Закономірності зміни оптимальних складу і параметрів силових установок з прямоточними контурами від швидкості надзвукового крейсерського польоту

Abstract

There are two aircraft concepts for transoceanic flights at supersonic speed. The first is the aircraft with moderate supersonic cruising speed M = 1.7...2.2, and the second is the aircraft with cruising speed M ≥ 3. Propulsion with a ramjet engine (ramjet) is preferable for high supersonic speeds. However, a ramjet has no starting thrust and is uneconomical at subsonic flight speeds. Combined propulsion with a turbojet duct for takeoff and a ramjet duct for supersonic cruise flight are used to overcome this contradiction. There are known propulsion with turboramjet engines, as well as various propulsion schemes with turbofan engines (afterburning and duct-burning ones), in which the outer contour together with the afterburner and nozzle can be considered the ramjet duct. When the turbojet duct is turned off, the operating process of such turbofan engines is practically the same as the ramjet, which allows using the advantages of a ramjet in supersonic cruise flight. Because flight at supersonic cruising speed can be provided by different propulsion compositions, the choosing problem of the composition and parameters of the propulsion for an aircraft with supersonic cruising speed is relevant. A calculation-analytical method was used to select the composition and parameters of the propulsion, which is based on the maximum relative mass of the payload criterion. Using the aircraft mass balance equation this criterion can be represented as a minimum conditions for the relative mass of the fuel and propulsion. Using this method, for an aircraft with a given mass, aerodynamic characteristics and a given flight profile, for the indicated propulsion compositions, the change patterns of the minimum relative mass of fuel and propulsion in the range of M = 2.5...4 are established. The established patterns allow choosing the propulsion composition and parameters depending on the speed of the supersonic cruising flight or choosing the flight speed of the aircraft at a given propulsion composition. The dependance of the propulsion working process optimal parameters for takeoff and cruising mode on the speed of supersonic cruising flight according to the criterion minimum of relative mass of fuel and propulsion were obtained.