Patent Grant
10982543
The present application is a National Phase of International Application Number PCT/US2017/021900, filed Mar. 10, 2017, and is related to International Application No. PCT/US2009/031863 filed Jan. 23, 2009 which designates the United States and claims priority to U.S. Provisional Application No. 61/022,838 filed Jan. 23, 2008 and U.S. Provisional Application No. 61/090,033 filed Aug. 19, 2008, and Provisional Application No. 61/366,389 filed Jul. 21, 2010 and U.S. Pat. No. 8,156,739 issued Apr. 17, 2012. The present application is further related to U.S. Provisional Patent Application No. 62/118,519 filed Feb. 20, 2015. The entire disclosure of all of the above listed PCT and provisional applications is expressly incorporated by reference herein.
The entireties of related U.S. Pat. Nos. 4,698,973, 4,938,117, 4,947,731, 5,806,403, 6,505,538, U.S. Provisional Applications Nos. 60/506,141, 60/618,749, 60/807,299, 60/803,008, 60/868,209, and 60/960,427, and International Applications No. PCT/US2005/036180, PCT/US2005/036532 and PCT/US2016/018624 are also incorporated herein by reference.
The most efficient heat engines up to this disclosure, Stirling engines, invented 200 years ago, lose 30% efficiency because they expand and compress their internally cycling working fluid from the volumes incasing their heating exchanger and cooling reservoir, and hence their fluid is heated and cooled near-isothermally during the strokes so that some of the added heat cannot be fully converted to its full work output potential.
Ever since, thermodynamic specialists have sought ways to retrieve this balance. The Second Law states that heat always flows from a higher to a lower level. Some specialists have confused this quest to retrieve the balance by misinterpreting the Second Law of Thermodynamics to mean a fluid cannot be cycled from a low to a high energy level. In fact, to be near-adiabatic, a bolus of cycled working fluid must be cycled to a higher level before being reheated, batched back into the engine and expanded. This disclosed near-adiabatic engine does not pass its heat from a low to a high level, breaking the Second Law. Rather its working fluid is cycled from a lower pressure condition to a higher pressure condition in a balance of forces much like a boat passes through a canal lock. When raised, in this disclosure, the raised level is used to power the next downstroke (expansion stroke). But, after cycling, heat is added to that cycled fluid from an outside source.
Overall thermal efficiencies of typical four-stroke spark-ignited piston engines are in the ˜20-30% range while four-stroke diesels achieve 30-40% range. The primary source of inefficiency in these engines is the loss of sensible enthalpy in the exhaust. This is less of a problem in closed cycle engines such as Stirlings where efficiencies of up to ˜38% have been demonstrated in automotive applications. However, the performance of these engines suffers from the fact that a significant portion of heat is added during the power-stroke (expansion phase of the cycle) and during the recompression phase, thus increasing the entropy during the cycle. This effect is a direct consequence of how the displacer piston transfers fluid between the working cylinder and the hot and cold reservoirs. Hundreds of billions of dollars-worth of heat energy could be converted into electricity every year, if a cost-efficient heat-driven generator is developed. The Carnot principle indicates that a set amount of energy is available within a given temperature range that can be converted from heat to power if a way can be found to efficiently convert it.
In one or more embodiments, this near-adiabatic heat engine comprises a working chamber, a power piston and a fluid pump volume. The power piston is moveable within the working chamber and the forces are united by the rotational inertia of a flywheel, running on working fluid in a high-pressure state receivable from a heating exchanger and cooled in the cooling reservoir. Six improvements are herein claimed:
1) A simplified pumping means wherein the diaphragm means of pumping (previously disclosed) is eliminated and replaced with the power piston means of pumping, the action occurring within the working cylinder. The working piston becomes both the power piston and the pump piston, both moveable within the working cylinder, wherein the quantity of the fluid in the expansion chamber, the quantity of fluid in the pump chamber and the quantity of fluid in the working chamber are determined by the positioning and sequential operation of the inlet valve between the hot heat exchanger and expansion chamber, and the connecting valve between the working chamber and the cooling reservoir, but the pumping cycle is driven by the action of the working piston.
2) Using a simplified valve means of opening the inlet valve from the hot heat exchanger, the inlet valve is mounted on the valve frame casing that is driven by the bevel gear train that is driven by the belt connection to the main drive shaft. The inlet valve herein is shown with five slits. The inlet valve opens five times with each rotation of the valve frame. The valve frame rotates six (6) times per second that means the valve opens 30 times a second or 1800 rpm. The inlet valve opens to fill the expansion chamber and shuts to allow the expansion chamber to expand near-adiabatically.
