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{{Short description|Turbofan engine component}}
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[[File:Boeing 737-2B7-Adv, Dasab Airlines AN0992824.jpg|thumb|Exhaust mixer of a [[Pratt & Whitney JT8D|JT8D]] engine of a [[Boeing 737-200]]]]
{{More citations needed
{{Refimprove
| date = June 2017
| date = June 2017
}}
}}
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[[File:Boeing 737-2B7-Adv, Dasab Airlines AN0992824.jpg|thumb|Exhaust mixer of a [[Pratt & Whitney JT8D|JT8D]] engine of a [[Boeing 737-200]]]]
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In aviation, '''exhaust mixer''' is a feature of many [[turbofan engine]]s, where the bypass (cold/slow) air is mixed with the core (hot/fast) [[exhaust gas]]es, before exhausting to atmospheric pressure through a common (mixed flow) propelling [[nozzle]].

⚫
In aviation, an '''exhaust mixer''' / '''flow mixer''' is a feature of many [[turbofan engine]]s, where slower, colder bypass air is mixed with faster, hotter core [[exhaust gas]]es, before exhausting to atmospheric pressure through a common (mixed flow) propelling [[nozzle]].<ref>{{cite web | url=https://www.dreamlandresort.com/black_projects/patent.htm | title=Patent Descriptions }}</ref>


