FR2944338A1 - Strainer for fuel injection system in turboshaft engine of aircraft, has interior space delimited by filtering structure through which fuel is circulated from space towards outside of strainer, and heating systems electrically powered - Google Patents

Abstract

The strainer (30) has an interior space (46) partially delimited by a filtering structure (38) through which fuel is circulated from the interior space towards the outside of the strainer. Heating systems are electrically powered, where the heating systems comprise heating resistors. Bottom (44) of the strainer is formed opposite to an inlet (34) in a principal flow direction of the fuel through the inlet, where the bottom of the strainer is covered by a thermally insulated coating. The heating systems are mounted on the bottom of the strainer. Independent claims are also included for the following: (1) a turboshaft engine for an aircraft comprising fuel injection system (2) a method for controlling a fuel injection system for a turboshaft engine of aircraft.

Description

1 FUEL INJECTION SYSTEM HEATER PIPE FOR AN AIRCRAFT AIRCRAFT

TECHNICAL FIELD The present invention relates generally to the field of fuel injection system strainers for aircraft turboshaft engines, and more particularly for turbojet, turboprop, or other type of turbine engines. STATE OF THE PRIOR ART In a known manner, a strainer equips a fuel injection system in order to prevent the operation of this system from being disturbed by undesired particles. The strainer, thanks to its filtering structure, makes it possible to trap these particles, thus preventing them from flowing further downstream into the injection system.

A disadvantage relating to such a strainer lies in the fact that in case of operation at low temperatures, for example below 0 ° C, the fuel contains ice crystals / ice which are likely to seal part of the structure filtered through this fuel. Such a shutter is harmful since it is capable of generating an overpressure within the strainer, and, more generally, in the fuel system. In such a case, it is possible that the observed overpressure will lead to the automatic opening of the overpressure valve of the fuel pump, when such a valve is provided. This opening is accompanied by an instantaneous unwanted loss of thrust, which can of course have catastrophic consequences on flight safety. In addition, in the case of a too high pressure differential, there is even a risk of bursting of the strainer. With the clogging of the strainers by the ice / ice crystals, the fuel supply of the combustion chamber necessarily becomes heterogeneous. This is conducive to the appearance of hot spots on the walls of this chamber and on the stator of the turbine arranged downstream, with significant consequences on the service life of these parts. Finally, in case of really large clogging strainers, there is even a risk of extinction of the combustion chamber of the turbine engine.

DISCLOSURE OF THE INVENTION The object of the invention is therefore to remedy at least partially the disadvantages mentioned above, relating to the embodiments of the prior art. To do this, the invention firstly relates to a fuel injection system strainer for an aircraft turbine engine, said strainer having an interior space delimited at least partially by a filtering structure through which the fuel is intended to circulate from said interior space to the outside of said strainer. According to the invention, said strainer comprises a heating system intended to be electrically powered. Therefore, the clean heating system of the present invention allows to melt the ice / ice crystals contained in the fuel, thus preventing their accumulation on the filter structure of the strainer. The risks of clogging of the filter structure are therefore reduced to nothing, as well as the problems of overpressure, heterogeneity of fuel supply and extinction of the combustion chamber of the turbine engine. Preferably, said heating system comprises one or more heating resistors intended to be electrically powered.

Preferably, the strainer comprises an inlet and a bottom opposite said inlet in the main flow direction of the fuel through said inlet, the bottom also participating in the delimitation of said interior space.

