FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
& The Patent Rules, 2003
COMPLETE SPECIFICATION
1.TITLE OF THE INVENTION:
CLOGGING MONITORING IN A STARTER INJECTOR PURGE CIRCUIT FOR A
TURBOMACHINE
2. APPLICANT:
Name: SAFRAN HELICOPTER ENGINES
Nationality: France
Address: 64510 Bordes, France.
3. PREAMBLE TO THE DESCRIPTION:
The following specification particularly describes the invention and the manner in which it
is to be performed:
2
DESCRIPTION
TECHNICAL FIELD
The invention relates to fuel supply systems for an aircraft
5 turbomachine. More precisely, it is concerned with clogging monitoring within the supply
system.
STATE OF PRIOR ART
A fuel supply system for a turbomachine generally comprises a starter
circuit and a main circuit.
10 In a known manner, the starter circuit is only supplied with fuel during
the starting phase. Once the turbomachine starting is made, the starter circuit is purged
to avoid stagnation of fuel. Indeed, a stagnation of fuel could result in coking, that is solid
carbon deposits, which risks clogging the supply system.
One way of purging the starter circuit consists in communicating, after
15 the end of the starting phase, the supply piping of the starter injectors with air at
atmospheric pressure. The fuel present in the injector and the pipings is thus purged
because of the pressure difference between pressurised air from the compressor outlet
and air at atmospheric pressure. Such a phenomenon is referred to as reverse purge,
because purge air circulates in the reverse direction to that of the fuel during the starting
20 phase.
In spite of these precautions, coking occurs, under some conditions, in
the starter circuit and the circuit de purge, which results in a partial or total clogging of
the supply system.
Thus, there is a need for monitoring clogging of the starter circuit and/or
25 the purge circuit.
3
DISCLOSURE OF THE INVENTION
The invention aims at solving at least partially the problems
encountered in solutions of prior art.
In this regard, the object of the invention is a fuel supply system for a
5 turbomachine. The supply system comprises:
- a starter circuit comprising at least one starter injector,
- at least one first hydraulic resistance, et
- a purge circuit comprising a conduit including an aperture opening outside of the
supply system. The purge circuit is configured to flow purge air between the starter
10 injector and the aperture, through the first hydraulic resistance.
According to the invention, the supply system comprises a pressure
representative value measuring means configured to measure a pressure representative
value between the starter injector and the first hydraulic resistance, during a purge air
flow between the starter injector and the first hydraulic resistance.
15 Thus, the pressure representative value enables clogging in the starter
circuit and/or the purge circuit to be detected, before this clogging is such that it results
in a turbomachine downtime.
Once a clogging has been detected, the required maintenance
operations can occur before the downtime of the turbomachine comprising the supply
20 system. These maintenance operations comprise for example scrubbing and/or replacing
components of the supply system.
The invention can optionally include one or more of the following
characteristics combined to each other or not.
It is possible that the purge circuit comprises a second hydraulic
25 resistance located between the first hydraulic resistance and the starter injector. In this
case, the measuring means is configured to measure the pressure representative value
between the first hydraulic resistance and the second hydraulic resistance.
According to a particular embodiment, the first hydraulic resistance
and/or the second hydraulic resistance comprise a valve, a filter and/or a flow restrictor
30 such as a purge conduit shrinkage.
4
According to an advantageous embodiment, the supply system
comprises a clogging monitoring device configured to compare the pressure
representative value with a reference value.
Advantageously, the monitoring device is configured to signal a clogging
5 piece of information, if the absolute value of the difference between the pressure
representative value and the reference value exceeds a first threshold value.
According to an advantageous embodiment, the monitoring device is
configured to signal a clogging piece of information of a first part of the purge circuit,
located upstream of the place of the measurement of the pressure representative value,
10 if:
- a relative value of the difference between the pressure representative value and
the reference value is negative, and that
- the relative value of the difference is lower than a second threshold value.
According to another advantageous embodiment, the monitoring device
15 is configured to signal a clogging piece of information of a second part of the purge
circuit, located downstream of the place of the measurement of the pressure
representative value, if:
- the relative value of the difference between the pressure representative value and
the reference value is positive, and that
20 - the relative value of the difference is higher than a third threshold value.
