http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
Mach Number Determination in a High-Enthalpy Supersonic Arc-Heated Plasma Wind Tunnel
Rajesh Kumar Chinnaraj,오필용,Eui Sup Shin,홍봉근,최성만 한국항공우주학회 2019 International Journal of Aeronautical and Space Sc Vol.20 No.1
In this experimental study, an intrinsic flow diagnostic technique involving a wedge probe is studied in a 0.4MWclass arc-jet plasma wind tunnel. The main objectives of this study are to determine theMach number of flow achieved in the plasma wind tunnel when operated under a typical operating condition using the experimental data obtained from the above-mentioned experimental technique and to perform comparative analysis with theoretically calculated results for the same operating conditions. Total specific enthalpy was determined using simple, yet efficient energy balance method. From total specific enthalpy, other vital flow parameters were estimated.
CHINNARAJ RAJESH KUMAR,홍성민,김호석,최성만 한국항공우주학회 2023 International Journal of Aeronautical and Space Sc Vol.24 No.2
Ablation experiments of three different material specimens for high-temperature aerospace applications, namely Inconel, C–C and SiC were carried out using a high-velocity oxygen-fuel system. Originally designed for spray coating, the HVOF can be used as an easy-to-operate and inexpensive alternative to plasma wind tunnels. The HVOF flow characterization was performed intrusively using a water-cooled Gardon gauge for stagnation point heat fluxes and wedge probes for supersonic Mach numbers. The specimen surface temperatures were measured using a two-colour pyrometer and an IR camera. The SiC specimen showed the maximum surface temperature around 2200 K. The stagnation point heat fluxes were measured at 80 mm, 100 mm, 120 mm, 140 mm, 160 mm and 180 mm away from the HVOF torch nozzle exit as 10.935 MW/m^2, 8.026 MW/m^2, 5.111 MW/m^2, 3.263 MW/m^2, 1.935 MW/m^2, and 1.600 MW/m^2, respectively. Using an HVOF system, this is the first study to report heat flux values measured experimentally at specimen test locations. A constant supersonic Mach number of 1.38 was obtained up to 80 mm of the flow. Three-dimensional mappings were performed to study the specimen surface feature changes before and after the tests. SEM and EDS were performed. The SiC specimen showed excellent ablation resistance, even though it was tested at a higher heat flux condition compared to other two material specimens.
CHINNARAJ RAJESH KUMAR,홍성민,김호석,오필용,최성만 한국항공우주학회 2020 International Journal of Aeronautical and Space Sc Vol.21 No.4
Ablation experiments of four thermal protection system (TPS) candidate specimens, including two UHTCs-coated (HfC and HfC–TiC) specimens, were performed. The specimens were tested at the VKI’s 1.2 MW ICP plasma wind tunnel. Intrusive flow diagnostic techniques (calorimetric probe and Pitot tube) were used to experimentally determine cold wall heat flux and dynamic pressure. Using the wind tunnel operating conditions and the experimental results, numerical codes were solved to characterize the boundary edge conditions. During tests, the specimen wall temperatures were measured optically using a two-colour pyrometer and the specimen internal temperatures were measured using thermocouples. The specimen surface feature changes were determined by three-dimensional mapping of specimen surfaces. The cold wall heat fluxes and dynamic pressure values for tests were in the range from 4.05 to 4.26 MW/m2 and 2.57 to 2.67 mbar, respectively. Two UHTC-coated specimens’ peak wall temperatures were almost 3000 K. The UHTC-coated specimens exhibited surface inflation, i.e., volume increase and the respective mass changes were very small compared to non-UHTC-coated specimens. HfC–TiC specimen’s mass change was positive, contrary to other specimens. The overall performance of HfC–TiC-coated specimen was better than others. TiC layer is considered as the reason for the mass increase and better overall performance.
