Turbine lubrication system including bypass for preferential supply of lubricant to low speed reduction gear

Abstract

The invention relates to a lubrication system (100) for a turbomachine comprising a reduction gear (152). The lubrication system (100) comprises a main branch (120) and a bypass branch (140) arranged in parallel to the main branch (120). The main branch (120) comprises a heat exchanger (121, 122, 124). The hydraulic resistance of the bypass branch (140) is lower than the hydraulic resistance of the main branch (120). The reduction gear (152) is located downstream of the main branch (120) and the bypass branch (140). The lubrication system (100) comprises at least one bypass device (200) configured to supply lubricant to the bypass branch (140) when a pressure value of the lubricant is below a threshold value.

Description

TECHNICAL FIELD

[0001] The present invention relates to the general technical field of aircraft turbines such as turbojet engines and turboprop engines. More precisely, the present invention belongs to the technical field of lubrication systems for turbines. BACKGROUND

[0002] Some turbines comprise a reduction gear for driving a fan of the turbine. This reduction gear is for example a epicyclic reduction gear. This reduction gear is in particular mechanically connected to a shaft of a low pressure body comprising a low pressure compressor and a low pressure turbine of the turbine.

[0003] These turbines comprise a lubrication system comprising a heat exchanger for cooling a lubricant, a bearing lubrication chamber of the turbine and a lubrication chamber of the reduction gear.

[0004] The lubrication chamber of the reduction gear is supplied with lubricant to cool the reduction gear and to lubricate the teeth of the reduction gear. When the reduction gear of the turbine is running at low speed, it can result in a very low pressure and flow of lubricant in the lubrication system. The reduction gear can be insufficiently supplied with lubricant, which is liable to damage the reduction gear. SUMMARY

[0005] The present invention aims at at least partially solving the problems encountered in the solutions of the prior art.

[0006] In this regard, the object of the present invention is a lubrication system for a turbine comprising a reduction gear for driving a module of the turbine.

[0007] According to the invention, the lubrication system comprises a main branch and a bypass branch, the bypass branch being arranged in parallel to the main branch. The main branch comprises a heat exchanger. The hydraulic resistance of the bypass branch is lower than the hydraulic resistance of the main branch. The reduction gear is located downstream of the main branch and of the bypass branch.

[0008] The lubrication system comprises at least one bypass device configured to supply the bypass branch with lubricant when the pressure value of the lubricant is below a threshold value.

[0009] By the lubrication system according to the invention, when the flow of lubricant and the pressure of the lubricant are too low to supply the entire turbine with lubricant, the reduction gear is supplied with lubricant in a preferential manner with respect to the rest of the turbine through the bypass branch.

[0010] When the turbine is running at low speed, the reduction gear is for example supplied with lubricant by the bypass branch. In particular, when the flow and pressure of the lubricant are sufficient to supply the entire turbine, for example when the turbine is running at high speed, the reduction gear is supplied with lubricant by the main branch.

[0011] The lubricant is typically an oil.

[0012] The invention can optionally comprise one or more of the following features, in combination with or without the other features.

[0013] According to one design feature, the bypass device is configured to supply the lubricant to the main branch when the pressure value of the lubricant is strictly greater than the threshold value.

[0014] Preferably, the bypass device is hydraulically controlled and / or mechanically controlled by the pressure of the lubricant.

[0015] According to one design feature, the bypass device comprises: a lubricant inlet; a first lubricant outlet fluidly connected to the bypass branch; a second lubricant outlet fluidly connected to the main branch; an obturator configured to at least partially close the first outlet and / or the second outlet; and means for elastically acting on the obturator, the means for elastically acting on the obturator being configured to elastically act on the obturator so that the obturator closes the second outlet.

[0016] Preferably, the obturator is configured to enable the circulation of the lubricant towards the first outlet when the lubricant pressure is below the threshold value.

[0017] According to one design feature, the bypass device comprises a first bypass valve and / or a second bypass valve.

[0018] Preferably, the obturator of the first bypass valve comprises a sliding portion. Preferably, the obturator of the second bypass valve comprises a sliding portion.

[0019] Preferably, the first bypass valve is bistable. Preferably, the first bypass valve comprises a first stable open position in which the first bypass valve supplies the lubricant to the bypass branch and a second stable open position in which the first bypass valve supplies the lubricant to the main branch.

[0020] Preferably, the second bypass valve is bistable. Preferably, the second bypass valve comprises a first stable open position in which the second bypass valve supplies the lubricant to the bypass branch and a second stable open position in which the second bypass valve is configured to supply the lubricant to the main branch.

[0021] According to one design feature, the bypass device comprises a first bypass valve and a second bypass valve, the second bypass valve being fluidly connected in series to the first bypass valve so that the first bypass valve and the second bypass valve supply the lubricant to the bypass branch when the pressure value of the lubricant is below the threshold value. The first bypass valve is configured to fluidly supply the main branch directly when the pressure value of the lubricant is strictly greater than the threshold value.

[0022] According to a design feature, the first bypass valve comprises: a lubricant inlet; a first lubricant outlet; a second lubricant outlet fluidly connected to the main branch upstream of the heat exchanger; an obturator configured to close the first outlet and / or the second outlet; and means for elastically acting on the obturator, configured to elastically act on the obturator so that the obturator closes the second outlet. The obturator of the first bypass valve is configured to enable the circulation of lubricant towards the first outlet when the lubricant pressure is below a pressure threshold.

[0023] The second bypass valve comprises: a lubricant inlet; a first lubricant outlet fluidly connected to the bypass branch; a second lubricant outlet fluidly connected to the main branch upstream of the heat exchanger; an obturator configured to close the first outlet or the second outlet; and means for elastically acting on the obturator, configured to elastically act on the obturator so that the obturator closes the second outlet. The obturator of the second bypass valve is configured to enable the circulation of lubricant towards the first outlet when the lubricant pressure is below a pressure threshold.

[0024] The first outlet of the first bypass valve is in particular fluidly connected to the lubricant inlet of the second bypass valve.

[0025] According to a design feature, the lubrication system comprises a non-return device configured to limit / prevent the circulation of lubricant from the reduction gear to the main branch.

[0026] Preferably, the non-return device comprises a non-return valve.

[0027] According to a design feature, the lubrication system comprises an obturator position monitoring device configured to monitor the position of the obturator of the bypass device.

