FR3108942A1 - DOUBLE-FLOW TURBOMACHINE FOR AN AIRCRAFT AND VENTILATION PROCESS FOR AT LEAST ONE TURBINE IN SUCH A TURBOMACHINE - Google Patents

Abstract

The invention relates to a bypass turbine engine (1) for an aircraft, comprising a ducted fan and a gas generator, the fan being configured to generate a primary flow of air in a primary duct (16) and a secondary flow in a secondary stream (18), the gas generator comprising at least one compressor (2, 3), a combustion chamber (4) and at least one turbine, the gas generator comprising at least one discharge valve (22) from the primary stream (16) located in said at least one compressor (2, 3) up to the secondary stream (18). According to the invention, the turbomachine (1) further comprises a heat exchanger (20), a first circuit (32) of which has an inlet (34) connected to an outlet (36) of said at least one discharge valve (22). ) and an outlet (38) configured to supply air to a ventilation circuit (40) of said at least one turbine. The invention also relates to a method for ventilating at least one turbine in such a turbomachine (1). Figure for the abstract: Figure 1

Description

DOUBLE-FLOW TURBOMACHINE FOR AN AIRCRAFT AND VENTILATION PROCESS FOR AT LEAST ONE TURBINE IN SUCH A TURBOMACHINE

Technical field of the invention

The present invention relates to a bypass turbomachine for an aircraft, such as a turbomachine comprising means for cooling a component located near a main axis of the turbomachine.

The invention relates more particularly to a bypass turbomachine comprising means for cooling a low pressure rotary shaft and / or lubricating oil pressurization chambers.

The invention also relates to a method for ventilating at least one turbine in such a turbomachine.

Technical background

In today's turbomachines, there are many internal engine air circuits. These circuits perform different functions.

Among these circuits, an air circuit performs both the function of pressurizing the lubricating oil chambers to prevent oil from escaping from these chambers and the function of cooling the low pressure shaft.

The air for this circuit is taken from the intermediate housing, downstream of the low pressure compressor, preferably between the low pressure compressor and the high pressure compressor.

The air passing through the enclosures is then exhausted by oil separators, and the remaining air is exhausted downstream of the low pressure turbine.

This circuit will undergo pressure losses due to changes in spokes, holes, seals, etc. ; at the level of the sample, along the low pressure shaft or at the pressure seals of the enclosures. It is therefore necessary that the pressure ratio (taken pressure / outlet pressure) is large enough for the air to circulate correctly and with the desired flow rate.

Among the constraints on this air circuit, the air temperature must be cold enough to cool the low pressure shaft and to ensure good bearing resistance. Indeed, a criterion on the temperature of the air entering the enclosures and bypassing the enclosures exists to ensure the good performance of the bearings by meeting the temperature criteria of the latter. The air pressure must also be sufficient so that the pressure ratio mentioned above is large enough to allow the specified flow rate to be circulated.

Also, in certain turbomachines, the thermodynamic cycle is such that the pressure ratio is too low for this circuit to meet these constraints. We must therefore find a workaround.

Known solutions consist in using heat exchangers. It is for example known to place a heat exchanger of the brick exchanger type in the secondary stream. The cold flow circulating in the secondary stream then passes through this brick exchanger, and the hot flow passes through channels formed inside the exchanger. The fins on the exchanger increase heat exchange between the two flows. However, since the heat exchanger is placed in the secondary flow, it increases the pressure drops and thus affects the overall efficiency of the engine. Even in the inter-vein position (also called the "core" position), air is drawn from the secondary flow, thus lowering the efficiency.

Another known solution consists in placing a heat exchanger of the surface exchanger type in the secondary stream. If the pressure drop caused is less than for a brick exchanger, such a solution also generates significant pressure drops for the air taken and for the air in the secondary stream in which the exchanger is placed.

Document EP-A1-0 743 435 describes a turbomachine comprising a heat exchanger integrated into a stator blade located in the secondary stream. According to this document, the blade has a cavity opening out at each radial end of the blade for the entry or exit of the air flow to be cooled.

Such a heat exchanger is thus suitable for an air circuit supplying a component located for example in the outer shell of the turbomachine, but it is not suitable for the ventilation of components located near the main axis of the engine. turbomachine. In addition, such an exchanger produces pressure drops in the secondary stream, which is detrimental to the overall efficiency of the engine.

The object of the present invention is in particular to resolve all or part of the aforementioned problems.

The invention provides for this purpose a bypass turbomachine for an aircraft, comprising a ducted fan and a gas generator, the fan being configured to generate a primary flow of air in a primary stream inside the gas generator. , and a secondary flow in a secondary stream extending around the gas generator, the gas generator comprising at least one compressor, a combustion chamber and at least one turbine, the gas generator comprising at least one discharge valve from the primary stream located in said at least one compressor up to the secondary stream.

According to the invention, it further comprises a heat exchanger, a first circuit of which has an inlet connected to an outlet of said at least one discharge valve and an outlet configured to supply air to a ventilation circuit of said at least one turbine. .

