WO2018069360A1

WO2018069360A1 - A combustion engine

Info

Publication number: WO2018069360A1
Application number: PCT/EP2017/075873
Authority: WO
Inventors: Nigel WILLIAMSON
Original assignee: Clean Power Hydrogen Group Limited
Priority date: 2016-10-13
Filing date: 2017-10-10
Publication date: 2018-04-19
Also published as: GB201617383D0

Abstract

A combustion engine of the type comprising a combustion chamber and an air intake configured to deliver air to the combustion chamber during operation is described. The engine comprises an aqueous mist generating module operably connected to the air intake and configured to generate an aqueous mist and induce the aqueous mist into air in the air intake, whereby a mixture of air and aqueous mist is delivered to the combustion chamber separate from the fuel. Combustion of the fuel and the air/mist mixture reduces the level of NOx emissions and increases the power generated by the engine. Induction of the mist into an air supply that is separate from the fuel supply avoids the need for specialised carburation or flash-back inhibition technology or an aqueous mist generating module configured for retro-fitting to a combustion engine is also disclosed.

Description

TITLE

A combustion engine Field of the Invention

The present invention relates to a combustion engine. Also contemplated are retro-fit attachments for combustion engines and methods of reducing emissions from combustion engines.

Background to the Invention

Internal combustion engines generally draw ambient air into a combustion chamber where the air and a fuel are compressed by a compression device, such as a piston in a cylinder for example, and ignited to cause combustion of the air-fuel mixture. The combustion gases generally expand to do work on the compression device, such as moving the piston to drive a crankshaft. The combustion gases are typically then expelled from the combustion chamber through an exhaust of the engine. Combustion of the fuel in the engine, such as diesel, gasoline, ethanol, Natural gas, LPG or hydrogen, typically results in incomplete combustion of the fuel. Incomplete combustion of hydrocarbon-based fuels can result in increased polluting emissions being released from the exhaust, such as hydrocarbon in gaseous form and particulate matter (e.g. soot) and carbon monoxide. Additionally, levels of NOx emissions typically increase with higher combustion chamber temperatures, and higher combustion chamber temperatures can also lead to increased wear on other components of the engine.

NOx, or oxides of nitrogen (NO, N02, etc.) emissions, are a family of poisonous and highly reactive gasses that form when fuel is burned with air at high temperatures, such as in engines of road and non-road vehicles and industrial engines found in power plants. With governments throughout the developed world attempting to address greenhouse gas generation (NOx is a strong contributor to global warming) and public health concerns associated with the NOx generated by motor vehicles, there is a concerted effort to reduce or even eliminate these compounds from exhaust emissions. Various technologies have been developed in an attempt to address this issue. Most of these involve post-combustion treatment of the exhaust gases, which react hydrogen- bearing compounds such as urea (AdBlue) with the exiting gases. Another approach, however, is to affect the combustion reaction itself by provision of water in droplet form by means of a water injection system. This requires a high-pressure water pump and one or more injectors to obtain a spray of droplets of approximately 10 microns in diameter. These water droplets perform two functions. Primarily, the droplets cool the combustion chamber as the phase-change from water to vapour demands considerable thermal input. Secondarily, due to the significant expansion during the liquid-to-vapour phase-change, additional expansion energy in the combustion chamber can contribute to increased power delivered by the engine, leading thereby to lowering fuel consumption and associated C02 emissions. This is well known and understood and, as a technology, has been around for some considerable time. More recently, the German Automotive OEM, BMW, have announced the development of a water-injected vehicle which is planned for release in 2016/2017.

US2004221821 describes the use of pressurised hydrogen as a fuel for internal combustion engines. This patent proposes the use of pressurised hydrogen and water being co-injected into an engine in order to improve the combustion reaction. High pressure gas is employed to atomise the water, before the mixture of hydrogen and water mist is injected into the engine at pressure. The system requires specialised, expensive components, and is not suitable for retro-fitting to existing hydrogen fuelled vehicles. US5758606 describes a turbocharged engine that employs a complicated counter-flow technology for introducing water vapour into compressed airflow system downstream of the turbocharger. It employs numerous complicated components including heat exchangers, nozzles and injectors, and is designed for installation post-turbocharger and will therefore take up considerable space in the engine bay of the vehicle.

WO02089780 describes a water injection system, requiring numerous expensive components such as a pressure pump, heating element and valves in order to provide a mist that is injected into the air-stream of a vehicle. US5671701 describes a mist generation technology for a combustion engine that employs an ultrasound mist generator. The mist is mixed with air and fuel to provide a mixed stream pre-combustion. This mixing of fuel and mist gives rise to significant complexity of design, and, in practical terms, makes the provision of the combustible mixture to the engine extremely difficult, requiring a relatively unique carburation technology. Furthermore, the mixture in this form is combustible, requiring additional flash-back inhibitor technologies to prevent pre-ignition in the supply conduits.

