U.S. patent application number 15/907953 was filed with the patent office on 2018-09-06 for mixer.
This patent application is currently assigned to ANSALDO ENERGIA SWITZERLAND AG. The applicant listed for this patent is ANSALDO ENERGIA SWITZERLAND AG. Invention is credited to Mirko Ruben BOTHIEN, Alessandro SCARPATO.
Application Number | 20180252412 15/907953 |
Document ID | / |
Family ID | 58227960 |
Filed Date | 2018-09-06 |
United States Patent
Application |
20180252412 |
Kind Code |
A1 |
BOTHIEN; Mirko Ruben ; et
al. |
September 6, 2018 |
MIXER
Abstract
A mixer having a housing, a duct within the housing, a first and
a second injector arranged to inject a fluid at a centre zone of
the duct, a third and a fourth injector arranged to inject the
fluid at a wall zone of the duct. The first/third injectors are at
a distance D1=v/2f.sub.1 or odd integer multiples of it from the
second/fourth injectors in the absence of an acoustic node between
them, or at a distance D1=.lamda..sub.conv=v/f.sub.1 or full wave
length integer multiples of it in the presence of an acoustic node
between them. Advantageously f.sub.1 is greater than f.sub.2.
Inventors: |
BOTHIEN; Mirko Ruben;
(Zurich, CH) ; SCARPATO; Alessandro; (Wettingen,
CH) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
ANSALDO ENERGIA SWITZERLAND AG |
Baden |
|
CH |
|
|
Assignee: |
ANSALDO ENERGIA SWITZERLAND
AG
Baden
CH
|
Family ID: |
58227960 |
Appl. No.: |
15/907953 |
Filed: |
February 28, 2018 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F23R 3/346 20130101;
F23R 2900/03341 20130101; F23R 3/283 20130101; F23R 3/00 20130101;
F23R 2900/00014 20130101 |
International
Class: |
F23R 3/34 20060101
F23R003/34; F23R 3/28 20060101 F23R003/28 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 2, 2017 |
EP |
17159008.6 |
Claims
1. A mixer comprising: a housing; a duct within the housing; a
first injector and a second injector arranged to inject a fluid at
a centre zone of the duct; a third injector and a fourth injector
arranged to inject the fluid at a wall zone of the duct, wherein:
the first injector is at a distance D1=v/2f.sub.1 or odd integer
multiples of it from the second injector in an absence of an
acoustic node between the second injector and the first injector,
or at a distance D1=.lamda..sub.conv=v/f.sub.1 or full wave length
integer multiples of it in a presence of an acoustic node between
the second injector and the first injector; and the third injector
is at a distance D2=v/2f.sub.2 or odd integer multiples of it from
the fourth injector in an absence of an acoustic node between the
third injector and the first injector, or at a distance
D2=v/f.sub.2 from the first injector in a presence of an acoustic
node between the third injector and the first injector; wherein:
f.sub.1 is an oscillating frequency to be damped at the wall zone
of the duct; f.sub.2 is an oscillating frequency to be damped at
the centre zone of the duct; and v is a fluid flow speed through
the duct, wherein f.sub.1 is greater than f.sub.2.
2. The mixer of claim 1, wherein both f1 and f2 are lower than 150
Hz.
3. The mixer of claim 1, wherein the first injector and/or the
second injector and/or the third injector and/or the fourth
injector comprise: a plurality of rows of nozzles close to one
another.
4. The mixer of claim 2, wherein nozzles of different rows of
nozzles of a same injector have different penetration.
5. The mixer of claim 2, wherein the nozzles of a same row of
nozzles have different penetration.
