JPS5852337Y2 - fan engine silencer - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a silencing device for a turbofan engine.

In the turbofan engine, which has been widely used as an aircraft engine in recent years, as shown in Figure 1, a turbine a turns a fan b attached to the front of the engine, and the air flows through a duct e and around a dient nozzle d. It's starting to gush.

In a turbofan engine, fan b is the main noise source, and in order to effectively reduce noise in a specific frequency range such as fan noise, the use of porous materials as sound absorbing materials has a remarkable effect. is known to exhibit.

However, this porous material has limitations in its use under conditions where it is exposed to high-speed airflow, such as in engines, so conventional sound absorbing materials with a structure that does not use porous materials, called resonance type, as shown in Figure 2, have been developed. has been mainly used.

This resonance-type sound absorbing material e has a structure that combines a perforated plate fs and a Nicumcore g1 bottom plate, and the sound absorbing material e is attached to the duct c of the turbofan engine shown in Fig. 1 above, and is used to absorb high-speed airflow. was made to flow along the side of the perforated plate f.

This sound-absorbing material e has a simple structure and can sufficiently withstand environmental conditions such as high-speed airflow, but the frequency band in which it exhibits an effective acoustic noise reduction effect is narrow, and it has a narrow frequency band that is useful for aircraft engines from takeoff to landing. It was difficult to obtain an effective sound absorption effect over the entire operating range.

In view of the above-mentioned circumstances, the present invention uses a porous material that can withstand high-speed airflow without sacrificing its good acoustic properties, in order to satisfy the demand for lower noise from aircraft, which is expected to become even more severe in the future. The purpose of this device is to provide a noise reduction device for a fan engine, in which a resin-treated porous material is bonded to a perforated plate for holding the porous material, and the porous material is bonded to a bottom plate that also serves as a duct wall surface. It is characterized by the fact that the material is removably attached.

Embodiments of the present invention will be described below with reference to the drawings.

In FIG. 3, reference numeral 1 designates a flange to be attached to a duct of a turbofan engine, and a bottom plate 2, which also serves as a duct wall surface, is formed by bending the end of the flange 1, and a felt support fitting 3 is joined to the bottom plate 2. While maintaining a constant distance between the felt support fitting 3 and the felt support fitting 3, the felt 5 as a porous material bonded to the perforated plate 4 is detachably attached to the felt support fitting 3 using a pad 6 and screws 7.

The felt 5 contains a synthetic resin to increase its strength to withstand the environmental conditions of an aircraft engine, and the perforated plate 4 bonded to the felt 5 wraps around the ends of the felt 5 to reinforce the felt 5. The end portion 4b of the perforated plate 4 is bent to the back side of the perforated plate 4.

Note that the holes 4a formed in the perforated plate 4 are relatively thick, that is, the holes 4a are formed in the shape of a dog from the resonant sound absorbing material so as not to impair the acoustic characteristics of the felt 5 (see Fig. 4). ).

In addition, an appropriate number of spacers 8 for holding the space between the felt 5 and the bottom plate 2 and reinforcing lips are removably attached to an appropriate position in the middle part of the felt 5 using pads 6 and screws 7, and the bottom plate 2 and the felt 5 are An air layer 9 is formed by maintaining a constant distance between the two.

When the sound damping device of the present invention with the above configuration is installed and used in the duct of a turbofan engine, the perforated plate of the conventional resonance type sound absorbing material is replaced with the felt 5. The vibration system consisting of viscous resistance, the inertial reactance of the air contained in the felt 5, and the capacitive reactance of the air layer 9 can provide a noise reduction effect in a wider frequency band than a resonance type sound absorbing material.

Furthermore, since the felt 5 is impregnated with resin and is bonded to the perforated plate 4, it has mechanical strength capable of withstanding environmental conditions such as high-speed airflow from an engine.

It should be noted that the present invention is not limited to the above-mentioned embodiments, and it goes without saying that other porous materials may be used instead of felt, and that various other changes may be made without departing from the gist of the present invention. be.

As mentioned above, according to the present invention, (1) noise over a specific frequency range, such as fan noise of a turbofan engine, can be absorbed over a wider range of the engine than with conventional resonant sound absorbing materials; Can be reduced more effectively.

(2) The porous material used to achieve the acoustic properties is
The resin coating is bonded to a perforated plate and protected by the perforated plate, which overcomes the mechanical weaknesses of porous materials and allows it to withstand harsh conditions such as those found in aero engines. can be used.

(3) Since the porous material bonded to the perforated plate can be removed from the duct, it can be easily replaced in the event of damage, resulting in good maintainability.

By replacing the porous material with a porous material having different characteristics, a muffler with different acoustic characteristics can be obtained.

(4) Since the structure is simple, it exhibits excellent effects such as easy assembly.

[Brief explanation of the drawing]

Figure 1 is a conceptual diagram of the turbofan engine of the present invention, Figure 2
The figure is an explanatory diagram of a conventional example, FIG. 3 is an explanatory diagram of an embodiment of the present invention, and FIG. 4 is a detailed diagram of a perforated plate. 2...Bottom plate, 4...Perforated plate, 5...
...Felt as a porous material, 9...
air layer.

Claims (1)

[Scope of utility model registration request] A resin-treated porous material is bonded to the perforated plate for holding the porous material, and the outer peripheral edge of the perforated plate wraps around the edge of the porous material to form the back surface of the perforated plate. The perforated plate, which is formed by bending along the sides and is integral with the porous material, is removably fixed to a bottom plate that also serves as the duct wall surface, and the perforated plate, which is integral with the porous material, is 1. A fan engine silencer, characterized in that an air layer having a predetermined width is formed between the plate and the plate.