It is an object of the invention to overcome at least one of the above-referenced problems. In particular, it is an object of the invention to decrease the amount of NOx emissions from an internal combustion engine.

Summary of the Invention The present invention is based on the finding that a fine aqueous mist, introduced into air in a combustion engine air intake (and/or into a gaseous fuel supply line), reduces the temperature of the engine and the level of NOx emissions from the engine. The droplets of the mist are smaller than the droplets generated by known water injection systems, in one embodiment about 5 microns, and therefore have a larger surface area allowing for faster and more efficient conversion to vapour and consequently a more aggressive cooling effect. In addition, the reduced droplet size allows the droplets to behave like a mist and are easily carried in a stream of gas (i.e. air). This ensures that it is evenly distributed on the incoming air-stream to the engine, and subsequently evenly distributed to each cylinder of the engine (in the case of multi-cylinder engines). It also allows for the mist to be induced post-filter into the air induction system and obviates the need for a complicated mist injection system. Tests carried out using a static diesel engine and an ultrasound mist generator configured to generate mist having an average droplet size of about 5 microns which is induced into the unpressurised air intake, have resulted in a 45% reduction of NOx emissions, compared with the usual 20% reduction achieved with conventional emission reduction technologies. In addition, in some embodiments, induction of a fine mist into the air intake has been found to clean the engine and boost engine power. In addition, induction of the mist into an air intake that is separate from the fuel intake provides a completely incombustible air supply to the engine, thereby obviating the requirement for additional flash-back inhibitor technologies to prevent pre-ignition in the supply conduits and specialist carburation technology. According to a first aspect of the present invention, there is provided a combustion engine of the type comprising a combustion chamber, an air intake configured to deliver air to the combustion chamber during operation, and an ultrasound aqueous mist generating module operably connected to the air intake and configured to generate an aqueous mist and induce the aqueous mist into air in the air intake, whereby a mixture of air and aqueous mist is delivered to the combustion chamber, characterised in that the engine comprises a fuel intake configured to deliver fuel to the combustion chamber separately from the mixture of air and aqueous mist.

In a further aspect, the invention provides hydrogen gas combustion engine of the type comprising a combustion chamber and a hydrogen gas intake configured to deliver hydrogen gas to the combustion chamber during operation, wherein the engine comprises an aqueous mist generating module operably connected to the hydrogen gas intake and configured to generate an aqueous mist and induce the aqueous mist into the hydrogen gas in the hydrogen gas intake, whereby a mixture of hydrogen gas and aqueous mist is delivered to the combustion chamber.

In one embodiment, the mist generating module is configured to generate droplets having an average dimension of 1 -8 microns. In one embodiment, the mist generating module is configured to generate droplets having an average dimension of about 2-8 microns. In one embodiment, the mist generating module is configured to generate droplets having an average dimension of about 3-8 microns. In one embodiment, the mist generating module is configured to generate droplets having an average dimension of about 3-7 microns. In one embodiment, the mist generating module is configured to generate droplets having an average dimension of about 4-6 microns.

In one embodiment, the aqueous mist generating module comprises an ultrasound aqueous mist generator. Examples of ultrasound (or ultrasonic) mist generators are known in the art, and are commonly used in air humidifiers. Other methods of generating aqueous mists are known, for example piezoelectric mist generators, ultrasonic nebulisers, vibrational micropumps, atomisers, and pressure activated devices. Ultrasound mist generators are easy to operate and relatively cheap. In addition, the droplet size attainable with ultrasound is much smaller than that attainable with pressurisation or spraying through a nozzlel , and is suitable for delivery into an air supply line passively by induction. In one embodiment, the aqueous mist generating module comprises a housing configured to contain a volume of aqueous liquid, a mist generator disposed within the housing, typically towards a base of the housing, and an air or gas inlet. Such an inlet may be operatively connected to the engine's air inlet manifold and configured to receive air from the air inlet manifold, and an outlet configured to provide a mixture of air and mist to the combustion chamber. Alternatively, the air inlet to the aqueous mist generator may be independently supplied with air from the environment. In one embodiment, the system comprises a fan for inducing mist from the mist generating module into the air/gas intake. In one embodiment, the fan is disposed in the air intake. In one embodiment, the system comprises an air filter for filtering air intake into the mist generating module. In one embodiment the housing is elongated (i.e. having a length greater than its width). This has been found to help reduce sloshing of water, and therefore help maintain contact between the mist generator and the water. In one embodiment, the housing is narrow, for example a width of less than 60cm, 50cm, 40cm, 30cm, 25cm, or 20cm. In one embodiment, the elongated housing is a cylinder. In one embodiment, the cylinder has a substantially circular or oval cross-section. In one embodiment, the cylinder has a polygonal cross section (for example square or rectangular).

In one embodiment, one of the air inlet or outlet is provided in a side of the housing, and the other of the air inlet or outlet is provided in a top of the housing.

