WO2018007865A1

WO2018007865A1 - Stratified charge combustion engine

Info

Publication number: WO2018007865A1
Application number: PCT/IB2017/000806
Authority: WO
Inventors: Dominique Bosteels
Original assignee: Dominique Bosteels
Priority date: 2016-07-04
Filing date: 2017-07-03
Publication date: 2018-01-11

Abstract

The invention relates to an opposite pistons engine comprising an intermediate open catalytic element located between the pistons moving in a cylinder, said element being provided with a cerium oxide - carbon containing coating, said coating further comprising at least comprising oxides of the followings elements Pr, Nd, La and at least Y and/or Zr. The engine of the invention enables a catalytic reduction of NOx exhaust rate.

Description

Stratified charge combustion engine Abstract of the disclosure

The invention relates to an at least partly stratified (such as at least partly dual stratified) charge combustion engine, especially CAI (combustion assisted ignition), HCC, HCSI and HCCI engine, in which the combustion of a hydrocarbon containing fuel generating a flame emitting photon is operated in a chamber with a wall and/or surfaces provided with a cerium oxide - carbon containing coating, said coating further comprising at least comprising oxides of the followings elements Pr, Nd, La and at least Y and/or Zr. The engine of the invention enables a catalytic reduction of NOx exhaust rate. The prior art

Combustion of fuel can be operated a cold combustion or a hot combustion, by reacting a fuel with oxygen or oxygen containing medium, said reaction comprising oxidation reaction as well as reduction reaction.

Fuel efficiency is nowadays more problematic, due to pollution and health problems generated by said pollution.

Fuel efficiency for engines (such as internal combustion engines, external combustion engines, with or without turbo, EGR, etc., possibly as hybrid engines), especially for on road vehicles (like cars and trucks, as well as bikes), ships, trains, flying apparatuses (like aeroplanes), which were considered by mechanical engineers as substantially complete, is more and more questioned, as assumed efficiency figures are not corresponding to the current figures achieved by the end user, for example for cars and trucks, with moreover higher than foreseen CO and NOx exhaust rates, as well as higher C 02 exhaust rates. The proposed system for improving efficiency comprises for example system enabling direct injection, most particularly controlled continuous or intermittent direct injection, instead of fuel admission through the air intake manifold or through a port fuel tube.

As disclosed in US8347613, direct injection (Dl) engines may produce more soot than port fuel injected engines in part due to diffuse flame propagation. As a consequence of diffuse flame propagation, fuel may not adequately mix with air prior to combustion, resulting in pockets of rich combustion that generate soot. Further, Dl engines may be susceptible to generating soot during high load and/or high speed conditions when there is a lack of sufficient air and fuel mixing.

For solving this soot (particle) problem, it has been proposed to apply particulate filters to Dl, spark-ignition engines or compression ignition engines, leading then the problem of regular filter regeneration steps, during which accurate emission control is difficult to maintain during particulate filter regeneration in a Dl, spark- ignition engine. Such filter reduces however the engine efficiency, as generating clogging and a pressure drop in the exhaust filter. Due to the high volume of small particles and soot, filter is quickly at least partly clogged. Soot will also generate other problems with respect to gas recycling systems (EGR), that will clog too.

The patent US8347613 suggests for solving said problem particle clogging of the filter to generate compressed air and to push said compressed air through the particulate filter, meaning thus that small particles are released back into the atmosphere.

Homogeneous charge combustion has also been proposed for increasing the fuel efficiency. More and more researches have therefor been directed to systems for ensuring CAI, HCC, especially HCCI and HCSI. For example US7290522 (Prof Heywood et al) relates to homogeneous charge compression ignition (HCCI) engine. As stated by Professor Heywood of the MIT, the use of HCCI combustion ensures high engine efficiency with extremely low NOx, CO and particulate emissions.

Professor Heywood teaches the use of hydrogen or hydrogen mixed with CO in order to enhance knock resistance, and thus resistance to auto ignition, i.e. auto ignition generated at higher temperature and pressure.

It means thus well that for expert in the chemistry of the fuel combustion in engine, the efficiency of the combustion can still be improved, with moreover reduced NOx, CO and particles emissions. The admission of Hydrogen possibly mixed with CO in a combustion chamber is not easy and lead to several technical problems, such as the storage of hydrogen.

In order to improve the efficiency of fuel combustion, it has been already proposed by the present inventor to operate the combustion of the fuel in presence of a heterogeneous catalyst comprising some cerium and carbon. For example, reference can be done to WO2006017915, US7482303, US7188470,

EP1590555Bl , and US7723257.

Opposed piston engines existed in the past (such as for marine and submarines), for example sold under the trade name Fairbanks-Morse. However, more and more researches have now been done for further reducing consumption, as well as for other advantages, as explained in the article "Opposed-piston engines: the future of internal combustion engines?", Kalke Jakub et al., PhD Interdisciplinary Journal, pages 175-184, 2014 (sdpg.pg.gda.pl/pij/wp- content/blogs.dir/.. V01_2014J 9-kalke.pdf - created on December 8, 2014). Other article of interest is available via the web : www.mdpi.com/1996- 1073/8/7/6365/pdf; "An experimental investigation on the combustion and heat release characteristics of an opposed-piston folded-cranktrain diesel engine", Fukang Ma et al, Energies 2015, 8 6365-6381

The invention is using a heterogeneous catalytic system comprising rare earth metals. Problems associated to heterogeneous catalytic system are among other limited catalytic life time, variable working efficiency in function of reaction conditions, etc.

