1
FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
& The Patent Rules, 2003
COMPLETE SPECIFICATION
1.TITLE OF THE INVENTION:
METHOD FOR CONTROLLING THE SUPPLY OF FUEL TO A COMBUSTION
CHAMBER OF A TURBINE ENGINE, FUEL SUPPLY SYSTEM AND TURBINE
ENGINE
2. APPLICANT:
Name: SAFRAN AIRCRAFT ENGINES
Nationality: France
Address: 2 boulevard du Général Martial Valin, 75015 PARIS, 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 is directed to the field of turbomachines 5 and supply circuit
of such a turbomachine.
The invention thus relates to a method for controlling fuel supply of a
combustion chamber of a turbomachine, a supply circuit and a turbomachine.
STATE OF PRIOR ART
10 Generally, a combustion chamber of a turbomachine is supplied with fuel
by injection devices designed to spray fuel into the combustion chamber. These same
injection devices, forming an injection system of the combustion chamber, are supplied by
a fuel supply circuit of the turbomachine.
Injection devices have at least one first and a second part configured to
15 allow supply to the combustion chamber according to a respective supply type. The first
part thus corresponds to a pilot supply type dedicated to low speed and the second part
corresponds to a main supply type dedicated to high speed and for optimising chamber
combustion at these high speeds so as to reduce the pollution generated. These first and
second parts can:
20 - either each consist of injection devices dedicated to the corresponding
supply type,
- or each consist of a part of each injection device which is dedicated to
the corresponding supply type.
Irrespective of the configuration of these injection devices, the fuel
25 supply distribution of each of the first and the second parts is provided by the fuel supply
circuit.
3
Thus, for this the supply circuit includes a pilot injection line and a main
injection line between which the fuel supply of the combustion chamber is distributed, the
pilot injection line supplying the first part of the injection devices and the main injection
line supplying the second part of the injection devices with fuel. Fuel supply of the injection
chamber is thus distributed between the pilot injection line and the main 5 injection line.
In order to limit the pollution generated by turbomachines, fuel supply
distribution of the pilot and main injection lines is, for different operating phases of the
turbomachine, whether in flight or on the ground, particularly regulated.
Regarding the changes in fuel supply distribution of the pilot and main
10 injection lines, between its different operating phases, regulations are less strict and only
require that this switch occurs during a predetermined period of time.
In order to exemplify such a switch, it has been provided in Figs. 1A to 1C
an example of fuel supply transition upon accelerating the turbomachine switching it from
low speed to high speed. As shown in Fig. 1B, in this example, the supply distribution
15 switches from a 100% first distribution value of fuel supply on the pilot injection line, the
main injection line being substantially not supplied with fuel, to a 5% second distribution
value of fuel supply on the injection line, the main injection line being supplied with 95% of
the fuel.
Thus, in accordance with the teachings of document FR 3025590 A1 and
20 as illustrated in Figs. 1A to 1C, it is known to make such switching abruptly.
It can thus be seen in these figures that, during such a speed
change 501 (R in Fig. 1A), the fuel injection flow rate 502 (Db in Fig. 1A) is gradually
increased until it reaches, at the same time as speed 501, a maximum. Switching 511 the
distribution 510 (Ds in Fig. 1B) from the first value to the second value is performed
25 abruptly when the speed reaches its maximum. As shown in Fig. 1C, this distribution 510
switching from the first value to the second value results itself in a sharp drop 521 in the
pressure 520 (P in Fig. 1C) in the fuel supply circuit.
Such a pressure drop is due to the fact that, for a same flow rate, head
losses are more significant for the first part of the injection devices than for the second part
30 of the injection devices. Thus as a result, switching from the first value to the second value
4
of fuel supply distribution leads to a significant reduction in head losses generated by the
relevant injection line, and therefore a decrease, at an equal fuel flow rate, in the pressure
of the fuel supply circuit.
However, such a pressure drop can be particularly detrimental to the
operation of the turbomachine when it occurs during some operating 5 phases of the
turbomachine, such as the acceleration phase illustrated in Figs. 1A to 1C, or phases of
ingestion of external elements, such as a bird, rain water/snow and hail. These different
phases require keeping pressure in the supply circuit.
Indeed, in a turbomachine, high pressure of the fuel supply circuit is also
10 used to supply hydraulic cylinders, controlling movable members useful for engine
operability, for example, variable angle stator vanes or bleed valves of a compressor. A
pressure drop in the fuel supply circuit has therefore a direct consequence on the hydraulic
muscle supplying these cylinders and therefore on the capability to actuate movable
members, whereas the loads being applied to the movable members can be increasing. It
15 is therefore necessary, in order to enable the turbomachine to properly operate, to provide
increased dimensioning of hydraulic cylinders supplied by the fuel circuit of the
turbomachine, in order to be able to provide sufficient loads with however less hydraulic
muscle due to the pressure drop related to the change in fuel supply distribution.