3) Using a simplified valve means of interconnecting the volumes between the engine working chamber and the cooling reservoir, the connection valve also is mounted on the valve frame casing and opens with the same number of sequences. That valve opens when the working piston is at Bottom Dead Center (BDC) and closes immediately before defining the pump volume during the upstroke. This connecting valve opens to allow pressurize working fluid in the cooling reservoir to be released when the working piston is at BDC and the valve stays open until the working fluid in the working chamber is recompressed into the cooling reservoir (and into the pump volume), and closes immediately before defining the pump volume so as to capture that recompressed working fluid in the cooling reservoir for the next cooling of the next expanded working fluid at the end of the next downstroke.
4) Using a means of disconnecting and reconnecting the flow between the hot heat reservoir and the engine itself, this valve is placed between the engine and the hot heat exchanger to prevent flooding of the engine with high pressure/temperature working fluid when the engine is not in operation. The valve caps off both access of the hot heat exchanger working fluid to the engine and it caps off the return of fluid from the engine. When the engine is stopped and is capping off the flow, flow is allowed to bypass the hot heat exchanger and be cycled directly back into the engine for easy startup. One embodiment would be to use an electronic zone valve.
5) Herein described is a means of rapidly cooling the working fluid in the cooling coils within the cooling reservoir by spraying a cold coolant on those cooling coils, creating rapid absorption of heat by creating a phase change within the cooling reservoir. The cooling coils are encased inside the cooling reservoir. A cold mist is sprayed out of multi opening directly onto the cooling coils, causing a phase change in the cooling reservoir that will rapidly absorb an immense quantity of heat. The coolant is fed into a liquid chamber and is sprayed to easily vaporize when in contact with the cooling coils. The fluid becomes a vapor and is forces with the rapid expansion out of the cooling reservoir where it again condenses into a liquid and is either recycled or used in other furnace room appliances as a booster as heat is needed.
6) Herein discloses is a means of snap-shutting the valve openings that are mounted on the valve frame to optimize flow through the inlet valve to the engine and to interconnect through a valve the fluid in the working chamber and the cooling reservoir within the engine. The inlet valve and connection valve described are designed to stay open until the point to snap shut. This delay in shutting and snapping shut optimizes the flow through the valves and thus the point of defining the expansion volume filled through the inlet valve and the point of defining the pump volume when the connection valve between the working chamber and cooling reservoir snaps shut. The large bevel gear swivels on the same axis as the valve frame casing that houses the inlet and connecting valves. The mechanism swivels only a couple of millimeters and is spring biased for rapid closing action at the point of closing to define the expansion volume and pump volumes.
Because this near-adiabatic engine has already used a flywheel as previously disclosed, the means for the cycling of the working fluid (previously using a diaphragm) was discovered to be redundant. Because the flywheel will even out the forces acting on the working piston occurring during the filling of the expansion volume and the emptying of the compression volume, in the same way the forces acting on the diaphragm were evened out within the balanced pressure environment surrounding said diaphragm, the dual actions essentially balance out as the forces filling the expansion chamber and emptying of the pump chamber during the cycle are nearly equal, as was taught by the issued patents. This simplification became apparent, when the engine was put into a running mode while operating in its virtual dynamic model. Thus, in fact, the diaphragm will be eliminated and replaced by the action of the working piston itself and alone. Said again, the filling of the expansion volume and the emptying of the pump volume are found to be connected, through their common connecting rod and driveshaft to the flywheel and their forces are essentially balanced out in the cycle, duplicating the forces that were before acting on the diaphragm as previously disclosed.
Regarding the working fluid, for this disclosure, air is used in this technical analysis. However, helium would be the working fluid for optimum heat to work conversion. Helium gas is suitable as an ideal working fluid because it is inert and very closely resembles a perfect gas, therefore providing the optimum heat to work conversion. Also, although volatile, hydrogen has been used. Its boiling point is close to absolute zero, improving its Carnot potential, but its atoms are small and may cause leakage problems. The greater the viscosity, the less leakage will occur. Other suitable media include, but are not limited to, hydrogen and carbon dioxide.
The described embodiments are illustrated by way of example, and not by limitation, in the figures of the accompanying drawings, wherein elements having the same reference numeral designations represent like elements throughout, unless otherwise specified.