In one embodiment, the air inlet and outlet are provided in a top of the housing. In one embodiment, the air inlet is provided towards one end of the housing and the outlet is provided towards an opposite end of the housing. In one embodiment, the housing comprises a plurality of inner housings, each having a mist generator (i.e. an ultrasound generator) disposed within the housing. In one embodiment, the inner housings have one or more openings at or adjacent the top and bottom to allow water enter the bottom of the inner housings and maintain the same water level in each of the housings, and mist exit the top of the inner housings. In one embodiment, the inner housings have an open bottom and/or open top. In one embodiment, the outlet comprises a manifold having a plurality of conduits configured to receive a mixture of air and fine mist from a side of each housing above the predefined water level. In one embodiment, each conduit comprises a drain to allow larger droplets to fall into the housing. The open bottom of the reservoir allows water in the housing fill each reservoir to a predefined level. During use, air enters the housing through an air inlet and enters each reservoir through the open top. A mist is generated in each reservoir, which is withdrawn through the side of each reservoir and into the outlet manifold, from where it is delivered to the combustion chamber. The use of multiple inner housing within an outer housing, where the inner housings are in fluid communication with each other (through the open bottom, or holes) has an anti- sloshing effect on the water when used with mobile combustion engines (such as cars) and helps keep the water in contact with the mist generator. The anti-sloshing effect is less of an issue with static engines, where a single housing may be employed

In one embodiment, the mist generating module comprises a water supply reservoir. In one embodiment, the mist generating module is configured for operative connection with the engine water supply system. In one embodiment, the mist generating module comprises a float switch or float valve operatively connected to the water supply and configured to maintain a defined level of water within the housing.

In one embodiment, the mist generating module comprises two housings, disposed side- by-side, and a conduit providing fluid communication between the housings configured to equilibrate water levels between the two housings. In none embodiment, the mist generator is disposed within one of the housings and a float switch/valve is disposed within the other housing. In one embodiment, the two housings are disposed within an outer housing (which is a reservoir for water), in which case the conduit may be replaced by apertures in the housings which allow water level equilibration. Typically, the housings are elongated (i.e. having a length greater than their width) which helps reduce sloshing. The use of two housings in fluid communication with each other, where the mist generator is disposed in one and the float switch in the other, is beneficial as it provides space for the float switch. Having both the float switch and mist generator in a single housing can be difficult especially when the housing is relatively narrow to help minimise sloshing of water. Examples of ultrasound aqueous mist generating modules are described below. In an embodiment where the engine includes one or more turbochargers, the aqueous mist generating module is operatively connected to the air intake manifold upstream of the or each turbocharger. Generally, the aqueous mist generating module is operatively connected to the air intake manifold downstream of the air filter.

In one embodiment, the mist generating module is configured for retrofitting to a

combustion engine, typically retro-fitting to an engine's air supply conduit. In one embodiment, the module comprises a water inlet configured for operatively connecting to the engine's water system and/or an electrical connector configured for connecting to an engine's electrical supply.

In one embodiment, the aqueous mist generating module is configured to generate a sufficient amount of fine mist to reduce the engine operation temperature while allowing the engine to continue operating. If too much water is provided to the engine in the form of mist, the engine will become saturated or flooded and the engine efficiency will drop and in many cases the engine will stop working. The amount of mist that is induced into the air intake will depend on the engine, the fuel, and the operating conditions, but these parameters can be determined by a person skilled in the art with routine experimentation. It is preferred that the amount of mist provided to the engine will be sufficient to allow at least 1 %, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 15%, 20%, 25%, 30%, 35%, 40% reduction of NOx emissions as determined by measurement of the exhaust gases with a gas analyser. In one embodiment, the engine is a vehicle engine. In one embodiment, the vehicle is a road vehicle, for example a bike, motorbike, car, van, truck, tractor, crane. In one embodiment, the vehicle is a non-road vehicle, for example a plane, ship, snowmobile, jetski, boat (where the engine is an inboard or outboard engine). In one embodiment, the engine is an electrical generator. In one embodiment, the engine is configured to employ a hydrocarbon fuel such as petrol, diesel, natural gas, LPG. In one embodiment, the engine employs a non-hydrocarbon gas, for example hydrogen or a mixture of oxygen and hydrogen. In one embodiment, the engine is configured to employ a mixture of a hydrocarbon fuel and a non-hydrocarbon fuel and in this embodiment, the mist may be added to the non-hydrocarbon fuel intake. In one embodiment, the engine is a jet engine. In another aspect, the invention provides a machine comprising an internal combustion engine of the invention. In one embodiment, the machine is a vehicle, for example a bike, motorbike, car, van, truck, tractor, crane, tractor, boat, ship, plane, submarine, space vehicle, snowmobile, and jetski. In one embodiment, the machine is an electrical generator. In one embodiment, the machine is a kiln or a heating appliance for a home or commercial building.

The aqueous mist employed in the present invention refers to a water mist. The water may include additives, for example a non-aqueous solvent such as ethanol or methanol. The additive may be liquid or solid. The additive may be an anti-freeze. The additive may be a hydrocarbon that aids phase change of the water to vapour or improves combustion.

