GB2457343A

GB2457343A - I.c. engine fuel system with reserve tank, eg for racing vehicles

Info

Publication number: GB2457343A
Application number: GB0802914A
Authority: GB
Inventors: Derek Lowe
Original assignee: Individual
Current assignee: Individual
Priority date: 2008-02-18
Filing date: 2008-02-18
Publication date: 2009-08-19
Also published as: GB0802914D0

Abstract

A fuel system for an internal combustion engine 6, eg of a racing vehicle, includes a main fuel tank 8, a reserve fuel tank 10, a fuel control valve 16 that is switchable to select whether the fuel is drawn from the main tank or the reserve tank, and an input device 20 for controlling operation of the valve. The main tank 8 contains a first fuel and the reserve tank 10 contains a second fuel that has a different energy density from the first fuel. In motor racing, the reserve tank may be filled with fuel of lower energy density than that of the main tank, eg by adding ethanol or methanol to gasoline. The input device 20 may be a driver-operated switch or remotely controlled, eg by a racing team technician or race official. A vehicle that uses its fixed allocation of main fuel for the race is thus disadvantaged by reduced peak power, speed and acceleration. The use of reserve fuel may be indicated, eg by a light visible to competitors, spectators and officials and penalty points may be applied.

Description

I

FUEL SYSTEM

The present invention relates to a fuel system for internal combustion engines. In particular, but not exclusively, it relates to a fuel system for use in racing vehicles.

It has been suggested that motor racing, including Formula One (F 1), should have a focus on energy efficiency. Motorsport is now seeking to raise its "green" profile and a focus on energy efficiency is crucial to that process. This invention seeks to provide a simple mechanism to drive automotive technologies in the right direction.

Throughout motorsport today power is limited by regulations which control the supply of air. This may be achieved by a limit on the engine's swept volume and a limit on the number of cylinders, or it may be achieved by similar measures plus some additional limit on peak engine rotational speed (rpm). Power limitation can also be achieved by the use of air restrictors: these effectively limit the air supply into the inlet manifold. Limiting air supply effectively places a limit on the amount of fuel that can be burned and this in turn has the effect of limiting the peak power. **S**

*S.. S : In cases where supercharged or turbocharged engines are permitted by the regulations, as in * **.

the 24-hour Le Mans endurance race, then various combinations of engine capacity, air S. .**.

* : restrictor diameter and boost pressure limitations are also applied. Today throughout *.* motorsport some limit to air supply is applied. Even within F 1 inlet airflow is effectively :: 20 limited, by a limit on engine capacity and a limitation on the number of cylinders. In Fl the *.

:"rj peak rpm is now constrained by electronic means.

Air supply limitations have serious shortcomings. There is little merit in carrying excess * : fuel in any form of motorsport competition as this serves to increase the vehicle's weight. * ***

* ** However, whenever air supply is limited and there are no limitations on the supply of fuel the only route to achieve maximum power is to ensure that the limited supply of oxygen in *:. the air is fully utilised. In short, excessive fuelling takes place and air-fuel ratios significantly richer than stoichiometric are frequently used. There is also an opportunity to **.

: : : : use excess fuel for charge cooling: this reduces the risk of "spark knock" and it also helps to reduce charge temperature thereby increasing charge density. This also serves to improve the engin&s volumetric efficiency and increase the power output of the engine.

Sadly, the result of this specific approach is that motorsport often discharges substantial emissions of unburned hydrocarbon fuel and carbon-monoxide, both of which are toxic.

This leaves motorsport vulnerable to action by health and safety officials and by environmental groups. Such emissions could easily generate a negative attitude within the population and this could impact upon spectator involvement with motorsport.

There is however another problem with this approach, in that the volume car industry has to reduce the discharge of CO2 from production cars. The weight of CO2 discharged per hour is over three times the weight of the fuel burnt each hour. In the case of liquid petroleum fuels this equates to around 241b weight of CO2 per gallon of fuel consumed. Moreover, increased fuel prices are changing customer purchasing patterns and now fuel efficiency is being driven by both economics and the environment. Therefore mainstream car makers are increasingly focused on minimising fuel burn, while the entire motorsport industry has gone off in virtually the opposite direction as a result of the application of regulations which limit the supply of air. ** S.

