GB2041526A

GB2041526A - Measuring fuel consumption

Info

Publication number: GB2041526A
Application number: GB7932644A
Authority: GB
Original assignee: DOORNES BEDRIJFSWAGEN FAB
Current assignee: DOORNES BEDRIJFSWAGEN FAB
Priority date: 1979-01-26
Filing date: 1979-09-20
Publication date: 1980-09-10
Also published as: DE2928375A1; NL7900635A; FR2447464A1; FR2447464B1

Abstract

A device for measuring the fuel consumption of internal combustion engines, particularly diesel engines, having a fuel injection system, comprises an auxiliary fuel tank 1 from which fuel feed and return lines 2, 3 lead to the engine (not shown), and which is connected to the main fuel tank 12 by a fuel line 7 incorporating a volume meter 8, there being a filter device 9 in this line, and the filter device 9 is connected at its top by inlet and return lines 13, 11 to the fuel tank 12, there being a pump 14 which is of the continuously operating type in the inlet line 13 and there being a non-return valve 10 in the return line 11 and a level control device 5 on the top of the auxiliary fuel tank 1. Air is vented by a vent 6. <IMAGE>

Description

SPECIFICATION Device for measuring the engine fuel consumption The present invention relates to a device for measuring the fuel volume which is consumed by a combustion engine, especially a diesel engine with a fuel injection system provided with a fuel feed and return line, of a vessel or vehicle containing a fuel supply tank.

It is desirable to measure the fuel consumption of a combustion engine as accurately as possible, and this for the following reasons.

The continuous raise of fuel costs and the danger of an increasing deficiency necessitate a useful control of the consumption. If the measurement is accurate, the measure appa ratus can contribute to the development to economize the consumption and the control of a good operation of the engine. By means of a measure apparatus which is placed on a power source, working with liquid fuel, with injection system the owner thereof can control the issued fuel receipts and the costs of transport can be controlled and malversations by the personnel can be avoided. Furthermore a comparison is possible of the fuel consumption of various combustion engines. If the measure apparatus is used in vehicles for international transport it is possible on the basis of the consumption registration to meet the legally admitted quantity to be imported when passing the frontier.If used in road vehicles, said measure apparatus will give the driver and owner of the vehicle a constant picture of the fuel composition.

Measuring the fuel consumption can be done in two ways, namely by weight and by volume.

Measuring the weight is normally done in a laboratory to determine the specific fuel consumption. Said measurement is, however, less suitable for a consumption measurement in the event of strongly varying engine loads and is not suitable as a metering device for vehicles and vessels.

In vehicles a measurement of the volume is often done so as to know the fuel consumption per time, distance or speed under often strongly varying operational conditions. In --practice the measurement always involved practical problems with respect to the continu ity of the measurement, the influence of the movements of the vehicle, loss of output, and inaccurate measurement. -.~ The temperature of the fuel in the return line is higher than that of the fuel in the supply tank. In order not to unfavourably affect the engine efficiency, the fuel fed to the engine must not or hardly not differ from the temperature of the ambient air. Therefore the fuel in the return line must not be returned directly to the engine but via the fuel tank or a heat exchanger.

The feed and return line may contain air and vapour bubbles, caused by underpressure, raise in temperature and/or leakage of pipe and tube connections. The consequence hereof is an inaccurate consumption measurement.

In known fuel volume measuring systems of combustion engines, containing a fuel injection system which is provided as such with a return line for the fuel, a drip line, and a desaeration line, systems are known containing a passage meter in the feed line and a system which contains a meter in the feed and return line.

In practice it appears that with the system with one meter, notwithstanding provisions to prevent the development of vapour bubbles by cooling and overpressure, the effect tended to is not or insufficiently achieved, whereas the system with two meters shows at least the disadvantage that the measurement inaccuracy is doubled.

If one meter is placed in the fuel line system, one should take care of the fact that no fuel can come in the supply tank through the return line. Then said return line has to be connected to the feed line behind the meter.

The temperature of the returned fuel is, however, considerably higher than the fuel in the supply tank. Normally said returned fuel is cooled in the supply tank. When the heated fuel is injected into the engine the output decreases, as the injection is volumetrically constant, but at a higher temperature the density of the fuel is less. Moreover gas bubbles are developed in the returned fuel of higher temperature, so that the effect of a smaller engine output is even increased.

If two passage flow meters are used the problems which are developed when achieving an accurate measurement of the fuel consumption are neither solved. When placing the one meter in the feed line and the other meter in the return line the difference of the measured quantity of fuel does not provide an accurate value for the fuel consumption. In the first place the measurement inaccuracy is doubled and in the second place it has the disadvantage that with the meter in the return line fuel of a higher temperature is measured than that of the fuel fed by the injection pump.

