GB867762A - Installation comprising a plurality of gas-generators, more particularly free-pistongenerators, producing hot gas under pressure - Google Patents

Abstract

867,762. Combustion product plant. SOC. D'ETUDES ET DE PARTICIPATIONS EAU GAZ, ELECTRICITE, ENERGIE S.A. Feb. 29, 1960 [March 18, 1958], No. 7061/60. Class 7(1)' An installation comprising a plurality of gas generators producing hot gas under pressure more particularly freepiston generators is characterized by a passage connecting two compressor cylinders of at least two gas generators and by means permitting the transfer of air through the passage from one of the two compressor cylinders to the other at least at low loads. In Fig. 1 the two engine cases 8 may communicate with one another as shown or may if preferred be separated from each other by a closure plate 10 shown dotted. In place of the mean pressure acting below the face 16b of the piston 16 a pressure taken from the cushion for a predetermined position of the piston elements 3b may be employed. There is established at least for low loads of the installation a communication between at least two of the compressor compartments 2a of the two gas-generators A and B for at least a part of their working cycle during which different pressures prevail in these cylinders such that there is a transfer of air from one of the cylinders to the other. It is assumed that the two gas-generators A and B are maintained at a constant phase difference of 180 degrees. In such case it is merely necessary to provide in the communication conduits 33 means which by construction or more or less complete closure produce in the conduits 33 a variable resistance to the flow of transferred air. These means effect a greater reduction in the cross-section of the conduits 33 as the load of the installation increases and close these conduits completely at a load at which the turbine 28 can absorb the quantity of gas supplied by the gas generators without the communication. The means for controlling the free cross-section of the conduits 33 may have for example the form of slide valves 34. A rod 35 connects together the two slide valves 34 and these two valves are controlled by a factor whose magnitude depends upon the load under which the installation is operating. To effect this control of the slide valves they may be connected by means of a rod 35a to a piston 36 under the action of liquid put under pressure by a governor 27 driven by the turbine 28 the liquid also controlling the fuel supply. Preferably, the transfer conduits 33 are inside the casing 6 to reduce noise produced by the transfer. To maintain the two generators at a phase difference of 180 degrees there may be used a device such as that shown in the left hand part of Fig. 1 and comprising a contactor arm 38 driven at a fixed speed for example by an electric motor. The displacement of the brushes 39 and 40 determines the displacement in the functioning of the pistons of the gas generators as described in Specification 853,183. To ensure a discharge as long as the gas generators are running in phase, each of the conduits 33 is put in communication with the surrounding air or with the suction casing and this communication is closed only at the moment at which the desired phase difference between the gas generators is obtained. A particularly simple device for effecting this is shown in Fig. 2. Fig. 5 shows a simplified system applied to an installation having two generators operating with a phase difference of 180 degrees. The slide valve 34 can occupy only two positions, one for which it completely closes the conduit 33 and the other for which it completely opens the conduit 33. The valve 34 is controlled by means of a cock 48. The slide valve 34 is opened fully only for starting and running idle. It is sufficient to provide the slide valve 34 on one side only of the two generators. The arrangement of Fig. 7 is applicable to the case where the gas generators operate almost always at their maximum power or to the case where fuel consumption is of secondary importance and where simplification of the installation is of first importance. In this arrangement the output of power gas is regulated throughout the entire range of different powers by greater or lesser opening of the conduit 33 connecting together the two compressor spaces 2a. The slide valve 34 completely closes the conduit 33 only at the moment when maximum power is reached. The slide valve may be controlled by a governor 27 as shown in Fig. 1. Regulation of the quantity of fuel injected may be effected by the pressure prevailing in the engine case 8 of each gas generator. The cross-section of the communication conduit 33 may be constant and the phase difference between the two gas generators may be varied. The phase difference may be varied by movement of at least one of the brushes 39, 40 (Fig. 1). The phase difference between the gas generators and the cross-section of the conduit or conduits 33 may be varied simultaneously. The single control member 34 may be replaced by tvo control members controlled simultaneously, each of these members being close to one of the two compressor spaces. The communication between the compressor cylinders may be controlled by alternating means which during each working cycle of the free pistons produce an opening and closing of the communication between the compressor spaces. The number of gas generators having their compressor spaces connected together by a transfer conduit may be greater than two.