GB2049914A

GB2049914A - Pre-warming fuel

Info

Publication number: GB2049914A
Application number: GB8009788A
Authority: GB
Original assignee: Individual
Current assignee: Individual
Priority date: 1979-05-30
Filing date: 1980-03-24
Publication date: 1980-12-31
Also published as: DE2921985A1; FR2458026A1; NL8001863A; FR2458026B3; SE8002260L

Abstract

Apparatus for the pre-warming of fuel which tends to gell at low temperatures comprises a heating block 1 insertable into the fuel supply line and having input and output connections (6) and (7) between which there is located a shallow gap- like fuel flow channel (5) the free cross-section of which is substantially the same as the free flow cross- section of the supply line into which the heating block is to be inserted. The heating block can conveniently be incorporated in a filter head and the shallow gap-like fuel flow channel is conveniently defined between the inner wall of a bore in the heating block and the outer wall of an electrical heating cartridge inserted into the bore. <IMAGE>

Description

SPECIFICATION Apparatus for the pre-warming of fuel The invention relates to an apparatus for the pre-warming of fuel which tends to gell at low temperatures and has particular reference to an arrangement in which the fuel is forwarded from a supply tank by means of a pump via connecting lines to a combustion chamber or burner.

It is known that fuel, for example diesel fuel, tends to gell at low temperatures such as occur during cold winters. As a consequence the starting of a vehicle which runs on diesel fuel can become impossible. Corresponding problems can also occur, by way of example, with heating apparatus equipped with oil burners which can then no longer be operated, in particular just at the time when they would be most needed by reason of low ambient temperatures.

In practice, and in particular for diesel vehicles, it is frequently attempted to reduce this problem by adding petrol or gasoline to the diesel fuel.

Quite apart from the fact that it is necessary to add the petrol before the fuel has gelled, this measure is associated with considerable danger for the engine and its user and does not thus represent an acceptable way of solving the problem which exists.

It has also already been attempted to provide the fuel supply tank with a heater so that the entire fuel supply can be raised to a temperature at which the danger of gelling is removed prior to operating the apparatus fed from the supply tank.

The practical application of this suggestion generally founders however because insufficient electrical energy is available in order to heat the entire fuel supply in the necessary manner not least as the required electrical energy must as a rule be drawn from a battery the ability of which to supply power is known to be additionally restricted at low temperatures.

It has finally also already been attempted to heat the fuel supply lines at least at certain regions by winding them with heating coils. These attempts also failed to produce a usable result because, after the fuel supply pump had been switched on for a short time, the filter in the fuel line blocked before the heating device could become truly effective.

The principle object underlying the present invention is to so further modify an apparatus of the kind initially named that problem-free and practically instantaneous operation of an apparatus fed with a fuel which tends to gell, in particular an oil burner or a motor, is possible at very low temperatures despite a low consumption of electrical energy.

This object is accomplished in accordance with the invention by a heating block insertable into a supply line the heating block having an input connection and an output connection and therebetween at least one shallow gap-like fuel flow channel the free flow cross-section of which is at least substantially the same as the free flow cross-section of the supply line into which it is to be connected.

By the use of a shallow gap-like fuel flow channel in a block which can be rapidly heated, the fuel, which can already be gelling, and which is emerging as a relatively thick jet from a tubular conduit is converted into a thin layer and is brought practically immediately to a temperature at which the tendency to further gelling is precluded so that the fuel leaving the heating block can neither block a subsequent filter nor be difficult to ignite in the subsequent combustion chamber or burner.

As the free flow cross-section of the shallow gap-like fuel flow channel is at least substantially the same as the free flow cross-section of the supply line into which the heating block is to be connected it is ensured that the flow channel in the heating block does not disturb the normal operation at normal temperatures at which no danger of gelling of the fuel exists. The arrangement, however, also ensures at low temperatures that the task on which the invention is based can be solved without problems by the transformation in the heating block of the jet of fuel from the supply line into a quickly warmable thin layer of fuel.

In accordance with a particularly advantageous embodiment of the invention the fuel flow channel in the heating block is constructed as a channel of annular cross-section. This channel of annular cross-section is defined on one side by the wall of a bore formed in the heating block and on the other side by the outer wall of a heating cartridge inserted into this bore.

This apparatus which is of particularly simple construction and which can thus be economically produced, has a high efficiency and can be inserted without problem at a suitable position in a fuel supply line. The use of the heating element or the heating cartridge as a boundary wall for the annular section gap ensures, on the one hand, extremely rapid, i.e. practically instantaneous operation of the arrangement and, on the other hand, a minimum consumption of electrical energy.

In the heating block, which is preferably of metal, there is usefully integrated a thermostat which controls (feed back controls) the feed to the heating cartridge so that the pre-warming apparatus is automatically set into operation when very low temperatures occur and is also taken out of operation when the danger of gelling of the fuel is no longer present, or when the heat originating from short time operation of the heating block or from the operation of the supplied apparatus is sufficient to preclude all danger of the fuel gelling.