In the following detailed description, for purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of the specifically disclosed embodiments. It will be apparent, however, that one or more embodiments may be practiced without these specific details. In other instances, well-known structures and devices are schematically shown in order to simplify the drawing.
A near-adiabatic engine has four stages in a cycle: (1) a means of near-adiabatically expanding the working fluid during the downstroke (expansion stroke); (2) a means of cooling the working fluid at Bottom Dead Center (BDC); (3) a means of near-adiabatically compressing that cooled fluid from the lower pressure/temperature level at BDC to the higher level at Top Dead Center (TDC); and finally, (4) a means of passing that working fluid back into the high pressure/temperature source in a balanced condition with minimal resistance to that flow. This disclosure builds on lessons learned in stages (1), (2), (3), and (4) which were patented in U.S. Pat. No. 8,156,739 issued Apr. 17, 2012 and in PCT/US2016/018624, and include improvement regarding the operation of the valves, the cooling means for the cooling reservoir, and a shutoff between the hot heat exchanger and the engine when the engine stops. This disclosure describes a simplified means of cycling the working from pump volume to the hot heat exchanger and to inject the bolus from the hot heat exchanger into the expansion chamber before near-adiabatic expansion.
As to comparing the Stirling engine with the herein disclosed near-adiabatic engine, experts in thermodynamics have long known that the ideal cycle is “adiabatic,” meaning that the stroke occurs without gain or loss of heat and without a change in entropy so that, during the process of expansion and recompression, all the energy within the given temperature bracket is given out as power or returned to the closed system. Such an adiabatic engine is sometimes referred to as a Carnot engine which receives heat at a high absolute temperature T1 and gives it up at a lower absolute temperature T2, with its optimum efficiency potential equaling (T1−T2)/T1.
The first law of thermodynamics (law of conservation of energy) states that the change in the internal energy of a system is equal to the sum of the heat added to the system and the work done on it. In this disclosed near-adiabatic engine, the heat in and out is proportional equal to the work out and in, proportionally recognizing the Carnot limit of the temperature range. The second law of thermodynamics states that heat cannot be transferred from a colder to a hotter body within a system without net changes occurring in other bodies within that system; in any irreversible isothermal process, entropy always increases. In other words, in a perfect cycle, heat in and out is equal to work out and in, as stated above, but, of course within the Carnot limits. But Stirlings, operating at a constant high and a constant low, will experience an entropy increase and decrease.
However, an ideal adiabatic stroke is reversible. Thus, heat potential can be converted into work output, and work input can be converted back into heat potential, ΔQ=ΔW. Work output of the engine results from utilizing the higher heat capacity of the nearly adiabatic downstroke as compared to the lower heat capacity for the near-adiabatic upstroke, i.e., reversible expansion for work output is countered by anti-work input after the heat removal at BDC. The heat removal is bringing the pressure/temperature conditions in the working chamber at BDC down to an ideal sink level before recompression.
The innovation advances the efficiency beyond cutting-edge Stirling engines by 20%. Stirlings have nearly isothermal cycles, meaning they operate at a constant high and constant low temperature within their respective working chambers. In the disclosed near-adiabatic engine, the working fluid is pumped from the low to the high temperature/pressure levels. Thus, the working fluid is circulated, while, in Stirling engines, the working fluid is pressed back and forth within the common containment of the engine and heating exchanger and cooling reservoir. In circulating the fluid from a low to high level in a near-adiabatic engine, the disclosure shows the batching of the working fluid, shows that that batch is isolated and expanded in isolation, extracting the optimum energy out of that fluid and converting it into work output.
The herein disclosed near-adiabatic engine, a closed cycle engine, greatly reduces the heat loss by using a patented mechanism (consisting of a rotating valve acting in conjunction with the motion of the piston) to rapidly introduce hot working fluid into a conventional piston-cylinder with minimal pressure loss. Enough mechanical separation is present between the hot and cold reservoirs and the expansion/compression components that the expansion and compression processes occur nearly adiabatically. The net effect is that the disclosed process approximates more closely the near-adiabatic cycle than other engines, the idealized heat addition and expansion processes associated with the Carnot cycle. Thus, it is inherently more efficient.
