Field of the Invention

[001] The present disclosure relates to combustion cycles, more specifically to reactant controlled compression ignition ("RCCI") systems.

Background

[002] Combustion engines are used in countless vehicles and powered devices. Fuel is becoming ever more expensive and pollution is being ever more controlled. For at least these reasons, it is clear that the demand will only increase for combustion engines that perform with maximum efficiency and minimal pollution.

[003] Compression Ignition (CI) engines are of high interest because of their higher working efficiency as compared to spark ignition (SI) or gasoline engines. One of the challenges with CI engines is to control the combustion temperature - higher combustion temperatures result in more complete fuel utilization (i.e., less soot is generated) and greater efficiency but higher temperatures also produce more nitrogen oxide ( Ox) pollutants.

[004] Homogeneous charge compression ignition (HCCI) systems, which seek to modify the combustion chemistry in order to achieve a more complete combustion reaction, can increase efficiency and reduce pollutants. However, at present, there are no sufficient systems or methods for starting and/or sustaining HCCI.

[005] Typically, in HCCI systems a fraction of the exhaust gases or combustion products from the previous combustion cycle are fed back or retained in the cylinder in order to modulate the combustion reaction and consume residual reactants. Secondary fuel reactants (SFR) have been employed that have different reactivities as compared to the primary fuel reactant (PFR) to modulate the combustion recation and consume residual reactants. HCCI engines that operate predomintantly on this fuel mixing principle are termed reactively controlled. Conventional wisdom in the art is to base the amount of secondary fuel used on the volume of primary fuel used in the system. [006] For CI engines there are two known types of systems (known as dual fuel systems) which utilize a secondary fuel to achieve fuel savings (i.e., replacement and enhancement). For replacement systems some percentage of the primary fuel is replaced by a secondary fuel. Typically this is in the range 15% to 80% of secondary fuel used. In practice the efficiency of the engine when operated on a plurality of fuels at these levels is lower than when operated on the primary fuel alone.

[007] Enhancement systems use a much lower percentage of secondary fuel to act as an accelerant (rate) and/or to enhance the consumption of fuel to improve the combustion of the primary fuel (typically less than about 15%). Therefore, the secondary fuel (which may be a lower or higher cost than the primary fuel by volume) acts as an ignition improver or combustion enhancer or both. The combustion improvement is attributed to a number of factors, which include but is not limited to: faster burn, reduced engine knock, advanced ignition timing, more homogenous combustion, more even cylinder pressure profile and faster progression of the flame front.

[008] In both of these systems the quantity of the primary fuel employed is one of the major factors used in the calculation of the quantity of the secondary fuel required. This is also true of systems which use estimated engine power to calculate the quantity of secondary fuel required as this will be directly derived from the amount of primary fuel employed.

[009] Thus, owing to concerns over fuel energy supplies, and the environmental impact of engine emissions, there is a significant need for engines that provide high efficiencies while meeting or exceeding current emission standards. However, to achieve all of the benefits of changed combustion chemistry, to maximise those benefits, and to ensure that they occur throughout the full range of engine operation requires a control strategy and control system that is based on the underlying chemical processes, which are part of the overall combustion process not just the engine operation.

Summary

[0010] Presently described are compression ignition engine system(s) and methods in which the stoichiometric ratios of the primary fuel reactant (PFR), oxygen reactant (OxR) and secondary fuel reactant (SFR) are tightly controlled such that engine efficiency is maximized across all operational states (rpms and loads) of the CI engine while using less SFR. When the correct quantity of reactants dictated by the stoichiometric ratios required for overall combustion are introduced into a CI engine, the engine exhibits characteristics of both a CI (diesel) engine and a SI (gasoline) engine ("hybrid combustion mode"). The stoichiometric ratio is defined as the correct amount of reactants for the instantaneous demands of the engine combustion.

[0011] In at least one aspect of this disclosure, a method of starting and/or stabilizing a reactant controlled compression ignition (RCCI) combustion system includes determining an amount of intake oxygen (0 ₂ ) flowing into a cylinder of an engine from an engine intake during an intake stage of the cylinder, calculating an amount of primary fuel reactant (PFR) and/or a secondary fuel reactant (SFR) to be injected into the cylinder to achieve a stoichiometric oxygen-to-fuel ratio, introducing the SFR into at least one cylinder before or during a compression stage of the at least one cylinder such that the SFR and the 0 ₂ create a compressed mixture after the compression stage, combining the PFR with the compressed mixture, wherein the PFR and the compressed mixture homogenously burn upon ignition.

