Volume-to-Surface Transformations of Rocket Stability Integrals

Fischbach, Sean R.; Flandro, Gary A.; Majdalani, Joseph

doi:10.2514/6.2004-4053

Cited by 6 publications

(7 citation statements)

References 18 publications

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“…2003 Flandro and Majdalani introduced additional linear correction terms, including terms involving the pseudopressure, the pressure variation due to vortical waves. 9 The resulting new integrals were reduced to surface integral form, and evaluated for magnitude in comparison to M b , the burning rate of the propellant. Two significant terms were identified: a vortical and a viscous correction.…”

Section: Evolution Of Linear Combution Stability Methodologiesmentioning

confidence: 99%

Improvements to the Linear Standard Stability Prediction Program (SSP)

French

Flandro

Majdalani

2004

40th AIAA/ASME/SAE/ASEE Joint Propulsion Conference and Exhibit

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Despite many decades of study, new solid rocket motors systems frequently experience unsteady gas motions and associated motor vibrations. This phenomenon most often occurs when the acoustic modes of the combustion chamber couple with combustion/flow processes. Current linear models of the sort used in the Standard Stability Prediction (SSP) code are designed to predict the tendency for a solid rocket motor to become unstable, but they do not provide any information on the severity of the instability (usually measured by the limit cycle amplitude of the oscillations) or on the triggerability (the tendency of an otherwise stable system to oscillate when pulsed with a sufficiently large disturbance) of the system. A goal of our present work is to build nonlinear capability into the the SSP tools. Success in incorporating useful nonlinear capabilities depends on a sufficiently complete and physically correct linear model. Accordingly, Software and Engineering Associates, Inc., has undertaken major improvements in the linear stability analysis and associated capabilities of the Solid Performance Program (SPP). These improvements support the development of new nonlinear capabilities to predict the oscillating pressure limit cycle amplitude, triggering and the DC pressure shift, the latter of which is often the most important threat to the rocket motor system resulting from combustion oscillations. In this paper, we focus on the recent additions and improvements to the linear SSP module. These include major improvement to the linkage between the rocket design code and SSP, and the inclusion of rotational flow effects that allow the satisfaction of key boundary conditions in the unsteady flow field solutions. The enhanced capability of the SSP is demonstrated by comparing the modified code to previous analyses for several solid rocket motors covering a wide range of typical design characteristics. Examples include systems predicted to be stable by earlier versions of the SSP code that were in fact inherently unstable. The improved linear code yields results which better fit the experimental findings. The analytic approaches of Culick 2 and Flandro 3-4 for modeling combustion stability have been evaluated previously. 5 An underlying similarity between these approaches is their reliance on the linear stability analysis. If

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Section: Evolution Of Linear Combution Stability Methodologiesmentioning

confidence: 99%

Improvements to the Linear Standard Stability Prediction Program (SSP)

French

Flandro

Majdalani

2004

40th AIAA/ASME/SAE/ASEE Joint Propulsion Conference and Exhibit

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“…This work involves the calculation of minimum 11 growth rate terms that arise in the dynamics of an oscillating complex flow. Thus, we have converted these volume stability integrals into more amenable surface forms [6,7,8]. The flow field properties are more accurately defined on the motor surface boundaries and allow a more precise assessment of the motor propensity for instabilities.…”

Section: I4 the Influence Of The Initial Grain Temperature On The Nomentioning

confidence: 99%

“…4, 5 and 6). Evaluations were done using the corrected energy normalization value, [7,8,9], and one can appreciate that it is a more comprehensive method with an estimated greater accuracy. All the results correspond to a linearly unstable system in the explored case of extreme negative initial temperatures.…”

Section: I4 the Influence Of The Initial Grain Temperature On The Nomentioning

confidence: 99%

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Effects of initial grain temperatures on homogeneous propellant rocket motor operation with special emphasis on combustion instability

Safta

Ion

2015

International Conference on Military Technologies (ICMT) 2015

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The purpose of this paper is to give an overview of our main experimental results on combustion instabilities and pressure oscillations in Double-Base (DB) homogeneous propellant grain rocket motors (SPRM-01, 02 and 03). We recorded some particular pressure-time traces, at extreme grain initial temperatures (223-233 K and 313-323 K), with significant perturbed pressure signal that was FFT analysed. On the basis of an improved mathematical model it was explored how the derived nonlinear pressure coupled response function, depending on time and frequency, behaves at extreme initial grain temperatures. Dynamic response of the propellant combustion under operating motor conditions was also investigated and the results were related to combustion stability and motor efficiency. The study model incorporates unsteady rotational sources and sinks in the acoustic energy assessment and thus a more precise formulation of the acoustic instability in SRM can be achieved. This method involves the calculation of minimum 11 growth rate terms that arise in the dynamics of an oscillating complex flow. The susceptibility of the tested motors with a DB propellant to get a significant perturbed working and to go unstable with pressure especially at extreme low initial grain temperatures has been conclusively emphasized and this risk has to be better evaluated.Keywords-combustion instability; Double-Base homogeneous solid propellant; unsteady burning rate; acoustic growth rate terms; pressure coupled response function.

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“…The summation of these ten stability integrals represents the exponential growth (or decay) of oscillatory energy within the combustion chamber. A study performed by Fischbach, Flandro and Majdalani 5 has successfully converted the ten volume integrals into more amenable surface forms. The outcome of that study is presented in Table 1.…”

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confidence: 99%