System for minimizing internal combustion engine pollution emission
United States Patent 3906913
A mixing device is provided for an internal combustion engine which simultaneously atomizes liquid fuel, mixes this fuel with an optimal quantity of hydrogen and combines this mixture with a prescribed quantity of air. A throttling mechanism controls the fuel delivery to the engine and also limits the fuel to air equivalence ratio to be predetermined upper bound to inhibit the production of air pollutants and to a lower bound which is above the lean flammability of the mixture.
US Patent References:
/1112188.html
Atwood - September 1914 - 1112188
Antidetonation system
Young et al. - September 1949 - 2482531
/1112188.html
Atwood - September 1914 - 1112188
Antidetonation system
Young et al. - September 1949 - 2482531
Application Number:
05/387342
Publication Date:
09/23/1975
Filing Date:
08/10/1973
View Patent Images:
Export Citation:
Assignee:
California Institute of Technology (Pasadena, CA)
Primary Class:
Other Classes:
123/DIG.012, 123/575, 123/198A
International Classes:
F02D19/08; F02M25/12; F02D19/00; F02M25/00; F02M13/08
Field of Search:
123/DIG.12,119E,121,127,120,198A
Primary Examiner:
Burns, Wendell E.
Attorney, Agent or Firm:
Lindenberg, Freilich, Wasserman, Rosen & Fernandez
Claims:
What is claimed is
1. A system for minimizing the air pollution output of an internal combustion engine comprising
2. A system as recited in claim 1 wherein said means for mixing includes a pneumatic atomizer for atomizing fuel and mixing fuel with hydrogen rich gas, and
3. A system as recited in claim 2 wherein said means for controlling said means for mixing includes a throttle controlled fuel control valve means for controlling the amount of fuel supplied to said pneumatic atomizer;
4. A system as recited in claim 3, wherein said means for sensing the mass air flow to said engine and producing a representative control effect includes
5. A system as recited in claim 1 wherein said means for controlling controls said means for mixing to produce, over the operating range of said engine, a gas, fuel and air mixture which is within the flammable range for the mixture and which does not exceed an upper bound equivalence ratio of approximately 0.6.
6. A system for minimizing the air pollution output of an internal combustion engine, comprising
7. A system as recited in claim 6 wherein said means for mixing and emitting hydrocarbon fuel and hydrogen gas into said induction tube comprises
8. A system as recited in claim 6 wherein said valve means in said fuel supply control means for controlling the amount of hydrocarbon fuel passing therethrough includes
9. A system as recited in claim 6 wherein said override means for limiting the maximum amount of fuel passed by said fuel supply control means includes
10. In an internal combustion engine a system for eliminating noxious emissions from said engine comprising
11. In an internal combustion engine as recited in claim 10 wherein said throttle controlled fuel supply means includes a variable area fuel control valve for supplying hydrocarbon fuel to said pneumatic atomizer,
12. In an internal combustion engine as recited in claim 11 wherein said variable area fuel control valve includes means for closing off the hydrocarbon fuel supplied to said pneumatic atomizer when said movable throttle rod means assumes an engine idle position.
13. In an internal combustion engine as recited in claim 10 wherein said override control means includes
14. In an internal combustion engine, an induction system for providing a hydrogen rich gas, hydrocarbon fuel and air mixture to said engine to minimize the air pollutants produced by said engine comprising
15. A method of minimizing the air pollution output of an internal combustion engine comprising the steps of
16. A method as recited in claim 15 wherein said step of mixing said air, hydrocarbon fuel and hydrogen rich gas includes
17. A method as recited in claim 16 wherein said step of supplying predetermined quantities of hydrocarbon fuel includes
18. A method as recited in claim 15 wherein said step of controlling said mixing provides only a mixture of a hydrogen rich gas and air when said engine is idling.
1. A system for minimizing the air pollution output of an internal combustion engine comprising
2. A system as recited in claim 1 wherein said means for mixing includes a pneumatic atomizer for atomizing fuel and mixing fuel with hydrogen rich gas, and
3. A system as recited in claim 2 wherein said means for controlling said means for mixing includes a throttle controlled fuel control valve means for controlling the amount of fuel supplied to said pneumatic atomizer;
4. A system as recited in claim 3, wherein said means for sensing the mass air flow to said engine and producing a representative control effect includes
5. A system as recited in claim 1 wherein said means for controlling controls said means for mixing to produce, over the operating range of said engine, a gas, fuel and air mixture which is within the flammable range for the mixture and which does not exceed an upper bound equivalence ratio of approximately 0.6.
6. A system for minimizing the air pollution output of an internal combustion engine, comprising
7. A system as recited in claim 6 wherein said means for mixing and emitting hydrocarbon fuel and hydrogen gas into said induction tube comprises
8. A system as recited in claim 6 wherein said valve means in said fuel supply control means for controlling the amount of hydrocarbon fuel passing therethrough includes
9. A system as recited in claim 6 wherein said override means for limiting the maximum amount of fuel passed by said fuel supply control means includes
10. In an internal combustion engine a system for eliminating noxious emissions from said engine comprising
11. In an internal combustion engine as recited in claim 10 wherein said throttle controlled fuel supply means includes a variable area fuel control valve for supplying hydrocarbon fuel to said pneumatic atomizer,
12. In an internal combustion engine as recited in claim 11 wherein said variable area fuel control valve includes means for closing off the hydrocarbon fuel supplied to said pneumatic atomizer when said movable throttle rod means assumes an engine idle position.
13. In an internal combustion engine as recited in claim 10 wherein said override control means includes
14. In an internal combustion engine, an induction system for providing a hydrogen rich gas, hydrocarbon fuel and air mixture to said engine to minimize the air pollutants produced by said engine comprising
15. A method of minimizing the air pollution output of an internal combustion engine comprising the steps of
16. A method as recited in claim 15 wherein said step of mixing said air, hydrocarbon fuel and hydrogen rich gas includes
17. A method as recited in claim 16 wherein said step of supplying predetermined quantities of hydrocarbon fuel includes
18. A method as recited in claim 15 wherein said step of controlling said mixing provides only a mixture of a hydrogen rich gas and air when said engine is idling.
