Patent GB-475730-A (GB)
Title: Improvements in or relating to reciprocating piston machines of the free-stroke type
IPC: F02B71/00
Filed: 1936-03-24
Abstract: 475,730. Regulating compressors. SULZER FRERES SOC. ANON. March 24, 1936, No. 8719. Convention date, April 3, 1935. [Class 8 (i)] The invention relates to " free-stroke " reciprocating piston machines of the type comprising at least one piston which reciprocates within an internal combustion cylinder, the combustion of a charge in the internal combustion cylinder causing the piston to move on its expansion stroke therein and thereby compress a gas, such for example as air, in a gas compression cylinder, this gas being delivered to the point of consumption or utilization. Thus, air may be compressed in the gas compression cylinder and delivered to the internal combustion cylinder, from which the exhaust gases including excess air are delivered to a consumer, such for example as a gas turbine. According to the invention, a free-stroke reciprocating piston machine of this type has control means whereby the charge which im- . parts energy to the piston during the expansion stroke thereof within the internal combustion cylinder is automatically controlled in accordance with any variation from normal of the movement of the piston during the immediately preceding compression stroke within the combustion cylinder so as to be reduced or increased respectively in accordance with the increase or decrease of the maximum speed of the piston during such immediately preceding compression stroke. The term " charge " refers to the quantity of fuel and/or air supplied to the internal combustion cylinder. In one form, Fig. 1, pistons 2, 3 work in opposition in an internal combustion cylinder 1 and are formed integral with air compression pistons 4, 5 single-acting in air-compression cylinders 7, 8 ; air is drawn in through suction valves 9 and delivered through valves 10 to a delivery pipe 11 which may be constructed so as to constitute an air receiver or reservoir whereby oscillations in the delivery pressure will be damped ; the air passes through inlet ports 12 into the combustion space 6 to scavenge and recharge the latter ; the compressed air is then further compressed in the internal combustion cylinder, fuel is injected and combustion commences. The mixture of waste gases and air passes through exhaust ports 13 to a turbine 15. The fuel supply comprises a low pressure pump, the plunger 18 of which is actuated by a cam 20 oscillated by movement of the piston 4 through a rod 22 ; connection with the reservoir 23 is controlled by a suction valve 24 which near the end of the delivery is lifted by a lever 27 oscillating about an eccentric 26 adjustable by means of a lever 28 ; the fuel is delivered to a high pressure pump 25 comprising a plunger 32 subject to the pressure in the combustion chamber 6 and a plunger 30 which delivers fuel to the injection valve comprising a needle valve 36 loaded by a spring 37. The control means comprises a spill valve 38 having a groove 48 controlling the passage of fuel from the injection valve through conduit 47 and pipe 49 to the reservoir 23 ; the spill valve is loaded by a spring 45 and is opened by one arm of a bell-crank lever 41, the other arm of which is contacted by a rod 42 on the piston 4 at a certain point in the stroke of the latter ; the lever 41 oscillates about an eccentric 40 adjustable by lever 44. In normal running, a certain amount of the fuel supplied to the injection valve is returned by the spill valve to the reservoir; if the penetration of the pistons 2, 3 in the internal combustion cylinder increases, the amount of fuel spilled is increased, thus reducing the charge. The eccentric 40 may be automatically adjusted, through lever 44 and linkage 52, 53, by a governor 51 on the turbine 15, so that when the speed of the turbine varies owing to variations in the load thereon the normal fuel supply is automatically adjusted in such manner as to restore the speed to normal. The pressure at which air is supplied to the internal-combustion cylinder may be varied in addition to the quantity of fuel supplied thereto. In a modification, the lever 41 oscillates about a fixed pivot, and the governor 51 actuates, through linkage 52, 53 and lever 28, the eccentric 26 so that the suction valve 24 is opened earlier or later in the delivery stroke of the plunger 18, whereby the delivery of fuel is adjusted automatically in accordance with the speed of the turbine. Alternatively, both the levers 28, 44 may be controlled in accordance with the pressure of the charging air in the passage 11. In a further modification, the upper arm of the bell-crank 41 acts, not on the spill valve but on the lever 28 to vary the effective length of the delivery stroke of the plunger 18 by varying the time, during said delivery stroke, over which the valve 24 remains closed, and thus controlling the quantity of fuel delivered by the low pressure pump. Again, the low pressure pump may deliver direct to the injection valve and stabilization be effected by displacing the whole injection period, that is by shifting not only the timing of the commencement but also the timing of the end of the injection, relatively to the moment at which each piston reaches the end of its compression stroke within the internal combustion cylinder. To this end, for example, when means are provided whereby not only the quantity of fuel drawn into the low pressure pump cylinder during the suction stroke but also the proportion of such fuel which is delivered to the combustion cylinder are controlled, the setting of the apparatus controlling both these valves has to be altered. In a modification, Fig. 5, a valve 50 controlling the outlet of air from the combustion space 6 through pipe 60 is opened against a spring 57 by pressure built up in the dashpot 54 during the inward stroke of the pistons ; if the penetration of the pistons increases, a greater volume of air is discharged. The final pressure is thus maintained constant, so that stabilization is effected. The air discharged through valve 50 may pass to the air supply ports 12, to the pipe 11 or to a receiver to which air under pressure is supplied from the cylinders 7, 8. In a modification, the supply of pressure air to the internal combustion cylinder is controlled by a valve actuated by the pressure in the dashpot 54 in the opposite sense to the valve 58, whereby the supply of air is decreased when the penetration increases. The pistons of the arrangements shown in Figs. 1, 5 are connected together by synchronizing mechanism comprising a rocking lever and connecting rods as illustrated by chain lines in Fig. 5 ; so as to move in opposition. The invention may also be applied to forms in which pistons in separate cylinders are synchronized mechanically, hydraulically or otherwise so as to move in the same direction. The gas compression piston may be arranged to compress and deliver gas other than air, in which case scavenging air may be supplied to the internal-combustion cylinder by a separate pump or fan, the exhaust gases from the internal-combustion cylinder being delivered, say to the atmosphere or to the same machine as, or a separate machine from, that to which the gas is delivered from the gas compression cylinders.