Patent Application
20100288248
This invention relates to a hybrid engine that combines together an internal combustion engine and an external combustion engine. The external combustion engine may be a steam engine.
A hybrid engine is one in which more than one prime mover contributes power to a single power output. Hybrid engine technology is currently a field of active research and development in the effort to improve the fuel efficiency of heat engines where a heat engine is a device capable of converting heat into mechanical work. An internal combustion engine is a typical heat engine.
The ratio between the energy input to the engine, measured as the calorific value of the fuel multiplied by the rate of fuel flow, and the work output from the engine is called the thermal efficiency. The thermal efficiency of a reciprocating internal combustion engine, such as an automotive engine, may be of the order of 30-40%. Thus 60-70% of the energy contained in the fuel is wasted. This wastage may partly be heat rejected by the engine, which is typically inherent in the functioning of heat engines, partly mechanical friction inside the engine and partly noise emitted by the engine.
Heat rejected may typically appear as:
Waste heat from internal combustion engines may sometimes be used for heating the interiors of buildings and vehicles but, especially in the case of automotive engines, the proportion of the total heat wastage used for this purpose may typically be very small.
Exhaust gases may typically leave the cylinders of a reciprocating internal combustion engine at temperatures of the order of 1,000° F. Their final exit temperature from the exhaust pipe may be of the order of 100° F.
In a reciprocating steam engine, steam may typically enter the cylinders at temperatures of the order of 500-700° F. and leave the engine at temperatures of the order of 250° F. The temperature range in which a steam engine functions may therefore lie within the range between the initial and final exhaust gas temperatures of a typical internal combustion engine.
A hybrid engine could therefore comprise a primary internal combustion engine with a secondary steam engine using the primary engine's waste heat and adding to the hybrid engine's power output and thermal efficiency. The following references disclose means of generating and using steam from an internal combustion engine exhaust gas.
U.S. Pat. No. 4,300,353 to Ridgway teaches a hybrid engine of the type described above in which the steam is generated in a boiler.
U.S. Pat. No. 4,433,548 to Hallstrom teaches a hybrid internal combustion/steam engine and specifies that steam is generated in a generating chamber by the transfer of heat to water from the hot surfaces of the chamber.
U.S. Pat. No. 4,406,127 to Dunn teaches a hybrid internal combustion/steam engine in which water is sprayed onto the hot surface of an exhaust manifold inside a steam-generating chamber. The resulting steam is used in a closed-circuit reciprocating steam engine.
U.S. Pat. No. 5,000,003 to Wicks discloses a hybrid internal combustion/steam engine in which steam is generated in a boiler and used in a closed-circuit steam engine.
U.S. Pat. No. 5,010,852 to Milisavlevic teaches a multi-fuel, multi-hybrid engine in which part of the power output is provided by steam generated in a boiler.
U.S. Pat. No. 5,191,766 to Vines discloses a hybrid internal combustion/steam engine in which steam is generated in a steam generation chamber which is separated by valving from both the internal combustion cylinder and the means of using the steam. Specifically, the steam is generated in a generation chamber, stored in a compression tank and released to drive a steam turbine operating in closed-circuit with a condenser. The steam generation system is interposed between the internal combustion engine cylinder and the means of using the steam. The transfer of water and steam between the components of the system is handled by valving.
U.S. Pat. No. 6,202,782 to Hatanaka discloses a hybrid engine in which heat is stored and periodically released in a closed-circuit gas turbine system.
U.S. Pat. No. 7,047,722 to Filippone teaches a hybrid internal combustion/steam engine in which the steam is generated and used in a closed-circuit turbine.
In all Patents except U.S. Pat. No. 5,191,766, the steam and exhaust gases are separated from each other by heat-transfer walls.
A significant problem with the hybrid internal combustion/steam engines disclosed and under development to date lies in their complexity, bulk, weight and potentially high construction and maintenance costs per unit of power output.
Considering
The rotational speed and speed-torque characteristics of the turbine 10 may typically differ from that of the internal combustion engine 4. Consequently, the turbine may drive an electric generator 16 which drives an electric motor 18, the power output of which may then be applied to the hybrid engine drive shaft.
