GB2567704A

GB2567704A - Method for fuelling diesel engines

Info

Publication number: GB2567704A
Application number: GB1804632.6A
Authority: GB
Inventors: Binns Frederick
Original assignee: Individual
Current assignee: Individual
Priority date: 2018-03-22
Filing date: 2018-03-22
Publication date: 2019-04-24
Also published as: WO2019180249A1; GB201804632D0

Abstract

A method for reducing pollution caused by combustion of fuel in a diesel engine, comprising adding hydrogen to diesel fuel prior to combustion of diesel fuel in a diesel engine, characterised in that hydrogen is introduced to diesel fuel in a fuel feed line 1, directly prior to a fuel pump 3; Also disclosed is the use of hydrogen as a secondary fuel in a diesel engine, a diesel engine, and a vehicle comprising such a diesel engine. The method allows for convenient design of new engines, or easy modification of existing diesel engines to reduce fuel consumption per unit energy output.

Description

(57) A method for reducing pollution caused by combustion of fuel in a diesel engine, comprising adding hydrogen to diesel fuel prior to combustion of diesel fuel in a diesel engine, characterised in that hydrogen is introduced to diesel fuel in a fuel feed line 1, directly prior to a fuel pump 3; Also disclosed is the use of hydrogen as a secondary fuel in a diesel engine, a diesel engine, and a vehicle comprising such a diesel engine. The method allows for convenient design of new engines, or easy modification of existing diesel engines to reduce fuel consumption per unit energy output.

High Pressure Fuel out (to engine)

Figure 1 - schematic diagram of fuel system.

Low Pressure

Diesel in (from fuel tank)

This print incorporates corrections made under Section 117(1) of the Patents Act 1977.

1/3

High Pressure Fuel out (to engine)

Figure 1 - schematic diagram of fuel system.

Low Pressure

Diesel in (from fuel tank)

Figure 2 - Hydrogen introduction pipe narrowing to 1mm o.d., 0.5mm i.d.

2/3

Figure 3 - hydrogen introduction pipe in place in fuel line prior to fuel pump

Figure 4 - hydrogen feed line with tap and air-bleed

3/3

Figure 5 - Inlet point to hydrogen inlet line, for connection to hydrogen cylinder

Method for Fuelling Diesel Engines

FIELD OF THE INVENTION

The present invention relates to methods for introducing a gaseous secondary fuel into a liquid-fuelled internal combustion engine. In particular, the invention relates to methods for introducing hydrogen into diesel engines and to related embodiments.

BACKGROUND

The internal combustion engine is now ubiquitous in modern life. Such engines provide easy and convenient power, particularly for the transportation of people and of goods, and many millions of such engines are operated every day.

Most internal combustion engines operate by the combustion of hydrocarbon fuels and consequently the primary combustion products of these fuels are water vapour and carbon dioxide. However, in recent years, there has been a global effort to reduce the emission of carbon dioxide since this is widely believed to contribute to currently observed warming of the earth’s atmosphere and consequent changes in the global climate.

Motive power at a fixed point may be provided by “low carbon” alternatives to combustion engines such as electric motors, which may in turn be powered through fixed power lines from low-carbon electrical sources such as wind, solar or nuclear power. Current battery technology, however, limits the range and performance of electric vehicles which, at the present time, are beginning to enter the market for personal transportation but have made little or no impact on commercial vehicles.

A valuable step towards a reduction in carbon dioxide emissions from vehicles would be to reduce the amount of hydrocarbon used. This has been addressed by use of smaller, more efficient engines and improved aerodynamic design but further contributions to this area would be of value. Furthermore, there are many millions of existing vehicles which cannot benefit readily from these advances and which will remain in economic use for many years to come.

