• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.44 no.12
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• pp.1062-1070
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• 2016

The heat transfer and flow characteristics of gas turbine blade tip were investigated in this paper by using the conjugate heat transfer analysis. The rotor inlet boundary condition profile which was taken from the first stage nozzle outlet was used to analyse. The profile contained the velocity and temperature information. This study presents the influence of tip clearance about aerodynamic loss, heat transfer coefficient and film cooling effectiveness with the squealer tip designed blade model which tip clearance variation range from 1% to 2.5% of span. Results showed that the aerodynamic loss and the heat transfer coefficient were increased when the tip clearance was increased. Especially when the tip clearance was 2% of the span, the average heat transfer coefficient on the tip region was increased obviously. The film cooling effectiveness of tip region was increasing with decreasing of the tip clearance. There was high film cooling effectiveness at cavity and near tip hole region.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 1998.04a
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• pp.7-7
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• 1998

가스터빈 엔진의 효율 및 성능은 터빈입구온도에 크게 좌우되므로, 높은 열효율을 얻기 위하여 최근 가스터빈 엔진은 높은 입구온도(대략 1400-150$0^{\circ}C$)에서 작동되도록 설계되고 있다. 이는 요소재질의 열한계점을 훨씬 상회하며, 이와 같은 입구온도의 고온화 경향은 터빈요소에 대한 열부하를 증가시키고 있다. 따라서 극한의 작동조건하에서의 허용수명 및 안정성의 유지를 위해서 내부대류냉각, 충돌세트냉각과 더불어 막냉각기법이 많이 응용되고 있다. 막냉각기법은 연소기 벽면 혹은 터빈블레이드 표면의 작은 구멍들을 통해서 압축기의 공기를 분사하여 표면에 고온의 유체와 일종의 단열벽을 형성하여 표면을 보호하는 냉각방법이다. 지금까지는 주로 단면적이 일정한 막냉각홀에 대한 연구가 주가 되어왔으나, 이러한 막냉각홀을 이용하는 경우 많은 문제점이 발생한다.

• Transactions of the KSME C: Technology and Education
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• v.4 no.2
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• pp.93-99
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• 2016

High pressure nozzles and turbines of a gas turbine engine should be required to be operated under extreme operating conditions in order to maximize the performance. Engine manufactures have utilized nickel-base superalloys, enhanced cooling design, and thermal barrier coating techniques to overcome them and furthermore, material modeling, finite element analysis, optimization techniques, and etc. have been utilized widely for elaborate predictions. We aim to evaluate the effects on the low cycle fatigue life of the high pressure turbine blade caused by thermal barrier coatings and the cooling design of the endwall of the first stage turbine nozzle. To achieve it, the structural analysis, which utilized the results of conjugate heat transfer analysis as loading boundary conditions, was performed and then the results were the input for the assessment of low cycle fatigue life at several critical zones.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2008.11a
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• pp.181-184
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• 2008

Austenitic stainless steel is used as high temperature components such as gas turbine blade and disk because of its good thermal resistance. In the present investigation, tensile and low cycle fatigue behavior of 316 stainless steel was studied at wide temperature range $20^{\circ}C{\sim}750^{\circ}C$. In the tensile tests, it was shown that elastic modulus, yield strength, ultimate tensile strength decreases when temperature increased. The effect on fatigue failure of the parameters such as plastic strain amplitude and plastic strain energy density was also investigated. With the experimental results, a structural analysis of turbine blades of 316 stainless steel were carried out.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.4
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• pp.475-480
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• 2010

The thermal barrier coating of a gas turbine blade was degraded by isothermal heating in a furnace and by varying the exposure time and temperature. Then, a micro-Vickers hardness test was conducted on the cross section of the bond coat and Ni-based superalloy substrate. Further, the thickness of TGO(Thermally Grown Oxide) was measured by using an image analyzer, and the changes in the microstructure and element contents in the coating were analyzed by using an optical microscope and by performing SEM-EDX analysis. No significant change was observed in the Vickers hardness of the bond coat when the coated specimen was degraded at a high temperature; delamination was observed between the top coat and the bond coat when the coating was degraded for 50 h at a temperature $1,151^{\circ}C$.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.27 no.4
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• pp.21-26
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• 2019

