GB2433265A

GB2433265A - Low toxicity fuel

Info

Publication number: GB2433265A
Application number: GB0525620A
Authority: GB
Inventors: Derek Lowe
Original assignee: Individual
Current assignee: Individual
Priority date: 2005-12-16
Filing date: 2005-12-16
Publication date: 2007-06-20
Also published as: GB0525620D0

Abstract

A low toxicity fuel for four-stroke engines includes 80-99% ethanol and 1-20% volatile hydrocarbon fractions that are soluble in ethanol. The volatile hydrocarbon fractions may include pentane, iso-pentane, butane, iso-butane, propane and combinations thereof. The ethanol and volatile hydrocarbon fractions may be blended for high octane and low toxicity. The volatile hydrocarbon fractions may be selected for volatility, flame rate, octane rating and low toxicity. The fuel may include 1-20% water and/or one or more additives such as corrosion inhibitors, combustion enhancers, solubility aids and cold starting promoters.

Description

LOW TOXICITY FOUR-STROKE FUEL

The present invention relates to a low toxicity fuel for four-stroke internal combustion engines and in particular, but not exclusively, for high performance competition engines.

A purpose of this invention is to provide a novel approach to reducing the toxicity of the emissions from four-stroke competition engines. The objective is to provide a fuel for use with four-stroke engines in applications where very high power is the prime objective. Such engines are operated rich of stoichiometric, often with significant valve overlap. This is done to maximise the power output, but in those applications where catalytic after treatment is considered inappropriate, high emission levels of the unburned fuel will be present in the exhaust gases. These conditions are also likely to create significant emissions of particulates.

Such conditions are commonplace with competition four-stroke engines. Typically such engines run at air-fuel ratios of around 12.5:1 when using gasoline: the enclosed graph (Figure 1) emphasises the levels of exhaust toxins. A further objective is to provide a fuel that has low toxicity to minimise the health risks associated with the handling of the fuel within the competition and recreational sectors.

The principles underlying this "low toxicity four-stroke fuel" are to provide innovative, practical and environmental solutions to unacceptably high emission levels of unburned hydrocarbon emissions, which are associated with high power four-stroke engines.

According to the present invention there is provided a low toxicity fuel for four-stroke engines, wherein the fuel includes 80-99% ethanol and 1-20% volatile hydrocarbon fractions that are soluble in ethanol. Preferably, the fuel includes 85-95% ethanol and 5-15% volatile hydrocarbon fractions.

Advantageously, the ethanol and volatile hydrocarbon fractions are blended for high octane and low toxicity.

Advantageously, the volatile hydrocarbon fractions are selected from the group comprising pentane, iso-pentane, butane, iso-butane, propane and combinations thereof. Preferably, the volatile hydrocarbon fractions include 3-13% pentane or iso-pentane, and/or 0-2% butane or iso-butane, and/or 0-2% propane.

Advantageously, the fuel component includes one or more additives selected from a range that includes corrosion inhibitors, combustion enhancers, solubility aids and cold starting promoters.

Optionally, the fuel component includes 1-20% water, preferably 3-10% water.

The key to this novel approach to the problem of four-stroke competition engine emissions is provided by ethanol. An initial formulation to address this four-stroke emission problem is made up with from 1% to 20% of appropriate hydrocarbons: these are selected for low toxicity, good volatility, high flame rate and high octane ratings. These hydrocarbons are likely to originate from the "front-end fractions" of the refining process. They can include the heavier hydrocarbon gases and the lighter hydrocarbon liquids. These specific hydrocarbon components will act as a cold starting aid. The composition of this hydrocarbon fraction may be varied depending on the application and the ambient temperature within a particular market.

These hydrocarbon components must also be selected for solubility in ethanol. They can include hydrocarbons that are gaseous at normal temperatures such as propane, butane and iso-butane, and those that are liquid such as pentane and iso-pentane. Other hydrocarbons may also prove appropriate to meet these requirements, the emphasis being towards low toxicity and good solubility. The remainder of the fuel is ethanol: this fuel is usually rated at 108 octane RON (although some sources quote ethanol octane ratings of 112-120 RON).

