WO1997039945A1

WO1997039945A1 - An airscrew anti-eddy system

Info

Publication number: WO1997039945A1
Application number: PCT/BG1996/000009
Authority: WO
Inventors: Rumen Dobrev Todorov
Original assignee: Rumen Dobrev Todorov
Priority date: 1996-04-19
Filing date: 1996-07-19
Publication date: 1997-10-30
Also published as: AU6410396A; BG100519A

Abstract

An airscrew anti-eddy system, used in the aircraft industry, especially in helicopters. The problem with the formation of an 'eddy ring' is solved by building a reliable barrier. The system consists of screw-blades (10), attached to an airscrew shaft (1). A pipe (12) for the burnt gases, given by a compressor (7), is layed inside each of the screw-blades (10). The end (15) of the pipe (12) reaches the external end (16) of the screw-blade (10), where is mounted at least one nozzle (17) and at the end of each pipe (26) towards the end (27) of the blade (10), there is a nozzle (28). Gas-fluid barriers (25) and (29) are formed from the flow of gases under pressure, which prevents the formation of cross turbolization and an 'eddy ring' over the blade (10). An advantage of the system is the reliable anti-eddy barrier and the additional anti-icer effect.

Description

AN AIRSCREW ANTI-EDDY SYSTEM

TECHNICAL FIELD

The invention is refrerred to a screw anti-eddy system, used in the aircraft industry in flying vehicles with vertical take-off and landing, for exsample helicopter. BACKGROUND ART

It is known a flying vehicle with vertical take-off, consisting of a multiblade supporting screw with 2 to 8 blades. At the rear part of the flying vehicle, remotely from the supporing screw is installed a small transverse compensating propeller. During rotation of the blades, a zone with comparatively low air pressure is formed over the upper surface of each blade. Peripheral-radially pushed air is eddying from the lower to the upper part of the screw-blades and is strongly turbolizing under certain special conditions of stream-line of the supporting screw. This phenomenon is known under the name of "eddy ring". It occurs when the helicopter is lowering in vertical traectory or when flying with low horizontal speed, under 35 km/h, as well as when there is sharp change in the angle of the screw-blades. The harm from the formed "eddy ring" is that it leads to increase of the air pressure over the blades and decrease of the air pressure below them, which itself leads to change for the worse of the lifting ability of the supporting screw. The regim of the "eddy ring" is dangerous and may lead to sudden increase of the lowering speed and quick loss of hight of the flying vehicle. (1) To prevent from forming of this "eddy ring", is invented suitable construction for the blades of the screw in the exsisting flying vehicle with 5 vertical take-off and landing. A blade (2) is known, which is specially constructed for reaching the effect of an airscrew anti-eddy system. The base and the body of the blade are with common configuration but the blade is widen towards its external end and has special barrier against occuring of the "eddy ring". The barrier consists of two twists - internal 0 and external, outgoing and is dirrected downwards. The blade is narrowed again at the outgoing twist of the barrier. Thus formed and turned downwards vertical peripheral barrier prevents, to a certain degree, the air under the blade to go peripherally out and above it, helps the preservation of the air cushion under the blade and prevents the 5 formation of the "eddy ring".

Disadvantages of the described construction of the anti-eddy blade are: it is impossible the barrier to be formed geometrically exactly at the outgoing end of the blade, so that the air cushion under the blade to be preserved at the nessessaiy degree and anti-eddy effect to be reached; the

_ι.0 widened end of the blade is an additional peripheral mass over it, which is badly influencing the loading of the blade's strength and leads to deflection of the the blade's end downwards. This consructive descent of the peripheral barrier and the additional deflection of the blade, caused by the peripheral mass over it, may lead to undesirable toutch of the

45 blade to the body of the flying vehicle. The vertical barrier of the blade is difficult to be stream-lined in a horizontal flight and causes resistance to the flight. Besides, the blade with this construction could not prevent or remove the ice, formed over it in cold atmosphere. DICLOSURE OF INVENTION The technical problem, which must be solved reffers to the construction of an airscrew anti-eddy system, which itself is able to build a reliable barrier against formation of an "eddy ring", preserving in better way the air cushion under the screw-blades and reaching the best anti- eddy effect. An additional loading of the blades' strength must be avoid, as well as an undesirable touch of the blade to the body of the flying vehicle. In addition, an anti-icer effect must be reached.

