Development of a method for selecting a cruising mode and engine control program of a ramjet aircraft

For supersonic cruising, combined power plants can be used, in which a gas turbine engine reaches the cruising mode, and a ramjet is used for cruising. Supersonic transoceanic flights are characterized by a long cruising segment, which is decisive in terms of required fuel mass. Therefore, the selection of cruising and engine operation parameters is an important task. As a rule, when selecting the cruising mode, the range parameter is used, which depends on the flight and engine operation modes. To take into account the influence of the ramjet operating mode on the range parameter, dimensionless relationships of engine parameters with control factors were obtained. Using the obtained relationships together with the equations of aircraft motion in steady horizontal flight, it is shown that the values of the engine control factors and the range parameter do not change at the altitudes of 11...20 km. This made it possible to conclude that the range parameter can be increased only by selecting the cruising and engine parameters that provide the minimum specific fuel consumption. The variable cruising parameters are speed and initial altitude. A method for selecting the cruising and ramjet operation parameters was developed, based on the analysis of the relationship between the range parameter and the flight speed and initial altitude at the most advantageous values of the engine control factors. The obtained relationships allow selecting the cruising parameters and the engine operating mode, taking into account the restrictions. It is shown that the specific fuel consumption decreases by 0...30 %, depending on the engine operating mode, when the control program is optimize