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:: No mention has been made so far as to appropriate levels of power for various motorsport applications. However, this can be readily determined once the specification of the racecar *. * * *

* * is defined and an appropriate level of performance has been prescribed. Efficient power *1. S..

* 20 units are turbocharged and run at lower rpm and higher boost levels; this is also helpful in S...

:::: reducing engine friction and engine wear. These are useful steps for improving engine durability and this provides an opportunity to reduce the cost of race engine overhauls.

* Peak power can be limited by a system that limits peak fuel flow. However this will only : : * serve to limit peak power and exhaust emissions at peak power. It will also only serve to drive forward efficiency at peak power. The rest of the time the engine can be operated "rich" of stoichiometric in the interests of maximising power at all other points on the "engine operating map". Today, the correct goal is to maximise engine efficiency across all useable power settings. This demands a limit on the total energy (or fuel) available to the S...

: : : competition car.

What is needed in order to move the motorsport industry into line with the technological trajectory of the automotive industry is a system that will constrain fuel supply instead of constraining the supply of air. These technologies need to be created as a priority and made available for application by the motorsport regulators. Fuel can be constrained either by flow rate or by quantity: however, the control of the quantity of fuel provides the much more accessible solution.

As the intention is to drive efficiency forward via motorsport, we should endeavour to ensure efficiency is improved across the entire operational range from idling to 100% power. To achieve this, a limitation on absolute fuel quantity has considerable merit. Regulators can easily determine the quantity of fuel required per lap for each particular circuit and for each series of racing car. Race teams can readily modify fuel consumption of any race car, as fuel-air mixture ratios, down-force and drag can be changed and these have an impact on lap times and on fuel consumption.

Race teams can modify air-fuel ratios, peak rpm and gearing in order to match the circuit and other variables (i.e. temperature, air density, wind etc) to the fuel quantity allocated. In ::;:. short, only incompetence or unusual conditions should result in a car running out of fuel *..* S ::: before the finishing line. However, the "goal posts" of motorsport will have been changed, * . *. ** so that the most fuel efficient power-train and car should be well positioned to win, all other things being equal. 5.

* 20 The eventuality of running out of fuel provides new opportunities if we adopt some * ::h17 innovative approach to this undesirable consequence of limiting fuel quantity or the capacity :?: of the tank. A reserve fuel tank system has proved its value on many aircraft over the years.

In motorsport it provides an important asset towards future fuel control regulations within * : : motor racing. The key to its innovative use in motorsport however depends on the nature ** 25 of the fuel placed in the reserve tank: this is the key innovative step to these specific * :* proposals to provide a new method for the regulation of power motorsport.

According to one aspect of the invention, there is provided a fuel system for an internal combustion engine, including a main fuel tank, a reserve fuel tank, a fuel control valve that *..* is switchable to select whether the fuel is drawn from the main tank or the reserve tank, and an input device for controlling operation of the valve, wherein the main tank contains a first fuel and the reserve tank contains a second fuel that has a different energy density from the first fuel.

Advantageously, the first fuel has a higher energy density. For example, the second fuel energy density may be in the range 70-95% of the first fuel energy density, and is preferably approximately 85% of the first fuel energy density.

The main fuel tank may have a larger capacity than the reserve tank.

The input device may be operable by the driver, or remotely by a third party, or automatically when the main fuel tank is substantially empty.

The fuel system may include an indicator device to indicate when the fuel control valve is switched to draw fuel from the reserve tank.

According to another aspect of the invention, there is provided a method of operating an internal combustion engine, in which fuel is supplied to the engine alternatively from a main fuel tank containing a first fuel and reserve fuel tank containing a second fuel that has a :::r; 15 different energy density from the first fuel.