Heat Flux Measurements in High Velocity Oxygen-Fuel Torch Flow for Testing High Thermal Materials
Rajesh Kumar Chinnaraj,Seong Man Choi(최성만),Seong Min Hong(홍성민) 한국추진공학회 2020 한국추진공학회 학술대회논문집 Vol.2020 No.7
고열 재료를 시험평가 하기 위한 HVOF 흐름에서 가든 게이지(Gardon gauge)를 이용하여 열유속을 측정하였다. 노즐 출구로부터 4 개의 다른 위치에서 열유속 측정을 수행하였다. 실험 중 가든 게이지를 수냉시켰다. 유효한 가정을 적용하여 열량 열유속(Calorimetric heat flux)을 계산하고 가든 게이지의 열유속 측정 결과와 잘 일치하는 것으로 나타났으며, 따라서 서로를 검증했습니다. A Gardon gauge was used to measure heat fluxes in a HVOF flow intended for testing high thermal materials. The measurements were taken at four different locations from the nozzle exit. The Gardon gauge was water cooled during the experiments. Applying valid assumptions, the calorimetric heat fluxes were calculated and were shown to be in good agreement with Gardon gauge heat flux results, thus validating each other.
Rajesh Kumar Chinnaraj,장현식(Hyeon Sik Jang),오필용(Phil Yong Oh),홍성민(Seong Min Hong),최성만(Seong Man Choi) 한국연소학회 2020 한국연소학회지 Vol.25 No.1
Need to improve the performances of the gas turbines and rocket engines are hindered by the limitations caused by melting points of the metallic super alloys at the combustor outlet nozzle or turbine components. High thermal resistive non-metallic materials are considered as future solutions to this problem. Most of these alternative non-metallic materials are carbon based composite materials and these materials can enable the gas turbines or rocket engines to operate at temperatures higher than the metallic super alloys. In this paper, a hydrocarbon fuel based evaluation system for carbon based composite materials is introduced. This evaluation system allows the testing and validation of the material specimens in a fuel burnt high thermal flow. The local Mach numbers were measured at five different locations using wedge probes in the flow’s axial direction. The results reveal that the measured Mach numbers were almost constant about 1.4. The Mach number results indicate the flow generated by the evaluation system was stable and suitable for material evaluation.
Supersonic Mach Disk Characteristics in a Plasma Wind Tunnel
Rajesh Kumar Chinnaraj(친나라즈라제쉬쿠마),Philyong Oh(오필용),Seongman Choi(최성만) 한국추진공학회 2018 한국추진공학회 학술대회논문집 Vol.2018 No.5
0.4 MW 급 고 엔탈피 초음속 아크 가열 플라즈마 풍동에서 발생된 팽창 유동에 대한 기초연구를 실험적으로 완료하였다. 노즐 출구로부터의 마하 디스크의 직경과 위치는 전체 압력비가 200에서 30까지 측정되었다. 마하 디스크 직경과 위치에 대한 경험적인 상관관계는 실험결과와 매우 일치하는 결과를 얻었다. A primary investigation on the underexpanded flow generated in a 0.4 MW class high enthalpy supersonic arc-heated plasma wind tunnel is conducted experimentally. The diameter and the position of the Mach disk from the nozzle exit is measured for overall pressure ratios ranging from 200 to 30. The empirical correlations for Mach disk diameter and position are determined which show very good agreement with experimental results.
친나라즈라제쉬쿠마(Rajesh Kumar Chinnaraj),박규상(Gyusang Park),오필용(Philyong Oh),최성만(Seongman Choi) 한국추진공학회 2015 한국추진공학회 학술대회논문집 Vol.2015 No.5
우주선의 열 보호 시스템(TPS)은 대기에 진압하는 동안 극한의 상황에 노출된다. 따라서 극한 상태에서의 열 보호 시스템의 재료에 대한 실험의 필요성은 증가하고 있다. 본 논문에서는 우주선이 대기에 진입하는 극한의 환경을 모사한 상태에서의 재료실험을 다루고자 한다. 재료시편은 극한환경의 플라즈마 유동에 노출시키고, 열전대, 파이로미터, 적외선 카메라 등의 접촉 및 비 접촉식 측정 기술을 사용해서 재료의 특성을 파악하고자 한다. Thermal protection systems(TPS) of space vehicles are subjected to extreme conditions during atmospheric entry. So there raises a need for extreme condition testing of TPS materials. This paper presents an experiment in a simulated condition which space vehicles endure during atmospheric entry. The specimens are subjected to same extreme conditions with the help of plasma wind tunnel. The characterization of the specimen is done from intrusive and non-intrusive measurement techniques such as thermocouples, pyrometer and infrared thermography.