Internal-combustion engines – Adjustable combustion chamber – Piston in head adjusted
Reexamination Certificate
2001-11-29
2004-03-23
Kamen, Noah P. (Department: 3747)
Internal-combustion engines
Adjustable combustion chamber
Piston in head adjusted
C123S0480AA
Reexamination Certificate
active
06708654
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to internal combustion engines designed to improve efficiency, improve power to weight ratios, and reduce emitted pollutants in a configuration which is readily manufacturable. The invention is most applicable to engines used in automotive applications.
BACKGROUND OF THE INVENTION
A major objective of the invention is to provide a prime mover engine, i.e. a device to derive mechanical energy from the heat energy of a burning fuel, with higher efficiency in a lighter weight and smaller configuration than has heretofore been the case; particularly at power demands less than the engine's maximum. The main use for the invention is for automobile power: For this application efficiency at low engine torque at moderate speeds is of prime interest since most of the time an automobile engine operates at approximately 10% of its maximum power output at moderate speeds-typically 1,500 to 3,000 rpm.
The engineering terminology used in this specification follows standard mechanical engineering practice. Three works have been used as engineering reference. These are:
Avallone and Baumeister, Ed., Marks'
Standard Handbook for Mechanical Engineers,
Tenth Edition, McGraw-Hill, 1996: referred to as ‘Marks’.
Ricardo, Harry R.,
The High Speed Internal Combustion Engine,
Fourth Edition, Blackie & Son, Ltd., 1967: referred to as ‘Ricardo’.
Stephenson, R. Rhoada.,
Should We Have a New Engine?,
Jet Propulsion Laboratory, California Institute of Technology, 1975: referred to as ‘Stephenson’.
Current automotive practice is usually to employ a spark-ignition engine with an average thermal efficiency around 20%; i.e. about 20% of the thermal energy of the fuel used is transferred to mechanical energy. Alternatively, a compression-ignition engine, more commonly called a diesel engine, is used having a somewhat higher efficiency at low output. The added efficiency of the diesel engine is, in passenger car application, offset by the added weight of current diesel engines. A typical passenger car using a diesel engine is no more efficient than a car of equal performance using a spark engine. Comparisons of apparent mileage differences between spark engines and diesel engines is obscured by the difference in energy content of diesel fuel and gasoline. Diesel fuel has about 18% more energy for a given volume, liter or gallon, than does gasoline: Thus an accurate comparison of a diesel car that gave 40 mpg with a spark-engine driven car giving 32 mpg would show that the two vehicles use almost exactly the same amount of energy. Even more exact comparisons that consider performance of the two autos shows that the diesel-driven car is most often less efficient than an equivalent spark-engined vehicle. Support for this argument comes from the choice of Toyota and Honda in their choice of spark engines for the Prius and Insight vehicles respectively. These two cars are designed to provide the ultimate in fuel mileage using contemporary techniques.
The discussion above begins to illustrate the problem of increasing the efficiency of automobiles. It is not enough to increase maximum efficiency of the prime mover; the efficiency at low power outputs and the weight of the engine are of equal or greater importance. In order to accomplish this increase of system efficiency it is necessary to reduce engine friction; increase engine power-to-weight, and focus on increasing the efficiency of the detailed burning process in the engine. In today's environment it is also necessary to ensure that the engine does not pollute the environment. If the engine is not inherently clean any accessories added to remove exhaust pollutants to the degree needed today can easily reduce efficiency directly and the weight added for these accessories will detract from the vehicle's fuel mileage.
Current proposals mostly fail to globally address the complexity of this problem. Any solution that addresses internal combustion engine efficiency needs to consider the basic combustion process itself. To obtain high efficiency at very low power outputs a solution must address the problem of lean burning. Hydrocarbon fuels do not burn rapidly enough for use in an automotive sized engine at fuel/air ratios under around 50-60% of stoichiometric ratio. To obtain ultra-efficient burning at 10% of maximum power output it is necessary to efficiently combine the fuel with air at fuel air ratios around 15-20% of stoichiometric within the time it takes an engine to rotate 30-35° at around 2,000 rpm or about 3 milliseconds. No matter what is done to a bulk air-fuel mixture this has not proved feasible in workable systems.
Diesel engines sidestep this problem by finely dividing the fuel and spraying it into a hot air environment. The burning that results occurs around each droplet at a fuel-air ratio almost exactly stoichiometric: Thus a mixture that is nominally a bulk mixture of fuel and air at a low fuel-air ratio is really a mixture of micro-domains of fuel and air at near stoichiometric ratio. The penalties inherent in this approach include the high friction penalties attendant with the use of compression ratios around 20:1 needed for automotive-sized engines and the aforementioned added weight. This illustrates that the solution must firmly address the problem of mechanical friction.
Friction and its effect on the part-load efficiency is largely ignored in contemporary proposed automotive prime mover solutions. The effect of friction is a very complicated factor. Typical modern production automotive engines battle friction by employing sophisticated valving and induction systems to ensure that maximum bearing loads are encountered only at moderate and higher speeds, where journal bearings can endure higher pressure loadings. This allows these same journal bearings to be designed smaller and thus the bearings contribute less friction to degrade the engine's performance.
The effect of friction is especially complicated when considered in conjunction with compression ratio. A higher compression ratio in an internal combustion engine inevitably results in concomitantly increased thermal efficiency. This is unfortunately accompanied by an increase in friction because the added compression ratio is inevitably attended by added friction from the larger bearings that are needed to support the higher loads that go along with the higher compression ratio. The friction loads are particularly influential to the engine when delivering low power at moderate speed which is the normal duty for an automotive engine.
It is highly desirable to realize an engine that is notably lighter and smaller for a given power output than conventional engines. It is well known that the fuel consumed by a road vehicle is approximately proportional to the vehicle's weight. Combining an increase in efficiency with lowered engine weight greatly increases the fuel efficiency of a vehicle system. This is especially true when the effects of what is called, in automotive technology, weight propagation are considered. This term describes the effects of changing the weight of any component of a vehicle system. Since the component must be carried by the vehicle system and the component's mass must be stopped by the vehicle's brakes the inevitable effect of changing the weight of any of the vehicle's components further entails a change in the weight of the vehicle by about 70% of the initial weight change. Thus a reduction of engine weight of 100 pounds will result in a total weight reduction of about 170 pounds due to the effects of weight propagation.
Internal Combustion Engine Pollutants
Another objective of the invention needed in today's environment is to create a prime mover than burns fuel in a manner that is inherently clean; whose combustion process inherently produces few contaminants associated with internal combustion engines. Such an engine will need fewer or smaller cleanup mechanisms such as catalytic converters used with it to meet increasingly stringent requirements for engine
Benton Jason
Jones Tullar & Cooper PC
Kamen Noah P.
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