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강정식,조성국,강신형,Kang, Jeong-Seek,Cho, Sung-Kook,Kang, Shin-Hyoung 한국유체기계학회 2000 한국유체기계학회 논문집 Vol.3 No.2
The aim of this paper is to understand the unsteady flow phenomena in a high speed centrifugal compressor channel diffuser. Instantaneous pressures aye measured at six locations in the diffuser using fast-response pressure transducers. Instantaneous pressure ratio decomposition was applied to analyze the pressure signal. In vaneless space where impeller-vaned diffuser interaction is strong, aperiodic unsteadiness is high and periodic pressure waveforms by blade passing are not clear at low flow rates, especially near vane suction side. High aperiodic unsteadiness decreases downstream of diffuser. The blade-to-blade pressure wave does not disappear in surge flow condition. In surge there exist not only large scale periodic surge wave but also blade-to-blade pressure wave.
강정식,김진선,김진한,Kang, Jeong-Seek,Kim, Jin-Sun,Kim, Jin-Han 한국유체기계학회 2004 한국유체기계학회 논문집 Vol.20 No.2
Cryogenic pump test facility (CPTF) is designed and developed in KARI. Hydraulic and cavitation performance of pump and inducer in cryogenic environment can be measured. Working fluid is liquid nitrogen and operating temperature is $-197^{\circ}C$. Run tank, catch tank of liquid nitrogen and their pressurizing tank has been built and remote tank pressure control system are installed. Maximum power of driving motor is 320 kW and its maximum speed is 32000rpm. Cryogenic fluids and lubricating systems are effectively separated that long test times are acquired. Therefore hydraulic and cavitation performance can be measured accurately and effectively. Pre-cooling test of the facility was successfully accomplished. This facility will contribute greatly to the development of turbopump for KSLV.
강정식(Jeong-Seek Kang),강신형(Shin-Hyoung Kang) 한국유체기계학회 2000 유체기계 연구개발 발표회 논문집 Vol.- No.-
본 연구에서는 고속의 원심압축기에서 스톨 발단에 관한 연구를 수행하였다. 스톨을 일으키는 요인과, 스톨이 발생하기 전에 이를 미리 경고할 수 있는 방법을 주된 연구 주제로 삼았다. 원주방향으로 균일하게 분포된 8개의 고속응답 압력변환기를 사용하여 순간압력을 측정하였으며, 이 신호를 공간 푸리에 변환(space Fourier transform)을 사용하여 스톨의 발단을 알리는 신호를 측정하였고, 회전하는 파의 에너지(Traveling Wave Energy) 방법을 사용하여 스톨을 미리 경고하는 방법에 대하여 연구하였다. 회전하는 파의 에너지 방법은 스톨을 경고하는 데 좋은 성능을 보였으며, 저속에서는 약 임펠러 100회전, 중간속도에서는 약 200회전, 그리고 고속에서는 약 임펠러 1000회전의 경고시간을 보였다. 그리고 스톨 발단 근처에서 공간 푸리에 계수의 위상이 임펠러 주파수의 속도로 선형적인 증가를 보이는 구간이 나타났으며 또한 임펠러 주파수의 스펙트럼이 스톨로 접근하면서 증가하는 것으로부터, 임펠러 주파수가 스톨을 일으키는 중요한 요인으로 작용함을 알 수 있었다. 또한 임펠러의 회전속도에 관계없이 스톨로 접근하면서 임펠러 주파수의 스펙트럼이 증가하므로, 이 값이 스톨을 경고하는 방법으로 사용될 수 있음을 보였으며, 약 임펠러 200회전의 경고시간을 얻을 수 있었고, 임펠러의 속도가 빠를수록 긴 경고시간을 얻었다. 이 방법의 개발로 하나의 센서의 측정만으로도 효과적으로 스톨을 경고할 수 있는 기반을 마련하였다.