==Benefits==
==Benefits==
[[File:Convair 880 Lisa Marie Graceland Memphis TN 2013-04-01 028.jpg|thumb|[[Hush kit]] mixer on the turbojet [[General Electric CJ805]] of a [[Convair 880]]]]
[[File:Convair 880 Lisa Marie Graceland Memphis TN 2013-04-01 028.jpg|thumb|[[Hush kit]] mixer on the turbojet [[General Electric CJ805]] of a [[Convair 880]]]]
[[File:Safran_Silvercrest.png|thumb|Exhaust mixer on a mockup of a [[Safran Silvercrest]] high-bypass turbofan used on large business jets]]
The mixer reduces the [[velocity]] of the core exiting air, and consequently, reducing the amount of noise produced. Additionally, the temperature of the exhaust is reduced, rendering the thermal signature of the aircraft to be lower as well. This attribute is critical in military aircraft where thermal detection or [[heat-seeking]] weapons are used.
The mixer reduces the [[velocity]] of the core exiting air, and consequently, reducing the amount of noise produced. Additionally, the temperature of the exhaust is reduced, contributing to the overall reduction of the thermal signature of the aircraft. This attribute is critical in military aircraft where thermal detection or [[heat-seeking]] weapons are used, in particular [[Stealth_technology|stealth]] [[Stealth aircraft|aircraft]].<ref>https://understandingairplanes.com/Stealth-Airplane-Design.pdf {{Bare URL PDF|date=August 2024}}</ref><ref>https://nsarchive2.gwu.edu/NSAEBB/NSAEBB443/docs/area51_14.PDF</ref><ref>https://watermark.silverchair.com/v002t02a002-90-gt-116.pdf?token=AQECAHi208BE49Ooan9kkhW_Ercy7Dm3ZL_9Cf3qfKAc485ysgAABIMwggR_BgkqhkiG9w0BBwagggRwMIIEbAIBADCCBGUGCSqGSIb3DQEHATAeBglghkgBZQMEAS4wEQQMdZ7l5lD183NosVlKAgEQgIIENkQQM1IZtwnfHAGBQ-mMRxLvxQ_aQqABcJ-FuzGclLLYZNBbYub-BjC41MeEO-a0lpzvUJmt30r9YdcLjPPcgnZkuIOXyoE88f6BNYxe6RHh6_MfG1ji95dmRhUiLAB0MuNvvU3QqWMy-rvQcWe7TcEojRqjyVX7eUH6xYJMhNYymisT7OnYA_ow07FHdLfID27LMt3B9MjweDMp-Uqk1NTTj_ZAg00g9cTMM_KuU7GFPxZPgyZv4X1bNZk1w7_3ivJrpq_EnN4k_wWUoFSSoJiUD7oUI1otnpjNsWiTg00cK26HyqrGS5n7LC2vedrtX5DEs26-1-qxC60ORuoI3s58BY_G72CRbEH_xmVej69TsTzVMFLAKOllXxsg19GC-2Zo16xlUfYgGLvbEENILLeASzaQKn6n8NZxWD0M5kmFQKWk2Pv5ur2jfNzykOMtGSMIHoi42Lt5hSZsYHnMeiFd4JAxMFTb_fjeerdnZ8iSKWARBgAnOlvYGqUBvV7WIOqNRAl3Nst-FRJ_6flGC2KNP1El0kMX-n6IWRGtIZithaCqu6pUjPxEqWT0m3AGwEg_Q5VdFUdsoj9VlltKmirDmPj0036QnWIrwyhsRdZKH6Js0owgRuI2_GDk3CMcZCM7noC6e9BCUy9Oz89dqeOBddQtCAaeX7cojJubHeaAPWZSlQPUrZOez2Lz7rQ65EqbHatVbQL42wyJf8fYfH04GaLPWxJ3uATUz7HwXeaNYN47Nq_ifwpX3Y_aHj5YDkTW508W6C807PJO3SzDfUmWZf-ImkVBzVAfYc2HBEb_KLfGRof4UXBUhBpL9UOA6dwdG9ayLU7EYtLW2XPMYWo3AX8E-ezegZZpvygdfyygPRzD7LRI987CGu2vzhu-AeVU7hbBF-y88xhvc20vUli98PEH46ATKCJ7f1q-nZj8Dy-njEKzVz-fHsdSPLKPnl0UB1SBRBZccdkawygmz0GhUXx8iZknRAKklv0xZEgnhULAzJIErLHZTKUCl7rxr1qaBJlcUAO6Z2vmqMYsbh2JEftUNMNT_ZanwfSmf8eTA3waZtEqP83XrDedkuYe2XwsO7NDO69FnoX5e9KWa5iV26doAsj_i_PRcypKM0A48EXuCtpPdWAUlGTzZjQ09CABpAh9S_gCEuaGjtOCFI-7l43GbtMabtXmGNYAPoJZ6qFlR3uz3d-I9zBOkAfIb9d_1TAgRIqIIlOy0vS6xBRQBdjAXmTSFPo76WubcgHnhV1WjzlwZ-5Ydy_ztSmHvwrEO5ff3KLD7PPHbHcUlqwZqjFtTsv2PKEqaZrnRU_Kg7hcolnGo_XqpMja4OEQOePjvvYD7HTe4JV71JzRtFOkwcxEzg-kKDtM7sAAQLk4sjUI1xs8XILKzdg27LAoAuGr-fdG8qyXYQXHx5TVQ21IrS3rhmA</ref>


Ideally, a mixer is also a performance benefit to increasing thrust. The exhaust thrust from a jet engine is equal to exhaust mass flow times exhaust velocity, i.e., ''Thrust = ṁv'', while the energy to make that thrust is given by ''Energy'' = 1/2''mv''<sup>2</sup>. A mixer helps reduce the fastest exhaust velocities from the core of the engine, while making the average exhaust velocity faster, producing more thrust with the same energy.
Ideally, a mixer is also a performance benefit to increasing thrust. The exhaust thrust from a jet engine is equal to exhaust mass flow times exhaust velocity, i.e., ''Thrust = ṁv'', while the energy to make that thrust is given by ''Energy'' = 1/2''mv''<sup>2</sup>. A mixer helps reduce the fastest exhaust velocities from the core of the engine, while making the average exhaust velocity faster, producing more thrust with the same energy.


