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CA-3046730-C - FLUID CIRCUIT IN A TURBINE ENGINE

CA3046730CCA 3046730 CCA3046730 CCA 3046730CCA-3046730-C

Abstract

The invention relates to an assembly for a turbine engine comprising an oil circuit (24) including an air/oil heat exchanger (31), a primary bypass pipe (26) connecting an intake of the air/oil heat exchanger (31) to an outlet of the air/oil heat exchanger (31) and surrounding the air/oil heat exchanger (31) so as to exchange heat with the air/oil heat exchanger (31), and a secondary bypass pipe (28) of the primary pipe (26) connecting the upstream end of the primary bypass pipe (26) to the downstream end of the primary bypass pipe (26), the circuit (24) also comprising at least one valve (22) for controlling the passage of the flow of oil into the primary (26) and secondary (28) bypass pipes and control means (35) for controlling the opening of said at least one valve (22) for a temperature lower than a threshold temperature.

Inventors

  • Nicolas Alain Bernard Potel
  • Lancelot Guillou

Assignees

  • SAFRAN AIRCRAFT ENGINES

Dates

Publication Date
20260505
Application Date
20171213
Priority Date
20161214

Claims (7)

  1. 11 CLAIMS 1. Assembly (44) for a turbomachine (36), comprising an oil circuit including an air/oil heat exchanger 5 (31), a primary bypass line (26) connecting an inlet of the air/oil heat exchanger (31) to an outlet of the air/oil heat exchanger (31) and surrounding the air/oil heat exchanger (31) so as to exchange heat with the air/oil heat exchanger (31) and a secondary bypass line (28) 10 of the primary line (26) connecting the upstream of the primary bypass line (26) to the downstream of the primary bypass line (26), the circuit (24) also comprising at least one valve (22) for controlling the passage of oil flow in the primary (26) and secondary (28) bypass lines and means (35) for controlling the opening of said valve (22) for a temperature below a threshold temperature, said secondary bypass pipe (28) having a length at least ten times less than the length of the primary bypass pipe (26).
  2. 2. The assembly according to claim 1, wherein the circuit 20 comprises a single valve (22) arranged at the outlet of the primary bypass pipe (26) and downstream of the outlet of the secondary bypass pipe (28).
  3. 3. The assembly according to claim 1 or 2, wherein said at least a control valve (22) is a valve capable of adopting at least two positions, a first open position permitting the passage of oil and a second closed position blocking the passage of oil through the valve.
  4. 4. The assembly according to any one of claims 1 to 3, wherein the threshold temperature is 70°C. 12
  5. 5. The assembly according to any one of claims 1 to 4, wherein said control valve (22) is a two-way unidirectional valve.
  6. 6. The assembly according to any one of claims 1 to 5, wherein the secondary branch pipe (28) has a diameter at least three times smaller than the diameter of the primary branch pipe (26).
  7. 7. Turbomachine comprising the assembly defined in any one of claims 1 to 6, wherein the oil/air heat exchanger 10 radially delimits outwards a flow surface for a secondary airflow.

Description

1 FLUID CIRCUIT IN A TURBOMACHINE The present invention relates to an oil circuit in a turbomachine and to a turbomachine equipped with such an oil circuit. Like all internal combustion engines, turbomachinery, whether turbojets or turboprops, includes moving parts that rub against other moving parts or against fixed parts. To prevent breakage due to overheating from friction, the parts are sprayed with oil which, on the one hand, limits (or contains) their heating and, on the other hand, lubricates them to facilitate the sliding of the parts against each other. The oil circulates in a circuit 10 equipped with heat exchangers, in particular oil/air exchangers 12, as shown in Figure 1, 15 having a matrix 14, in the form of a sinuous conduit shaped to achieve heat exchange, into which the oil from said parts is introduced and then cooled before being injected again onto said parts. When starting a turbomachine in cold conditions 20 (for example with a temperature below 0°C), the oil in the matrix 14 of the air/oil exchanger 12 (or exchangers as appropriate) may be frozen, making heat exchange between the oil and the air difficult or even impossible since the oil cannot circulate in the matrix 14 of the exchanger 12. It is then necessary to preheat the matrix 14 of the air/oil heat exchanger 25 12. For this purpose, it is known to provide the air/oil heat exchanger 12 with a bypass duct 16 serving as a defrosting channel and which surrounds the matrix 14 of the air/oil heat exchanger 12 so as to warm the frozen oil. This branch pipe 16 is connected at its upstream end 30 to the inlet 18 of the heat exchanger 12 and to the outlet 20 of the heat exchanger 12. The oil circuit 1 O also includes a 2 valve 22 for controlling the oil flow in the bypass line 16 in order to allow oil circulation in the matrix 14 of the exchanger 12 only when the temperature is below a predetermined threshold. However, the oil passage section of the bypass line 16 being less than the oil passage section in the air/oil heat exchanger, there is an overpressure in the oil circuit when the matrix 14 of the exchanger 12 is frozen. Overpressure leads to a risk of damage to the oil circuit 10. In order to reduce this overpressure, an obvious solution is to increase the cross-section of the bypass pipe so as to increase the flow rate without changing the operating pressure conditions of the feed pumps. However, due to space constraints, increasing the cross-section of the bypass pipe 16 is not feasible. 15 The invention aims, in particular, to provide a simple, effective, and economical solution to this problem. To this end, the invention proposes an assembly for a turbomachine comprising an oil circuit including an air/oil heat exchanger, a primary bypass line connecting an inlet of the air/oil heat exchanger 20 to an outlet of the air/oil heat exchanger and surrounding the air/oil heat exchanger so as to exchange heat with the air/oil heat exchanger, and a secondary bypass line of the primary line connecting the upstream of the primary bypass line to the downstream of the primary bypass line, the circuit also comprising at least one control valve for the passage of the oil flow in the primary and secondary bypass lines and means for controlling the opening of said at least one valve for a temperature below a threshold temperature. According to the invention, the addition of a secondary bypass line 30 allows a portion of the fluid to be diverted from the primary bypass line, thereby reducing the fluid pressure in the primary bypass line 3 under cold operating conditions. The combination of a control valve for the oil flow in the primary and secondary bypass lines and means for controlling the valve opening at temperatures above a threshold temperature allows the primary and secondary bypass lines to operate only under cold operating conditions, with no oil flowing through these lines when the temperature exceeds the predetermined threshold temperature. Since the pressure loss increases with the decrease in temperature due to the increase in oil viscosity, it is understandable that the addition of a secondary bypass line is particularly useful. However, this secondary line has little impact on the oil heating function of the air/oil heat exchanger via the primary line. For example, diverting 30% of the oil flow from the primary bypass line 15 to the secondary bypass line maintains the same defrosting time for the heat exchanger. According to another feature of the invention, the assembly comprises a single valve arranged at the outlet of the primary bypass pipe and downstream of the outlet of the secondary bypass pipe. It would obviously be possible to have a valve for each of the primary and secondary bypass pipes. However, this obviously complicates the assembly. In another implementation, the single valve could be arranged at the inlet of the primary bypass pipe and upstream of the inlet of the secondary bypass pipe. The control valve can be