JPH0344220B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention This invention relates to an exhaust system for a mixed flow gas turbine engine, and more particularly, to an improved exhaust system for internally mixing fan bypass air and core engine exhaust gas. This invention relates to an assembly consisting of an exhaust center body and a mixer.

BACKGROUND OF THE INVENTION Gas turbine engine technology involves efficient mixing of fan bypass air with core engine exhaust gas and discharging the combined flow through a single exhaust nozzle to produce a bypass turbofan engine. It is known that it is possible to improve the performance of One exhaust system for mixing fan bypass air and exhaust gases includes a lobed mixer located downstream of the core engine. The lobe mixer forces the relatively hot exhaust gases to mix with the relatively cool fan bypass air to provide improved thermodynamic properties and thus improve fuel consumption.

A gas turbine engine operates when the combined fan and core engine exhaust streams have a relatively uniform temperature at the exit plane of the exhaust nozzle that is substantially lower than the unmixed peak temperature. Thermodynamic properties are improved. Various exhaust system geometric parameters have been studied to enhance the mixing effect to obtain a more uniform temperature distribution. Certain parameters that are evaluated for this purpose include, for example, the number of lobes in the mixer, the height of the mixer, the length of the mixer, the cross section of the mixer, the shape of the end face of the mixer and the notch in the mixer. Other geometrical parameters evaluated include the diameter, shape, and mixing length of the exhaust system transition piece.

However, by suitably varying these geometrical parameters, the mixing effect can be enhanced, but the parasitic pressure losses typically associated with the exhaust system are also increased. For example, in high bypass ratio turbofan engines, the exhaust dynamic pressure typically accounts for a large proportion of the total exhaust pressure, and the engine therefore experiences relatively large parasitic pressure losses. Therefore, conventional exhaust systems are typically compromise systems that
Mixing effectiveness is limited by parasitic pressure losses.

Accordingly, one object of the present invention is to provide an improved exhaust system for a mixed flow gas turbine engine.

Another object of the invention is to enhance the internal mixing of core engine exhaust gases and fan bypass air;
An object of the present invention is to provide an improved exhaust system that provides a more uniform temperature distribution across the exit plane of an exhaust nozzle.

Another object of the invention is to provide an improved evacuation system that increases the mixing effect without appreciably increasing the pressure losses attributable thereto.

SUMMARY OF THE INVENTION One form of the invention provides an improved exhaust system that includes a lobe mixer and an improved exhaust centerbody. This exhaust center body is
In cooperation with the lobe mixer, means are included for increasing the mixing effectiveness of the exhaust system without substantially increasing the pressure losses attributable thereto. In a preferred embodiment of the invention, the means include a plurality of circumferentially spaced elongated deformations, such as grooves or ridges, which extend radially relative to a reference plane of the exhaust center body. It extends and is axially aligned substantially parallel to the longitudinal axis of the center body.

Other objects and advantages of the invention will become apparent from the following detailed description of the drawings.

DETAILED DESCRIPTION FIG. 1 shows an exemplary high bypass ratio mixed flow gas turbofan engine 10 that includes an exhaust system 12 in accordance with one type of the present invention. A turbofan engine 10 has a fan 14 that is driven by a core engine 16 disposed coaxially about a longitudinal axis 18 of the engine downstream of the fan 14 . core engine 16
includes a compressor, a combustor, and a turbine (none of which are shown), which produces relatively high temperature combustion exhaust gas 2.
It acts to discharge 0.

The core engine 16 is arranged circumferentially around the core engine 16.
A cowl 22 is arranged. An aerodynamically streamlined exhaust centerbody 24 in accordance with one form of the invention to be described hereinafter is suitably mounted to the core engine 16 and extends downstream from the annular rear end 26 of the core cowl 22. It's growing. The exhaust center body 24 is located on the inner surface 28 of the core cowl 22.
radially inwardly spaced from the core engine 1
core nozzle 3 discharging exhaust gas 20 from 6;
Configure 0.