The heating block is preferably inserted before the filter provided in the supply line. For this purpose the heating block can conveniently be constructed as a component of the removable metal cover of the filter housing and can thus be integrated with the filter. This brings the additional advantage that the filter, which also presents particularly critical problems when using fuels which gelt, can be additionally heated.

A preferred use of the apparatus of the present invention is its installation in an air heater, in particular an air heater of portable or movable construction, which operates with an oil burner.

Air heaters of this kind mustalso be capable of being started at low temperatures because they are frequently used on building sites and in the shells of buildings under construction where extremely low temperatures can occur. When using the apparatus in accordance with the invention in equipment of this kind it has been shown that no starting problems occur, even at very low temperatures and that the consumption of electrical energy is so low that this energy can also be supplied by a battery incorporated in the equipment.It has also been shown that the apparatus in accordance with the invention only needs to be in operation for a surprisingly short time, even at very low temperatures, because the fuel circulation between the supply and return flow lines, which lie alongside one another in the tank, and the pump ensures that the necessary increase in temperature in the supply tank propagates from the vicinity of the connection points into the remainder of the tank. I.e. that a partial supply of fuel which does not tend to gell and which ensures the trouble-free functioning of the equipment fed with the fuel is very rapidly created in that region of the tank from which the fuel is drawn.

A further advantageous application of the apparatus of the invention is its installation in machines and vehicles which are operated with diesel fuel. In this case also it is possible, with a surprisingly small expenditure of electrical energy drawn from the battery, to raise the temperature of the fuel supplied to the combustion chamber at once and to a sufficient level that problem free starting is possible even with fuels that are already gelling. The further operation of the motor after it has started is also assured without difficulty.

Embodiments of the invention will now be explained in further detail by way of example only and with reference to the following drawings in which are shown: Fig. 1 a schematic side view of a heating block in accordance with the invention in which the heating cartridge and the flow gap are represented in broken lines, Fig. 2 a sectional illustration along the line A-A of Fig. 1, Fig. 3 a sectional illustration taken on the line B-BofFig. 1, Fig. 4 a schematic sectional illustration of a heating block integrated in the cover of a filter housing in accordance with the invention, Fig. 5 a section of the cover of Fig. 4 extending through a central axis and, Fig. 6 a side view of the cover of Fig. 5.

Fig. 1 shows a block 1 consisting of metal which is provided with a bore 2 centrally formed from one end face and which is intended to receive a heating cartridge 3. This heating cartridge 3 is sealingly screw threaded in the block 1 by its fastening part 4.

The diameter of the bore 2 and the heating cartridge 3 are so chosen that an annular section gap 5 exists between the heating cartridge 3 and the wall of the bore 2. The gap 5 serves as the flow channel for the fuel which is supplied via an inlet bore 6 and leaves via an outlet bore 7. A thermostat 8 is usefully arranged on the outer wall of the block 1 and ensures that the heating cartridge 3 is switched on when a predeterminable low temperature is reached and that the heating cartridge 3 is switched off when the temperature once more exceeds this critical lower value.

The sectional illustration of Fig. 2 enables the supply bore 6 and the discharge bore 7 for the fuel to be recognized and shows that the fuel, which is supplied via the bore 6 and which can already be gelling, is led directly against the wall of the heating cartridge 3 and is at once converted into a thin layer extending over the entire annular gap 5.

This thin fuel layer is in direct contact with the outer wail of the heating cartridge 3 and is thus warmed to a sufficient degree that any tendency of the fuel to gell disappears.

The thickness of the annular gap, i.e. the radial height of the annular gap in the illustrated embodiment lies as a rule between 0.1 mm and 2 mm and preferably between 0.1 mm and 1 mm and the range of variation can also originate from a conical run of the annular gap i.e. the gap can taper.

It is also possible for the purpose of providing specified gap widths to construct the bore 2 to be somewhat large and to insert corresponding fitting sleeves which, if desired, can also be of synthetic material for insulation purposes.

The sectional illustration of Fig. 3 shows the annular gap 5 formed by cooperation of the bore and the heating cartridge 3. The heating wires provided in the heating cartridge 3 can also be recognized. The fuel discharge opening 7 is indicated in broken lines.

The heating cartridge 3 can in principle be supplied from any desired electrical energy source, it has, however, been shown that the energy supplied from a battery readily suffices in order to ensure the desired operation.

A preferred embodiment of the invention is illustrated in Fig. 4 and in this embodiment the heating block 1 is integrated in the cover of a filter which is referred to with the general reference numeral 1 0. Inside the filter glass 11 there is located a customary filter cartridge 12 and filter glass 11 can be secured by threads to the filter head or filter cover by means of a collar nut 1 3 so that the filter glass 1 can be removed for the purpose of changing the cartridge.

