Patent Application
20160230605
Not Applicable
Not Applicable
Not Applicable
Low grade fuels (low density, low heating value solid, liquid and gaseous substances) are not competitive with higher grade commercial fuels in small scale (e.g., less than 2000 kW) mobile and stationary power plants. This is mainly due to the lack of small scale, efficient, low cost steam prime movers that can economically convert low grade fuels into usable, industrial power.
The traditional reciprocating steam engine, in its various forms, has become economically and technologically obsolete due to the availability of refined, petroleum based fuels that were better utilized in more efficient heat engine cycles (Otto, Diesel and Brayton cycles) and the development of low cost electrical power delivered by the interconnected utility power grid. The traditional steam engine is limited by its ability to convert raw, unrefined fuel sources into clean, high quality steam energy that is converted to mechanical work. The final evolution of reciprocating steam engine technology circa 1950 is represented by the uniflow steam engine. The first American uniflow engine was built in 1913 by the Skinner Engine Company of Erie, Pa.; the last one was built in 1982. The Skinner Engine Company closed its doors and was liquidated in 2003.
The Skinner Universal Uniflow steam engine, circa 1950, represents the current state of the art for commercially manufactured, industrial steam engines applied to stationary service. The Skinner Uniflow steam engine was a major improvement over previous engine types because it improved steam flow dynamics and thermal efficiency. But it could only work at relatively low speeds (e.g., generally not exceeding 400 rpm). Thus, it required high torque outputs. The result is that the Skinner Uniflow engine had five major weaknesses: (a) massive and costly components that could not withstand high reaction forces generated by large piston diameters due to low rotational speeds (generally not above 400 rpm); (b) double acting pistons required complex piston rod/crosshead/connecting rod assemblies that limited rotational speeds due to high inertia forces that could not be adequately balanced at high speed; (c) long cutoffs of up to 40% that adversely impacted thermodynamic performance; (d) need for large concrete foundations to support the heavy engine weights and separate condenser, and, therefore, lack of portability; and (e) higher cost compared to less efficient steam turbines due to higher manufacturing and labor costs.
A compact, thermodynamically and power efficient steam engine that runs at higher speeds, and therefore, requires lower torque outputs, has smaller components and does not require a massive support foundation is unknown in the prior art.
The present invention is directed to a Practical Steam Engine that can run at higher speeds (at least 400 rpms) and, thus, requires lower torque outputs. This lower torque output, in turn, allows the power delivery through smaller components that do not need to be supported by a massive concrete foundation as does the prior art uniflow engine. The fact that the Practical Steam Engine can be made compactly and relatively portable makes it ideal for off-grid power generation applications. The Practical Steam Engine may be fueled by biomass, such as slash and thinnings as part of forest management practices, or for providing steam-generated power at a merchantable timber source to add value to wood product processes.
The Practical Steam Engine includes at least one cylinder head assembly, an admission and exhaust valve assembly, a cylinder/piston assembly, a crank shaft assembly or other similar apparatus that converts between reciprocating motion and rotational motion, a valve gear assembly. The admission or the exhaust valve assembly, or both the admission and exhaust valve assembly includes a variable duration, rotary valve (the “rotary valve”). The rotary valve eliminates reciprocating motion reducing the number of moving components therefore reducing the failure rate of mechanical components. Another advantage of the rotary valve is that it, in its typical motion, does not move in a direction significantly affected by the forces of net pressure forces of the working fluid, a common problem experienced by poppet-valves and slide valves conventionally used in these types of engines.
When the Practical Steam Engine is placed into a conventional Rankine cycle with an evaporator (boiler), condenser, and pumps, the overall energy generation plant may produce mechanical work using raw, unrefined fuel sources such as biomass (e.g., residual forest waste) and other unconventional fuel sources, as well as conventional fuel sources. The Practical Steam Engine steam-powered generator is more compact in size than prior art. For example, The Practical Steam Engine may, for example, be transported to remote areas, particularly where remotely-accessed biomass may be located. This cuts down on the high cost and pollution from using conventional fuel sources (e.g., Diesel oil) to transport the biomass to the Practical Steam Generator. This compact-size steam generator using the Practical Steam Engine can be utilized within deep forests as part of forestry management or at a merchantable timber source to allow value-added processing at or closer to the power source (such as at sawmills, or wood palletizing and pulp chipping). Further, the Practical Steam Engine may be used to produce higher value wood processed products closer to the power source, thereby reducing transportation logistics, costs and additional carbon emissions from such transportation.
The single acting, simple expansion design of the Practical Steam Engine lends itself to conversion of a counter flow, semi-uniflow or uniflow engine to a counter flow, semi-uniflow, or uniflow engine for steam operation. The conversion process replaces a cylinder head, including the poppet valves, of a conventional engine with a cylinder head having an integral valve assembly. The resulting converted engine to steam engine operates at high volumetric efficiency.