One approach to reducing the amount of hydrocarbon fuel consumed by an engine is to use hydrogen as a fuel. Since hydrogen can be generated from water using electricity from low-carbon generation, this would effectively provide an extension of low-carbon electric power to more vehicles. However, use of purely hydrogen in an internal combustion engine requires large volumes to be carried in the vehicle and hydrogen storage, although the subject of considerable research over recent decades is not a well-developed technology. The range of a purely hydrogenpowered vehicle would thus most likely be limited by the quantity of hydrogen which might reasonably be carried. Existing vehicles are also unlikely to be economically modified to run purely on hydrogen, even if the storage issues can be overcome.

An alternative to purely hydrogen-fuelled vehicles would be the use of hydrogen as a secondary fuel in existing internal combustion engines. This requires either the design of a new engine or modification of existing engines to allow dual-fuel operation. Two existing approaches have been devised to achieve this.

U.S. Pat. No. 5,408,957 discloses the use of LPG (propane), natural gas, hydrogen gas, or the like, which is continuously injected at substantially constant pressure into the air intake manifold, or air induction system, of a conventional internal combustion engine, the engine being electronically, or mechanically, controlled to adjust the air to liquid fuel mixture to a optimum value. U.S. Pat. No. 5,370,097 discloses a dual fuel control system for use with an internal combustion engine which controls the flow of liquid fuel alone or in combination with a gaseous fuel. US 2011/301826 discloses a conventional gasoline engine that is retrofitted to operate as a bi-fuel engine calibrated to burn hydrogen gas as a primary fuel and gasoline as a secondary fuel at various acceptable air fuel ratios while avoiding forbidden air fuel ratios. WO 99/30024 relates to a method for producing NOx reductants by injecting hydrocarbon into a diesel engine's combustion chamber during the expansion cycle.

It is evident that hydrogen has previously been considered for introduction by direct injection into the cylinder(s) of an internal combustion engine or by introduction into the air intake system. Evidently, the former method requires considerable modification to an engine, requiring at least the design and fitment of a new cylinderhead and injection system, while the latter method runs the risk of generating explosive fuel/air mixtures in the air intake system prior to reaching the cylinders. This evidently requires a high degree of skill to design and validate a system which will be safe to use and most likely requires a bespoke solution for each model of vehicle to be modified.

In view of the above, it would clearly be of considerable value to provide a method for reducing pollution from an internal combustion engine which could be easily incorporated into the design of new engines and/or could be retro-fitted to existing engines without requiring major modification or exacting design to ensure a safe and convenient solution.

SUMMARY OF THE INVENTION

The present inventor has now established that by introduction of hydrogen at an appropriate point in the fuel-delivery system of a diesel-fuelled internal combustion engine (diesel engine), hydrogen may be used as a secondary fuel in such diesel engines at a wide range of proportions. Such a method potentially allows for convenient design of new engines and/or facile modification of existing diesel engines, thereby reducing the amount of diesel fuel consumed per KW of energy output and/or reducing the amount of pollution relative to an unmodified engine.

In a first aspect, the present invention thus provides a method for reducing the pollution caused by combustion of fuel in a diesel engine, said method comprising adding hydrogen to diesel fuel prior to combustion of said diesel fuel in said diesel engine, characterised in that said hydrogen is introduced to said diesel fuel in a fuel feed line, directly prior to a fuel pump.

Corresponding, in a second aspect, the invention provides the use of hydrogen as a secondary fuel in a diesel engine, characterised in that said hydrogen is introduced to said engine by addition to a diesel fuel line directly prior to a fuel pump. Such use will typically be to reduce pollution from such an engine.

Where reduction of pollution is indicated herein, this will typically be a reduction in carbon dioxide generated. Reduction may be per unit of time (e.g. per second or per hour) during which the engine is run or more typically will be reduction per unit of work (e.g. per kilojoule) output, or per unit of power (e.g. per kilowatt) output. Such reduction in pollution is considered further below.

Since the present invention allows for a diesel engine designed and/or modified to run effectively on diesel and hydrogen mixtures, in a further aspect the invention further provides a diesel engine configured to accept an input of hydrogen into at least one diesel fuel feed line, characterised in that said hydrogen is introduced to said diesel fuel in a fuel feed line, directly prior to a fuel pump. Conventional diesel engines of all types may be suitably modified, either before or after production with such a configuration.