Thus, methods for controlling fuel supply currently implemented are not
20 adapted with respect to fuel distribution change phases since they can result in a pressure
drop in the fuel supply circuit of the turbomachine. This pressure drop, in order not to be
detrimental to the operation of the turbomachine, may require an increased dimensioning
of hydraulic cylinders, especially an increase in their diameter.
DISCLOSURE OF THE INVENTION
25 The invention aims at solving this drawback and thus its purpose is to
provide a method for controlling fuel supply of a turbomachine for ensuring an adequate
pressure of the fuel supply circuit during a change in fuel distribution without requiring an
increased dimensioning of hydraulic cylinders, as is the case for turbomachines of prior art.
5
The invention relates to a method for controlling fuel injection in a
combustion chamber of a turbomachine, the turbomachine comprising a fuel supply circuit
of an injection system of the combustion chamber, said supply circuit comprising a pilot
injection line and a main injection line between which the fuel supply of the combustion
chamber 5 is distributed,
controlling method in which, a transition of the supply distribution
between the pilot injection line and the main injection line from a first distribution value to
a second distribution value is performed over a corresponding period of time, the supply
distribution having the second distribution value at the end of the corresponding period of
10 time,
the controlling method comprises, for a transition of the supply
distribution from a first distribution value to a second distribution value for which fuel
distribution from the pilot injection line is reduced relative to that of this same pilot
injection line for the first distribution value, the following steps of:
15 a) determining at least one minimum value to be maintained of a
pressure quantity of the supply circuit for at least one part of the period of time,
b) determining at least one hydraulic quantity of the supply circuit,
c) calculating, from the determined hydraulic quantity of the supply
circuit, a calculated distribution value of fuel supply corresponding to the minimum value
20 to be maintained of the pressure quantity, the distribution value calculated being chosen
from a range of values defined between the first distribution value and the second
distribution value, said range of values including the first and second distribution values,
d) switching the fuel supply distribution to the distribution value
calculated,
25 at least steps b) to d) being successively repeated for the whole duration
of the corresponding period of time.
With such a method, switching from the first to the second value during
the corresponding period of time, that is the predetermined period of time during which
switching from the first to the second value has to occur, is made so as to keep minimum
30 pressure in the supply circuit. With such a pressure kept, actuating the cylinders is provided
6
without necessarily having an increased dimensioning of cylinders as is the case in methods
of prior art.
During step c) of calculating, from the determined hydraulic quantity of
the supply circuit, a calculated distribution value of fuel supply corresponding to the
minimum value to be maintained of the pressure quantity, the calculated 5 distribution value
can be intermediate between the first distribution value and the second distribution value.
It will be noted that the minimum value to be maintained of a pressure
quantity of the supply circuit for at least one part of the period of time can be a minimum
pressure value necessary to actuate at least one part of the hydraulic actuators of the
10 turbomachine.
Step c) of calculating the calculated distribution value of fuel supply may
include the following sub-steps of:
- calculating from the determined hydraulic quantity of the supply
circuit and from a current value of the pressure quantity of the supply circuit, a current
15 value of the pressure quantity of the supply circuit
- comparing the calculated current value of the pressure quantity of
the supply circuit with the determined minimum value to be maintained of the pressure
quantity of the supply circuit,
- calculating, from the comparison result, the calculated distribution
20 value of fuel supply corresponding to the minimum value to be maintained.
Step c) of calculating the calculated distribution value of fuel supply can
consist of a step of calculating said calculated distribution value of fuel supply from the at
least one determined hydraulic quantity of the fuel supply circuit and from the determined
minimum value to be maintained of the pressure quantity of the supply circuit.
25 This way, with these two alternatives of step c), it is possible to obtain a
quick change in the supply distribution while ensuring that the pressure in the supply circuit
remains sufficient to guarantee proper operation of the hydraulic cylinders.
The pressure quantity can be chosen from a pressure value of the supply
circuit and a value of force developed by a cylinder supplied by the supply circuit, and the
7
hydraulic quantity of the supply circuit is a value of the fuel supply flow rate of the injection
chamber.
Upon successively repeating steps b) to d), step a) can also be repeated,
this being for determining a minimum value to be maintained of the pressure quantity of
the fuel supply circuit for a fraction of period of the corresponding 5 period of time.
In this way, the supply system is able to provide proper actuation for the
whole corresponding period of time irrespective of upgrades of the turbomachine
configuration.