According to a first preferred embodiment, said heating system comprises said strainer bottom. In this case, in order to limit the heat exchange between the heating system and the fuel located outside the strainer, and therefore to limit the power required to melt the ice / ice crystals, said strainer bottom is preferentially at least partially covered externally with a thermally insulating coating. Thus, the heat generated by the heating system is used to melt the ice crystals / frost located in the strainer. According to a second preferred embodiment, said heating system is an integral part of said filtering structure. Therefore, it is therefore a part of the filter structure, through which the fuel flows, which is directly electrically powered to heat and cause the melting of ice crystals / frost. According to a third preferred embodiment, said heating system is attached to said strainer bottom, in said interior space. This advantageously makes it easy to achieve the invention starting from a conventional strainer of the prior art, thus simply adding a heating system on the bottom strainer. Preferably, the strainer also comprises a power supply cable connected to the heating system, and running along said filtering structure, on which it can for example be glued. The invention also relates to a fuel injection system for an aircraft turbine engine comprising a strainer as described above, said injection system comprising a control unit designed to order the power supply of said heating system. only when the estimated or measured fuel temperature is below a predetermined threshold value. In this respect, it is noted that other conditions than that of the temperature could be verified before ordering the power supply of the heating system, such as the flow rate. In other words, the condition related to the temperature is a necessary but not necessarily sufficient condition to trigger the power supply order of the heating system. The invention also relates to an aircraft turbine engine comprising a plurality of fuel injection systems such as that described above, supplying a combustion chamber of the turbine engine. Finally, the subject of the invention is a method for controlling a fuel injection system for a turbine engine as described above, in which said heating system is electrically powered only when the estimated or measured fuel temperature is lower than at a predetermined threshold value. Other advantages and features of the invention will become apparent in the detailed non-limiting description below. BRIEF DESCRIPTION OF THE DRAWINGS This description will be made with reference to the appended drawings among which; FIG. 1 represents a longitudinal half-sectional view of an aircraft turbine engine portion, according to a first preferred embodiment of the present invention; - Figure 2 shows a perspective view of a fuel injection system of the type fitted to the turbine engine shown in Figure 1; Figure 3 shows a sectional view of a portion of the fuel injection system shown in Figure 2, incorporating the strainer of this system; - Figure 3a shows an alternative embodiment for the strainer shown in Figure 3; - Figures 4a to 4c show different possibilities of realization of the heating system fitted to the strainer shown in Figures 3 and 3a; Figure 5 shows a view similar to that shown in Figure 3, with the strainer in the form of a second preferred embodiment of the present invention; Figure 6 shows a view similar to that shown in Figure 3, with the strainer in the form of a third preferred embodiment of the present invention; and FIG. 7 shows one way of producing the heating system equipping the strainer shown in FIG. 6. DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS Referring to FIG. 1, a portion 1 of an aircraft turbine engine can be seen, according to FIG. a first preferred embodiment of the present invention. This portion 1 comprises an annular combustion chamber 2, with axis 4 also corresponding to the longitudinal axis of the turbine engine. At the combustion chamber 2 are associated a plurality of fuel injection systems 6 circumferentially spaced from each other and 7 fixedly mounted on an outer casing 7 through which they pass. They cooperate with an annular chamber bottom 8 centered on the axis 4, equipped with holes 10 in each of which are mounted means 12 for holding the injection system, as well as a heat shield 14 placed downstream of the chamber bottom in order to protect the latter from heat radiation from inside the combustion chamber. The holding means 12 each have an orifice 15 for receiving the free end of the rod 16 of its associated injection system 6, which is thus assembled to the outer casing 7 by means of a fixing plate 18. 2, it can be seen that each fuel injection system 6 has, successively in the direction of flow 20 of the fuel through this system, an assembly 22 housing a strainer for filtering the fuel, a valve assembly 24 , the mounting plate 18 and the injection rod 16. In addition, it comprises a control unit 26 connected by a power supply cable 28 to the assembly 22 housing the strainer, for purposes which will now be explained. Indeed, with reference to Figure 3 showing in detail the assembly 22, we can see that it houses a strainer 30 for filtering the fuel before it enters the valve assembly of the system. 'injection. Here, the strainer 30 comprises a threaded base 32 defining a fuel inlet 34, and mounted in a screwed manner on a body 36 of the assembly 22. From this base 32 8 extends a filtering structure 38 forming here the wall side of the strainer. It is noted that it can indifferently be cylindrical, conical, or other. In the example shown, its shape is cylindrical with a circular cross section, with axis 40. The strainer also comprises, opposite the inlet 34 in the main flow direction of the fuel through said inlet, schematized by the arrow 42 parallel to the axis 40, a strainer bottom 44. This bottom may for example be mounted screwingly on the end of the filtering structure 38. Thus, in this first preferred embodiment, the strainer defines with its base 32, its filtering structure 38, and its bottom 44 an interior space 46 in which the fuel enters before leaving the strainer by the filtering structure 38, to reach the chamber 48 defined by the body 36 and receiving the strainer 30. In known manner, once the fuel filtered and circulating in the chamber 48, it can then join the downstream parts of the injection system. One of the peculiarities lies in the fact that the bottom 44 is a heating system electrically powered by the cable 28. Thus, the arrival of the current by the same power cable 28 is used to heat the bottom 44, which diffuses then heat having the effect of melting the ice / ice crystals, thus preventing their accumulation on the filter structure 38. The risk that it is clogged are therefore reduced to nothing, implying that the fuel can flow through the one in a very satisfactory way. As can be seen in FIG. 3, the supply cable 28 can run along the filtering structure 38, for example by being glued to it, internally or externally. Then, it can cross the base 32, then out of the assembly 22 to reach the aforementioned control unit, an integral part of the injection system. In this regard, it is noted that the control unit 26 is designed to order the power supply of the bottom 44 only when the estimated or measured temperature of the fuel is below a predetermined threshold value, for example equal to 0 ° C. Thus, as long as this condition, as well as possibly other conditions, are not met, the heating portion is not activated. It is therefore activated only when the fuel temperature is below the predetermined threshold value, then is deactivated again when the fuel temperature returns above this same threshold value. In this regard, it is noted that a temperature sensor can be fixed at the level of the fuel injection system, or even at the level of the strainer. If this is not the case, thermal analysis models nevertheless make it possible to estimate the temperature of the fuel throughout the fuel system, including the strainers of the injection systems. It is then this estimated temperature that the control unit 26 compares with the predetermined temperature threshold value, in order to activate or deactivate the power supply of the heating base 44. So that the heat diffusion of the bottom 44 is essentially dedicated to the melting of ice / ice particles in the interior space 46, the bottom 44 is covered externally with a thermally insulating coating 50. This therefore makes it possible to limit the heat losses by convection with the fuel located outside the strainer 30, namely in the chamber 48 of the assembly 22 of the injection system. Such an embodiment is shown diagrammatically in FIG. 3. Furthermore, even if this has not been shown, it is possible to provide one or more discharge orifices through the bottom 44 and the insulating coating 50. Such orifices evacuation allow the water resulting from the melting of the ice / frost particles to escape from the interior space 46. In FIGS. 3 and 3a, the bottom 44 of the strainer is preferentially in the form of a solid element through which the fuel can not flow. This solid element is preferably in direct contact with the end of the filtering structure 38, so that the heat produced by this bottom 44 can diffuse through this structure 38. In this respect, FIGS. 4a to 4c show different possibilities of realization. 44. In Figure 4a, the solid element incorporates within it a heating resistor electrically powered by the cable 28, and here taking the form of a spiral. Thus, this spiral 52 is embedded in an insulating material 54 defining the bottom 44. 11 Other possible embodiments are conceivable, such as that shown in FIG. 4b where the heating resistor 52 defines several converging branches at one point, as well as the embodiment shown in Figure 4c showing a heating resistor 52 defining a plurality of parallel branches, still integrated in the insulating material 54. Referring now to Figure 5, there is shown a strainer according to a second preferred embodiment of the present invention. . This second mode has similarities with the first, being in this respect indicated that in the figures, the elements bearing the same reference numerals correspond to identical or similar elements. Thus, it can be seen here that the filtering structure 38 extends here all along the strainer from the base 32, and integrates the bottom 44. The particularity here lies in the fact that the structure 38 is divided into two parts made of different materials, a part 38a integrating the bottom 44 and intended to form the heating system, and a portion 38b interposed between the portion 38a and the base 32. Thus, the portion 38a is electrically powered by the cable 28 , and therefore constitutes a heating resistor. On the other hand, the portion 38b of the filtering structure is made of a material which is preferably an electrical insulator. In this second embodiment where the junction between the two parts of the filtering structure 38 is schematized by the reference 58, the particularity therefore lies in the fact that the heating system is an integral part of the filtering structure, since the fuel can cross it. In the third embodiment shown in FIG. 6, the strainer 30 comprises a filtering structure 38 which is preferably identical to those conventionally encountered in the prior art. Thus, this filtering portion 38 thus forms the side wall and the bottom 44 of the strainer. A heating system is thus attached to the bottom 44 in the interior space 46, here preferably taking the form of a T. In a manner similar to that described above, this heating system 60 is electrically connected by the cable 28 to the control unit 26 which ensures activation or deactivation. In FIG. 7, it can also be seen that the heating system 60 can integrate one or more heating resistors 52 embedded in an insulating material 54.