Since the use of lower-polluting diesel engines is particularly valuable for use in vehicles, where providing electrical power for long periods is difficult, in a still further aspect, the invention further provides a vehicle comprising a diesel engine as described herein.

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to methods and uses for reducing pollution from a diesel-fuelled internal combustion engine (diesel engine) as well as corresponding engines and vehicles. It is evidently desirable to reduce emissions from all sources but emissions from diesel engines are particularly important because such engines are used daily in huge numbers. The fact that diesel engines are often used in close proximity to people including areas of high population density, such as cities, is a further factor arguing for reductions in diesel engine emissions.

Although reduction of emissions to zero is potentially desirable, a more modest reduction can still provide a valuable contribution where the use is widespread. Diesel combustion in the US in 2016, for example, is estimated to have released 437 million metric tons of CO₂ into the atmosphere. Even a modest reduction in such large numbers could prove a significant environmental benefit and also contribute towards attainment of goals for lowering emissions. Reductions in other pollutants such as unburned fuel and carbon particulates would provide an additional or alternative benefit.

In the present application the term “reducing pollution”, “reduction of pollution” and related terms indicates a reduction in the release of carbon dioxide from a diesel engine when compared with an equivalent engine configured to run purely on diesel fuel. Thus, for example, reduction in CO₂per kilojoule of fuel burned may be reduced by at least 10% (e.g. 10 to 80%), preferably at least 20% and more preferably by at least 30% over an equivalent engine configured to use diesel as sole fuel. Similarly, the reduction may be per unit of time (e.g. per second or per hour) during which the engine is run or more typically will be reduction per unit of work (e.g. per kilojoule) output, or per unit of power (e.g. per kilowatt) output. In each case, a reduction in CO₂ generated of at least 10% (e.g. 10 to 80%), preferably at least 20% and more preferably by at least 30% over an equivalent engine configured to use diesel as sole fuel.

In some embodiments, it may be preferable to configure and engine or enginemanagement system (mechanical or preferably electronic) such that the proportion of hydrogen in the fuel mixture will vary depending upon the demands being placed on the engine. Where a reduction in pollution is indicated herein, this is preferably the “worst case” situation, which will typically be where the engine is instantaneously configured to use the greatest proportion of diesel fuel and the lowest proportion of hydrogen. Alternatively, such reductions may be over a “cycle” of engine use, such as those used for emissions testing for vehicles and engines. Typical examples of such cycles include the US Federal Test Procedure “Heavy-Duty FTP Transient Cycle” or the corresponding “FTP-75” cycle for lighter duty vehicles. Corresponding test cycles used in other jurisdictions could also be appropriate, such as the “European Transient Cycle” for heavy duty engines or the “New European Driving Cycle (NEDC)” (“MVEG-B”) test cycle for light duty engines.

In the present application, hydrogen is used as a secondary fuel in a “diesel engine”. Such an engine is used herein to indicate an engine in which fuel ignition takes place without any spark as a result of compression of the inlet air mixture and injection of fuel. Diesel engines may have at least one of Glow plugs, grid heaters, block heaters and other methods known in the art help achieve high temperatures for combustion (e.g. during engine startup and/or in cold conditions). However, such engines will not have the “spark” ignition typical of gasoline engines. Diesel fuel, as used herein, is correspondingly any liquid fuel used or usable in diesel engines.

Examples of diesel fuels include petroleum diesel, synthetic diesel fuel, biodiesel and mixtures thereof. It is of particular advantage to employ the various embodiments of the present invention where a diesel fuel comprising at least a portion of fossil-fuel derived diesel fuel would otherwise be employed. By replacing some fossil-fuel derived diesel fuel in a diesel engine, the total amount of carbon dioxide released from fossil sources is reduced. In one embodiment, therefore, “diesel fuel” as indicated herein may comprise at least a portion of fossil-fuel derived diesel fuel, such as petroleum diesel and/or synthetic diesel. Mixtures of such fossil-fuel derived diesel fuel with biodiesels may evidently also be used.