The invention further relates to a fuel supply circuit for a turbomachine,
10 the fuel circuit including:
- a pilot injection line for supplying a pilot part of an injection system
of a combustion chamber of the turbomachine,
- a main injection line for supplying a main part of the injection system
of the combustion chamber,
15 - a fuel supply distributing device configured to control fuel
distribution between the pilot injection line and the main injection line,
- a control unit able to control the supply distributing device and to
make a measurement of some hydraulic quantities of the supply circuit,
the control unit being configured to control the distributing system so as
20 to provide transition of the supply distribution between the pilot injection line and the main
injection line from a first distribution value to a second distribution value over a
corresponding period of time, the supply distribution having the second distribution value
at the end of the corresponding period of time.
The control unit is further configured to, upon controlling the fuel
25 distributing system to perform a transition of supply distribution from a first distribution
value to a second distribution value for which the fuel distribution of the pilot injection line
is reduced relative to that of this same pilot injection line for the first distribution value,
implement the following steps of:
8
a) determining at least one minimum value to be maintained of a
pressure quantity of the supply circuit for at least one part of the corresponding period of
time,
b) determining at least one hydraulic quantity of the supply circuit,
c) calculating, from the determined hydraulic quantity 5 of the supply
circuit, a calculated distribution value of fuel supply corresponding to the minimum value
to be maintained of the pressure quantity, the calculated distribution value being chosen
from a range of values defined between the first distribution value and the second
distribution value, said range of values including the first and second distribution values,
10 d) switching the supply distribution to the calculated supply distribution
value,
the control unit being further configured to successively repeat steps b)
to d) for the whole duration of the corresponding period of time.
Such a supply circuit allows implementation of a supply method according
15 to the invention thus benefiting from advantages related thereto.
The control unit can further be configured so that, during step c) of
calculating, from the determined hydraulic quantity of the supply circuit, a calculated
distribution value of fuel supply corresponding to the minimum value to be maintained of
the pressure quantity, the calculated distribution value is intermediate between the first
20 distribution value and the second distribution value.
The control unit can include:
- a minimum pressure determining module configured to determine a
minimum value to be maintained of the pressure quantity of the supply circuit for at least
one part of the corresponding period of time,
25 - a calculation module configured to calculate from a determined
hydraulic quantity of the supply circuit and from a current value of the fuel supply
distribution, a current value of the pressure quantity of the supply circuit,
- a comparison module configured to compare the calculated current
value of the pressure quantity of the supply circuit with the determined minimum value to
30 be maintained of the pressure quantity of the supply circuit, and to calculate, from the
9
comparison result, a calculated distribution value of fuel supply corresponding to the
determined minimum value to be maintained of the pressure quantity of the supply circuit.
The control unit is a turbomachine calculator.
The invention relates to a turbomachine comprising an injection
chamber, said injection chamber comprising an injection system, 5 said turbomachine
further comprising a fuel supply circuit according to the invention supplying the injection
system with fuel.
Such a turbomachine benefits from advantages related to the fuel
supply circuit it includes.
10 BRIEF DESCRIPTION OF THE DRAWINGS
The present invention will be better understood upon reading the
description of exemplary embodiments, given by way of purely indicative and in no way
limiting purposes, made with reference to the appended drawings in which:
- Figs. 1A to 1C graphically illustrate the variation in some parameters
15 of a turbomachine and supply circuit of prior art equipping said turbomachine when said
turbomachine switches from low speed to high speed, Fig. 1A depicting the variation over
time in the turbomachine speed and the flow rate of fuel injected into the combustion
chamber, Fig. 1B depicting the variation over time in fuel supply distribution between a
pilot supply line and a main supply line,
20 - Fig. 2 is an axial cross-section schematic view of a turbomachine for
an aircraft according to a first embodiment of the invention;
- Fig. 3 is a schematic view of elements making up a fuel supply circuit
of a turbomachine according to the first embodiment,
- Fig. 4 is a block diagram of a control unit according to the first
25 embodiment of the invention,
- Fig. 5 is a block diagram of a control unit according to a second
embodiment,
- Figs. 6A and 6B illustrate a comparison between a transition in fuel
distribution according to prior art and a transition in fuel distribution according to the
10
invention with respectively, in Fig. 6A, the variation over time in fuel supply distribution
and, in Fig. 6B, in the pressure of the fuel supply circuit.
Identical, similar or equivalent parts of the different figures bear the same
reference numerals so as to facilitate switching from one figure to another.
Different parts represented in the figures are not necessarily 5 drawn to a
uniform scale, to make the figures more legible.
Different possibilities (alternatives and embodiments) should be
understood as being not mutually exclusive and combinable with each other.
