Investigation Of Ignition Transinet In Dual-Trust Rocket Motors With Aft-End Igniter

Due to the complex phenomena embedded in ignition process, ignition transientanalysis is a difficult problem for solid rocket motor research. Focusing on DTRMswith an aft-end igniter, this dissertation systematically investigates its ignition transientprocess in the aspects of theoretical model establishment of heat transfer on grainsurface, identification of unknown parameters for the developed heat transfer model,gas filling process in the chamber and flame spreading along grain surface, ignitiontransient characteristics,structural integrityof propellant grain duringignition transient,and aft-end igniter design based on theoretical analysis and numerical simulation. Thetechnical approach to improve the performance of DTRMs with an aft-end igniter isexplored,thusthe results wouldprovidethetheoreticalas wellastechnicalguidance fortheoptimizationdesignofDTRMswithanaft-endigniter.An improved heat transfer model is developed to describe heat transfer on grainsurface in DTRMs with an aft-end igniter. Based on the traditional convection andradiation heat transfer model, an additional flame radiation model which considers theflame radiation fromadjacent ignited area is incorporated to describe theheat flux overtheunignitedgrainsurface.Ageneration algorithm isadaptedtoapplyonparameteridentificationfor transientignition model of solid rocket motor. Using the improved algorithm, the unknownparametersoftheheattransfermodelaresuccessfullyidentified.Several tactics,suchasutilizing Latin hypercube sampling to generate inherit population, revising theindividualitycomparison rules, and introducingsomeproportion of unfeasible solutionsinto feasible domain, are employed to improve the optimization ability and to enhancetheconvergence speedofthealgorithm.Transient characteristics during ignition process in DTRMs with an aft-end igniterare investigated. Subsequently, the technical methods to enhance the ignitionperformance are discussed. The transient flow characteristics during gas filling processare predicted and the flame spreading process is described in detail. The variation ofignition performance along with various operation parameters such as igniter powdermass,propellantproperties,seal's openingpressure,initialtemperature andthewidthofthe slot between the boosting grain and the cruisinggrain during ignition transient areobtained through numerical simulation. Based on the calculation results, the reasonablevaluerangeforigniterpowdermassandseal's openingpressureisprovided.Response characteristics of the grain during pressurization are investigated. Thestructural integrity of solid propellant grain during ignition transient is analyzed.Response characteristics of the grain exposed to transient uniform pressure load andnon-uniform pressure load are compared. The relationships between stress and strain, strain rate and loading rate, pressure load and strain during pressurization are alsostudiedseparately.A method for igniter powder mass calculation is proposed. In comparison withtraditional empiricalpowdermass formulas, thenewmethod whichis establishedbasedon the solid phase ignition theory and heat transfer theory presents more profoundtheory basis and higher integrity of the design variables by introducing the generalrequirement of ignition delay as inputs. As a result, wider application and highercalculationprecisionisobservedforthenewmethod.