The experience and further searches carried out by the inventor have shown that catalyst could be still be improved, for fuel efficiency purposes for a long period of time, as well as for variable working conditions. The new catalyst of the invention enables also an easier control of the working of the engine, while being submitted to variation of load or speed. The system of the invention is thus a dynamic bi functional or hybrid system combining rare earth metal oxides and non rare earth metal oxides, together with carbon particles. The system of the invention uses a catalytic coating having a good thermal resistance, a good catalytic longevity, a good resistance to vibrations, pressure variations. It seems that some metal elements of the catalyst coating are sintered with the metal surface of the combustion chamber (for example of the aluminium alloy of the combustion chamber). It was observed that catalytic efficiency or working was achieved from low temperature (such as temperature of less than 300°C) up to high temperature (such as temperature higher that 700°C, or even higher than 900°C). It was observed that catalyst coatings of the invention were suitable to catalyse redox reactions on and in the porous catalytic coating. It was also observed that due to the catalyst coating of the invention, some flame quenching could be prevented, such as side wall and/or surfaces quenching and/or tube quenching (cylinder quenching). It was also observed that ionisation current was better conserved adjacent to the catalyst coating. Without being bound to any theory, it is expected that the catalyst coating ensures within the free volume of the combustion chamber a thicker intermediate layer between the flame plasma and the catalyst coating of the invention, with respect to a combustion chamber not provided with the catalyst coating. Without being bound to any theory, it is expected that the catalyst coating of the invention ensures a more controlled ionisation level, with reduced chemi ionisation peak and thermal ionisation peak, even in presence of large excess of air, such as with lambda value of more than 1.4, or even 1.5 (such as more than 1.6, more than 1.7 or even more than 2.0). It seems also that the temperature of the face of the wall and/or surfaces of the combustion chamber is less- subject to high variations, despite intake step and exhaust step in particular in a four-cycle engine.-

The control of chemical catalysis is disclosed in US7998538 (California Institute of Technology). As stated in said documents, many catalytic reactions have a temperature threshold. Prior art methods utilise macroscopic heat source to provide heat for such reactions and typically entail gross convection, gross conduction, or gross radiation. Inherent with the use of such conventional methods of heating, is the difficulty of having control of the temperature of a catalyst, the vicinity of the catalyst and/or the heat applied, both temporally and spatially.

In a combustion chamber of current engine, reaction is substantially operated in the volume of the chamber, without heterogeneous catalyst. In the engine of the invention, wall and/or surfaces of the combustion chamber is/are coated with a catalyst coating, the working of said catalyst coating being controlled by photon- electron interactions, said interactions having not only localised effect on the temperature of the coating, but also on the local charging of photon-electron of the coating for controlling local radical reaction on the catalyst coating.

When burning fuel, a large quantity of photon-electron energy is emitted. In the current engine (thus not according to the invention), said photon-electrons are not used for catalytic efficiency purposes. Brief description of the invention

The invention relates to an at least partly stratified charge combustion engine being an opposed-piston engine comprising at least one cylinder in each of which a first piston with a first cross section with a first diameter is moving along a first axis and a second piston with a second cross section with a second diameter equal or different from the first diameter is moving along a second axis parallel to the first axis, whereby said first piston and said second piston are reciprocating along to each other between a first position in which the said first and second pistons are close the one to the other in the cylinder considered, whereby defining in said cylinder considered a small volume between the said first and second pistons, and a second position in which the first and second pistons are away the one with respect to the other so as to define therebetween a second volume in the cylinder considered which is greater than the first volume, whereby each cylinder is provided with a catalytic open element located within the small volume of the cylinder considered, said open element separating the said first volume into a first zone directed towards the first piston and a second zone directed towards the second piston, while defining one or more open channels extending between the first zone and the second zone, said one or more passages defining an open cross section defining an open surface within a plane perpendicular to the first axis and second axis which is comprised between 0.2 and 0.8 times (advantageously 0.3 and 0.7, preferably between 0.4 and 0.6, such as from 0.5 to 0.6) the average cross section of the first and second piston, whereby at least the one or more channels of the catalytic element is provided with a cerium oxide - carbon containing coating, said coating further comprising at least comprising oxides of the fallowings elements Pr, Nd, La and at least Y and/or Zr, whereby said cerium oxide - carbon containing coating with the oxides of the followings elements Pr, Nd, La and at least Y and/or Zr, is adapted for controlling the formation of H+ species on the wall and/or surfaces of the chamber, while controlling the hydrogen branching reactions by catalysing the use of oxygen atoms from Ce, Pr, Nd, La and at least Y and/or Zr oxides for reacting with hydrogen ¾ for the formation of H₂0 on the wall and/or surfaces of the chamber, whereby the weight metal content of the metal element selected from Y, Zr and mix thereof expressed as oxide in the total metal weight content of metal elements selected from Ce, Pr, Nd, La, Y and Zr expressed as oxide is at least 10%, advantageously at least 15%, preferably from 16 to 40%, most preferably from 20 to 30%.

The invention relates also to a power engine comprising a combustion chamber in which a fuel is bum for generating gases for moving a driving element, especially an engine as disclosed here above with opposed pistons, whereby the combustion chamber comprises at least one element selected from the group consisting of a fuel injector, a water vapour injector, a spark plug, a sensor comprising at least a core provided with a cerium oxide - carbon containing coating, said coating of the element further comprising at least comprising oxides of the followings elements Pr, Nd, La and at least Y and/or Zr, whereby said cerium oxide - carbon containing coating with the oxides of the followings elements Pr, Nd, La and at least Y and/or Zr, is adapted for controlling the formation of H+ species on the wall and/or surfaces of the chamber, while controlling the hydrogen branching reactions by catalysing the use of oxygen atoms from Ce, Pr, Nd, La and at least Y and/or Zr oxides for reacting with hydrogen H₂ for the formation of H₂0 on the wall and/or surfaces of the chamber, whereby the weight metal content of the metal element selected from Y, Zr and mix thereof expressed as oxide in the total metal weight content of metal elements selected from Ce, Pr, Nd, La, Y and Zr expressed as oxide is at least 10%, advantageously at least 15%, preferably from 16 to 40%, most preferably from 20 to 30%.