DETAILED DISCLOSURE OF PARTICUAR EMBODIMENTS
10 Fig. 2 illustrates a turbomachine, for example a turbofan engine 10 for an
aircraft, generally including a fan 12 arranged to suck an airflow F1 being divided
downstream of the fan into a primary flow F2 supplying a core of the turbofan and a
secondary flow F3 bypassing this core and for providing theoretically most of the thrust.
The turbofan core includes, in a well known manner, a low pressure
15 compressor 14, a high pressure compressor 16, a combustion chamber 18 for example of
the annular type, a high pressure turbine 20 and a low pressure turbine 22. The turbofan is
shrouded by a nacelle 24 surrounding the flowing space 26 of the secondary flow. The
turbofan rotors are rotatably mounted about a longitudinal axis 28 of the turbofan.
The invention is however applicable to any turbomachine type.
20 The combustion chamber 18 is supplied with fuel by a fuel supply
circuit 100 schematically illustrated in Fig. 3 and fuel injection devices 181, generally called
injectors. Each of the injection devices comprises a fuel exhaust duct, not illustrated, able
to spray fuel into the combustion chamber, for example through corresponding holes, not
illustrated, provided in a bottom wall of the combustion chamber. To that end, the fuel
25 exhaust ducts directly or indirectly open into the combustion chamber 18.
As described in connection with prior art, these injection devices 181
have at least one first and one second part, not represented, configured to allow supply of
the combustion chamber 18 according to a respective supply type. The first part thus
corresponds to a pilot supply type dedicated to low speed and the second part corresponds
11
to a main supply type dedicated to high speed and adapted to optimise the combustion
speed of the chamber at these high speeds so as to reduce the pollution generated. These
first and second parts can:
- either each consist of injection devices 181 dedicated to the
corresponding 5 supply type,
- or, according to a preferential possibility of the invention, each consist
of a part of each injection device 181 which is dedicated to the corresponding supply type.
According to the latter possibility, each injection device 181 can, for
example, include two types of holes supplied by a corresponding exhaust duct:
10 - a central hole of a relatively significant dimension forming, with the
corresponding exhaust duct, the first part of said injection device 181,
- holes peripheral to the central hole and distributed about this same
central hole, these peripheral holes forming with the corresponding exhaust duct the
second part of said injection device 181.
15 Irrespective of the configuration of these injection devices 181, the fuel
supply distribution of each of the first and the second parts is provided by the fuel supply
circuit 100.
The fuel supply circuit 100 comprises, as shown in Fig. 3:
- a fuel pressurising system 110 able to supply with fuel the fuel supply
20 circuit 100 from fuel supplied by the aircraft fitted with the turbomachine, and to control
the actuation of cylinders 40 of the turbomachine,
- a flowmeter 120 adapted to measure the flow rate of fuel passing in
the fuel supply circuit 100, the flow rate forming a hydraulic quantity of the supply
circuit 100,
25 - a fuel supply distribution device 130 configured to control fuel
distribution to the first and second parts of the injection devices 181,
- a pilot injection line 141 configured to supply with fuel the first part
of the injection devices 181,
- a main injection line 142 configured to supply with fuel the second
30 part of the injection devices 181,
12
- a control unit 30 able to control the distribution device 130 and to
make a measurement of some hydraulic quantities of the supply circuit 100, especially the
fuel flow rate in the supply circuit 100 from the flowmeter 120.
Thus, in accordance with the present embodiment, the hydraulic quantity
of the supply circuit 100 can be the fuel flow rate in the supply circuit 5 upstream of the
supply distribution device 130. According to this possibility, this hydraulic quantity of the
supply circuit 100 can be the flow rate at the pipe supplying the cylinders 40. Such a value
enables a proper estimation of hydraulic muscle of said cylinders 40 to be obtained.
Of course, the control unit 30 can also be able to control the distribution
10 device 130 and to make a measurement of a hydraulic quantity other than the fuel flow
speed, for example the fuel pressure in the supply circuit 100 using a pressure gauge.
Alternatively, the measured hydraulic quantity can consist of the fuel distribution between
the pilot injection line and the main injection line. For example, if the distribution device is
formed by a valve provided with a movable cover as a sliding spool the position of which
15 governs distribution, measuring fuel distribution can be made by measuring the position of
the spool. According to another possibility of the invention, this measurement of
distribution can be performed using two flowmeters respectively disposed in the pilot
injection line 141 and main injection line 142.
The pilot injection line 141 is configured to supply with fuel the first part
20 of injection devices 181 and the main injection line 142 is configured to supply with fuel
the second part of injection devices 181. It will also be noted that the supply distribution
device 130 is configured to control fuel distribution between the pilot injection line 141 and
main injection line 142.
