Analysis of Gas-Dynamic Effects in Explosively Actuated Valves

Abstract

A quasi-one-dimensional model is formulated to assess unsteady gas dynamics occurring within axisymmetric explosively actuated valves. The model accounts for pressure-dependent explosive burn within an actuator, compressible product-gas flow through a narrow port connecting the actuator to a gas expansion chamber, and piston motion due to the combined effects of gas-dynamic forces within the expansion chamber and structural deformation forces between the piston and valve bore. The initial boundary-value problem is posed in terms of generalized coordinates to facilitate numerical computations on a domain that volumetrically expands due to combustionandpistonmotion.Predictionsforabaselineconfigurationthatisrepresentative ofaconventionalvalve indicate that gas-dynamic waves do not result in irregular operation, implying that spatially homogeneous models may be adequate for describing its performance. However, small changes in valve geometry and explosive mass can produce large variations in gas-dynamic fields that significantly affect both the magnitude and frequency of the pyrotechnic shock transmitted to the valve’s supporting structure. Port diameter is shown to control the rates of explosive energy release andacoustic energy transport, which can significantly affect pistonmotion andstroke time.