Such a configuration for the heat exchanger, in the form of a tap on the discharge of the discharge valve, makes it possible to effectively cool the pressurized air flow which has been taken downstream of the low pressure compressor, while producing low pressure. pressure losses. In fact, due to this tapping in the discharge valve, the flow rate discharged into the secondary flow is advantageously reduced compared to the flow rate discharged in the solutions of the prior art (flow rate which participated in the pressure drops of the secondary flow). The overall efficiency of the engine is thus improved. In addition, such a configuration makes it possible to use a lost flow as a cold source for the exchanger, again helping to reduce pressure losses. In addition, the cost / performance ratio of taking the cold source is low. Finally, the turbomachine according to the invention makes it possible to meet both the cooling needs of the low pressure shaft and the pressurization needs, despite a thermodynamic cycle not suited to a conventional circuit.

The bypass turbine engine according to the invention may include one or more of the characteristics below, taken in isolation from one another or in combination with one another:

• the exchanger is located in a gas generator compartment located between the primary and secondary streams;
• the inlet of the first circuit and the outlet of said at least one discharge valve are connected by a conduit which includes a bypass opening into said secondary stream in order to supply air to the exchanger when the discharge valve is closed;
• the exchanger comprises a second circuit comprising an inlet connected to an air bleed system in said at least one compressor, this bleed system being located downstream of said at least one discharge valve;
• the second circuit comprises an outlet connected to an air injection system in a space surrounded by said primary stream; and
• the injection system supplies air to a pressurization circuit of the bearing lubrication chamber (s) and / or a shaft ventilation circuit.

The invention also relates to a method for ventilating at least one turbine in a turbomachine as described above, this method comprising the steps of:

a) ventilate the turbine with air taken by said at least one discharge valve and passing through the first circuit of the exchanger, when this discharge valve is open, and

b) ventilate the turbine with air taken from the secondary stream and passing through the first circuit of the exchanger, when this discharge valve is closed.

Preferably, the air passing through the first circuit is heated by the air taken from said at least one compressor.

Brief description of the figures

The invention will be better understood and other details, characteristics and advantages of the invention will emerge more clearly on reading the following description given by way of non-limiting example and with reference to the accompanying drawings in which:

FIG. 1 is a schematic representation in axial section of a bypass turbomachine according to the invention, the turbomachine comprising a discharge valve;

FIG. 2 is an enlarged view of the turbomachine of FIG. 1, when the discharge valve is open; and

FIG. 3 is a view similar to that of FIG. 2, when the discharge valve is closed.

Detailed description of the invention

In Figure 1 is shown a bypass turbomachine 1 intended to equip an aircraft. Such a turbomachine 1 generally comprises, from upstream to downstream in the direction of the gas flow, one or more ducted blowers then a gas generator comprising one or more compressor stages, low pressure 2 then high pressure 3, a chamber combustion 4, one or more turbine stages, high pressure then low pressure, and a gas exhaust nozzle. The fan, the high and low pressure turbines and the nozzle are not shown in the figures for reasons of clarity.

The turbomachine 1 further comprises, moving away from its main axis A, a low pressure shaft 12, a high pressure shaft 14, a primary air flow duct 16 arranged inside the gas generator, a secondary air flow duct 18 extending around the gas generator, and a heat exchanger 20.

The blower (s) are configured to generate a primary flow of air in the primary stream 16, and a secondary flow of air in the secondary stream 18.

The gas generator further comprises at least one discharge valve 22 from the primary stream 16 located in the stage (s) of compressors 2, 3 to the secondary stream 18. Such valves 22 are discharge valves low pressure compressor stages 2. In fact, depending on the flight phases and for operability reasons, it is necessary to unload the low pressure compressor 2, in other words to evacuate, downstream of this compressor 2, of the primary flow to the secondary stream 18. Such a discharge is carried out by a hatch, opened by the discharge valve (s) 22, which allows part of the air from the primary stream 16 to go to the secondary stream 18. Such discharge valves 22 also sometimes play a role of scooping foreign bodies (such as for example hail or hailstones) before the high pressure compressor 3.

The heat exchanger 20 is located in an inter-vein compartment 28, also called a "core compartment", separating the primary vein 16 and the secondary vein 18. The heat exchanger 20 is of the air-air type and the source of heat exchanger. The cold air from the heat exchanger 20 is formed by a tap 30 on the discharge valve (s) 22. More precisely, the heat exchanger 20 comprises a first circuit 32, an inlet 34 of which is connected to a outlet 36 of the discharge valve (s) 22, and one outlet 38 of which is configured to supply air to a ventilation circuit 40 of the turbine (s). This ventilation circuit 40 can also make it possible to ventilate and cool the inter-vein compartment 28. Preferably, and as illustrated in FIG. 1, the heat exchanger 20 also comprises a second circuit 42, an inlet 44 of which is connected. to a system 46 for taking air from the high pressure compressor (s) 3, and an outlet 48 of which is connected to a system 50 for injecting air into a space surrounded by the primary duct 16.