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* 50 SS Advantageously, fuel is drawn primarily from the main fuel tank and is drawn from the reserve fuel tank when the main fuel tank is substantially exhausted. * *..

* The fuel supplied to the engine may be selected by the driver, or remotely by a third party, or automatically. An indicator device may be activated when fuel is supplied to the engine *** from the reserve fuel tank.

According to a preferred embodiment of the invention, the car's main fuel tank(s) are filled * *.* * with a fuel which for the sake of simplicity we will regard as having an energy content per * S.* * " litre of 100%. However, the reserve fuel tank is filled with fuel which has been blended to * have an energy content per litre of say 85%. The addition of ethanol or methanol to gasoline *:. 25 would appear to address these requirements. We will thereby have created a significant reduction in peak power for any car which has used its race fuel allocation and then starts S...

to use the reserve fuel through the same fuel injectors or jets. Moreover it seems we may well have introduced a significant amount of overtaking in the closing laps thereby increasing the entertainment value of the racing spectacle. The reserve fuel supply can also be used by cars until racing actually starts when fuel from the main fuel tank(s) will be used.

In fact the change over of fuel supply from the reserve to the main supply can be initiated electronically by the race officials at the commencement of the race.

A car that uses the allocated limit of energy before the end of the race is disadvantaged by a reduction in peak power, speed and acceleration, providing the regulations specify that no changes are permitted between the fuel injection rate used with the normal and the reserve fuel supply.

However, we still need to create a "level playing field" to cater for a car which still wins the race, but has used reserve fuel for say the last two laps. The cars can be fitted with a reserve fuel indicator light, visible to competitors, spectators and to race officials. If the reserve fuel is used prior to the finish, this light will illuminate, and some form of penalty points are then applied to the competitor.

If for example points are allocated on the basis of: 1 place 10 pts, 2' place 8 pts, 3rd place *5S* :r; 6 pts, place 5pts 8th place 1 Pt, then perhaps a five point penalty would be an * S..

:,: appropriate deterrent to the use of the reserve fuel. In any case engines and cars can be "trimmed" during the race to ensure that only the "main fuel" with 100% energy" is used.

. .*** . .5 * I :: An embodiment of the invention will now be described by way of example, with reference to the accompanying drawing, wherein: S. * * I.. S...

Figure 1 is a schematic representation of a fuel system for an internal combustion engine.

Figure 1 shows a fuel system that is indicated generally by the reference numeral 4, for an : : internal combustion engine 6. The fuel system and the engine may for example be components of a racing car. I. **

The fuel system 4 includes a main fuel tank or tanks 8 and a reserve fuel tank 10. The S..

reserve tank 10 will generally have a much smaller capacity than the main tank or tanks 8. S... * * **.I I. I

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The main tank 8 and the reserve tank 10 are each connected through a fuel line 12,14 respectively to a fuel control valve 16, which is in turn connected to the engine 6 through another fuel line 18. The fuel control valve 16 is switchable to deliver fuel to the engine 6 from either the main tank 8 or the reserve tank 10. An input device 20 is connected to the fuel control valve and is operable to control switching of the valve. The input device 20 may for example be a switch that can be operated by the driver, or it may include a remote control system, allowing operation of the valve 16 to be controlled by a third party (for example a racing team technician or an official of the racing authorities). Optionally, the fuel control valve may also be connected to an indicator device 22 for indicating the operational state of the valve. The indicator device 22 may for example be a display that is visible to the driver, or an indicator such as a light mounted on the vehicle so that it can be seen by spectators.

The indicator device may also include a signalling device for sending a signal to a third party to indicate the operational state of the switch. The third party may for example be a technician of the race team, a race official or the spectators.

