Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
  • F01B—MACHINES OR ENGINES, IN GENERAL OR OF POSITIVE-DISPLACEMENT TYPE, e.g. STEAM ENGINES
  • F01B3/00—Reciprocating-piston machines or engines with cylinder axes coaxial with, or parallel or inclined to, main shaft axis
  • F01B3/04—Reciprocating-piston machines or engines with cylinder axes coaxial with, or parallel or inclined to, main shaft axis the piston motion being transmitted by curved surfaces
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
  • F02G—HOT GAS OR COMBUSTION-PRODUCT POSITIVE-DISPLACEMENT ENGINE PLANTS; USE OF WASTE HEAT OF COMBUSTION ENGINES; NOT OTHERWISE PROVIDED FOR
  • F02G1/00—Hot gas positive-displacement engine plants
  • F02G1/04—Hot gas positive-displacement engine plants of closed-cycle type
  • F02G1/043—Hot gas positive-displacement engine plants of closed-cycle type the engine being operated by expansion and contraction of a mass of working gas which is heated and cooled in one of a plurality of constantly communicating expansible chambers, e.g. Stirling cycle type engines
  • F02G1/044—Hot gas positive-displacement engine plants of closed-cycle type the engine being operated by expansion and contraction of a mass of working gas which is heated and cooled in one of a plurality of constantly communicating expansible chambers, e.g. Stirling cycle type engines having at least two working members, e.g. pistons, delivering power output
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
  • F02G—HOT GAS OR COMBUSTION-PRODUCT POSITIVE-DISPLACEMENT ENGINE PLANTS; USE OF WASTE HEAT OF COMBUSTION ENGINES; NOT OTHERWISE PROVIDED FOR
  • F02G1/00—Hot gas positive-displacement engine plants
  • F02G1/06—Controlling
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
  • F02G—HOT GAS OR COMBUSTION-PRODUCT POSITIVE-DISPLACEMENT ENGINE PLANTS; USE OF WASTE HEAT OF COMBUSTION ENGINES; NOT OTHERWISE PROVIDED FOR
  • F02G2244/00—Machines having two pistons
  • F02G2244/02—Single-acting two piston engines
  • F02G2244/06—Single-acting two piston engines of stationary cylinder type
  • F02G2244/12—Single-acting two piston engines of stationary cylinder type having opposed pistons
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
  • F02G—HOT GAS OR COMBUSTION-PRODUCT POSITIVE-DISPLACEMENT ENGINE PLANTS; USE OF WASTE HEAT OF COMBUSTION ENGINES; NOT OTHERWISE PROVIDED FOR
  • F02G2244/00—Machines having two pistons
  • F02G2244/50—Double acting piston machines

Definitions

• This invention relates to Stirling-cycle engines, also known as regenerative thermal machines, and more particularly to a new family of thermodynamic working fluids for such machines.
• the working fluids of the present invention are specifically selected with regard to whether or not they possess a high dynamic heat transfer coefficient, as defined by knovm empirical relations for heat transfer in turbulent flows, in addition to other requisite thermophysical properties such as chemical inertness and thermal stability.
• a Stirling-cycle engine is a machine which operates on a closed regenerative thermodynamic cycle, with periodic compression and expansion of a gaseous working fluid at different temperature levels, and where the flow is controlled by volume changes in such a way as to produce a net conversion of heat to work, or vice versa.
• the regenerator is a device which in prior art takes the forta of a porous mass of metal in an insulated duct. This mass takes up heat from the working fluid during one part of the cycle, temporarily stores it within the machine until a later part of the cycle, and subsequently returns it to the working fluid prior to the start of the next cycle.
• the regenerator may be thought of as an oscillatory thermodynamic sponge, alternately absorbing and releasing heat with complete reversibility and no loss.
• thermodynamic system A reversible process for a thermodynamic system is an ideal process, which once having taken place, can be reversed without causing a change in either the system or its surroundings.
• Regenerative processes are reversible in that they involve reversible heat transfer and storage; their importance derives from the fact that idealized reversible heat transfer is closely approximated by the regenerators of actual machines.
• the Stirling engine is the only practical example of reversible heat engine which can be operated either as a prime mover or as a heat pump. Background
• the invention comprises fundamental concepts and material properties which are used in combination to form a new and less complicated technology base for the development of improved Stirling-Cycle machines, specifically including the following: (1) working fluids other than hydrogen, helium, or air, namely certain fluorine compounds exemplified by by sulfur hexafluoride, perfluorobutane, perfluoropropane, and octafluorocyclobutane, which provide an increased dynamic heat transfer coefficient yet are nonflammable, nontoxic, and easily liquefied; and (2) an engine power level control subsystem by which the r ⁇ e-an system working pressure, and thereby the instantaneous power level of the engine, is conveniently varied by the hydraulic injection or ejection of condensed working fluid through a special heat exchanger to be known as the reservoir cooler.
