Combustion instability suppressant

Though the major components of double-base propellants are NG-NG or NG-TMETN, various additives such as plasticizers, burning rate modifiers, or combustion instability suppressants are needed. Table 4.11 shows the materials used to formulate double-base propellants. 

High-energy additive Combustion instability suppressant HCl suppressant... 

Burning rate catalyst modifier Combustion instability suppressant Opacifier ... 

Lee, J. G., and D. A. Santavicca. 1998. Application of flame evolution imaging to the optimization of an active control system for suppressing combustion instability. 27th Symposium (International) on Combustion Proceedings. Pittsburgh, PA The Combustion Institute. 

Extensive reviews of active instability suppression techniques are found in McManus et al. [18] and Candel [19]. Also, Zinn and Neumeier [20] provide an overview of research and developmental needs for practical applications. Most of the previous studies have used actuators impractical in liquid-fueled systems, such as loudspeakers that impose acoustic perturbations on gaseous flow. The major emphasis in the present study was to establish active instability suppression using liquid-fuel injection. According to Rayleigh s criterion [21, 22], combustion-acoustics interaction can be used to damp the undesirable oscillations provided that pressure fluctuations p and heat release fluctuations q satisfy the proper phase relation such that... 

To demonstrate liquid-fueled active combustion control, instability suppression experiments were performed under several conditions. Figure 21.6 shows the dump combustor set-up used in the demonstration experiments. Three configurations in which naturally unstable oscillations were observed are shown. Table 21.1 lists the specific flow conditions where instabilities occurred. The case number in the table corresponds to the combustor configuration used. 

The present study was conducted in an effort to better understand ACC mechanisms and to design practical ACC based on pulsed liquid-fuel injection suitable for propulsion devices. The controller utilized a simple fixed phase-delay approach that has been studied previously, but the direct liquid-fuel injection and the novel use of vortex-droplet interaction made the present study unique. The demonstration experiment in a 102-millimeter dump combustor showed that combustion instabilities can be successfully suppressed using properly designed pulsed liquid-fuel injection. 

Poinsot, T., F. Bourienne, S. Candel, and E. Esposito. 1989. Suppression of combustion instabilities by active control. J. Propulsion Power 5 14-20. 

The use of feedback-control techniques to modulate combustion processes in propulsion systems has recently received extensive attention [1-3]. Most of the previous studies involved direct implementation of existing control methods designed for mechanical devices, with very limited effort devoted to the treatment of model and parametric uncertainties commonly associated with practical combustion problems. It is well established that the intrinsic coupling between flow oscillations and transient combustion responses prohibits detailed and precise modeling of the various phenomena in a combustion chamber, and, as such, the model may not accommodate all the essential processes involved due to the physical assumptions and mathematical approximations employed. The present effort attempts to develop a robust feedback controller for suppressing combustion instabilities in propulsion systems. Special attention is given to the treatment of model uncertainties. Various issues related to plant... 

Fig. 13.25 Combustion instability is suppressed as the concentration of aluminum particles is increased (the average designed chamber pressure is 4.5 MPa).

It is evident that the standing pressure wave in a rocket motor is suppressed by solid particles in the free volume of the combustion chamber. The effect of the pressure wave damping is dependent on the concentration of the solid particles, and the size of the particles is determined by the nature of the pressure wave, such as the frequency of the oscillation and the pressure level, as well as the properties of the combustion gases. Fig. 13.25 shows the results of combustion tests to determine the effective mass fraction of Al particles. When the propellant grain without Al particles is burned, there is breakdown due to the combustion instability. When... 

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