In another aspect, the invention provides an aqueous mist generating module configured for retrofitting to a combustion engine. In one embodiment, the aqueous mist generating module comprises a housing configured to contain a volume of aqueous liquid, a mist generator disposed within the housing and typically towards a base of the housing, and a gas supply system configured to pass a gas through the housing such that an aqueous mist is induced into the gas, and deliver the mixture of gas and aqueous mist to the combustion chamber of the engine, typically via the air intake of the engine or when a gaseous fuel is employed, through the gaseous fuel intake. In one embodiment, the gas is air, and the aqueous mist generating module comprises an air inlet configured to operatively connect to the air inlet of the combustion engine and direct air into the housing, and an outlet configured to provide a mixture of air and mist to the combustion chamber (directly or via the air intake).

In one embodiment, the aqueous mist generating module comprises an air inlet (which may also comprise a fan and/or an air filter) to take ambient air from the environment, and direct air into the housing, and an outlet configured to provide a mixture of air and mist to the combustion chamber (directly or via the air intake).

In one embodiment, the system comprises a fan for inducing mist from the mist generating module into the air intake. In one embodiment, the fan is disposed in the air intake. In one embodiment, the system comprises an air filter for filtering air intake into the mist generating module. In one embodiment the housing is elongated (i.e. having a length greater than its width). This has been found to help reduce sloshing of water, and therefore help maintain contact between the mist generator and the water. In one embodiment, the housing is narrow, for example a width of less than 60cm, 50cm, 40cm, 30cm, 25cm, or 20cm. In one

embodiment, the elongated housing is a cylinder. In one embodiment, the cylinder has a substantially circular or oval cross-section. In one embodiment, the cylinder has a polygonal cross section (for example square or rectangular).

In one embodiment, the air inlet and outlet are provided in a top of the housing. In one embodiment, the air inlet is provided towards one end of the housing and the outlet is provided towards an opposite end of the housing.

In one embodiment, the housing comprises a plurality of inner housings, each having a mist generator (i.e. an ultrasound generator) disposed within the housing. In one embodiment, the inner housings have one or more openings at or adjacent the top and bottom to allow water enter the bottom of the inner housings and maintain the same water level in each of the housings, and mist exit the top of the inner housings. In one embodiment, the inner housings have an open bottom and/or open top. In one

embodiment, the outlet comprises a manifold having a plurality of conduits configured to receive a mixture of air and fine mist from a side of each housing above the predefined water level. In one embodiment, each conduit comprises a drain to allow larger droplets to fall into the housing. The open bottom of the reservoir allows water in the housing fill each reservoir to a predefined level. During use, air enters the housing through an air inlet and enters each reservoir through the open top. A mist is generated in each reservoir, which is withdrawn through the side of each reservoir and into the outlet manifold, from where it is delivered to the combustion chamber.

The use of multiple inner housing within an outer housing, where the inner housings are in fluid communication with each other (through the open bottom, or holes) has an anti- sloshing effect on the water when used with mobile combustion engines (such as cars) and helps keep the water in contact with the mist generator. The anti-sloshing effect is less of an issue with static engines, where a single housing may be employed In one embodiment, the mist generating module comprises a water supply reservoir. In one embodiment, the mist generating module is configured for operative connection with the engine water supply system. In one embodiment, the mist generating module comprises a float switch or float valve operatively connected to the water supply and configured to maintain a defined level of water within the housing.

In one embodiment, the mist generating module comprises two housings, disposed side- by-side, and a conduit providing fluid communication between the housings configured to equilibrate water levels between the two housings. In one embodiment, the mist generator is disposed within one of the housings and a float switch/valve is disposed within the other housing. In one embodiment, the two housings are disposed within an outer housing (which is a reservoir for water), in which case the conduit may be replaced by apertures in the housings which allow water level equilibration. Typically, the housings are elongated (i.e. having a length greater than their width) which helps reduce sloshing. The use of two housings in fluid communication with each other, where the mist generator is disposed in one and the float switch in the other, is beneficial as it provides space for the float switch. Having both the float switch and mist generator in a single housing can be difficult especially when the housing is relatively narrow to help minimise sloshing of water.

In another aspect, the invention provides a method of reducing the emissions of a combustion engine of the type having a combustion chamber and an air intake, reducing especially the NOx emissions, the method comprising the steps of inducing an aqueous mist into air in an air intake of a combustion engine to provide a mixture of air and aqueous mist, induction of the mixture of air and aqueous mist into a combustion chamber of the engine, separately supplying fuel to the combustion chamber, and combustion of the fuel, air and aqueous mist mixture, whereby the temperature of combustion is reduced compared to combustion in the absence of the aqueous mist. The level of aqueous mist induced into the air in the air intake will depend on the type of engine, the type of fuel and optionally the operating conditions, but is generally sufficient to lower the temperature of combustion and lower the level of emissions, especially NOx emissions, and/or clean the engine and/or boost the engine power. In one embodiment, the method of the invention employs a mist generator according to the invention, which may be retro-fitted to the engine.