This technical problem is solved with the invention of an airscrew anti-eddy system with the following construction. A collector for compressed gases is installed movably and hermetically around the driven screw shaft of the flying vehicle. The shaft is with a central cavity. Via a pipe, the chamber of the collector is connected to a dehvery pipe of a compressor for thickened gases and via radial opening in the shaft it is connected to the central cavity of the shaft. Hollow screw-blades with ability for rotation are set bearingly to special journals on the driven shaft. Each of the journals is with central opening. Inside each of the screw-blades is layed a pipe for gases under pressure. One of the ends of the pipe for gases under pressure is connected with the journal in a way, so that the opening of the journal is joint with the opening of the pipe. The other end of the pipe reaches the external end of the screw-blade, where minimum one nozzle is mounted. The axis of the opening of each of the nozzles comes to the lower surface of the blade at an angle α of 90° to 50°. The compressor owes a suction pipe as well. Towards this pipe, a chamber is installed, in which gases come, including the athmosphere air and burnt gases from the outlet for burnt gases of the main machine for flying of the vehicle. The chamber owes an input, where the athmosphere air enter and an income for burnt gases. Thanks to a distributor one of the inputs is always open or parάally open and parάally closed, and the other one is closed or pardally closed and parcially open. A pipe is installed to the input for the burnt gases, the

80 second end of which is set in the outlet for burnt gases of the engine of the flying vehicle, for exsample a turbine. The barrier against formation of "eddy ring" is gas-fluid and consists of the compressed air and burnt gases flowing through the nozzles.

Additionally, transverse pipes are brought out of the pipe for gases

85 under pressure in the airscrew blade and stretched towards the end of the blade. At the end of each pipe, there is a nozzle, through which compressed gases could flow out and a fluid barrier, against cross turbolization of the air over the blade, could be formed.

The advantages of the offerred airscrew anti-eddy system are the

90 following. The system preserves in better way the air cushion under the screw-blades, reaches the best anti-eddy effect, preventing the formation of the "eddy ring". This effect is a result of the air barrier, which as a fluid formation is flexible and is able for fitting. The undesirable additional loading of the blades' strength and touch of the blade to the body of the

95 flying vehicle are avoided, because the barrier is fluid. In addition, an anti-icer effect of the blades is reached, as a result of the flow of hot air under pressure or even hotter burnt gases, through the screw-blades. BRIEF DESCRIBTION OF FIGURES One sample of an airscrew anti-eddy system, according to the

100 describtion is shown on figure L

Figure 1 shows a common view with a parάal cut of an airscrew anti-eddy system. BEST MODE FOR CARRYING OUT THE INVENTION According to the describtion and the figures, the sample for an airscrew anti-eddy system has the following construction. A collector 2 with a chamber 3 for compressed gases is installed movably and hermetically around the driven screw shaft 1 of the flying vehicle (not shown). The shaft 1 is with a central cavity 4. Via a pipe 5, the chamber 3 of the collector 2 is connected to a delivery output 6 of a compressor 7 for thickened gases and via radial opening 8 in the shaft 1 it is connected to the central cavity 4 of the shaft. Hollow screw-blades 10 with ability for rotation are set bearingly to special journals 9 on the driven shaft 1. Each of the journals 9 is with central opening IL Inside each of the screw-blades 10 is layed a pipe 12 for gases under pressure. One of the ends 13 of the pipe 12 for gases under pressure is connected with the journal 9 in a way, so that the opening 11 of the journal 9 is joint with the opening 14 of the pipe. The other end 15 of the pipe 12 reaches the external end 16 of the screw-blade 10, where five nozzles 17 are mounted. The axis of the opening of each of the nozzles 17 comes to the lower surface 18 of the blade 10 at an angle α of 75°. The compressor 7 owes a suction pipe 19 as well. Towards this pipe 19, a chamber 20 is installed, in which gases come, including the athmosphere air and burnt gases from the outlet for burnt gases of the main machine for flying of the vehicle. The chamber 20 owes an input 21, where the athmosphere air enter and an input 22 for burnt gases. Thanks to a valve distributor 23 one of the inputs 21 or 22 is always open or parcially open and parcially closed, and the other one is closed or parcially closed and parcially open. A pipe 24 is installed to the input 22 for the burnt gases, the second end of which is set in the outlet for burnt gases of the engine of the flying vehicle, which 130 is itself a turbine. The barrier 25 against formation of "eddy ring" is gas- fluid and consists of the compressed air and burnt gases flowing tlirough the nozzles 17.

Additionally, transverse pipes 26 are brought out of the pipe 12 for gases under pressure in the airscrew blade 10 and stretched towards the

135 end 27 of the blade 10. At the end of each pipe 26, there is a nozzle 28, through which compressed gases could flow out and a fluid barrier 29, against cross turbolization of the air over the blade 10, could be formed.

