JPH0526944B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an aircraft gas turbine engine system, and more particularly to the use of air discharged from the inside of a nacelle cowling or nacelle compartment.

The concept of the present invention is that the thrust is 20,000 to 60,000 lb (9 to 27
Although it was devised for large turbofan engines in the ton class, it can be widely applied to other engines as well.

BACKGROUND OF THE INVENTION A gas turbine engine to which the concept of the present invention is applied is housed in an aircraft engine nacelle or means for providing a hydrodynamic smooth shape called a nacelle cowling. Nacelle cowlings cover engine accessory parts that are mounted on the exterior of the engine case to reduce fluid resistance created by and protect the parts. The venting of air by the nacelle compartment defined inside the nacelle cowling prevents overheating of parts located within the nacelle compartment and prevents flammable materials from entering the nacelle compartment due to accidental leakage of the fuel pipes. This prevents gas from accumulating.

Historically, there have been three main sources of air entering the nacelle compartment: That is, the first is air provided to the parts to cool them, and the cooling air is sent to the compartment after cooling. The second is the portion of the engine main airflow that inevitably leaks between the flanges of the engine case into the nacelle compartment. Third, there is fan duct flow air that leaks into the nacelle compartment through a compartment door seal extending at the upstream end of the nacelle. In many power plants, such air within the nacelle compartment is naturally vented through a gap in the nacelle cowling that extends to the downstream end of the nacelle compartment. In the past, such air flow rates were sufficiently adequately vented from the compartment that little attention was paid to the actual pressure of the air flowing through the nacelle compartment.

JT9D- manufactured by Pratt & Whittney Aircraft Company (a division of United Technologies Corporation)
Recent commercial aircraft gas turbine engines, such as the 7R4 engine, have a radial engine that brings the thermal expansion displacements of the stator and rotor parts closer together, causing fluid loss between them. 〓
Active clearance control device or wing tip radial that acts on most of the engine to reduce clearance
Built-in interval control device. Basically, cooling air or possibly heated air is injected onto the outer wall of the engine case in the area to be controlled;
This causes the required contraction or expansion of the part. U.S. Patent No. 4,069,662 “Clearance Control Device for Gas Turbine Engine,” U.S. Patent No.
No. 4019320, “External Cooling for a Gas Turbine Engine Clearance Control System,” and U.S. Pat.
No. 4,279,123, ``External Cooling for a Gas Turbine Engine Clearance Control System,'' is representative of the concept employed in active clearance control that acts on the engine from outside the engine.

Generally, such active clearance control devices extract low pressure cooling air from the engine fan stream and direct it to a manifold surrounding the area of the case to be cooled. The introduced cooling air exits the manifold and impinges directly onto the engine case. This allows the engine case to be cooled by both impingement cooling and convection cooling. In designing engines with such systems, it is conventional to maintain fairly low backpressure in the nacelle compartment so that the flow exiting the manifold is accelerated to the highest possible velocity to provide effective impingement cooling. more demanded. A suitably sized gap is provided in the nacelle cowling at the downstream end of the nacelle compartment, which vents air from the nacelle compartment to lower the back pressure in the nacelle compartment below atmospheric pressure.
The value is set to about 0.5 psi (3.5×10 ⁻² Kgf/cm ² ).
The flow rate through the nacelle compartment is typically 3 to 4 lb/s (1.4 to 1.8 kg), and a leakage area on the order of 100 in ² (645 cm ² ) is required to maintain the required low backpressure in the nacelle compartment. Needed.

Problems to be Solved by the Invention It has long been recognized that one way to make constructive use of the air in the nacelle compartment is to perform backward exhaust to reuse part of the energy of these working fluids. However, the size of the exhaust nozzle required in conventional engines seemed to have a detrimental effect on the characteristics of the airflow passing through or around the engine. . In addition, the amount of thrust increase achieved by evacuation of compartments with conventionally required low backpressures was expected to be very small.

Therefore, the present invention seeks a new technique for utilizing the exhaust air from the nacelle compartment, taking into account the overall engine system.