Petroleum diesel is fossil fuel derived and is the most common type of diesel fuel. It is produced from the fractional distillation of crude oil between 200 °C (392 °F) and 350 °C (662 °F) at atmospheric pressure, resulting in a mixture of carbon chains that typically contain between 8 and 21 carbon atoms per molecule. In one embodiment, “diesel fuel” as referred to herein may comprise, consist essentially of or consist of Petroleum diesel.

Synthetic diesel may be generated from fossil-fuel sources such as coal or crude oil but can be produced from any carbon-containing material such as biomass, biogas, natural gas, coal and many others. The raw material is gasified into synthesis gas, which after purification is converted by the Fischer-Tropsch process to a synthetic diesel. Coal-to-liquid (CTL) synthetic diesel is a common fossil-fuel derived synthetic diesel. Paraffinic synthetic diesel is another fossil-fuel derived diesel fuel. This has the advantage of a near-zero sulphur content and low content of aromatics. The may lower the production of hydrocarbons, nitrous oxides and particulate matter from a diesel engine, in comparison with petroleum diesel fuel. Where synthetic diesel is indicated here, this may in one embodiment be a fossil-fuel derived diesel, such as CTL diesel fuel and/or paraffinic diesel fuel.

Biodiesel is typically a vegetable oil- or animal fat-based diesel fuel comprising alkyl esters of long-chain fatty acid moieties. Biodiesel is typically made by esterification of fatty acids from natural sources (e.g., vegetable oil, rapeseed oil, soybean oil, and/or animal fat) with an alcohol (e.g. methanol or ethanol) to produce fatty acid esters. Biodiesels such as “fatty-acid methyl ester” (FAME), and/ or the equivalent ethylester product may be used pure in appropriate diesel engines, but it is more often used as a mix with fossil-fuel derived diesel(s) such as petroleum diesel.

A second category of biodiesels are hydrogenated oils and fats. These are synthesised by converting the triglycerides in vegetable oil and animal fats into alkanes by refining and hydrogenation. The produced fuel has many properties that are similar to synthetic diesel, and may be used with petroleum diesel or other diesels of fossil-fuel origin.

Since hydrogen contains no sulphur, the emissions of sulfur oxides and sulfates, major components of acid rain, may be reduced in the various aspects of the present invention (relative to an equivalent use of petroleum diesel, as discussed herein). This may be in addition to any reduction in carbon dioxide production. In one embodiment, the present invention may therefore provide (in any aspect) for a reduction in at least one exhaust component selected from sulfur oxides, sulfates, NOx, unburned hydrocarbons and/or particulate carbon. This my preferably be in addition to a reduction in CO₂. In all cases, this comparison will typically be against an equivalent engine running on diesel as sole fuel and particularly running on petroleum diesel as sole fuel.

A key feature of the various aspects of the present invention is the introduction of hydrogen gas to a diesel fuel line directly prior to a fuel pump. This is illustrated in Figure 1 below. In this method, low pressure diesel fuel is drawn from a reservoir (“diesel fuel tank”) at low pressure (e.g. approximately atmospheric pressure) along a fuel line (1) by means of a fuel pump (3). Such fuel pumps are well known for use in engines including diesel engines and may, for example, be a mechanical or electrical fuel pump but will typically be an electrical fuel pump. Prior to reaching the fuel pump (3), the fuel line is joined by a hydrogen inlet line (2). This hydrogen inlet line (2) introduces hydrogen to the fuel from a hydrogen reservoir (such as a hydrogen tank or cylinder). Since the hydrogen is introduced into a low-pressure fuel line, the hydrogen does not need to be handled at high pressure and may be introduced at slightly above atmospheric pressure (e.g. 0.01 to 1 bar above atmospheric pressure, such as 0.05 to 0.3 bar above atmospheric pressure). The fuel pump (3) then serves to pressurise the diesel fuel and entrained hydrogen to a pressure suitable for injection into the combustion chambers of the diesel engine.