[0028] Preferably, the monitoring device is configured to determine the lubricant pressure in the main branch, for example by means of a first pressure sensor, and the lubricant pressure in the bypass branch, for example by means of a second pressure sensor. The monitoring device can monitor the position of the obturator of at least one bypass valve by comparing the lubricant pressure value in the main branch and the lubricant pressure value in the bypass branch.

[0029] According to a design feature, the main branch comprises a heat exchanger, a filter, a reservoir, a pump and / or a valve.

[0030] Preferably, the main branch comprises a lubricant distributor.

[0031] According to one design feature, the main branch and / or the bypass branch are configured to supply lubricant to an accessory drive box for the turbomachine, the accessory drive box for the turbomachine comprising a fuel pump, a lubricant pump, a generator and / or a starter for starting the turbomachine.

[0032] Preferably, the starter comprises a gear train.

[0033] The application also relates to a turbomachine comprising a reduction gear, a module and a lubrication system as defined above. The turbomachine module comprises a fan and / or a propeller, a compressor and a turbine. The reduction gear is configured to be driven by the turbine.

[0034] Preferably, the turbine is a low pressure turbine of the turbomachine. Preferably, the turbomachine is a turbojet. The turbomachine is in particular an aircraft turbomachine. BRIEF DESCRIPTION OF DRAWINGS

[0035] The application will be best understood by reading the following description of example embodiments, given by way of illustration and non-restrictive examples, and with reference to the appended drawings, in which:

[0036] - Figure 1 A turbomachine comprising a lubrication system according to a first embodiment of the application is shown;

[0037] - Figure 2 is a partial schematic view of the lubrication system according to the first embodiment at low speed;

[0038] - Figure 3 is a partial schematic view of the lubrication system according to the first embodiment at high speed;

[0039] - Figure 4 is a partial schematic view of the lubrication system according to a second embodiment at low speed;

[0040] - Figure 5A is a partial schematic view of the lubrication system according to a third embodiment at low speed;

[0041] - Figure 5B is a partial schematic view of the lubrication system according to the third embodiment at high speed;

[0042] - Figure 5C is a partial schematic view of the lubrication system according to the third embodiment at high speed and in case the first bypass valve is undesirably locked in its first open position;

[0043] - Figure 5D is a partial schematic view of the lubrication system according to the third embodiment at high speed and in case the second bypass valve is undesirably locked in its first open position;

[0044] -Figure 6A is a schematic view of a bypass valve of a lubrication system according to the first embodiment when the bypass valve is in a first open position;

[0045] - Figure 6B is a schematic view of a bypass valve of a lubrication system according to the first embodiment when the bypass valve is in a second open position;

[0046] - Figure 7 shows the pressure drop of a bypass valve according to the first embodiment relative to the pressure drop of a valve having a conventional structure;

[0047] - Figure 8 shows a turbomachine lubrication method by a lubrication device according to one of the embodiments of the application. DETAILED DESCRIPTION

[0048] The same, similar or equivalent parts of different figures are denoted by the same reference signs in order to facilitate the passage from one figure to the other.

[0049] Figure 1 A ducted twin-corps turbomachine 1 is shown. The turbomachine 1 is a turbojet having the shape of a revolution around a longitudinal axis AX.

[0050] The turbomachine 1 comprises, in this order, an air inlet channel 2, a fan 3, a low pressure compressor 4, a high pressure compressor 6, a combustion chamber 7, a high pressure turbine 8 and a low pressure turbine 9 on the path of a primary flow in a primary channel 11.

[0051] Generally, the term "air" refers to any gas that can act as an oxidizer in the turbomachine 1.

[0052] The low pressure compressor 4, the high pressure compressor 6, the high pressure turbine 8 and the low pressure turbine 9 delimit a secondary flow channel 13 through which a secondary flow passes.

[0053] The high pressure compressor 6 and the high pressure turbine 8 are mechanically connected by a drive shaft of the high pressure compressor 6 to form a high pressure corps of the turbomachine 1. In a similar manner, the low pressure compressor 4 and the low pressure turbine 9 are mechanically connected by a turbomachine shaft 1 to form a low pressure corps of the turbomachine 1. The fan 3 is mechanically connected to the turbomachine low pressure corps by a reduction gear 152.

[0054] The low pressure compressor 4, the high pressure compressor 6, the combustion chamber 7, the high pressure turbine 8 and the low pressure turbine 9 are surrounded by an inner fairing extending from the inlet channel 2 to the low pressure turbine 9.

[0055] The inner fairing is surrounded by an outer casing delimiting the turbomachine radially outwardly with respect to the longitudinal axis AX. The outer casing delimits the secondary channel 13 radially outwardly in particular at the fan 3.

[0056] Combined reference Figures 2 to 5D The turbomachine 1 comprises an accessory drive box 170 comprising fuel pumps, lubricant pumps, a generator and a starter for starting the turbomachine 1. The starter comprises a gear train. The accessory drive box 170 is connected to the shaft of the high pressure body of the turbomachine 1 by a mechanical power take-off.

[0057] Figure 2 A lubrication system 100 according to a first embodiment of the application is shown. The lubricant is generally oil.

[0058] The lubrication system 100 comprises an upstream branch 110, a main branch 120 and a bypass branch 140 each located downstream of the upstream branch 110, a primary branch 150 and a secondary branch 160 each located downstream of the main branch 120 and downstream of the bypass branch 140, and a lubricant return circuit 180.

[0059] In the present description, the terms upstream and downstream are used with reference to the general flow direction of the lubricant in the lubrication system 100 from upstream to downstream.

[0060] The upstream branch 110 comprises a lubricant reservoir 111, a pumping assembly 112, a first hydraulic resistor 114 and a bypass device 200.

[0061] The pumping assembly 112 comprises at least one pump for supplying lubricant in the lubrication system 100, and in particular comprises at least one lubricant return pump designed to circulate lubricant towards the reservoir 111. Each of these pumps is for example a centrifugal pump, which can form part of the accessory drive box 170. The flow rate of lubricant pumped by the pumping assembly 112 depends in particular on the speed of the turbomachine 1, wherein the maximum flow rate of pumped lubricant increases according to the operating speed of the turbomachine 1.

[0062] The lubricant return pump is connected to a third lubricant return branch 186 which leads lubricant from the pumping assembly 112 to the reservoir 111.