A nacelle 32 is disposed circumferentially around the fan 14 and core engine 16 and is spaced radially outwardly from the core cowl 22 to provide a relatively cool fan sideway downstream of the fan 14. An annular side duct 34 is configured as a passage for air 36. Nacelle 32 cooperates with aft end 26 of core cowl 22 to define an annular fan nozzle 38 for discharging fan bypass air 36 (simply referred to as fan air 36) from bypass duct 34. A nacelle 32 extends downstream from the aft end 26 of the core cowl 22 and receives fan air 3 from a fan nozzle 38.
One exhaust nozzle 40 is configured to discharge both the exhaust gas 20 from the core nozzle 30 and the exhaust gas 20 from the core nozzle 30 as a mixed flow.

A lobe mixer 42 is disposed inside the exhaust nozzle 40 and is suitably attached to the aft end 26 of the core cowl 22 and spaced radially outwardly from the exhaust centerbody 24. Mixer 42 operates to mix fan air 36 from fan nozzle 38 and exhaust gas 20 from core nozzle 30 prior to discharging the combined stream from exhaust nozzle 40 . The combination of the mixer 42, the exhaust center body 24, the fan nozzle 38, the core nozzle 30, and the exhaust nozzle 40 is the engine 10.
An exhaust system 12 is configured.

An example of a typical lobe mixer is U.S. Patent No.
It is described in No. 4240252 and No. 3861140.

An example of a suitable mixed flow gas turbine engine including a lobe mixer is described in US Pat. No. 4,147,029.

In one form of the invention, an improved exhaust system 12 including a mixer 42 and an exhaust center body 24 is shown in more detail in FIG. This improved exhaust center body 24 has a lobe-shaped mixer 4
2, without substantially increasing the pressure loss,
It includes means 44 for enhancing the mixing effect of the exhaust system 12.

In one embodiment, the means 44 include the center body 2
4 includes a plurality of circumferentially spaced deformed portions 44 provided at an intermediate portion 46 of a radially outer surface 48 of the radially outer surface 48 . More specifically, in FIGS. 2 and 3, the center body 24 is corrugated or configured with spaced apart pleats and has a nominal reference plane 52 at the intermediate section 46.
It includes a plurality of circumferentially spaced indentations or grooves 50 extending radially inwardly relative to the recesses or grooves 50 . Reference plane 52 represents the outer surface of a typical conventional center body without deformed portion 44 . Each groove 50 also extends generally axially through intermediate portion 46 and is aligned generally parallel to longitudinal axis 54 of centerbody 24 . When the center body 24 is installed in the engine 10, its longitudinal axis 54 is as shown in FIG.
It is aligned with the longitudinal axis 18 of the engine 10.

Centerbody 24 also has a plurality of ridges 56 extending radially outwardly relative to nominal plane 52 . Each ridge 56 also extends generally axially through the intermediate portion 46 and is disposed between and parallel to adjacent grooves 50 .

3 and 4, the lobe mixer 42 and centerbody 24 are shown in more detail.
Lobe mixer 42 is circumferentially spaced and has a plurality of alternating radially inner lobes 58 and radially outer lobes 60. An inner lobe 58 extends from the aft end 26 of the core cowl 22 and slopes axially rearward relative to the direction of flow to a reduced diameter at the mixer discharge plane 62 shown by line 4-4. ing. Inner lobe 58 is generally U-shaped and cooperates with generally parallel spaced apart sidewalls 64 to form a cold chute or channel 66 . Cold chute 66 is in flow communication with fan nozzle 38 .

The outer lobes 60 are also located at the rear end 26 of the core cowl 22.
and slopes rearwardly to a larger diameter compared to the reduced diameter of inner lobe 58. The outer lobe 60 is also generally U-shaped;
In cooperation with sidewall 64, a hot chute or channel 68 is likewise formed. Hot chute 68 is in flow communication with core nozzle 30 .

