Patent GB-704472-A (GB)
Title: Improvements in speed limiting governors for continuous combustion turbine engines
Inventor: SIMMONS HAROLD CUTHBERT
IPC: F02C9/28
Filed: 1951-04-09
Abstract: 704,472. Gas turbine plant. DOWTY EQUIPMENT, Ltd. March'28; 1952 [April 9, 1951], No. 8227/51. Class 110 (3). [Also in Group XXIX] A speed limiting governor for a continuous combustion turbine engine comprises a vent valve 20, Fig. 3, for a servomotor which controls the delivery of fuel to the engine, said valve being opened when the engine reaches the desired speed to limit the fuel supply. Fuel is supplied by a pump 11 having a bye-pass valve 14 actuable by a piston 17 controlled by valve 20, or the'pump may be of the variable stroke type in which the valve controls the stroke varying member. Up to the limiting speed the piston 17 is controlled by a .vent in a line 18. Valve 20 is fixed on a lever 21 subjected in a valve closing sensed to a spring 23 and to opposed pressures on a diaphragm 22. These pressures are constituted by the pressure rise across an engine driven centrifugal pump 24, and when the limiting speed as set by spring 23 is reached the pressure rise overcomes the spring and opens valve 20. In order that the governor may be used with different fuels, e.g. diesel oil, kerosene and petrol, of different densities, the pressure drop across the pump 24 is arranged to be constant at the limiting speed, for all fuels, by providing a compensating back flow in the line 27 on the high pressure side of pump 24. The flow takes place through a fixed orifice 31 from a line 32 connected to a source of pressure higher than pump inlet pressure, e.g. the main delivery line 13, and having restricting means 34 and a pressure reducing valve 33. Valve 33 maintains a pressure at its outlet at a constant amount higher than pump inlet pressure and means 34 includes an orifice 36, Fig. 4, in series with an annular restricted passage 37. The relationship between viscosity and density of the previously mentioned fuels is that their curves plotted for different temperatures lie substantially on a common curve, as shown in Fig. 2. Thus changes in viscosity of fuel as sensed by the means 34 reflect the changes in density. Hence, e.g., a low viscosity fuel which gives a lower pressure rise across the pump 24 than a high viscosity fuel, will give a higher flow through and hence pressure drop across orifice 31. The pressure difference across the pump and orifice 34 when the engine is at its limiting speed will therefore be constant for any of the fuels. Valve 33 comprises a closure member 42, Fig. 4, balanced as regards inlet pressure, mounted on a lever 43 pivoted at 44 and actuated by a piston 48 subjected in a valve-opening sense to the inlet pressure of pump 24 in line 26 and an adjustable spring 50, and in a valve closing sense to the pressure on the inlet side of orifice 36. The orifice 17a, Fig. 3, through piston 17 may be replaced by an orifice 17b, Fig. 4, separated-from the piston, and the diaphragm 22 by a bellows 22a. The spring 23 may be adjusted in response to altitude changes and the pump 24 may be constituted by the rotor of pump 11. It is stated that the restriction 31 may be positioned on the inlet side of pump 24.