Engineering Design And Related Studies On The Free Vortex Aerodynamic Windows Of High Energy Lasers

Because of the intrinsic fractional absorption of the laser energy with the conventional solid output windows for high energy lasers (HEL),the optical quality will be degraded,or the overall HEL system cannot run at all when the laser energy are far higher,or the system runs longer time. So the conventional solid windows have been becoming the threshold of the laser energy's promotion and the optical quality's improvements.To solve the above-mentioned problem of HEL's output solid windows the concept of aerodynamic windows(abbr. ADW) is proposed according as the property of gas,i.e. selective absorption of electromagnetic wave. ADW employing gases which don't absorb the laser energy can form a gas urtain" whose pressure of the two sides is equal to the low pressure of laser cavity and the ambient circumstance pressure respectively so it can isolate the higher pressure ambient air from entrancing into the laser cavity and maintain the HEL's running normally.First this paper proposes the method of evaluating ADW's properties including the sealing capability,optical quality,mass flow rate of working gas and so on. It proposes and founds the concept of the relative mass flow rate mr of ADW. Calculating results mr of various aerodynamic windows proposed years ago show that the free-vortex aerodynamic window(abbr.FADW) has the apparent virtues. So we choose the FADW to study and design for taking the place of the solid windows of HEL.A complete set of the method designing FADW is founded in this paper. The flow field of FADW is very complicated,especially in the free vortex jet zone. So the method is according to the ideal flow,including the design of the asymmetric supersonic laval nozzle and the diffuser.The reasonability of FADW designing should be proved experimentally,so this paper studies the various running properties of the FADW whose output window's size is 30mmX30mm experimentally. It uses the methods of the far-field beam profilemeasurement,the lateral shearing interferometer(LSI) and the Hartmann-Shack wavefront sensing to measure the window's optical qualities when the FADW works in the situations of different inlet total gas pressure. And the paper analyzes the physical reasons that the supersonic flow of FADW degrades the optical quality. And the structure of free-vortex jet of FADW is studied using the methods of shadowgraph and LSI,respectively. A prototype of FADW 90mm x 30mm with the same wall curve of the above FADW is manufactured,and its properties are studied preliminarily.To study the engineering application of FADW a testing free-vortex aerodynamic window system whose structure size is changeable is designed and manufactured,and the system can be used to study the method of FADW optimizing design. This paper studies the diffuser's influence on the FADW's running properties experimentally including the inner wall and outer wall of diffuser and the backpressure of the diffuser. To prevent the gas of FADW from leaking into the laser cavity because of the effect of layer and turbulence the leak-proof flakes are designed. First the method of the leak-proof flake design is studied and then its influence on the properties of FADW is studied experimentally. Through the above various experiments study on FADW's properties many value results are obtained. These results can provide the theoretical and engineering reference to optimize the free-vortex aerodynamic window in the future.And then experiments of compensation for the aberrant wave front caused by FADW's free-vortex flow are studied using our 37-elements adaptive optical system. It gives the related explanations of the experimental results and points out the further studying direction in this field.At last the paper calculates and discusses the overall flow of the FADW using the finite volume method(FVM). The calculation results show that the adopted methods are reasonable.