Whether the steam circuit is closed (with a condenser 12 returning exhaust steam to the boiler 6 as water) or open (exhausting steam to atmosphere), the boiler 6 requires an injector or feed pump (not shown) to force water into the boiler against the pressure of the steam being generated there. The injector or feed pump consumes some of the power produced by the hybrid engine.
While these arrangements may tend to maximize thermal efficiency, they may also tend to make a hybrid internal combustion/steam engine substantially bulkier, heavier and more complicated than a conventional internal combustion engine of equivalent power output and, hence, more costly to construct and maintain, thereby detracting from its total economy.
Applicant has developed a new hybrid engine design wherein the exhaust gas heat of an internal combustion engine is used to generate gas and the generated gas is used to power an external combustion engine adding its power output to that of the internal combustion engine. The thermal efficiency of the hybrid engine may be higher than the thermal efficiency of an internal combustion engine without use of the exhaust gas heat.
Accordingly, there is disclosed a hybrid engine comprising:
In another aspect, there is provided a hybrid engine comprising:
Embodiments of the present hybrid engine may use as the external combustion engine portion, a reciprocating, steam engine arrangement.
Embodiments of the present hybrid engine may be simpler and cheaper to construct and maintain than engines of equivalent power output disclosed in the referenced prior patents.
Embodiments of the presenting hybrid may be of lesser weight and bulk per unit of power output than the engines disclosed in the referenced prior patents.
Embodiments of the present hybrid engine include a steam engine that operates within the temperature range between the initial and final exhaust gas temperatures of the internal combustion engine.
Embodiments of the present hybrid engine include a reciprocating, open-circuit steam engine, as distinct from a turbine, closed-circuit steam engine. A reciprocating, open-circuit steam engine may typically be simpler and cheaper to construct than a closed-circuit, turbine steam engine of similar power output.
Embodiments of the present hybrid engine may include a reciprocating steam engine which adds its power output to that of the internal combustion engine by direct mechanical means, such as gearing, which tends to make the present hybrid simpler and cheaper to construct and maintain than the addition of power to the internal combustion engine by indirect means, such as electrical means.
Embodiments of the present hybrid engine generate steam in the cylinder(s) of the reciprocating steam engine. This may make a reciprocating steam engine effective at higher cycling rates than might normally be practical in a conventional reciprocating steam engine, where the steam is generated outside the cylinder, allowed to enter the cylinder and then allowed to expand within the cylinder.
Embodiments of the present hybrid engine make use of steam generated without a boiler. Such an engine without a boiler may be simpler and cheaper to construct than a hybrid engine of similar power output incorporating a boiler.
Embodiments of the present hybrid engine provide an engine in which the power of the steam engine may begin to develop substantially simultaneously with the starting of the internal combustion engine.
Embodiments of the present hybrid engine may provide the above-listed benefits without inducing substantial back pressure in the exhaust of the internal combustion engine.
Aspects of the present invention are illustrated, merely by way of example, in the accompanying drawings in which:
In embodiments discussed below, the hybrid engine embodiments employ a steam engine as the secondary external combustion engine portion, however, it will be understood that other external combustion engine arrangements may be used.
The present hybrid engine was developed according to the following simplifying steps which render the engine generally simpler and, hence, cheaper to construct and maintain than the internal combustion/steam hybrid engines disclosed or under development hitherto:
A first step in reducing the complexity of an internal combustion/steam hybrid engine may be to use a reciprocating steam engine instead of a turbine steam engine. A reciprocating steam engine may typically be simpler and cheaper to construct and maintain than a turbine steam engine of similar power output.
This brings the problem that reciprocating steam engines, e.g. locomotive engines, tended to be adversely affected by the viscosity of the steam at cycling rates higher than 350-400 revolutions per minute. At and above such cycling rates, the opening time of the valves admitting steam to the cylinders was so short that the admission of steam was limited and the possible power output of the engine at those cycling rates was limited as a consequence.