[0063] In the present description, by analogy with electrical fields, the hydraulic resistance of a lubrication system element 100 is defined as the magnitude of the ratio between the pressure drop across this element and the flow rate of lubricant passing through this element. By metonymy and still by analogy with electrical fields, a hydraulic resistor corresponds to an element of the lubrication system 100 whose value of hydraulic resistance characterizes it. The first hydraulic resistor 114 comprises for example an oil filter.

[0064] The bypass device 200 comprises at least one first bypass valve 210. The bypass device 200 is hydraulically controlled and / or mechanically controlled by the pressure of the lubricant.

[0065] Generally, the bypass device 200 is designed to distribute lubricant to the bypass branch 140 when there is a risk that the pressure and flow of lubricant in the lubrication system 100 are insufficient to properly supply the entire turbomachine 1. More precisely, the bypass device 200 is configured to supply lubricant to the main branch 120 when the lubricant pressure value is strictly greater than a threshold value. The bypass device is configured to supply lubricant to the bypass branch 140 when the lubricant pressure value is below the threshold value.

[0066] More particularly with reference to the first embodiment and Figure 6A and Figure 6B The bypass device 200 comprises a first bypass valve 210, a lubricant inlet duct 212, a pressurization duct 218, a first lubricant outlet duct 214 and a second lubricant outlet duct 216.

[0067] The first bypass valve 210 comprises a lubricant inlet 211, a pressurization inlet 217, a first lubricant outlet 213, a second lubricant outlet 215, an obturator 202 and a spring forming the means 204 for elastically acting on the obturator.

[0068] The lubricant inlet 211 is fluidly connected to the lubricant inlet duct 212. The pressurization inlet 217 is fluidly connected to the pressurization duct 218. The first lubricant outlet 213 is fluidly connected to the bypass branch 140. The second outlet 215 is fluidly connected to the main branch 120.

[0069] The pressurization duct 218 is fluidly connected first to the inlet duct and second to the pressurization inlet 217. The pressurization duct 218 makes it possible to introduce lubricant to the pressurization inlet 217, the pressure of which is approximately the same as the pressure of the fuel at the lubricant inlet 211.

[0070] The first bypass valve 210 is bistable. The first bypass valve comprises a first stable open position and a second stable open position.

[0071] When the pressure of the lubricant at the inlet 211 of the first bypass valve 210 is below the threshold value, the first bypass valve 210 is in the first stable open position. In the first stable open position, the first bypass valve 210 supplies lubricant to the bypass branch 140.

[0072] When the pressure of the lubricant at the inlet 211 of the first bypass valve 210 is above the threshold value, the first bypass valve 210 is in the second stable open position. In the second stable open position, the first bypass valve supplies lubricant to the main branch 120.

[0073] The obturator 202 comprises a sliding part that slides in a housing 201 which delimits the outside of the first bypass valve 210. The sliding part of the obturator 202 delimits, inside the housing 201, a first chamber 207 and a second chamber 209, on either side of the obturator 202 and each having a variable volume. The sliding part of the obturator 202 has a first passage 206 and a second passage 208 passing through the sliding part, the second passage being distinct from and fluidically separate from the first passage 206.

[0074] In the illustrated embodiment, the spring of the elastic means 204 for acting on the obturator is a compression spring located in the first chamber 207. This spring is configured to act on the obturator 202 so that the first bypass valve 210 is in the first open position. In other words, the elastic action means 204 of the obturator are configured to elastically act on the obturator 202 so that the obturator closes the second outlet 215 of the first bypass valve 210.

[0075] With reference to Figure 6A When the lubricant pressure is below the threshold, the obturator 202 closes the second outlet 215 under the action of the spring of the elastic action means 204. The second passage 208 is blocked by the housing 201. The lubricant inlet 211 thus appears in the first passage 206. The outlet of the first passage 206 is aligned with the first outlet duct 214. The lubricant can flow from the inlet duct 212 to the first outlet duct 214 through the first bypass valve 210.

[0076] With reference to Figure 6B When the pressure of the lubricant is above the threshold, the obturator 202 closes the first outlet 213 by opposing the action of the spring of the elastic action means 204. The first passage 206 is blocked by the housing 201. The lubricant inlet 211 thus appears in the second passage 208. The outlet of the second passage 208 is aligned with the second outlet duct 216. The lubricant can flow from the inlet duct 212 to the second outlet duct 216 through the first bypass valve 210.

[0077] With reference again to Figure 2 The main branch 120 is fluidically connected to the second outlet 215 of the bypass device 200 by the main duct 123. The main branch comprises, from upstream to downstream, the first heat exchanger 121, the second heat exchanger 122, the lubricant distributor 169, the third heat exchanger 124 and the first non-return device 130.

[0078] The main branch 120 supplies lubricant to the preferential branch 150 and to the secondary branch 160 when the flow rate and pressure of the lubricant in the lubrication system 100 are sufficient to supply the entire turbomachine 1 with lubricant. The main branch 120 supplies lubricant to the downstream zone of the lubrication system 100 when the speed of the turbomachine 1 is sufficiently great, generally at speeds other than take-off and landing, for example the cruising speed of the turbomachine 1.

[0079] Each of the heat exchangers 121, 122, 124 can be an air-oil heat exchanger or an oil-fuel heat exchanger. Each heat exchanger can be a brique-type heat exchanger or a surface heat exchanger. The heat exchangers 121, 122, 124 can be arranged in series with each other and / or in parallel with each other.

[0080] The lubricant distributor 169 is a lubricant direction control valve comprising a lubricant inlet and a plurality of lubricant outlets. The lubricant distributor distributes the lubricant arriving at the inlet of the lubricant distributor between the different outlets of the lubricant distributor. The distributor 169 comprises, for example, as many positions as outlets as lubrication chambers in the lubrication system 100.

[0081] In the embodiment shown, the distributor 169 comprises a lubricant inlet downstream of the second heat exchanger 122, a first lubricant outlet fluidically connected downstream of the main branch 120, a second outlet fluidically connected to the secondary branch 160, and a third outlet fluidically connected to the reservoir 111. The third outlet of the distributor 169 is connected to a second lubricant return branch 184 which leads lubricant from the lubricant distributor 169 to the reservoir 111. The lubricant distributor 169 is in particular a hydraulic direction control valve with a plurality of passages and a plurality of positions of known structure.