The terms “upstream” and “downstream” are defined in the purge
circuit with respect to the direction of the purge air flow.
Preferably, the purge circuit is a so-called reverse purge circuit, that is
purge air flows in the reverse direction to that taken by fuel to initiate combustion in the
25 turbomachine. The purge air thereby passes earlier through the starter injectors which
would be particularly likely to be “coked”.
Advantageously, the supply system comprises an alert device configured
to be triggered in case of signalling a clogging piece of information by the monitoring
device.
5
The invention also relates to a turbomachine comprising a supply
system as defined above. Preferably, the turbomachine is an aircraft turbomachine such
as a turbojet engine or a turboprop engine.
The invention is also concerned with a method for monitoring clogging
5 of a fuel supply system as defined above.
Advantageously, the monitoring method comprises a step of
signalling a clogging piece of information, if the absolute value of the difference between
the pressure representative value and the reference value exceeds the first threshold
value,
10 wherein the pressure representative value is measured between the
starter injector and the first hydraulic resistance, during a purge air flow between the
starter injector and the first hydraulic resistance.
According to an advantageous embodiment, the purge air flow occurs
from the starter injector to the aperture, through the first hydraulic resistance.
15 According to another advantageous embodiment, the reference value is
predetermined.
Alternatively, the reference value is determined as a function of at least
one pressure representative value during at least one previous flight of the turbomachine
which is an aircraft turbomachine.
20 BRIEF DESCRIPTION OF THE DRAWINGS
The present invention will be better understood upon reading the
description of exemplary embodiments, given by way of purely indicating and no way
limiting purposes, making reference to the appended drawings in which:
- Fig. 1 is a longitudinal cross-section partial schematic representation of
25 a turbomachine, according to a preferred embodiment of the invention;
- Fig. 2 is a partial schematic representation of a fuel supply system for a
turbomachine, according to a first embodiment of the invention;
- Fig. 3 is a partial schematic representation of a fuel supply system for a
turbomachine, according to a second embodiment of the invention;
6
- Fig. 4 illustrates the implementation of a clogging detection method in
a supply system according to the first or the second embodiment of the invention.
DETAILED DISCLOSURE OF PARTICULAR EMBODIMENTS
5 Identical, similar or equivalent parts of the different figures bear the
same reference numerals so as to facilitate switching from one Fig. to the other.
Fig. 1 represents a turboprop engine 1 which is partially annular about
an axis 3 of power turbine.
The turbomachine 1 includes, from upstream to downstream
10 considering a direction of travel to the axis 3, a propeller 10, a speed reducer 12, case
radial arms 4, a compressor 6, a combustion chamber 7, a high pressure turbine 8 and a
power turbine 9.
The compressor 6, the combustion chamber 7, the high pressure
turbine 8 and the power turbine 9 are surrounded by a case 5. They commonly define in
15 connection with the case 5 a primary stream 13 through which a primary flow flows in the
direction opposite to the turbomachine direction of advance. The flow direction of the
primary flow is represented by the arrow 11. This direction also corresponds to that of
the thrust force of the turbomachine 1 in use.
The gas thrust at the outlet of the combustion chamber 7 causes the
20 compressor 6 and the turbines 8 and 9 to rotate about the axis 3 of the power turbine.
The rotation of the power turbine 9 about its axis 3 is transmitted to the propeller 10
through the speed reducer 12, to rotate it.
Fig. 2 represents a fuel supply system 20 for the combustion chamber 7.
The supply system 20 comprises an upstream circuit 21 comprising a
25 distribution conduit 23 which leads to a node A for separating a main circuit 110 from a
starter circuit 120.
The separating node A is located at a distribution valve 24 which is
configured to distribute fuel between the main circuit 110 and the starter circuit 120. This
7
valve 24 comprises for example a spool (not represented) to make the fuel pressure in the
main circuit 110 equal to that in the starter circuit 120.
The main circuit 110 comprises a valve 114, a supply conduit for the
main injectors 113 and the main injectors 116. These main injectors 116 supply the
5 combustion chamber 2 of the turbomachine 1 with fuel in a steady state condition.