In internal combustion engines, pressure is generated and applied substantially simultaneously inside the cylinders, permitting higher cycling rates and, hence, higher power density, where power density is measured as the power output per unit of engine bulk or weight.
Conventional internal combustion engines typically function at cycling rates of the order of 2,000-4,000 revolutions per minute. This would bring into question whether any useful power output could be obtained from a conventional reciprocating steam engine at those cycling rates.
In the present hybrid engine, a reciprocating steam engine may be used as the secondary engine of the hybrid engine. Steam may be generated inside the cylinder(s) of the steam engine by passing internal combustion exhaust gases through the cylinder and injecting a fine spray of water. This water may be preheated almost to boiling point before being injected into the cylinders.
This may:
Generation of steam inside the cylinder may provide a further significant benefit as a third step, namely elimination of the boiler.
With the exception of U.S. Pat. No. 5,191,766, the hybrid engines disclosed in the mentioned references comprise the generation of steam in pressurized systems separated by heat transfer walls from the internal combustion engine exhaust gas, typically and generically known as boilers or heat exchangers.
Several problems tend to arise from such systems:
Elimination of the boiler in a hybrid internal combustion/steam engine would, therefore, be a significant benefit.
The thermal efficiency and power output of a steam engine is in proportion to its steam pressure. The highest attainable steam pressure is therefore desirable, but in a conventional steam-generating system is limited by the factors mentioned in items (a), (e) and (m) above. The problems listed in items (b) to (d) also typically increase with increasing steam pressure and temperature.
Concerning item (m) above, the steam pressure is typically contained in the steam cylinder and in a boiler, its fittings and steam pipes. The cylinder is a better shape than the boiler system for resisting internal pressure. In the present hybrid engine, water is injected as a fine spray into the secondary (steam) cylinder(s) at just below its boiling point, and exposed directly to internal combustion exhaust gases at temperatures of the order of 1,000° F. without an intervening heat transfer wall. The resulting steam pressure would be confined within the steam cylinder(s). The cylinder(s) may be built to withstand these pressures.
In an internal combustion engine, the exhaust gases may typically begin to lose heat as soon as they leave the cylinders. This is partly due to adiabatic cooling and partly due to conduction and convection through the walls of the exhaust system. Thus, the exhaust gases are never as hot as when leaving the cylinders. It would therefore be desirable to locate the steam generating means as close as possible to the exhaust gas outlet from the internal combustion cylinders. The present hybrid engine provides this additional benefit of proximity between steam generation and internal combustion exhaust.
If a pressurized boiler, with a water/steam space separated by heat transfer walls from the exhaust gases, can be dispensed with, as in U.S. Pat. No. 5,191,766, the problem arises how the steam can be induced to exert pressure on a power-producing means without also exerting a back pressure into the internal combustion cylinder, considering that:
U.S. Pat. No. 5,191,766 discloses the generation of steam directly by a mixing of the internal combustion exhaust gas with a spray of water, followed by expansion of the steam in a turbine. The '766 Patent does not disclose a means by which the steam can be generated and expanded inside a reciprocating engine cycling at high rates and driving directly on the hybrid engine drive shaft.
U.S. Pat. No. 5,191,766 depends for its functioning on a one-way flow of fluids and gases from the internal combustion exhaust outlet through the steam-generating system. The '766 Patent specifies at least one “one-way valve.” Unless a pump is interposed, which would consume energy and add to the cost and complexity of the system, this flow can take place only if the pressure in the internal combustion exhaust outlet is higher than the pressure in the system for generating and applying steam pressure. In other words, the back pressure in the internal combustion exhaust outlet must exceed the pressure in the steam system. This may be undesirable as a portion of the mechanical work done by the internal combustion engine must necessarily be used to overcome this back pressure.
The present hybrid engine discloses a means by which the back pressure in the internal combustion exhaust outlet may be no greater than the friction head between the internal combustion exhaust and the final exhaust.
The reciprocating steam engine portion of the present hybrid engine would typically require a piston stroke in the steam cylinder to receive exhaust gases from the internal combustion cylinder, whereby the piston in the steam cylinder would move in the direction from top dead center (TDC) towards bottom dead center (BDC).