In the present invention, the diesel engine may be a “simple direct injection” or “common rail direct injection” diesel engine. In the case of a simple direct injection diesel having a fuel feed pump and an injection pump, the hydrogen inlet line (2) will typically be positioned directly prior (up-stream) of the fuel feed pump. However, the hydrogen inlet line (2) may be positioned directly prior to the injection pump.

In a preferred embodiment, the diesel engine may be a “common rail direct injection” diesel engine. This is advantageous because pressures of around 100 bar or greater are typically generated by the fuel pump (3) in such common rail diesel engines and such a high pressure may serve to compress, compact or dissolve the hydrogen secondary fuel into the diesel primary fuel for injection. In one embodiment, the fuel pump (3) may be a high pressure fuel pump, supplying fuel at a pressure of not less than 50 bar (e.g. 50 to 10,000 bar), preferably not less than 75 bar and more preferably not less than 95 bar (e.g. 100 to 5000 bar).

In the various aspects of the present invention, the hydrogen secondary fuel may be introduced to the diesel fuel directly prior to a fuel pump. This indicates primarily that no other major components of the fuel system should be present in the fuel line between the point of hydrogen introduction and the fuel pump. Without being bound by theory, it is believed that by introducing the hydrogen secondary fuel directly prior to the fuel pump, the two fuels remain well mixed upon reaching the pump and are then compressed together in the high pressure fuel line (4).

Since the hydrogen fuel is not mixed with oxygen from the air prior to entering the combustion chamber, the risk of a hydrogen explosion is greatly reduced in comparison with systems having hydrogen gas introduced into the air-intake system of the engine. Furthermore, since the hydrogen is compressed or compacted into the liquid fuel, only a single set of injectors is required for the fuel mixture. Separate injection of hydrogen, in contrast, requires a second complete injection system including handling of high pressure hydrogen, which adds significant complexity to the engine and makes retro-fitting of such technology to an existing engine complex and difficult. In contrast, the present invention may be implemented by simple modification of an existing diesel engine without modification of the cylinder head.

In the various aspects of the present invention, the proportion of hydrogen to diesel fuel may be varied in order to achieve desired goals. A minimum amount of diesel fuel may be required in order to ensure effective ignition of the fuel/air mixture. However, providing that minimum amount is maintained, the ratio may be varied as required. For example, the calorific ratio of diesel fuel: hydrogen may be between 99:1 and 1:99, preferably between 90:10 to 10:90. In one embodiment, at least 50% of the energy intake of the engine may be provided by hydrogen. In such an embodiment, it will be preferable for the calorific ratio of diesel fuel: hydrogen to be between 50:50 and 10:90.

The proportion of hydrogen in the fuel mixture may be fixed for a particular engine or engine configuration, or may be varied, such as by the engine control system of the engine. Where the engine control system controls the proportion of hydrogen in the fuel, this may be such that the proportion of hydrogen increases when the engine is under lower load (e.g. less than 50% of maximum load) and decreases when the engine is under greater load (e.g. greater than 50% of maximum load). Evidently, this adjustment may take place in steps or by continuously varying the proportion of hydrogen (e.g. with an inverse relationship to the engine load). In a similar embodiment applicable to all aspects, the hydrogen may be introduced into the diesel fuel at a calorific ratio which is inversely related to the required torque of the engine.

In one aspect, the present invention relates to a diesel engine configured to accept an input of hydrogen (especially hydrogen gas at less than 5 bar above ambient) into a least one diesel fuel line. Such engine may be a simple direct injection diesel engine or more preferably a common rail direct injection diesel engine. Such an engine may have an engine management system (typically an electronic engine management system) configured to reduce the pollution from the engine (as discussed herein) by the introduction of hydrogen into diesel fuel in a feed line or similar structure directly prior to a fuel pump. Such an engine management system may be configured to implement any of the proportions or ratios of fuel or relationships between load or torque and fuel described herein.