Description:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method and means for rendering an internal combustion engine substantially air-pollution free, and more particularly to improvements therein.
2. Description of the Prior Art
A great deal of investigation has gone into the problem of reducing the pollutants emitted by an internal combustion engine which uses a hydrocarbon fuel. It has been recognized that carbon monoxide and other emissions have been found to decrease as the fuel to air ratio is made leaner. The fuel to air ratio is also known as the "equivalence ratio" when it is compared to the stoichiometric value for that fuel. However, in either case as the mixture is made fuel lean, a point is very soon reached where the mixture is no longer flammable. Thus, it appears desirable to have a means to extend the equivalence ratio into the ultra lean region still providing flammability, whereby pollutant emissions from the internal engine may be minimized. Since the load requirements on the engine are variable, it is also necessary to control the equivalence ratio of the fuel-air mixture in an engine over the range of load applied, within a lean mixture range, if the engine is to operate and be substantially pollutant free.
A patent to Blumenberg, U.S. Pat. No. 1,379,077, teaches passing hydrogen and oxygen gases through a heavy hydrocarbon fuel to facilitate its vaporization. A patent to Ricardo, U.S. Pat. No. 1,520,772, teaches mixing a fixed amount of hydrogen and a fixed amount of air with a hydrocarbon fuel whose quantity can be varied from zero to a maximum value over the range from no load to a maximum load. The hydrocarbon and hydrogen are mixed in the absence of air, and then are mixed with the air in the piston of the engine. A patent to Bogan, U.S. Pat. No. 3,653,364, teaches how to produce hydrogen gas and then introduce it into the intake manifold below the carburetor to be mixed with fuel and air. The hydrogen gas is for the purpose of providing higher combustion temperatures thus reducing the quantity of unburned hydrocarbons which are exhausted into the atmosphere.
Mixing hydrogen with a hydrocarbon fuel-air mixture can extend the flammability limits, but no one has taught how to maintain control at all times when hydrogen is used, over an upper and lower boundary on the fuel-air equivalence ratio over the wide range of speed and lower requirements of an automobile engine. This problem becomes complicated by virture of the fact that a mixture of two (or more) fuels are being used for which the "quality" (mass fraction of one fuel in the total) of the fuel is constantly changing. The use of a constant hydrogen flow and unrestricted air flow as taught by the prior art does not solve the problem.
OBJECTS AND SUMMARY OF THE INVENTION
An object of this invention is the provision of an improvement in an internal combustion engine whereby it will produce substantially no air pollutants.
Another object of this invention is the provision of a hydrogen-fuel-air mixing system which minimizes the amount of pollutants produced by an internal combustion engine over its operating range.
Still another object of the present invention is the provision of a system for maintaining a mixture of hydrogen-fuel and air for an internal combustion engine within predetermined boundary limits over the engine operating range.
Yet another object of the invention is the provision of a novel and useful fuel-air mixture control for minimizing the emission of pollutants by an internal combustion engine.
The foregoing and other objects of the invention may be achieved by providing an induction system for an internal combustion engine which uses an internal variable area fuel control valve under throttle control for mixing hydrogen and fuel to maintain predetermined proportions over the operating range of the engine. A throttle override control is used to maintain an upper bound for the mass flow of this mixture relative to any given air flow over the engine operating range. The air flow to the engine is also controlled by the throttle in a manner to assure that the equivalence ratio of the hydrogen-fuel-air mixture is maintained within prescribed bounds and to assure combustible mixtures at high engine speeds when minimal amounts of power are required.
The novel features of the invention are set forth with particularity in the appended claims. The invention will best be understood from the following description when read in conjunction with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a curve illustrating the characteristic correlation between specific emissions (NO x ) and equivalence ratio for a spark internal combustion engine.
FIG. 2 is a schematic drawing of an automobile illustrating placement of the various components of a system in accordance with this invention.
FIG. 3 is a schematic drawing illustrating the layout of an induction system, in accordance with this invention.
FIG. 4 is a drawing of a fuel flow control valve which is in the induction system together with the override control.
FIG. 5 is a view in section illustrating the cam and passages within the fuel flow control valve.
FIG. 6 is a side view of the fuel flow control valve.
FIG. 7 shows a series of curves illustrating the performance bounds of an engine in accordance with this invention.
FIG. 8 is an illustration of a hydrogen generator which may be employed with this invention.
DESCRIPTION OF THE PREFERRED EMBODIMENT OF THE INVENTION
The curve 8, FIG. 1, represents the characteristic correlation between specific emissions, which here is NO x , and equivalence ratio for a spark internal combustion engine. This curve can be modified by any one of a number of operating variables, such as spark advance, compression ratio, engine speed, etc., but if one maximizes performance and efficiency of the combustion process, and normalizes the NO x formation to the heat added during each combustion cycle, then the dominance of stoichiometry in the correlation of NO x formation is always observed. The curve indicates a characteristic maximum occurring at a location (0.83-0.85 equivalence ratio) which is slightly lean from the stoichiometric mixture, (1.0 equivalence ratio).
If in an attempt to control NO x emissions, one operates a conventionally fueled engine (e.g., gasoline) very lean, the engine begins to misfire as the engine approaches the flammability limit of the fuel, (0.7 equivalence ratio). Unfortunately this limit occurs for mixtures with relatively high NO x formation rates and therefore imposes severe limitations on the lean limit operation for conventional fuels. On the other hand, hydrogen is unique in this regard since it exhibits flammability limits that are only 13 percent of its stoichiometric mixture (volume basis). Hence, as indicated in FIG. 1, it is possible to reduce emissions of NO x to essentially zero (less than 1 ppm) simply by using H 2 as the fuel and operating at very low equivalence ratios.