[0082] The first non-return device 130 comprises a non-return valve. The first non-return device is configured to prevent the circulation of lubricant from downstream of the main branch 120 through the main branch 120. The first non-return device 130 prevents the circulation of lubricant from the preferential branch 150 to the main branch 120.

[0083] The bypass branch 140 is arranged in parallel with the main branch 120. The bypass branch is fluidically connected to the first outlet 213 of the bypass device 200 by a bypass duct 141 and to the main duct 123 at the downstream of the first non-return valve 130. The total hydraulic resistance of the bypass branch 140 is less than the total hydraulic resistance of the main branch 120 to limit the pressure drop in the bypass branch 140 relative to the pressure drop in the main branch 120.

[0084] The bypass branch 140 is intended to supply lubricant to the priority branch 150 so that the priority branch is supplied preferentially with respect to the secondary branch 160 when there is a risk of insufficient lubricant flow and pressure in the lubrication system 100 to supply the entire turbomachine 1. In each of the embodiments shown, the bypass branch 140 supplies lubricant only to the priority branch 150.

[0085] More particularly with respect to the first embodiment, the priority branch 150 comprises, from upstream to downstream, a shut-off valve 132 and a lubrication chamber of a reduction gear 152. The priority branch 150 is connected to the main duct 123 and to the bypass duct 141 at downstream of the first non-return device 130 by a first priority duct 153.

[0086] The shut-off valve 132 is configured to stop the supply of lubricant to the lubrication chamber of the reduction gear 152 when the pressure of the lubricant supplied to this chamber is too great. The shut-off valve is intended to protect the reduction gear 152 when the lubricant supply in this lubrication chamber is disturbed.

[0087] The lubrication chamber of the reduction gear 152 supplies lubricant to the reduction gear 152 to lubricate and cool the reduction gear. In particular, when the turbomachine 1 is running, this lubrication chamber lubricates the teeth of the reduction gear 152 to limit the wear of the teeth.

[0088] The secondary branch 160 comprises a fourth heat exchanger 168, a first bearing lubrication chamber 162, a second bearing lubrication chamber 164, a third bearing lubrication chamber 166 and a lubrication chamber of an accessory box 170. In the embodiment shown, the secondary branch is supplied with lubricant only by the distributor 169.

[0089] The fourth heat exchanger 168 can be an air-oil heat exchanger or an oil-fuel heat exchanger. The fourth heat exchanger can be a brick-type heat exchanger or a surface heat exchanger.

[0090] Each of the lubrication chambers 162, 164, 166 is a lubrication chamber of a turbomachine shaft bearing, in particular of a shaft of a high-pressure body or of a shaft of a low-pressure body of the turbomachine 1. Each of the lubrication chambers 162, 164, 166 supplies a corresponding bearing to lubricate and cool this bearing. In particular, when the turbomachine 1 is running, each of the lubrication chambers 162, 164, 166 lubricates the rolling components of the bearing.

[0091] The lubrication chamber of the accessory drive box 170 supplies lubricant to the gears of the accessory drive box 170, in particular to the gears of the turbomachine starter.

[0092] The first, second, third lubrication chambers and the accessory drive case are each arranged downstream of the fourth heat exchanger 168.

[0093] Each of the bearing lubrication chambers 162, 164, 166 and the chamber of the accessory drive case 170 is fluidly connected to the first lubricant return branch 182 which leads lubricant from each of the bearing lubrication chambers 162, 164, 166 and the chamber of the accessory drive case 170 to the reservoir 111.

[0094] More specifically referring to Figure 2 and Figure 6A The pressure of the lubricant at the inlet 211 of the first bypass valve 210 is below a threshold value. The turbomachine 1 is for example in a start-up phase. The pressure supplied by the pumping assembly 112 is not sufficient to supply the main branch 120. The first bypass valve 210 is in the first open position and lubricant is only supplied to the bypass branch 140 through the first lubricant outlet 213. Since no lubricant circulates in the main branch 120, the secondary branch 160 is not supplied with lubricant. The lubricant at the outlet of the bypass branch 140 is supplied to the preferential branch 150 in the direction of the lubrication chamber of the reduction gear 152. The reduction gear 152 is sufficiently cooled and lubricated despite the low flow rate and low pressure of the lubricant in the lubrication system 100.

[0095] More specifically referring to Figure 3 and Figure 6B The pressure of the lubricant at the inlet 211 of the first bypass valve 210 is above a threshold value. The turbomachine 1 is for example at cruising speed. The pressure supplied by the pumping assembly 112 is sufficient to supply the main branch 120. The first bypass valve 210 is in the second open position and lubricant is only supplied to the main branch 120 through the second lubricant outlet 215. The lubricant is cooled in the heat exchangers 121, 122, 124 of the main branch 120. The preferential branch 150 and the secondary branch 160 are each supplied with lubricant from the main branch 120.

[0096] The lubricant circulating in the secondary branch 160 is cooled by the fourth heat exchanger 168. Each of the bearing lubrication chambers 162, 164, 166 and the chamber of the accessory drive case 170 is supplied with lubricant.

[0097] The lubricant at the outlet of the main branch 120 is supplied to the preferential branch 150 in the direction of the lubrication chamber of the reduction gear 152. The reduction gear 152 is sufficiently cooled and lubricated regardless of the pressure drop in the secondary branch 160 and the flow rate of the lubricant in the secondary branch 160.

[0098] Reference is now made in combination with Figure 7 and Figure 8 Operation of the first bypass valve 210 during flight of the turbomachine 1 is described. Figure 7 and Figure 8 Each illustrates a method 300 for lubricating the turbomachine 1 during flight.

[0099] The turbomachine 1 is first in a start-up phase 302, 304, in which the speed of the turbomachine is low. The flow and pressure of the lubricant in the lubrication system 100 increase, but the flow and pressure of the lubricant in the lubrication system are insufficient to supply the secondary branch 160. The pressure of the lubricant at the inlet 211 of the first bypass valve 210 is below a threshold value. The first bypass valve 210 is in a first open position. Only the lubrication chambers of the reduction gear 152, which are in the preferential branch 150, are supplied with lubricant through the bypass branch 140.