The main circuit 110 also includes a hydraulic resistance 115 comprising
a filter, an exchanger and/or a flow meter. The hydraulic resistance 115 is located
between the valve 114 and the main injectors 116.
The term “hydraulic resistance” is used to define in this document, by
10 analogy with the electricity field, the magnitude from the ratio of the fluid pressure
difference between inlet and outlet of an element of the supply system to the fluid flow
rate passing through the element, as well as the element characterised by this magnitude.
The starter circuit 120 includes an inlet conduit 121 which is connected
at its first end to the separating node A and at its second end, opposite to the first end, to
15 a regulating valve 124. The regulating valve 124 is fluidly connected to the starter
injectors 126.
These starter injectors 126 are in the proximity of spark plugs (not
represented), so as to initiate combustion in the combustion chamber 2. They are distinct
from the main injectors 116. Once the combustion has been initiated in the
20 turbomachine 1, the starter injectors 116 are turned OFF and purge air passes through
them.
The regulating valve 124 comprises a first outlet which opens into a
conduit 123 for supplying the starter injectors and a second outlet which opens into a
purge conduit 131 of a purge circuit 130.
25 The regulating valve 124 includes a closure member movable between a
first opening position where it releases the first outlet and a second opening position in
which it releases the second outlet.
When the closure member is in the first opening position, it causes fuel
to flows from the inlet conduit 121 to the first outlet, towards the starter injectors 126. It
8
prevents air or fuel from being circulated between the starter injectors 126 and the purge
conduit 131.
When the closure member is in the second opening position, it causes
purge air to circulate between the starter injectors 126 and the purge conduit 131. It
5 prevents fuel from flowing from the inlet conduit 121 to the starter injectors 126.
The regulating valve 124 is electrically controlled. The closure member
position is controlled by the electronic regulation system 150 of the turbomachine 1,
through a first electronic regulation module 151 and a solenoid 127.
The electronic regulation system 150 is also known as “FADEC” or “Full
10 Authority Digital Engine Control”. Conventionally, this electronic regulation system 150
comprises an engine calculator with two full authority redundant symmetric ways.
The purge circuit 130 comprises means for injecting hot pressurised air
from the compressor 6, the starter injectors 126, the regulating valve 124 and a flow
restrictor 136.
15 The starter injectors 126, the regulating valve 124, as well as the
conduit 123 for supplying the starter injectors are common to the starter circuit 120 and
the purge circuit 130.
The purge circuit 130 also comprises the purge conduit 131 which opens
into the second outlet of the regulating valve 124. The purge conduit 131 and the flow
20 restrictor 136 are specific to the purge circuit 130.
The purge conduit 131 comprises an aperture 133 which opens outside
of the supply system 20. The aperture 133 is located at the end of the purge conduit
which is opposite to that which opens into the regulating valve 124.
The flow restrictor 136 takes for example the form of a shrinkage of the
25 purge conduit 131. It limits fuel leaks in case of a failure of the regulating valve 124.
The air injecting means inject air from the compressor 6 at the starter
injectors 126 and towards the flow restrictor 136.
The purge circuit 130 is thereby a so-called “reverse” purge circuit, that
is purge air flows in the contrary direction to that taken by fuel to initiate combustion in
30 the turbomachine.
9
In the document, the terms “upstream” and “downstream” are used in
reference to the purge circuit 130, with respect to the flow direction of the purge air and
unless otherwise set out.
The purge air flows from the compressor 6, through the starter
5 injectors 126, the conduit 123 for supplying the starter injectors, the regulating valve 124,
the flow restrictor 136 and the aperture 133 of the purge conduit 131 successively.
Air at the aperture 133 is at a pressure P0 which is that of ambient air. It
is lower than P3 of air from the compressor 6 which is at the starter injectors 126.
The supply system 20 also comprises a pressure sensor 141 which plays
10 the role of pressure representative value measurement means. The pressure
representative value Pm is a pressure measurement value.
The pressure sensor 141 measures the pressure in the conduit 123 for
supplying the starter injectors 126 in the place which is represented in Fig. 2 by a first
measurement node B. This first measurement node B is located between the starter
15 injectors 126 and the regulating valve 124 which is a hydraulic resistance for purge air.