In one embodiment, the aqueous mist stream from the mist generator of this design is combined with a gas stream as provided by a separate gas generation technology or a gas cylinder, in order to combine the effects of both mist and gas to reduce polluting exhaust emissions and improve fuel efficiency.

Other aspects and preferred embodiments of the invention are defined and described in the other claims set out below.

Brief Description of the Figures

The invention will be more clearly understood from the following description of some embodiment thereof, given by way of example only, with reference to the accompanying embodiments in which:

Figure 1 A is an illustration of a combustion engine according to the invention; Figure 1 B is an illustration of a combustion engine according to an alternative embodiment of the invention;

Figures 2A to 2C are illustrations of an aqueous mist generating module according to the invention, namely a top plan view with the lid removed (Fig. 2A), a perspective view with the lid removed (Fig. 2B), and a perspective view with the lid in-situ (Fig. 2C).

Figures 3A to 3C are illustrations of an aqueous mist generating module according to an alternative embodiment of the invention; Figures 4A to 4C are illustrations of an aqueous mist generating module according to an alternative embodiment of the invention;

Figure 5 is an illustration of an inner housing forming part of an aqueous mist generating module according to the invention; Figures 6A and 6B are illustrations of a mist generating module according to an alternative embodiment of the invention; and

Figure 7 is an illustration of a joining piece which allows streams of mist and gas (provided by a separate unit not shown) to combine as a mist/gas stream to the inlet of an engine.

Detailed Description of the Invention

All publications, patents, patent applications and other references mentioned herein are hereby incorporated by reference in their entireties for all purposes as if each individual publication, patent or patent application were specifically and individually indicated to be incorporated by reference and the content thereof recited in full.

Definitions and general preferences

Where used herein and unless specifically indicated otherwise, the following terms are intended to have the following meanings in addition to any broader (or narrower) meanings the terms might enjoy in the art: Unless otherwise required by context, the use herein of the singular is to be read to include the plural and vice versa. The term "a" or "an" used in relation to an entity is to be read to refer to one or more of that entity. As such, the terms "a" (or "an"), "one or more," and "at least one" are used interchangeably herein. As used herein, the term "comprise," or variations thereof such as "comprises" or

"comprising," are to be read to indicate the inclusion of any recited integer (e.g. a feature, element, characteristic, property, method/process step or limitation) or group of integers (e.g. features, element, characteristics, properties, method/process steps or limitations) but not the exclusion of any other integer or group of integers. Thus, as used herein the term "comprising" is inclusive or open-ended and does not exclude additional, unrecited integers or method/process steps.

As used herein, the term "induced" as applied to the supply or mist to a gas intake of an engine has its art-recognised meaning, namely that the mist is supplied to the air intake without any pressurised supply system as employed in injection systems. Exemplification

The invention will now be described with reference to specific Examples. These are merely exemplary and for illustrative purposes only: they are not intended to be limiting in any way to the scope of the monopoly claimed or to the invention described. These examples constitute the best mode currently contemplated for practicing the invention.

EXAMPLE 1

Referring to the drawings, and initially to Figures 1 and 1 (a), there is illustrated a

combustion engine according to the invention and indicated generally by the reference numeral 1 . The engine 1 comprises a combustion chamber 2 for combustion of fuel and air, an air intake 3 for providing ambient air to the combustion chamber, a fuel intake 4 for separately providing fuel to the combustion chamber 2, and an aqueous mist generating module 5 for generating an aqueous mist 1 1 and outlet conduit 10 that allows induction of the aqueous mist 1 1 into the air intake.

In more detail, the aqueous mist generating module 5 comprises a housing 6 containing water or aqueous solution 7 and an ultrasound generator 8, an air intake conduit 9 in fluid communication with an upstream part of the air intake 3, and an outlet conduit 10 in fluid communication with a downstream part of the air intake 3. The ultrasound generator is configured to convert water in the housing into a mist of fine droplets 1 1 having an approximate average dimension of 5 microns, forming a mist 1 1. In use, during operation of the engine in Fig. 1 , air is drawn into the air intake 3 and drawn into the housing 6 via the inlet conduit 9. Mist 1 1 that is generated in the housing is induced into the air, and the mixture of air/mist is returned to the air intake 3 via outlet conduit, where it is delivered to the combustion chamber, where it mixes with the fuel 12 and is combusted. The addition of a fine aqueous mist having a droplet size of about 5 microns reduces the temperature of combustion in the combustion chamber which reduces the level of NOx emissions.

