Patent GB-586989-A (GB)
Title: Improvements in the governing of free piston type internal combustion compressors
IPC: F02B3/06
Filed: 1942-09-30
Abstract: 586,989. Supplying working fluid to turbines. ENGLISH ELECTRIC CO., Ltd., and WELSH, R. J. Sept. 30, 1942, Nos. 13743 and 13883. [Class 110 (iii)] [Also in Groups XXVII and XXVIII] In a power plant of the kind comprising a gas turbine 25 and a free-piston internal-combustion compressor supplying the turbine with motive fluid (combustion products, compressed air, or a mixture of the two), a speed governor 28 actuated by the turbine determines the energy input to the combustion cylinder 1 by controlling the fuel-supply regulator, and means responsive to the stroke of the free pistons keeps this stroke substantially constant by varying the volumetric efficiency of the compressor cylinders 2. As shown, the compressor is of the opposed-piston type, each piston unit comprising a power piston 4 working in the cylinder 1, a compressor piston 5 in a cylinder 2, and a piston 6 in a cushioning cylinder 3, the piston units being connected by links 7 to the ends of a lever 8 pivoted upon the cylinder 1. The compressor cylinders 2 supply air through pipes 15 to an annular space surrounding inlet ports 1a on the cylinder 1, which also has exhaust ports 1b connected by a pipe 16 to the turbine 25. Fuel injectors 9 on the cylinder 1 are supplied from a pump 10 actuated by a cam 11 oscillated by a lever 20 connected by a link 21 to one of the links 7. A ruck 10a for adjusting the output of the fuel pump is connected through a lever 32, link 31 and lever 29 to the weight-actuated sleeve 28a of the turbine-driven governor 28. Throttle valves 42 in the air inlets 14 to the compressor cylinders 2 are connected by levers 43, links 44, 45 and an interposed spring link 46, and a bell-crank 53, Fig. 3, to the piston 49 of a fluid-pressure servomotor 50 actuated in dependence upon the stroke of the free-piston units. For this purpose the control piston 55 of the servomotor is connected by links and levers 63, 61, 60, 58, 57 to an arm 8a on the lever 8 oscillated by the pistons. The piston 55 has a circumferential groove 55b and moves in a cylinder 56 having ports 56a, 56b connected to a liquid storage tank 72 and ports 56c, 56d connected respectively to an accumulator cylinder 67 containing a spring-loaded piston 68, and to the cylinder 50 of the servomotor piston 49. During the outward stroke of the free-piston units, the control piston 55 closes the port 56b and forces liquid through a non- return valve 65 to the cylinder 67 ; at the end of the outward stroke, the piston normally uncovers the port 56c but not the port 56d, while at the end of the return stroke the cylinder 67 communicates through the ports 56c, 56d with the servomotor 50. If the stroke of the free-piston units is shorter than normal, the piston 55 will force liquid into the cylinder 67 without uncovering the port 56c, and, on its return the groove 56b will allow liquid from the cylinder 67 to flow through ports 56c, 56d to actuate the servomotor 50, so closing the throttles 42 step by step. If the stroke of the free-piston units is excessive, the control piston 55 on its outward stroke will uncover both ports 56c, 56d, allowing the return of liquid from the servomotor and progressive opening of the throttles 42. If a sudden increase in the load on the turbine and of the quantity of fuel injected causes a corresponding increase in the piston stroke, the lever 53 strikes a lever 75 connected by a link 77 to a throttle valve 81 in the exhaust pipe 16. The lever 53 is also connected by links and levers 41, 85, 86, 84, 83 to a lever 39 for adjusting the eccentric 38 on which is pivoted a follower lever 23 interposed between the cam 11 and lever 24 acting on the pump 10, so that the timing of the fuel injection is controlled by the servomotor 50. The lever 39 is pivotally connected at 40 to a member sliding in a slotted lever 36 pivoted at 37 and connected by a link 35 to the fuel rack 10a, so that the timing of the fuel injection also depends upon the relationship between the quantity of fuel injected and the position of the throttle valves 42. In a modification, Fig. 4, the control piston 55 is actuated by a cam 87 oscillating with the synchronizing lever 8 and moving a lever 88 about a fixed pivot 89 against the force of a spring 90, so that the piston 55 is actuated by the freepiston units only when they are approaching the outer dead-point. In the event of an abnormally long stroke, a spring latch 91 engages some part such as an extension of the pivot pin 94 to hold the piston 55 in a position allowing the cylinder 50 to drain through the port 56d, so that the piston 49 will promptly open the throttles 42 fully and close the throttle 81. The pin 94, when held by the latch, or the servomotor piston-rod 49a in its lowest position, may actuate means to cut off the fuel supply by moving the rack 10a.