SUMMARY OF THE INVENTION According to the present invention, the nacelle compartment of an aircraft power plant from which air from the active clearance control system is exhausted during high-altitude steady flight is 1 to 2.5 psi below the ambient pressure outside the power plant.
It operates under pressure as high as (7.0×10 ⁻² to 17.6×10 ⁻² Kgf/cm ² ) and is exhausted by a compartment exhaust nozzle installed toward the rear.

According to one particular embodiment of the invention, the aft-facing nozzle is an essentially annular hole extending around the outer periphery of the nacelle compartment. In another detailed embodiment, the aft-facing exhaust nozzle of the turbo fan power plant is located a portion of the circumference of the fan section.

The main features of the invention are the pressurized nacelle compartment and the rear-facing exhaust nozzle. Although cooling air for active clearance control is sent to a pressurized compartment, during high-altitude steady flight the pressure within the compartment is 1 to 2.5 psi (7.0 x 10 ^-2 to 7.0 x 10 -2 17.6×
10 ^-2 Kgf/cm ² ) and is discharged from the rear-facing compartment outlet. In one particular embodiment, the exhaust flow from the nacelle compartment is routed through a conduit that crosses the engine fan flow and is exhausted to the atmosphere outside the engine fan section. In another detailed embodiment, the exhaust nozzle is formed extending circumferentially around the nacelle compartment. The area of the nacelle exhaust hole is such that the compartment pressure is 1 to 2.5 psi (7.0 x 10 ^-2 to 17.6 psi) lower than atmospheric pressure during high-altitude steady flight.
×10 ^-2 Kgf/cm ² ).

OPERATION The main advantage of the present invention is that the engine thrust is greater than engines with unpressurized nacelles when compared at the same fuel flow rate. Fuel consumption is therefore reduced, resulting in more economical operation of the engine. Improvements in pressurized nacelles are achieved by optimizing the balance between the increase in thrust provided by evacuation of the nacelle compartment and the reduction in thrust due to less effective cooling. If the pressure in the nacelle compartment is higher than the pressure specified in this invention, the loss of cooling effect is greater than the thrust increase.

The above features and advantages of the invention will become more apparent from the following detailed description of the best mode of operation of the invention and the accompanying drawings.

Embodiment The present invention aims to improve the overall efficiency of a gas turbine engine during high-altitude steady flight (35,000 ft (10,670 m), Matsuha number 0.8). An embodiment in a fan engine will be described below. The engine mainly consists of a fan section 12 and a core section 14.
It is formed by. Core section 14 is further divided into compressor 16, combustor 18, and turbine 20. Air flow 22 toward the engine inlet 24 is divided into a core flow 26 and a fan flow 28 . The core flow passes through a compressor, a combustor, a turbine, and exits through a core nozzle 30. The fan flow is a single row or sub-sequence of fan blades 3
2 and is discharged from the fan nozzle 34.
Engine case 36 includes compressor 16 and combustor 18
and the turbine 20. Engine accessories such as an ignition system 38 and an electronic fuel control system 40 are mounted on the outside of the engine case 36 and surrounded by a nacelle air ring or cowling 44. The nacelle cowling 44 is configured with a smooth profile to minimize air resistance to fan flow and cooperates with the engine case 36 to define the nacelle compartment 46. Accessories such as the ignition system 38 and fuel control system 40 are often installed in the nacelle compartment 4.
It is cooled by the air that is finally sent into 6.

A fan case 48 surrounds the blades of fan portion 12. A structure 50 extends upstream from the fan case to form the inlet 24, while a structure 52 extends downstream and cooperates with the nacelle cowling 44 to form the fan nozzle 34.

The illustrated engine has active clearance control system functionality and includes one or more cooling air manifolds 54 located around the engine case. Although only the manifold around the turbine 20 is shown in the figure, a similar manifold can also be placed around the compressor 16. The cooling air is supplied to the nacelle cowling 4 upstream of the fan nozzle 34, for example.
A port 56 located on 4 supplies the manifold. The supplied air is blown against the engine case 36 through inwardly drilled holes in the manifold under steady flight conditions, reducing the temperature of the engine case and thereby increasing the temperature of the stator seal supported inside the case. Shrink the diameter. By contracting the diameter of the stator seal during steady flight conditions, the stator seal will mesh more closely with its opposing rotor seal. Engine efficiency is therefore improved by reducing air leakage between seals.

