GB597200A - Improvements relating to the air cooling of heat exchange surfaces in moving vehicles - Google Patents

Abstract

597,200. Automatic control systems for aero-engine cooling devices. JENNINGS, H. W. K. (Sturtevant Co., B. F.). Aug. 22, 1945, No. 21492. [Class 38 (iv)] [Also in Group XXVII] In an aero-engine air cooling system, means are provided for varying the volume of air moved over the cooling surface and for relating the velocity of the cooling air discharged from an aircraft to the aircraft speed. As shown, the electric motor 25 and gears 22 control the positioning of vanes 26 situated in the entrance of the engine cooling, and motor 50, by means of connecting rod 64 and screw-shaft 62, the setting of flaps 51 at the exit louvres. Power for both motors is supplied by battery 36. Changes in engine temperature cause mechanical movements in the thermostat 27 which operate the arm 24 carrying mutually insulated switch members 28, 59, which, when the engine is overheated are in the right-hand position and meet contacts 29, 104 and 58, 84, closing circuits through relay 34 which connect the field winding of motor 25 to the armature to rotate the vanes 26 to the open position. With the engine overcooled, arm 24 moves leftwards and switch member 28 forms a circuit with contacts 42, 106 which causes relay 34 to connect the field of motor 25 to the armature in the reverse direction to rotate the vanes to the closed position. Impact tubes 52, 53 exposed to the airstream (or slipstream) and to the air in the exit louvres respectively, are connected to the chamber 66 to cause diaphragm 67, and its associated contact arm 68, to move in response to a difference of air velocities between 52, 53. With the vanes 26 under control of thermostat 27, the diaphragm 67 moves contact arm 68 to operate relay 76 which connects the field and armature of motor 50 to cause the motor to adjust the flaps to maintain the difference in velocity at the two impact tubes at zero. With the vanes fully open and the thermostat still registering an, excessive engine temperature, the motor 25 continues to rotate until the cam 41 moves the switch members 32, 60 to the left (i.e. the position shown) causing the energization of solenoid 55, from battery 36, and thereby causing armature 91, 74 to meet contacts 97, 99. Control of motor 50, through relay 27 adjusts the flap opening to raise the rate of passage of air through the exit cowl. Conversely, if the engine becomes too cool the thermostat reduces the flap opening. Control of the vanes and flaps is restored to the thermostat and diaphragm respectively when the thermostat arm 24 returns to its neutral position. Orthodox limit switches are fitted to both motors 25 and 50. In a modification, Fig. 4 (not shown), the air from impact tubes 52, 53 acts on separate, dissimilar, interconnected diaphragms to allow for the expansion, due to heating, of the cooling air. Specification 358,154, [Group XXVI], is referred to.