6. A gas turbine comprising: a compressor; a first combustion
chamber; a second combustion chamber arranged to be fed with a
fluid coming from the first combustion chamber; and a turbine,
wherein between the first combustion chamber and the second
combustion chamber a mixer is provided, which mixer includes: a
housing; a duct within the housing; a first injector and a second
injector arranged to inject a fluid at a centre zone of the duct; a
third injector and a fourth injector arranged to inject the fluid
at a wall zone of the duct, wherein: the first injector is at a
distance D1=v/2f.sub.1 or odd integer multiples of it from the
second injector in an absence of an acoustic node between the
second injector and the first injector, or at a distance
D1=.lamda..sub.conv=v/f.sub.1 or full wave length integer multiples
of it in a presence of an acoustic node between the second injector
and the first injector; and the third injector is at a distance
D2=v/2f.sub.2 or odd integer multiples of it from the fourth
injector in an absence of an acoustic node between the third
injector and the first injector, or at a distance D2=v/f.sub.2 from
the first injector in a presence of an acoustic node between the
third injector and the first injector; wherein: f.sub.1 is an
oscillating frequency to be damped at the wall zone of the duct;
f.sub.2 is an oscillating frequency to be damped at the centre zone
of the duct; and v is a fluid flow speed through the duct, wherein
f.sub.1 is greater than f.sub.2.
Description
PRIORITY CLAIM
[0001] This application claims priority from European Patent
Application No. 17159008.6 filed on Mar. 2, 2017, the disclosure of
which is incorporated by reference.
TECHNICAL FIELD
[0002] The present invention relates to a mixer. In particular the
mixer is part of a gas turbine and is used to supply dilution air
into the hot gas passing through the gas turbine.
BACKGROUND
[0003] FIG. 1 schematically shows an example of a gas turbine; the
gas turbine 1 has a compressor 2, a first combustion chamber 3, a
second combustion chamber 4 and a turbine 5. Possibly between the
first combustion chamber 3 and the second combustion chamber 4 a
high pressure turbine is provided. During operation air is
compressed at the compressor 2 and is used to combust a fuel in the
first combustion chamber 3; the hot gas (possibly partly expanded
in the high pressure turbine) is then sent into the second
combustion chamber 4 where further fuel is injected and combusted;
the hot gas generated at the second combustion chamber 4 is then
expanded in the turbine 5.
[0004] Between the first combustion chamber 3 and the second
combustion chamber 4 a mixer 7 can be provided in order to dilute
with air (or other gas) the hot gas coming from the first
combustion chamber 3 and directed into the second combustion
chamber 4.
[0005] FIG. 2 schematically shows the section of the gas turbine
including the first and the second combustion chambers 3, 4. FIG. 2
shows a first burner 3a of the first combustion chamber 3 where the
compressed air coming from the compressor 2 is mixed with the fuel
and a combustor 3b where the mixture is combusted generating hot
gas (reference 20a indicates the flame). The hot gas is directed
via a transition piece 3c into the mixer 7, where air is supplied
into the hot gas to dilute it. The diluted (and cooled) hot gas is
thus supplied into the burner 4a of the second combustion chamber 4
where further fuel is injected into the hot gas via a lance 8 and
mixed to it. This mixture combusts in the combustor 4b by auto
combustion (reference 20b indicates the flame), after a "delay
time" from the injection into the second burner 4a.
[0006] The temperature in the second burner 4a can oscillate,
typically because of mass flow oscillations of the air coming from
the mixer 7 and directed into the second burner 4a.
[0007] The delay time depends on, inter alia, the temperature
within the second burner 4a, such that temperature oscillations in
the second burner 4a cause increase/decrease of the delay time and
thus axial upwards/downwards oscillations of the flame in the
combustor 4b.
[0008] In order to prevent these axial oscillations of the flame,
the temperature in the second burner 4a has to be maintained
constant and thus the flow emerging from the mixer 7 has to be
maintained constant.
[0009] The mass flow through the mixer 7 can vary because within
the mixer 7 pressure oscillations exist (e.g. due to the combustion
in the combustor 3b and/or 4b); these pressure oscillations cause
an increase/decrease of the flow of diluting air injected into the
mixer.
[0010] In order to maintain this flow constant, multiple injectors
can be provided at different axial locations of the mixer 7, in
such a way that oscillating pressure air supplied through upstream
injectors compensate for oscillating pressure air supplied trough
downstream injectors. In other words, air is injected in such a way
that high pressure air injected from upstream injectors reaches the
downstream injectors when low pressure air is injected through them
(and vice versa); this way the high pressure and low pressure
compensate for one another and are cancelled, such that the
pressure within the mixer 7 stays substantially constant; air
injection into the mixer can thus be constant over time.
[0011] The inventors have found a way to improve cancellation of
pressure oscillations (and thus mass flow oscillations) through the
cross section of the mixer.