Advantageously, the cerium - carbon coating of the catalytic element or core is adapted for capturing photons emitted by the flame with wavelength from 6500 to 7500A, advantageously for capturing 5 to 25% of the photons with wavelength from 6500 to 7500A emitted by the flame having a temperature higher than 800°C. Preferably, the cerium - carbon coating of the catalytic element or core is adapted for ensuring a photon amplified spectrum emission radiation at least at a temperature comprised between 500 and 800°C, said spectrum covering advantageously substantially the whole range from about 4000A up to 7500A.

Most preferably, the element has a plurality of distinct channels with a m imum open cross section of at least 0.5cm², advantageously at least 1cm². According to a preferred embodiment, the element or core is made at least partly in a temperature ceramic like material, advantageously comprising aluminium.

The engine of the invention is advantageously an engine, which comprises a plurality of cylinders and a central axis provided with two wobble plates, a first series of pistons being turned to a first wobble plate and connected to said first wobble plate by means of a first series of rods, while a second series of pistons are turned to the second wobble plate and are connected to said second wobble plate by means of a second series of rods. According to an embodiment, the engine is an invention, which cycles comprise each at least four successive steps, namely an intake step for charging the combustion chamber with at least oxygen and nitrogen, a compression step in which said at least oxygen and nitrogen is compressed, a combustion step in the combustion chamber, and an exhaust step for the exhaust of gases present in the combustion chamber, whereby at least during one step selected from the group of the intake step and compression step, the cerium oxide - carbon coating of the element comprising oxides of the followings elements Pr, Nd, La and at least Y and/or Zr, is adapted for uptake of oxygen atoms at temperature comprised between 100 and 400°C. Advantageously, each cylinder is associated to at least one injector for the admission of a combustible material within the cylinder, adjacent to the catalytic element or at the level of the catalytic element, and/or to at least one injector for the admission of water vapour within the cylinder, adjacent to the catalytic element or at the level of the catalytic element.

The inner wall and/or surfaces of the cylinder or combustion chamber is/are advantageously provided with a cerium oxide - carbon containing coating, said cerium oxide - carbon containing coating further comprising at least comprising oxides of the followings elements Pr, Nd, La and at least Y and/or Zr, whereby said cerium oxide - carbon containing coating with the oxides of the followings elements Pr, Nd, La and at least Y and/or Zr, is adapted for controlling the formation of H+ or [Η^'] species on the cerium oxide - carbon containing coating of the chamber, while controlling the hydrogen branching reactions by catalysing the use of oxygen atoms from Ce, Pr, Nd, La and at least Y and/or Zr oxides for reacting with hydrogen H₂ for the formation of H₂0 on the wall and/or surfaces of the chamber, whereby the weight metal content of the metal element selected from Y, Zr and mix thereof expressed as oxide in the total metal weight content of metal elements selected from Ce, Pr, Nd, La, Y and Zr expressed as oxide is at least 10%, advantageously at least 15%, preferably from 16 to 40%, most preferably from 20 to 30%.

The cerium oxide - carbon containing coating of said inner wall and/or surfaces and/or of the catalytic el ement and/or core has advantageously a thickness of less than ΙΟΟμιη, such as less than 70μηι, for example a thickness from 10 to 70μπι.

Carbon containing coating in the present invention means a coating comprising graphite carbon (also known as graphitic carbon or carbon lattices), most preferably like as 2dimensional-graphene structures (such as structures with a larger Raman intensity peak between 2600 - 2700 Raman shift (1/cm) than the Raman peak intensity between 1500 - 1700 Raman shift (1/cm). The carbon containing coating of the invention is preferably a coating for which at least 30% by weight of the carbon is in a form of 2dimensional-graphene structure, advantageously mixed with graphite having the structure of nanotubes (such as single wall and/or surfaces carbon nano tubes, double wall and/or surfaces carbon nano tubes or multi wall and/or surfaces carbon nano tubes) and/or fullerene and/or combinations thereof.

The catalytic coating disclosed for the combustion chamber of the engine of the invention can also be used for other purposes, such as for the post treatment of exhaust gases (such as NOx reducing post treatment), especially exhaust gases containing fuel and/or carbon containing particles. The catalyst coating is then advantageously supported on an aluminium containing support, an alumino silicate support and/or alumino phospho-silicate support, like a cordierite-like support.

Advantageously, the cerium - carbon coating of said inner wall and/or surfaces and/or of the catalytic element or core is adapted for capturing photons emitted by the flame with wavelength from 6500 to 7500A, advantageously for capturing 5 to 25% of the photons with wavelength from 6500 to 7500A emitted by the flame haying a temperature higher than 800°C.

According to an advantageous embodiment, the cerium - carbon coating of said inner wall and/or surfaces and/or of the catalytic element or core is adapted for ensuring a photon amplified spectrum emission radiation at least at a temperature comprised between 500 and 800°C, said spectrum covering advantageously substantially the whole range from about 4000A up to 7500A (i.e. ensuring thus emission of rays in the violet range (wave length from 4000 A up to about 4500 A), in the blue range ( wave length from 4500 A up to 5200 A), in the green range (from about 5200A up to about 5700A), in the yellow range (from about 5700A up to about 5900A), in the orange range (from about 5900 A up to 6250 A) and in the red range (from about 6250A up to about 7500A). The emission is advantageously controlled so that emission from the coating occurs substantially continuously from about 300°C up to about 900°C.

