볼류트 보다 원주방향 전체를 통틀어 높은 압력회복계수와 낮은 손실계수를 보여주었다. The flow characteristics of two types of overhung compressor volutes for automobile turbochargers were analyzed numerically using commercial software. For obtaining high performance from a volute, it is necessary that the volute have a high pressure recovery coefficient and a low loss coefficient. We investigated the flow characteristics of two types of overhung compressor volutes with a fixed diffuser inlet angle of 24° and a mass flow rate of 0.055 kg/s. The first type is a volute with one-arc cross section (type 1) and the second type is with three-arc cross section (type 2). Our results showed that between the two types of volutes, type 2 had the higher pressure recovery coefficient and the lower loss coefficient along the entire angular position.
원주방향 볼류트 입구 높이를 수정한 자동차용 터보차저 원심압축기의 성능 향상
Zhou Tianjun,이근식(Geun Sik Lee) 대한기계학회 2014 大韓機械學會論文集B Vol.38 No.2
자동차용 터보차저 압축기의 성능 개선을 위해 원주방향의 볼류트 입구 높이들이 수정되었고 디퓨저를 포함한 볼류트에 대한 유동장이 상용 소프트웨어를 사용하여 조사되었다. 기본적으로 잘 설계된 볼류트는 높은 압력회복계수와 낮은 전압력손실계수를 보여주어야 한다. 본 연구에서는 동일한 단면형상과 설단면각(Tongue Angle)을 가지나 원주방향으로는 서로 다른 볼류트 입구 높이를 갖는 두 경우의 원형단면 볼류트가 선정되었다. 하나는 90° 원주방향에서는 단면 중앙으로 유입되나 이후의 원주방향에서는 볼류트 단면 최하단부들을 잇는 접선과 동일한 높이를 유지하면서 점진적으로 하단부로 유입되는 볼류트 형상이다(케이스 1 볼류트). 다른 하나는 설단면에서는 접선방향으로 유입되도록 모든 원주방향에 대하여 입구 높이를 2 ㎜ 낮춘 형상이다(케이스 2 볼류트). 해석결과, 케이스 2 볼류트가 케이스 1 볼류트보다 높은 압력회복계수로 인한 높은 전압력비와 낮은 전압력손실계수로 인한 높은 등엔트로피 효율을 보여주었다. To enhance the performance of an automobile turbocharger compressor, the circumferential inlet heights of the volute were modified and the flow field for the combined region of the diffuser and volute was numerically investigated using commercial software. Basically, a well-designed volute should have a high pressure recovery coefficient and a low loss coefficient for the total pressure. In this study, two circular volutes with the same cross sectional shape and tongue angle, but circumferentially different volute inlet heights, were selected. One volute had the middle inlet in the cross-section at the circumferential angle of 90o but gradually lower inlet heights for the angles between 90° to 360 o with respect to the cross sectional center of the volute, while maintaining the same height between the tangential line connecting the lowest positions of the cross section and the line connecting the volute inlets in the circumferential direction (case 1 volute). The other volute has an inlet height that is 2 ㎜ lower than in case 1 volute such that the tongue section has a tangential inlet (case 2 volute). The results showed that the case 2 volute had a higher total pressure ratio because of its higher pressure recovery coefficient and higher isentropic efficiency, resulting from the lower loss coefficient along the circumferential position than the case 1 volute.
