EP0683886A1

EP0683886A1 - Improved snow gun.

Info

Publication number: EP0683886A1
Application number: EP94906949A
Authority: EP
Inventors: Pierre Girardin
Original assignee: YORK FRANCE AIRCHAL
Current assignee: YORK FRANCE AIRCHAL
Priority date: 1993-02-19
Filing date: 1994-02-15
Publication date: 1995-11-29
Anticipated expiration: 2014-02-15
Also published as: ATE155875T1; FR2701759A1; FR2701759B1; JPH08509800A; NO953196L; EP0683886B1; CA2156422A1; NO953196D0; DE69404446D1; WO1994019655A1

Abstract

A snow gun including a hollow moulded body provided with a pressurized water inlet channel (2) leading to a mixing chamber (16) which ends in an outlet nozzle (17), and a compressed air inlet channel (3) leading to an injector (14) arranged at the inlet of said mixing chamber in the middle of the water inlet. Said gun comprises a ring-shaped nozzle (18) for supplying secondary compressed air, surrounding the primary air/water mixture. The nozzle (18) and the injector (14) have a common compressed air supply. In said device, expansion of the secondary air at the outlet of the nozzle accelerates the formation of seeding crystals whereby the formation of snow is faster and more thorough in the main water jet.

Description

IMPROVEMENT WITH SNOW CANNONS.

The present invention relates to an improvement to snow guns of the high pressure type, that is to say to snow cannons as described in particular in document EP-A-18280.

The present invention provides a gun which significantly increases the capacity for producing snow. Under identical temperature conditions, the barrel according to the invention will deliver a greater quantity of water which, by means of particular means, will make it possible to obtain abundant and high quality snow.

The means used by the invention in fact make it possible to promote the rapid formation of ice or snow crystals which will very quickly inoculate all of the drops projected by the gun. This transformation into snow is all the more rapid as means allow the formation of a jet of water and air mixture in which the water particles have a very fine size which favors the transformation into ice or snow. .

The invention also has the advantage of significantly reducing the noise caused by the main jet consisting of the mixture of water and primary air.

The snow cannon according to the invention comprises - a pressure water inlet pipe, - a pressurized air supply pipe, - and a chamber for mixing water and pressurized air at the end of which is an ejection nozzle; said barrel further comprising, around said ejection nozzle, an annular nozzle for ejecting secondary air under pressure and enveloping the main jet consisting of the mixture of water and primary air.

Still according to the invention, the nozzle comprises, from upstream to downstream, a convergent, a narrow sonic neck, which limits the flow, where the secondary air reaches the speed of sound, then a divergent at very low opening so as to achieve relaxation of the compressed air making it possible to reach temperatures in the region of - 70 ° C.

At the outlet of this nozzle, the very cold secondary air envelops the main jet. The water particles which emanate from this main jet are immediately in contact with this very cold air; this contact promotes the formation of crystals which serve to seed all of the particles of this main jet.

Still according to the invention, the mixing chamber is in the form of an elongated cylindrical tube comprising, at its end, located upstream of the ejection nozzle, a cavity formed by a sudden flaring followed by a convergent then by a cylindrical portion. The diameter of the internal cylindrical portion is slightly less than that of the mixing chamber upstream of said flaring. The slope of the convergent is around 10 °.

Still according to the invention, the ejection nozzle has an internal divergence and a cylindrical internal end whose cylindrical external envelope constitutes the internal wall of the nozzle.

There is thus between the primary jet constituted by the mixture of water and primary air and the flow of secondary air, a space favoring a sort of fripping of the circumference of the central jet and one observes an atomization of the particles of water and the formation of seed crystals. This frizzing is also caused by the difference in the speeds of the main central jet and the secondary air flow. The space between the two jets, that is to say the thickness of the end of the ejection nozzle, is between one and five millimeters.

According to another preferred arrangement of the invention, the barrel consists of a molded hollow body comprising: - a tube followed by a cavity for the arrival of water and - another tube followed by another cavity for the air intake, - chambers connected to said cavities and delimited by radial partitions, the chamber corresponding to the passage of water being disposed between the two other chambers reserved for primary air and secondary air respectively , and - a sleeve for the secondary air which extends from the chamber of said secondary air to the end of the barrel where the nozzle is located.