• working fluids other than hydrogen, helium, or air namely certain fluorine compounds exemplified by by sulfur hexafluoride, perfluorobutane, perfluoropropan
• thermodynamic working fluids for Stirling-cycle, reciprocating, thermal machines other than the usual hydrogen, helium, or air which possess increased dynamic heat transfer coefficients; have a critical temperature somewhat above the minimum ambient temperature of the available heat sink yet somewhat below the designated heat rejection temperature of the cycle as maintained within the engine cooler; and which are also nonflammable, nontoxic, and inexpensive, inert, and of low viscosity.
• FIG. 1 is an illustration of the operational sequence of events during one complete cycle of an idealized singleacting two-piston Stirling engine used in the prime mover mode;
• FIG. 2(a) and FIG. 2(b) are schematics which illustrate the idealized pressure-volume and temperature-entropy diagrams of the then ⁇ odynaraic cycle of the working fluid in the same machine depicted by FIG. 1;
• FIG. 2(c) is a pressure volume diagram which depicts the working of an actual machine;
• FIG. 3 is a bar graph comparison of the dynamic heat transfer coefficient calculated for various gaseous working fluids relative to air.
• FIG. 4 is a schematic representation of means for controlling the instantaneous power level of a Stirling-cycle machine by adjusting the mean operating pressure.
• numeral 1 designates an idealized version of a two-piston Stirling-cycle prime mover.
• a conceptually constant mass of pressurized gaseous working fluid occupies the working volume between the compression piston 2 and the expansion piston 3.
• the total working volume is comprised by compression space 4, regenerator 5, and expansion space 6.
• a portion of compression space 4 is continually cooled by cooler 7, while a portion of expansion space 6 is continually heated by heater 8.
• Arrows 9 are intended to represent the input of heat by conduction, convection, or radiation. Escape of fluid from the working volume is prevented by the piston seals 10.
• regenerator 5 yields stored heat to the working fluid as it is transferred to expansion space 6 with the volume remaining constant. The temperature and pressure rise to their maximum levels.
• regenerator 5 recovers heat from the working fluid as it is transferred to compression space 4 with the volume remain ing constant. The temperature and pressure return to the starting levels of the cycle.
• FIG. 2(a) and FIG. 2(b) wherein the same complete cycle is presented in terms of the pressure-volume diagram and the temperature entropy diagram for the working fluid.
• the area under a curve on the P-V diagram is a representative measure of the mechanical work added to or removed from the system during the ,,procesp.
• the area under a curve on a T-S diagram is a measure of the heat transferred to or rejected from the working fluid during the process.
• One favorable embodiment of the present invention is the utilization of alternative working fluids which provide increased performance, greater safety, and improved reliability. From a historical standpoint there appear to be only three working fluids of significant interest for appli cation in regenerative thermal machines: air, helium, and hydrogen. Air was and still is of interest primarily because of its universal availability. But helium and hydrogen are the normal working fluids of choice in the prior art because their thermophysical properties are such as to permit high rates of heat transfer and flow to occur, with relatively low viscous flow losses, compared to air.
• the three alternative working fluids suggested by FIG. 3 are nontoxic, nonflammable, and easily liquefied under pressure at room temperature, which leads to improved safety and ease of handling. They are also chemically and thermally stable, and generally possess a much higher molecular weight corr.pared to hydrogen or helium. According to Graham's Law the rate at which gases tend to diffuse through very small openings is inversely propor tional to the square root of their density. Thus these high molecular weight gases present a far less difficult reciprocating seal design problem compared to either hydrogen or helium, and a far greater quantity of makeup fluid can be stored in a given volume as a liquefied gas than as a pressurized gas.
• Drag (Speed) exp2 x Density x (Size)exp2.
• the invention proposes the uuilization of the indicated compounds, and others, as alternative working fluid media in the Stirling-cycle engine.
• the essence of this concept is the novel recognition that such working fluids should be selected primarily with regard to whether or not they exhibit a high dynamic heat transfer coefficient, outstanding chemical and physical inertness, and the requisite critical properties to facilitate liquefaction under normal operating conditions.
• Another favorable embodiment of the invention is an engine power level control subsystem, to be used in conjunction with the operation of any regenerative thermal machine, by means of which the mean system operating pressure can be rapidly and automatically varied as a function of power demand.
• the operating power level is normally controlled by simultaneously adjusting both the quantity of heat input to the heater head and the mean working pressure of the cycle, since it is these variables which most directly influence the power level.
• the first of these is accomplished by means of a combustion control subsystem quite similar in function to the familiar accelerator/throttle linkage of the automotive internal combustion engine, except that the time response is much slower due to the large thermal mass of the heat transfer components.