How the Near-Adiabatic Engine Works
Of course, Spark Ignition engines are powered by the pulse of the controlled explosion in the working chamber and throw off their expended hot gases after that controlled SI explosion. The disclosed near-adiabatic engine, unlike Stirlings, is a closed system which is powered by the work differential between the positive work caused by the high temperature/pressure expansion downstroke (Points 1 to 2) and negative anti-work caused by the cooling/recompression upstroke (Points 3 to 4). With the disclosed engine, these cyclical expansion and recompression strokes occur nearly adiabatically within the same working cylinder, and are possible because two displacement volumes open and close during the cycle at Top Dead Center (TDC), Point 1 (the expansion volume opens after the pump volume has closed) and at Bottom Dead Center (BDC), Point 2 (the expanded volume is cooled before the upstroke). Remembering that adiabatic means all the energy within the given temperature bracket is given out as power or returned to the closed system, two conditions must be met to achieve an adiabatic cycle: 1) The working fluid must be cycled from its low to high heat/pressure source with low mechanical losses, solving “Maxwell's Demon” issue; and 2) The working strokes must expand and recompress in isolation, hence adiabatically. Cycling of the working fluid from the low to high pressure happens because the work caused by filling the expansion volume balances with the anti-work caused by emptying the pump volume which are directly connected and balanced by the unifying force of the flywheel. A critical feature of the cycle is the cooling of the working fluid at BDC. During the entire upstroke (Points 3 to 4), the expanded working fluid is internally completely squeezed out of the working chamber (which includes the expanded volume and pump volume) into the cooling reservoir and simultaneously compressed into the pump volume, and then out of the engine into the hot heat exchanger. All three volumes—the working chamber, the cooling reservoir, and the pump volume—share the same pressure condition. At TDC, the fluid is pressed (cycled) out of the engine into the hot heat exchanger before the next injection of an equal quantity of hot working fluid into the opening expansion chamber.
As previously disclosed, the expansion chamber and the working chamber fluidly communicate as one volumetric unit. As previously disclosed, the expansion volume is near-isothermally filled. That volume was also monitored by the point of closing the inlet valve between the hot heat exchanger and the expansion chamber. As previously disclosed, the remaining downstroke, or expansion stroke, the working fluid is near-adiabatically expanded until the working piston reaches near Bottom Dead Center (BDC) in which that working fluid (Stage 1) is nearly fully expanded. Consistent with the previous patent, after the expansion downstroke, a means was disclosed in the previous patent of cooling the expanded working fluid at BDC (Stage 2). As previously disclosed, the working chamber is controllably, fluidly communicable with the pump chamber during the compression upstroke of the power piston for near-adiabatically compressing the cooled working fluid from the low pressure state into the higher state into the pump chamber, volume (Stage 3), while, in the cooling reservoir, simultaneously near-isothermally compressing the balance of fluid back into the cooling reservoir, thus removing heat and containing that cooled fluid to be released at the bottom dead center position (BDC) of the next cycle. BDC cooling is achieved, as previously disclosed, by: a) a disclosed means of, during the previously compression upstroke, compressing a portion of the fluid that is in the working chamber into the cooling reservoir during the upstroke so that its fluid was near-isothermally cooled, b) a disclosed means of containing that fluid during the sequent downstroke, expansion stroke, and c) a disclosed means of releasing that fluid at BDC into the working chamber, supercooling the expanded working fluid before recompression. So, after BDC cooling, the disclosure also teaches a means of achieving near-adiabatic compression during the upstroke into the pump volume (stage 3) that will ensure that the same quantity of fluid that is pressed into the pump volume is an equal quantity of fluid as compared to the initial volume of the bolus that was initially injected at Top Dead Center (TDC) into the expansion chamber from the hot heat exchanger as described in previous patents.
The balance of forces in the pumping process is achieved by balancing the near equal work acting on the common piston due to the pressure in the expansion chamber and counter balanced by the pressure caused during the pumping process. The balance of forces is created by the unifying common rotational inertia of the flywheel itself acting on the working piston. The flywheel (as shown in previous patents) is now incorporated directly into the pumping action, allowing the transfer of cycled fluid to be pressed from the lower pressure state in the pump chamber back into the high-pressure state in the heating exchanger (stage 4), completing the cycle.
In summary, this disclosure teaches this above format and teaches a means of an improved the inlet valve and the connecting valve, teaches a means of isolating the engine cycling process from the hot heat exchanger during start up for easier startup turnover, teaches a means of efficiently cooling in the fluid in the cooling reservoir by spraying a coolant fluid mist, such as cool water or ammonia/water, over the cooling coils to optimize the heat removal by creating an optimum phase change condition in the cooling fluid thus optimally the removal of heat, and teaches a means of snap closing the inlet valve and connection valve of the valving mechanism. This disclosure also recognizes that the valving means can be electronically actuated.