Still according to the invention, the barrel body has a central bore to accommodate a kind of cartridge made up of three distinct parts arranged on the axis of said bore: - a primary air injector, - the mixing chamber, the end of which downstream constitutes the ejection nozzle, provided with means of connection with the sleeve and - the nozzle associated with fixing means relative to the end of said sleeve.

The invention will be further detailed with the aid of the following description of an embodiment and the appended drawings, given for information only, and in which:

- Figure 1 is a longitudinal sectional view of the barrel according to the invention;

- Figure 2 is a partial section of the end of the barrel showing the secondary air ejection nozzle;

- Figure 3 illustrates all of the elements inserted into the barrel body, forming a kind of cartridge;

- Figure 4 shows an alternative embodiment.

The snow cannon consists of a hollow body 1 obtained by molding. This body comprises a pipe 2 for the inlet of pressurized water and a pipe 3 for the inlet of pressurized air. The tubing 2 is extended in the body 1 by a cavity 2 'which serves a chamber 4 of annular shape centered on the longitudinal axis 5 of the barrel.

The tubing 3 is extended, in the same way, by a cavity 3 'which serves a first chamber 7 located upstream in the body 1, that is to say before the chamber 4, and a second chamber 8 located downstream; in fact rooms 7 and 8 are located on either side of the room

4, and they also have an annular shape also centered on the axis 5.

Beyond the chamber 8, the body 1 is extended by a sheath 9, which sheath constitutes the outer envelope of a tubular chamber 10 whose role will be explained below. Note that the chamber 4 is delimited by radial partitions 47 and 48 common with the chambers 7 and 8 respectively.

The chamber 7 is delimited by the partition 47 common with the chamber 4 and by the radial wall 71 which constitutes the bottom of the body 1 between the pipes 2 and 3.

The chamber 8 is delimited by the partition 48 common with the chamber 4 and the radial wall 81 of the body 1 from which the sheath 9 extends.

The partitions 47, 48 and the walls 71 and 81 are all arranged radially, that is to say perpendicular to the main axis 5.

The body 1 contains a kind of cartridge 11 detailed in FIG. 3. This cartridge 11, centered on the axis

5, threads into the body 1 and in particular into the sleeve 9, -and into the bores 12 and 13 arranged respectively at the partitions 47 and 48. This cartridge 11 is supported on the internal face of the wall 71 of the body 1 for the embodiment shown in FIG. 1.

This cartridge 11 consists of the following three elements: - an injector 14 for compressed air, - a main tube

15, the central part of which constitutes the mixing chamber

16 and whose downstream end constitutes the ejection nozzle 17, - a nozzle 18 which may include, as shown according to the embodiment of Figures 1 and 2, in a single piece, a flange 19 for fixing all of the elements constituting the cartridge 11 on the end 20 of the sleeve

9. c The main tube 15 is centered in the body 1 and in particular in the partitions 47, 48 and the sleeve

9. The tube 15 comprises a cylinder 21 provided with a groove

22 to receive an annular seal 222.

This cylind-rage 21 is adjusted in the bore 13 of the _j 0 partition 48.

Note, on the downstream end of the main tube 15, radial fins 23 in sufficient number to center said tube in the internal bore of the sleeve 9. The space between two fins 23 forms a channel for

25 the passage of secondary air. The total passage section at the level of these channels is chosen so as to be compatible with the flow rate of the nozzle 18.

Upstream of the rolling 21 of the tube 15, there is, in a single piece, a cylindrical ring 24 pierced

20 orifices which allow the passage of pressurized water from chamber 4.

The tube 15 also includes, upstream of the ring 23, a cylinder 25 provided with a groove 22 'for an annular seal 222'; this cylinder 25 is adjusted

25 in the bore 12 of the partition 47.

This upstream end of the tube 15 has an internal bore 26 which serves to center the injector 14. This injector 14 has for this purpose a cylinder 27 provided with a groove 28 for an annular seal 282, and a

Shoulder 29 in a plane perpendicular to the main axis 5; this shoulder 29 comes into contact with the end face 30 of the tube 15. This gives very precise positioning of the injector 14 relative to the tube 15 and in particular relative to the chamber

35 of mixing 16. This injector 14 comprises, arranged in the chamber

7, upstream of its shoulder 29, a cylinder portion 31 centered on the axis 5, provided with orifices 32 of relatively small section so as to be able to retain the ice crystals c which could be conveyed by the pressurized air .

We also note that the cylindrical portion 31 is centered in the bore 12 of the partition 47, over a small span.