According to an advantageous configuration of the invention, the control
25 unit 30 is formed by a calculator of the turbomachine. As an alternative, the control unit 30
can be formed by an electronics solely dedicated to the control of the supply circuit 100.
In the rest of this document, for the purpose of simplicity, a transition of
the supply distribution between the pilot injection line 141 and the main injection line 142
from a first distribution value to a second distribution value for which the supply
30 distribution of the pilot injection line 141 in the second value is reduced relative to that of
13
this same pilot injection line 141 for the first distribution value, is referred to as “reduction
transition of pilot distribution”.
Fig. 4 illustrates a block diagram of the control unit 30. Thus the control
unit 30 includes:
- a stabilised phase regulation module 310 5 adapted to control
different elements of the fuel supply circuit 100 apart from the reduction transition phases
of pilot distribution, this stabilised phase regulation module 310 being configured to
provide control of the fuel supply distribution between the pilot injection line 141 and the
main injection line 142 which is similar to control modules of prior art,
10 - a module 320 for determining the minimum pressure to be
maintained of a pressure quantity of the fuel supply circuit, such as the pressure of the
supply circuit 100, during a reduction transition phase of the pilot distribution from a
configuration of the turbomachine, said configuration especially including speed state
information of the turbomachine 402, position information 403 for the cylinders 40 and
15 control information 404 for moving the cylinders 40, said minimum pressure to be
maintained forming a minimum value to be maintained,
- a calculation module 330 configured to calculate from the hydraulic
quantity of the supply circuit 100 and from a current value of the fuel supply distribution,
a current value of the pressure quantity of the supply circuit 100,
20 - a comparison module 340 configured to compare the determined
value of the pressure quantity of the supply circuit 100 and the calculated current value of
the pressure quantity of the supply circuit 100 and to calculate, from the comparison result,
a calculated distribution value of fuel supply corresponding to the minimum value to be
maintained,
25 - a selecting system 350 configured to, from at least one state
value 411 of the turbomachine characteristic of a reduction transition of distribution, select
a control value of the supply distribution from that provided by the stabilised phase
regulation module 310 and the value calculated by the comparison module 340.
Each of the modules 310, 320, 330, 340 is provided either by a dedicated
30 circuit of the control unit 30, or by a software module set up on said control unit 30.
14
According to a possibility of the invention, the pressure quantity of the
supply circuit 100 can be a pressure value of the supply circuit as well as a value of force
developed by a cylinder 40 supplied by the supply circuit 100.
It will be noted that the state value 411 is a characteristic quantity of a
state corresponding to a reduction transition of pilot distribution. 5 According to a
conventional configuration, the state value can take a value 1 (or 0) for the whole duration
of the reduction transition of pilot distribution and a value 0 (or 1) outside the same.
According to another possibility, this state value 411 can include a plurality of states
corresponding to states of the turbomachine 18 for which a reduction transition of the pilot
10 distribution is made, and at least one state for which the turbomachine 18 is outside a
reduction transition of the pilot distribution.
Regarding the minimum pressure determining module 320, this
determination can be performed depending on the state of the turbomachine and
empirically, the values of the pressure quantity having then being experimentally
15 determined during prior factory experiments. As an alternative, this determination can be
made:
- from factory simulations for defining laws regarding the values of
minimum pressure quantity during a reduction transition of the pilot distribution,
- from values considered as being secure values, the latter being
20 overestimated so as to ensure a control of cylinders irrespective of stresses applied to
cylinders.
The calculation module 330 is configured to calculate the current value
of the pressure quantity of the supply circuit 100, for example, based on a model for
continuously determining the pressure level from the fuel flow rate and from a value of
25 supply distribution between the pilot injection line 141 and the main injection line 142.
With such a configuration, the control unit 30 is configured to control the
supply distribution system 130 so as to provide a transition of the supply distribution
between the pilot injection line 141 and the main injection line 142 from a first distribution
value to a second distribution value over a corresponding period of time, the supply
15
distribution having the second distribution value at the end of the corresponding period of
time.
Moreover, the control unit 30 is configured, during a reduction
transition of the pilot distribution, to implement the following steps of:
a) determining at least one minimum value to be 5 maintained of the
pressure quantity of the supply circuit 100 for at least one part of the corresponding period
of time tt,
b) determining at least one hydraulic quantity of the supply circuit 100,
said hydraulic quantity being, for example, the fuel flow rate in the supply circuit 100,
10 c) from at least one hydraulic quantity of the supply circuit 100,
determining a calculated distribution value of supply corresponding to the minimum value
to be maintained of the pressure quantity, the calculated distribution value being chosen
from a range of values defined between the first distribution value and the second
distribution value, said range of values including the first and second distribution values,
15 d) switching the fuel supply distribution to the calculated supply
distribution value.
