TECHNICAL FIELD OF INVENTION
The invention relates to a fuel filter for strong hold in icing. The field of the invention is that the filter in the fuel supply systems. In particular the field of the invention is that the filtering in the aerospace supply systems.
STATE OF THE ART
In a fuel supply system, the fuel usually pass into a low pressure portion of a fuel pump, and in heat exchangers. The fuel then goes to a filter and then passes through a high pressure pump. The fuel then passes through a fuel regulator and then through the injector before being injected into a combustion chamber.

The fuel filter filter contaminants from tanks and more generally from upstream system for providing a clean fuel to sensitive organs present downstream of the feed system.

The integration of filters in fluid systems has two main difficulties. The first is the detection of their clogging by contaminants, to provide for a replacement of the filter. The second is their susceptibility to icing which generates an early clogging of the filter.

This outfit icing fuel system is a certification requirement (CS-E 560 (e)). This requirement is very restrictive and it may be necessary to improve the resistance to icing.

A fuel filter is mainly equipped with a filter cartridge and a bypass valve, or bypass, or "bypass valve" which opens in the event of clogging of the cartridge.

Figure 1.a shows a sectional view of a filter 100 of the prior art. Figure 1.a shows the filter 100 of the prior art compote a cylindrical housing 1 10 in which a filter cartridge is introduced.

Figure 1.a shows a filter cartridge comprises a cylindrical core 120 on which is fixed a filter media. Conventionally a filter medium is a pleated fabric. The fuel is introduced into the filter and must pass through the filter medium to reach the inside of the core and continue its flow in the power system to which belongs the filter 100 of the prior art.

Figure 1.a shows a filter medium composed of pleats 130, each ply having a 140 fold external and internal folds 150 it shares with the adjacent pleats. The filter media is attached to two end plates glued to the two bases of the cylinder formed by the media, the cylindrical core being installed in the center between the two flanges to stiffen the assembly mechanically. A flange is, for example, a crown whose large radius corresponds to the radius of the cylinder and of which the minor radius is the core radius. A flange is, for example, a disk having a radius equal to that of the cylinder.

Figure 1.a illustrates a fuel inlet 160 area corresponding to an angular fraction, about 1/12 in this example, the cylinder formed by the filter. Figure 1.a shows also the direction 170 of fuel flow in the filter. The fuel arrives from the inlet zone, corresponding to the angular sector 160, then diffuses to the filter periphery and then to the filter kernel.

During a frost period of the fuel supply system, the ice after the water in the fuel sub-zero temperatures, has continually accumulate relatively rapidly on the cartridge until the clog and therefore cause the opening of the bypass. Thereafter, the downstream portion of the fuel system is subject to frost, and also contamination (The fuel not passing through the filter cartridge, it is not filtered).

Figure 1.b shows a first freezing step during which the ice 180 is deposited on the external folds of the pleats. At first the ice savings folds situated opposite, symmetrically with respect to the axis of the core cylinder, the fuel inlet 160.

Figure 1 illustrates a second .c icing step during which all the external folds are covered with ice 180.

Finally Figure 1 shows a third .d icing step in which the filter of the prior art is obstructed, the mirror 180 having clogged the free spaces between the outer folds. At this stage the feed system opens the bypass filter and the unfiltered fuel flows downstream of the feed system.

One of the key characteristics of a fuel filter in the icing test is the time before opening of the bypass filter.

Indeed, fuel icing events include engine cold starts. However, these periods are by nature transient, in the order of minutes to tens of minutes. Once past the start the engine and its systems begin to heat up and out of the conditions called icing.

In the prior art ice is deposited continuously with the arrival of fuel, that is to say in the direction of flow illustrated in FIGS. The folds clog one by one starting from the arrival area of ​​the fuel to the diametrically opposite area.

Just a small volume of ice to cover with a film of ice a lot of folds and thus greatly seal the cartridge. Indeed, the folds are clogged when the accumulated ice covers their outer fold.

The invention proposes a solution to delay the clogging of a filter and thus to delay the opening of a bypass.

DISCLOSURE OF INVENTION

The solution of the invention is to create a zone without folds on the angular sector of the cartridge to the fuel supply level. Fuel will de facto led to this accretion zone privileged ice on arrival in the filter.

The area is empty, it will allow the expansion of a large volume of ice while keeping a low surface covered with ice folds.

In order to keep equal filtering surface with respect to a filter of the prior art and thus keep the same ability to retain contamination, we will concentrate the folds in the zone diametrically opposite to the fuel intake.

For this purpose, one aspect of the invention relates to a cartridge for filtering device said cartridge comprising a pleated cloth arranged in the cylinder, the pleats being parallel to the generatrix of the cylinder characterized in that the cylinder

comprises a zone without folds, the area without folds being intended to be positioned in front of a fuel inlet in the filter device.