In FIG. 3, the radially outer surface 48 of the center body 24 has a front portion 70 and a rear portion 72 with an intermediate portion 46 therebetween. All these parts are arranged coaxially around the longitudinal axis 54 of the center body 24. A rear portion 72 slopes radially inwardly rearwardly from the intermediate portion 46 . A forward portion 70 slopes forwardly and radially inwardly to suitably attach to the core engine 16 and support the centerbody 24 relative to the core engine.

The center body 24, including the nominal surface 52, is shown in detail in FIGS. 3, 4, and 5. Side 5
2 is a groove 50 and a ridge 56 of the center body 24;
It is used to express the arrangement of. Groove 50 has a generally arcuate concave cross section and extends radially inwardly from nominal surface 52 . Each groove 50 is connected to the mixer 4
The outer lobes 60 of the two outer lobes 60 are preferably substantially axially parallel aligned with and directly opposite the outer lobes 60 of the outer lobes 60 of the two.

Ridge 56 has a generally arcuate convex cross section and extends radially outwardly from nominal surface 52 . Preferably, each ridge 56 is generally axially parallel aligned with and directly opposed to a respective inner lobe 58.

In Figures 3 and 5, hot chute flow area 7
4 is configured in the mixer discharge plane 62 and represents the unit flow area through which the hot exhaust gas 20 exits the core nozzle 30. Mixer discharge plane 62 is defined as a plane passing through intermediate portion 46 of centerbody 24 and generally aligned with the rear end of lobe mixer 42 .

It is known to those skilled in the art that the hot shoot flow area 74 of a typical mixed flow exhaust system is a predetermined fixed value based on selected parameters of the engine's thermodynamic cycle. The geometric parameters of the exhaust system as described above are then adjusted while maintaining the hot chute flow area 74 at the predetermined value.
It is chosen to provide a compromise between mixing efficiency and mixer pressure loss.

In conventional center bodies, the hot chute flow area 74 typically has a flow cross-section defined by the inner surface of the mixer 42 and the outer surface of the center body 24 as represented by the nominal surface 52. Area is defined as divided by the number of inner lobes 58 or outer lobes 60. Typically, there will be an equal number of inner lobes 58 and outer lobes 60, preferably 18 each, although other numbers may be used.

In the preferred embodiment of the invention described above,
The center body 24 and the lobe mixer 42 are
The prior art has been strategically reconfigured to provide enhanced mixing efficiency compared to typical mixed flow exhaust systems without substantially increasing pressure drop. However, although the centerbody 24 has been reconfigured, the hot chute flow area 74 preferably remains the same as in conventional exhaust systems.

Accordingly, when provided with the centerbody 24 of the present invention, instead of what was previously described, the hot chute flow area 74 includes the inner surface of the adjacent half of the inner lobe 58, the outer lobe 60, the side wall 64, Groove 5
0 and the adjacent half of the ridge 56 of the center body 24.

In this regard, as shown in more detail in FIG. 5, each ridge 56 of the center body 24 has a ridge-shaped cross-sectional area 76 defined as the area bounded by the convex outside of the ridge 56 and the nominal surface 52. have. Similarly, each groove 50 has a channel-shaped cross-sectional area 78 that defines the area bounded by the concave outer surface of the groove 50 and the nominal surface 52. The ridged area 76 is chosen to be equal to the grooved area 78 and the groove 50
Preferably, the increase in flow area due to ridge 56 is offset by the decrease in flow area due to ridge 56. Thus, the hot chute flow area 74 remains at the predetermined size based on the thermodynamic cycle parameters previously discussed, even with the ridges 56 and grooves 50 in the centerbody 24.

3 and 4, the radius of the center body 24 at the ridge 56 or the ridge radius R ₁ relative to the longitudinal axis 54 of the center body 24 at the groove 50.
The value obtained by subtracting the radius of 4 or groove radius R ₂ is the depth d
, which has a maximum value D at the discharge plane 62 of the mixer. To reduce parasitic pressure losses attributable to the center body 24, the grooves 50 and ridges 56 of the intermediate section 46 are connected to the front section 70 of the center body 24.
and aerodynamically merge with the rear portion 72 .