To this blend we can optionally add water up to 10% in order to achieve further suppression of the oxides of nitrogen (NOx) and to avoid spark knock. Tests have indicated that water is soluble in ethanol/hydrocarbon fuel blends. The flame temperature of ethanol is lower than with gasoline and the flame luminosity is also less: this will help suppress the formation of NOx. The use of ethanol can be expected to further reduce NOx emissions. Adding water may well limit the formation of NOx further but the trade-off is likely to be an increase in the 1.. - ____ risk of corrosion to engine and fuel systems components and the requirement for greater fuel tank capacity.

It is anticipated that in the first instance a four-stroke ethanol/hydrocarbon competition fuel will be created. This will be designed and optimised for four-stroke competition engines.

Each of the components and additives is selected to minimise the toxic risks associated with fuel handling and to minimise the toxicity of the exhaust emissions. Each fuel component is selected to ensure solubility and compatibility with ethanol. Ethanol is relied on primarily to provide clean burn, the required high octane rating and lower levels of toxins in the unburned fuel in the engine's exhaust gases. The ethanol based fuel needs to be blended with cold starting combustion enhancers, whilst aiming to ensure that the four-stroke emissions are of low toxicity and low in particulates.

Appropriate hydrocarbons remain useful to improve cold starting characteristics, but they are only required in small proportions. The right hydrocarbons are required for this clean fuel technology and there is a need to select hydrocarbon fractions with low toxicity, high octane rating and appropriate volatility as the key blending components.

With conventional gasoline fuels, the main exhaust gases are carbon-dioxide, nitrogen and water vapour. These gases are relatively benign. However the worst pollutants in the engine's exhaust are those products of incomplete combustion, namely carbon-monoxide and a range of unburned hydrocarbons, including particulates. The oxides of nitrogen (NOx) are the result of atmospheric nitrogen and oxygen, which combine under conditions of high temperature and pressure. The emissions of NOx are generally high with four-stroke engines. The objective here is to reduce the NOx emissions and particulates by the use of this fuel package.

Combustion chamber design with high speed competition four-stroke engines has been influenced by over square bore: stroke ratios and this leads to "disc-like" combustion chambers where the high surface area tends to cause combustion "quenching" resulting in increased levels of unburned hydrocarbons and carbon monoxide. Formation ofNOx can be minimised by a reduction in the peak combustion temperatures, and for this purpose a fuel that can absorb water may prove beneficial. Adding water has the disadvantage that it will increase the risk of corrosion, but anti-corrosion additives should serve to minimise the problem. Materials used in the engine fuel system should also be selected to reduce the corrosion problem.

A solution that relies on alternative fuels is proposed as an answer to the four-stroke competition engine emission problems. It will also reduce the health risks associated with handling highly toxic fuels. The initial blends proposed here provide the opportunity to retain a liquid fuel and to replace the toxic unburned fuels which are emitted in exhaust gases of four-stroke engines. Instead, the components of the fuel have been selected for their benign nature, whilst providing the opportunity to maintain and improve octane rating and charge density.

This will allow competition engines to operate without the use of such toxic components as toluene, which is used in some competition fuels at a concentration exceeding 20%.

A range of additives is required to address various issues such as corrosion, solubility, cold starting and a number of other undesirable characteristics. It may also prove beneficial to improve the luminosity of the flame with an appropriate marker-tracer. The appropriate additives will be incorporated into the fuel.

This fuel will be "designed" to be four-stroke compatible: there is an emerging market for a high octane and benign fuel that can be used in a wide range of competition four-stroke engines. These engines are often run rich of stoichiometric and with significant valve overlap in the pursuit of maximum power and performance. This results in very high emission levels linked to the unburned fuel. With these proposals these emissions become much less toxic.

Ethanol, as a result of its high latent heat of evaporation, creates a significant reduction of the charge temperature compared with gasoline. This helps to reduce peak temperatures and NOx formation. The high latent heat of evaporation is invaluable to reduce charge temperature and to increase the charge density. The result is an increase in power output. The fuel has a higher octane rating than gasoline fuels currently mandated in various forms of motor sport. This will permit the use of increased compression ratios leading to improved efficiency.

Four-stroke engines with carburettors can be sensitive to "transient spark knock", which is caused by "light end" octane deficiency. The high octane rating available with the ethanol provides an opportunity to avoid this undesirable condition. However, the hydrocarbon fractions also need to be selected carefully to avoid similar "light end" octane deficiency.