[0100] At a first transient operating speed 306 of the turbomachine 1, the flow of lubricant increases and the pressure of the lubricant at the inlet 211 of the first bypass valve 210 exceeds the threshold value. The first bypass valve 210 switches to its second stable open position, in which it supplies the main branch 120 with lubricant. The hydraulic resistance of the main branch 120 is greater than the hydraulic resistance of the bypass valve 140, the pressure drop in the lubrication system 100 suddenly increases at a substantially constant flow of lubricant. The preferential branch 150 and the secondary branch 160 are supplied with lubricant. Each of the bearing lubrication chambers 162, 164, 166, the lubrication chamber of the accessory drive case 170 and the lubrication chambers of the reduction gear 152 are supplied with lubricant.

[0101] At a first cruising speed 308 of the turbomachine 1, the flow of lubricant increases and the pressure of the lubricant in the lubrication system 100 increases. The first bypass valve 210 is in its second stable open position, in which it supplies the main branch 120 with lubricant. The preferential branch 150 and the secondary branch 160 are supplied with lubricant. Each of the bearing lubrication chambers 162, 164, 166, the lubrication chamber of the accessory drive case 170 and the lubrication chambers of the reduction gear 152 are supplied with lubricant.

[0102] At another cruising speed 310, 312 of the turbomachine 1, the flow rate of lubricant is increased and the pressure of the lubricant in the lubrication system 100 is decreased. The pressure at the inlet 211 of the first bypass valve 210 is above the threshold value. The first bypass valve 210 is in its second stable open position in which it supplies lubricant to the main branch 120. The preferential branch 150 and the secondary branch 160 are supplied with lubricant. Each of the bearing lubrication chambers 162, 164, 166, the lubrication chamber of the accessory drive case 170 and the lubrication chamber of the reduction gear 152 are supplied with lubricant.

[0103] At a second transient operating speed 314 of the turbomachine 1, the flow rate of lubricant is decreased and the pressure of the lubricant at the inlet 211 of the first bypass valve 210 is decreased below the threshold value. The first bypass valve 210 switches to its first stable open position in which it supplies lubricant to the bypass branch 140. The hydraulic resistance of the bypass branch 140 is smaller than the hydraulic resistance of the main branch 120, the pressure drop in the lubrication system 100 is suddenly decreased at a substantially constant flow rate of lubricant. Only the lubrication chamber of the reduction gear 152 is supplied with lubricant by the bypass branch 140, the lubrication chamber of the reduction gear being in the preferential branch 150.

[0104] The flow rate of lubricant circulating in the lubrication system 100 at the second transient speed 314 of operation of the turbomachine is lower than the flow rate of lubricant circulating in the lubrication system at the first transient speed 306 of operation of the turbomachine. The bypass device 200 is of the hysteresis operating type, which is particularly advantageous in the present case. This results in a longer time for supplying lubricant to the preferential branch 150 when the turbomachine 1 is starting, which guarantees a reliable supply of lubricant to the lubrication chambers of the reduction gear 152 even if there are any fluctuations in the lubrication system. It also results in a longer time for supplying lubricant to the secondary branch 160 when the turbomachine 1 is approaching a stop, which guarantees a longer time for supplying lubricant to the bearing lubrication chambers 162, 164, 166 of the turbomachine and to the lubrication chamber of the accessory drive case 170 when the stresses of the reduction gear 152 are relatively low.

[0105] Finally, the turbomachine 1 is in a landing and stop phase 316, during which the speed of the turbomachine is low. The flow rate and the pressure of the lubricant in the lubrication system 100 are further decreased and the flow rate and the pressure of the lubricant in the lubrication system are insufficient to supply the secondary branch 160. The first bypass valve 210 is in the first open position. Only the lubrication chamber of the reduction gear 152 is supplied with lubricant by the bypass branch 140, the lubrication chamber of the reduction gear being in the preferential branch 150.

[0106] Figure 4A lubrication system 100 according to a second embodiment of the application is shown. The lubrication system 100 according to the second embodiment mainly differs from the lubrication system according to the first embodiment in the structure of the primary branch 150 and the structure of the secondary branch 160. The following will only describe the differences between the lubrication system 100 according to the second embodiment and the lubrication system 100 according to the first embodiment.

[0107] In the second embodiment, the lubrication chamber of the accessory drive case 170 forms part of the primary branch 150, instead of being in the secondary branch 160. The lubrication chamber of the accessory drive case 170 is arranged in parallel to the lubrication chamber of the reduction gear 152. The primary branch 150 comprises a second non-return device 133 upstream of the lubrication chamber of the accessory drive case 170. This second non-return device 133 comprises a non-return valve. The second non-return device is configured to prevent the lubricant from circulating from the lubrication chamber of the accessory case 170 to the main branch 120.

[0108] The secondary branch 160 comprises a fourth heat exchanger (not shown) and three bearing lubrication chambers 162, 164, 166, which are each arranged in parallel to each other.

[0109] In Figure 4 , the hydraulic resistance of the main branch 120 is schematically shown by the heat exchanger and the lubricant distribution block 125. However, the first non-return device 130 of the main branch is shown. The first non-return device prevents the lubricant from circulating from the lubrication chamber of the reduction gear 152 to the main branch 120.

[0110] Figure 5A 、 Figure 5B 、 Figure 5C and Figure 5D A lubrication system 100 according to a third embodiment of the application is shown. The lubrication system 100 according to the third embodiment mainly differs from the lubrication system according to the first embodiment in the structure of the bypass device 200. The following will only describe the differences between the lubrication system 100 according to the third embodiment and the lubrication system 100 according to the first embodiment.

[0111] The bypass device 200 of the lubrication system 100 according to the third embodiment comprises a first bypass valve 210 and a second bypass valve 220.

[0112] The structure of each of the first bypass valve 210 and the second bypass valve 220 is identical to the structure of the first bypass valve 210 described with reference to the lubrication system 100 according to the first embodiment. The operation of each of the first bypass valve 210 and the second bypass valve 220 during the flight of the turbomachine is similar to the operation of the first bypass valve 210 described with reference to the lubrication system 100 according to the first embodiment. Figure 6A and Figure 6B The structure of each of the first bypass valve 210 and the second bypass valve 220 is identical to the structure of the first bypass valve 210 described with reference to the lubrication system 100 according to the first embodiment. The operation of each of the first bypass valve 210 and the second bypass valve 220 during the flight of the turbomachine is similar to the operation of the first bypass valve 210 described with reference to the lubrication system 100 according to the first embodiment. Figure 7The operation of the bypass valve is described. The lubrication method 300 for turbine 1 during its flight is similar to that described in reference [reference]. Figure 8 The described lubrication method.