In use, the main tank 8 and the reserve tank 10 contain fuels having different energy content per unit of volume. For example, the main tank 8 may contain approved competition petrol :; (gasoline), whereas the reserve tank contains a mixture of this petrol and ethanol or methanol. In this case, the alcohol reduces the energy density of the fuel in the reserve tank, so that the energy content per litre is reduced by comparison with the undiluted petrol in the . ..S.

main tank 8. For example, the mixture may be such that the energy content per litre of the . S. * fuel in the reserve tank is only 85% of that in the main tank. S... S * S

During racing, the engine will be powered primarily by fuel from the main tank, owing to % * . * . . S * its higher energy density. Generally, the amount of fuel provided in the main tank will be designed to be sufficient to power the car for the entire duration of the race. The reserve fuel * is intended to be used only if the fuel in the main tank is exhausted before the race is **** * S finished. In this event, the driver or a remote third party operates the valve 16 so that it switches from the main tank 8 to the reserve tank 10. Alternatively, the switch may be *:. designed to operate automatically, when the fuel in the main tank is exhausted. When fuel from the reserve tank is being used, the power of the engine will be reduced owing to the S... * S 5.55 *5 S * . S S *S

lower energy content of the reserve fuel. This will cause the car to slow down, increasing the opportunity for trailing competitors to overtake.

If desired, the indicator device 22 can be used to indicate when fuel from the reserve tank is being used. Racing regulations may provide for a penalty to be imposed on the competitor in this event.

The fuel system is designed so that fuel is supplied at the same rate, regardless of whether the fuel is drawn from the main tank 8 or the reserve tank 10. This prevents the effect of the reduced energy content of the reserve fuel being negated by an increase in the rate of fuel delivery. * S..

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Claims

Claims 1. A fuel system for an internal combustion engine, including a main fuel tank, a reserve fuel tank, a fuel control valve that is switchable to select whether the fuel is drawn from the main tank or the reserve tank, and an input device for controlling operation of the valve, wherein the main tank contains a first fuel and the reserve tank contains a second fuel that has a different energy density from the first fuel.
2. A fuel system according to claim 1, in which the first fuel has a higher energy density.
3. A fuel system according to claim 2, in which the second fuel energy density is in the range 70-95% of the first fuel energy density.
4. A fuel system according to claim 3, in which the second fuel energy density is approximately 85% of the first fuel energy density.
5. A fuel system according to any one of the preceding claims, in which the main fuel **..tank has a larger capacity than the reserve tank.*5 *�.* S S. ** *S..
6. A fuel system according to any one of the preceding claims, in which the input %S s*S* I* device is operable by the driver. . *S
7. A fuel system according to any one of the preceding claims, in which the input *I S S 5 ::..: device is operable remotely by a third party. . *S. * S*
8. A fuel system according to any one of the preceding claims, in which the input device is operable automatically when the main fuel tank is substantially empty. .5.
9. A fuel system according to any one of the preceding claims, including an indicator device to indicate when the fuel control valve is switched to draw fuel from the reserve tank.S S..I .5. S... S. SS SIS IS
10. A method of operating an internal combustion engine, in which fuel is supplied to the engine alternatively from a main fuel tank containing a first fuel and reserve fuel tank containing a second fuel that has a different energy density from the first fuel.
11. A method according to claim 10, in which fuel is drawn primarily from the main fuel tank and is drawn from the reserve fuel tank when the main fuel tank is substantially exhausted.
12. A method according to claim 10 or claim 11, in which the first fuel has a higher energy density than the second fuel.
13. A method according to claim 12, in which the second fuel energy density is in the range 70-95% of the first fuel energy density.
14. A method according to claim 13, in which the second fuel energy density is approximately 85% of the first fuel energy density.
15. A method according to any one of claims 10 to 14, in which the fuel supplied to the engine is selected by the driver. S...S
16. A method according to any one of claims 10 to 15, in which the fuel supplied to the *S**** * engine is selected remotely by a third party. _. S.l** ..* S *
17. A method according to any one of claims 10 to 16, in which the fuel supplied to the engine is selected automatically.*... S
18. A method according to any one of claims 10 to 17, in which an indicator device is . * * *. activated when fuel is supplied to the engine from the reserve fuel tank. *S.. * S S *S I S... * S *..S I. * S S * *I S..I S... * S a..., S. S S S * *