INDUSTRIAL APPUO^BILITY

The airscrew anti-eddy system is used in the following way. The

140 athmosphere air is sucked through the input 21 and via the distributor 23 enters in the compressor 7. After that the compressor 7 blasts it and the air enters, with increased pressure, the chamber 3 and, via openings 8, the central cavity 4, openings 11 in the journals 9 and opening 14 of the pipe 12, comes to the nozzles 17, through which the air flows with high

1 45 speed. When the compressed air is flowing out, it creates a thick air barrier 25, which opposes the peripheral flow-out of the air under the blade 10 during its movement. At the same time, flowing compressed gases, through nozzles 28, form a fluid barrier 29, which prevents the formation of cross turbolization and undesired increase of the air

1 50 pressure over the blade 10. The air barriers 25 and 29, as gas-fluid formations, are able for flexibility and fitting, which leads to optimal prevention from forming of cross turbolization and an "eddy ring".

During the flight under winter conditions, the screw-blades 10 very often become iced. The offerred airscrew anti-eddy system is able to

1 55 warm the screw-blades and to prevent from ice-formation or to melt it.

As a rule, the compressed air comes out of the compressor hot. It warms all the details, through which it passes, including the screw-blades 10. In case, that's not enough, the valve distributor 23 closes completely or parcially te input 21 for the athmosphere air and opens completely or parcially the input 22, through which hot burnt gases from the outlet for burnt gases of the turbine of the engine enter the compressor. This way, the relation between fresh air and burnt gases in the gas mixture, sucked and blasted by the compressor 7, could be changed. In this case, compressed gases with even higher temperature flow out after the compressor 7, which allows more effective heating of the screw-blades 10.

Literature: (1) A. S. Braveπnan, A. P. Vaindrub - "Dinamic of the helicopter" (2) EP 0565 413

Claims

PATENT CLAIMS

1. An airscrew anti-eddy system, constisting of screw-blades, attatched via journals, to a driven airscrew shaft, at the peripheral end of the blades being built a barrier against forming of an "eddy ring", which system could be characterized by a collector (2) with a chamber (3) for compressed gases, mounted movably and hermetically around the driven airscrew shaft of the flying vehicle, which shaft (1) has a central cavity (4), and via a pipe (5) the chamber (3) of the collector (2) being connected to a delivery outlet (6) of the compressor (7) for thicken gases and via radial openings (8) in the shaft ( 1) being connected to its central cavity (4) and to special journals (9) over the driven shaft (1), each of them being with a central opening (11), are set bearingly screw-blades (10), inside of each of them being layed a pipe (12) for gases under pressure, the first end (13) of which is connected to the journal (9), so that the opening (11) in the journal (9) is joint to the opening of the pipe and the other end (15) of the pipe reaches the external end (16)of the screw-blade (10), where is mounted at least one nozzle (17), the axis of the opening of each nozzle coming to the lower surface (18) of the blade (10) at the angle α of 90° to 50° and, owe to the flow of gases under pressure, a gas-fluid barrier (25) is formed, the gases enterring a chamber (20), mounted to the suction pipe (19) of the compressor (7).

2. An airscrew anti-eddy system, according to claims 1 and 2, characterized by the fact, that the chamber (20) consists of an input (21) for athmosphere air, enterring it and an input (22) for burnt gases, enterring it, so that due to a valve distributor the one end (21) or (22) is always open or parcially open and parcially closed, and the other one is closed or parcially closed and parcially open, a pipe (24) being mounted to the input (22) for burnt gases, the second end of which is placed in the outlet for burnt gases of the engine of the flying vehicle.

3. An airscrew anti-eddy system, according to claims 1 and 2, characterized by the fact, that the gases enterring chamber (20) include athmosphere air and burnt gases from the main engine for flying of the vehicle or a mixture of athmosphere air and burnt gases.

4. An airscrew anti-eddy system, according to claims i, characterized by the fact, that the axis of the opening of each nozzle (17) comes to the lower surface (18) of the blade (10) at the angle α of 75°.

5. An airscrew anti-eddy system, according to claim L characterized by the fact, that additionally, transverse pipes (26) are brought out of the pipe (12) for gases under pressure in the airscrew blade (10) and stretched towards the end (27) of the blade (10) and at the end of each pφe (26), there is a nozzle (28), through which compressed gases could flow out and a fluid barrier (29), against cross turbolization of the air over the blade (10), could be formed.