The control unit 30 is further configured to successively repeat steps b)
to d) for the whole duration of the corresponding period of time.
In other words and according to the invention, with such a configuration
20 of the supply circuit 100, the control unit 30 is for implementing a method for supplying
fuel to a turbomachine including, during a reduction transition of the pilot distribution, the
following steps of:
a) determining at least one minimum value to be maintained of a
pressure quantity of the supply circuit for at least one part of the period of time,
25 b) determining at least one hydraulic quantity of the supply circuit,
c) calculating, from the determined hydraulic quantity of the supply
circuit 100, a calculated distribution value of fuel supply corresponding to the minimum
value to be maintained of the pressure quantity, the calculated distribution value being
chosen from a range of values defined between the first distribution value and the second
30 distribution value, said range of values including the first and second distribution values,
16
d) switching the fuel supply distribution to the calculated distribution
value,
steps b) to d) being successively repeated for the whole duration of the
corresponding period of time.
It will be noted that, alternatively, during step c) of calculating, 5 from the
determined hydraulic quantity of the supply circuit 100, a calculated distribution value of
fuel supply corresponding to the minimum value to be maintained, the calculated
distribution value can be intermediate between the first distribution value and the second
distribution value.
10 It will also be noted that the minimum value to be maintained of a
pressure quantity of the supply circuit can be a minimum pressure value necessary to
actuate at least one part of the hydraulic actuators of the turbomachine, that is
cylinders 40.
According to this first embodiment, step c) of determining a calculated
15 distribution value of fuel supply includes the following sub-steps of:
- calculating an actual value of the pressure quantity of the supply
circuit from the determined hydraulic quantity of the supply circuit and from an actual
distribution value of fuel supply,
- comparing the calculated current value of the pressure quantity of
20 the supply circuit with the determined minimum value to be maintained of the pressure
quantity of the supply circuit,
- calculating, from the comparison result, the calculated distribution
value of fuel supply corresponding to the minimum value to be maintained.
According to one possibility of the invention, it is also contemplatable
25 that, when successively repeating steps b) to d), step a) is also repeated. According to this
possibility, step a) is for determining a minimum value to be maintained of a pressure
quantity of the fuel supply circuit during a given fraction of period of the period of time.
Fig. 4 illustrates a block diagram of a control unit 30 for a fuel supply
circuit 100 according to a second embodiment of the invention. A fuel supply circuit 100
30 according to this second embodiment differs from a fuel supply circuit 100 according to the
17
first embodiment in that the control unit has, instead of the calculation module 330 and
the comparison module, a direct calculation module 335.
The direct calculation module 335 is configured to calculate a calculated
distribution value of fuel supply from the at least one determined hydraulic quantity of the
supply circuit and from the determined minimum value to be maintained 5 of a pressure
quantity of the supply circuit.
According to this second embodiment, the selecting system 350 is
configured to, from the at least one state value 411 of the turbomachine characteristic of
a reduction transition of distribution, select a control value of the supply distribution from
10 that provided by the stabilised phase regulation module 310 and the value calculated by
the direct calculation module 335.
Calculating the calculated distribution value of fuel supply distribution
can be performed based on an equation directly or indirectly derived from equation (1).
Thus, according to this second embodiment, the method for controlling
15 fuel supply differs from a method for controlling fuel supply according to the first
embodiment in that step c) of determining a calculated distribution value of fuel supply
consists of: a step of calculating said calculated distribution value of fuel supply from the
at least one determined hydraulic quantity of the fuel supply circuit and from the
determined minimum value to be maintained of a pressure quantity of the supply circuit.
20 Whether the fuel supply circuit 100 is according to the first embodiment
or the second embodiment, such a supply circuit 100 is for providing, during a reduction
transition of the pilot distribution and as illustrated in Figs. 6A and 6B, a pressure in the fuel
supply circuit compatible with pressure requirements for moving the cylinders 40.
Indeed, Figs. 6A and 6B illustrate such a comparison with, in Fig. 6A, the
25 variation over time in the distribution of fuel supply 531, 532 and, in Fig. 6B, in the
pressure 541, 542 of the supply circuit 100. Fig. 6B also shows, in dotted lines, the result of
determining the minimum necessary pressure value 543 of the supply circuit 100 during
the reduction transition of the pilot distribution.
It will be noted that such a necessary minimum value 543 can be different
30 from the minimum value to be maintained according to the invention since, according to
18
the invention, the minimum value to be maintained can correspond to the minimum
necessary value to which a stored pressure is added.