Other features and advantages of the present invention will become apparent in the following detailed descriptions of the preferred embodiment with reference to the accompanying drawings, of which:
The present invention is described more fully hereinafter with reference to the accompanying drawings, in which preferred embodiments of the invention are shown. This invention may, however, may be embodied in many different forms and should not be construed as limited to the embodiments set for herein; rather, these embodiments are provided so that this disclosure will be thorough and complete and will fully convey the scope of the invention to those skilled in the art. The current invention is a high speed, two-stroke engine that is counter flow, semi-uniflow, or uniflow and is comprised of at least one variable rotary valve mechanism. Working fluid, referred to herein, may be organic and/or inorganic fluid, naturally occurring and/or man-made. Working fluid may include: Chlorofluorocarbon (CFC) (e.g. R-11, R-12); Hydro-fluorocarbons (HFC) (e.g. R-134a, R-245fa); Hydro-chlorofluorocarbon (HCFC) (e.g. R-22, R-123); Hydrocarbons (HC) (e.g. Butane, methane, pentane, propane, etc.); Perfluocarbon (PFC); Basic organic compounds (Carbon dioxide, etc.); Inorganic compounds (e.g. Ammonia); Elements (Hydrogen, etc.), or a combination thereof, amongst others. A preferred working liquid is water.
Most commercial engines have four, six, or eight cylinders where each cylinder operationally houses a piston. The current invention may have a conventional number of cylinders however; it must have at least one cylinder. Referring to
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The intake rotary valve assembly 22 accommodates the adjustment valve assembly 23. The adjustment valve assembly 22 front end 23b is supported by a bearing 27 mounted to the intake rotary valve assembly 22 front end 22b. Similarly, the rear end 23c of the adjustment valve assembly 23 rear end is supported by a bearing 27 located to the intake valve assembly rear end 22c. Additionally, a stationary bushing 28 is operably mounted to the cylinder head assembly 11. Preferably, the stationary bushing 28 is aligned concentrically with the intake rotary valve assembly cylindrical bore 20, and supports the rear end 23a of the adjustment valve assembly 23. Known seals prevent working fluid leakage and protects the valve bearing 25 from the working fluid; preferably, the seal is a rotary lip seals 29.
Working fluid is supplied through the working fluid inlet port 35 and fills the cylinder head annular volume around the intake valve assembly 22. The working fluid travels through working fluid ports 37, radially located around the circumference of the intake valve tube 22a. As the intake valve assembly 22 rotates, these ports align with adjustment tube working fluid ports 38, radially located around the circumference of the adjustment valve tube 23a, thus supplying working fluid to the interior of the adjustment valve tube 23a. When the intake valve cylinder ports 33 and adjustment valve cylinder ports 32 align as described in
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Once exhaust working fluid leaves the cylinder 13 and is delivered to the interior of the exhaust valve tube 24a through the exhaust tube port 34, the exhaust rotary valve assembly 24 rotates until the exhaust tube port 34 aligns with the primary exhaust port 36. The intake rotary valve assembly 22 rotates at a speed directly related to the engine speed. The intake rotary valve assembly 22 may rotate at the same speed of the engine, one-half the engine speed, one-third of the engine speed, etc. Preferably, the intake rotary valve assembly 22 rotates at one-half engine speed. When the working fluid inlet port 38 aligns with the cylinder head intake port 30 and the adjustment valve cylinder port 32, working fluid is allowed into the interior of the adjustment valve tube 23a to be supplied to the cylinder 13 via the cylinder head intake port 30.
The adjustment valve assembly 23 may be adjusted angularly by rotating the adjustment valve assembly 23 rear end 23c by adjusting the duration of communication between the interior of the adjustment valve tube 23a and the cylinder head intake port 30, resulting in control of admission cutoff. The control of this admission cutoff may be used to control engine speed and/or power output. The exhaust valve tube 24a also rotates at a speed directly related to engine speed. The exhaust rotary valve assembly 24 may rotate at the same speed of the engine, one-half the engine speed, one-third of the engine speed, etc. Preferably the exhaust rotary valve assembly 24 rotates one-half the speed of the engine. As the exhaust valve tube 24a rotates, the exhaust tube port 34 aligns with the cylinder head exhaust port 31. Working fluid is exhausted from the cylinder 13 into the interior of the exhaust valve tube 24a. When the exhaust tube port 34 aligns with the primary exhaust port 36, working fluid is exhausted from the interior of the exhaust valve, thus allowing exhaust working fluid to exit the cylinder head assembly 11 and subsequently the engine 10. Preferably, both the intake valve tube 22a and the exhaust valve tube 24a may utilize diametrically opposed cylinder ports, thus producing an inherently radially balanced valve. Preferably the intake valve 22 and the exhaust valve 24 operate at precisely one-half engine speed—increasing bearing life.
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