According to a further embodiment, the cerium oxide - carbon coating of said . inner wall and/or surfaces and/or of the catalytic element or core comprising oxides of the followings elements Pr, Nd, La and at least Y and/or Zr, is adapted for uptake of hydrogen atoms (especially in the form of hydrogen species H') at least at temperature comprised between 300 and 700°C. It is expected that some cracking of the fuel is operated at temperature below 500°C and at pressure higher than 5 10⁵ Pa.

According to an embodiment, the presence of Pr, Nd, La and at least Y and/or Zr, oxides in the cerium oxide - carbon containing coating of said inner wall and/or surfaces and/or of the catalytic element acts advantageously as catalyst for the reaction of oxygen stored in the coating with hydrogen H₂ and/or hydrogen species for the formation of water (as steam or superheated steam) at least at temperature above 500°C and pressure higher than 30 10⁵Pa. Advantageous embodiments of the invention comprise one or more of the following characteristics, advantageously a plurality of the following

characteristics :

- the cerium - carbon containing coating of said inner wall and/or surfaces and/or of the catalytic element or core is appropriate so that the hydrocarbon containing fuel is converted into carbon containing species or molecules and into hydrogen and hydrogen species, at least at temperature above 500°C and pressure above 20 10⁵ Pa.

- the cerium oxide - carbon containing coating of said inner wall and/or surfaces and/or of the catalytic element comprises enough oxides of Pr, La, Nd and at least Y and/or Zr, so as to reduce at least by 50 mole % that hydrogen H₂ molecules contacting the cerium - carbon containing coating are converted into free H species and free OH species, at temperature above 500°C and pressure above 20 10⁵ Pa.

- the cerium oxide - carbon containing coating comprises enough oxides of Pr, La, Nd and at least Y and/or Zr, so as to reduce at least by 75 mole % that hydrogen ¾ molecules contacting the cerium - carbon containing coating is converted into free H species and free OH species, at temperature above 500°C and pressure above 20 10⁵Pa.

- the cerium - carbon containing coating of said inner wall and/or surfaces and/or of the catalytic element or core is adapted, after capturing photon emitted by the flame generated by the combustion of the carbon containing fuel, for generating at least adjacent to the cerium - carbon containing coating, spectra covering substantially continuously the whole range of spectra from about 4000 A up to about 7500 A.

- the cerium - carbon containing coating of said inner wall and/or surfaces and/or of the catalytic element is adapted for capturing photon emitted by the flame generated by the combustion of the carbon containing fuel, and/or,

advantageously and, for generating at least adjacent to the cerium - carbon containing coating, spectra covering substantially continuously the whole range of spectra from about 4000 A up to about 7500 A.

- the cerium - carbon contaimng coating of said inner wall and/or surfaces and/or of the catalytic element or core is adapted for controlling the number of photons in the combustion chamber during at least the combustion of the carbon containing fuel, said photons being advantageously a mix of photons covering the whole range spectra from about 4000 A up to about 7500 A.

- the cerium - carbon containing coating of said inner wall and/or surfaces and/or of the catalytic element or core comprises at least Y and Zr, advantageously the weight ratio Y/Zr present in the catalyst coating is comprised between 1 : 10 and 10: 1 , preferably between 2: 10 and 10:2.

- the cerium - carbon containing coating of said inner wall and/or surfaces and/or of the catalytic element or core comprises some aluminium, preferably in its oxide or hydroxide form and/or in the form of alumino-silicate, whereby the aluminium metal content of the catalyst coating of said inner wall and/or surfaces and/or of the catalytic element with respect to the total metal weight content of the catalyst coating of metal selected from Al, Ce, Pr, Nd, La and at least Y and/or Zr is comprised between 1 and 10%.

- the engine comprises cylinders having an alumino containing face, especially an alumino-silica containing face, said face being at least partly provided with the cerium- carbon containing coating.

- the relative weight of the metals selected from Ce, Pr, La, Nd, Y and Zr (metal elements which can be present in the coating as oxides and/or hydroxides), expressed as the following respective oxides Ce0₂, Pr₆On, La₂0₃, Nd₂0₃, Y₂0₃. and Zr0₂ of the cerium - carbon containing coating of said inner wall and/or surfaces and/or of the catalytic element with respect to total weight of the said metals expressed as oxides are :

Ce (as Ce0₂) : 25 to 50%, preferably from 35 to 45%,

Pr (as Pr₆O_n) : 2 to 10%, preferably from 2.5 to 6%

La (as La₂0₃) : 15 to 37%, preferably from 20 to 32%

Nd (as Nd₂0₃) : 4 to 15%, preferably from 5 to 13%

Y (as Y₂0₃) : 5 to 15%, preferably from 8 to 12%

Zr (as Zr0₂) : 5 to 25%, preferably from 10 to 17%

- the catalyst coating of said inner wall and/or surfaces and/or of the catalytic element or core further comprises aluminium oxide and/or alurninosilicate.

- The catalyst coating of said inner wall and/or surfaces and/or of the catalytic element or core has a thickness of less than 500nm, advantageously less than 300nm.

- the catalyst coating has the structure of largest particles with a size greater than lOOnm, with particles with a size of less than 70nm (preferably less than 30nm) extending within the void created between the largest particles.

- the cerium oxide - carbon containing catalyst of said inner wall and/or surfaces and/or of the catalytic element or core is a catalyst controlling at least the branching reaction of H^' species with 0₂ on the said catalyst, as well as for controlling the branching reaction of '0' species with ¾ on the said catalyst.

