Numerical Studies on Flow Behavior of Composite Propellant Slurry During Vacuum Casting

: Rockets are powered by composite solid propellant, which is a heterogeneous system consisting of solid oxidizer and metallic fuel dispersed in a polymeric fuel binder matrix. The slurry casting technique under vacuum/ gravity condition is well-established for performing a different class of large sized case bonded rocket motors. During propellant casting, the (cid:192) ow rate of slurry is a very critical parameter as it affects the product quality. The casting rate is governed by suf (cid:191) cient degassing and viscosity buildup due to the progress of cure reaction. (cid:44) n the present study, casting rate and casting time have been numerically evaluated for (cid:191) xed and varying percentages of valve opening, different viscosity of slurry, and different pressure drop (cid:11) driving force (cid:12) . The velocity pro (cid:191) le of propellant slurry inside feeding pipe and valve has also been evaluated. (cid:41) urthermore, to get a (cid:192) awless grain and to predict the slurry casting rate, a microscopic analysis has been carried out to model the (cid:192) ow behaviour of composite propellant slurry, where the momentum conservation law has been applied to express the mathematical model in an analytical form. The resulting differential and algebraic equations have been solved numerically using MATLAB, computing software. The numerical analysis is useful for designing new casting set-up and for giving the idea of maximum casting rate, which is achievable for given casting set-up and rheological properties of propellant slurry.


P
Pressure drop N/m 2 V avg Average velocity m/s a Percentage opening of the valve % h Slurry height in the bowl m V Volume m 3

N Re
Reynolds number

INTRODUCTION
Composite propellants (CP) are the most important class of solid rocket propellant used in various missile programmes such as ammonium perchlorate (65 to 70%), a metallic fuel such as aluminum powder (15 to 20%), and a polymeric bindalong with certain isocyanate based curatives and process aids special precautions are taken in application of vacuum and on parameters like type of propellant, rheological behavior of Vacuum/gravity casting is the most widely adopted tech-lant slurry is gravitational force and vacuum inside casting

Slurry During Vacuum Casting
Bejoy Thiyyarkandy, Mukesh Jain, Ganesh Shankar Dombe, Mehilal*, Praveen Prakash Singh, Bikash Bhattacharya High Energy Materials Research Laboratory -Pune -India Abstract: Rockets are powered by composite solid propellant, which is a heterogeneous system consisting of solid oxidizer and metallic fuel dispersed in a polymeric fuel binder matrix.The slurry casting technique under vacuum/ gravity condition is well-established for performing a different class of large sized case bonded rocket motors.During propellant casting, the ow rate of slurry is a very critical parameter as it affects the product quality.The casting rate is governed by suf cient degassing and viscosity buildup due to the progress of cure reaction.n the present study, casting rate and casting time have been numerically evaluated for xed and varying percentages of valve opening, different viscosity of slurry, and different pressure drop driving force .The velocity pro le of propellant slurry inside feeding pipe and valve has also been evaluated.urthermore, to get a awless grain and to predict the slurry casting rate, a microscopic analysis has been carried out to model the ow behaviour of composite propellant slurry, where the momentum conservation law has been applied to express the mathematical model in an analytical form.The resulting differential and algebraic equations have been solved numerically using MATLAB, computing software.The numerical analysis is useful for designing new casting set-up and for giving the idea of maximum casting rate, which is achievable for given casting set-up and rheological properties of propellant slurry.

MATHEMATICAL MODELING
During the mathematical modeling, momentum balance dimension followed by the integration over the whole control for the mathematical modeling:

Slanted and straight pipe-I
nature of slurry with power law behavior, slurry velocity, where: P slanted pipe, cos as (Saleh, 2002):

Ball valve
x at a distance of x from the z is the radius of circular shell and r is the distance of shell from the centre of sphere: With no-slip boundary condition, xy = nite at x = R, it becomes:

Velocity distribution inside various components of casting system
propellant slurry is at the free surface of slurry inside the valve, and decreases towards the valve surface, whereas velocity of the of propellant slurry in the pipe after ball valve also indicates that rheological behavior of slurry, pot life of propellant, and et al Few studies on modeling and simulation of propellant casting during pressure casting was carried out by Dombe et al et al Dormaus et al the distribution prediction of solid particle constituents during et al have also used bidirectional X-ray penetration measurement and digital image analysis for estimation of propellant slurry During propellant processing, propellant formulations in propellant slurry, with different rheological properties (end path available for casting (web thickness) of propellant grain wide variety of propellant formulations, with different web rate with percentage opening of valve with different rheological tion of vacuum casting with % opening of control valve (ball valve), mathematical modeling and simulation of casting set up across various components of casting system and related In the following section, we have reported the results of in the valve is V = × vol age opening of the valve is , this volume will be / of Numerical Studies on Flow Behavior of Composite Propellant Slurry During Vacuum Casting through this pipe, consider a shell of slurry at a distance x from the centre of pipe having thickx r is the distance of shell from the centre ofModeling of slurry height in bowlSlurry height in the bowl is modeled using continuity the casting setup, by considering one surface as a free one of straight pipe after the ball valve: number for the propellant slurry during casting is calculated, which is of the order of 10 -3 Numerical Studies on Flow Behavior of Composite Propellant Slurry During Vacuum Casting viscosity on pressure drop and casting time found that as viscosity increases, casting time increases for In uence of percentage opening of valve on pressure drop CONCLUSIONS has been numerically modeled in terms of differential and overall pressure drop and the time taken by the slurry to casting system is useful in designing new casting setup and for attaining given casting rate for propellant slurry, with Flow Behavior of Composite Propellant Slurry During Vacuum Casting 203 J. Aerosp.Technol.Manag., São José dos Campos, Vol.4,No 2, pp.197-203, Apr.-Jun., 2012