Why the Engine is Near-Adiabatic
Reason 1—As taught in previous patents, the expansion chamber is filled and expansion downstroke is near-adiabatically expanded because the working fluid 703 is isolated before that expansion (Stage 1).
Reason 2—At BDC, the appropriate amount of heat used during the downstroke work output is removed by injecting the cold fluid from the cooling reservoir 600 (Stage 2). Actually, the appropriate heat removal amount must be sufficient to achieve the near-adiabatic upstroke within the temperature high to low range. In the previous upstroke, heat in the cooling reservoir 600 was near-isothermally removed by the previous compression of that fluid into the cooling reservoir 600 during the previous upstroke (from Point 3 to 4, Stage 3). And the balance was near-adiabatically compressed into the pump chamber 701 for recycling. During the next downstroke from TDC to BDC, this retained, compressed, cooled fluid in the cooling reservoir 600 is released into the working chamber 104 at BDC, supercooling the expanded working fluid 703, bringing the mean temperature/pressure down to the ideal low temperature/pressure level (Stage 2). Thus, after being accessed to the working chamber 104, the BDC temperature and pressure approach the ideal Carnot bracket level.
Reason 3—The pre-access BDC and post-pressurized TDC conditions within the cooling reservoir 600 are the same. When determining the p-V work input ΔW=ΔFΔd, the upstroke length Δd (from points 3 to 4, Stage 3) is the same. In the temperature bracket of 922° K to 294° K range, the temperature in the cooling reservoir 600 remains a near constant 294° K with its density rising to 1.9094 times the density in the high energy pump, balancing the pressure buildup (Δp) in the pump, matching the progressive buildup of force (ΔF) required to achieve an ideal adiabatic upstroke.
Reason 4—At TDC, the working fluid 703 passes back from the pump volume into the hot/high pressure heat exchanger 500 balancing the force (work) against the force (work) caused during the filling of that working fluid into the expansion chamber. The balance of forces is caused by the rotational inertia of the flywheel acting on the common piston.
The Near-Adiabatic Cycle
The following was prepared by the Department of the Aerospace Engineering, University of Maryland, in explaining the operation of the engine. The near-adiabatic cycle is a closed thermodynamic cycle that makes use of three fluid volumes: the hot reservoir, the working cylinder, and the cold reservoir, noting that the expansion and pump volumes are now combined within the working chamber to comprise the working cylinder volume. Valves alternately connect each reservoir to the working cylinder in a way that causes the working fluid to be cycled and the piston to be driven up and down.
Graph 1 a and b illustrate the variations of pressure and temperature in the three volumes over the course of a cycle. Beginning at bottom dead center (BDC) or 180 crank angle degrees (CAD), the piston moves upward compressing the working fluid in the cylinder. Fluid in the cold reservoir is also compressed because the cold reservoir spool valve separating the cold reservoir and working cylinder is open. The inlet valve closes around 280 CAD trapping cooled working fluid in the cylinder. The upward motion of the piston compresses the trapped, cool, fluid until its pressure reaches that of the hot reservoir around 340 CAD. At this point, one-way reed valves at the top of the cylinder open allowing the cooler working fluid to flow into one end of the hot reservoir labyrinth. These valves close when the pressures in the cylinder and hot reservoir equalize at top dead center (TDC, 360 CAD).
The inlet valve, separating the other end of the hot reservoir labyrinth from the cylinder, opens immediately after TDC admitting hot, high pressure working fluid from the hot reservoir to the volume above the piston. This gas begins to expand pushing the piston down. The hot reservoir inlet valve closes shortly thereafter (at ˜380 CAD) and the bolus of hot working fluid trapped in the cylinder continues to expand doing work on the piston. The cold reservoir connection valve opens near bottom dead center (BDC, ˜40 CAD) allowing cool working fluid from the cold reservoir to enter the cylinder and mix with the expanded fluid from the previous cycle. The cold reservoir connection valve closes ˜100 CAD after BDC and the cycle repeats. Graph 1b shows that the temperatures of the hot and cold reservoirs change very little (<5%) over the course of the cycle indicating that heat addition and removal processes are nearly isothermal as in the Carnot cycle. Graph 1c shows the p-V diagram for the fluid in the working cylinder. Finally, it should be noted that the crank angle resolution in Graph 1 has been degraded intentionally to facilitate the creation of the annotated plots. The ‘real’ pressure and temperature traces produced by the model are much smoother. Referring to the drawings in
The intake and exhaust ports at the top of the cylinder connect, respectively, to the outlet and inlet ports of a shell and tube heat exchanger. The ‘hot reservoir’ is the internal volume of the ‘tube’ portion of the heat exchanger plus the volume of the connections between the exchanger and the engine. The shell of the cold side heat exchanger has been removed to expose the tubes whose internal volumes form the cold reservoir. The figure also shows the valves separating the reservoirs from the working cylinder. Reed valves at the top of the cylinder prevent backflow from the hot reservoir (which is at elevated pressure) into the cylinder. A cylindrical rotary valve isolates the cold reservoir from the working cylinder at the appropriate points in the cycle. A circular plate rotary valve at the top of the working cylinder opens to permit flow from the hot reservoir to the working cylinder at appropriate points in the cycle.
