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Design of a test setup for altitude simulation

Aydoğdu, Ataman
Altitude simulation testing is an important concept in missile systems, especially in terms of aerothermal ground testing and high speed air breathing engine free-jet testing. Those tests of the missile systems at supersonic speeds need High Altitude Test System (HATS) which simulates Mach number, total pressure and total temperature of the flow on the test article mounted in the test chamber by using free-jet nozzle. To start the free-jet nozzle operation which simulates high altitude conditions, test chamber pressure should be lowered. One of the mostly used methods to reduce the static pressure in the test chamber is ejector systems. In this thesis, performance of an ejector system is investigated together with the free jet nozzle and test chamber by using numerical and experimental methods. Primarily, ejector system and test section design are performed separately by ‘Design by Analysis’ method based on Computational Fluid Dynamics (CFD) analyses and optimization algorithms. Nondimensional ejector system and test section geometry are determined. Then, numerical results of ejector system and test section analyses are compared with the numerical results of combined HATS analysis model with 2, 2.5 and 3 Mach free-jet nozzles. Good aggrement between the results is indicated. After that, by using the nondimensional ejector system and test section geometry, experimental setup is designed, manufactured and established in TÜBİTAK-SAGE. Then, an experimental study is performed to assess the numerical solutions. The effect of the length to diameter ratio (L/D) of ejector diffuser, ejector nozzle exit plane (NXP) location and entrainment ratio (ER) on the pressure distribution along experimental setup and free-jet nozzle starting condition are investigated in detail. At design condition, vacuum pressure value is calculated as 26754 Pa in numerical solution and measured as 30794 Pa in experiment, test chamber pressure value is calculated as 7563 Pa in numerical solution and measured as 7437 Pa in experiment. Comparisons of numerical data with experimental data show a good fit in vacuum pressure and test chamber pressure (within 13% for vacuum pressure and 2% for test chamber pressure).