The starter injectors 126 are upstream of the first measurement node B,
relative to the purge air flow in the purge circuit 130. Therefore, they form an upstream
part 132 of the purge circuit 130.
The regulating valve 124 and the flow restrictor 126 are downstream of
20 the first measurement node B, relative to the purge air flow in the purge circuit 130. They
form a downstream part 134 of the purge circuit 130.
The second embodiment, which is represented in reference to Fig. 3, is
distinguished from the first embodiment by the place of the measurement of the
pressure representative value Pm.
25 In the second embodiment, the pressure sensor 141 measures pressure
in the purge conduit 131 between the flow restrictor 136 and the regulating valve 124, at
a place which is represented by the second measurement node C in Fig. 3.
The flow restrictor 136 plays the role of the first hydraulic resistance,
the regulating valve 124 plays the role of the second hydraulic resistance. The
10
measurement of the pressure representative value Pm thereby occurs between this first
hydraulic resistance and this second hydraulic resistance.
The starter injectors 126 and the regulating valve 124 are upstream of
the second measurement node C, relative to the purge air flow in the purge circuit 130.
5 Therefore, they form an upstream part 132 of the purge circuit 130.
The flow restrictor 136 is downstream of the second measurement
node C, relative to the purge air flow in the purge circuit 130. It forms a downstream
part 134 of the purge circuit 130.
In the first and in the second embodiment, the signal emitted by the
10 pressure sensor 141 is transmitted to a second electronic control module 152 and to the
electronic regulation system 150.
The second control module 152 and the electronic regulation
system 150 comprise a memory and means for processing the pressure representative
value Pm.
15 They form a monitoring device 150 for monitoring clogging of the supply
system 20, in particular the purge circuit 130. The monitoring device 150 is for signalling a
clogging piece of information to an alert device 154.
The clogging piece of information indicates a clogging start in the supply
system 20 and/or a statistically significant risk that the turbomachine 1 is in downtime
20 with a predetermined number of flights because of clogging.
The alert device 154 is triggered in case of signalling a clogging piece of
information by the monitoring device 150. It emits a light, tactile and/or sound alert, in
order to inform a pilot and/or a maintenance operator of a clogging risk in time.
The method for monitoring a clogging of the supply system 20, in
25 particular of the purge circuit 130 is illustrated in Fig. 4.
The pressure representative value Pm is first measured in the supply
system, at the first node B and/or the second node C, in a measuring step 202. The
measuring step 202 occurs during a purge air flow from the starter injectors 126 to the
aperture 133, through the regulating valve 124 and the flow restrictor 136.
11
Then, the monitoring device 150 compares the pressure representative
value Pm with a reference value Pref, in a comparing step 204.
The reference value Pref is either predetermined, or it corresponds to an
old, possibly averaged, value, of the pressure representative value Pm.
5 When it is predetermined, the reference value Pref corresponds to a
pressure nominal value in the conduit 123 for supplying the starter injectors.
When it is determined as a function of the pressure change in the supply
conduit 123, the reference value Pref is set from at least one pressure representative
value Pm during at least one previous flight of the turbomachine 1.
10 The monitoring device 150 then signals a clogging piece of information if
the difference ε between the pressure representative value Pm and a reference value Pref
is high enough, in a step 207.
The monitoring device 150 signals a clogging piece of information, if the
absolute value of the difference ε between the pressure representative value Pm and the
15 reference value Pref exceeds a first threshold value S1. This condition is called a “first
condition”.
The monitoring device 150 does not necessarily calculate the absolute
value of the difference ε, to check the first condition. It is sufficient for it to calculate for
example the relative value of the difference ε between the pressure representative
20 value Pm and the reference value Pref.
The monitoring device 150 checks whether a significant decrease in the
pressure representative value Pm is detected, by comparison with the reference value Pref,
in step 209. This condition is called a “second condition”.
The second condition amounts to checking whether:
25 - a relative value of the difference ε between the pressure
representative value Pm and the reference value Pref is negative and that
- the relative value of the difference ε is lower than a second threshold
value S2.