[0012] The products of combustion can be purged during the exhaust cycle such that there are approximately no residual reactants present in the cylinder for a subsequent compression and combustion reaction, thereby stabilizing the RCCI combustion system because it is not dependent on the previous combustion cycle.

[0013] In certain embodiments, the method may further include a step of allowing the PFR to ignite via compression or chemical reaction with the compressed mixture. In additional embodiments, the method can further include a step of igniting the PFR using a spark plug after the PFR has been introduced

[0014] In other embodiments, the step of combining the PFR can include at least one of injecting the PFR in the intake air, fumigation, direct injection of the PFR into the cylinder or a combination thereof.

[0015] In any of the aspects or embodiments as described herein, the SFR may comprise, consist essentially of, or consist of liquefied petroleum gas (LPG).

[0016] In additional embodiments, the step of introducing the SFR can include using engine oil as the transport medium. As such, in certain embodiments, the step of introducing the SFR can include introducing an additive quantity of SFR such that the SFR can be considered an additive. [0017] In any of the aspects or embodiments described herein, the PFR can include any desired fuel, e.g., diesel fuel, biodiesel, ethanol, gasoline, butane, isooctane, ethyltoluene, MTBE, kerosene, LPG, propane, coal tar, naptha, propane and the like or a combination thereof.

[0018] In an additional aspect, the disclosure provides methods as described herein and further including a step of determining or measuring an amount of a product of combustion in an exhaust and modifying the timing and/or amount of at least one of 0 ₂ intake, the amount of SFR, the amount of PFR or a combination thereof in response thereto to minimize pollution and/or to increase efficiency or engine output.

[0019] In additional aspects, the disclosure provides a combustion system comprising a reciprocating engine having at least one cylinder and an air intake for providing intake oxygen (0 ₂ ) to the at least one cylinder, a fuel introduction system comprising fuel injectors for a primary fuel reactant (PFR) and a secondary fuel reactant (SFR), and a control system including a memory having computer readable instructions stored thereon for starting and/or stabilizing a reactant controlled compression ignition (RCCI) combustion system, the instructions including one or more steps of an embodiment of the method disclosed herein.

[0020] The preceding general areas of utility are given by way of example only and are not intended to be limiting on the scope of the present disclosure and appended claims. Additional objects and advantages associated with the compositions, methods, and processes of the present invention will be appreciated by one of ordinary skill in the art in light of the instant claims, description, drawings, and examples. For example, the various aspects and embodiments of the invention may be utilized in numerous combinations, all of which are expressly contemplated by the present description. These additional advantages, objects and embodiments are expressly included within the scope of the present invention. The publications and other materials used herein to illuminate the background of the invention, and in particular cases, to provide additional details respecting the practice, are incorporated by reference.

Brief Description of the Drawings

[0021] The accompanying drawings, which are incorporated into and form a part of the specification, illustrate several embodiments of the present invention and, together with the description, serve to explain the principles of the invention. The drawings are only for the purpose of illustrating an embodiment of the invention and are not to be construed as limiting the invention. Further objects, features and advantages of the invention will become apparent from the following detailed description taken in conjunction with the accompanying figures showing illustrative embodiments of the invention, in which:

[0022] Fig. 1 is a schematic view of a combustion system in accordance with this disclosure, shown at the end of the intake stage;

[0023] Fig. 2 is a schematic view of portions of the combustion system of Fig. 1 , shown at the end of the compression stage;

[0024] Fig. 3 is a schematic view of portions of the combustion system of Fig. 1 , shown at the PFR introduction/ignition stage;

[0025] Fig. 4 is a schematic view of portions of the combustion system of Fig. 1 , shown during homogeneous combustion and expansion of the reactants; and

[0026] Fig. 5 is a schematic view of portions of the combustion system of Fig. 1 , shown at the exhaust stage.

Detailed Description

[0027] The following is a detailed description provided to aid those skilled in the art in practicing the present invention. Those of ordinary skill in the art may make modifications and variations in the embodiments described herein without departing from the spirit or scope of the present disclosure. All publications, patent applications, patents, figures and other references mentioned herein are expressly incorporated by reference in their entirety.

[0028] The present description provides systems and methods that surprisingly and unexpectedly improve the fuel efficiency and the emissions of a compression ignition (CI) or spark ignition engine or both by modifying the combustion chemistry. This is achieved by introducing controlled amounts of combustion reactants (primary fuel reactants (PFR), secondary fuel reactants (SFR) and oxgen) into the combustion chamber of the engine such that the reactants are stoichiometrically balanced with respect to each other at all times during the combustion process. The method(s) result in increased combustion efficiency, mechanical efficiency, and thermodynamic efficiency, which results in enhanced engine performance and consequent fuel savings. The enhanced combustion mode that is achieved according to the systems and methods as described herein is referred to "reactant controlled combustion ignition" or RCCI.