The block 1 which is integrated into the filter cover once more has a bore for receiving a heating cartridge 3 so that a shallow annular gap 5 is formed between the heating cartridge 3 and the wall of the heating block. This annular gap has a conical run because the recess which receives the heating body 3 is lightly conical, the heating cartridge is, however, cylindrical. In this manner the gap width tapers from approximately 1 mm to 0,1 mm which has advantageous effects on the practical operation of the total arrangement.

The supply bore is illustrated at 6 and the discharge bore once more has the reference numeral 7. The centrally disposed fuel discharge connection from the filter is illustrated at 14.

The sectional view of Fig. 5 allows the layout of the filter cover or filter head 1 5 to be recognized in detail and shows the compact unification of ail the components required for pre-warming of the fuel on one half of the filter head. To the side there is provided a reception region 1 6 for a thermostat and a fuse and also for the connection lines. The integration of all the various components is thus achieved in a most compact manner.

The side view of Fig. 6 shows the arrangement of a thermostat 8 and also a fuse 1 7 inserted in the feed line, in particular a safety fuse and also the accommodation of the necessary electrical connection lines 1 8.

The pre-warming apparatus of the invention is not restricted to the specially described embodiment and can also be modified in various respects. In particular it is not essential for the operation of the device that an oil return flow line is used. The described oil pre-warming in accordance with the basic principle of the invention can also be realized without problem without a return flow line.

It will be appreciated by those skilled in the art that further modifications can be made to the disclosed apparatus without departing from the scope of the present teaching. In particular it will be apparent that a plurality of shallow gap-like fuel flow channels could be provided in the heating block or in the filter head. In an arrangement of this kind it will be preferable for the total flow area of the various fuel flow channels to be substantially the same as the free flow crosssection of the supply line or the free flow crosssection of the input connection/duct to the heating block.

In such a multi-channel arrangement it is useful for the inlet connection to direct the fuel directly against the walls of the heating cartridges.

Claims

1. An apparatus for the pre-warming of fuel which tends to gell at low temperatures and which is forwarded from a supply tank by means of a pump via connecting lines to a combustion chamber burner, the apparatus being characterized by a heating block insertable into a supply line, the heating block having an input connection and an output connection and therebetween at least one shallow gap-like fuel flow channel the free flow cross-section of which is at least substantially the same as the free flow cross-section of the supply line into which it is to be connected.

2. Apparatus in accordance with Claim 1 and characterized in that at least one electrical heating element is provided in a recess in the heating block and that this heating element forms at least a part of the wall of said shallow gap-like fuel flow channel.

3. Apparatus in accordance with Claim 2 and characterized in that said shallow gap-like fuel flow channel is constructed as an annular section channel in the heating block.

4. Apparatus in accordance with Claim 3 and characterized in that the annular section channel is bounded on the one side by the wall of a bore formed in the heating block and on the other side by the outer wall of a heating cartridge inserted into this bore.

5. Apparatus in accordance with Claim 4 and characterized in that the bore is lightly conical and that its smallest diameter is disposed at the end of the bore in the region of the diameter of the heating cartridge.

6. Apparatus in accordance with Claim 4 and characterized in that at least the opening of the input connection consists of a bore in the heating block which opens directly against the outer wall of the heating cartridge.

7. Apparatus in accordance with Claim 1 and chrlacterized in that the heating block consists of metal and is connected with a thermostat controlling the input to the heating cartridge.

8. Apparatus in accordance with Claim 4 and characterized in that the height of the shallow gap-like fuel flow channel in the heating block lies in the range 0.1 to 2 mm.

9. Apparatus in accordance with Claim 4 and characterized in that the height of the shallow gap-like fuel flow channel in the heating block lies in the range from 0.1 to 1 mm.

10. Apparatus in accordance with Claim 1 and characterized in that the heating block is integrated in the cover of a filter housing inserted into the supply line.

11. Use of the apparatus in accordance with Claim 1 in an air heater operating with an oil burner in particular an air heater of portable construction.

12. Use of the apparatus in accordance with Claims 1 and 10 in a vehicle operated with Diesel fuel.

1 3. Apparatus for the pre-warming of fuel which tends to gell at low temperatures said apparatus comprising a fuel storage tank, a supply line leading from a position within said fuel storage tank via a pump to fuel burning equipment, a return flow line for returning excess fuel to said storage tank, said return flow line opening into said storage tank in the immediate vicinity of said position, a heating block inserted into said supply line upstream of said return flow line and in which said heating block has inlet and outlet connections for joining it into said fuel supply line, and at least one shallow gap like fuel flow channel extending between said inlet and outlet connections and defined between a bore in said heating block and a heating cartridge whereby to warm the fuel in said supply line and a localised body of fuel in said storage tank.

14. Apparatus in accordance with claim 13 and in which said heating block is incorporated in a fuel filter.

1 5. Apparatus in accordance with either of claims 13 and 14 and in which said inlet connection is adapted to direct fuel at the wall of said heating cartridge.

1 6. Apparatus substantially as herein described and illustrated with respect to the accompanying drawings.