, ₀ The rear face 33 of the injector 14 is supported on the wall 71 of the body 1. The injector 14 is pressed against the wall 71 of the body 1 by means of the tube 15 and in particular of the upstream end face 30 of the tube 15 in contact with the shoulder 29 of the injector. The tube

25 15 is held in position by means of the nozzle 18 and in particular of its face 34 located upstream and which bears on the downstream side "of the fins 23. The tightening of the flange 19 of the nozzle 18, by means of the screws 35, allows the blocking of the cartridge in the body 1 of the barrel.

20 more, the centering of the parts with respect to each other is automatic: the injector 14 is directly centered on the rear end of the mixing chamber 16 and the nozzle 18 is centered in the internal bore of the sleeve 9 likewise that the centering fins 23

25 from the downstream end of the tube 15, that is to say of the ejection nozzle.

The injector 14 comprises, downstream of the chamber 7, a convergent 35 which extends to the inlet of the mixing chamber 16, slightly penetrating the latter over 0 'a distance which corresponds substantially to the radius of the injection port. The external surface of the convergent 35 ensures the guiding of the stream of pressurized water at the inlet of the mixing chamber 16; this entrance to the mixing chamber 16 is arranged in the form of

35 converge 36 with a rounded profile. The mixing chamber is in the form of a tube whose central cavity is cylindrical from the inlet 36 to a frustoconical cavity 37 located upstream of the ejection nozzle 17.

This cavity 37 begins with an abrupt flaring by means of a radial wall 38 in the form of a crown from which there is a convergent 39. The distance which separates this wall 38 from the inlet of the mixing chamber is between 5 and 12 times the internal diameter of this mixing chamber. This convergent 39 has a slope of the order of 10 °. At the end of the convergent 39 there is a neck 40, cylindrical, the diameter of which is slightly less than the internal diameter of the mixing chamber 16, of the order of ten percent in diameter. The length of the neck 40 is of the same order as the length of the diverging portion 41 of the ejection nozzle 17. The speed of the jet at the level of the neck 40 is close to the speed of sound.

The end of the nozzle 17, after the divergent 41, has a cylindrical portion 42 of short length which extends to the end 43 of the tube 15. The end 43 of the tube 15 has a relatively small thickness which appears in more detail in FIG. 3, this thickness corresponds to the space which separates the main jet from the secondary air flow. This thickness can reach 5 mm.

The tube _^ 15 defines with the sleeve 9, the chamber 10 in which the secondary air under pressure circulates, downstream of the chamber 8. The chamber 10 has a tubular shape which extends from the chamber 8 to the nozzle 18, which nozzle has, behind the fins 23, downstream, a convergent whose slope is of the order of 20 ° followed by a relatively narrow neck 45 from which there is a divergent 46 whose slope is order of 4 °. The cylindrical outer wall 50 of the ejection nozzle 17 channels, with the convergent 44, the neck 45 and the divergent 46, the secondary air which circulates in the nozzle. Compressed air circulates at very low speed in chamber 10. On the other hand, it has a very high speed close to or equal to the speed of sound at the level of the neck 45. Beyond the neck 45, the speed of the 'air c increases; the air relaxes. This expansion, in the divergent 46, is accompanied by a temperature drop which can reach - 70 °. This flow of cold air envelops the main jet consisting of the mixture of water and primary air. in The secondary air passage section at the neck 45 of the nozzle is of the order of 20 to 30 percent of the primary air passage section at the ejector 14.

FIG. 4 represents an alternative embodiment 5 relating mainly to the cartridge 11, the injector 14 and to the end of the barrel.

Given the extremely low temperatures at the end of the barrel, we can see the formation of frost. To avoid this frost formation, the end

20 of the cartridge 11 is arranged to better distribute the calories of the mixture of water and primary air under pressure towards the end of the barrel.

The cartridge 11 comprises, at its downstream end, a frustoconical head 51 in which are cut

25 grooves 52, which correspond to the space referred to above, arranged between the fins 23. These grooves 52, in the form of a cutter blade, allow the passage of secondary air to the nozzle 18. This head 51 has a shoulder 53 which takes

30 rests on the end 54 of the sleeve 9. It also comprises, upstream of the shoulder 53, a threaded portion 55, which allows the cartridge 11 to be screwed onto the end of the sleeve 9 and to position it in this sleeve .