[0029] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used in the description is for describing particular embodiments only and is not intended to be limiting of the invention.

[0030] Where a range of values is provided, it is understood that each intervening value, to the tenth of the unit of the lower limit unless the context clearly dictates otherwise (such as in the case of a group containing a number of carbon atoms in which case each carbon atom number falling within the range is provided), between the upper and lower limit of that range and any other stated or intervening value in that stated range is encompassed within the invention. The upper and lower limits of these smaller ranges may independently be included in the smaller ranges is also encompassed within the invention, subject to any specifically excluded limit in the stated range. Where the stated range includes one or both of the limits, ranges excluding either both of those included limits are also included in the invention.

[0031] The following terms are used to describe the present invention. In instances where a term is not specifically defined herein, that term is given an art-recognized meaning by those of ordinary skill applying that term in context to its use in describing the present invention.

[0032] The articles "a" and "an" as used herein and in the appended claims are used herein to refer to one or to more than one (i.e., to at least one) of the grammatical object of the article unless the context clearly indicates otherwise. By way of example, "an element" means one element or more than one element.

[0033] The phrase "and/or," as used herein in the specification and in the claims, should be understood to mean "either or both" of the elements so conjoined, i.e., elements that are conjunctively present in some cases and disjunctively present in other cases. Multiple elements listed with "and/or" should be construed in the same fashion, i.e., "one or more" of the elements so conjoined. Other elements may optionally be present other than the elements specifically identified by the "and/or" clause, whether related or unrelated to those elements specifically identified. Thus, as a non-limiting example, a reference to "A and/or B", when used in conjunction with open-ended language such as "comprising" can refer, in one embodiment, to A only (optionally including elements other than B); in another embodiment, to B only (optionally including elements other than A); in yet another embodiment, to both A and B (optionally including other elements); etc.

[0034] As used herein in the specification and in the claims, "or" should be understood to have the same meaning as "and/or" as defined above. For example, when separating items in a list, "or" or "and/or" shall be interpreted as being inclusive, i.e., the inclusion of at least one, but also including more than one, of a number or list of elements, and, optionally, additional unlisted items. Only terms clearly indicated to the contrary, such as "only one of or "exactly one of," or, when used in the claims, "consisting of," will refer to the inclusion of exactly one element of a number or list of elements. In general, the term "or" as used herein shall only be interpreted as indicating exclusive alternatives (i.e., "one or the other but not both") when preceded by terms of exclusivity, such as "either," "one of," "only one of," or "exactly one of."

[0035] In the claims, as well as in the specification above, all transitional phrases such as "comprising," "including," "carrying," "having," "containing," "involving," "holding," "composed of," and the like are to be understood to be open-ended, i.e., to mean including but not limited to. Only the transitional phrases "consisting of and "consisting essentially of shall be closed or semi-closed transitional phrases, respectively, as set forth in the United States Patent Office Manual of Patent Examining Procedures, Section 21 11.03.

[0036] As used herein in the specification and in the claims, the phrase "at least one," in reference to a list of one or more elements, should be understood to mean at least one element selected from anyone or more of the elements in the list of elements, but not necessarily including at least one of each and every element specifically listed within the list of elements and not excluding any combinations of elements in the list of elements. This definition also allows that elements may optionally be present other than the elements specifically identified within the list of elements to which the phrase "at least one" refers, whether related or unrelated to those elements specifically identified. Thus, as a nonlimiting example, "at least one of A and B" (or, equivalently, "at least one of A or B," or, equivalently "at least one of A and/or B") can refer, in one embodiment, to at least one, optionally including more than one, A, with no B present (and optionally including elements other than B); in another embodiment, to at least one, optionally including more than one, B, with no A present (and optionally including elements other than A); in yet another embodiment, to at least one, optionally including more than one, A, and at least one, optionally including more than one, B (and optionally including other elements); etc.

[0037] It should also be understood that, in certain methods described herein that include more than one step or act, the order of the steps or acts of the method is not necessarily limited to the order in which the steps or acts of the method are recited unless the context indicates otherwise.

[0038] The following description, which illustrates and exemplifies certain aspects and embodiments of the systems and methods described herein, includes reference to the drawings, wherein like reference numerals identify similar structural features or aspects of the subject disclosure.