<gallery mode="packed" heights="160px">
<gallery mode="packed" heights="160px">
File:Trent 700 - DSC 8123-F-WWCR - MSN 1462 (10513329855) (cropped).jpg|On the [[Airbus A330]], the [[Trent 700]] has an exhaust mixer
File:Trent 700 - DSC 8123-F-WWCR - MSN 1462 (10513329855) (cropped).jpg|The [[Trent 700]] which powers the [[Airbus A330]], has a common nozzle assembly which mixes the cold and hot flows.<ref>Lufthans Technical Training, Training Manual Airbus A330, ATA71-80 Engine RR Trent 700, page 30</ref>
File:Airbus A330-200F(F-WWYE) (4337113707).jpg|While the [[PW4000]] has separate exhausts
File:Airbus A330-200F(F-WWYE) (4337113707).jpg|The [[PW4000]] has separate exhaust nozzles
File:Northrop Tacit Blue rear R&D NMUSAF 25Sep09 (14600452315).jpg|Slit shaped tail exhaust [[Northrop Tacit Blue]]
</gallery>
</gallery>


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== See also ==
== See also ==
* [[Index of aviation articles]]
* [[Infrared countermeasure]]
* [[Chevron (aeronautics)]]
* [[Chevron (aeronautics)]]
* [[Hush kit]]
* [[QTOL]]


==References==
==References==
{{Reflist}}
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*http://www.fluent.com/solutions/examples/x178.htm

==External links==
⚫
*[http://www.fluent.com/solutions/examples/x178.htm]


[[Category:Gas turbines]]
[[Category:Gas turbines]]
[[Category:Missile countermeasures]]
[[Category:Stealth technology]]

Latest revision as of 23:45, 21 December 2024

Exhaust mixer of a JT8D engine of a Boeing 737-200

In aviation, an exhaust mixer / flow mixer is a feature of many turbofan engines, where slower, colder bypass air is mixed with faster, hotter core exhaust gases, before exhausting to atmospheric pressure through a common (mixed flow) propelling nozzle.[1]

Benefits

[edit]
Hush kit mixer on the turbojet General Electric CJ805 of a Convair 880
Exhaust mixer on a mockup of a Safran Silvercrest high-bypass turbofan used on large business jets

The mixer reduces the velocity of the core exiting air, and consequently, reducing the amount of noise produced. Additionally, the temperature of the exhaust is reduced, contributing to the overall reduction of the thermal signature of the aircraft. This attribute is critical in military aircraft where thermal detection or heat-seeking weapons are used, in particular stealth aircraft.[2][3][4]

Ideally, a mixer is also a performance benefit to increasing thrust. The exhaust thrust from a jet engine is equal to exhaust mass flow times exhaust velocity, i.e., Thrust = ṁv, while the energy to make that thrust is given by Energy = 1/2mv2. A mixer helps reduce the fastest exhaust velocities from the core of the engine, while making the average exhaust velocity faster, producing more thrust with the same energy.

Mixer types

[edit]
Apache AH-64 helicopter, with exhaust mixer to reduce IR signal
  • Annular - bypass and core streams are brought together co-annularly, mixing being achieved by the shearing effect at the stream interface
  • Forced - hot and cold chutes, intertwined, force the two streams to mix

Mixing efficiency is defined in a number of ways, but simply, compares the actual thrust gain (due to mixing) to that of the ideal case. Annular mixers have a low pressure loss, but a low mixing efficiency. Forced mixers can have a high mixing efficiency, but this is offset by a high pressure loss.

Mixers are extremely common on military turbofans, since long coaxial exhaust pipes (i.e. hot and cold) are avoided. Afterburning, with the associated variable area nozzle, is also easier to accommodate.

Some high bypass ratio (e.g. civil) turbofans now feature a mixer, the advantage being a small thrust gain, which improves specific fuel consumption. Although the mixing process is not thorough, there is a jet noise benefit as well.