In the first and second embodiments, the second threshold value S2 has
30 an opposite value to that of the first threshold value S1.
12
The monitoring device 150 also checks whether a significant increase in
the pressure representative value Pm is detected, by comparison with the reference
value Pref, in step 209. This condition is called a “third condition”.
The third condition amounts to checking whether:
5 - the relative value of the difference ε between the pressure
representative value Pm and the reference value Pref is positive and that
- the relative value of the difference ε is higher than a third threshold
value S3.
In the first and second embodiments, the third threshold value S3 is
10 equal to that of the first threshold value S1.
Checking the second condition and the third condition can be made at
the same time as checking the first condition, since the absolute values of the
thresholds S1, S2 and S3 are identical. In other words, steps 207 and 209 can be the same.
When the second condition is met, the monitoring device 150 has
15 noticed a significant decrease in the pressure representative value Pm. Thereby, it signals
a piece of information of clogging of the upstream part 132 of the purge circuit, that is
upstream of the place of the measurement of the pressure representative value Pm
relative to the purge air flow.
The alert device 154 alerts the pilot and/or a maintenance operator of a
20 clogging risk of the starter injectors 126, in a step 210 and in reference to the first
embodiment.
The alert device 154 alerts the pilot and/or a maintenance operator of a
clogging risk of the starter injectors 126 and/or the regulating valve 124, in a step 210 and
in reference to the second embodiment.
25 When the third condition is met, the monitoring device 150 has noticed
a significant increase in the pressure representative value Pm. Then, it signals a piece of
information of clogging of the downstream part 134 of the purge circuit, that is
downstream of the place of the measurement of the pressure representative value Pm
relative to the purge air flow.
13
The alert device 154 alerts the pilot and/or a maintenance operator of a
clogging risk of the regulating valve 124 and/or the flow restrictor 136, in a step 212 and
in reference to the first embodiment.
The alert device 154 alerts the pilot and/or a maintenance operator of a
5 clogging risk of the flow restrictor 136, in a step 212 and in reference to the second
embodiment.
Of course, various modifications can be made by those skilled in the art
to the invention just described without departing from the scope of the invention.
The flow restrictor 136 is a hydraulic resistance which can take a
10 different form.
The pressure representative value measuring means 141 can comprise a
temperature sensor, in addition to or in place of the pressure sensor. The pressure
representative value Pm is thereby a temperature measurement. In this case, the pressure
at the measurement nodes B and/or C is determined using an air equation of state from
15 this temperature measurement.
The supply system 20 can both make measurements of pressure
representative values Pm at the first measurement node B and at the second
measurement node C. In this case, the monitoring device 150 enables a clogging risk of
the regulating valve 124 to be better discriminated from a clogging risk of the
20 injectors 126 and a clogging risk of the flow restrictor 136.
The pressure representative value Pm is preferably measured upstream
of the flow restrictor 136 in the purge circuit 130, to make a clogging detection easier.
The second threshold S2 and/or the third threshold S3 can have different
values from that opposite to the first threshold S1 and to the first threshold S1, in
25 particular if the pressure sensor 141 more readily detects a pressure increase or a
pressure decrease or vice versa.
The embodiments represented in Figs. 2 and 3 comprise a purge
circuit 130 with a so-called “reverse” purge but of course, the purge air could circulate in
the other direction in the purge circuit 130. The fuel and purge air would thereby circulate
30 in the same direction in the purge circuit 130 and in the starter circuit 120.
14
Thereby, the purge air would flow from the compressor 6, through the
aperture 133, the flow restrictor 136, the regulating valve 124 and the starter injectors
126 successively.
In such a configuration, the upstream 132 and downstream 134 parts
5 would be exchanged with respect to the nodes B and/or C for measuring the pressure
representative value.
When the second condition is met after a measurement at the first
node B, the alert device 154 alerts the pilot and/or a maintenance operator of a clogging
risk of the flow restrictor 136 and/or of the regulating valve 124, in a step 210.
10 When the second condition is met after a measurement at the second
node C, the alert device 154 alerts the pilot and/or a maintenance operator of a clogging
risk of the flow restrictor, in a step 210.