[0039] With reference to Fig. 1 , in at least one aspect of this disclosure, a combustion system 100 includes a reciprocating engine having at least one cylinder 101. The system 100 further includes a piston 103 in operable communication with the cylinder 101 and configured to sealingly move within the cylinder cavity 107. The cylinder 101 is selectively in fluid communication with an air intake system 108 and a fuel introduction system including a primary fuel reactant (PFR) 1 12 and a secondary fuel reactant (SFR) 1 10. The cylinder cavity 107 is in fluid communication with the atmosphere via an air intake 108a as well as an exhaust manifold 105 such that air with oxygen (0 ₂ ) can be drawn into the cavity 107 through the air intake 108a and exhaust gas can be exhausted through the exhaust manifold 105 into the atmosphere.

[0040] The system 100 also includes a control system 115 having a memory including computer readable instructions stored thereon for starting and/or stabilizing a reactant controlled compression ignition (RCCI) combustion system, the instructions including one or more steps of an embodiment of the method as disclosed hereinbelow.

[0041] In some embodiments, the control system 1 15 can also be connected to a flow sensor 1 17 configured to determine flow rate and/or oxygen content of air being drawn into the cylinder 101. In some embodiments, the control system 1 15 can also be connected to an exhaust sensor 119 configured to sense one or more characteristics (e.g., chemical content, NOx content, unburned reactants) of exhaust gas.

[0042] The control system 1 15 can control any suitable portion of the fuel introduction system (e.g., timing of the air valve 109, the SFR valve 1 11 , and/or the PFR valve 1 13 such as to control the flow rate of air/oxygen, SFR, or PFR into the cavity 107). In some embodiments, the control system 1 15 can determine oxygen content of intake air (e.g., by using readings from sensor 1 17) and modify the input of SFR and PFR to create a stoichiometric mixture to ensure approximately full usage of each reactant.

[0043] In certain embodiments, the SFR can include an oil or oil distillate (e.g., petroleum or pyrolysis oil based), liquefied petroleum gas (LPG) or any other suitable fuel or additive. In certain aspects, the SFR includes an oil, for example, as a transport medium that undergoes pyrolysis to form light hydrocarbons (C1-C8).

[0044] In further embodiments, the PFR can include at least one of diesel fuel, biodiesel, ethanol, gasoline, butane, isooctane, ethyltoluene, MTBE, kerosene, LPG, propane, coal tar, naptha, propane and combinations thereof. The SFR and 0 ₂ mixture can be selected to generate radicals when subject to a compression cycle. The radicals can cause ignition of the PFR upon introduction of the PFR into the cylinder 101.

[0045] The SFR and 0 ₂ mixture can be selected to generate an enhanced combustion environment when subject to a compression cycle. This environment is condusive to the rapid, even and complete combustion of the PFR upon ignition.

[0046] Referring to Figs. 1 -5, in at least one aspect of this disclosure, a method of starting and/or stabilizing a reactant controlled compression ignition (RCCI) combustion system 100 includes determining an amount of intake oxygen (0 ₂ ) flowing into a cylinder 101 of an engine from an intake 108a during an intake stage of the cylinder. The method also includes calculating an amount of primary fuel reactant (PFR) and/or a secondary fuel reactant (SFR) to be injected into the cylinder 101 to achieve a stoichiometric oxygen-to-fuel ratio. Achieving any other suitable ratio of PFR, SFR, and/or air is contemplated herein.

[0047] The method includes introducing the SFR into the cylinder 101 before or during a compression stage (e.g., as shown in Fig. 1) of the cylinder 101 such that the SFR and the 0 ₂ create a compressed mixture after the compression stage (e.g., as shown in Fig. 2). In some embodiments, introducing the SFR can include using engine oil as the transport medium. Introducing the SFR can include introducing a small additive quantity of SFR such that the SFR can be considered an additive instead of a fuel. Typically, additives which are added to the fuel tank have a concentration ratio of 0.1 % by volume. The composition of the diesel fuel can comprise up to 7% addition of bio-diesel (FAME) by volume according to EN590:2009 standard. Both figures refer to the direct dilution of the PFR. For a system as described where the SFR and PFR may be delivered via different methods the dilution occurs in the engine cylinder.

[0048] While the SFR system 1 10 is shown as independent of the air system 108, it is contemplated that the SFR can be combined in the air intake 108a with the air before entering the cylinder 101. Any other suitable configuration for mixing the SFR and the 0 ₂ before or during compression is contemplated herein. In certain embodiments, the method includes creating radicals by compressing the SFR and the 0 ₂ mixture, which allows the PFR to homogeneously combust upon introduction into the cylinder 101. In some embodiments, the SFR and 0 ₂ mixture release energy when subject to a compression cycle, allowing homogeneous combustionof the PFR when it is ignited.