In the engine of Fig 1 (a), the air is drawn into the housing via opening 13, which may contain a fan and/or an air filter, said air being drawn from the ambient surrounding environment. EXAMPLE 2

Referring to Figs. 2A to 2C, there is illustrated an aqueous mist generating module according to the invention and indicated generally by the reference numeral 20, in which parts identified with reference to the previous embodiment are assigned the same reference numerals. The aqueous mist generating module 20 as described is suitable for retro-fitting to a combustion engine, for example a combustion engine of an automotive vehicle. The module 20 comprises a fabricated PVC housing 6, which is subdivided by a number of internal baffles 21 into individual water reservoirs 22, each containing an ultrasound generator 8 at the base of the reservoir 22. The baffles do not fully separate the reservoirs, allowing water within the housing 6 communicate with each reservoir 22. The housing 6 comprises a removable sealing top 23 having an inlet conduit 24 and outlet conduit 25 disposed at opposite ends of the top 23. A float switch or float valve 26 of conventional design is provided to maintain a defined water level within the housing and is operatively connected to a water supply (not shown). Referring to Figure 5, the float switch or float valve may be housed in another cylindrical housing 27, within the reservoir housing 6 as a method of reducing the effect of sloshing which, in the case of mobile units, occurs during movement across rough terrain. Cylindrical housing 27 may have small holes 28 drilled in the wall close to the bottom to allow water levels to equilibrate slowly with those in the main reservoir housing. The water supply may be a separate water tank, or a conduit allowing water in the reservoir to be replenished from an external source. The use of this embodiment is the same as that described with reference to the previous embodiment.

EXAMPLE 3

Referring to Figs. 3A to 3C, there is illustrated an aqueous mist generating module according to the invention and indicated generally by the reference numeral 30, in which parts identified with reference to the previous embodiment are assigned the same reference numerals. The aqueous mist generating module 30 as described is suitable for retro-fitting to a combustion engine, for example a combustion engine of an automotive vehicle. Referring to Fig. 3B and 3C, the module 30 comprises an outer housing 6 and four inner housings 31 of cylindrical shape and having an open top and bottom. An air inlet 32 is provided in the housing 6 and in use receives air from an air intake of the engine (not shown), or from the ambient environment. An outlet conduit comprises a manifold of separate conduits 33, each of which is connected to an inner housing 31 on the side of the housing, and an outlet 35 for connection to the air intake of the engine downstream of the air inlet 32. Each of the conduits 33 includes a drain pipe 36 to allow large droplets of water fall out of the mist and into the reservoir of water in the housing 6.

In use, and referring to Fig, 3C, the outer housing 6 is filled with water up to a defined level, and consequently enters each of the inner housings 31 through their open bottoms. Air is drawn into the outer housing 6 through the inlet 32 and enters each of the inner housings 31 through their open tops. Holes 38 may be provided at the bottoms of housings 31 , positioned under the water level, to ensure that the water level is balanced throughout the unit. The ultrasound generator 8 in each inner housing 31 is actuated using an electrical supply (not shown) and generates a fine mist in the headspace of each inner housing comprising fine droplets of water suspended in air. The mist mixes with the incoming air and is drawn out of the housing 31 into conduits 33, where the air/mist mixture is withdrawn from the housing through the outlet 35 and back to the air intake of the engine, and then induced into the combustion chamber of the engine (as previously described). Any large droplets in the mist (droplets too large to be suspended in air) and any condensed water from the outlet are allowed to drain from the mist through the drain pipes 36 and 37, and are returned to the reservoir of water in the housing 6.

EXAMPLE 4

Referring to Figures 4(a) to 4(c), there is illustrated an aqueous mist generating module according to an alternative embodiment of the invention and indicated generally by the reference numeral 40, in which parts identified with reference to the previous embodiment are assigned the same reference numerals. In this embodiment, the mist generator is provided as a single unit that is suitable for use on a smaller capacity engine, wherein the mist generator 8 sits in a first cylinder 41 , with float switch/float valve 26 positioned in a second adjacent cylinder 42. The two cylinders are in fluid communication with each other by way of conduit 43, disposed intermediate the length of the cylinders, and at the bottom through communicating water top-up system 44. In this configuration, the water level is maintained by the float switch/float valve in the second cylinder 42, while the mist is generated in the first cylinder 41 . A fan 32, disposed at the top of cylinder 41 , forces air and mist through the communicating ports 43, and out through outlet conduit 35, to the air intake of the engine. As water is consumed by the mist generator, it is topped up from a separate reservoir (not shown) through top-up system 44 as demanded by float switch/float valve 26. EXAMPLE 5

Referring to figures 6(a) and 6(b), there is illustrated an aqueous mist generating module according to an alternative embodiment of the invention and indicated generally by the reference numeral 60, in which parts identified with reference to the previous embodiment are assigned the same reference numerals and comprising a housing 61 in which sit multiple mist generators 8. An air inlet 62 and an outlet 65 are disposed in a lid 64of the housing. In this arrangement, the mist generators sit in an aqueous solution of appropriate depth, controlled by a float switch or float valve (not shown), wherein the mist generated is carried on the air-stream through the box and out of the outlet, towards the air intake of the engine.