[0113] Each of the first bypass valve 210 and the second bypass valve 220 is bistable, having a first stable open position and a second stable open position.

[0114] When the pressure of the lubricant at the inlet 211 of the first bypass valve 210 is below a threshold, each of the first bypass valve 210 and the second bypass valve 220 is in its first stable open position to supply lubricant to the main branch 120.

[0115] When the first bypass valve 210 is in its first stable open position, the plug 202 of the first bypass valve 210 connects the inlet 211 of the first bypass valve to the first bypass outlet 213 of the first bypass valve. The plug 202 of the first bypass valve 210 closes the second lubrication outlet 215 of the first bypass valve 210.

[0116] When the second bypass valve 220 is in its first stable open position, the plug 202 of the second bypass valve 220 fluidly connects the inlet 221 of the second bypass valve 220 to the first bypass outlet 223 of the second bypass valve. The plug 202 of the second bypass valve 220 closes the second lubrication outlet 225 of the second bypass valve 220.

[0117] When the pressure of the lubricant at the inlet 211 of the first bypass valve 210 is strictly higher than the threshold, each of the first bypass valve 210 and the second bypass valve 220 is in its second stable open position to supply lubricant to the bypass branch 140.

[0118] When the first bypass valve 210 is in its second stable open position, the plug 202 of the first bypass valve 210 connects the inlet 211 of the first bypass valve to the second bypass outlet 215 of the first bypass valve. The plug 202 of the first bypass valve 210 closes the first lubrication outlet 213 of the first bypass valve 210.

[0119] When the second bypass valve 220 is in its second stable open position, the plug 202 of the second bypass valve 220 fluidly connects the inlet 221 of the second bypass valve 220 to the second bypass outlet 225 of the second bypass valve. The plug 202 of the second bypass valve 220 closes the first lubrication outlet 223 of the second bypass valve 220.

[0120] The first outlet 213 of the first bypass valve 210 is fluidly connected to the lubricant inlet 221 of the second bypass valve 220 via the first bypass pipe 143.

[0121] When the pressure of the lubricant at the inlet 211 of the first bypass valve 210 is strictly higher than the threshold value, the second outlet 215 of the first bypass valve 210 is fluidly connected to the main duct 123 to directly supply the lubricant to the main branch 120.

[0122] The first outlet 223 of the second bypass valve 220 is fluidly connected to the bypass duct 141 to supply the lubricant only to the priority branch 150 through the bypass branch 140, without favoring the secondary branch 160. In other words, when the pressure value of the lubricant is below the threshold value, the second bypass valve 220 is fluidly connected in series to the first bypass valve 210 to supply the lubricant to the bypass branch 140.

[0123] In the event of a failure of the first bypass valve 210, the second outlet 225 of the second bypass valve 220 is fluidly connected to the main duct 123 to supply the lubricant to the main branch 120. In particular, the second outlet 225 of the second bypass valve is connected to the main branch 120 upstream of the first heat exchanger 121 of the main branch 120.

[0124] In Figure 5A , the hydraulic resistance of the main branch 120 is schematically illustrated by the heat exchanger and the lubricant distribution block 125. However, the first non-return device 130 of the main branch is illustrated. The first non-return device prevents the circulation of lubricant from the lubrication chamber of the reduction gear 152 to the main branch 120. The fourth heat exchanger 168 is not illustrated in this figure.

[0125] More particularly with reference to Figure 5A , each of the first bypass valve 210 and the second bypass valve 220 is in normal operation. The pressure of the lubricant at the inlet 211 of the first bypass valve 210 is below the threshold value. The turbomachine 1 is for example in a start-up phase. The pressure supplied by the pumping assembly 112 is not sufficient to supply the main branch 120. Each of the first bypass valve 210 and the second bypass valve 220 is in the first open position and only supplies the lubricant to the bypass branch 140 through the first lubricant outlet 213 of the first bypass valve 210 and the first lubricant outlet 223 of the second bypass valve 220. Since no lubricant circulates in the main branch 120, the secondary branch 160 is not supplied with lubricant. The lubricant at the outlet of the bypass branch 140 supplies the priority branch 150 in the direction of the lubrication chamber of the reduction gear 152. The reduction gear 152 is sufficiently cooled and lubricated despite the low flow rate and low pressure of the lubricant in the lubrication system 100.

[0126] More particularly with reference to Figure 5BEach of the first bypass valve 210 and the second bypass valve 220 is regularly operated. The pressure of the lubricant at the inlet 211 of the first bypass valve 210 is above the threshold value. The turbomachine 1 is for example at cruising speed. The pressure supplied by the pumping assembly 112 is sufficient to supply the main branch 120. The first bypass valve 210 is in the second open position and supplies lubricant to the main branch 120 only through the second lubricant outlet 215. The inlet 221 of the second bypass valve 220 is not supplied with lubricant. The lubricant is cooled in the heat exchangers 121, 122, 124 of the main branch 120. The preferential branch 150 and the secondary branch 160 are each supplied with lubricant by the main branch 120.

[0127] The lubricant circulating in the secondary branch 160 is cooled by the fourth heat exchanger 168. Each of the bearing lubrication chambers 162, 164, 166 and the chamber of the accessory drive case 170 is supplied with lubricant.

[0128] The lubricant at the outlet of the main branch 120 is supplied to the preferential branch 150 in the direction of the lubrication chamber of the reduction gear 152. The reduction gear 152 is sufficiently cooled and lubricated regardless of the pressure drop in the secondary branch 160 and the flow rate of the lubricant in the secondary branch 160.

[0129] More particularly with reference to Figure 5C The first bypass valve 210 is faulty and locked in its first stable open position. The pressure of the lubricant at the inlet 211 of the first bypass valve 210 is above the threshold value. The turbomachine 1 is for example at cruising speed. The pressure supplied by the pumping assembly 112 is sufficient to supply the main branch 120. The fault of the first bypass valve 210 will tend to cause a lack of lubrication in the secondary branch 160, in particular in each of the bearing lubrication chambers 162, 164, 166 and the accessory drive case 170. Damage to the rolling bearings of the turbomachine and / or to the rolling bearings of the accessory drive case 170 can thus result.