[0049] The method further includes combining the PFR with the compressed mixture (e.g., as shown in Fig. 3). The PFR and the SFR in the compressed mixture are chemically selected and metered to homogenously burn upon ignition (e.g., as shown in Fig. 4). The method can further include allowing the PFR to ignite via compression or chemical reaction with the compressed mixture. In other embodiments, igniting the PFR can be done using a spark plug after the PFR has been introduced.

[0050] Combining the PFR with the compressed mixture of SFR and 0 ₂ can include at least one of injecting the PFR in the intake air, fumigation, or direct injection of the PFR into the cylinder. Any other suitable method if contemplated herein.

[0051] As shown in Fig. 5, the products of combustion can be purged during the exhaust cycle such that there are approximately no residual reactants present in the cylinder for a subsequent compression and combustion reaction. This stabilizes the RCCI combustion system in HCCI mode because the carefully metered quantities of 0 ₂ , SFR, and PFR are not interfered with by any residual reactants that failed to be exhausted since all reactants are converted to products and not capable of reacting again or with this selected chemical mixtures.

[0052] Without being limited by any particular theory, it is believed that the manifestation of the increased linear pressure wave with the RCCI mode of stoichiometric combustion is felt as increased torque at the crank. Moreover, it is believed that combustion in the RCCI mode is so rapid and complete that the crank feels the increased torque very quickly along its teeth. Thus, in certain aspects, the description provides internal combustion systems and methods that utilizes compression ignition in RCCI mode as described herein, which provide rapid and enhanced power across a range of engine demands.

[0053] The method can further include determining an amount of a product of combustion (e.g., using sensor 1 19) in an exhaust gas and modifying the timing and/or amount of at least one of 0 ₂ intake 108, SFR 1 10, PFR 112 or a combination thereof in response thereto to minimize pollution and increase efficiency. This can also be used in a situation where exhaust gas is redirected back into the intake such that a new formulation of SRF and PFR can be used to account for the changing intake air chemistry.

[0054] For a gasoline engine (SI) to operate in RCCI mode forced induction is required which will both increase the cylinder pressure on the compression stroke and also the quantity of 0 ₂ reactant, compared to a normally aspirated engine. CI engines require a high cylinder pressure on the compression stroke in order to achieve auto ignition of the PFR, which is achieved via a high compression ratio and forced induction, normally by the use of a turbo charger. It is the combination of the 0 ₂ and SFR when subject to the compression stroke of the engine that create the combustion environment for homogenious combustion of the PFR when it is ignited. It is likely that this combustion environment is contemporaneous in nature and will decay or react if not utilized constructively by the ignition of the PFR. It is therefore implicit that the creation of the favourable combustion environment occurs on the compression stroke, immediately before the ignition of the PFR all of which occurs around the TDC position. The homogenious combustion of the PFR requires that the reactants, especially the 0 ₂ , are stoichiometrically related. Whilst known schemes such as exhaust gas recirculation (EGR) or a combination of EGR and variable boost pressure are compatible with a RCCI engine they are not as important in reducing emissions as the primary reduction has been achieved via homogenious combustion.

[0055] The methods and systems of the present disclosure, as described above and shown in the drawings, provide for improved combustion engine systems with superior properties including increased efficiency and reduced pollution. While preferred embodiments of the systems and methods have been shown and described herein, it will be understood that such embodiments are provided by way of example only. Numerous variations, changes and substitutions will occur to those skilled in the art without departing from the spirit and scope of the present disclosure. Accordingly, it is intended that the appended claims cover all such variations as fall within the spirit and scope of the disclosure. [0056] Those skilled in the art will recognize, or be able to ascertain using no more than routine experimentation, many equivalents to the specific embodiments described herein. Such equivalents are intended to be encompassed by the following claims. It is understood that the detailed examples and embodiments described herein are given by way of example for illustrative purposes only, and are in no way considered to be limiting to the invention. Various modifications or changes in light thereof will be suggested to persons skilled in the art and are included within the spirit and purview of this application and are considered within the scope of the appended claims. For example, the relative quantities of the ingredients may be varied to optimize the desired effects, additional ingredients may be added, and/or similar ingredients may be substituted for one or more of the ingredients described. Additional advantageous features and functionalities associated with the systems, methods, and processes of the present invention will be apparent from the appended claims. Moreover, those skilled in the art will recognize, or be able to ascertain using no more than routine experimentation, many equivalents to the specific embodiments of the invention described herein. Such equivalents are intended to be encompassed by the following claims.