Modeling Results
A control volume approach applied to the hot reservoir, cold reservoir, and working cylinder is used to develop a quasi-one-dimensional model of the engine's performance. Pressure losses associated with the flow of fluid through various tubes and orifices are accounted for using correlations that are appropriate for the geometries of the flow passages shown in this disclosure. Similarly, heat transfer in the hot and cold reservoirs is modeled using empirical correlations for the performance of shell and tube heat exchangers. The time-dependent conservation equations (mass and energy) are integrated using a standard Runge-Kutta integrator (MATLAB's ODE45). Inputs to the calculations include initial pressures and temperatures in the three volumes at a particular crank angle, the hot and cold reservoir volumes (VHR, VCR), displacement, clearance volume (Vc), compression ratio (rc), crankshaft speed, and the inlet temperatures of the hot and cold reservoir heat exchangers. The latter refer to the temperatures of the fluids entering the hot and cold side heat exchangers from the outside (i.e. The external temperature difference that the engine operates between) and not the temperatures of the hot and cold reservoirs themselves which lie inside the heat exchangers and thus will be at intermediate temperatures relative to the external temperature difference.
The simple thermodynamic model was used to identify designs that maximize power, efficiency, or Brake Mean Effective Pressure (BMEP). Over 4000 combinations of compression ratio (4<rc<30), hot reservoir volume (0.5rcVc<VHR<50rcVc), cold reservoir volume (0.5rcVc<VCR<50rcVc), and cold reservoir initial pressure (0.5<pC,i<8 Mpa) were explored (see Graph 2). The hot and cold reservoir temperatures were fixed at 1000K and 300K respectively to reflect realistic operating temperatures and hot and cold reservoir volumes were fixed at 0.036 m3 to reflect practical constraints on device size. Note that other work showed that VH/Vc˜1 is about optimal. Engine speed was held constant at 1800 RPM corresponding to a four-pole A/C generator operating in 60 Hz grid. The results show that a compression ratio of 12 and VH/VC=1 maximizes power output for an engine with the specified hot and cold reservoir temperatures and volumes. The optimum engine satisfying these constraints produces 5.9 kW with 28.5% efficiency. Sample p-V and T-S diagrams for the cycle are presented in Graph 3.
Referring to
Similar methods can be used to identify configurations that maximize efficiency. Graph 4 shows that efficiencies in excess of 50% are attainable in designs that produce useful levels of power output using only a moderate temperature difference. Increasing the hot reservoir temperature significantly improves performance while increasing speed increases power for a while but at the expense of efficiency. Since the work/stroke decreases with speed (because the rate of heat transfer in the heat exchangers cannot keep up), power output peaks at about 3700 RPM and decreases with further speed increases. Graph 4 summarizes the levels of performance that are available from this size engine operating between 1000K and 300K when the engine is optimized for either power output, efficiency, or BMEP.
Refer to
The Valving Interchange of the Working Chamber and the Flow Capacity of the Disclosed Model
The opening of the inlet valve 121 must provide optimum flow from the hot heat exchanger 500 to the expansion chamber 702 in the working cylinder. Therefore, a delay means that allows the valve to rapidly snap shut will be designed into the valve mechanism. The featured model is designed with bevel gears 151 and 152, having a ⅕ ratio, meaning the valve frame 130 will rotate one time in five rotations of the crankshaft 141. The valve frame has five openings, meaning that the valve will open once per rotation of the crankshaft 141. The pulley ratio between the valve pulley 806 and the crankshaft pulley 143 is 1/1. Four valving mechanisms interact with the working chamber volume 104: 1) the valve frame 130 with its five inlet valves 121 allows for the timed TDC injection from the hot heat exchanger 500; 2) the BDC port opens when the working piston 103 nears the BDC position and uncovers the BDC ports, exposing access of pressurized cold fluid from the cooling reservoir 600 to the working cylinder 104 (in tandem with the opened valve 122); 3) the valve 122 between the working chamber 104 and the cooling reservoir 600, located at the TDC position right before the pump volume, will remain open during almost the entire near-adiabatic portion of the upstroke, allowing the fluid in the working chamber 104 to be compressed back into the cooling reservoir 600. This valve will also be designed to rapidly snap shut; and 4) the unidirectional check valve 126 accesses flow from the pump chamber volume 701 to the hot heat exchanger 500, providing unidirectional flow out of the engine 400 through the pump chamber volume 701 back into the high pressure/temperature hot heat exchanger 500.