SUMMARY
[0012] An aspect of the invention includes providing a mixer with
improved flow oscillation cancellation.
[0013] These and further aspects are attained by providing a mixer
in accordance with the accompanying claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] Further characteristics and advantages will be more apparent
from the description of a preferred but non-exclusive embodiment of
the mixer, illustrated by way of non-limiting example in the
accompanying drawings, in which:
[0015] FIG. 1 schematically shows a gas turbine;
[0016] FIG. 2 schematically shows the first combustion chamber,
mixer and second combustion chamber of the gas turbine of FIG.
1;
[0017] FIG. 3 shows a longitudinal section of a mixer;
[0018] FIG. 4 shows a different embodiment of the gas turbine;
[0019] FIGS. 5 and 6 show the distance between the first, second,
third, fourth injectors, in relation with the pressure within the
mixer itself; in those figures the reference 0 identifies the
nominal pressure within the mixer;
[0020] FIG. 7 shows an example of injectors comprising more rows of
nozzles, and
[0021] FIG. 8 shows a different embodiment of the mixer.
DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS
[0022] With reference to the figures, these show the gas turbine 1
with the compressor 2, the first combustion chamber 3, the second
combustion chamber 4 fed with a fluid coming from the first
combustion chamber 3, the turbine 5. Between the first combustion
chamber 3 and the second combustion chamber 4 it is provided the
mixer 7. In addition, between the first combustion chamber 3 and
the second combustion chamber 4 (upstream or downstream of the
mixer 7), a high pressure turbine can be provided (FIG. 4, turbine
9).
[0023] The mixer 7 comprises a housing 10, a duct 11 within the
housing 10, a first injector 12 arranged to inject a fluid at the
centre zone of the duct 11, a second injector 13 arranged to inject
a fluid at the centre zone of the duct 11, a third injector 14
arranged to inject a fluid at the wall zone of the duct 11 and a
fourth injector 15 arranged for injecting a fluid at the wall zone
of the duct 11. Additional injectors can also be provided.
[0024] Each injector can comprise a row of nozzles 16 extending
over the circumference or perimeter of the duct 11; in addition
each injector can comprise a plurality of rows of nozzles close to
one another. Additionally, nozzles 16 of different rows of nozzles
of a same injector can have same or different penetration and/or
nozzles 16 of a same row of nozzles can have different
penetration.
[0025] For example, FIG. 3 shows an embodiment with injectors
arranged for injecting the fluid at the centre zone and at the wall
zone of the duct 11 that are provided close to one another.
[0026] In order to inject the fluid at the centre zone 18 of the
duct 11 the first and second nozzles 12, 13 have a deep penetration
into the duct 11; likewise in order to inject the fluid at the wall
zone 17 of the duct 11 the third and fourth nozzles have a small
penetration into the duct 11; generally the first and second
injectors 12, 13 have a deeper penetration into the duct 11 than
the third and fourth injectors 14, 15.
[0027] The relative position of the injectors can be any, i.e. any
injector can be upstream and/or downstream of any other injector
(upstream and downstream are referred to the fluid circulation
direction identified by the arrow F in the figures).
[0028] The distance between the first injector 12 and the second
injector 13 is, in case there is no acoustic node between them
(i.e. in the absence of an acoustic node)
D1=.lamda..sub.conv/2=v/2f.sub.1
[0029] or an odd integer multiple of it. In case there is an
acoustic node between the first and second injectors 12, 13 (i.e.
in the presence of an acoustic node) the distance D1 is
D1=.lamda..sup.conv=v/f.sub.1
[0030] or a full wave length integer multiple of it.
[0031] Likewise, the distance between the third injector 14 and the
fourth injector 15 is, in case there is no acoustic node between
them (i.e. in the absence of an acoustic node)
D2=.lamda..sub.conv/2=v/2f.sub.2
[0032] or an odd integer multiple of it. In case there is an
acoustic node between the third injector 14 and the fourth injector
15 (i.e. in the presence of an acoustic node) the distance D2
is
D2=.lamda..sup.conv=v/f.sub.2
[0033] or a full wave length integer multiple of it.
