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Aviation History
1963
1963 - 2023.PDF
m+$ ins FLIGHT International. 21 November 1963 825 GEARBOX i STARTER HYDRAULIC PUMP 65 kVA A,C GENERATOR The jetpipe is fixed to the engine by means of a quickly detachable flexible joint, and supported by three trunnions at 120 around the jack mounting ring. The primary nozzle is variable and is controlled by pneumatic rams fed by compressor delivery air. The jetpipe may contain a partial reheat system, and if this is fitted it will be of the single-gutter type with the fuel injectors integral with the gutter. The increase in j.p.t. thus obtained will be of the order of 300°C, and the thrust boost about 25 per cent at Mach 1.2. Reheat will be limited to a short period during the transonic acceleration/climb phase of flight, and the control will be a simple on/off switch in the cockpit. The petals of the primary nozzle (Fig 5) may be formed to carry silencing lobes, and hence provide an additional degree of jet noise ilencing of some 5 PNdb for a small thrust penalty. The function of the nozzle system is to convert the thermal and pressure energy of the engine gas stream into kinetic energy and hence thrust. The nozzle design has to be a compromise between the requirements of : supersonic cruise operation at high pressure ratios (about 15 : 1) 'where the bulk of the expansion is carried out in supersonic flow ; in the divergent section*of the nozzle, and of subsonic operation where the pressure ratio may be in the region of 2 : 1 or 3 : 1 and a simple convergent nozzle would be quite adequate. Taking the supersonic operation first, the nozzle is so matched that the jet is fully expanded and there is very little external drag due to the "boat tailing" of the rear end of the nacelle. The secon dary flow is taken from the intake boundary-layer bleed, and is used for engine-bay ventilation as well as the provision of an aerodynamic cushion over which the main jet expands. It also provides a degree of cooling to the structure surrounding the engine and jetpipe. During subsonic operation at low pressure ratio it is necessary Fig 4 The first official installation drawing of the Olympus 593 to be released for publication. According to the French industry, the sea-level static thrust of this engine will be 29,3001b to fill in a large proportion of the base area with secondary air. The intake boundary-layer flow is not sufficient for this purpose, and it is augmented by nacelle boundary-layer air taken in through the tertiary doors. The latter are opened by the pressure drop across them; it is not necessary to provide a control to accomplish this, although some damping may have to be provided to prevent rapid opening and closing in some flight conditions. The base area is additionally filled by means of the trailing-edge flaps, which close in subsonic flight. An additional function of the secondary nozzle is to provide reverse thrust during the landing run. The SNECMA reverser has two small buckets which are closed across the gas stream down stream of the primary nozzle. These buckets deflect the flow on to cascades housed in the top and bottom surfaces of the nacelle which reverse the flow direction. Reverser operation will be accomplished by levers which pull up and over the main throttle levers in their "idle" position to control the amount of reverse thrust. The first part of the movement of these levers will arm the system, and there will be an undercarriage-controlled override to prevent airborne •operation. A block diagram of the engine control system is shown in Fig 6. Throttle actuation and nozzle scheduling will be controlled elec tronically, and the single pilot's lever will reset the datum positions of these two units. Maximum or Max-Cont power will be selected at the "full throttle" lever position by means of the turbine-entry- temperature datum switch. A similar electronic unit is already under development for the TSR.2 engine. Basically the engine fuel system consists of an h-p driven fuel pump, a control valve and the fuel injectors. A high-speed shut-off cock is provided to shut down the engine in the event of a shaft failure and, hence prevent overspeeding (and failure) of the turbines. The reheat system takes its fuel supply from the main engine pump and meters the fuel flow into the jetpipe. At the same time the nozzle control unit will reset the primary nozzle area so that the engine operates at Max-Cont power whilst reheat is in operation. There will, therefore, be no engine life deterioration due to the reheat system. Additional controls are provided for compressor blow-off and the turbine cooling air. The blow-off valve will be programmed to open at low compressor r.p.m. to provide a wide surge margin, whilst the turbine cooling air will be cut off at low turbine entry temperature to improve fuel consumption during subsonic diversion and hold. fig -5 The sketch below reveals the revised form of P'opelling nozzle for the pair of engines on each side of the Concorde. The original nozzle was to be housed in a square-section box, as illustrated in our June 'J issue: I, reverser door; 2, reverser cascade; 3, supplementary cooling intakes; 4, nozzle petals; 5, minimum nozzle diameter Fig 6 Block diagram of the engine control system REVERSE SELECTOR- FULL REVERSE THRUST T.E.T. DATUM SELECTOR FORWARD THROTTLE LEVER REHEAT SELECTOR Pi TRANSDUCER SPILL DOOR i TRANSDUCER THROTTLE CONTROL UNIT TURBINE COOLING VALVE BLOW- OFF VALVE ENGINE FUEL SYSTEM HIGH SPEED S.O.C. 1 : REHEAT SYSTEM SO. C. 1 NOZZLE TRIM UNIT NOZZLE CONTROL UNIT NL 0/SPEED TO. COMBUSTION CHAMBER >NL I SIGNAL ; PRIMARY NOZZLE JACKS .TO 'REHEAT BURNER
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