This arrangement is appropriate for static engines such as those which drive generators. EXAMPLE 6

Referring to Figure 7, there is illustrated a joining piece the use of which allows for combining the streams of mist as generated by a mist generator, through tube 72 with a stream of gas which may come from a gas generator or from a gas storage bottle, through tube 71 , whereby both streams are mixed and supplied to a combustion engine as a mixed mist/gas stream through tube 73 in order to further improve combustion efficiency and lower polluting emissions. This embodiment is useful for engines that employ non- hydrocarbon fuels, or a mixture of hydrocarbon and non-hydrocarbon fuels, where mist is added to the non-hydrocarbon fuel (i.e. hydrogen gas) prior to supply to the combustion chamber.

EXAMPLE 7

The aqueous mist generating module of Example 2 was retro-fitted to, and tested on, two engines, a 2.2 litre Ford Transit engine and a 15 Litre static generator engine. The test on the Ford Transit engine provided positive results, showing a reduction of NOx generated of approximately 60%. For the generator test, the air filter was removed and the mist generating module was connected to the air induction tube upstream of the turbocharger. Reduction of NOx emissions of between 38% and 45% was achieved.

The ultrasound generator used in both current designs is typical of those used for creating a mist over a garden pond, being readily available and inexpensive. Other types and sizes of mist generator may also be used, dependent upon practical considerations of energy consumption (currently very low at around 0.5A X 24V per mist generator), available space and design of mist generation/provision module.

Equivalents

The foregoing description details presently preferred embodiments of the present invention Numerous modifications and variations in practice thereof are expected to occur to those skilled in the art upon consideration of these descriptions. For example, while the specification predominantly describes induction of an aqueous mist into air, and apparatus for achieving such induction, it will be appreciated that the methodology and apparatus is applicable for the induction of an aqueous mist into a gaseous fuel which is then supplied to the combustion chamber of the engine. Thus, the use of "air", "air inlet", "mixture of air and aqueous mist" may be replaced with "gaseous fuel", "gaseous fuel inlet" and "mixture of gaseous fuel and aqueous mist". Those modifications and variations are intended to be encompassed within the claims appended hereto.

Claims

CLAIMS:

1 . A combustion engine of the type comprising a combustion chamber, an air intake configured to deliver air to the combustion chamber during operation, and an ultrasound aqueous mist generating module operably connected to the air intake and configured to generate an aqueous mist and induce the aqueous mist into air in the air intake, whereby a mixture of air and aqueous mist is delivered to the combustion chamber, characterised in that the engine comprises a fuel intake configured to deliver fuel to the combustion chamber separately from the mixture of air and aqueous mist.

2. A combustion engine according to Claim 1 in which when the engine comprises a turbocharger, the ultrasound aqueous mist generating module is operatively connected to the air intake upstream of the or each turbocharger.

3. A combustion engine according to Claim 1 or 2 in which the mist generating module is configured to generate droplets having an average dimension of 1 -8 microns.

4. A combustion engine according to Claim 3 in which the aqueous mist generating module is configured to generate droplets having an average dimension of about 3-7 microns.

5. A combustion engine according to any preceding Claim in which the combustion engine is a petrol or diesel engine.

6. A combustion engine according to any preceding Claim in which the aqueous mist generating module comprises a housing configured to contain a volume of aqueous liquid, a mist generator disposed within the housing and typically towards a base of the housing, and an air supply system configured to receive air, pass the air through the housing such that an aqueous mist is induced into the air, and deliver the mixture of air and aqueous mist to the combustion chamber of the engine.

7. A combustion engine according to Claim 6 in which the aqueous mist generating module comprises an air inlet configured to operatively connect to the air inlet of the combustion engine and direct air into the housing, and an outlet configured to provide a mixture of air and mist to the combustion chamber via the air intake.

8. A combustion engine according to Claim 7 in which one of the air inlet or outlet is provided in a side of the housing, and the other of the air inlet or outlet is provided in a top of the housing.

9. A combustion engine according to Claim 7 or 8 in which the air inlet and outlet are provided in a top of the housing and the air inlet is provided towards one end of the housing and the outlet is provided towards an opposite end of the housing.

10. A combustion engine according to any of Claims 6 to 9 in which the housing comprises a plurality of inner housings disposed within an outer housing, each inner housing having a mist generator disposed within the inner housing, one or more openings at the bottom of each inner housing configured to allow water level equilibration between the inner housings, and one or more openings at the top of each housing to allow the aqueous mist leave the inner housings.

1 1 . A combustion engine according to Claim 10 in which the inner housings have an open bottom and top.

12. A combustion engine according to any of Claims 7 to 1 1 in which the outlet comprises a manifold having a plurality of conduits configured to receive a mixture of air and fine mist from a side of each housing above the predefined water level.

13. A combustion engine according to Claim 1 1 in which each conduit comprises a drain to allow larger droplets fall into the housing.

