GB821822A - Improvements in and relating to heat engines operating on the stirling or ericsson heat cycles - Google Patents

Abstract

821,822. Hot gas engines and power plant. ENERGY Ltd. Dec. 12, 1955 [Oct. 5, 1954], No. 28660/54. Class 7(1) In an engine operating on the Sterling or Ericsson heat cycle, the working medium is dehydrated carbon dioxide with or without admixture of one or more of the inert gases in dehydrated form. In Fig. 1 a working piston 2, 3 operates in a double acting cylinder 1 which is associated with two displacer cylinders 7, 8. The cylinders 7, 8 are conveniently formed of bronze and constitute cold chambers. They are formed with jackets supplied with cooling water. Into the upper end of each cold chamber casting is screw threaded a cylinder 9, 10 of heat resisting alloy constituting a hot chamber. A suitable alloy might have the following composition: carbon 0.4%, manganese 0.8% silicon 1%, nickel 13%, chromium 13%, cobalt 10%, molybdenum 2%, niobrium 3%, tungsten 2.5% and iron the balance. The displacer is hollow and preferably formed of the same alloy as the hot chambers. The primary regenerator preferably comprises a series or stack of thin perforated discs or rings 24 formed from wire gauze of 200 mesh. Alternatively compact coils of fine wire of suitable metal may be employed. The displacers are operated by a cam on the crank shaft. There is provided between each of the working cylinder spaces and the adjacent cold space an auxiliary regenerator which may comprise a series of fine mesh gauze rings or discs 34 or may comprises coils of fine wire for example nichrome wire wound into compact coils. The auxiliary regenerator acts as a baffle or collector of oil or lubricant from the working cylinder and it may be arranged that lubricant collected is drained off into a sump. Heat may be supplied in any convenient way for example by burners in combustion chambers or by furnace or industrial waste gases which are caused to pass through a chamber surrounding the upper ends of the displacer cylinders. Ribbed tubes may be used to provide efficient heat intake from the burner gases. Assuming that the working medium is to be carbon dioxide this is fed from the usual storage cylinders through a reducing valve and thence through openings in the castings 7 and 8 to the two ends of the working cylinder through non-return valves the openings 36 being connected to suitably arranged gas relief valves. The gas may be supplied to the cool cylinder at any desired pressure up to a maximum of 400 lbs./sq. in. The carbondioxide may be used in conjunction with one or more of the inert gases such as nitrogen, helium, argon or neon. Glands are fitted to the piston rod and displacer rods. These glands may be of twist fibre. The working piston is fed with high pressure oil from an engine driven pump. The working pressure may be reduced to 150 lbs./sq. in. A plurality (four or more) of working cylinders may be associated with a common crankshaft or alternatively are connected to a wobble plate drive. Each cylinder may be double acting in the sense that it consists of a hot chamber bolted on its top and a displacer piston bolted on to its working piston. The top of each hot chamber is connected by a suitable tube to the bottom of the next cylinder assembly. Where a crankshaft method of drive is used the cylinder units should be. mounted in pairs each pair constituting a 90‹ V formation. Any number of banks of such V formations can be assembled one behind the other on,a common crank case and with their several pairs of connecting rods connected to a common crankshaft. Figs. 2 and 3 show a modification in which gases are admitted to a regenerator 64 from a storage chamber 51 under control of an inlet valve 62. The regenerator is connected by heater tubes 65 which lead through a combustion chamber to the upper end of the hot chamber 44. An outlet tube 73 from the regenerator 64 leads to the cooler 67. The compressor assembly consists of a high pressure cylinder 48 surrounded by a water jacket 49. The intercooler 40 connects 48 with the gas storage bottle 51. A pressure equalizing tank 70 fitted with a safety valve 71 and blow off cock 72 is connected between the first and second compression stage the connection being completed through the cooler 52. The displacer piston 45 is hollow and is filled with powder such as magnesium oxide or microporous silica (silica aerogel). Conveniently the regenerator is loaded with fine metal gauze and the heater tubes of which there are 70 each with a ribbed length (see Fig. 5) of 24 inches have a cross sectional shape as shown in Fig. 4 and are preferably arranged as shown in Fig. 5. The exterior of the combustion chamber is covered with a layer of microporous silica and the hot chamber and upper parts of the regenerator are similarly insulated the covering in each case being contained in a bright aluminium jacket. The combustion chamber walls are made of a heat resisting alloy of the requisite strength at 850‹C. and of good non-scaling properties up to a temperature of 1100‹C. with the furnace gases. The composition of this alloy is nickel 20%, chromium 25%. silicon 1.5%, carbon 0.15%, balance iron. The inner wall of the hot chamber is thermally insulated by means of a layer of microporous silica of “ in. thick contained in a sealed canister of an alloy such as stainless steel. The regenerator may consist of 200 mesh gauze of metal sold under the Registered Trade Mark "Monel" and be constructed of a plurality of discs stamped out of the same gauze and packed tightly into the cylindrical cylinder of the regenerator. The working gas may be carbon dioxide at a pressure varying from 240 lbs. to 800 lbs. per sq. in..Two identical expansion units may be assembled in right-angled V formation with their identical pistons and connecting rods working on a common crank pin. Two regenerators each with its own combination of cams would be employed. Four or more identical expansion units could be assembled in right-angled V formation on a common crankshaft as above. Only two set of regenerators would be necessary as each regenerator could be made to serve two or more expansion units. The tubular heaters from any number of expansion units could have their heater tubes all welded into the common top of one regenerator. For such an engine one compressor unit could be employed driven from the crankshaft at any suitable gear ratio. An "isothermal" centrifugal compressor could be driven at 2,800 r.p.m. from the crankshaft. The crank case 43 may be pressurized to approximately 240 lbs./sq. in.