35 The nozzle 18 has a skirt 56 which adjusts to the frustoconical head 51 of the cartridge 15 to allow an even more precise positioning of its neck 45, FIG.

3, relative to the outer wall 50 of the ejection nozzle.

This frustoconical skirt 56 has at its upper end a flange 57 which allows, by means of a ring

58, to clamp the nozzle 18 on the head 51 and on the end of the barrel.

The ring 58 is internally threaded and screwed onto the end of the sleeve 9. A better distribution of the calories is thus obtained between the head 51 of the cartridge 11 and the skirt 56 of the nozzle 18 which avoids the formation of frost on the end of the barrel.

In this variant shown in FIG. 4, there is also a simplification in terms of the mounting of the injector 14 which serves to introduce the primary air at the inlet of the mixing chamber 16.

This injector 14 is centered at the downstream end of the cartridge 15 and fixed by a thread 60. We find the same constructive arrangements as those described above in connection with FIGS. 1 to 3 concerning the water and air inlets under pressure and their introduction both at the level of the mixing chamber 16 and at the level of the chamber 10 which serves the nozzle 18.

Claims

- CLAIMS -

1.- Snow gun of the high pressure type, spraying a mixture of air and water and comprising: - a pipe (2) for inlet of pressurized water, - a pipe (3) for inlet of pressurized air, and - a chamber (16) for mixing water and pressurized air, at the downstream end of which is an ejection nozzle (17), characterized in that it comprises , around said ejection nozzle (17), an annular nozzle (18) supplying secondary air under pressure to envelop the main jet consisting of the mixture of water and primary air.

2.- snow cannon according to claim 1, characterized in that the nozzle (18) and the injector (14) comprise a common inlet of pressurized air.

3.- snow cannon according to any one of claims 1 or 2, characterized in that the nozzle (18) comprises, around the outer cylindrical end of the ejection nozzle (17), from upstream to downstream, a converging (44), a narrow neck (45) where the secondary air reaches a sonic speed, then a diverging (46) with a very slight slope, to achieve a relaxation of the compressed air making it possible to reach temperatures of the order of - 70 °.

4.- snow cannon according to any one of claims, 1 to 3, characterized in that it comprises a mixing chamber (16) in the form of an elongated cylindrical tube provided, upstream of the ejection nozzle (17 ), a cavity (37) which comprises an abrupt flaring followed by a convergent (39) then a neck (40) whose internal diameter is slightly less than that of said mixing chamber (16) at said level flare.

5.- snow cannon according to any one of claims 1 to 4, characterized in that the ejection nozzle (17) has an internal divergent (41) and c an internal cylindrical end (42).

6.- snow cannon according to any one of claims 1 to 5, characterized in that it consists of a body (1) hollow, molded, comprising - a tube

(2) and a cavity (2 ') for the water supply and a pipe _c - (3) and a cavity (3') for the air supply, - chambers

(4, 7 and 8) defined by walls and radial partitions (47, 48, 71 and 81) and whose chamber (4) for water is arranged between the two chambers (7 and 8) for air , and _ιn - a sheath (9) which extends from the chamber (8) of the secondary air to the end of the barrel where the nozzle (18) and the ejection nozzle (17) are located.

7.- snow cannon according to claim 6, characterized in that the body (1) has an orifice

, _c central to accommodate, arranged on the same axis (5), several separate parts forming a kind of cartridge (11): - the injector (14) for primary air, - the mixing chamber (16) of cylindrical tube (15) whose downstream end constitutes the ejection nozzle (17) and

- Has centering means and connection with the inner wall of the sleeve (9), - the nozzle (18) centered on the end of the tube (15) at said ejection nozzle.

8.- snow cannon according to claim 7,

25 characterized in that the injector (14) comprises a cylinder (27) and a thread allowing its centering and its screwing at the end of the main tube (15), which tube is centered in a sealed manner in the partitions (47 and 48) separating the air and pressurized water chambers.

3 _Q 9.- snow cannon according to claim 8, characterized in that the upstream end of the nozzle (18) is supported and centered on the head (51) located at the end of the ejection nozzle ( 17), which nozzle (18) is immobilized by means of a ring (58) screwed 5 on the outer end of the sleeve (9). 10.- snow cannon according to claim 4, characterized in that the nozzle (18) is fixed on the end of the sheath (9) by a threaded ring (58) and it is centered on a frustoconical head (51) arranged at the end of the tube (15), which head has grooves (52) for the passage of secondary air.