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Characteristics of flow and thrust variations in a jet engine with a variable area nozzle
박준호,손채훈 대한기계학회 2015 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.29 No.11
A numerical analysis of the internal flow field in an exhaust converging-diverging nozzle of a jet engine has been carried out. Variablearea nozzle is required in a jet engine for optimal expansion and adjusting back pressure in the engine when the afterburner is operated. Steady-state and transient analyses are carried out for each condition with and without afterburner operation and as a function of the locationof the nozzle flap. For a baseline power condition, mixture composition of combustion products is calculated by the chemical equilibriumanalysis and the cold flow analysis is carried out based on the mixture composition. For the afterburner operating condition, additionalfuel is injected from the inlet boundary and numerical analyses of reactive flow fields are carried out. With variable area nozzleadopted, combustion fields are variable in time, leading to periodically variable thrust. When nozzle flap is in a closed state, nozzle internalpressure and temperature are increased upon the afterburner operation and moment of a force at the pivot point is increased as well. These undesirable phenomena can be solved by control of a variable area nozzle. And, thrust level is also maximized by nozzle variation. During nozzle variation, unsteadiness effect is observed because of response lag of internal flow to nozzle variation. Both the designpressure and the optimum expansion of the nozzle can be attained by adopting the independent operation of a variable area nozzle.
가변노즐의 변위가 제트 엔진의 유동 및 추력특성에 미치는 영향에 관한 수치해석
박준호(Junho Park),손채훈(Chae Hoon Sohn),박동창(Dong Chang Park) 한국추진공학회 2013 한국추진공학회지 Vol.17 No.5
Variable area nozzle, where both throat and exit area vary, is required for optimal expansion and optimal nozzle shape upon operation of after-burner. Steady-state and transient analyses are carried out for each condition with and without afterburner operation and as a function of the location of the nozzle flap. Effects of that nozzle displacement on flow and thrust characteristics are analyzed from numerical results. With variable area nozzle adopted, the combustion field is variable in time, leading to periodically variable thrust. For off-design conditions, flow separation shows up due to over expansion at the flap tips and shock wave does in the nozzle due to under expansion. The undesirable phenomena can be solved by control of variable area nozzle.
박동창(Dongchang Park),이상연(Sangyoun Lee) 한국추진공학회 2014 한국추진공학회 학술대회논문집 Vol.2014 No.12
가변노즐은 다양한 고도에서 비행체의 효율을 향상시키기 위하여 사용된다. 가변노즐의 효율을 더욱 향상시키기 위해서는 노즐 내부 유로 형상을 최적화할 필요가 있다. 본 논문에서는 Vitoshinsky 노즐과 이중원호법을 이용하여 가변노즐의 내부유로 형상을 설계하는 실제적인 방법을 소개한다. 본 기법을 이용하여 가변노즐의 플랩 작동으로 인해 형성되는 몇 개의 노즐 내부 유로 형상을 평가하였다. Variable nozzles are used to enhance the effectiveness of aircraft at various altitudes. The optimization of internal contour of variable nozzle is needed to enhance the effectiveness of variable nozzle. In this research, a practical method to design nozzle profile is introduced . The method consists of Vitoshinsky nozzle and a two arc method. The method was used to validate several contours of variable nozzle due to the flap movement.