GB743498A - Jet propulsion engines with pulse-jet units - Google Patents

Abstract

743,498. Jet propulsion plant. SOC. NATIONALE D'ETUDE ET DE CONSTRUCTION DE MOTEURS D'AVIATION. April 21, 1953 [April 24, 1952], No. 10969/53. Class 110(3) A jet propulsion engine having one or more pulse jets each provided with an exhaust pipe has each exhaust pipe combined with an ejector having a forwardly facing inlet which discharges into a pressure chamber which is substantially closed except for the ejector device or devices discharging thereinto and a propulsion nozzle communicating with the atmosphere. In the arrangement shown, Fig. 1, a number of pulse jets 6 discharge through ejector units 13 and force air into a pressure chamber 16 having a propulsion nozzle 3. A cowling 1, arranged around the pulse jets 6 has a divergent portion 8 so that the velocity of the air entering the inlets 7 of the pulse jets is less than that of the air passing through the inlet 2 of the cowling. The part of the air passing through the inlet 2 not used in the pulse jets passes to the ejectors 13. When a number of pulse jets are used the explosions in the various units are preferably out of phase. A variable area nozzle 17 and re-heat burners 39 may be provided. In this arrangement the pulse jets 6 are of the automatically operating type which operate at the frequency of resonance of the sound tubes they constitute. In a modification, in which the pulse jets are fitted with aerodynamic inlet valves of the type described in Specification 731,798, the back flow through the valves is led to a separate propulsion nozzle as described in Specification 733,508. In another modification. Fig. 4, the pulse jets are formed by intermittently operating combustion chambers 28 of the type described in Specification 743.492 employing a scavenging system. A pressure drop between the inlet and outlet of the pulse jets is caused by an orifice 32. A turbine 33 may be arranged in the orifice. The chambers are intermittently operated at any desired frequency by means of a motor 37 which drives a fuel injection pump 34 and a generator 35 supplying current to the sparking plug 36. In another modification, the drop in pressure is obtained by taking the air supply for the injectors 13 frcm the boundary layers of the unit. The intermittently operated combustion chambers may be arranged in a circle or in a line adjacent one another. The latter arrangement is especially suitable for an installation in an aircraft wing. Specifications 660,144 [Group XXIX], 711,281 and 715,323 also are referred to.