The internal components of the four-stroke engine will be exposed to a lower incoming charge temperature with the ethanol based fuellair mixture and this will assist in piston cooling. There should also be similar benefits by improved cooling of the cylinder bore. This should be advantageous for improving engine durability.

Lower maximum and mean flame temperatures have been reported with ethanol fuel. This will help in NOx reduction and will reduce the heat load on the piston. Lower coolant temperatures can be expected and this is beneficial for durability and for the avoidance of "spark knock".

The present invention thus provides a high octane but significantly more benign fuel for four-stroke motor sport than conventional gasoline-based fuels.

According to a preferred embodiment, the invention provides a blend of fuels and additives for use in four-stroke engines. This fuel has been devised in order to reduce the variety of risks posed to human health and to the environment from the exhaust emissions of such engines.

These engines are currently operated on gasoline fuels.

This fuel with or without the addition of water can be used for reducing the toxicity of the exhaust emissions, including NOx and particulates, from "competition" four-stroke engines.

It also reduces the health risks associated with the handling of such fuels within the competition and recreational sectors for various four-stroke engine applications.

Various embodiments of the invention will now be described with reference to the following

examples.

EXAMPLE 1

Compound Percentage Ethanol 90% Iso-pentane 10% Plus fuel additive package 100% fuel element

EXAMPLE 2

Compound Percentage Ethanol 90% Butane or iso-butane 02% Iso-pentane or pentane 08% Plus fuel additive package 100% fuel element

EXAMPLE 3

Compound Percentage Ethanol 95% Propane 01% Butane or iso-butane 01% Iso-pentane 03% Plus fuel additive package 100% fuel element

EXAMPLE 4

Compound Percentage io Ethanol 93% Propane 01% Butane or iso-butane 02% Iso-pentane 04% Plus fuel additive package 100% fuel element EXAMPLES -For lower NOx Compound Percentage Ethanol 85% Water 06% Butane or iso-butane 02% Iso-pentane or pentane 07% Plus fuel additive package 100% fuel element EXAMPLE 6 -Four-stroke, low toxicity competition fuel Compound Percentage Ethanol 85% Butane or iso-butane 02% Iso-pentane 13% Plus fuel additive package 100% fuel element In summary, the various advantages provided by the invention are as follows: * unburned fuel in the exhaust is non-toxic and biodegradable; * high octane (RON 108) allows increased compression ratio, increased power and improved efficiency; * reduced combustion temperature reduces emissions of NOx; * reduced formation of particulates; 1..) -- * increased latent heat of evaporation and reduction in charge temperature: this increases the charge density and increases power output; * lower charge temperature reduces the temperature of the piston and cylinder bore, improving engine durability: this is particularly useful on air-cooled engines; * much reduced toxicity in fuel handling; * retains simplicity and the advantage of the low cost carburettor; requires only minor changes to be made to the engine technology; and * can use renewable bio-fuels.

Claims

CLAIMS

1. A low toxicity fuel for four-stroke engines, wherein the fuel includes 80-99% ethanol and 1-20% volatile hydrocarbon fractions that are soluble in ethanol.

2. A fuel according to claim 1, wherein the fuel includes 85-95% ethanol and 5-15% volatile hydrocarbon fractions.

3. A fuel according to claim 1 or claim 2, wherein the ethanol and volatile hydrocarbon fractions are blended for high octane and low toxicity.

4. A fuel according to any one of the preceding claims, wherein the volatile hydrocarbon fractions are selected from the group comprising pentane, iso-pentane, butane, iso-butane, propane and combinations thereof.

5. A fuel according to any one of the preceding claims, wherein the volatile hydrocarbon fractions include 3-13% pentane or iso-pentane.

6. A fuel according to any one of the preceding claims, wherein the volatile hydrocarbon fractions include 0-2% butane or iso-butane.

7. A fuel according to any one of the preceding claims, wherein the volatile hydrocarbon fractions include 0-2% propane.

8. A fuel according to any one of the preceding claims, wherein the volatile hydrocarbon fractions are selected for volatility, flame rate, octane rating and low toxicity.

9. A fuel according to any one of the preceding claims, wherein the fuel component includes one or more additives selected from a range that includes corrosion inhibitors, combustion enhancers, solubility aids and cold starting promoters.

10. A fuel according to any one of the preceding claims, wherein the fuel component includes 1-20% water.

11. A fuel according to any one of the preceding claims, wherein the fuel component includes 3-10% water.