The purpose of this study is to suggest a method for the efficient preventive maintenance of aircraft gas turbine engine turbine blades. For this study, the types and characteristics of gas turbine engines and its turbine blades were studied, the turbine blade defect types that caused an In-Flight Shut Down(IFSD) were analyzed, the blade failure rate according to the blade life cycle was analyzed through the Weibull distribution, one of the statistical techniques. Through these research results, it is possible to supplement the problems of the life cycle management and maintenance method of the turbine blade, and to suggest the measures to strengthen the preventive maintenance of the turbine blade. In this analysis, when total cycle of turbine blade exceeds 18,000 cycles, the failure rate is over 98%, and then the special management measures are required.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.37 no.6
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• pp.769-774
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• 2013

Turbine blades and disc, which are one of the most important rotating parts of a gas turbine engine, are required to have highly efficient performance in order to minimize the total life cycle costs. Owing to these requirements, these components are exposed to severe conditions such as extreme turbine inlet temperatures, high compression ratios, and high speeds. To evaluate the structural integrity of a turbine disc under these conditions, material modeling and finite element analysis techniques are essential; furthermore, shape optimization is necessary for determining the optimal solution. This study aims to generate 2D finite element models of an axisymmetry model and a sector one and to perform thermal-structural coupled-field analysis and contact analysis. Structurally vulnerable areas such as the disc bore and disc-blade interface region are analyzed by a parametric study. Finally, an improved design is provided based on the results, and the necessity of elaborate shape optimization is confirmed.

• The KSFM Journal of Fluid Machinery
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• v.15 no.3
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• pp.51-56
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• 2012

This study analyzed the influence of firing biogas on the performance and operation of a gas/steam turbine combined system. A reference gas/steam turbine combined system, designed with biogas fuel(57% volumetric methane) was set up and off-design simulation was made to investigate operating characteristics when a couple of operating schemes to mitigate turbine blade overheating were applied. Performance at base-load operation using each scheme was compared and part load operation using the variable inlet guide vane was analysed. Also, differences in operating characteristics and performance caused by changes in the methane content of biogas and ambient temperature were examined.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.11
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• pp.765-770
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• 2020

The turbochargers used widely in diesel and gasoline engines are effective devices to reduce fuel consumption and emissions. In this study, the isentropic turbine efficiency of the steady flow in a twin-scroll turbocharger for the passenger vehicle gasoline engine was analyzed. The cold gas test bench was designed and made. The pressure and temperature of the inlet and exit of the turbine were measured at 60,000, 70,000, 90,000, and 100,000rpm under the steady-state flow. The isentropic turbine efficiency was calculated. The efficiency was the range of 0.53 to 0.57. The BSR and expansion ratio were changed from 0.71 to 0.84 and from 1.24 to 1.72, respectively. The isentropic turbine efficiency decreased with increasing BSR and expansion ratio. The operation of only scroll A or B was compared with that of the twin-scroll turbine. The isentropic efficiency of using only scroll B was higher than those of only scroll A at 60,000rpm. The isentropic efficiency of using only scroll A was higher than those of only scroll B at 100,000rpm. Therefore, the twin-scroll turbine used in this study is operating effectively in the wide speed range.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 1998.04a
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• pp.8-8
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• 1998

Alloy 718은 Fe을 다량 함유하고 있어 가격이 저렴하고 엔진 작동조건에서 내열강도, 내환경성 등이 우수하여, 터빈디스크, 터빈샤프트, 터빈실, 압축기 블레이드 등에 다양하게 이용되고 있다. 이 합금은 고온에서 반복응력을 받는 부위에 대부분 사용되기 때문에 고온인장, 저주기 피로측정 등의 기계적 성질이 동시에 요구되며, 이들 특성은 단조공정변수 및 후열처리 등에 의해 크게 바뀌게 된다. 본 연구에서는 Alloy 718을 이용하여 가스터빈 디스크 제조할 경우 공정변수로서 단조온도, 변형속도 등에 의한 조직이 변화와 이에 따른 기계적 특성의 변화를 다루었다. 특히 이 합금에서 결정립크기는 고온 기계적 성질을 결정하는 중요한 변수로 작용하는데, 2단계 단조공정시 재결정에 의한 조직의 변화를 전산모사 방법에 의해 해석하고 그 결과를 조직 관찰을 통해 검증하였다.