Theoretic And Experimental Research On Thrust Misalignment Of Laval Nozzle

Thrust misalignment caused by gas flow is one of the main reasons for uncontroled-rocket dispersion. This dissertation researches the rule of side thrust and misalignment moment according to Laval nozzle of different type inner profiles. Integrated with experimental research, zero-thrust-misalignment (ZTM) nozzle designing method is enriched.Comprehensive theoretic study on thrust-misalignment characteristic of rocket engine nozzle has been carried out, and unsymmetrical flow computation in nozzle is basic theoretic. Computational results based on method of small perturbations, method of characteristics,and CFD shows that side thrust curves oscillate and reduce along the nozzle axis, their zero point positions will not be affected by different intensity of inlet disturbance, and prove ZTM existent. CFD simulations receive transonic3D flow fields in nozzles at the asymmetry situations of inlet velocity, total pressure, and total temperature, results show that different disturbance sources get different side thrust curves and their zero points.Researches on effect caused by nozzle stagnation parameters and propellant gas parameters show that small asymmetry of inlet total pressure can lead to significant side thrust, and its curve is different from other disturbances. Gas parameters, especially ratio of specific heats, greatly affects nozzle thrust misalignment. This factor should been paid attention in further research and design of ZTM.Structural schemes of experimental device for nozzle thrust misalignment have been analyzed, and test method of side thrust zero points has been optimized.6-force-components test bed is the basic equipment, has been studied. It is complicated, and its accuracy affected by many factors.Combining theoretic researches and experiments, design principle, design process, and design means of ZTM has been consummated. Strategy of theoretical computation in ZTM design is expressed:method of small perturbations is suitable for conical nozzle of small expansion angle; Method of characteristics fits conical nozzle of large expansion angle, parabola nozzle, and dual-arc nozzle; CFD method is suitable for dissymmetrical fluid field study and final design project optimization. ZTM can been designed from scratch or modified from normal nozzle, their processes are compatible. Example of ZTM design has twice shoot intensity than the one before modified, proves design method is correct.