Nonlinear Stability Testing of Full-Scale Tactical Motors

Blomshield, Fred S.; Mathes, H. B.; Crump, J. E.; Beiter, C. A.; Beckstead, M. W.

doi:10.2514/2.5192

Cited by 47 publications

(39 citation statements)

References 8 publications

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“…This implies that the tendency of a motor to become unstable often increases with time. 36,40,41,45,46,47,52 Referring to Figure 8, it can be seen that the magnitude of both driving alphas (those that are positive) and damping alphas (those that are negative) decrease in magnitude as the motor burns to completion. This can be explained by examining the following expression:…”

Section: Stability Observationsmentioning

confidence: 99%

“…40,41,45,46,52,53 A star aft geometry is an example. The driving mechanisms of velocity coupling and distributed combustion have terms like the following:…”

Section: Stability Observationsmentioning

confidence: 99%

“…Furthermore, a stable motor will tend to be more susceptible to non-linear pulsed instability. 40,45,46,52,59,60,61 An example of this is shown in Figure 10. This plot presents the ballistic pressure traces for three identical motors except for nozzle throat sizes which modify the motor chamber pressure.…”

mentioning

confidence: 99%

“…The grain design should not have an abundance of burning area in the aft end. 40,41,45,46,52,53 This can increase driving due to velocity coupling and distributed combustion for metallized propellants. This can also decrease nozzle damping if more of the aft case is exposed as the motor burns.…”

mentioning

confidence: 99%

“…In general, as mean motor pressure is increased, other factors remaining the same, a motor will tend to become less stable. 40,41,45,46,52,55,59 Raising mean motor pressure reduces the margin of stability due to decreases in both nozzle and flow turning losses, see Figure 7. Furthermore, a stable motor will tend to be more susceptible to non-linear pulsed instability.…”

mentioning

confidence: 99%

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Lessons Learned In Solid Rocket Combustion Instability

Blomshield¹

2007

43rd AIAA/ASME/SAE/ASEE Joint Propulsion Conference &Amp;amp; Exhibit

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Over the last 60 years, a considerable amount of time and money has been spent improving our understanding of combustion instability in solid rocket propulsion systems. Over this period, significant knowledge has been accumulated that can influence the acoustic stability of solid propulsive systems. Unfortunately, many of these lessons learned about combustion instability remain the knowledge of a select few in government and industry who work with combustion instability on a daily basis. This paper attempts to organize many of these "rules of thumb" that propellant formulators and motor designers need to be aware of in order to minimize the chances of combustion instability. In addition, several mathematical relationships are presented which can be used to predict the frequency of potential acoustic modes and determine resultant thrust oscillations produced by acoustic oscillations. Also included are some key fundamental equations which can be used to gain insight into combustion instability in rocket motor systems and there is a short section on motor instrumentation. This paper is not an attempt to be an exhaustive study into combustion instability, but rather, will attempt to list in a clear fashion some of the more important lessons learned and empirical observations of solid propellant combustion instability. This paper emphasizes composite propellants, but many observations apply to double base and composite modified double base propellants, as well.

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Section: Stability Observationsmentioning

confidence: 99%

“…40,41,45,46,52,53 A star aft geometry is an example. The driving mechanisms of velocity coupling and distributed combustion have terms like the following:…”

Section: Stability Observationsmentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

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Lessons Learned In Solid Rocket Combustion Instability

Blomshield¹

2007

43rd AIAA/ASME/SAE/ASEE Joint Propulsion Conference &Amp;amp; Exhibit

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Bifurcation to Limit Cycle Oscillations in Laminar Thermoacoustic Systems

Sujith

Pawar

2021

Springer Series in Synergetics

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In this chapter, we study the bifurcation characteristics of a laminar thermoacoustic system through the application of dynamical system theory. We restrict our discussions to two simple prototypes of real thermoacoustic systems (known as Rijke-type thermoacoustic systems): a horizontal Rijke tube with an electrical heater and a ducted premixed flame combustor, both having a laminar flow field. We describe the transition of a thermoacoustic system from a state of stable operation (called stable fixed point) to unstable operation (called stable limit cycle) on variation of any control parameter. First, we will present the dynamical transitions and characteristics of the dynamical states observed in laminar thermoacoustic systems in the absence of any stochastic background fluctuations in the flow field. Subsequently, we will study the effect of external stochastic perturbations on the occurrence of different dynamical transitions in such systems. These investigations performed on simple laminar thermoacoustic systems can be considered as a baseline study before we attempt to understand the complex dynamics exhibited by turbulent thermoacoustic systems in Chap. 6.As mentioned in Chap. 1, the occurrence of thermoacoustic instability has been a concern for most practical combustion systems used in power generating units and propulsion engines. Traditionally, both linear and nonlinear methodologies have been used to explain the occurrence and the characteristics of thermoacoustic oscillations observed in such systems. In linear analysis, the equations describing flame-acoustic interactions are subjected to small amplitude perturbations for calculating the eigenvalues [12]. When all the eigenvalues are negative, the system is considered to be linearly stable, and when one of the eigenvalues is positive, the system is considered to be linearly unstable. For a linearly unstable system, an infinitesimally small perturbation introduced in the system grows in time and asymptotically approaches another stable state that is different from the initial state. As seen in Chap. 2, for the case of subcritical Hopf bifurcation, a finite amplitude perturbation (or initial condition) in the regime of bistability (hysteresis) can alter

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Modeling and analysis of triggering pulse to thermoacoustic instability in an end-burning-grain model solid rocket motor

Wang

2019

Aerospace Science and Technology

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Nonlinear Stability Testing of Full-Scale Tactical Motors

Cited by 47 publications

References 8 publications

Lessons Learned In Solid Rocket Combustion Instability

Lessons Learned In Solid Rocket Combustion Instability

Bifurcation to Limit Cycle Oscillations in Laminar Thermoacoustic Systems

Modeling and analysis of triggering pulse to thermoacoustic instability in an end-burning-grain model solid rocket motor

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