Studying specifics of strained state of a box-shape channel of ramjet engine

Аuthors

Khomovskii Y. N.

Moscow Aviation Institute (National Research University), 4, Volokolamskoe shosse, Moscow, А-80, GSP-3, 125993, Russia

e-mail: yariksp@mail.ru

Abstract

In hypersonic ramjet engines of underslung type the structural forms of air intake units, transition parts (the so-called insulators), through which the air is supplied to the combustion chamber and combustion chambers themselves represent thin-walled channels of rectangular or circular cross-sections. The airflow duct of an American X-51 hypersonic rocket and, particularly, its insulator is a consistent combination of channels of this shape.

The thin-walled structural elements of box, oval and cylindrical shape, forming the insulator sections, are exposed mainly to the pressure drops and temperature gradients. The stress state of such elements has its own specifics, and no sufficient information on it is available in the known literature sources. It relates, in the first place, to the inner corners. A significant concentration of stresses may be supposed in these places. Instead of a real insulator, let us consider the stressed state of a boxed-shape channel on the example of its six cross-sections.

The calculations were performed separately for the cases of loading by temperature gradient, pressure drop and a joint impact of these loads. The impact of R radius (R = 1; 3; 5; 13; 21; 28,5 mm) in the inner corners of models on the stress concentration factor was considered for each model.

Analyzing the obtained results, we can draw conclusions that the stresses in the corners of the models arising from the influence of pressure are very sensitive to the inner radius (in contrast to the temperature stresses). This may indicate the feasibility of separate consideration of these factors in the calculation of stress-strain state. Separate evaluation of stress concentration factors along the x and y axes may be handy for evaluating the strength of shells made of carbon-carbon composite materials with a fiber structure.

Keywords:

combustion chamber, stress concentration

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