It can be seen in Fig. 6B, that with such a method of prior art in which
the transition of fuel supply between the pilot injection line 141 and the main injection
line 142 is abrupt, as that illustrated in Fig. 6A, this transition results 5 in a sharp drop in
pressure in the supply circuit 100 and this becomes lower than the minimum pressure value
necessary. Movements of cylinders 40 are therefore partially included therein. After this
sharp drop in pressure, the increase in the fuel flow rate in the supply circuit 100 leads to
a pressure increase and, after a relatively significant period of time, enables the minimum
10 value necessary to be reached. Movements of cylinders 40s. However, it can be seen that
with the method of prior art, pressure in the supply circuit 100 remains lower than the
minimum necessary pressure value during a relatively significant period of time.
Within the scope of the invention, due to be implementation of the
method according to the invention, it can be seen that the drop in the supply distribution
15 has a drop in the supply of the pilot line which is gradual, which is for maintaining the
pressure value to the minimum pressure value to be maintained. This gradual drop is
directly related to the increase in the fuel flow rate in the supply circuit 100. Thus, once the
fuel flow rate is stabilised, the supply distribution 532 is also stabilised by implementing
the method. It will be noted that, according to the principle of the invention, at the end of
20 the period of time tt, the supply distribution 532 is brought back to the second value.
It will be noted that if such a method is particularly advantageous in the
case of a reduction transition of the pilot distribution related to an acceleration in the
turbomachine 10, that is during switching from low speed to high speed, it is also
advantageous during other operating phases of the turbomachine. In particular, the
25 following cases will be mentioned:
- ingestion of external elements, such as a bird, run water/snow and
hail, the turbomachine supply switching during such an ingestion to a so-called “rich”
mixture speed,
- during a rotating stall.
19
Thus, the supply circuit according to the invention and the related
method is for providing, irrespective of the phase of the turbomachine 10 requiring a
reduction transition of the pilot distribution, the pressure necessary to cylinders 40 in order
to ensure the responsivity necessary in controlling the movement of these cylinders 40.
5
20
WE CLAIM:
1. A method for controlling fuel injection into a combustion
chamber (18) of a turbomachine (10), the turbomachine (10) comprising a fuel supply
circuit (100) for an injection system of the combustion chamber 5 (18), said supply
circuit (100) comprising a pilot injection line (141) and a main injection line (142) between
which fuel supply of the combustion chamber (18) is distributed,
controlling method in which, a transition of the supply distribution
between the pilot injection line (141) and the main injection line (142) from a first
10 distribution value to a second distribution value is made over a corresponding period of
time (tt), the supply distribution having the second distribution value at the end of the
corresponding period of time (tt),
the controlling method comprising, for a transition of the supply
distribution from a first distribution value to a second distribution value for which fuel
15 distribution from the pilot injection line (141) is reduced relative to that of this same pilot
injection line (141) for the first distribution value, the following steps of:
a) determining at least one minimum value to be maintained of a
pressure quantity of the supply circuit (100) for at least one part of the period of time,
b) determining at least one hydraulic quantity of the supply
20 circuit (100),
c) calculating, from the determined hydraulic quantity of the supply
circuit (100), a calculated distribution value of fuel supply corresponding to the minimum
value to be maintained of the pressure quantity, the calculated distribution value being
chosen from a range of values defined between the first distribution value and the second
25 distribution value, said range of values including the first and second distribution values,
d) switching the fuel supply distribution to the calculated distribution
value,
at least steps b) to d) being successively repeated for the whole duration
of the corresponding period of time (tt).
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2. The method for controlling fuel injection according to claim 1,
wherein, during step c) of calculating, from the determined hydraulic quantity of the supply
circuit (100), a calculated distribution value of fuel supply corresponding to the minimum
value to be maintained of the pressure quantity, the calculated distribution value is
intermediate between the first distribution value and the second distribution 5 value.
3. The method for controlling fuel injection according to claim 1 or 2,
wherein step c) of calculating the calculated distribution value of fuel supply includes the
following sub-steps of:
10 - calculating from the determined hydraulic quantity of the supply
circuit (100) and from a current distribution value of fuel supplya current value of pressure
quantity of the supply circuit (100),
- comparing the calculated current value of the pressure quantity of
the supply circuit with the determined minimum value to be maintained of the pressure
15 quantity of the supply circuit,
- calculating, from the comparison result, the calculated distribution
value of fuel supply corresponding to the minimum value to be maintained.
4. The method for controlling injection according to claim 1 or 2,
20 wherein step c) of calculating the calculated distribution value of fuel supply consists of a
step of calculating said calculated distribution value of fuel supply from the at least one
determined hydraulic quantity of the fuel supply circuit and from the determined minimum
value to be maintained of the pressure quantity of the supply circuit.