Besides the main characteristics that have just been mentioned in the preceding paragraph, the method / device according to the invention may have one or more additional characteristics among the following, taken individually or as technically possible combinations:

the cylinder comprises a concentrated folds area opposite to the area without folds;

the cartridge comprises a cylindrical core, the internal folds of the pleated cloth arranged cylindrically around the core being bonded to the flanges to the bases of the cylinder formed by the filter medium;

the pleated cloth arranged in cylinder comprises two sheets a first corrugated sheet and a second non-pleated sheet;

the ply density is a function of the angular sector.

BREVE DESCRIPTION DES FIGURES

Other features and advantages of the invention will emerge on reading the description which follows, with reference to the accompanying figures, which illustrate:

Figure 1.a, a sectional view of a filter of the prior art with an indication of the arrival direction and movement of the fuel in the filter;

Figures 1 .b .d 1, an illustration of the gradual clogging of a filter of the prior art;

Figure 1.b, start of icing on the outer portions of the pleats;

Figure 1 .c, icing has colonized all the folds;

.D Figure 1, the filter is clogged;

FIG 2. is a sectional view of a filter using a cartridge according to the invention;

FIGS 2b to 2.e, a progressive clogging illustration of a filter using a cartridge according to the invention;

Figure 2b, start icing in the box to concentrate the icing;

Figure 2.c, icing extends in the region provided for the concentrate;

Figure 2.d, icing begins to colonize the surface of the folds;

- Figure 2.e, icing extends all the folds without having clogged the filter;

Figure 3, an illustration of the gain obtained with the invention.

For clarity, identical or similar elements are identified by like reference signs throughout the figures,

The invention will be better understood from reading the following description and examining the accompanying figures. These are presented for illustrative purposes and in no way limit the invention.

DETAILED DESCRIPTION OF AN EMBODIMENT

Figure 2. a shows a filter 200 having a housing 1 10, wherein there is introduced a filtering cartridge according to the invention. On our here that the housing does not change between the prior art and the invention.

Figure 2. a shows an area 160 corresponding to a fuel inlet region in the housing, wherein the cartridge has no folds.

In the invention, at the angular sector corresponding to the fuel inlet zone in the filter, the filter medium is fixed flat on the core of the cartridge.

therefore carried out an inhomogeneous pleating the filter media. Since the power of the filter is bonded to the surface of the filter medium, the fact that there is a non-folded zone involves densification of the distribution of pleats in the folded zones.

In particular we arrange the filter medium to obtain an area of ​​folds concentrated in a zone diametrically opposite the zone without folds.

Thus, a cartridge for which the ply density is dependent on the angular sector.

an asymmetric cartridge that is to say a cartridge is thus obtained for which the ply density is not constant as a function of the angular sector of the relevant cartridge. This implies that such a cartridge insertion direction in the casing: the fold-free zone should be facing the fuel supply.

In a preferred variant is created a high density plies in the area diametrically opposite angular sector fuel inlet angular sector. It thus created an area with dense folds. In this variant the intermediate zones between the zone without folds and the high density plies zone, the folds density is that of a standard filter.

This shirring can be carried out with a filtering medium of constant thickness, that is to say using a continuous filter media sheet.

In a variant of the invention using two sheets of filter media, one for the folded zone, one for the zone without folds, which glue contiguously at an inner fold, on the core of the cartridge. This limits any loss of filter surface due to the use of two sheets.

Once the setting performed folds and the filter medium bonded to the flanges of the cartridge can be observed that the closure by icing cycle operates favorably. The description details the implementation of a fuel supply system, but his teaching is still for any power system by channeling fluid.

Figure 2b illustrates a first step of icing, corresponding to the first step of freezing of a filter of the prior art, during which the ice 180 is deposited on the external folds of the pleats. For a filter according to the invention, in this first step of the ice 280 is completely deposited in the area 160 without folds and saving integrally all the folds cartridge according to the invention.

Figure 2.c illustrates a second step of icing, corresponding to the second step of icing of a filter of the prior art, during which the ice 180 is deposited on all the external folds of the pleats. For a filter according to the invention, in this second step the ice 280 continues to drop, by thickening, fully in the area without folds and saving integrally all the folds cartridge according to the invention.

Figure 2.d shows a third step of icing, corresponding to the third step of icing of a filter of the prior art, in which the mirror 180 has obstructed the filter of the prior art. Figure 2.d shows that at this stage the ice 280 has not settled all external folds of the filter media. Figure 2.e shows a fourth step of icing, corresponding to a freezing step with a filter of the prior art in which the filter of the prior art is clogged. In this step the filter of the invention is still operational though the ice 280 has colonized all external envelopes.

For a filter according to the invention, in this third step the ice continues to thicken in the region without folds and begins to colonize part of the external foldings. The filter according to the invention thus remains operational. It will be clogged in a later step.

With a filter using a cartridge according to the invention, plugging of the filter, and therefore the opening of the bypass, is delayed.