Insofar as the other emissions are concerned, i.e., CO and unburned hydrocarbons, it can be shown that even with carbonaceous fuels, operation near the lean flammability limit is an effective control technique. Obviously, if the fuel is 100% H 2 these fuels are not generated in the combustion process.
Thus, in summary, all fuels exhibit similar emission characteristics, (when properly normalized) which can be reduced to negligible quantities if the combustion process takes place at low equivalence ratios (less than 0.6 for example). Since it is now recognized that these properties are exhibited by all fuels, it follows that mixtures of hydrogen and hydrocarbons will behave in a similar manner with reduction in emissions being limited only by the flammability limits of the mixture. Thus, the well-known laws for flammability limits of fuel mixtures serve as the basis for establishing the lean equivalence ratio bounds that assure flammability while the emission data typified by Curve 8 of FIG. 1 serve to establish the upper limit that will be allowed -- regardless of engine operating conditions.
It has been found that extension of the misfire limits to very lean equivalence ratios with hydrogen fuel also yields significant increases in thermodynamic efficiency of the combustion process. Efficiency is not fuel dependent and the extension of the misfire limit using hydrogen fuel provides efficiency increases of nearly 100% relative to the value obtained at the stoichiometric mixture. Thus, if an engine can be run on hydrogen near its misfire limit, substantial gains in fuel economy are possible.
There is a decrease in specific horsepower (horsepower for a given engine size) which accompanies the decrease in specific energy (heat release per cycle) when an engine is operated with a very lean mixture. It has been observed that this property is not fuel dependent except to limit the operating range (misfire limit) for carbonaceous fuels. When the operating range is extended to the misfire limit of hydrogen, (where minimum emission and maximum efficiency occur), then relative horsepower, (actual horsepower relative to the maximum attainable at that speed), is reduced to 15% of maximum. This is really just a scaling problem since in concept a hydrogen fueled engine could be increased in size to recover the reduced horsepower if that were deemed essential. It will become apparent however that this will not be necessary since an operating system, in accordance with this invention, utilizes this characteristic as a throttling mechanism.
In a particular embodiment of this invention an arrangement is provided wherein hydrogen or a hydrogen rich gas is supplied to an engine as the working fluid of a pneumatic atomizer at a quantative rate sufficient to supply 100 percent of the energy needs for the engine at idle conditions and, by way of illustrating, at an equivalence ratio on the order of 0.15. One of several alternate arrangements would provide for a variable hydrogen flow rate (e.g. proportional to engine speed) which would decrease the amount of air throttling required and hence yield slightly higher overall average operating efficiencies. However, this system would introduce the additional complexity of hydrogen throttling (as well as air throttling) in order to satisfy the low power, high engine speed operating requirements. Hence, in illustration of the invention, the preferred embodiment will utilize the constant and minimal hydrogen flow indicated above.
The pneumatic atomizer is mounted in the intake system and atomizes the liquid fuel being supplied to the engine. The liquid fuel delivery system for supplying fuel to the atomizer is demand controlled to provide varying stoichiometry to the engine. An override of the fuel delivery system, which is air flow sensitive, is provided to limit the maximum mixture equivalence ratio to a predetermined value - on the order of 0.6 -- for example, in order to minimize NO x formation.
FIG. 2 shows an illustration of an automobile 10, having an engine 12, and a tank 14, in which the hydrocarbon fuel is kept. In accordance with this invention, the engine is equipped with an induction tube 16, wherein there is located a fuel flow control valve and throttle override therefore, as well as a pneumatic atomizer, for atomizing the fuel and mixing with hydrogen gas. The fuel flow control valve is controlled from the foot pedal by the operator.
There is also provided an air throttle 18 which is coupled to the fuel flow control valve, and in consonance with fuel flow requirements determines the amount of air permitted to flow to the engine through the induction tube. The hydrocarbon fuel is fed into the pneumatic atomizer in the induction tube through a pipe 22 in which there is a fuel pump 24.
The hydrogen rich gas supply for this invention may come from any source. Any of the known types of hydrogen generators may be employed. However, by way of example, and not by way of limitation, a hydrogen generator of the type described and claimed in an application entitled, "Hydrogen Generator", by Houseman, et al., filed Aug. 20, 1973, Ser. No. 390,049, and assigned to a common assignee. This hydrogen generator generates hydrogen rich gas from the hydrocarbon fuel used by the engine and water using the steam reforming process. A pipe 26 branches from the pipe 22 to couple to a pump 28, which is used to supply hydrocarbon fuel to the hydrogen gas generator 20. A water supply coupled to a pump 34 whereby water is provided to the hydrogen generator. An air pump 36, is also employed for applying air under pressure to the hydrogen generator 20.
Referring now to FIG. 3, there is shown an induction tube 16 in section, which, in accordance with this invention, contains the flow control valve 40, which is controlled by the vehicle operator by means of the throttle rod 42 and rod coupling 43. Hydrocarbon fuel is brought to the flow control valve by tube 26 and hydrogen rich gases are brought from a supply, by the tube 44. The flow control valve 40 is connected to fuel atomizer 46. An override control 48 is used to limit the amount of hydrocarbon fuel being supplied by the flow control valve for any given engine speed in response to pressure in the venturi which is established by the mass air flow to the engine to limit the maximum mixture ratio to a suitable value for suitably inhibiting the formation of NO x . The details of the operation of the override control 48 are discussed in connection with the description of FIG. 4.
The induction tube is coupled to the engine intake manifold 50, which, because it is so well known, is shown as a fragment. The coupling passage between the induction tube and the intake manifold contains an air throttle section in which two air throttle valves, respectively 54, 56, are positioned to control the air intake into the engine, in response to the throttle rod 42 position, which is positioned by the vehicle operation in response to power demands. Two air throttle valves are shown by way of example and not by way of limitation. One or more may be used without departing from the spirit or scope of the claims.