- the catalyst coating of said inner wall and/or surfaces and/or of the catalytic element or core is substantially free or free of Pd, Pt, Rh, Cu and combinations thereof.

- at least 50% of the carbon present in the cerium oxide - carbon containing coating is the form of graphene units, possibly with some overlapping portions.

- the cerium oxide - carbon containing catalyst of said inner wall and/or surfaces and/or of the catalytic element or core is adapted for controlling the formation of carbon particles in the form of porous graphite, especially in the form of graphene particles, within the combustion chamber, especially on the catalyst coating, and/or for reducing the exhaust of soot particles from the combustion chamber.

- the cerium oxide - carbon containing catalyst is adapted for emitting in function of the temperature rays with wave lengths in the violet range, rays in the blue range, rays in the green range, rays in the yellow range, as well as rays within the red range.

- the cerium oxide - carbon containing catalyst of said inner wall and/or surfaces and/or of the catalytic element or core is adapted for controlling the formation of carbon particles in the form of porous graphite, especially in the form of graphene particles, within the combustion chamber, especially on the cerium oxide - carbon containing coating, and/or for reducing the exhaust of soot particles from the combustion chamber.

- the cerium oxide - carbon containing catalyst is adapted for emitting in function of the temperature rays with wave lengths in the violet range, rays with wavelengths in the blue range, rays with wave lengths in the green range, rays with wave lengths in the yellow range, as well as rays with wave lengths in the red range.

- the engine is an at least partly dual stratified charge combustion engine, having advantageously two opposite surfaces provided with the cerium oxide - carbon containing catalyst, said opposite surfaces being preferably piston head surfaces or surfaces of two opposite moving piston heads. - combinations thereof.

Brief Description of the drawing

Figures 1 A and IB is a schematic view of one cylinder of a piston-opposite engine with the piston in a close position or in an away position.

Figure 2 is an enlarged view of the catalytic element present in the cylinder, and Figure 3 is a schematic perspective view of a wobble plate connected to a series of pistons, said wobble plate being mounted on one end of the plurality of cylinders.

Description of preferred embodiments

The present invention is an improvement of the technology disclosed in

WO2006017915, US7482303, US7188470, EP1590555B 1 , and US7723257, the content of which is incorporated herein by reference.

Homogeneous charge combustion is according to the state of the art, the way to increase fuel efficiency of the car engine. Car companies have then developed several systems with computer control. However, all said systems have shown their limits, as unable to achieve correctly the goals of consumption, particle emission, etc. at all loads and rpm full ranges.

The invention has for subject matter a piston opposite engine provided with a heterogeneous catalyst enabling a live control of the combustion, even in case of large regime variation.

The combustion chamber of the engine associated with two reciprocating pistons is provided with an intermediary catalytic open element coated with a catalyst or a catalyst precursor. Possibly, the inner wall and/or surfaces of the cylinder is also provided with a catalytic coating or catalyst precursor. Figure 1A or IB shows a cylinder 1 of a piston opposite engine (comprising a plurality of cylinders mounted parallel to each other). Each cylinder 1 is associated to a first piston 2 with a first cross section with a first diameter is moving along a first axis A and a second piston 3 with a second cross section with a second diameter equal or different from the first diameter moving along a second axis parallel to the first axis (in this case corresponding to the axis A), whereby said first piston 2 and said second piston 3 are reciprocating along to each other between a first position (Fig 1 A) in which the said first and second pistons 2,3 are close the one to the other in the cylinder considered 1 , whereby defining in said cylinder considered a small volume between the said first and second pistons 2,3, and a second position (Fig IB) in which the first and second pistons are away the one with respect to the other so as to define therebetween a second volume in the cylinder considered which is greater than the first volume, whereby each cylinder is provided with a catalytic open element 4 located within the small volume of the cylinder considered, said open element 4 separating the said first volume into a first zone 5 directed towards the first piston 2 and a second zone 6 directed towards the second piston 3, while defining one or more open channels 7 extending between the first zone 5 and the second zone 6, said one or more passages 7 defining an open cross section defining an open surface within a plane perpendicular to the first axis and second axis which is comprised between 0.2 and 0.8 times (advantageously 0.3 and 0.7, preferably between 0.4 and 0.6, such as from 0.5 to 0.6) the average cross section of the first and second piston, whereby at least the one or more channels of the catalytic element is provided with a cerium oxide - carbon containing coating 8. -

The catalytic element is provided with a injector 10 for fuel injection, and another 1 1 for water vapour injection. The combustion chamber comprises one or more fuel injectors 100, a water vapour injectors 101 , spark plugs 102, and sensors 103, each comprising at least a core provided with a cerium oxide - carbon containing coating, said coating of the element further comprising at least comprising oxides of the followings elements Pr, Nd, La and at least Y and/or Zr, whereby said cerium oxide - carbon containing coating with the oxides of the followings elements Pr, Nd, La and at least Y and/or Zr, is adapted for controlling the formation of H+ species on the wall and/or surfaces of the chamber, while controlling the hydrogen branching reactions by catalysing the use of oxygen atoms from Ce, Pr, Nd, La and at least Y and/or Zr oxides for reacting with hydrogen ¾ for the forrnation of H₂0 on the wall and/or surfaces of the chamber, whereby the weight metal content of the metal element selected from Y, Zr and mix thereof expressed as oxide in the total metal weight content of metal elements selected from Ce, Pr, Nd, La, Y and Zr expressed as oxide is at least 10%, advantageously at least 15%, preferably from 16 to 40%, most preferably from 20 to 30%.