[0130] The first bypass valve 210 is in the first open position and supplies lubricant to the inlet 221 of the second bypass valve 220. The second bypass valve 220 is regularly operated and is in its second stable open position. The inlet 221 of the second bypass valve 220 is fluidically connected to the second outlet 225 of the second bypass valve 220 and to the main branch 120. The preferential branch 150 and the secondary branch 160 are each supplied with lubricant by the main branch 120.

[0131] More particularly with reference to Figure 5D, the second bypass valve 220 is faulty and locked in its first stable open position. The pressure of the lubricant at the inlet 211 of the first bypass valve 210 is above the threshold. The turbomachine 1 is for example at cruising speed. The pressure supplied by the pumping assembly 112 is sufficient to supply the main branch 120. The fault of the second bypass valve 220 can cause a lack of lubrication in the secondary branch 160, in particular in each of the bearing lubrication chambers 162, 164, 166 and in the accessory drive case 170. This can cause damage to the rolling bearings of the turbomachine and / or to the rolling bearings of the accessory drive case 170.

[0132] The first bypass valve 210 is in the second open position and supplies lubricant only to the main branch 120 through the second lubricant outlet 215. The inlet 221 of the second bypass valve 220 is not supplied with lubricant. Thus, the second bypass valve 220 is unable to direct lubricant through the bypass branch 140. The lubricant is cooled in the heat exchangers 121, 122, 124 of the main branch 120. The preferential branch 150 and the secondary branch 160 are each supplied with lubricant by the main branch 120.

[0133] With the lubrication system 100 according to the application, when the flow rate and the pressure of the lubricant are too low to supply the entire lubrication system 100 with lubricant, the reduction gear 152 is supplied with lubricant in a preferential manner with respect to the heat exchangers 121, 122, 124 and the bearing lubrication chambers 162, 164, 166, through the bypass branch 140.

[0134] When the turbomachine is running at low speed, the reduction gear 152 is supplied with lubricant by the bypass branch 140. In particular, when the flow rate and the pressure of the lubricant are sufficient to supply the entire lubrication system 100 with lubricant, in particular when the turbomachine 1 is running at high speed, the reduction gear is supplied with lubricant by the main branch 120.

[0135] Of course, a person skilled in the art can make various modifications to the application just described, without departing from the scope of the application as described.

[0136] In a variant, the turbomachine 1 is a turbomachine with a pair of unfaired counter-rotating propellers. Such a turbomachine 1 is also called "Open Rotor". In this case, the reduction gear 152 is for example configured to rotate the propellers by connecting them in particular to the low-pressure body of the turbomachine.

[0137] In another variant, the turbomachine 1 is a turboprop engine comprising a propeller at the inlet of the turbomachine.

[0138] The structure of each of the hydraulic resistors of the lubrication system can vary. For example, each of these hydraulic resistors can comprise a heat exchanger, a filter, a shut-off valve and / or a flowmeter.

[0139] The structure of the bypass device 200 can vary, in particular as long as the bypass device 200 enables the circulation of lubricant in the main branch 120 at least at some operating speeds of the turbomachine 1.

[0140] In a variant, the bypass device 200 is mechanically controlled, electrically controlled and / or pneumatically controlled. The bypass device 200 can for example be electrically controlled by a digital regulation system of the turbomachine. Such a digital regulation system is also called a “FADEC”.

[0141] In a variant of the third embodiment, the bypass device 200 can comprise a first bypass valve 210 and a second bypass valve 220 arranged fluidically in parallel. However, the arrangement of the bypass device of the lubrication system according to the third embodiment is still more preferred than this variant embodiment since it favors a better distribution of lubricant in the event of a malfunction of a valve among the first bypass valve 210 and the second bypass valve 220.

[0142] The structure of the first bypass valve 210 and / or the structure of the second bypass valve 220 can vary.

[0143] In a variant, the elastic device 204 for acting on at least one bypass valve 210, 220 comprises a tensile spring located in the second chamber 209 and pushing the obturator 202 towards the first open position of this valve.

[0144] In a variant, at least the first bypass valve 210 comprises at least one stable open position between the first stable open position and the second stable open position, in which the obturator 202 of the first bypass valve 210 partially supplies the main branch 120 and partially supplies the bypass branch 140. The first bypass valve 210 can comprise a plurality of stable open positions between the first stable open position and the second stable open position, for example successive stable open positions or a series of discontinuous stable open positions.

[0145] More generally, the first bypass valve 210 and / or the second bypass valve 220 can be of the type of directional control valve other than a three-way two-position hydraulic directional control valve.

[0146] In yet another variant, the pressurized inlet 215 of the first bypass valve 210 can be present in the first chamber 207 of the first bypass valve 210 and / or the pressurized inlet 215 of the second bypass valve 220 can be present in the first chamber 207 of the second bypass valve 220.

[0147] In a variant, the obturator 202 of the first bypass valve 210 comprises a flap valve and / or the obturator 202 of the second bypass valve 220 comprises a flap valve.

[0148] The structure of the second bypass valve 220 is for example different from the structure of the first bypass valve 210.

[0149] In a variant of the second embodiment, the bypass device 200 comprises a second bypass valve 220 in addition to the first bypass valve 210, and the structure of the bypass device 200 is similar, if not identical, to the structure of the bypass device of the lubrication system according to the third embodiment.

[0150] The main branch 120 and the bypass branch 140 each have a variable structure. The preferential branch 150 and the secondary branch 160 each have a variable structure. In particular, the arrangement, the number and the nature of the hydraulic resistors in the lubrication system 100 can vary.

[0151] The number of heat exchangers 121, 122, 124 of the branches can vary. The main branch 120 can comprise at least one filter.

[0152] The bypass branch 140 can comprise at least one heat exchanger.

[0153] The preferential branch 150 can be devoid of a shut-off valve 132 upstream of the reduction gear 152, or in particular devoid of a non-return valve 130 when the shut-off valve 132 also serves as a non-return device.

[0154] In a variant of the second embodiment, the lubrication system 100 can comprise a single non-return valve 130 located between the outlet of the main branch 120 and the inlet of the preferential branch 150.

[0155] In a variant of the second embodiment, the preferential branch 150 can comprise a lubricant distributor, typically a hydraulic directional control valve, for distributing the flow of lubricant between the reduction gear 152 and the accessory drive box 170.

[0156] The number of lubrication chambers 162, 164, 166 of the secondary branch 160 can vary.