During high-altitude steady flight of the above power plant (35000ft
(10670m) When driving at Matsuha number 0.8),
Since a significant amount of cooling air is pumped into the nacelle compartment, that air must be vented from the compartment. In addition to cooling air, air leaking between adjacent engine case flanges and air leaking into the interior of the fan section between the mating ends of the nacelle cowling must also be exhausted from the nacelle compartment.
When a large engine, such as the JT9D-7R4 turbofan engine, is operating under steady-state flight conditions with active clearance control, the airflow to be exhausted is 3-4 lb/s (1.4 lb/s).
~1.8Kg). Exhaust in at least one power plant employing such an engine involves directing the air flow through a conduit that crosses the fan flow 28 and then in a rearward direction through a rearward facing exhaust nozzle 58 disposed about the circumference of the fan section 12. This is achieved by allowing the gas to be released into the atmosphere. The pressure inside the nacelle compartment is 1~
It is 2.5 psi (7.0×10 ⁻² to 17.6×10 ⁻² Kgf/cm ² ) high, and therefore the pressure difference between the inside and outside of the rearward-facing exhaust nozzle is also about that level.

The rearwardly directed exhaust nozzle 58 located around the fan section is shown in more detail in the perspective view of FIG. Other types of nozzles include a nozzle located at an intermediate location 60 along the nacelle cowling 44 in FIG. 3A and a core exhaust nozzle 30 located at the rear end 62 of the nacelle cowling 44 in FIG.
The nozzle is shown positioned in close proximity to the nozzle.

The present invention not only provides additional benefits by discharging the flow in the direction of increasing engine thrust, but also by maintaining a pressurized condition within the nacelle compartment, which provides an optimal value for the total engine thrust. It is also recognized that this can be achieved. As an example, FIG. 4 illustrates the relationship between the cooling effect of the active clearance control system and exhaust back pressure (pressure in the nacelle compartment) in an engine such as the JT9D-7R4. As the back pressure on the exhaust side of the active clearance control device manifold increases, the cooling effectiveness, measured as the ability to remove heat from the engine case, decreases. This is primarily due to the reduced pumping speed as the pressure differential across the manifold decreases. The cooling capacity of the JT9D-7R4 engine without the pressurized nacelle is shown as a bottom value as indicated by 80. When increasing the compartment pressure at constant supply pressure, the cooling capacity measured as a percentage of the bottom value is curve 8.
It decreases as shown by 2. The initial reduction in cooling effectiveness is small, but increases as the compartment back pressure approaches the supply pressure. Nacelle compartment pressure is 1~1 than atmospheric pressure 86
When within the 2.5 psi (7.0 x 10 ^-2 - 17.6 x 10 ^-2 Kgf/cm ² ) high range 84, the reduction in cooling effectiveness is less than 30%. The improvement in fuel efficiency obtained through the use of active clearance control in the JT9D-7R4 engine is due to the fuel consumption rate (TSFC,
The fuel consumption rate per unit thrust is approximately 1%. This decrease in efficiency with increasing compartment backpressure is illustrated by curve 90 in FIG. As the compartment back pressure approaches the supply pressure, the 1% mentioned above cancels out.

Figure 5 also shows that the fuel consumption rate can be increased by venting the compartment exhaust flow backwards.
A curve 92 is drawn showing how the TSFC decreases. By exhausting the same flow under higher pressure differentials resulting from increased compartment pressure, fuel consumption is reduced. By combining the effects shown in curves 90 and 92, net fuel consumption curve 92 is obtained. As can be seen from the figure, the optimal value of fuel consumption rate (TSFC) is
Compartment pressure is 4.5~6.0psi (31.6× ^10-2 ~
42.2×10 ^-2 Kgf/cm ² ) or the compartment pressure is 1 to atmospheric pressure.
Obtained when in the high pressure range of 2.5 psi (7.0×10 ⁻² to 17.6×10 ⁻² Kg/cm ² ).