The catalytic element or core is for example a support (alumino silicate, alumina silico phosphate, ceramic, etc.) provided with a catalyst coating or a precursor coating suitable for generating a catalyst coating. The precursor used was a mix of nano scale particles possibly dispersed in a wax or liquid, the composition of said mix being:

1. nano carbon primary particles with a size of less than 10 nm (possibly agglomerated into a structure with a size of less than 500nm. Said nano carbon primary particles are present in the precursor mix at a rate of 10 to 50% by weight, advantageously from 15 to 30% by weight, preferably about 20% by weight.

Instead of using carbon nano particles as such, a wax possibly with carbon nano particles can be used. The carbon particles are preferably comprising some particles forming a two dimensional graphene structure, most particularly a mono layered two

dimensional graphene structure. 2. a mix of metal oxide particles, especially of nanoparticles (particles with a size of less than 200nm, preferably at least partly less than 50nm. Said mix of metal particles comprises advantageously with respect to the total mix of said metal oxide particles (as weight %) :

Ce (as Ce0₂) : 25 to 50%, preferably from 35 to 45%,

Pr (as Pr On) : 2 to 10%, preferably from 2.5 to 6%

La (as La₂0₃) : 15 to 37%, preferably from 20 to 32%

Nd (as Nd₂0₃) : 4 to 15%, preferably from 5 to 13%

Y (as Y₂0₃) : 5 to 15%, preferably from 8 to 12%

Zr (as Zr0₂) : 5 to 25%, preferably from 10 to 17%

Al (as A1₂0₃) : 0 to 10%, preferably from 1 % to 5%

Si (as Si02) : 0 to 10%, preferably from 0.5 to 5% (Said silicon can be in the form of liquid or soluble tetra ethoxy silane, in a solvent system, such as methanol, ethanol, etc.) The mix of nano oxide particles is advantageously a mix of nano oxide particles with a weight average size of more than 100 ran and of nano oxide particles with a weight average size of less than 70 ran, the weight ratio nano oxide particle with a weight average size greater than lOOnm / nano particles with a weight average size lower than 70nm being comprised between 5: 1 and 1 :5, advantageously between 4: 1 and 2: 1.

3. possibly a wax or liquid system, for enabling some adhesion of the particles on the surface to be coated, said wax or liquid being preferably molecules comprising carbon and hydrogen, as well as preferably oxygen atoms. the weight ratio wax / mix of metal oxide particles is advantageously greater than 2, such as comprised from 2.5 up to 6. The precursor was used for coating (for example by brushing, blowing, spraying, etc.) the wall and/or surfaces of the combustion chambers and piston heads of the engine. The engine was made in an aluminium-based alloy. After said coating, the engine was driven with a fuel for 30 minutes. After said driving of the engine, the excess of catalyst was removed.

The catalyst coating had a thickness of less than about 70nm, with metal particles homogeneously dispersed. On the tube face of the combustion cylinders, substantially no catalyst was present or catalyst with a very small thickness.

The engine of the invention will have the advantages disclosed in the article : "Opposed-piston engines: the future of internal combustion engines?", Kalke Jakub et al. The engine will moreover have the following advantages:

- high thermal stability of the catalyst

- high pressure stability

- high hydrogen stability

- working of the engine possible with different cetane number or octane number

- high ionic conductivity of the coating

- possible ignition control at different compression ratio from 6 up to more than 15, such as 20 or more, for example 22;

- possibility to burn at least partly the carbon and the hydrogen from the fuel separately, namely a large portion of the fuel carbon in the volume of the chamber (comprising the plasma zone adjacent to the catalyst coating(s), i.e. in a N2 enriched environment with respect to air ), and a large portion of the fuel hydrogen on or in the catalyst coating(s) (i.e. namely in a 02 rich environment or in a reduced N2 environment with respect to air)

- High oxygen storage capacity, with high uptake and release oxygen rate

High hydrogen storage capacity - Possible down sizing of the filter, due to less small particle emissions, as well as down sizing of the three way catalyst exhaust

- Possibility to use a filter with large pore size

- Possibility to reduce pressure drop in the exhaust, at the level of the filter, as well as at the level of the three way catalyst

- quicker activation of the three way catalyst

- stable working of the catalyst during time, whereby less catalyst rejuvenation is needed

- possible working of the engine with lambda value higher than 1.3, such as higher than 1.4, such as from 1.4 to 1.3, such as from 1.5 to 2.1.

- improved post treatment

- less NOx

low HC content in the exhaust gases

high steam, superheated steam formation

- less carbon particles exhaust (especially substantially no small sized carbon particles exhaust, such as substantially no carbon particle with a size of less than 5μη )

no soot formation in the combustion chamber

no soot deposit in the exhaust pipe

- high water vapour exhaust.

Lower fuel consumption

Higher global amount of free electrons in the combustion chamber

The combustion was a dual stratified combustion with two opposite surfaces provided with a cerium - carbon containing coating.

- The catalyst coating will reacts differently in function of the oxygen content present within the combustion chamber, thus during the intake and

compression phases (oxygen rich atmosphere), and during the combustion and exhaust phases (oxygen poor or depleted atmosphere). The engine was working with a fuel direct injection system, as well as preferably with a liquid water (as micro droplets) direct injection into the combustion chamber, such system are for example systems like the K-Jetronic fuel range of systems of Bosch GmbH and Wl (Water Injection) of Bosch GmbH. Water injection technologies are disclosed in US5174247, US6067964 and US6092514. The following results were observed: lower fuel consumption, lower NOx emission, lower small carbon particles emission, better , improved working of the engine (less vibrations), better working of the filter and exhaust treatment system, etc.