강정식(Kang Jeong-Seek),강신형(Kang Shin-Hyoung) 대한기계학회 2002 대한기계학회 춘추학술대회 Vol.2002 No.5
This paper is focused on stall inception at vaneless diffuser of a centrifugal compressor. Eight fast-response pressure transducers are equally spaced around the circumference at the inlet and exit of a vane less diffuser. Experiments are done from 20000rpm to 60000rpm for the diffuser stall. Two-cell structure which rotates at 6~10% of impeller speed is fully developed at 20000~ 40000rpm, and three-cell structure which rotates at 7~9% of impeller speed is fully developed at 50000~60000rpm. It is found that two-cell and three-cell structures of small amplitude wave grow and decay repeatedly before they fully develops to rotating stall, which is named as pre-cell. When it appears, then the phase of spatial Fourier coefficient increases linearly and the traveling wave energy increases. The pre-cell travels at or slightly lower than the speed of fully developed rotating stall, and its growing-decaying life time is about several decade of impeller revolutions. Pre-cells of two-cell and three-cell structures are found to interact in their growing and decaying mechanism through transferring energy from one structure to the other. These phenomena that pre-cells grow and decay repeatedly and finally lead to fully developed rotating stall are different stall inception pattern with mode and spike which are well known stall inception pattern in axial compressors. So it is named as pre-cell stall inception. This is thought to be characteristic stall inception pattern in vaneless diffuser of centrifugal compressor.
강정식(Jeong-Seek Kang),조성국(Sung-Kook Cho),강신형(Shin-Hyoung Kang) 한국유체기계학회 1999 유체기계 연구개발 발표회 논문집 Vol.- No.-
The aim of this paper is to understand the unsteady flow phenomena in a high speed centrifugal compressor channel diffuser. Instantaneous pressures are measured at six locations in the diffuser using fast-response pressure transducers. Instantaneous pressure ratio decomposition was applied to analyze the pressure signal. In vaneless space where impeller-vaned diffuser interaction is strong, aperiodic unsteadiness is high and periodic pressure waveforms by blade passing are not clear at low flow rates, especially near vane suction side. High aperiodic unsteadiness decreases downstream of diffuser. The blade-to-blade pressure wave does not disappear in surge flow condition. In surge there exist not only large scale periodic surge wave but also blade-to-blade pressure wave.
강정식(Jeong-Seek Kang),임병준(Byeung-Jun Lim),안이기(Iee-Ki Ahn) 한국유체기계학회 2009 유체기계 연구개발 발표회 논문집 Vol.2009 No.-
Experimental study on the flow field inside the nozzle for radial turbine was performed. At design point, the pressure is high and the Mach number is low at the pressure side of the nozzle inlet semi-vaneless space as the flow turns through the nozzle vanes. As the flow accelerates through the nozzle passage to the throat the pressure level at the pressure and suction sides becomes similar. The flow continued accelerating from the throat to the inlet of turbine wheel and the pressure field became uniform in the circumferential direction in the vaneless space. In high expansion ratio condition, strong favorable pressure gradient band region occurred just after the throat in the semi-vaneless space in the circumferential direction and the pressure became uniform in the circumferential direction after this band. In low expansion ratio condition, core flow acceleration is dominant after the throat and this non-uniform pressure field reached to the inlet of turbine wheel.
강정식(Jeong-Seek Kang),김춘택(Chun Taek Kim),김창근(Chang Geun Kim),안이기(Iee-Ki Ahn),이대성(Dae-Sung Lee) 한국유체기계학회 2007 유체기계 연구개발 발표회 논문집 Vol.- No.-
This paper presents the development of 2-stage powerturbine for turboshaft engine. This engine is a latest turboshaft engine which is upgraded from T700 engine series. Its power class is designed to fit the helicopter mission. And it is a rear-drive engine to fit into the helicopter. The speed of powerturbine increased about 13% from its predecessor and the its rotating direction is contrary to that of GGT. Despite these restrictions, the powerturbine is designed to have longer life and higher efficiency than its predecessor. The efficiency of powerturbine increased about 1.4 % and its life has increased more than 20 %.