Accordingly, gas turbine engines employing the concepts of the present invention are capable of operating with higher fuel efficiency than comparable conventional engines.

Although it is not directly related to engine thrust,
A high level of nacelle pressure has the additional advantage of allowing the cross-sectional area of the exhaust nozzle to be smaller. Compartment pressure is 1 to 2.5 psi (7.0×10 ^-2 to 17.6×10 ^-2 Kgf/
^cm2 ) The cross-sectional area of the exhaust nozzle is designed as high as the compartment pressure is 0.5psi above atmospheric pressure
(3.5×10 ⁻² Kgf/cm ² ) substantially smaller than the cross-sectional area of the exhaust nozzle designed to be higher or lower. In the former case, weight is reduced and the adverse hydrodynamic effects on the surrounding airflow that occur in larger nozzles are reduced.

Although the present invention has been described in detail with respect to specific embodiments above, the present invention is not limited to these embodiments, and various embodiments are possible within the scope of the present invention. will be clear to those skilled in the art.

[Brief explanation of the drawing]

FIG. 1 is a schematic perspective view of a gas turbine power plant with a portion of the nacelle cowling cut away to reveal the nacelle compartment. FIG. 2 shows the nacelle compartment exhaust nozzle arranged around the fan section. Figures 3A and 3B illustrate another embodiment of nacelle compartment exhaust nozzles disposed circumferentially around the aft portion of the nacelle cowling. FIG. 4 is a graph showing how the cooling capacity of the active clearance control device decreases as the back pressure within the core increases. FIG. 5 is a graph showing the change in fuel consumption rate versus nacelle compartment pressure. 12...Fan part, 14...Core part, 16
... Compressor, 18 ... Combustor, 20 ... Turbine, 22 ... Air flow, 24 ... Inlet, 26 ...
Core flow, 28...Fan flow, 30...Core nozzle, 32...Fan blade row, 34...Fan nozzle, 36...Engine case, 38...Ignition device, 40...Electronic fuel control device, 44...Nacelle Cowling, 46... Nacelle compartment, 48... Fan case, 50, 52... Structure, 54... Cooling air manifold, 56... Port, 58... Exhaust nozzle, 60... Intermediate position of nacelle cowling, 62 ... Rear end of nacelle cowling, 80 ... Bottom price, 82 ... Decreasing curve, 84
...Range, 86...Atmospheric pressure, 90...Decrease curve, 92...Curve for backward exhaust, 94...
Composite curve showing net fuel consumption.

Claims (1)

[Scope of Claims] 1. A gas turbine engine housed in a nacelle compartment defined inside a nacelle cowling of an aircraft, comprising an engine case 36;
means 54 for injecting cooling air toward the engine case 36 within the nacelle compartment to cool and shrink the diameter of the case 36 during high-altitude steady flight; and adjusting the pressure of the air within the nacelle compartment. pressure regulating means for controlling the air pressure within the compartment during high altitude steady flight, the pressure regulating means including an exhaust nozzle 58 for allowing air to flow out of the nacelle compartment; 1~ than the atmospheric pressure outside the aircraft
It has dimensions to maintain a high level of about 2.5 psi (7.0×10 ^-2 to 17.6×10 ^-2 Kgf/cm ² ) and is installed to exhaust the air backward with respect to the direction of travel of the aircraft. A gas turbine engine characterized by: 2 a gas turbine engine mounted on the aircraft and housed in a nacelle compartment 46 defined inside a nacelle cowling and a cooling air manifold 54 extending around the engine; A method for operating an aircraft power unit that performs active clearance control to control direction and distance, the method comprising: introducing air for the active clearance control into the nacelle compartment 46, and further injecting the air to the engine. , the air pressure in the nacelle compartment 46 is set to 1 to 2.5 psi below the atmospheric pressure outside the power plant during high-altitude steady flight.
(7.0×10 ^-2 to 17.6×10 ^-2 Kgf/cm ² ); and exhausting the air in the compartment 46 backwards with respect to the direction of travel of the aircraft. A method characterized by: