Internal-combustion engines – Two-cycle – Pump and cylinder adjacent
Reexamination Certificate
1998-07-03
2001-11-13
Argenbright, Tony M. (Department: 3747)
Internal-combustion engines
Two-cycle
Pump and cylinder adjacent
C123S543000, C123S052500, C060S604000
Reexamination Certificate
active
06314925
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field Of The Invention
This invention relates to piston-type internal combustion engines having a combustor/expander cylinder, a separate compressor, and an exhaust heat recuperator means which preheats the compressed air charge. The invention relates further to an engine having a recuperator and a recuperator-protective valve to protect the recuperator from the combustion process.
2. Description Of The Related Art
Internal combustion engines today, with the exception of Diesels, operate on what is commonly known as an Otto cycle originally patented in France in 1862 by Alphonse Beau de Rochas. In 1876, the Rochas compression cycle was incorporated into a practical engine by Nicholas A. Otto. Otto engines were immediately more efficient than Lenoir non-compressing gas engines which had been in production since 1862. Then in 1892, Rudolf Diesel invented the compression ignition engine with higher efficiency than an Otto engine. At the time, their efficiencies were about 3 to 4% for the Lenoir, 12% for the Otto, and 24% for the Diesel, and compared with their expansion ratios of approximately 1.5: 1, 2.5:1, and 16:1.
The low efficiencies are related to the large amount of energy remaining in the engine exhaust at the moment of release by the exhaust valve. Exhaust temperatures for example of 1,450° Fahrenheit or more were reported for the Lenoir and Otto, and around 900° F. for the Diesel. Actual gas temperatures inside the cylinders when expansion was complete were surely much higher. This is because a great deal of exhaust gas heat transfers to the exhaust valve and then to the exhaust port walls. For example, gas reaches about 90% equilibrium with wall temperature after flowing only ten diameters along the length of a straight pipe. In early engines, exhaust valves and exhaust ports were labyrinthine in design and thus much of the heat from the exhaust was absorbed by these parts before the exhaust exitted the engine.
The better efficiency of the Diesel came about due to its very high expansion ratio, a result of the high compression ratio needed to create high temperature (generally greater than 550° F.) sufficient to auto-ignite the injected fuel. The high compression ratio and attendant gas and bearing pressures required greatly increased strength and with it, increased weight and cost. In fact, the Diesel is two to three times the weight and cost of a comparable Otto engine.
The first recuperative internal combustion engine of the prior art appears to be U.S. Pat. No. 4,155,087 issued on Sep. 15, 1874 to Joseph Hirsch. The described engine has two cylinders interconnected by a regenerator made of refractory elements. Because the heat exchanger is located in an external duct also made of refractory material, the heat exchanger continuously radiates away thermal energy. Hot exhaust gas from the “hot-air” cylinder, after passage through the heat exchanger, passes into the “cold-air” cylinder. When heated exhaust gas is in the cold-air cylinder, water is injected to cool and reduce the volume of the gas in the cold-air cylinder. Additional make-up air is then added under pressure and the gas volume is finally transferred to the hot-air cylinder via the heat exchanger. Utilization of the thermal energy in the exhaust is far from optimum as a consequence of lowering the temperature of the charge before transfer to the hot-air cylinder by way of the heat exchanger. Taking the radiation and convection heat losses from the heat exchanger into account, it is difficult to see how the device can effect an appreciable increase in the Carnot efficiency.
U.S. Pat. No. 328,970 issued Oct. 27, 1885 to James F. Place describes an engine having a compression-cylinder and a power-cylinder arranged in a vee, their cylinder heads connected by a regenerative means for the capture of exhaust heat. A cylindrical, internally finned, dual purpose recuperator valve of the type that is usually oil lubricated and sealed was located in the power cylinder head. This valve captured heat as it released exhaust gas and transferred the heat to the compressed charge passed back through the valve to the power-cylinder. Such a recuperator valve would probably have attained 1,000° F., creating problems with its lubrication and with any associated seals. The second stage external tubular recuperator connecting the cylinder heads was of considerable length and presented a large area for loss of heat to the atmosphere instead of retention in the next cycle. Place's patent indicates an amazing understanding of the problem when one considers the date of his work.
U.S. Pat. No. 642,176 issued to E. Thomson describes a two cylinder engine with its cylinders interconnected by a recuperator which is not separated from either cylinder by valving. Air is inducted into one cylinder and the other cylinder is filled with a fuel-air mixture. The fuel-air mixture is inducted into the cylinder containing air via the recuperator and is ignited during passage through the recuperator. Exhaust is released from each cylinder directly to the atmosphere and not through the recuperator whereby no exhaust heat is recovered.
U.S. Pat. No. 870,720 issued to A. J. Frith describes a two cylinder engine with the cylinders coupled by a recuperator as in the device of Thomsom without the isolation from either cylinder by valving. This engine suffers from the same deficiency as the engine of Thomson, in that exhaust is transferred to a cylinder and released directly to atmosphere without passing through the recuperator as is needed for maximum recovery of thermal energy. Additionally, the inventor teaches that the air should be saturated with water prior to compression and passage through the recuperator to the other cylinder. The presence of water vapor will lower the temperature of the recuperator and further reduce the Carnot efficiency.
In U.S. Pat. No. 1,111,841 issued to J. Koenig and U.S. Pat. No. 1,904,070 issued to J. D. Morgan, both inventors have the similar idea of cooling compressed air followed by heating the air in a recuperator. This method of operation does not make full use of the high value thermal energy of the exhaust since cooled compressed air sent through the recuperator must result in a lower temperature of the output gas and must therefore reduce the maximum attainable working temperature in the engine. Thus, the Carnot efficiency of the engines of each of these two inventions is less than that which is desired and is believed to be attainable in a properly engineered internal combustion engine.
In United Kingdom patent 528,391 issued 10/1940 to Michael Martinka there is described an engine having a regenerative heat-exchanger mounted movably within the combustion chamber and thus exposed to the combustion gases.
In United Kingdom patent 640,410 issued 7/1950 to Isaac Lubbock and R. Rigby and assigned to Shell Refining and Marketing Co. Ltd. there is described an engine having a regenerator fixed in the combustion chamber, or alternatively fixed to the head of the piston, and in either case exposed to the combustion gases.
In United Kingdom patent 761,122 issued 11/1956 to Richard Rigby and assigned to Shell Refining and Marketing Co. Ltd., an engine is described having a regenerator in the cylinder and attached to a movable sleeve. Another engine is described having a regenerator fixed in a cylinder between two reciprocating pistons. In each case the regenerator is exposed to the combustion process which is generally above the temperature tolerance of known regenerator elements.
In Swiss patent 307,098 issued 5/1955 to J. H. Keller and assigned to N. V. Machinefabriek en Reparatiebedrijf describes an engine having a multistage, intercooled compressor followed by an external regenerator feeding into a combustion/expansion cylinder.
United Kingdom patent 1,308,355 issued 2/1973 to Daimler-Benz Aktiengesellschaft on Feb. 28, 1973 describes an engine having a regenerator located and exposed to combustion between dual opposed pistons. It states that by use of the best heat-resistant mat
Argenbright Tony M.
Castro Arnold
Schaeffer Daniel M.
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