The air throttle 54, 56, is actuated in such a way that the air flow is dictated by a known relation between gasoline flow rate (set by fuel throttle valve) and the air flow in order to assure a mixture bound that is greater than the lean flammability limit of the fuel mix. As the fuel demand (i.e., power load) decreases at high engine speeds the fuel flow control valve is driven toward the closed position. When this happens the air is also throttled in order to maintain the fuel-to-air mass flow within the prescribed flammability limit. However, in view of the fact that the fuel quality is then dominated by hydrogen, the engine will operate at very lean equivalance ratios. Hence, the throttling requirements are approximately one-sixth of those needed for conventional systems. Further, at lessor engine pumping speeds the need for air throttling is proportionately reduced. The combination of these effects provide the basis for the simple mechanically linked system indicated in FIG. 3.
The pneumatic atomizer 46 simultaneously mixes the hydrocarbon fuel with the supply of hydrogen rich gases and produces a very fine mist. The inducted air mixes with this mist and is urged into the intake manifold and then into the engine. The flow control valve, as previously indicated, is demand controlled by the driver using the throttle pedal. The throttle override is used to determine the maximum hydrocarbon fuel flow rate so that it is at a value consistent with an upper limit equivalence ratio of approximately 0.6, which has been determined as the upper bound necessary to best inhibit the formation of NO x . At idle power requirement conditions, no hydrocarbon fuel is employed, the engine is then operating on the hydrogen rich gas.
FIG. 4 is a drawing illustrating the details of the override control. The override control includes a chamber 58 containing an air driven piston 60. A tube, 62, connects the top end of the chamber to the throat of the venturi formed between the wall of the induction tube and the exterior of the flow control valve 40. The piston 60 is attached to a flexible cable 62 which is keyed to a pulley 64 by a dog 65 and held in tension around the periphery of the pulley by means of a spring 66. The spring 66 is attached to the wall of the induction tube. The pulley rotates about a center 67 and rotates with it a cam 68. The cam surface can engage a cam follower 69, mounted on throttle extension 43 to block further motion to the right and thus inhibits flow of additional fuel.
FIG. 4 shows several positions of the extension arm 43, which couples the throttle rod 42 to the flow control valve 40. The throttle closed position is at the extreme left and is represented by the dotted lines. The maximum open throttle at maximum RPM is at the extreme right and is represented by the dotted lines. The solid line position between the two, represents maximum throttle at idle RPM. The pressure of the air in the venturi throat section of the induction tube determines the position of the piston 60. The piston pulls against the spring 66 in response to the vacuum caused by the venturi and thus, variations in air pressure cause different piston positions which cause rotation of pulley 64 and with it cam 68. In this manner, the position assumed by the cam is determined by the air pressure or air depression established at the venturi by the air flow to the engine. The cam position determines the maximum amount of hydrocarbon fuel which can be provided to the engine for any given engine speed. This is established in compliance with a predetermined relationship to the air flow rate. The air flow rate is detected from the static pressure produced in the throat of the venturi. By this means, the equivalence ratio of the fuel plus air mixture can be limited to a selected maximum value, which has been found to be on the order of 0.6 at which value production of NO x is substantially eliminated.
FIGS. 5 and 6 respectively show a cross-sectional view of the pneumatic atomizer with an integral flow control valve and a cross-sectional view along the lines 5--5 of FIG. 4. The hydrocarbon fuel line 22 feeds the fuel into a substantially circular opening, defined by walls 70, within which space a valve member 72, is rotated by the throttle 43. The opening 70 communicates with an exit passageway 74, which ends in an exit passage 76, which is considerably narrower than the passageway 74.
The line 24 containing the pneumatic atomizer working fluid communicates with a frustrated conicular region, defined by the walls 78, 80, which surrounds the exit passageway 76 which is concentric therewith. The conicular region terminates in an opening 82. The narrow exit passageway 76 ends just short of the opening 82, as a result of which the hydrogen gas and the hydrocarbon fuel spray mix at the exit opening 82 and are ejected into the induction passageway of the induction tube.
It should be noted that the shape of the valve member 72 is such that when the throttle arm is in the throttle closed position, it blocks the passageway 74 and therefore, no hydrocarbon fuel will be supplied to the engine. The shape of the valve member is contoured to provide a desired rate of flow of hydrocarbon fuel with throttle position, whereby engine speed may be controlled.
FIG. 7 presents a series of curves illustrating equivalence ratio, (ER), throttling of a spark ignition engine. The curves labeled ER=0.1 through 1.0 are for wide open throttle operating conditions and assume sufficient hydrogen available to satisfy the horsepower requirements illustrated by the 0.1 ER line. These curves are analogous to a conventional representation where they would represent mass flow throttling to give respectively 25, 35, 63, 87, and 97 percent of the maximum power available at any given engine speed. It is seen that with equivalence ratio throttling, engine power is varied on demand by varying fuel flow while equivalence ratio is allowed to vary with either fuel flow or engine speed. In conventional engines, power is adjusted by changing the mass density of the combustion charge (and hence energy) for a substantially constant mixture ratio. Superimposed on this operating map is the flammability limit curve which bounds the cross hatched region where air throttling is required when the hydrogen flow is constant and equal to idle energy requirements. In this system, the engine burns a fuel that is "pure" hydrogen at idle and a fuel that is a mixture of perhaps 90% liquid fuel and 10% hydrogen at maximum horsepower, (also maximum equivalence ratio and high engine speed), condition. For the low load conditions where the bulk of the driving is done, it is estimated that the fuel mixture would vary between 5 and 25% hydrogen and hence emissions and efficiency tend to be simultaneously optimized.
FIG. 8 is a drawing illustrating a hydrogen gas generator which may be employed to provide hydrogen rich gas to an engine, in accordance with this invention. This is shown by way of illustration of hydrogen rich gas and not by way of limitation. An electric motor 90 drives an air pump 36, a gasoline pump 28 and a water pump 34 to provide these fluids to the gas generator 20 over the respective pipes 92, 94 and 96. The hydrogen rich gas generator includes two portions respectively 98 and 100 which include chambers which have the same axis and communicate at one end with each other.
The first portion has cylindrical walls 102 which enclose a first chamber. At one end of this chamber is a pneumatic atomizer 104 to which air, as the operating fluid, and the hydrocarbon fuel are supplied to atomize the fuel. The air is supplied directly from the high pressure discharge of the air pump 36.
The second portion 100 of the hydrogen generator has outer cylindrical walls 105. These enclose inner cylindrical walls, which are spaced therefrom and define a second chamber, which is the burning chamber. Between the first and second walls is a spiral wall 108, which defines a spiral passage. Air is pumped into one end of the spiral passage over the pipe 92, to be directed around the inner walls 106 and thus, is preheated by the inner chamber walls which surround the burning chamber.
The fuel-air mixture created in the first chamber is passed into the second chamber through an air swirler. This comprises a toroid with a plurality of passages which are angularly directed from the outer periphery of the toroid ring to the central opening. Preheated air from the spiral passage passes through these angularly directed openings and causes the air-fuel mixture passing through the central opening of the air swirler 112 to be swirled as it enters into the burning chamber. A spark plug 114 ignites this mixture and the hot gases which are created pass further into the chamber where there is sprayed a mixture of gasoline and water through a second pneumatic atomizer 116.
The gasoline and water are supplied to the pneumatic atomizer over pipes 94 and 96. High pressure air is also provided as the atomizer working fluid over a pipe 118.
The hot gases in the second chamber convert the water spray in the fuel-water mixture into steam. The fuel is vaporized and a steam reforming action takes place within the reactor space formed by the burning chamber. Hydrogen rich gas passes out of the opening 120 to the induction tube of the engine.
For start up, the vehicle ignition switch will also energize the motor 90 which causes delivery of air to the hydrogen generator. After a suitable delay interval to allow air pressure to build up to a predetermined value, such as 5 psi, or when the pressure is sensed by a pressure sensitive switch, the engine cranking system is activated, the engine and hydrogen generator ignition systems are activated and the magnetic clutch that couples the water and fuel pumps, respectively 34, 28, to the motor drive are activated. This produces hydrogen substantially instantaneously and the engine then bootstraps itself to the idle condition.
There has accordingly been described and shown herein a novel and useful system for operating an internal combustion engine in a manner to substantially eliminate combustion products which cause air pollution, while effectively reducing the amount of hydrocarbon fuel which is consumed.
In the foregoing application, and in the claims, it should be understood that the word "hydrogen" is used as an abbreviation for "hydrogen rich gas." The invention does not require pure hydrogen gas. The hydrogen rich gas may contain considerable fractions of inert and flammable material.
1. Field of the Invention
The present invention relates to a method and means for rendering an internal combustion engine substantially air-pollution free, and more particularly to improvements therein.
2. Description of the Prior Art
A great deal of investigation has gone into the problem of reducing the pollutants emitted by an internal combustion engine which uses a hydrocarbon fuel. It has been recognized that carbon monoxide and other emissions have been found to decrease as the fuel to air ratio is made leaner. The fuel to air ratio is also known as the "equivalence ratio" when it is compared to the stoichiometric value for that fuel. However, in either case as the mixture is made fuel lean, a point is very soon reached where the mixture is no longer flammable. Thus, it appears desirable to have a means to extend the equivalence ratio into the ultra lean region still providing flammability, whereby pollutant emissions from the internal engine may be minimized. Since the load requirements on the engine are variable, it is also necessary to control the equivalence ratio of the fuel-air mixture in an engine over the range of load applied, within a lean mixture range, if the engine is to operate and be substantially pollutant free.
A patent to Blumenberg, U.S. Pat. No. 1,379,077, teaches passing hydrogen and oxygen gases through a heavy hydrocarbon fuel to facilitate its vaporization. A patent to Ricardo, U.S. Pat. No. 1,520,772, teaches mixing a fixed amount of hydrogen and a fixed amount of air with a hydrocarbon fuel whose quantity can be varied from zero to a maximum value over the range from no load to a maximum load. The hydrocarbon and hydrogen are mixed in the absence of air, and then are mixed with the air in the piston of the engine. A patent to Bogan, U.S. Pat. No. 3,653,364, teaches how to produce hydrogen gas and then introduce it into the intake manifold below the carburetor to be mixed with fuel and air. The hydrogen gas is for the purpose of providing higher combustion temperatures thus reducing the quantity of unburned hydrocarbons which are exhausted into the atmosphere.
Mixing hydrogen with a hydrocarbon fuel-air mixture can extend the flammability limits, but no one has taught how to maintain control at all times when hydrogen is used, over an upper and lower boundary on the fuel-air equivalence ratio over the wide range of speed and lower requirements of an automobile engine. This problem becomes complicated by virture of the fact that a mixture of two (or more) fuels are being used for which the "quality" (mass fraction of one fuel in the total) of the fuel is constantly changing. The use of a constant hydrogen flow and unrestricted air flow as taught by the prior art does not solve the problem.
OBJECTS AND SUMMARY OF THE INVENTION
An object of this invention is the provision of an improvement in an internal combustion engine whereby it will produce substantially no air pollutants.
Another object of this invention is the provision of a hydrogen-fuel-air mixing system which minimizes the amount of pollutants produced by an internal combustion engine over its operating range.
Still another object of the present invention is the provision of a system for maintaining a mixture of hydrogen-fuel and air for an internal combustion engine within predetermined boundary limits over the engine operating range.
