Zhivotov N.P.   Abashev V.M.   Tretyakov P.K.   Eremkin I.V.  

The theoretical and practical aspects of paste-fuel fuels using in rocket engines

Reporter: Zhivotov N.P.

Classical solid fuels have almost exhausted the possibilities of increasing their characteristics, both energy and constructive. The so-called paste-like fuels can become an alternative. These fuels were high-filled (up to 80%) paste-like suspension on the basis of an "active" vigorous liquid binder filled with a mineral oxidizer and high-energy additives, for example aluminum, boron and the like. They can maintain a viscous-fluid state at temperatures from +70 to -60 degrees. The viscosity of these compounds at room temperature was several thousand Pa * s. High combustion rates (up to several hundred mm / s) allow the use of pasty fuel for end charges that combust layer by layer. Together with the high density, all these properties of pasty fuel make it possible to obtain significant advantages for rocket engines of certain classes in comparison with conventional solid rocket Engines. Such areas include engines with short operating times (less than 1 second), multi-mode and multi-pulse engines, soft landing engines for return objects and auxiliary launch vehicle engines, starting and accelerating engines, fire extinguishers and many others.
Achievements that are realized in paste-like fuels became possible with the creation of active, self-extinguishing liquid-viscous binders, which fundamentally change the mechanism of burning and ignition of fuels. In the charges of pasty fuel, physical methods for increasing the burning rate are possible, for example, using reinforcing elements in the form of cylinders made of materials with high thermal conductivity. The combustion mechanisms of pasty fuel, especially with reinforcing elements, are not fully understood and require additional research.
Paste-like fuel is a hydroplastic in a viscous-flowing state, therefore, for the pasty fuel charge there are no requirements for the strength of the charge, moreover, the paste-like fuel is not afraid of high pressure, and can operate at pressures of 300 ... 500 MPa without the transition of combustion into detonation.
However, the use of pasty fuel has its own characteristics. First, its fluidity in the free state and a high coefficient of linear expansion, that 2-5 times its value for mixed rocket fuels. If the first feature is easily compensated by constructive methods, for example by installing a sealing mobile diaphragm in the combustion chamber, then to release stresses in the pasty fuel mass and to eliminate stratifications in the charge, it is necessary to create a special system - the system for compensating the thermal shrinkage of pasty fuel. Existing methods of calculation of compensation of thermal shrinkage are built on approximation dependencies for a specific type of paste-like fuel and are not General in nature. Creation of techniques that consider the majority of influencing factors, including operating conditions, rheological and physical-mechanical properties of pasty fuel, is the task of fundamental science.

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