Patent GB-525496-A (GB)
Title: Improvements in hot air or gas power engine plant
IPC: F02C1/04
Filed: 1939-02-22
Abstract: 525,496. Hot air power plant. MARTINKA, M. Feb. 22, 1939, Nos. 5913 and 5914. Convention dates, Feb. 23, 1938 and Oct. 28, 1938. [Class 7 (i)] [Also in Group XXVI] In a power plant using air or other gaseous working medium the medium is first compressed in a compressor, then passed to a heat-exchanger heated by gases and expanded in a motor and finally exhausted into a combustion chamber to which fuel is admitted to burn in the medium the combustion gases being used to heat the exchanger. As shown in the Figures, a multi-stage compressor V discharges air at about 7 atmospheres pressure into a saturator S supplied with hot water from inter-stage coolers 2 . . . 4 of the compressor, the water being further heated by a surface heat-exchanger 23 heated by burnt gases leaving a heat storage element R. The element R comprises several chambers each of which is first heated by the passage therethrough of burnt gases from a combustion chamber B where oil is burnt in the exhaust air or gas from a turbine T or other motor driven by the moist compressed air heated by passage through the heat storage element R to a temperature of about 950‹ C. Each chamber in the element R is alternately heated by the burnt gases and then opened to the compressed air stream to which it transfers its heat, the air thus attaining a temperature of about 600‹ C. If the heat is to be derived from gas instead of oil, the exhaust from the turbine T is tapped and part fed to a heatexchanger to raise the temperature of the gas. When using powdered fuel, the blast necessary to blow the fuel into the combustion space is derived from a blower set in the pipes discharging the burnt gases from the heat storage element R. The powdered fuel falls from a hopper 21, Fig. 4, past a rotating shaft 25 formed at its lower end as a valve and thereabove with an eccentric portion to serve as an agitator; the fuel drops on to a worm feed 22 which delivers it to a vertical pipe 26 leading to a chamber 24 where the blast entering by a pipe 20 encounters it and discharges it into the combustion chamber B. The exhaust gases from the turbine T enter the Chamber B tangentially through overlapping plates 27 and helical overlapping plates 29 at the top of the chamber. As shown in Fig. 7, the burnt gases leaving the storage element R, after traversing heat exchangers 23, 11 are fed to a washer W, where lime water may be used to free them from acid impurities, and thence to a compressor V1 which delivers them through a saturator Sl and the heat storage element R to the turbine T1 the whole forming a closed circuit. To maintain in the circuit sufficient fresh air for combustion in the chamber B, a compressor V2 supplies moist air to a heat exchanger 37 heated by the exhaust from a low pressure turbine T2 fed from the exhaust of the turbine T1 through a pipe 35 branching from the pipe 14 leading from the turbine T1 to the chamber B. The efficiency of the low pressure turbine may be increased by feeding it from the outlet instead of the inlet of the combustion chamber B or the exhaust from the turbine T1 may be heated in a heat exchanger heated by an additional combustion chamber similar to the chamber B. In a further modification, the feed for the low pressure turbine T2 is taken from a point between the washer W and the compressor V1 and is heated in a storage element similar to the element R the discharge from the turbine T2 serving to heat another similar storage element which replaces the heat exchanger 37, Fig. 7. According to a further modification, a simple heat exchanger is inserted in the feed to a low pressure turbine and water from a washer is led to a reduced pressure chamber where it boils. The steam evolved after being superheated in a heat exchanger drives an additional turbine the exhaust of which is condensed at and fed back through a filter to the washer. Some of the water fed back may be circulated through the intermediate coolers of the compressor and then be led directly to the reduced pressure chamber. The output of the plant may be controlled by adjusting the temperature of the compressed air fed to the turbine by using two heat storage elements heated respectively by the exhaust from the turbine and by burnt gases from the combustion chamber and dividing the air stream between them in varying proportions or by varying the heat supplied to the different elements. A plant for carrying out this method consists of a central conduit 103, Fig. 11, down which gases exhausted from the turbine T1 flow, part of them encountering a heated portion 105 of a heat exchanger while the other part traverses an outer annular passage 106. Surrounding the heat exchanger are arranged nine heat storage elements 110, 110<1> of which the elements 110 have inlets 111 for combustible gas while the others 110<1> are heated solely by the gases from the turbine. During the heating operation, the gases are admitted to the chambers 110<1> past valves 108, ascend a central passage 113, flow outwardly between heat storage plates. 112, then downwardly to a chamber 115 and finally past a piston valve 116 to a withdrawal conduit 119. The heating operation being completed, the valve 116 is lowered to admit compressed air from a pipe 120 and the air traverses the chamber 115, flows radially inwards between the hot plates 112 and outwards past a selfclosing valve 122, which may be water cooled, to a passage communicating with the inlet pipe 102 to the turbine. When the element needs re-heating, the piston valve 116 is raised cutting off the compressed air supply ; the reduced pressure permits the valve 122 to close and the va ve 108 is opened to admit the heating gases as before. In the chambers 110 the process is similar wi th the addition of the combustible gas through the inlets 111. The combustible gas is pre-heated by the heat exchanger 105. To ensure equality of temperature between the gases in the discharge pipe 119 and those leaving the heat exchanger, a valve 130 controls the proportion of gases passing through the heat exchanger 105 and the chamber 110<1> respectively and may be actuated by a heat-sensitive device. In regulating the output of the plant, when the compressed air supply is diminished, the proportion thereof directed through the combustion chambers 110 is also reduced. The compressed air thus enters the power engine at a lower temperature, but due to the smaller expansion undergone therein, loses less heat and the exhaust temperature is maintained. The piston valves 116 associated with the combustion chambers 110 throttle both the inlet of compressed air and the outlet of burnt gases unless the air introduced is at its maximum pressure. Each piston valve 116 is actuated by mechanism, not shown, comprising a piston displaced in a cylinder under control of a slide valve itself actuated from a cam on a shaft driven through worm gearing by an electric motor, a series-of cams on the shaft ensuring the successive operation of the various heating chambers. A wedge disposed between projections on the rod connecting the valve 116 and piston limits the stroke of the piston and is coupled to a spring-pressed piston exposed to the pressure of the compressed air, the arrangement permitting a full stroke of the piston valve only when the pressure of the compressed air has interposed the thinnest portion of the wedge between two abutments. Hand-controlled emergency cut-off valves 162, 163 are provided in the passages 107, 118.