(Top dead center is a term typically used to describe the piston position where the contained volume inside the cylinder is at a minimum. Bottom dead center is a term typically used to describe the piston position where the contained volume inside the cylinder is at a maximum. Both of these terms are used regardless of the physical attitude or orientation of the cylinder.)
This intake stroke needs to be followed by a piston stroke powered by the steam generated by the internal combustion exhaust gases within the steam cylinder, also moving in the direction from TDC towards BDC.
There would then need to follow an exhaust stroke, whereby the steam piston would tend to move in the direction from BDC towards TDC. This piston stroke would exhaust a mixture of steam and exhaust gases from the steam cylinder in preparation to receive another charge of internal combustion exhaust gases.
The desired cycle would thus consist of two piston strokes in the direction from TDC towards BDC, but only one in the direction from BDC towards TDC. A stroke in the direction from BDC towards TDC, interposed between the two strokes from TDC towards BDC would tend either to exhaust the fluids and gases if they were not confined within the steam cylinder, or to compress them if they were confined within the steam cylinder. Exhausting them from the cylinder would minimize the work that they could do. Compressing them would consume work for no desirable purpose and would therefore detract from the power and efficiency of the steam engine. The present hybrid engine provides a solution to this problem.
Referring to
This hybrid engine 20 may consist of a primary internal combustion (IC) engine portion 22 and a secondary external combustion engine portion 24 functioning in accordance with a duplex cycle as shown in
Considering
Turning to
Each secondary steam cylinder 28 may be fitted with a valved inlet 56 for the exhaust gases from the primary internal combustion cylinder, corresponding to the valved exhaust gas outlet 54 from the primary cylinder, a water nozzle 58 and a valved exhaust outlet 60. Each secondary steam cylinder 28 may contain an enlarged headspace 62, such that the volume inside the secondary cylinder 28, when the secondary piston is at top dead center (TDC) may be approximately equal to the volume swept by the primary internal combustion piston 26′ in the primary cylinder 26.
The secondary piston 28′ may be geared to the primary piston 26′ so that the secondary piston cycles at some fraction of the rate of the primary piston. This may be achieved by the gearing arrangement shown in
The flow of gases and fluids through the primary cylinder 26 and secondary cylinder 28 may be controlled by valves 90, 92 and 94 which will be described in more detail below. The valves are typically three in number per pair of cylinders and are adapted to open and close in conformity with the functioning of the engine as described below and as shown in
In the illustrated first embodiment, the secondary cylinder 28 may exhaust to atmosphere. In an alternative embodiment, the secondary cylinder 28 may exhaust to a second-stage engine or some other heat recovery means. In a further embodiment, each primary cylinder 26 may exhaust to more than one secondary cylinder 28 in sequence. Embodiments incorporating these additional configurations will be discussed below in association with
Returning to the illustrated first embodiment of
The water jacket 70 may be provided with two outlets. A pump or other means (not shown) may draw water from a first outlet 72 of the water jacket and circulate the water through a radiator (not shown) so as to control the temperature of the water in the water jacket.
A pump 76 or other means may draw water from the water jacket through a second outlet 74 and force the water through the water nozzle 58 into the secondary cylinder 28 as a spray 80 of atomized water particles. The flow rate of water and the fineness of the spray may be adjustable.
Atmospheric or other external pressure may tend to replenish the water in the water jacket from an external supply via inlet 78. Inlet 78 also serves as the return inlet for water circulated through the radiator.
The atomized water spray 80 injected into the secondary cylinder 28 may tend to expose a very large surface area of water per unit volume of water to the hot exhaust gases, being the total surface area of a very large number of fine droplets. The volume of each droplet may typically be very small, so that a rapid conversion of water to steam may take place. The water, already heated to just below its boiling point during its passage through the water jacket 70, may therefore be sprayed into the steam cylinder and converted into steam by direct contact with the exhaust gases from the internal combustion engine, which may be at temperatures of the order of 1,000° F.