More specifically, the depth d varies from the maximum value D at the mixer discharge plane 62 to the point of connection between the intermediate section 46 and both the rear section 72 and the front section 70 of the center body 24. It changes to a value of approximately zero. Therefore, the ridge 56 and the groove 50 aerodynamically merge forwardly at the front merging region 80 and rearwardly at the aft merging region 82 of the center body 24 .

Using the centerbody 24 of the present invention using grooves 50 and ridges 56, a predetermined hot chute flow area 74, and the aerodynamic merging of grooves 50 and ridges 56 at the outer surface 48, the centerbody 24 of the present invention provides improved performance compared to the prior art. hand,
It should be appreciated that an improved exhaust system 12 is obtained which acts to significantly enhance mixing efficiency without substantially increasing parasitic pressure losses. As a result,
The fuel consumption rate of engine 10 is improved.

In another embodiment of the exhaust system 12, the hot chute flow area 74 as shown in FIG.
Even if the constituent areas 78 and 78 are not equal, they can remain constant. For example, ridge 5
By moving the side walls 64 of the mixer 42 closer and further apart in a predetermined manner to compensate for any net change in the flow area of the hot chute due to unequal grooves 6 and 50. It can be achieved.

Having thus described what are considered to be preferred embodiments of the invention, many modifications will occur to those skilled in the art from the foregoing description.

For example, the center body 24 may have only either the groove 50 or the ridge 56. Third
The depth d in the figure is the groove 50 or ridge 5 from the nominal surface 52.
The radial extent of 6 is shown. Ridge 56 and groove 50
Although described as having an arcuate cross-section, they may have other cross-sections, such as a V-shape.

Additionally, various types of mixers 42 may be used in conjunction with centerbody 24. In one embodiment, the mixer 42 can have a side wall 64 as shown in FIG. 3 with a rearward facing or shell-shaped indentation (not shown).

Although the invention has been described above, it should be understood that the scope of the invention is limited only by the claims.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of a high bypass ratio mixed flow gas turbine engine as an example using one type of exhaust system of the present invention, and FIG. 2 includes a lobe mixer and an exhaust center body of the present invention. A perspective view showing a part of the exhaust system in Figure 1 in cross section, Figure 3.
The figure is a detailed sectional view of the lobe mixer and exhaust center body in Figure 2, Figure 4 is an end view of the mixer and exhaust center body in Figure 3 taken along line 4--4, and Figure 5 is a cross-sectional view showing the mixer and exhaust center body in Figure 3 in detail. Figure 4 is an enlarged cross-sectional view of a portion of the mixer and exhaust centerbody of Figure 4 showing its flow cross-sectional area; Explanation of main symbols, 24: Center body, 4
6: Middle part, 50: Groove, 70: Front part, 7
2: Rear part.

Claims (1)