Yet another object of the invention is the provision of a novel and useful fuel-air mixture control for minimizing the emission of pollutants by an internal combustion engine.
The foregoing and other objects of the invention may be achieved by providing an induction system for an internal combustion engine which uses an internal variable area fuel control valve under throttle control for mixing hydrogen and fuel to maintain predetermined proportions over the operating range of the engine. A throttle override control is used to maintain an upper bound for the mass flow of this mixture relative to any given air flow over the engine operating range. The air flow to the engine is also controlled by the throttle in a manner to assure that the equivalence ratio of the hydrogen-fuel-air mixture is maintained within prescribed bounds and to assure combustible mixtures at high engine speeds when minimal amounts of power are required.
The novel features of the invention are set forth with particularity in the appended claims. The invention will best be understood from the following description when read in conjunction with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a curve illustrating the characteristic correlation between specific emissions (NO x ) and equivalence ratio for a spark internal combustion engine.
FIG. 2 is a schematic drawing of an automobile illustrating placement of the various components of a system in accordance with this invention.
FIG. 3 is a schematic drawing illustrating the layout of an induction system, in accordance with this invention.
FIG. 4 is a drawing of a fuel flow control valve which is in the induction system together with the override control.
FIG. 5 is a view in section illustrating the cam and passages within the fuel flow control valve.
FIG. 6 is a side view of the fuel flow control valve.
FIG. 7 shows a series of curves illustrating the performance bounds of an engine in accordance with this invention.
FIG. 8 is an illustration of a hydrogen generator which may be employed with this invention.
DESCRIPTION OF THE PREFERRED EMBODIMENT OF THE INVENTION
The curve 8, FIG. 1, represents the characteristic correlation between specific emissions, which here is NO x , and equivalence ratio for a spark internal combustion engine. This curve can be modified by any one of a number of operating variables, such as spark advance, compression ratio, engine speed, etc., but if one maximizes performance and efficiency of the combustion process, and normalizes the NO x formation to the heat added during each combustion cycle, then the dominance of stoichiometry in the correlation of NO x formation is always observed. The curve indicates a characteristic maximum occurring at a location (0.83-0.85 equivalence ratio) which is slightly lean from the stoichiometric mixture, (1.0 equivalence ratio).
If in an attempt to control NO x emissions, one operates a conventionally fueled engine (e.g., gasoline) very lean, the engine begins to misfire as the engine approaches the flammability limit of the fuel, (0.7 equivalence ratio). Unfortunately this limit occurs for mixtures with relatively high NO x formation rates and therefore imposes severe limitations on the lean limit operation for conventional fuels. On the other hand, hydrogen is unique in this regard since it exhibits flammability limits that are only 13 percent of its stoichiometric mixture (volume basis). Hence, as indicated in FIG. 1, it is possible to reduce emissions of NO x to essentially zero (less than 1 ppm) simply by using H 2 as the fuel and operating at very low equivalence ratios.
Insofar as the other emissions are concerned, i.e., CO and unburned hydrocarbons, it can be shown that even with carbonaceous fuels, operation near the lean flammability limit is an effective control technique. Obviously, if the fuel is 100% H 2 these fuels are not generated in the combustion process.
Thus, in summary, all fuels exhibit similar emission characteristics, (when properly normalized) which can be reduced to negligible quantities if the combustion process takes place at low equivalence ratios (less than 0.6 for example). Since it is now recognized that these properties are exhibited by all fuels, it follows that mixtures of hydrogen and hydrocarbons will behave in a similar manner with reduction in emissions being limited only by the flammability limits of the mixture. Thus, the well-known laws for flammability limits of fuel mixtures serve as the basis for establishing the lean equivalence ratio bounds that assure flammability while the emission data typified by Curve 8 of FIG. 1 serve to establish the upper limit that will be allowed -- regardless of engine operating conditions.
It has been found that extension of the misfire limits to very lean equivalence ratios with hydrogen fuel also yields significant increases in thermodynamic efficiency of the combustion process. Efficiency is not fuel dependent and the extension of the misfire limit using hydrogen fuel provides efficiency increases of nearly 100% relative to the value obtained at the stoichiometric mixture. Thus, if an engine can be run on hydrogen near its misfire limit, substantial gains in fuel economy are possible.
There is a decrease in specific horsepower (horsepower for a given engine size) which accompanies the decrease in specific energy (heat release per cycle) when an engine is operated with a very lean mixture. It has been observed that this property is not fuel dependent except to limit the operating range (misfire limit) for carbonaceous fuels. When the operating range is extended to the misfire limit of hydrogen, (where minimum emission and maximum efficiency occur), then relative horsepower, (actual horsepower relative to the maximum attainable at that speed), is reduced to 15% of maximum. This is really just a scaling problem since in concept a hydrogen fueled engine could be increased in size to recover the reduced horsepower if that were deemed essential. It will become apparent however that this will not be necessary since an operating system, in accordance with this invention, utilizes this characteristic as a throttling mechanism.
In a particular embodiment of this invention an arrangement is provided wherein hydrogen or a hydrogen rich gas is supplied to an engine as the working fluid of a pneumatic atomizer at a quantative rate sufficient to supply 100 percent of the energy needs for the engine at idle conditions and, by way of illustrating, at an equivalence ratio on the order of 0.15. One of several alternate arrangements would provide for a variable hydrogen flow rate (e.g. proportional to engine speed) which would decrease the amount of air throttling required and hence yield slightly higher overall average operating efficiencies. However, this system would introduce the additional complexity of hydrogen throttling (as well as air throttling) in order to satisfy the low power, high engine speed operating requirements. Hence, in illustration of the invention, the preferred embodiment will utilize the constant and minimal hydrogen flow indicated above.
