Patent GB-1411769-A (GB)
Title: Condensable vapour power producing system
IPC: F01K19/04
Filed: 1972-12-28
Abstract: 1411769 Steam generation J G DAVOUD 28 Dec 1972 59760/72 Heading F4A [Also in Division F1] In an external combustion power producing system, a condensable vapour is heated to a predetermined temperature at a predetermined pressure and divided into two portions, a first of which is expanded to a lower pressure in a work producing means (e.g. turbine 23) the second being expanded in such a way that the work it produces is used (e.g. in a unitary free piston type expander/compressor 21) to compress the expanded vapour of the second cycle together with additional vapour and/or liquid to the original predetermined pressure. In Fig. 6, the expanded vapour from turbine 23 is used in part to drive a turbine 24 before being condensed and heated to a state denoted by point F on the pressure-enthalpy diagram in Fig. 1 where it is mixed with vapour at point E, E1 or E2 in expander/compressor 21 and compressed before being fed to superheater 22. The expansion of of w lbs of superheated vapour from pressure P to pressure p may end in the superheat region E1), on the saturated vapour line (E) or in the region of mixtures (Eg), the subsequent admixture with water changing the state of the vapour to point J before compression to point C which is shown on the saturated vapour line but may be in the region of mixtures, Fig. 2 (not shown), in the superheat region or on an isentropic line passing through the critical point C. In Fig. 7 (not shown) some vapour by-passes the turbine 24 and is used to heat water passing through heater 26. Expander-Compressor. A unitary free-piston type expander-compressor is shown in Figs. 4B and 4D, in which superheated steam is admitted through valve 5, expanded steam through valve 8, water through valve 7 and the compressed vapour is returned to the superheater via valve 6. Superheated steam is admitted when pistons 3, 3<SP>1</SP> are close together and expanded steam is introduced when the superheated steam has pushed the pistons some way apart, so that the now expanded superheated steam has reached the same state as the steam admitted through valve 8. Valve 8 is closed and water is admitted through valve 7 after which the pistons 3, 3<SP>1</SP> move together again under the influence of the air compressed in bounce chambers 2, 2<SP>1</SP> to press the vapour which is released to the superheater through valve 6 when the pistons 3, 3<SP>1</SP> are again close together. The cycle is then repeated. Figs 5A-E (not shown) are of a double acting expander-compressor with three working chambers, one between the pistons and one outside of each piston. Figs 8 and 10 (not shown) are of pressureenthalpy diagrams in which losses are taken into account, e.g. the pressure drop through the superheater and the non-isentropic mixture of the compressions and expansions. The corresponding systems are in Figs. 9, 11 (not shown) and include re-heat stages. The specification includes calculations to obtain the relative flow rates denoted by w, y, z, k, etc. and corresponding cycle efficiencies. The working fluid may be water, or other fluids containing polar groups of low molecular weight, e.g. ammonia, carbon dioxide, methanol, ethanol and trifluorethanol.