[Scope of Claims] 1. A fan; a core engine disposed downstream of the fan and coaxially with the fan around a longitudinal axis of the engine; and circumferentially disposed around the core engine. a core cowl extending from a rear end of the core engine and spaced radially inwardly from an inner surface of the core cowl for discharging gas from the core engine; an exhaust center body disposed circumferentially around the fan and core engine, spaced radially outwardly from the core cowl and downstream of the fan to provide a passageway for fan air; an annular fan nozzle forming an annular side passage duct and cooperating with the rear end of the core cowl to discharge fan air from the side passage duct; a nacelle extending downstream and forming an exhaust nozzle for discharging both fan air from the fan nozzle and gas from the core nozzle, the exhaust center body having a radially outer surface; an annular member having an outer surface including a front portion, a middle portion, and a rear portion disposed coaxially about the longitudinal axis of the engine, the rear portion of the outer surface extending from the middle portion; radially inwardly inclined in a rearward direction, said intermediate portion being corrugated and defining a plurality of circumferentially spaced apart ridges, each groove and ridge extending generally axially through said intermediate portion; Turbofan engine. 2 The turbo fan described in claim 1
In an engine, each groove and ridge extends axially to a forward and aft portion of the outer surface, respectively, and the radial extension of each groove and ridge has a substantially zero magnitude. A turbofan engine that aerodynamically merges the front and rear portions of the groove and ridge at the outer surface. 3 The turbo fan described in claim 1
In the engine, each ridge extends radially outwardly from a reference surface of said intermediate portion to define a ridge-shaped cross-sectional area between said outer surface and said reference surface, and each groove extends radially outwardly from said reference surface. a turbofan engine extending radially inwardly from an outer surface thereof to define a groove-shaped cross-sectional area between an outer surface thereof and the reference surface, the ridge-shaped cross-sectional area being equal to the groove-shaped cross-sectional area. 4 The turbo fan described in claim 1
A turbofan engine, wherein a forward portion of the outer surface slopes forwardly and radially inwardly from an intermediate portion of the outer surface. 5 a fan; a core engine disposed downstream of the fan and coaxially with the fan around a longitudinal axis of the engine; and a core cowl disposed circumferentially around the core engine; an exhaust centerbody extending from a rear end of the core engine and spaced radially inwardly from an inner surface of the core cowl and defining a core nozzle for discharging gas from the core engine; an annular shunt duct disposed circumferentially around the fan and the core engine, spaced radially outwardly from the core cowl, and downstream of the fan for passage of fan air; an annular fan that cooperates with the rear end of the core cowl to discharge fan air from the duct;
a nacelle that constitutes a nozzle and further extends downstream from the rear end of the core cowl and constitutes an exhaust nozzle that discharges both fan air from the fan nozzle and gas from the core nozzle; , disposed at the rear end of the core cowl, including a plurality of inner lobes and outer lobes arranged alternately and spaced apart in the circumferential direction, the outer lobes facing rearward with respect to the inner lobes; a lobe-shaped mixer that is sloping and wherein the outer and inner lobes define a hot and cold chute, respectively, in flow communication with the core nozzle and fan nozzle, respectively; is comprised of an annular member having a radially outer surface, the outer surface including a front portion, an intermediate portion and an aft portion coaxially disposed about the longitudinal axis of the engine; portions are spaced radially inwardly from said lobed mixer, said rearward portion of said outer surface slopes radially inwardly rearwardly from said intermediate portion, said intermediate portion being corrugated and circumferentially spaced apart; A turbofan engine forming a plurality of grooves, each groove extending radially inward from a reference surface of the intermediate section and generally axially through the intermediate section. 6 The turbo fan described in claim 5
In the engine, the intermediate portion of the outer surface of the annular member has a plurality of ridges elongated in the axial direction, each ridge being disposed between adjacent grooves and forming a reference surface of the intermediate portion. a turbofan extending radially outwardly from the lobed mixer, with each groove facing a respective one hot chute of the lobed mixer and each ridge facing a respective one cold chute of the lobed mixer; ·engine. 7 The turbo fan described in claim 6
In the engine, the outer surfaces of the grooves and ridges and the inner surfaces of the hot and cold shute define a hot shute flow zone therebetween, the flow zone comprising:
A turbofan engine having a hot shute flow area that is substantially equal to the reference plane of the intermediate portion of the annular member. 8. In an exhaust center body used in a mixed-flow turbofan engine that includes a core engine, a fan air bypass duct, and a lobe mixer that mixes the fan bypass air with the core engine combustion gas, an annular member having a radially outer surface disposed coaxially about an axis, the outer surface having an intermediate portion operatively spaced radially inwardly from the lobe-shaped mixer; The portion is corrugated and has a plurality of circumferentially spaced apart grooves, each groove extending radially inwardly from a reference surface of the intermediate portion and generally axially through the intermediate portion, the intermediate portion further comprising: It has a plurality of axially elongated ridges, each ridge being disposed between adjacent grooves and extending radially outward from the reference plane of the intermediate section, each ridge having a surface extending from its outer surface and An exhaust center body defining a groove-shaped cross-sectional area between the reference surfaces, each groove defining a groove-shaped cross-sectional area between its outer surface and the reference surface, said edge-shaped cross-sectional area being equal to the groove-shaped cross-sectional area.