Figure 3 shows a graph with the x-axis the time and ordered a percentage shutter. Ordinate there are two notable values:

A first value V1 corresponding to the opening of the bypass, a second value V2 corresponding to 99% closure.

Figure 3 shows a first curve C1 corresponding to a filter of the prior art, a second curve C2 corresponding to a filter using a cartridge according to the invention.

Figure 3 also shows:

A zone Z1 corresponds to the first stage of clogging of the cartridge, that is to say the phase where ice begins to accumulate in the area where the plies have been decentralized

- A zone Z2 corresponds to the second phase, where the ice has reached the portion of the cartridge where the folds are identical to a conventional cartridge and cartridge asymmetric

A zone Z3 corresponds to the last phase, in which the ice has clogged the portion of the cartridge where the pleating was concentrated.

In the zone Z1, so there is a cartridge according to the invention, for the same duration (and therefore the same amount of ice enters the cartridge) becomes blocked less quickly (the pressure difference to the input terminals and output cartridge increases less rapidly). This is represented by the timing of the ice accumulation illustrated above.

In the zone Z2, the two cartridges behave in the same manner vis-à-vis the ice, so it has no increase in the difference between the two curves.

In zone Z3, the two curves meet because the cartridge of the invention becomes clogged faster than the cartridge of the prior art. Indeed, once the ice has reached the area where the folds have been condensed, ice can achieve less wrinkles than in the case of a conventional cartridge, and thus the same volume of ice "obstructing" a larger proportion cartridge.

This is not a problem since this zone Z3 is purely theoretical in the case of a real presence bypass valve. Indeed, it is deemed to have exceeded the threshold opening of said valve, so no further flow or ice enters the filter cartridge.

The finding that both cartridges arrive at the same differential pressure end of icing is because we have clogged the same filtering surface. Indeed, it has reached more folds surface in the first phase (through deconcentration of folds), but have been less affected in the last phase (due to the concentration of plies).

A 100% icing, the two curves are supposed to give a theoretically infinite pressure difference: the filter is closed, nothing comes out.

3 illustrates with a cartridge according to the invention the bypass valve is open to t2> t1, and t1 is Instant opening the bypass valve for a filter of the prior art.

The difference t2 - 11 shows the increase in time before opening of the bypass valve.

Quantitatively, it is sufficient to dimension a feed system for t2 - 11> = 1 minute in magnitude so that the solution starts to be particularly advantageous (in order of magnitude transient engine speeds where icing conditions occur is such as starts). In any case dimensioning, t2 remaining greater than t1, the invention is useful.

Another advantage of the invention is that it operates during the period [t1 -t0] with less pressure loss in the filter, which is beneficial for the equipment downstream of the filter which will thus be better fed during icing.

It is also conceivable that both benefits will be in practice more important than represented, because the solution is based on the principle of increasing the achievable surface early frost can create another beneficial phenomenon.

Indeed, in the first zone of the cartridge, it is very likely, according to feedback on the equipment, the turmoil inherent in any confined flow a certain speed, causes additional ice accretion in volume inter- fold. In which case, it not only increases t2-t1, but also increases the total ice accumulation capacity of the cartridge, which results in a blue curve that will reach the stage 99% clogged later than the red curve (and either simultaneously).

Thus with the invention is increased frost holding time without impacting the ability to filter contaminants or congestion, or the mass of the filter and thus addresses a major problem of aeronautics.

The advantages are many:

Much less bypass occurrence (valve) of the filter in case of light blockage: increased service life of downstream equipment which thus see little of contamination;

- Increase the lifespan of equipment also via the decrease in the pressure drop in the icing (equipment well fed downstream);

Compliance with ease icing standards (you can adjust the opening of the bypass valve with more freedom because it happens less quickly to strong pressure differences);

- Extension of the field of use (less than operation of the airplane limitation, even in case of engine fuel inlet temperature <5 ° C as at present);

Logistics easier because there is no need antifreeze.

CLAIMS
1. cartridge filter device for the cartridge comprising a pleated cloth arranged in the cylinder, the pleats being parallel to the generatrix of the cylinder characterized in that the cylinder comprises a zone without folds, the area without folds being intended to be positioned in front of a fuel into the filter device.

2. Cartridge filter device according to claim 1, characterized in that the cylinder comprises a concentrated folds area opposite to the area without folds.

3. Cartridge filter device according to any one of the preceding claims, characterized in that the cartridge comprises a cylindrical core, the internal folds of the pleated cloth arranged cylindrically around the core being bonded to the flanges to the bases of the formed cylinder the filter media.

4. Cartridge filter device according to any one of the preceding claims, characterized in that the pleated web arranged in cylinder comprises two sheets a first corrugated sheet and a second non-pleated sheet.

5. Cartridge filter device according to any one of the preceding claims, characterized in that the folds of density is dependent on the angular sector.