14. A combustion engine according to any preceding in which the mist generating module comprises a float switch or float valve configured to maintain a defined level of water within the housing.

15. A combustion engine according to any of Claims 1 to 8 in which the housing of the aqueous mist generator comprises two individual housings, one of which comprises a mist generator and the other of which comprises a float valve/switch, wherein the housings are configured to be in fluid communication with each other.

16. A combustion engine according to Claim 15 including a conduit providing fluid communication between the housings.

17. A combustion engine as claimed in Claim 16 including a first conduit providing water communication between the bottom of the housings, and a second conduit providing mist communication between the housings.

18. A combustion engine according to any preceding Claim in which the engine includes one or more turbochargers, and wherein the aqueous mist generating module is

operatively connected to the air intake upstream of the or each turbocharger.

19. A combustion engine according to any preceding Claim in which the gas is a non- hydrocarbon gaseous fuel, the gas intake is a gaseous fuel intake, and the mixture of gas and aqueous mist is a mixture of gaseous fuel and aqueous mist.

20. A combustion engine according to Claim 19 in which the non-hydrocarbon gaseous fuel is hydrogen gas.

21 . A combustion engine according to any preceding Claim which is an automotive engine.

22. A machine comprising a combustion engine according to any preceding Claim.

23. A machine according to Claim 22 selected from a car and an electrical generator.

24. An aqueous mist generating module configured for retrofitting to a gas intake of a combustion engine and delivery of a mixture of gas and an aqueous mist into a combustion chamber of the combustion engine.

25. An aqueous mist generating module as claimed in Claim 24 in which the gas is air, the gas intake is an air intake, and wherein the module is configured to deliver a mixture of air and aqueous mist into the combustion chamber of the combustion engine, directly or via an engine air intake.

26. An aqueous mist generating module according to Claim 24 or 25 in which the aqueous mist generating module comprises an ultrasound aqueous mist generator.

27. An aqueous mist generating module according to Claim 24 to 26 and comprising a housing configured to hold a reservoir of water, a mist generator disposed within the housing, an air intake conduit configured to operatively connect to an air intake and supply air from the air intake conduit to the housing, and an outlet conduit configured to operatively connect to the air intake downstream of the air intake conduit and provide a mixture of air and aqueous mist to the air intake for delivery to the combustion chamber of the engine.

28. An aqueous mist generating module according to Claim 27 in which one of the air inlet or outlet conduits is provided in a side of the housing, and the other of the air inlet or outlet is provided in a top of the housing.

29. An aqueous mist generating module according to Claim 27 in which the air inlet and outlet conduits are provided in a top of the housing on opposite ends of the housing.

30. An aqueous mist generating module according to any of Claims 24 to 29 in which the housing comprises a plurality of water reservoirs, each having a mist generator disposed within the reservoir.

31 . An aqueous mist generating module according to Claim 30 in which each reservoir comprises a separate housing having an open top and open bottom,

32. An aqueous mist generating module according to Claim 30 or 31 in which the outlet conduit comprises a manifold having a plurality of conduits configured to receive a mixture of air and fine mist from a side of each separate housing above the predefined water level.

33. An aqueous mist generating module according to Claim 32 in which one or more of the plurality of conduits comprises a drain to allow larger droplets fall into the housing.

34. An aqueous mist generating module according to any of Claims 25 to 33 and including a fan configured to induce an aqueous mist into the air intake of the engine.

35. An aqueous mist generating module according to any of Claims 25 to 34 in which an air intake to the mist generation module is configured to take ambient air from the surrounding environment, being unconnected to the air intake of the engine.

36. An aqueous mist generating module of claim 35, in which the air intake to the module incorporates a fan to move the air-mist toward the outlet of the mist generating module and onward to the air intake of the engine.

37. An aqueous mist generating module of any of Claims 25 to 36, in which an air filter is placed in an air intake of the module.

38. An aqueous mist generating module according to any of Claims 24 to 37 in which a float switch or float valve is housed in a separate housing within the reservoir housing, said separate housing functioning to reduce the effect of sloshing within the reservoir housing when installed in a mobile vehicle.

39. An aqueous mist generating module according to Claim 24, in which the gas is a gaseous fuel, and wherein the aqueous mist generating module is configured for retrofitting to a gaseous fuel supply line and delivery of a mixture of gaseous fuel and an aqueous mist into a combustion chamber of the combustion engine.

40. A method of reducing the emissions of a combustion engine of the type having a combustion chamber, a fuel intake and an air intake separate to the fuel intake, reducing especially the NOx emissions, the method comprising the steps of inducing an aqueous mist into air in an air intake of a combustion engine to provide a mixture of air and aqueous mist, induction of the mixture of air and aqueous mist into the combustion chamber, separately supplying fuel to the combustion chamber, and combustion of the fuel, air and aqueous mist mixture, whereby the temperature of combustion is reduced compared to combustion in the absence of the aqueous mist.

41. A method according to Claim 40 in which the fuel is selected from petrol or diesel.