25 5. The method for controlling fuel injection according to any of claims 1
to 4, wherein the pressure quantity is chosen from a pressure value of the supply circuit
and a value of force developed by a cylinder supplied by the supply circuit, and the
hydraulic quantity of the supply circuit is a value of the fuel supply flow rate of the injection
chamber (18).
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6. The method for controlling fuel injection according to any of claims 1
to 5, wherein upon successively repeating steps b) to d), step a) is also repeated, this being
for determining a minimum value to be maintained of the pressure quantity of the fuel
supply circuit for a fraction of period of the corresponding period of time (tt).
5
7. A circuit (100) for supplying a turbomachine with fuel, the fuel circuit
including:
- a pilot injection line (141) for supplying a pilot part of an injection
system of a combustion chamber of the turbomachine,
10 - a main injection line (142) for supplying a main part of the injection
system of the combustion chamber,
- a fuel supply distributing device (130) configured to control fuel
distribution between the pilot injection line (141) and the main injection line (142),
- a control unit (30) able to control the supply distributing device (130)
15 and to make a measurement of some hydraulic quantities of the supply circuit (100),
the control unit (30) being configured to control the distributing
system (130) so as to provide transition of the supply distribution between the pilot
injection line (141) and the main injection line (142) from a first distribution value to a
second distribution value over a corresponding period of time (tt), the supply distribution
20 having the second distribution value at the end of the corresponding period of time,
the fuel supply circuit (100) being characterised in that the control
unit (30) is further configured to, upon controlling by the fuel distributing system (130) to
perform transition of supply distribution from a first distribution value to a second
distribution value for which the fuel distribution of the pilot injection line (141) is reduced
25 relative to that of this same pilot injection line (141) for the first distribution value,
implement the following steps of:
a) determining at least one minimum value to be maintained of a
pressure quantity of the supply circuit (100) for at least one part of the corresponding
period of time (tt),
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b) determining at least one hydraulic quantity of the supply
circuit (100),
c) calculating, from the determined hydraulic quantity of the supply
circuit (100), a calculated distribution value of fuel supply corresponding to the minimum
value to be maintained of the pressure quantity, the calculated distribution 5 value being
chosen from a range of values defined between the first distribution value and the second
distribution value, said range of values including the first and second distribution values,
d) switching the supply distribution to the calculated supply distribution
value,
10 the control unit (30) being further configured to successively repeat
steps b) to d) for the whole duration of the corresponding period of time (tt).
8. The supply circuit (100) according to claim 7, wherein the control
unit (30) is further configured so that, during step c) of calculating, from the determined
15 hydraulic quantity of the supply circuit (100), a calculated distribution value of fuel supply
corresponding to the minimum value to be maintained of the pressure quantity, the
calculated distribution value is intermediate between the first distribution value and the
second distribution value.
20 9. The supply circuit (100) according to claim 7 or 8, wherein the control
unit (30) includes:
- a minimum pressure determining module (320) configured to
determine a minimum value to be maintained of the pressure quantity of the supply
circuit (100) for at least one part of the corresponding period of time (tt),
25 - a calculation module (330) configured to calculate from a
determined hydraulic quantity of the supply circuit (100) and from a current value of the
fuel supply distribution, a current value of the pressure quantity of the supply circuit (100),
- a comparison module (340) configured to compare the calculated
current value of the pressure quantity of the supply circuit (100) with the determined
30 minimum value to be maintained of the pressure quantity of the supply circuit (100), and
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to calculate, from the comparison result, a calculated distribution value of fuel supply
corresponding to the determined minimum value to be maintained of the pressure
quantity of the supply circuit (100).
10. The supply circuit (100) according to claim 7 5 or 8, wherein the
control unit (30) includes
- a minimum pressure determining module (320) configured to
determine a minimum value to be maintained of the pressure quantity of the supply
circuit (100) for at least one part of the corresponding period of time (tt),
10 - a direct calculation module (335) configured to calculate a calculated
distribution value of fuel supply from the at least one determined hydraulic quantity of the
supply circuit (100) and from the determined minimum value to be maintained of the
pressure quantity of the supply circuit (100).
15 11. The supply circuit (100) according to any of claims 7 to 10,
wherein the control unit (30) is a turbomachine calculator.
12. A turbomachine (10) comprising an injection chamber (18),
said injection chamber (18) comprising an injection system, said turbomachine (10) being
20 characterised in that it further comprises a fuel supply circuit (100) according to any of
claims 7 to 11 supplying the injection system with fuel.