The pneumatic atomizer is mounted in the intake system and atomizes the liquid fuel being supplied to the engine. The liquid fuel delivery system for supplying fuel to the atomizer is demand controlled to provide varying stoichiometry to the engine. An override of the fuel delivery system, which is air flow sensitive, is provided to limit the maximum mixture equivalence ratio to a predetermined value - on the order of 0.6 -- for example, in order to minimize NO x formation.
FIG. 2 shows an illustration of an automobile 10, having an engine 12, and a tank 14, in which the hydrocarbon fuel is kept. In accordance with this invention, the engine is equipped with an induction tube 16, wherein there is located a fuel flow control valve and throttle override therefore, as well as a pneumatic atomizer, for atomizing the fuel and mixing with hydrogen gas. The fuel flow control valve is controlled from the foot pedal by the operator.
There is also provided an air throttle 18 which is coupled to the fuel flow control valve, and in consonance with fuel flow requirements determines the amount of air permitted to flow to the engine through the induction tube. The hydrocarbon fuel is fed into the pneumatic atomizer in the induction tube through a pipe 22 in which there is a fuel pump 24.
The hydrogen rich gas supply for this invention may come from any source. Any of the known types of hydrogen generators may be employed. However, by way of example, and not by way of limitation, a hydrogen generator of the type described and claimed in an application entitled, "Hydrogen Generator", by Houseman, et al., filed Aug. 20, 1973, Ser. No. 390,049, and assigned to a common assignee. This hydrogen generator generates hydrogen rich gas from the hydrocarbon fuel used by the engine and water using the steam reforming process. A pipe 26 branches from the pipe 22 to couple to a pump 28, which is used to supply hydrocarbon fuel to the hydrogen gas generator 20. A water supply coupled to a pump 34 whereby water is provided to the hydrogen generator. An air pump 36, is also employed for applying air under pressure to the hydrogen generator 20.
Referring now to FIG. 3, there is shown an induction tube 16 in section, which, in accordance with this invention, contains the flow control valve 40, which is controlled by the vehicle operator by means of the throttle rod 42 and rod coupling 43. Hydrocarbon fuel is brought to the flow control valve by tube 26 and hydrogen rich gases are brought from a supply, by the tube 44. The flow control valve 40 is connected to fuel atomizer 46. An override control 48 is used to limit the amount of hydrocarbon fuel being supplied by the flow control valve for any given engine speed in response to pressure in the venturi which is established by the mass air flow to the engine to limit the maximum mixture ratio to a suitable value for suitably inhibiting the formation of NO x . The details of the operation of the override control 48 are discussed in connection with the description of FIG. 4.
The induction tube is coupled to the engine intake manifold 50, which, because it is so well known, is shown as a fragment. The coupling passage between the induction tube and the intake manifold contains an air throttle section in which two air throttle valves, respectively 54, 56, are positioned to control the air intake into the engine, in response to the throttle rod 42 position, which is positioned by the vehicle operation in response to power demands. Two air throttle valves are shown by way of example and not by way of limitation. One or more may be used without departing from the spirit or scope of the claims.
The air throttle 54, 56, is actuated in such a way that the air flow is dictated by a known relation between gasoline flow rate (set by fuel throttle valve) and the air flow in order to assure a mixture bound that is greater than the lean flammability limit of the fuel mix. As the fuel demand (i.e., power load) decreases at high engine speeds the fuel flow control valve is driven toward the closed position. When this happens the air is also throttled in order to maintain the fuel-to-air mass flow within the prescribed flammability limit. However, in view of the fact that the fuel quality is then dominated by hydrogen, the engine will operate at very lean equivalance ratios. Hence, the throttling requirements are approximately one-sixth of those needed for conventional systems. Further, at lessor engine pumping speeds the need for air throttling is proportionately reduced. The combination of these effects provide the basis for the simple mechanically linked system indicated in FIG. 3.
The pneumatic atomizer 46 simultaneously mixes the hydrocarbon fuel with the supply of hydrogen rich gases and produces a very fine mist. The inducted air mixes with this mist and is urged into the intake manifold and then into the engine. The flow control valve, as previously indicated, is demand controlled by the driver using the throttle pedal. The throttle override is used to determine the maximum hydrocarbon fuel flow rate so that it is at a value consistent with an upper limit equivalence ratio of approximately 0.6, which has been determined as the upper bound necessary to best inhibit the formation of NO x . At idle power requirement conditions, no hydrocarbon fuel is employed, the engine is then operating on the hydrogen rich gas.
FIG. 4 is a drawing illustrating the details of the override control. The override control includes a chamber 58 containing an air driven piston 60. A tube, 62, connects the top end of the chamber to the throat of the venturi formed between the wall of the induction tube and the exterior of the flow control valve 40. The piston 60 is attached to a flexible cable 62 which is keyed to a pulley 64 by a dog 65 and held in tension around the periphery of the pulley by means of a spring 66. The spring 66 is attached to the wall of the induction tube. The pulley rotates about a center 67 and rotates with it a cam 68. The cam surface can engage a cam follower 69, mounted on throttle extension 43 to block further motion to the right and thus inhibits flow of additional fuel.
FIG. 4 shows several positions of the extension arm 43, which couples the throttle rod 42 to the flow control valve 40. The throttle closed position is at the extreme left and is represented by the dotted lines. The maximum open throttle at maximum RPM is at the extreme right and is represented by the dotted lines. The solid line position between the two, represents maximum throttle at idle RPM. The pressure of the air in the venturi throat section of the induction tube determines the position of the piston 60. The piston pulls against the spring 66 in response to the vacuum caused by the venturi and thus, variations in air pressure cause different piston positions which cause rotation of pulley 64 and with it cam 68. In this manner, the position assumed by the cam is determined by the air pressure or air depression established at the venturi by the air flow to the engine. The cam position determines the maximum amount of hydrocarbon fuel which can be provided to the engine for any given engine speed. This is established in compliance with a predetermined relationship to the air flow rate. The air flow rate is detected from the static pressure produced in the throat of the venturi. By this means, the equivalence ratio of the fuel plus air mixture can be limited to a selected maximum value, which has been found to be on the order of 0.6 at which value production of NO x is substantially eliminated.