The Engine Valves:
1) The upper portion of the rotating valve frame 130 houses inlet valve 121 which has five (5) slit openings, spaced equal distance around the valve frame circumference, moving within the walls of the valve mechanism 130. At 1800 RPMs, the valve frame 130 with its five slits rotates one complete rotation per five rotations of the crankshaft. Since the gear ratio for the bevel gear is ⅕, as explained and since the belt pully ratio between the cam and crankshaft is 1 to 1, the valve frame rotates (at 1800 RPM) 30 seconds/5:1 ratio=6 times a second. The projected total opening will be 15.56 cm2. However, designing into the valve mechanism a means of snap closing the valve will ensure that the nearly isothermal (filling of the expansion volume) and near-adiabatic expansion downstroke distinction will be sharper. As such, if the required openings do not need to be generous, the impact of a tighter cosign on the TDC action would improve. For example, if the TDC action straddles TDC with a 15 degree approach and a 15 degree descent, the cosign would be 15 degree Cosign=96.6% for the near-adiabatic expansion. But, if the timing of the TDC opening is reduced to a 11.84 degree Cosign, the system would improve to a 97.9% near-adiabatic range.
2) Approaching BDC, BDC ports 124 allow the rapid flow of the pressurized cold fluid in the cooling reservoir 600 back into the working chamber 104. With a 30 degree rotation of the crankshaft 141 at BDC and with a 7 mm tube diameter, each opening would have a 38.5 mm2 opening aperture. 38.5×30 openings would be a total of 11.55 cm2 which is a 1.8 in2 opening. If the rotation range at BDC has a tighter cosign angle, this would decrease the time exposure of the opened ports 124 at BDC but would improve the engine efficiency.
3) The upper ports between the working chamber 104 and the cooling reservoir 600 (located right before the pump volume) are shown with a 23.56 cm2 maximum aperture opening. Designing into the valve mechanism as a snap closing means will sharpen the distinction between the near-adiabatic upstroke and the pumping of the working fluid from the pump volume 701 into the hot heat exchanger 500. If the rotation range at BDC has a tighter cosign angle, this would decrease the time exposure of the opened ports 124 at BDC but would improve the engine efficiency.
4) The check valve 126 from the pump chamber volume 701 to the hot heat exchanger provides unidirectional flow out of the engine.
The Containment Furnace
This disclosure shows the previously patented design of a containment furnace that provides the heat that drives the disclosed engine 400 and its generator. Encased inside a light-weight silicone shell material, the furnace 900 uses an interior conventional heat exchanger 500 to feed heat to the engine 400. The furnace 900 is fired up using a conventional furnace gas/air nozzle 903. However, previous disclosures of the engine concept include several other heat exchanger options for its multi-application uses. Heat is drawn off the interior heat exchanger 901 (the heat exchanger 500) as the engine receives its boluses of hot working fluid 703, driving the engine cycles. As that fluid cycles, its heat energy is converted to work output, and is returned to the containment furnace 900 for reheating through port 123 from the engine 400 to port 905 of the furnace. In the home furnace configuration, any fumes exhausted from the containment furnace 900 pass through the exit flue 906, and flow into and through the hot water heat and HVAC as needed (see
Preventing Engine Lock when Idle
The containment furnace is shown so as to explain that, when the engine stops, unavoidable leakages will seep into and out of the internal volumes of the engine 400—into and out of the working chamber volume 104, of the cooling reservoir volume 600, of the expansion chamber volume 702, and of the pump chamber volume 701. These leakages will allow the high pressure fluid in the hot heat exchanger 500 to flood the system. When this happens, when the working fluid 703 in the engine 400 is not in its cycling mode, the engine 400 will tend to lock up. To prevent such lockage, a bridge valve 201 between the expansion chamber 702 and the engine 400 will close off at ports 203 and the access of the high pressure/temperature working fluid when the engine stops. However, as the bridge valve closes, a loop is opened allowing flow through the loop port 202 from the exhaust back into the engine so that the engine can be easily turned over to gain momentum. When the engine does gain momentum, the bridge valve opens. This will minimize the resistance of internal pressures within the engine during startup.