The rate of water flow from water nozzle 58 may be adjustable so that the maximum amount of steam may be generated.
The primary piston 26′ and secondary piston 28′ typically drive crankshafts 30 and 32, respectively, as described above with reference to
Also as described above, the crankshafts 30 and 32 may be connected so that the secondary piston 28′ cycles at some fraction of the rate of the primary piston 26′ and at some phase angle to the primary piston. In this first embodiment, the secondary piston may typically cycle at half the rate of the primary piston at a phase angle of 135 degrees between TDC in the primary piston and TDC in the secondary piston. It will be appreciated by a skilled person that phase angles other than 45 and 135 degrees may be possible or even preferable.
Also as described above, the primary and secondary crankshafts may be connected in a manner such that the secondary piston 28′ may drive the primary crankshaft 30 during one part of the cycle and may be driven by the primary crankshaft during some other part of the cycle.
In alternative embodiments to those already described, there may be more than one secondary cylinder 28 for each primary cylinder 26. The secondary pistons 28′ may cycle at some rate other than half the rate of the primary pistons. The secondary pistons 28′ may cycle at some phase angle(s), other than 45 degrees and 135 degrees to the primary pistons 26′. The motion of either or both pistons may be other than sinusoidal.
Referring to
Phase A begins with the primary piston 26′ at top dead centre (TDC (pri)) and the secondary piston 28′ approximately one quarter the way from bottom dead centre (BDC(sec) to TDC(sec). The primary cylinder inlet valve 90 and exhaust valve 92 are both closed. The secondary exhaust valve 94 is open.
During Phase A, the primary piston 26′ makes its power stroke from TDC(pri) to BDC(pri) as indicated by arrow 96 in
At the end of Phase A, the primary piston 26′ reaches BDC(pri), and the secondary piston 28′ may be approximately three quarters of the way from BDC(sec) toward TDC(sec). The primary exhaust valve 92 opens and the secondary exhaust valve 94 remains open. The primary inlet valve 90 remains closed.
Phase B begins with the primary piston 26′ at BDC(pri). The secondary piston 28′ may typically be approximately three quarters of the way from BDC(sec) to TDC(sec) moving in the direction of arrow 100 in
During Phase B, the primary piston 26′ begins its exhaust stroke in the direction of arrow 102 in
At the end of Phase B, the primary piston 26′ may typically be approximately halfway from BDC(pri) toward TDC(pri). The secondary piston 28′ reaches TDC(sec). The primary inlet valve 90 remains closed; the primary exhaust valve 92 is open; the secondary exhaust valve 94 closes.
Phase C begins with the primary piston 26′ in the middle of its exhaust stroke from BDC(pri) to TDC(pri) and the secondary piston 28′ at TDC(sec). The primary inlet valve 90 remains closed; the primary exhaust valve 92 remains open; the secondary exhaust valve 94 is closed.
During Phase C, the primary piston completes its exhaust stroke, reaching TDC(pri) as indicated by arrow 104 in
At the end of Phase C, the primary piston 26′ may reach TDC(pri); the secondary piston 28′ may be approximately one quarter the way from TDC(sec) toward BDC(sec). The primary inlet valve 90 opens; the primary exhaust valve 92 closes; the secondary exhaust valve 94 remains closed.
Phase D begins with the primary piston 26′ at TDC(pri), having completed its exhaust stroke. The secondary piston 28′ may typically be approximately one quarter the way from TDC(sec) toward BDC(sec). The primary inlet valve 90 opens; the primary and secondary exhaust valves 92 and 94, respectively, are both closed.
During Phase D, the primary piston may typically make its complete induction stroke from TDC(pri) to BDC(pri) in the direction indicated by arrow 108 in
At the end of Phase D, the primary piston 26′ may typically reach BDC(pri). The secondary piston 28′ may typically continue to move toward BDC(sec) as indicated by arrow 110. The primary inlet valve 90 closes, both exhaust valves 92 and 94 remain closed.