See also

[edit]

References

[edit]
  1. ^ "Patent Descriptions".
  2. ^ https://understandingairplanes.com/Stealth-Airplane-Design.pdf [bare URL PDF]
  3. ^ https://nsarchive2.gwu.edu/NSAEBB/NSAEBB443/docs/area51_14.PDF
  4. ^ https://watermark.silverchair.com/v002t02a002-90-gt-116.pdf?token=AQECAHi208BE49Ooan9kkhW_Ercy7Dm3ZL_9Cf3qfKAc485ysgAABIMwggR_BgkqhkiG9w0BBwagggRwMIIEbAIBADCCBGUGCSqGSIb3DQEHATAeBglghkgBZQMEAS4wEQQMdZ7l5lD183NosVlKAgEQgIIENkQQM1IZtwnfHAGBQ-mMRxLvxQ_aQqABcJ-FuzGclLLYZNBbYub-BjC41MeEO-a0lpzvUJmt30r9YdcLjPPcgnZkuIOXyoE88f6BNYxe6RHh6_MfG1ji95dmRhUiLAB0MuNvvU3QqWMy-rvQcWe7TcEojRqjyVX7eUH6xYJMhNYymisT7OnYA_ow07FHdLfID27LMt3B9MjweDMp-Uqk1NTTj_ZAg00g9cTMM_KuU7GFPxZPgyZv4X1bNZk1w7_3ivJrpq_EnN4k_wWUoFSSoJiUD7oUI1otnpjNsWiTg00cK26HyqrGS5n7LC2vedrtX5DEs26-1-qxC60ORuoI3s58BY_G72CRbEH_xmVej69TsTzVMFLAKOllXxsg19GC-2Zo16xlUfYgGLvbEENILLeASzaQKn6n8NZxWD0M5kmFQKWk2Pv5ur2jfNzykOMtGSMIHoi42Lt5hSZsYHnMeiFd4JAxMFTb_fjeerdnZ8iSKWARBgAnOlvYGqUBvV7WIOqNRAl3Nst-FRJ_6flGC2KNP1El0kMX-n6IWRGtIZithaCqu6pUjPxEqWT0m3AGwEg_Q5VdFUdsoj9VlltKmirDmPj0036QnWIrwyhsRdZKH6Js0owgRuI2_GDk3CMcZCM7noC6e9BCUy9Oz89dqeOBddQtCAaeX7cojJubHeaAPWZSlQPUrZOez2Lz7rQ65EqbHatVbQL42wyJf8fYfH04GaLPWxJ3uATUz7HwXeaNYN47Nq_ifwpX3Y_aHj5YDkTW508W6C807PJO3SzDfUmWZf-ImkVBzVAfYc2HBEb_KLfGRof4UXBUhBpL9UOA6dwdG9ayLU7EYtLW2XPMYWo3AX8E-ezegZZpvygdfyygPRzD7LRI987CGu2vzhu-AeVU7hbBF-y88xhvc20vUli98PEH46ATKCJ7f1q-nZj8Dy-njEKzVz-fHsdSPLKPnl0UB1SBRBZccdkawygmz0GhUXx8iZknRAKklv0xZEgnhULAzJIErLHZTKUCl7rxr1qaBJlcUAO6Z2vmqMYsbh2JEftUNMNT_ZanwfSmf8eTA3waZtEqP83XrDedkuYe2XwsO7NDO69FnoX5e9KWa5iV26doAsj_i_PRcypKM0A48EXuCtpPdWAUlGTzZjQ09CABpAh9S_gCEuaGjtOCFI-7l43GbtMabtXmGNYAPoJZ6qFlR3uz3d-I9zBOkAfIb9d_1TAgRIqIIlOy0vS6xBRQBdjAXmTSFPo76WubcgHnhV1WjzlwZ-5Ydy_ztSmHvwrEO5ff3KLD7PPHbHcUlqwZqjFtTsv2PKEqaZrnRU_Kg7hcolnGo_XqpMja4OEQOePjvvYD7HTe4JV71JzRtFOkwcxEzg-kKDtM7sAAQLk4sjUI1xs8XILKzdg27LAoAuGr-fdG8qyXYQXHx5TVQ21IrS3rhmA
  5. ^ Lufthans Technical Training, Training Manual Airbus A330, ATA71-80 Engine RR Trent 700, page 30
[edit]
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