Study On Cylindrical Gain Generator Assembly For Continuous Wave HF Chemical Laser

Output power of cylindrical HF chemical laser is the highest among continuouswave lasers in the world at present.As a vital component in cylindrical chemical laser,cylindrical gain generator assembly is primary investigation object in this paper. Theresearchmethodinvolvesnumericalsimulation, theoreticaldesignandexperiment.1D analysis method of HF chemical laser combustor was presented by combiningminimumGibbs'freeenergymethodandmassfluxconservationprinciple.MolefluxofFatominnozzlethroatsectionasanewparameterthatcanbeusedtoexpress yield ofFatom was deduced. The effect of changing fuels'mass flow rates on combustor'scharacteristics for NF3-D2-He reaction system was calculated using this method. Thechangingtendencyofcombustor'spressureisinagreementwith experimentalresult.Distributionflowpipeline,injector andcombustor,primarynozzle,couplingregionand optical cavity in gain generator assembly were calculated and analyzed using 3Dnumerical simulation theoretical model of cylindrical gain generator assembly for HFchemical laser. The effect of hot wall boundary on flow field characteristics ofdistribution flow pipeline in primary nozzle under conditions of single end or doubleends supplygas wasanalyzed. Comparinglinear distribution flow pipeline with annulardistribution flow pipeline,it was shown that the annular distribution flow pipeline withbranch pipelinesconnected with outer circular arc of general pipeline is of advantage todistributing uniformly branch pipelines'gas flows most. Chemical reactions ofcombustor were described by integrating Eddy-Dissipation Model and Arrhenius ratecoefficients. Thecoldandreact flowfieldcharacteristics oftriplet impingement injectorand combustor for Fuel-Oxidizer-Fuel (F-O-F) or Oxidizer-Fuel-Oxidizer (O-F-O)triplet arrangement were simulated. The degree of F2 dissociation in combustor exitplane for O-F-O triplet arrangement is higher by 13.5% as compared with F-O-F tripletarrangement under conditions of specified compositions proportioning and combustorcharacteristic length. Experimental result confirms above-mentioned conclusion. Threekinds of primary nozzles with different convergent section curves were calculated. Thenumerical simulation result shows that total pressure loss of gas flow in primarynozzleusing arc-line composite curve as convergent section curve is higher a little, butrecombination proportion of F-atom in nozzle exit plane for this convergent sectioncurve is lower than for some curves else. And this nozzle is convenient to machiningand suitable touse in experiments. The flow filed of coupling region and optical cavityfor annular HYLTE nozzle was numerically simulated considering heat energy loss ofcombustor wall. The small signal gain coefficient distribution in optical cavity wascalculated bypost processingof flow field data. The experiments of measuringoutputspectrum and moving optical axis demonstrate that, the computational model The above-mentioned research results provide important guidance for the design andexperimentofcylindricalgaingeneratorassembly.The experimental facility of 1/4 cylindrical gain generator assembly was designedand built. The computational method of input fuels'mass flow rates was described indetail. Flow filed characteristics of Venturi nozzle under conditions of different backpressures were studied using numerical simulation method. The computing resultsprovide reference to reasonable design and accurate monitor of Venturi nozzle. A novelannular HYLTE nozzle structure including four inner gas passages is obtained byfurther simplifying existing annular nozzle structures. The fabricating methods andtechnologicalprocessesofannularinjectorandannularHYLTEnozzle wereconfirmed.A series of lasing experiments of laser system was performed. When each inputfuel's mass flow rate was set to designed value,output power of laser was about 60 W.Intemperature and pressurecurves of combustor measured in experiment, there are allclimbing segments, which are similar to Alpha HL911-3 test results. The differencebetween measured values and computed values for static pressure of combustor iswithin1%.The characteristicofcircumferentialdivergenceincylindricalgaingeneratorassembly lowers the pressure of optical cavity remarkably. The measured value ofoptical cavity pressure is merely about 0.5 kPa. The experimental results of adjustingfuels'mass flow rates show that, as compare with changing mass flow rate of onwardHe,changingmassflowrateofbackwardHecanacquiremuchhigheroutputpowerandbetter ignition stability. To validate effective formation of cylindrical gain region, thelasing experiments were performed for 3 couples of power extraction apertures. Theexperimental results demonstratethat laseroutput poweris detectedwitheffect for eachcoupleofpowerextractionaperturesandcylindricalgainregionhasgenerated.Theexperimental datashowthat,thedesignof experimental facilityis rational andits working parameters behave properly during operating. The devices can maintaingood sealing and mechanical properties in high temperature and strong corrosiveenvironment.