FIGS. 5 and 6 respectively show a cross-sectional view of the pneumatic atomizer with an integral flow control valve and a cross-sectional view along the lines 5--5 of FIG. 4. The hydrocarbon fuel line 22 feeds the fuel into a substantially circular opening, defined by walls 70, within which space a valve member 72, is rotated by the throttle 43. The opening 70 communicates with an exit passageway 74, which ends in an exit passage 76, which is considerably narrower than the passageway 74.
The line 24 containing the pneumatic atomizer working fluid communicates with a frustrated conicular region, defined by the walls 78, 80, which surrounds the exit passageway 76 which is concentric therewith. The conicular region terminates in an opening 82. The narrow exit passageway 76 ends just short of the opening 82, as a result of which the hydrogen gas and the hydrocarbon fuel spray mix at the exit opening 82 and are ejected into the induction passageway of the induction tube.
It should be noted that the shape of the valve member 72 is such that when the throttle arm is in the throttle closed position, it blocks the passageway 74 and therefore, no hydrocarbon fuel will be supplied to the engine. The shape of the valve member is contoured to provide a desired rate of flow of hydrocarbon fuel with throttle position, whereby engine speed may be controlled.
FIG. 7 presents a series of curves illustrating equivalence ratio, (ER), throttling of a spark ignition engine. The curves labeled ER=0.1 through 1.0 are for wide open throttle operating conditions and assume sufficient hydrogen available to satisfy the horsepower requirements illustrated by the 0.1 ER line. These curves are analogous to a conventional representation where they would represent mass flow throttling to give respectively 25, 35, 63, 87, and 97 percent of the maximum power available at any given engine speed. It is seen that with equivalence ratio throttling, engine power is varied on demand by varying fuel flow while equivalence ratio is allowed to vary with either fuel flow or engine speed. In conventional engines, power is adjusted by changing the mass density of the combustion charge (and hence energy) for a substantially constant mixture ratio. Superimposed on this operating map is the flammability limit curve which bounds the cross hatched region where air throttling is required when the hydrogen flow is constant and equal to idle energy requirements. In this system, the engine burns a fuel that is "pure" hydrogen at idle and a fuel that is a mixture of perhaps 90% liquid fuel and 10% hydrogen at maximum horsepower, (also maximum equivalence ratio and high engine speed), condition. For the low load conditions where the bulk of the driving is done, it is estimated that the fuel mixture would vary between 5 and 25% hydrogen and hence emissions and efficiency tend to be simultaneously optimized.
FIG. 8 is a drawing illustrating a hydrogen gas generator which may be employed to provide hydrogen rich gas to an engine, in accordance with this invention. This is shown by way of illustration of hydrogen rich gas and not by way of limitation. An electric motor 90 drives an air pump 36, a gasoline pump 28 and a water pump 34 to provide these fluids to the gas generator 20 over the respective pipes 92, 94 and 96. The hydrogen rich gas generator includes two portions respectively 98 and 100 which include chambers which have the same axis and communicate at one end with each other.
The first portion has cylindrical walls 102 which enclose a first chamber. At one end of this chamber is a pneumatic atomizer 104 to which air, as the operating fluid, and the hydrocarbon fuel are supplied to atomize the fuel. The air is supplied directly from the high pressure discharge of the air pump 36.
The second portion 100 of the hydrogen generator has outer cylindrical walls 105. These enclose inner cylindrical walls, which are spaced therefrom and define a second chamber, which is the burning chamber. Between the first and second walls is a spiral wall 108, which defines a spiral passage. Air is pumped into one end of the spiral passage over the pipe 92, to be directed around the inner walls 106 and thus, is preheated by the inner chamber walls which surround the burning chamber.
The fuel-air mixture created in the first chamber is passed into the second chamber through an air swirler. This comprises a toroid with a plurality of passages which are angularly directed from the outer periphery of the toroid ring to the central opening. Preheated air from the spiral passage passes through these angularly directed openings and causes the air-fuel mixture passing through the central opening of the air swirler 112 to be swirled as it enters into the burning chamber. A spark plug 114 ignites this mixture and the hot gases which are created pass further into the chamber where there is sprayed a mixture of gasoline and water through a second pneumatic atomizer 116.
The gasoline and water are supplied to the pneumatic atomizer over pipes 94 and 96. High pressure air is also provided as the atomizer working fluid over a pipe 118.
The hot gases in the second chamber convert the water spray in the fuel-water mixture into steam. The fuel is vaporized and a steam reforming action takes place within the reactor space formed by the burning chamber. Hydrogen rich gas passes out of the opening 120 to the induction tube of the engine.
For start up, the vehicle ignition switch will also energize the motor 90 which causes delivery of air to the hydrogen generator. After a suitable delay interval to allow air pressure to build up to a predetermined value, such as 5 psi, or when the pressure is sensed by a pressure sensitive switch, the engine cranking system is activated, the engine and hydrogen generator ignition systems are activated and the magnetic clutch that couples the water and fuel pumps, respectively 34, 28, to the motor drive are activated. This produces hydrogen substantially instantaneously and the engine then bootstraps itself to the idle condition.
There has accordingly been described and shown herein a novel and useful system for operating an internal combustion engine in a manner to substantially eliminate combustion products which cause air pollution, while effectively reducing the amount of hydrocarbon fuel which is consumed.
In the foregoing application, and in the claims, it should be understood that the word "hydrogen" is used as an abbreviation for "hydrogen rich gas." The invention does not require pure hydrogen gas. The hydrogen rich gas may contain considerable fractions of inert and flammable material.