Phase E begins with the primary piston 26′ at BDC(pri). The secondary piston 28′ is moving toward BDC(sec) as indicated by arrow 112 in
During Phase E, the primary piston 26′ begins its compression stroke in the direction indicated by arrow 114 in
At the end of Phase E, the primary piston 26′ may typically be moving toward TDC(prim); the secondary piston 28′ may reach BDC(sec) at the completion of its power stroke. The inlet valve 90 and primary exhaust valve 92 remain closed. The secondary exhaust valve 94 opens.
Phase F begins with the secondary piston 28′ at BDC(pri). The primary piston 26′ may typically be moving toward TDC(pri) as shown by arrow 116. The primary inlet valve 90 and the primary exhaust valve 92 both remain closed. The secondary exhaust valve 94 opens.
During Phase F, the primary piston may typically reach TDC(pri), completing its compression stroke. The secondary piston may typically begin its exhaust stroke, expelling the mixture of steam and exhaust gas through the secondary exhaust outlet 94.
At the end of Phase F, the primary piston 26′ may typically reach TDC(pri) at the end of its compression stroke. The secondary piston 28′ may typically be approximately one quarter of the way from BDC(sec) toward TDC(sec). The primary inlet valve 90 and primary exhaust valve 92 are both closed; the secondary exhaust valve 94 is open. The cycle then begins again with Phase A.
In another embodiment, the water spray 80 may be injected into the secondary cylinder 28 continuously. Steam may, therefore, be generated substantially continuously and may apply pressure to the secondary piston 28′ whenever the primary and secondary exhaust valves 92, 94 are both closed, preventing the escape of the steam. This may typically be arranged to occur when the secondary piston is moving from TDC towards BDC; a pressure in excess of atmospheric pressure may thus tend to power the secondary piston, so adding power to the crankshaft. This modification would provide a simplified manner of injecting water into the second cylinder.
In another embodiment, the secondary cylinder 28 may be formed without additional headspace 62 as shown in
In illustrated embodiments of
Additional hybrid engine configurations that incorporate multiplex and multistage arrangements of cylinders are shown schematically in
The present hybrid engine design does not preclude multiple stages of steam generation and expansion. For example,
In all of the various embodiments of the present hybrid engine described above, the movement of the pistons will be sinusoidal based on a plot of piston velocity vs. time. It will be appreciated that the present hybrid engine design does not preclude an arrangement such that the movement of the primary and/or secondary pistons may not be sinusoidal.
In a further embodiment of the present hybrid engine, the primary internal combustion engine portion may function on a two-stroke cycle rather than a four stroke cycle. In this case, the heated exhaust gases of the primary cylinder would be generated during the power/exhaust stroke of the two stroke primary engine portion. As the top of the primary piston passes an exhaust port, the pressurized exhaust gases begin to exit to the secondary cylinder. As the primary piston continues moving toward bottom dead centre, the piston compresses an air/fuel/oil mixture in the crankcase so that once the top of the piston passes a transfer port, the compressed charge enters the primary cylinder from the crankcase and any remaining exhaust is forced out. The intake/compression stroke begins as the primary piston starts to move to top dead centre. This movement compresses the charge in the cylinder and draws a vacuum in the crankcase, pulling in more air, fuel, and oil.
In a still further embodiment, the primary internal combustion engine portion may function as a diesel engine.
Referring to
In another embodiment, the secondary pistons and cylinders of the secondary external combustion engine portion may be arranged on the uniflow system. In this design, the exhaust port of the secondary cylinder may be located in the wall of the secondary cylinder in such a position that the movement of the secondary piston to at or near BDC(sec) will uncover the exhaust port, thereby allowing a flow of gases out of the secondary cylinder without the action of the separate exhaust valve required by the first-described embodiment. The utility of this embodiment lies in the absence of a secondary exhaust valve and its timing mechanism.
Although the present invention has been described in some detail by way of example for purposes of clarity and understanding, it will be apparent that certain changes and modifications may be practised within the scope of the appended claims.
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/CA08/01922 | 10/31/2008 | WO | 00 | 7/27/2010 |
| Number | Date | Country | |
|---|---|---|---|
| 61001038 | Oct 2007 | US |
