The mathematical model of general system instability in a liquid jet engine is obtained, taking into account the nonstationarity of the outflow of combustion products from the jet nozzle. The peculiarity of the variation of self-oscillations of vibration combustion is established depending on the geometric structure of the hydraulic characteristic of the jet nozzle. The possibility of decreasing the amplitude or complete suppression of the considered oscillations is justified. The theoretical description of vibrational combustion is represented by a system of equations for the mechanics of gases, in which the energy equation is reduced to the pressure characteristic of the heat supply. This made it possible to establish previously unknown mechanisms of this phenomenon caused by the formation of an ascending (unstable) branch on the pressure characteristic of the heat supply. Using the numerical integration of the obtained equations of the mathematical model of the self-oscillations under consideration, the nature of their dependence on the delay in combustion of fuel for various geometric types as a pressure characteristic of the heat supply as well as the hydraulic characteristics of the jet nozzle is established. The nature of the deformation of the limiting cycles of self-oscillations in the combustion chamber of LPRE is established, when mechanisms of both intra-chamber instability and flow from the jet nozzle are manifested. Using numerical simulation, an increase in the limiting cycle of self-oscillations is established with an increase in the delay time of combustion of fuel when the stationary regime is on a stable monotonically decreasing branch of the pressure characteristic of the heat supply. The expression for the critical delay time of fuel combustion is analytically obtained as a function of the acoustic parameters of the combustion chamber, its pressure characteristic and the hydraulic characteristic of the reactive nozzle. The obtained expression makes it possible to quantify the influence of these parameters on the boundary of the stability region of the stationary regime.
MATHEMATICAL MODELING OF SELF-OSCILLATIONS IN A LIQUID JET ENGINE DUE TO THE NONSTATIONARY OUTFLOW OF GASES FROM A REACTIVE NOZZLE
2017
Aufsatz (Zeitschrift)
Elektronische Ressource
Unbekannt
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