The engine was an engine with compression ignition. It was observed that it was possible to increase the compression ratio before ignition in a spark ignition engine as well as for compression ignition engine, with respect to currently used ignition compression ratio. Moreover, possible ignition was possible with a spark plug within a large range of compression ratio.

As the pressure drop in the exhaust converter system and filter was reduced with respect to the pressure drop in the exhaust converter system and filter of the current engines, while ensuring a high level of removal of carbon particles and /or conversion of toxic NOx molecules, a better air filling of the combustion chamber was possible with the engine of the invention. Moreover when the air intake system (inlet canals or intake ports) and the exhaust valve are both in open position, air can more easily flow through the combustion chamber of the engine of the invention, ensuring in this way an oxygen uptake by the catalyst coating, as well as a cooling of the combustion chamber, and even a high scavenging of exhaust gases.

In view of the lower pressure drop in the exhaust converter system, exhaust gases can be better used for driving into rotation of a turbine (for which ever purposes), when required and/or for EGR (exhaust gas recycling) purposes. Due to the low level of carbon particles content, EGR is better performing and the EGR system is not subject to clogging problems The engine could also be an engine with spark ignition or with other means for controlling the ignition. The engine can also be provide with Bosch like injectors for injecting water drops or droplets and/or water vapour in the air intake (before and/or after the air butterfly valve in the manifold , and/or directly within the combustion chamber).

The catalyst coating of the invention can thus be considered as being a highly coordinated selective, oxidising and reducing self supported redox catalytic system, whereby selective oxidising and selective reducing can vary or be controlled in function of temperature and photon emission.

The opposite pistons engine can also be of the type not using wobble plates for transmitting the power generated by the fuel combustion and the displacement of the pistons to a driving axis. The opposite pistons engine can also be of the type "fairbanks-Morse" diesel engine.

Figure 3 shows in perspective a wobble plate 20 connected by means rods 21 (with spherical head enabling a rotation of the head within a recess of a arm of the wobble plate) to five pistons (2 or 3)moving in distinct cylinders 1 , the said wobble plate being located at one end of said cylinders 1. Another wobble plate is connected similarly to the other pistons moving in the cylinders 1. The two wobble plates (also known as swash-plates) are linked the one to the other by a central axis 24 which is driven into rotation by the movement of the wobble plate. Wobble plates opposite pistons engines are for example of the type : Lamplough axial engine (see www.douglas-self.com; US 1765167); Wishon (U S 1476275), Sterling axial engine (US2080846), etc.

Claims

What I claim is :

1. An at least partly stratified charge combustion engine being an opposed-piston engine comprising at least one cylinder in each of which a first piston with a first cross section with a first diameter is moving along a first axis and a second piston with a second cross section with a second diameter equal or different from the first diameter is moving along a second axis parallel to or corresponding to the first axis, whereby said first piston and said second piston are reciprocating along to each other between a first position in which the said first and second pistons are close the one to the other in the cylinder considered, whereby defining in said cylinder considered a small volume between the said first and second pistons, and a second position in which the first and second pistons are away the one with respect to the other so as to define therebetween a second volume in the cylinder considered which is greater than the first volume, whereby each cylinder is provided with a catalytic open element located within the small volume of the cylinder considered, said open element separating the said first volume into a first zone directed towards the first piston and a second zone directed towards the second piston, while defining one or more open channels extending between the first zone and the second zone, said one or more passages defining an open cross section defining an open surface within a plane perpendicular to the first axis and second axis which is comprised between 0.2 and 0.8 times the average cross section of the first and second piston, whereby at least the one or more channels of the catalytic element is provided with a cerium oxide - carbon containing coating, said coating of the element further comprising at least comprising oxides of the followings elements Pr, Nd, La and at least Y and/or Zr, whereby said cerium oxide - carbon containing coating with the oxides of the followings elements Pr, Nd, La and at least Y and/or Zr, is adapted for controlling the formation of H+ species on the wall and/or surfaces of the chamber, while controlling the hydrogen branching reactions by catalysing the use of oxygen atoms from Ce, Pr, Nd, La and at least Y and/or Zr oxides for reacting with hydrogen H₂ for the formation of ¾0 on the wall and/or surfaces of the chamber, whereby the weight metal content of the metal element selected from Y, Zr and mix thereof expressed as oxide in the total metal weight content of metal elements selected from Ce, Pr, Nd, La, Y and Zr expressed as oxide is at least 10%, advantageously at least 15%, preferably from 16 to 40%, most preferably from 20 to 30%.

2. The engine of claim 1 , in which the cerium - carbon coating of the element is adapted for capturing photons emitted by the flame with wavelength from 6500 to 7500A, advantageously for capturing 5 to 25% of the photons with wavelength from 6500 to 7500A emitted by the flame having a temperature higher than 800°C.

3. The engine of claim 1 or 2, in which the cerium - carbon coating of the element is adapted for ensuring a photon amplified spectrum emission radiation at least at a temperature comprised between 500 and 800°C, said spectrum covering advantageously substantially the whole range from about 4000A up to 7500A.

4. The engine of any one of the preceding claims, in which the element has a plurality of distinct channels with a minimum open cross section of at least 0.5cm², advantageously at least 1cm².

5. The engine of any one of the preceding claims, in which the element is made at least partly in a temperature ceramic like material, advantageously comprising aluminium.

6. The engine of any one of the preceding claims, which comprises a plurality of cylinders and a central axis provided with two wobble plates, a first series of pistons being turned to a first wobble plate and connected to said first wobble plate by means of a first series of rods, while a second series of pistons are turned to the second wobble plate and are connected to said second wobble plate by means of a second series of rods.