[0157] According to a variant embodiment, the lubrication system 100 comprises a device for monitoring the position of the obturator 202 of each bypass valve, the device being configured to monitor the position of the obturator 202.

[0158] The monitoring device is for example configured to determine the lubricant pressure in the main branch 120, for example by means of a first pressure sensor, and to determine the lubricant pressure in the bypass branch 140, for example by means of a second pressure sensor. The monitoring device can monitor the position of the obturator 202 by comparing the lubricant pressure value in the main branch 120 and the lubricant pressure value in the bypass branch 140.

Claims

1. A lubrication system (100) for a turbine (1), the turbine including a reduction gear (152) for driving a module of the turbine (1), the lubrication system comprising: The main branch (120) includes at least one heat exchanger (121, 122, 124, 125). Check devices (130, 133), configured to restrict / prevent lubricant flow from the reduction gear (152) to the main branch (120), the check devices (130, 133) including a check valve, and A bypass branch (140) is arranged in parallel with the main branch (120), and the hydraulic resistance of the bypass branch (140) is lower than that of the main branch (120). The reduction gear (152) is located downstream of the main branch (120) and the bypass branch (140). The lubrication system (100) includes at least one bypass device (200) configured to supply lubricant to the bypass branch (140) when the pressure value of the lubricant is below a threshold.

2. The lubrication system (100) according to claim 1, wherein, The bypass device (200) is configured to supply lubricant to the main branch (120) when the pressure value of the lubricant is strictly greater than the threshold.

3. The lubrication system (100) according to claim 1 or 2, wherein, The bypass device (200) includes: a lubricant inlet (211); a first lubricant outlet (213) fluidly connected to the bypass branch (140); a second outlet (215) fluidly connected to the main branch (120); a stopper (202) configured to at least partially close the first lubricant outlet (213) and / or the second outlet (215); and means (204) for resiliently acting on the stopper, the means for resiliently acting on the stopper being configured to resiliently act on the stopper (202) such that the stopper closes the second outlet (215).

4. The lubrication system (100) according to claim 1 or 2, wherein, The bypass device (200) includes a first bypass valve (210) and / or a second bypass valve (220).

5. The lubrication system (100) according to claim 4, wherein, The bypass device (200) includes a first bypass valve (210) and a second bypass valve (220), the second bypass valve being fluidly connected in series to the first bypass valve (210) such that when the pressure value of the lubricant is below the threshold value, the first bypass valve (210) and the second bypass valve (220) supply lubricant to the bypass branch (140). The first bypass valve (210) is configured to directly supply fluid to the main branch (120) when the pressure of the lubricant is strictly above the threshold.

6. The lubrication system (100) according to claim 5, wherein, The first bypass valve (210) includes: a lubricant inlet (211); a first lubricant outlet (213); a second outlet (215) fluidly connected to the main branch (120) upstream of the heat exchangers (121, 122, 124, 125); a stopper (202) configured to close either the first lubricant outlet (213) or the second outlet (215); and means (204) for resiliently acting on the stopper, the means for resiliently acting on the stopper being configured to resiliently act on the stopper (202) such that the stopper closes the second outlet (215). The closure (202) of the first bypass valve (210) is configured to allow lubricant to flow toward the first lubricant outlet (213) when the lubricant pressure is below the threshold value. The second bypass valve (220) includes: a lubricant inlet (221); a first lubricant outlet (223) fluidly connected to the bypass branch (140); a second outlet (225) fluidly connected to the main branch (120) upstream of the heat exchangers (121, 122, 124, 125); a stopper (202) configured to close either the first lubricant outlet (223) or the second outlet (225); and means (204) for resiliently acting on the stopper, the means for resiliently acting on the stopper being configured to resiliently act on the stopper (202) such that the stopper closes the second outlet (225). The stopper (202) of the second bypass valve (220) is configured to allow lubricant to flow toward the first lubricant outlet (223) when the lubricant pressure is below the threshold. The first lubricant outlet (213) of the first bypass valve (210) is fluidly connected to the lubricant inlet (221) of the second bypass valve (220).

7. The lubrication system (100) according to claim 3, the lubrication system comprising a stopper position monitoring device configured to monitor the position of the stopper (202) of the bypass device.

8. The lubrication system (100) according to claim 1 or 2, wherein, The main branch (120) includes the heat exchangers (121, 122, 124, 125), filters, reservoirs, pumps and / or valves.

9. The lubrication system (100) according to claim 1 or 2, wherein, The main branch (120) and / or the bypass branch (140) are configured to supply lubricant to an accessory drive box (170) for the turbine (1), the accessory drive box for the turbine including a fuel pump, a lubricant pump, a generator and / or a starter for starting the turbine (1).

10. The lubrication system (100) according to claim 2, wherein, The bypass device (200) is hydraulically controlled and / or mechanically controlled by the pressure of the lubricant.

11. The lubrication system (100) according to claim 3, wherein, The occluder (202) is configured to allow lubricant to flow to the first lubricant outlet (213) when the lubricant pressure is below the threshold.

12. The lubrication system (100) according to claim 4, wherein, The first bypass valve (210) and / or the second bypass valve (220) include a sliding portion.

13. The lubrication system (100) according to claim 4, wherein, The first bypass valve (210) is doubly stable, and the first bypass valve (210) includes a first stable open position and a second stable open position. In the first stable open position, the first bypass valve (210) supplies lubricant to the bypass branch (140), and in the second stable open position, the first bypass valve (210) supplies lubricant to the main branch (120).

14. The lubrication system (100) according to claim 4, wherein, The second bypass valve (220) is doubly stable, and includes a first stable open position and a second stable open position. In the first stable open position, the second bypass valve (220) supplies lubricant to the bypass branch (140), and in the second stable open position, the second bypass valve (220) is configured to supply lubricant to the main branch (120).

15. The lubrication system (100) according to claim 8, wherein, The main branch (120) includes a lubricant distributor (169).

16. The lubrication system (100) according to claim 9, wherein, The starter includes a gear system.

17. A turbine (1), said turbine comprising a lubrication system (100) according to any one of claims 1 to 16, wherein, The turbine (1) includes a fan (3) or propeller, a compressor (4, 6) and a turbine (8, 9). The reduction gear (152) is configured to be driven by the turbine (8, 9), which is the low-pressure turbine (9) of the turbine (1).

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