Of course, various modifications may be made by those skilled in the art to the invention which has just been described, solely as non-limiting examples.

Claims (11)

REVENDICATIONS1. A fuel injection system strainer (6) (6) for an aircraft turbine engine, said strainer having an interior space (46) defined at least partially by a filter structure (38) through which the fuel is intended to flow, said inner space to the outside of said strainer, characterized in that said strainer comprises a heating system (52, 54) for being electrically powered. 2. Strainer according to claim 1, characterized in that said heating system comprises one or more heating resistors (52) intended to be electrically powered. 3. Strainer according to claim 1 or claim 2, characterized in that it comprises an inlet (34) and a bottom (44) opposite said inlet in the main direction (42) of flow of fuel through of said inlet, the bottom (44) also participating in the delimitation of said interior space (46). 4. Strainer according to claim 3, characterized in that said heating system comprises said strainer bottom (44) .30 14 5. Strainer according to claim 4, characterized in that said strainer bottom (44) is covered at least partially, externally, with a thermally insulating coating (50). 6. Strainer according to claim 3 or claim 4, characterized in that said heating system is an integral part of said filter structure (38). 7. Strainer according to claim 3, characterized in that said heating system (60) is attached to said strainer bottom (44) in said interior space (46). 15 8. Strainer according to any one of the preceding claims, characterized in that it also comprises a power supply cable (28) connected to the heating system, and running along said filtering structure (38). A fuel injection system (6) for an aircraft turbine engine comprising a strainer (30) according to any one of the preceding claims, said injection system comprising a control unit (26) arranged to order the engine supplying said heating system only when the estimated or measured fuel temperature is below a predetermined threshold value. 10 30 15 10. Aircraft turbine engine comprising a plurality of fuel injection systems (6) according to claim 9, feeding a combustion chamber (2) of the turbine engine. 11. A method of controlling a fuel injection system for a turbine engine according to claim 9, characterized in that said heating system is electrically powered only when the estimated or measured fuel temperature is below a predetermined threshold value.