7. The engine of any one of the preceding claims, which cycles comprise each at least four successive steps, namely an intake step for charging the combustion chamber with at least oxygen and nitrogen, a compression step in which said at least oxygen and nitrogen is compressed, a combustion step in the combustion chamber, and an exhaust step for the exhaust of gases present in the combustion chamber, whereby at least during one step selected from the group of the intake step and compression step, the cerium oxide - carbon coating comprising oxides of the followings elements Pr, Nd, La and at least Y and/or Zr, is adapted for uptake of oxygen atoms at temperature comprised between 100 and 400°C.

8. The engine of the preceding claim, in which each cylinder is associated to at least one injector for the admission of a combustible material within the cylinder, adjacent to the catalytic element or at the level of the catalytic element.

9. The engine of the preceding claim, in which each cylinder is associated to at least one injector for the admission of water vapour within the cylinder, adjacent to the catalytic element or at the level of the catalytic element.

10. The engine of any one of the preceding claims, in which the hydrocarbon containing fuel is converted into carbon containing species or molecules and into hydrogen and hydrogen species, at least at temperature above 500°C and pressure above 20 10⁵ Pa.

1 1. The engine of any one of the previous claims, in which the cylinder has advantageously an inner wall and/or surfaces provided with a cerium-carbon containing coating further comprising at least comprising oxides of the followings elements Pr, Nd, La and at least Y and/or Zr, whereby the cerium - carbon containing coating of said inner wall and/or surfaces of the cylinder and/or of the catalytic element is adapted for controlling the number of photons in the combustion chamber, especially adjacent to the catalytic element, during at least the combustion of the carbon containing fuel, said photons being advantageously a mix of photons covering the whole range spectra from about 4000 A up to about 7500 A.

12. The engine of anyone of the preceding claims, in which the cerium - carbon containing coating of said inner wall and/or surfaces and/or of the catalytic element comprises at least Y and Zr, advantageously the weight ratio Y/Zr expressed as oxides present in the catalyst coating is comprised between 1 : 10 and 10: 1 , preferably between 2: 10 and 10:2.

13. The engine of anyone of the preceding claims, in which the cerium - carbon containing coating of said inner wall and/or surfaces and/or of the catalytic element comprises some aluminium, preferably in its oxide or hydroxide form and/or in the form of aluminosilicate, whereby the aluminium metal content of the catalyst coating with respect to the total metal weight content of the catalyst coating of metal selected from Al, Ce, Pr, Nd, La and at least Y and/or Zr is comprised between 1 and 10%.

14. The engine of anyone the preceding claim, in which the engine comprises cylinders having an alumino containing face, especially an alumino-silica containing face, said face being at least partly provided with a cerium - carbon containing coating.

15. The engine of the preceding claim, in which the relative weight of the metals selected from Ce, Pr, La, Nd, Y and Zr, expressed respectively as the following oxides Ce0₂, Pr₆Ou, La₂0₃, Nd₂0₃, Y₂0₃. and Zr0₂ of the cerium - carbon containing coating of said inner wall and/or surfaces and/or of the catalytic element with respect to total weight of the said metals expressed as oxides are : Ce (as Ce0₂) : 25 to 50%, preferably from 35 to 45%,

Pr (as Pr₆On) : 2 to 10%, preferably from 2.5 to 6% La (as L¾0₃) : 15 to 37%, preferably from 20 to 32%

Nd (as Nd₂0₃) : 4 to 15%, preferably from 5 to 13%

Y (as Y₂0₃) : 5 to 15%, preferably from 8 to 12%

Zr (as Zr0₂) : 5 to 25%, preferably from 10 to 17%

16. A power engine comprising a combustion chamber in which a fuel is burn for generating gases for moving a driving element, especially an engine according to any one of the preceding claims, whereby the combustion chamber comprises at least one element selected from the group consisting of a fuel injector, a water vapour injector, a spark plug, a sensor comprising at least a core provided with a cerium oxide - carbon containing coating, said coating of the element further comprising at least comprising oxides of the followings elements Pr, Nd, La and at least Y and/or Zr, whereby said cerium oxide - carbon containing coating with the oxides of the followings elements Pr, Nd, La and at least Y and/or Zr, is adapted for controlling the formation of H+ species on the wall and/or surfaces of the chamber, while controlling the hydrogen branching reactions by catalysing the use of oxygen atoms from Ce, Pr, Nd, La and at least Y and/or Zr oxides for reacting with hydrogen H₂ for the formation of H₂0 on the wall and/or surfaces of the chamber, whereby the weight metal content of the metal element selected from Y, Zr and mix thereof expressed as oxide in the total metal weight content of metal elements selected from Ce, Pr, Nd, La, Y and Zr expressed as oxide is at least 10%, advantageously at least 15%, preferably from 16 to 40%, most preferably from 20 to 30%.

17. The engine of claim 16, in which the relative weight of the metals selected from Ce, Pr, La, Nd, Y and Zr, expressed respectively as the following oxides Ce0₂, ΡΓ6<3Ι Ι, La₂0₃, Nd₂0₃, Y₂0₃. and Zr0₂ of the cerium - carbon containing coating of said core with respect to total weight of the said metals expressed as oxides are : Ce (as Ce0₂) : 25 to 50%, preferably from 35 to 45%, Pr (as Pr₆O_n) : 2 to 10%, preferably from 2.5 to 6% La (as La₂0₃) : 15 to 37%, preferably from 20 to 32% Nd (as Nd₂0₃) : 4 to 15%, preferably from 5 to 13% Y (as Y₂0₃) : 5 to 15%, preferably from 8 to 12% Zr (as Zr0₂) : 5 to 25%, preferably from 10 to 17%