• the second however, currently requires a complex pressure control subsystem consisting of pressurized heavy wall stainless steel hydrogen gas bottles; sophisticated servoactuated high pressure flow control valves; an array of essential and specially designed check valves, stop valves, bypass valves, relief valves, gauges, and the like; and a high-capacity, hydrogen-compatible compressor as described in prior art patents filed under Subclass 521 of Class 60. (see for example U.S. Patent No. 3,699,770; No. 3,827,241; or no. 4,030,297).
• the control subsystems re quired to vary the power level of prior art Stirling-cycle engines are both complicated and costly, and they represent a critical stumbling block to the economical use and the widespread acceptance of these engines. This is particularly true today with respect to prime movers which might be sold in the highly competitive worldwide automotive market.
• FIG. 4 Attention is now directed to the schematic illustration of FIG. 4 wherein a novel power level control subsystem is depicted which is deliberately intended to operate in a single-component two—phase mode.
• This system is similar to the prior art in that it operates on the well-known principie that a change in the steady state power level of a
• Stirling engine is virtually a direct linear function of a change in the mean operating pressure of the gaseous working fluid contained therein. But it is radically different from previous systems in that the working fluid is intended to undergo a change in phase whenever it is added to or withdrawn from the working volume. Thus it is another impoftiant specific teaching of this invention that a rapid transition from a condition of low power demand to some other condition of high power demand may best be accoraplished by the rapid injection of working fluid into the working volume in the form of a virtually incompressible liquid.
• a power level control subsystem is comprised by a servoactuated variable displacement hydraulic pump 30, a power demand control mechanism or accelerator 32, free piston 34, fluid reservoir 35, reservoir cooler 36, and a plurality of Stirling cycle engine coolers 24.
• pump 30 forces hydraulic fluid 31 into reservoir 35 which in turn forces piston 34, sealed by oring 33, to move to the right.
• This action causes the rapid injection of condensed liquid working fluid 37 into the working volume at points of entry contiguous with coolers 24.
• the change in mean operating pressure is immediate, because the introduction of nearly incompressible liquid medium in this manner instantly lowers the total working volume available to the gaseous medium.
• Each engine cooler 24 is maintained at a temperature sufficiently low for good Stirling-cycle thermodynamic efficiency, but at a temperature somewhat above Tc so that its function from the standpoint of power control is always that of an evaporator.
• reservoir cooler 36 and therefore revervoir 35 must be maintained at a temperature somewhat below Tc so that its function is always that of a condenser.
• the pressure in reservoir 35 is the saturated vapor pressure of the condensed working fluid at that temperature.
• the closed cycle Stirling prime mover operates on the basis of the difference in temperature in the working fluid between the hot expansion space and the cold compression space, the development of useful power output is not specific to the source of heat available for use. Therefore the design of the heat source can be any one of a large variety of possible types.
• a rather simple combustion system can be produced, for example, which will cleanly and efficiently burn various kinds of both liquid fuels and gaseous fuels without any modification whatsoever.
• a single prime mover may be made to operate on regular or premium gasoline, diesel oil, alcohol, crude oil, lubricating oil, olive oil, vegetable oil, propane, butane, natural gas, and synthetic coal gas.
• automotive prime movers marine prime movers, aeronautical prime movers, astronautical prime movers, industrial prime movers, military prime movers, agricultural prime movers, multifuel prime movers, nonfuel prime movers, portable prime movers, biomedical prime movers, refrigerators, air conditioners, cryogenic cooling engines, residential heat pumps, industrial heat pumps, military heat pumps, water coolers, air compressors, other gas compressors, re mote electric generators, portable electric generators, stationary electric generators, hydroelectric power converters, nuclear power converters, radioisotope power converters, solar power converters, geothermal power converters, ocean thermal power converters, biomass power converters, solid waste power converters, small cogeneration power plants, large cogeneration power plants, remote fluid pumps, portable fluid pumps, stationary fluid pumps, remote power tools, portable power tools, outdoor power tools, underwater power tools, toys and novelties.

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• 1982
  • 1982-05-14 DE DE8282902015T patent/DE3275577D1/de not_active Expired
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  • 1982-05-14 WO PCT/US1982/000651 patent/WO1982004101A1/fr active IP Right Grant
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  • 1982-05-14 DE DE8282902016T patent/DE3279652D1/de not_active Expired
  • 1982-05-14 EP EP19820902016 patent/EP0078848B1/fr not_active Expired
  • 1982-05-14 WO PCT/US1982/000648 patent/WO1982004098A1/fr active IP Right Grant
  • 1982-05-14 WO PCT/US1982/000649 patent/WO1982004099A1/fr active IP Right Grant
  • 1982-05-14 EP EP19820902015 patent/EP0078847B1/fr not_active Expired
  • 1982-05-14 EP EP82902018A patent/EP0078850B1/fr not_active Expired
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