[0034] In the above formulas:
[0035] f.sub.1 is the oscillating frequency (pressure oscillation)
to be damped at the wall zone 17 of the duct 11, i.e. at zones
within the duct 11 that are close to the wall, e.g. at the outer
part of the flame,
[0036] f.sub.2 is the oscillating frequency (pressure oscillations)
to be damped at a centre zone 18 of the duct 11, e.g. at the inner
or centre part of the flame,
[0037] .lamda..sub.conv is the convective wave length, i.e. the
flow velocity v through the duct divided by the frequency that
should be addressed with the concept,
[0038] v is the fluid flow speed through the duct 11.
[0039] Acoustic node defines the change of sign of the pressure
with reference to the nominal pressure.
[0040] In addition, the distances D1 and D2 are measured between
the axes of the nozzles 16 of the injectors 12, 13, 14, 15 or, in
case an injector comprises more rows of nozzles 16 (all injecting
into the same zone being the centre or the wall zone), with
reference to an average position between the two or more axes of
the nozzles 16 of this injector (see e.g. FIG. 7).
[0041] As an example, FIG. 5 shows one wall of the duct 11 and the
pressure in relation to an axial coordinate thereof. From this
figure it can be acknowledged that the distance of the first
injector 12 from the second injector is
D1=.lamda..sub.conv/2=v/2f.sub.1 and likewise the distance of the
third injector 14 from the fourth injector 15 is
D2=.lamda..sub.conv/2=v/2f.sub.2 because in this example between
the first and second injectors 12, 13 and third and fourth
injectors 14, 15 no acoustic nodes are present.
[0042] FIG. 6 is similar to FIG. 5; from this figure it can be
acknowledged that the distance of the first injector 12 from the
second injector 13 is D1=.lamda..sub.conv/2=v/2f.sub.1 because
there is no acoustic node between them and the distance of the
third injector 14 from the fourth injector 15 is
D2=.sub.conv=v/f.sub.2 because an acoustic node is provided between
them (the acoustic node being identified by reference 22).
[0043] Advantageously, f.sub.1 is greater than f.sub.2. Both
f.sub.1 and f.sub.2 are low frequencies e.g. below 150 Hz.
[0044] The operation of the mixer and gas turbine having such a
mixer is apparent from that described and illustrated and is
substantially the following.
[0045] Air is compressed at the compressor 2 and is supplied into
the burner 3a where fuel is supplied and mixed with the compressed
air, generating a mixture that combusts in the combustor 3b with a
flame 20a; the hot gas generated through this combustion passes
through the transition piece 3c and enters the mixer 4 (in
particular the duct 11 of the mixer 4).
[0046] At the mixer 4 air is injected into the hot gas via the
first, second, third, fourth injectors 12, 13, 14, 15 and via
possible additional injectors.
[0047] This configuration allows a selective cancellation of the
mass flow oscillations, because different zones of the cross
section of the duct 11 are responsible for generating pulsations of
different frequency. In particular, as indicated above, the zones
closer to the duct wall have a higher frequency while the zones
farther from the duct walls (i.e. at the centre of the duct) have a
lower frequency.
[0048] FIG. 8 shows an example of a mixer having a plurality of
injectors (more than four).
[0049] Naturally the features described may be independently
provided from one another. For example, the features of each of the
attached claims can be applied independently of the features of the
other claims.
[0050] In practice the materials used and the dimensions as well as
the injector shapes can be chosen at will according to requirements
and to the state of the art.
REFERENCE NUMBERS
[0051] 1 gas turbine [0052] 2 compressor [0053] 3 first combustion
chamber [0054] 3a first burner [0055] 3b combustor [0056] 3c
transition piece [0057] 4 second combustion chamber [0058] 4a
second burner [0059] 4b combustor [0060] 5 turbine [0061] 7 mixer
[0062] 8 lance [0063] 9 turbine [0064] 10 housing [0065] 11 duct
[0066] 12 first injector [0067] 13 second injector [0068] 14 third
injector [0069] 15 fourth injector [0070] 16 nozzles [0071] 17 wall
zone [0072] 18 centre zone [0073] 20a, 20b flame [0074] 22 acoustic
node [0075] D1 distance [0076] D2 distance [0077] F flow [0078]
.lamda..sub.conv convective wave length [0079] v fluid flow speed
through the duct
* * * * *