냉기입구 형상변화에 대한 고온교반실 내부 열유동 특성 수치해석
Zhou Tianjun,이근식(Geun Sik Lee) 대한기계학회 2018 大韓機械學會論文集B Vol.42 No.10
고온교반실은 산업현장에서 요구되는 적정 온도를 얻기 위하여 고온 및 저온유체를 서로 섞는 장치이다. 본 연구에서는 서로 다른 냉기입구형상을 갖는 고온교반실에서 유동 및 온도특성을 FLUENT를 이용하여 조사하였다. 냉기입구 수는 2, 3, 4이다. 2개의 냉기입구에 대하여, 4개의 모델은 (단면 원주상에서) 서로 다른 입구각 90°, 120°, 150°, 180°을 가진다. 따라서 120°의 입구각을 갖는 3개의 냉기입구 모델과 90°의 입구각을 갖는 4개의 냉기입구 모델을 포함하여 총 6개의 모델에 대한 수치해석이 수행되었다. 해석결과로부터, 3개의 냉기입구 모델의 경우가 가장 높은 성능(가장 높은 출구온도분포 균일도와 가장 낮은 외부표면온도)을 가짐을 알 수 있었다. The hot mixing chamber (HMC) is a device that mixes streams of fluid to obtain gas with a pertinent operational temperature in the final outlet section that can meet the industry requirements. In this numerical simulation study, the flow and temperature characteristics in the hot mixing chamber in different cold air inlets conditions were obtained using the software FLUENT. The number of cold air inlets was 2, 3 and 4. For the two cold air inlets, there were four models with various inlet angles of 90°, 120°, 150° and 180°. Therefore, a total of six models including 3 air inlets angle of 120° and 4 air inlets angle of 90°, were simulated in this study. The simulation results showed the model with 3 cold air inlets had the best performance for the highest temperature uniformity at the HMC outlet and the lowest wall temperature over the surface of the HMC.
REVIEW Advances in Research of ENSO Changes and the Associated Impacts on Asian-Pacific Climate
Tianjun Zhou,Bo Wu,Lu Dong 한국기상학회 2014 Asia-Pacific Journal of Atmospheric Sciences Vol.50 No.4
This review provides a summary on the recent major advances in research of ENSO changes and the associated impacts on Asian-Pacific climate. Achievements in the following topics are summarized: 1) the asymmetry between El Niño and La Niña; 2) the different features of central Pacific (CP) El Niño and eastern Pacific (EP) El Niño; 3) the change of ENSO in a warming world, including analysis of pre-industrial control simulation, historical simulation and climate projections of coupled climate system model; 4) Impact of EP ENSO on warm-pool air-sea interaction and East Asianwestern North Pacific summer monsoon; 5) Impacts of CP ENSO on Asian-Pacific climate, with focus on East Asian seasonal precipitation and tropical cyclones in the western Pacific. Research results published in the recent 5 years are the major sources for this review. Based on the review of the current progresses, some challenging issues needed to be investigated in the future are highlighted.
터보차저 압축기에서 3-원호 단면 오버헝 볼류트의 두 형태에 대한 유동장 특성
Zhou Tianjun,이근식(Geun Sik Lee) 대한기계학회 2013 대한기계학회 춘추학술대회 Vol.2013 No.12
Flow characteristics of two types of 3-arcs overhung compressor volute for an automobile turbocharger were numerically investigated using CFX. High performance of a volute needs to have higher pressure recovery coefficient and lower loss coefficient. The air flow angle coming into the vaneless diffuser is assumed 24 degree and the inlet mass flow rate is 0.055kg/s. One type is the volute with the radially long cross section composed of the 3-arcs (type 1) and the other with the axially long cross section composed of the different 3-arcs (type 2). Results showed that type 2 had higher pressure recovery coefficient and lower loss coefficient along angular position than type 1.
Enhancement of the turbocharger compressor performance by designing a new housing structure
Zhou Tianjun(주천준),Geun Sik Lee(이근식) 대한기계학회 2018 대한기계학회 춘추학술대회 Vol.2018 No.12
In this study, we examined two turbocharger compressor housing structures to improve the turbocharger compressor pressure ratio and efficiency. A certain type of recirculating casing treatment(RCT) can improve the compressor performance near the surge line. And a Hybrid RCT adopting both RCT in the inlet duct and a passage from a volute section to the RCT side can improve the compressor performance at a certain engine operating range. There are 8 different hole position models for Hybrid RCT compressor. Using the CFX software, we obtained the simulation results of all compressor models. At 140,000RPM, the Hybrid-RCT with the different connecting hole position has different performance for pressure ratio and efficiency. Among 8 Hybrid-RCT models, the Hybrid 270D model showed the best performance in the operating range from 0.077kg/s to 0.10kg/s.