The present invention tends to provide a simple device to measure the consumption of liquid fuel for a combustion engine, with which the above mentioned disadvantage re abolished, and with which a measurement without failures of said consumption is achieved without unfavourably influencing the temperature and the pressure of the fuel fed to the engine, and consequently the engine efficiency.

For that purpose the present invention is characterized in that in the fuel injection system an auxiliary tank is placed into which the fuel feed and return line debouch, said auxiliary tank communicating at its top, by means of a fuel feed line with volume meter, via a feed pump with the fuel supply tank, said feed pump being embodied and arranged such that the auxiliary vessel is always filled with filtered fuel, without vapour and air, from the fuel supply tank.

No air and gas bubbles and pollutions appear in the measure line, and the temperature of the fuel to the meter is equal to that of the supply tank.

The invention also enables an accurate measurement on slopes. If the meter would show a disturbance, fuel is fed to the engine all the same. Optionally the lines of the fuel injection system can be re-coupled such that they communicate with the supply tank. The invention can be used for any type of consumption units. No increase of the temperature, other than the normal increase, of the fuel takes place. In the event of diesel engines a normal flow of the fuel pump galery is maintained.

Pre-filtering the fuel prevents a pollution or obstruction of the meter. Fore measurements with a very high accuracy the auxiliary tank can be provided with an apparatus, which takes care of the maintenance of a constant temperature of the fuel. The difference in volume caused by heating during use or the ambient temperature is accurately registered as yet after cooling when switching-on the measuring apparatus.

The present device can be placed at any required location. The auxiliary tank is embodied such, that no hollow spaces can be filled by air or foam bubbles. The level control device placed within the auxiliary tank, for which control device any system can be used like a float or membrane system, with the desaeration placed over it, will take care of a constant quantity of fuel in the auxiliary tank.

By refiling the fuel supply tank the accurate operation of the auxiliary tank can be checked. Stopping the fuel from being fed to the auxiliary tank does not influence the behaviour of the engine at all. When completely switching off the meter, the connections of the auxiliary tank to the fuel injection system can simply be connected to the fuel supply tank. The contents of the auxiliary tank takes care of the fact that the engine cannot be made inactive if the above situation occurs.

The meter can either indicate volume units, or be connected to an electronic apparatus which gives a signal.

The invention will now be elucidated on the basis of the drawing, by way of example, in which: Figure 1 shows schematically the arrangement of the measuring device according to the invention.

The device according to the invention consists of an auxiliary tank 1 of sufficient content, or provided with a cooling intallation, to keep the temperature of the fuel within acceptable limits, placed in a fuel injection system, known per se, of a diesel engine (not shown).

The fuel injection system contains a line 2 to feed fuel from the auxiliary tank to the fuel pump of the diesel engine, and a line 3 to return fuel from the fuel pump to the auxiliary tank. At its top the auxiliary tank is provided with a chamber 4 with an arbitrary level control device 5 and a desaerator 6, a fuel feed line 7 being connected to said chamber, and adapted to be closed by the level control device. In the fuel feed line 7 a volume meter 8 is placed, which may be of any known type.

The fuel feed line debouches into the bottom of a filter device 9. The filter device 9 is provided at its top with an overpressure valve 10 to which a return line 11 is connected, which debouches into a fuel supply tank 1 2.

The supply tank 1 2 is connected via an inlet line 13 with a feed pump 14, to the upper space of the filter device 9. The pump can also be an electrically controllable pump, the control being dependent upon the pressure.

Claims

1. A device for measuring the volume of fuel which is consumed by a combustion engine of a vessel or vehicle containing a fuel supply tank and a fuel feed and return line wherein an auxiliary tank is provided into which the fuel feed and return lines lead, said auxiliary tank communicating at its top, by means of a further fuel feed line fitted with a volume meter and via a feed pump with the fuel supply tank, said feed pump being embodied and arranged such that the auxiliary tank is always filled with filtered fuel, without vapour and air, from the fuel supply tank.

2. A device according to claim 1 wherein at its top, the auxiliary tank is provided with a chamber with a level control device and a desaerator, the further fuel feed line being connected to said chamber and adapted to be closed by the level control device.

3. A device according to claim 1 or 2 wherein the feed pump is a continuously operating pump with a return line.

4. A device according to claim 1, 2 or 3 wherein the fuel pump is an electrically controllable pump.

5. A device according to claim 3 wherein the further feed line is connected to a downstream side of a filter device and wherein a fuel inlet line in which the continuously operating feed pump is located is connected between the supply tank and the top of the filter device, there also being a return line provided with a non-return valve therein extending between the supply tank and the top of the filter device.

6. A device substantially as described herein and/or as shown in the drawing.

7. A fuel feed system for a combustion engine or the like provided with a device substantially as indicated in the specification and/or as shown in the drawing.