Effect of the mode of combustion on the service life of the combustion chamber material

The effect of the characteristics of intrachamber combustion (the pressure and the temperature of combustion products) on the service life of the material of the combustion chamber of a thermal engine is examined. The problem is studied with the help of the Zhurkov kinetic approach based on model examples of spherical and cylindrical shells subjected to the action of cyclically varying pressure and temperature of the gas in the chamber. An analogy between the influence of stress and temperature on the service life of material is demonstrated. It is shown that periodic variations of the intrachamber characteristics can lead to an appreciable shortening of the service life of the shell in comparison with the service life at a constant pressure and temperature equal to the corresponding mean values. Thus, in the case of pressure and temperature variations (of the harmonic type), small in amplitude, the effect of the accelerated aging of the material per cycle of loading is proportional to the square of the amplitude of variations. In this case, a relative increase in the deterioration of material during one period of loading does not depend on the value of the period of loading. The problem of the effective medium stress with a periodically varying loading of random type is discussed. The theoretical results obtained are illustrated for aluminum shells and other construction materials, as examples.