As will be described in more detail later with reference to Figures 2 and 3, the inlet 34 of the first circuit 32 of the exchanger 20 and the outlet 36 of the discharge valve (s) 22 are connected by a conduit 52. The conduit 52 comprises a bypass 54 opening into the secondary stream 18 in order to supply air to the exchanger 20 when the discharge valve 22 is closed.

The air sampling system 46 is located downstream of the discharge valve (s) 22 and allows hot air to be taken from the high pressure compressor (s) 3, thus providing a source of hot air for the exchanger 20.

The air injection system 50 supplies air to a pressurization circuit 55 of the bearing lubrication chamber (s) as well as a ventilation circuit 56. The pressurization circuit 55 is designed to supply the chambers with pressurized air. containing lubricating oil for moving parts, which are located at the level of the low pressure shaft 12 and which make it possible to pressurize this lubricating oil. The ventilation circuit 56 is designed to cool the low pressure shaft 12. The air leaving the second circuit 42 of the exchanger at the level of the air injection system 50 thus pressurizes the enclosures and cools the low shaft. pressure 12, passing through the intermediate casing.

The foreign bodies scooped out by the discharge valve (s) 22 must be ejected without being captured by the connection 30 in the direction of the exchanger 20. To do this, the turbomachine 1 is preferably fitted with a filter or d 'a protective grid (not shown) disposed at the level of the bifurcation for the exchanger 20. The exchanger 20 is then effectively protected from these foreign bodies. As a variant, it is also possible to adjust the profile of the air samples.

The method for ventilating the turbine (s) of the turbomachine 1 according to the invention will now be described with reference to FIGS. 2 and 3. To facilitate the remainder of the description, it will be assumed that the turbomachine 1 only comprises a single turbine, although this could equally well include several turbines within the framework of the present invention.

During an initial step illustrated in FIG. 2, when the discharge valve 22 is open, the turbine is ventilated via the ventilation circuit 40 by the air taken by this valve 22 and passing through the first circuit 32 of exchanger 20. By taking this air from the discharge of the discharge valve 22, the flow discharged into the secondary flow is reduced. The pressure drops of the secondary flow are thus advantageously reduced and the overall efficiency of the motor is improved.

During a following step illustrated in FIG. 3, when the discharge valve 22 is closed, the turbine is ventilated via the ventilation circuit 40 by the air taken from the secondary stream 18 and passing through the first circuit 32 of the exchanger 20. This air taken from the secondary stream 18 being cold air, it can therefore participate in the cooling of the air supplied at the outlet 48 of the second circuit 42 of the exchanger 20, intended for the injection system air 50.

During these two steps, the air passing through the first circuit 32 of the exchanger 20 is heated by the air taken from the high pressure compressor (s) 3, via the air sampling system 46 .

Claims (8)

By-pass turbomachine (1) for an aircraft, comprising a ducted fan and a gas generator, the fan being configured to generate a primary flow of air in a primary stream (16) inside the gas generator, and a secondary flow in a secondary stream (18) extending around the gas generator, the gas generator comprising at least one compressor (2, 3), a combustion chamber (4) and at least one turbine, the generator of gas comprising at least one discharge valve (22) from the primary stream (16) located in said at least one compressor (2, 3) to the secondary stream (18), characterized in that it further comprises a heat exchanger (20) having a first circuit (32) having an inlet (34) connected to an outlet (36) of said at least one relief valve (22) and an outlet (38) configured to supply air to a circuit (40) ventilation of said at least one turbine. Turbomachine (1) according to claim 1, wherein the exchanger (20) is located in a compartment (28) of the gas generator located between the primary and secondary streams (16, 18). Turbomachine (1) according to claim 1 or 2, wherein the inlet (34) of the first circuit (38) and the outlet (36) of said at least one discharge valve (22) are connected by a duct (52) which comprises a bypass (54) opening into said secondary stream (18) in order to supply air to the exchanger (20) when the discharge valve (22) is closed. Turbomachine (1) according to one of the preceding claims, in which the exchanger (20) comprises a second circuit (42) comprising an inlet (44) connected to a system (46) for taking air from said at least one compressor (2, 3), this sampling system (46) being located downstream of said at least one discharge valve (22). Turbomachine (1) according to claim 4, wherein the second circuit (42) comprises an outlet (48) connected to a system (50) for injecting air into a space surrounded by said primary stream (16). Turbomachine (1) according to Claim 5, in which the injection system (50) supplies air to a pressurization circuit (55) of the bearing lubrication chamber (s) and / or a ventilation circuit (56). tree (s). A method of ventilating at least one turbine in a turbomachine (1) according to one of the preceding claims, this method comprising the steps of:

1. ventilate the turbine (2, 3) with the air taken by said at least one discharge valve (22) and passing through the first circuit (32) of the exchanger (20), when this discharge valve (22) is open, and
2. ventilate the turbine (2, 3) with the air taken from the secondary stream (18) and passing through the first circuit (32) of the exchanger (20), when this discharge valve (22) is closed.

A method according to claim 7, wherein the air passing through the first circuit (32) is heated by air taken from said at least one compressor (2, 3).