JPH0419262A - Small hovercraft - Google Patents

Abstract

PURPOSE:To reduce the generation of noise of a fan for propulsive floating by forming an annular air inflow port for floating in the inner surface of an introduction flow duct and on the downstream side of a fan and opened in a staged manner in the direction of an upper stream, and guiding intake air to an air cushion chamber. CONSTITUTION:A fan 1 is mounted on the rear part of a ship hull 3 in a manner that the tip part of a fan moving blade is surrounded with the inner wall of an introduction flow duct 4 formed in a hollow blade shape in cross section so that air resistance is reduced and buoyancy is increased. An air intake port 5 for floating opened in a staged manner toward an upper stream is formed in an annular manner in the inner surface of the duct 4, and the hollow part of the introduction flow duct is communicated to an air flow passage 7 for floating. After air flowing through an air intake port 5 to the hollow interior of the duct 4 with the aid of the fan 1 flows through the hollow part of the introduction flow duct along a peripheral direction, the air flows down to the interior of the ship hull. The air flows through an air flow passage 7 for floating and flows through an injection nozzle 8, formed in the outer periphery of the ship hull, to an air cushion chamber and works as buoyancy. A delivery air flow at the central part of the fan is discharged directly to the rear of the ship hull to produce thrust.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a small hovercraft, and particularly to noise reduction of a fan that serves both for propulsion and levitation.

[Conventional technology]

In the small hovercraft that has been used conventionally, the 4th
As shown in the side view of the drawing and the construction plan of drawing 5, a flow guide duct 4 surrounded by a wing-shaped upper half in cross-section and a concave lower half at the rear of the hull 3 is used for propulsion and flotation. Fan 1 is installed coaxially. Immediately after the fan of the flow guiding duct 4, as shown in the partial vertical cross-sectional view of FIG. The air is dammed up and diverted to the floating air flow path 7, and is ejected from the ejection port 8. 2 is an engine that drives the fan 1.

In this type of hovercraft, the air discharged from the propulsion and levitation fan 1 flows backward in the flow guide duct 4 to generate thrust, and the air diverted from the dam 6 passes through the levitation air flow path 7 and jets out. It ejects from the outlet 8 and fills the air cushion chamber, creating buoyancy and traveling while floating on the sea surface, etc.

[Problem to be solved by the invention]

However, if a dam is installed downstream of a propulsion flotation fan to collect flotation air, the back pressure at the dam increases, resulting in uneven flow distribution of the airflow discharged from the fan up and down. The air flow becomes uniform and the air flowing into the rotating fan blades has high pressure in the dam area and low pressure in other parts, which causes the air flow to fluctuate periodically and generate loud noise, which interferes with passengers' conversation. It often comes.

The present invention was proposed in view of the above circumstances, and an object of the present invention is to provide a small hovercraft that reduces the noise of a propulsion and levitation fan.

[Means to solve the problem]

To this end, the present invention provides a hovercraft having an annular flow guide duct that coaxially surrounds a fan that simultaneously discharges propulsion air and levitation air, in which the flow guide duct is formed so that the inside of its airfoil cross section is hollow; , an annular floating air inlet is provided on the inner surface of the flow guiding duct and opens stepwise toward the upstream on the downstream side of the fan, and the air taken in from the floating air inlet is introduced into the air cushion chamber. It is characterized by being made to do.

[Effect]

According to this configuration, the air for floating is taken in uniformly in the circumferential direction from the discharge air flow of the fan by the hollow guide duct having the annular air intake for floating on the inner surface, so that the back pressure of the fan is reduced. The circumferential distribution becomes uniform, and the noise of the hovercraft is significantly reduced.

〔Example〕

An embodiment of the present invention will be explained with reference to the drawings. Fig. 1 is a longitudinal sectional view thereof, Fig. 2 is a transverse sectional view taken along the line ■-■ in Fig. 1, and Fig. 3 is a cross-sectional view taken along the line FIG.

In the above figure, the same reference numbers as in Figs. 4 to 6 indicate the same parts as in the same figure, and the fan 1 is installed at the rear of the hull 3 to reduce air resistance and increase buoyancy, as shown in Fig. 3. As shown in FIG.
A floating air intake 5 is provided in an annular shape that opens in steps toward the upstream on the inner surface of the floating air guide duct, and the hollow part of the flow guide duct communicates with the floating air flow path 7.

In such a structure, the air intake port 5 is controlled by the fan 1.
The air that has flown into the hollow interior of the guide duct 4 flows along the circumferential direction inside the guide duct, descends into the interior of the hull, passes through the floating air channel 7, and is distributed around the outer periphery of the hull. The air flows into the air cushion chamber through the provided jet port 8 and acts as buoyancy.

Here, the blade tips 9 of the guide duct 4 are formed to extend rearward and cover the outer peripheral edge portion immediately downstream of the fan, and a floating air intake port is provided on the inner peripheral surface of the introduction duct to the fan in the air flow direction. It is preferable to provide it close to and overlapping the tip of the rotor blade.

The airflow discharged from the center of the fan is directly discharged to the rear of the ship and becomes a propulsive force.

The levitation air intake 5 may be formed into a slit shape and arranged in an annular shape on the inner peripheral surface of the flow guide duct in order to resist impact, etc., and the levitation air flow path 7 may be particularly restricted. It is preferable to install it on both sides of the hull.

〔Effect of the invention〕

According to this structure, the air for floating can be uniformly taken in from downstream of the fan using the flow guide duct, so there is no difference in back pressure in the circumferential direction of the fan, especially in the upper and lower parts, so that the inflow in the circumferential direction of the fan is reduced. Since the flow rate becomes more uniform, the noise level of the hovercraft is significantly reduced.

In short, according to the present invention, in a hovercraft having an annular guide duct that coaxially surrounds a fan that simultaneously discharges propulsion air and levitation air, the guide duct is formed so that the inside of its airfoil cross section is hollow. At the same time, an annular floating air inlet is provided on the inner surface of the flow guiding duct and opens stepwise toward the upstream on the downstream side of the fan, and the air taken in from the floating air inlet is introduced into the air cushion chamber. By introducing this, we can obtain a small hovercraft that reduces the noise of the propulsion levitation fan.
The present invention is extremely useful industrially.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal cross-sectional view showing an embodiment of the present invention, FIG. 2 is a cross-sectional view taken along line nn in FIG. 1, and FIG. 3 is a cross-sectional view taken along line nn in FIG.
FIG. Figure 4 is a side sectional view showing a conventional small hovercraft.
! 5 is a cross-sectional view taken along line V-V in FIG. 4, and FIG. 6 is a partial vertical cross-sectional view taken along line vr-VI in FIG. 1... Propulsion and levitation fan (fan) 2... Engine, 3... Hull, 4... Guide duct, 5... Air intake for levitation, 7... Air channel for levitation , 8... Ejection port, 9... Wing tip, Agent: Masafumi Tsukamoto, patent attorney

Claims (1)

[Claims] In a hovercraft having an annular guide duct that coaxially surrounds a fan that simultaneously discharges propulsion air and levitation air, the guide duct is formed so that the inside of its airfoil cross section is hollow, and the guide duct is An annular floating air inlet is provided on the inner surface and opens stepwise toward the upstream on the downstream side of the fan, and the air taken in from the floating air inlet is introduced into the air cushion chamber. A small hovercraft with special features.