The invention will now be further described by reference to the following non-limiting examples and to the attached Figures, in which:

Figure 1 - shows a schematic representation of the fuel system applicable to all aspects of the invention: 1 - Fuel line; 2 - Hydrogen inlet line; 3 - Fuel pump; 4 Fuel outlet line (to engine combustion chambers(s)).

Figure 2 - photograph showing the hydrogen introduction pipe (inlet line) narrowing to 1mm outside diameter (0.5mm inside diameter).

Figure 3 - photograph showing the hydrogen inlet line going into the fuel line directly prior to the fuel pump.

Figure 4 - photograph showing the hydrogen inlet line with optional tap and air-bleed screw.

Figure 5 - photograph showing the end of the hydrogen inlet line for connection to a hydrogen cylinder.

EXAMPLE

Hydrogen was introduced to the fuel line of a diesel engine (Isuzu trooper 3.1 L capacity), directly at the fuel inlet port of the fuel pump (Fig 3). The pump was a 2000 bar high-pressure fuel pump feeding the diesel injectors. Hydrogen was introduced into the fuel line immediately prior to the fuel inlet port of the fuel pump by means of tube with internal diameter 0.5mm (external diameter 1mm) (Fig 2). The hydrogen from a hydrogen cylinder was regulated to 0.1 bar above ambient pressure and the introduction of hydrogen controlled by regulating the flow.

The diesel engine was initially held at tick-over at approximately 500 rpm. While maintaining the diesel fuel at tick-over level, hydrogen was introduced into the fuel line prior to the fuel pump and the engine speed observed to rise to 2000 rpm. Control of the hydrogen flow allowed the engine speed to be controlled to around 1000 rpm.

Taking the engine speed as indicative of the calorific value of the fuel and assuming that the diesel fuel continued to be fed at a constant rate, it appears that the engine functioned normally with the introduction of up to around three parts hydrogen fuel to one part diesel fuel (diesel: hydrogen ratio of 25:75). Higher levels of hydrogen were not tested but no indication was seen of this being a maximum value.

Claims

1) A method for reducing pollution caused by combustion of fuel in a diesel engine, said method comprising adding hydrogen to diesel fuel prior to combustion of said diesel fuel in said diesel engine, characterised in that said hydrogen is introduced to said diesel fuel in a fuel feed line, directly prior to a fuel pump.

2) The method of claim 1 wherein said reduction of pollution comprises a reduction of carbon dioxide generation.

3) The method of claim 2 wherein said reduction of pollution additionally comprises a reduction of at least one exhaust component selected from sulfur oxides, sulfates, NOx, unburned hydrocarbons and/or particulate carbon.

4) The method of any preceding claim wherein said hydrogen is introduced into said diesel fuel at a calorific ratio of diesel fuel: hydrogen of 99:1 to 1:99, preferably 90:10 to 10:90.

5) Use of hydrogen as a secondary fuel in a diesel engine, characterised in that said hydrogen is introduced to said engine by addition to a diesel fuel line directly prior to a fuel pump.

6) The use of claim 5 for the reduction of pollution from said diesel engine.

7) The use of claim 6 wherein said pollution comprises carbon dioxide.

8) The use of any of claims 5 to 7 wherein said hydrogen is introduced into said diesel fuel at a calorific ratio of diesel fuel: hydrogen of 99:1 to 1:99, preferably 90:10 to 10:90.

9) The use as claimed in claim 8 wherein hydrogen is introduced into said diesel fuel at a calorific ratio which is inversely related to the required torque of the engine.

10) A diesel engine configured to accept an input of hydrogen gas into at least one diesel fuel feed line, characterised in that said hydrogen is introduced to said diesel fuel in a fuel feed line, directly prior to a fuel pump.

11) The diesel engine of claim 10 having an engine management system configured to reduce pollution from said engine by the introduction of hydrogen into diesel fuel in a fuel feed line, directly prior to a fuel pump.