When the third condition is met after a measurement at the first
node B, the alert device 154 alerts the pilot and/or a maintenance operator of a clogging
15 risk of the starter injectors 126, in a step 212.
When the third condition is met after a measurement at the second
node C, the alert device 154 alerts the pilot and/or a maintenance operator of a clogging
risk of the regulating valve and/or the starter injectors 126, in a step 212.
15
WE CLAIM:
1. A fuel supply system (20) for a turbomachine (1), comprising:
a starter circuit (120) comprising at least one starter injector (126),
5 at least one first hydraulic resistance (124, 136),
a purge circuit (130) comprising a conduit (131) including an aperture (133) opening
outside of the supply system (20),
wherein the purge circuit (130) is configured to flow purge air between the starter
injector (126) and the aperture (133), through the first hydraulic resistance (124, 136),
10 characterised in that the supply system (20) comprises a pressure
representative value measuring means (141) configured to measure a pressure
representative value (Pm) between the starter injector (126) and the first hydraulic
resistance (124, 136), during a purge air flow between the starter injector (126) and the
first hydraulic resistance (124, 136).
15
2. The supply system (20) according to the preceding claim, wherein
the purge circuit (130) comprises a second hydraulic resistance (124) located between the
first hydraulic resistance (136) and the starter injector (126),
wherein the measuring means (141) is configured to measure the pressure
20 representative value (Pm) between the first hydraulic resistance (136) and the second
hydraulic resistance (124).
3. The supply system (20) according to any of the preceding claims,
wherein the first hydraulic resistance (136) and/or the second hydraulic resistance (124)
25 comprise a valve, a filter and/or a flow restrictor such as a purge conduit shrinkage.
4. The supply system (20) according to any of the preceding claims,
comprising a clogging monitoring device (150) configured to compare the pressure
representative value (Pm) with a reference value (Pref).
30
16
5. The supply system (20) according to the preceding claim, wherein
the monitoring device (150) is configured to signal a clogging piece of information, if the
absolute value of the difference (ε) between the pressure representative value (Pm) and
the reference value (Pref) exceeds a first threshold value (S1).
5
6. The supply system (20) according to any of claims 4 and 5, wherein
the monitoring device (150) is configured to signal a clogging piece of information of a
first part (132) of the purge circuit, located upstream of the place of the measurement of
the pressure representative value (Pm), if:
10 a relative value of the difference (ε) between the pressure representative value (Pm)
and the reference value (Pref) is negative and
the relative value of the difference (ε) is lower than a second threshold value (S2).
7. The supply system (20) according to any of claims 4 to 6, wherein
15 the monitoring device (150) is configured to signal a clogging piece of information of a
second part of the purge circuit (130), located downstream of the place of the
measurement of the pressure representative value (Pm), if:
the relative value of the difference (ε) between the pressure representative
value (Pm) and the reference value (Pref) is positive and
20 the relative value of the difference (ε) is higher than a third threshold value (S3).
8. The supply system (20) according to any of claims 5 to 7, comprising
an alert device (154) configured to be triggered in case of signalling a clogging piece of
information by the monitoring device (150).
25
9. A method for monitoring clogging of a fuel supply system (20)
according to any of claims 5 to 8,
characterised in that it comprises a step of signalling (210, 212) a
clogging piece of information, if the absolute value of the difference (ε) between the
17
pressure representative value (Pm) and the reference value (Pref) exceeds the first
threshold value (S1),
wherein the pressure representative value (Pm) is measured
between the starter injector (126) and the first hydraulic resistance (124, 136), during a
5 purge air flow between the starter injector (126) and the first hydraulic resistance (124,
136).
10. The monitoring method according to the preceding claim, wherein
the purge air flow occurs from the starter injector (126) to the aperture (133), through
10 the first hydraulic resistance (124, 136).
11. The monitoring method according to any of claims 9 and 10,
wherein the reference value (Pref) is predetermined or wherein the reference value (Pref)
is determined as a function of at least one pressure representative value (Pm) during at
15 least one previous flight of the turbomachine (1) which is an aircraft turbomachine.