The initial intended use of the near-adiabatic engine 400 and its disclosures is for generating electricity in the home. The near-adiabatic engine 400 is designed to drive a gas-driven home generator 1000. Any heat-driven home generator, that shares its heat with other furnace room appliances, will achieve exceptional efficiency, but, with a highly efficient Combined Heat to Power (CHP) engine such as disclosed, the cost-efficiency should triple. As shown, the disclosed gas-driven engine 400, driving a home generator, integrated into the home HVAC and hot water heater, is projected to achieve as much as 46% efficiency. This disclosed CHP engine, drawing its heat from a containment furnace 900 between 1230° F. and 742° F., with the heat flow through the furnace 900 controlled so as to optimize the system efficiency, further ensures that nearly all the heat will be converted into usable energy. Overlapping and sharing heat between the near-adiabatic CHP unit and other furnace room appliances will ensure that little additional heat will be required above the winter consumption of central heating and the summer consumption for cooling. As a point of interest, the average summer cooling requirement is ˜⅓rd that of the required heat for winter.
Small lawnmower and aviation SI engines, like Honda's Freewatt, are only 21.6% efficient. The WhisperGen, a Stirling engine, is awkwardly designed and achieves only 15% efficiency. Larger engines are generally more efficient. A four-cylinder Kockums, for instance, with 25-kW power, if reconfigured as a one-cylinder engine, would suffer ¼th the internal losses while generating 25/4 kW the power, approximately 6-kW power. The single-cylinder engine 400 herein disclosed, sized to the Kockums with a flywheel and an efficient alternator generator serving both as an engine starter and a generator, having 20% greater efficient, would have 7.5-wK power. A 2-kW Gas-Tricity generator for homes with a nearly adiabatic cycle, 20.1% mechanical and 5% thermal losses, and a projected 46% efficiency, would require 2.67-kW heat conversion.
Other Intended Applications for the Engine
Broader heat-to-work conversion needs will be met as other applications of the engine enable for cheaper generation while reducing greenhouse emission. Optimized heat-to-power conversion will reduce energy consumption, thus reducing greenhouse emissions. The focus in this patent is on developing the practical near-adiabatic engine design for the Gas-Tricity Home Generator. So far, the breakthrough has identified five heat-to-power engine applications. Projections show:
1) savings herein described associated with the GTHG,
2) savings in electricity generation from high-grade industrial waste heat of 2.882 GW year, costing $615.7 million compared to nuclear power plant generation at $13.7 billion or 23 times more cost-efficient;
3) thermal-solar savings, using the same solar array but in small engine clusters, replacing the 18% efficient Ivanpah 392 MW steam turbine with multi 46% efficient 1.1 MW versions of the near-adiabatic CHP engine units, the plant cost-efficiency can improve 2.5 times;
4) savings from distributed generation for large buildings parallels the savings using the GTHG; and
5) cars can get 80 mpg.
During the first two years of GTHG commercialization, if 5,000 homes are built containing the GTHG, their homeowners will save a total of over $1.6M per year on utility bills, and its environmental impact on the environment would aggregate removal of 25,000 tons of CO2 from the atmosphere (equivalent to removing 3,582 cars from the road).
The volumes are defined and distinguished by the sequence of the opening and closing of the inlet 121 and connecting 122 valves. For example, the opening of the inlet valve 121 at the beginning of the downstroke near-isothermally feeds hot working fluid into the opening expansion volume 702. When that inlet valve 121 is closed, the downstroke becomes the near-adiabatic expansion downstroke of the work output during cycle. Likewise, the upstroke is the near-adiabatically compressed portion of the work input as long as the connecting valve 122 between the cooling reservoir and working cylinder is open. When that connecting valve closes, the remaining volume in the working cylinder become the pump volume 700 during the upstroke to TDC and thus defines that pump volume and becomes that pump volume (filled with working fluid) that is pressed near-isothermally back to the high pressure/temperature level of the hot heat exchanger.
| Filing Document | Filing Date | Country | Kind |
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| PCT/US2017/021900 | 3/10/2017 | WO | 00 |
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|---|---|---|---|
| WO2018/164696 | 9/13/2018 | WO | A |
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