NO346615B1

NO346615B1 - A snowmaking nozzle

Info

Publication number: NO346615B1
Application number: NO20201094A
Authority: NO
Inventors: Odd Ivar Lindløv
Original assignee: Lindloev Odd Ivar
Priority date: 2020-10-09
Filing date: 2020-10-09
Publication date: 2022-10-31
Also published as: WO2022075855A1; NO20201094A1

Description

A SNOWMAKING NOZZLE

The present invention relates to a snowmaking nozzle for atomizing water and ensure nucleation by means of compressed air.

BACKGROUND

Artificial snow, better known as man-made snow, is a necessity for ski resorts in geographic areas where either snowfall is rare, or temperature is too high or a combination of both. Typically, during cold periods there is little to none natural snowfall, thus these cold periods are used to generate man-made snow to ensure a proper season for the ski resort. Large resorts typically use man-made snow to have a guaranteed opening and closing date for the season. These large ski resorts also have the financial power to invest in large and sophisticated snowmaking systems, where snow production is adjusted automatically to the ambient conditions. However, smaller resorts and club driven resorts, both for alpine and cross-country skiing, or both, typically have a small number of snow canons and limited financial power to invest in more tailored and efficient systems. They typically use lance guns (or stick) in combination with a few fan guns. These systems are energy intense and offers limited possibilities for snow making in marginal conditions, and if so, the wet contents in the snow will be high.

The present invention describes a novel nozzle concept, integrated with a secondary external air cooling device, that will increase snow production in marginal conditions as well as simplifying the method for on-the-fly snow production capacity.

Current snowmaking technology mainly consists of two different snow gun types, namely the stick/pole/lance type, ref. fig.1, and the fan gun type, ref. fig.2.

The main difference between the two technologies lies in capacity and how the snow coverage is required; the lance type is more sensitive to wind direction and has a smaller operating envelope in regard to temperatures and water/air pressures, as compared to the fan gun type, which has a larger operating envelope, but at a significant higher cost. The height of the lance is compensated by the fan in the fan type, giving a longer throwing distance and thus a longer ‘hang time’.

The method for making snow is more or less identical for the two types; a simple nozzle for the water, -mainly a fan spray nozzle - and a separate nucleation nozzle, supplying compressed air to the liquid stream exiting the fan nozzle, ref. fig.3. In regard to the conventional fan spray nozzle, several different concepts are used to produce a flat or fanshaped sprays. The most common type of nozzle is one in which the orifice is formed by the intersection of a V-groove with a hemispheric cavity communicating with a cylindrical liquid inlet. It produces a liquid sheet parallel to the major axis of the orifice, which disintegrates into a narrow elliptical spray, ref. fig 3.

The benefit with a fan spray nozzle is that it may provide good atomization, but this is dependent on a high water supply pressure. Atomization grade will naturally vary with pressure; the higher pressure and output, the better atomization grade and vice versa. As the atomization grade, i.e. a monodisperse spray with small droplets, does vary with pressure for the fan spray nozzle, it can be such that the optimum condition is to have a monodisperse spray with medium sized droplets, and the fan spray nozzle will often struggle to meet such predefined condition, as the droplet size will vary with varying pressure.

There are variances of technology used, but most conventional solutions falls into one of these two categories. The cost of a fan type snow gun is far higher than a lance, so for smaller resorts they either use a number of lances (which are more or less permanently arranged on locations) or one or two fan guns (which usually have to be moved around from one location to another).

A further drawback with both the lance and fan gun types, is that the nozzle have fixed orifices. When conditions are marginal, a smaller orifice nozzle is required for optimal results. When the temperature drops and the conditions are better, a larger orifice nozzle can be installed to increase snow production (or more orifice nozzles of the same smaller size can be added). For a lance type, swapping orifice nozzles is a manual job. For the fan type, this is usually done remotely by adjusting the number of on/offline nozzles automatically. In any case, this does not change the very fundamental concept on how the nozzle atomizes the water.

US3923247 relates to a snowmaking gun having an outer water conduit, an inner air conduit and a convergent-divergent portion of the nozzle connected thereto, and wherein the divergent portion of the nozzle includes a circular restrictor. According to US 3,923,247, water undergoes pre-atomization at the point of intersection of the convergent and divergent portions of the nozzle. The intention seems to be that the water will be forced as a sheet towards the wall, while the compressed air will assist in sheet break-up at the smallest cross sectional area. The mixture will then be accelerated via a central cone and finally broken up when exiting the nozzle. Being an internal mixing nozzle, water/compressed air flows will be dependent on each other; Gas-To-Liquid Ratio (GLR) will vary and are deemed to effect atomization performance. Further, the use of compressed air as a source for nuclei formation is not possible as the Joule Thomson effect (“the J/T effect”) will not be present. Spray angle will be narrow.

US4730774 also describes a nozzle with an internal mixing nozzle. A spring disc arrangement is used to adjust slit size during varying water/compressed air supply pressure; the more pressure, the larger slit and vice versa. This calls for a varying GLR. However, the liquid sheet break-up will happen internally, and the air expansion will accelerate the mixture and make the sheet/droplets exit the nozzle in a non-monodisperse and thus chaotic manner, which is not desirable. Being an internal mixing nozzle, water/compressed air flows will be dependent on each other; Gas-To-Liquid Ratio (GLR) will vary and effect atomization performance. Again, the use of compressed air as a source for nuclei formation is not possible as the J/T effect will not be present.

FR2783310A1 describes a snowmaking nozzle comprising a coaxial inner air discharge conduit and an annular coaxial outer water discharge slit. US5890652A1 describes a thermally self-regulating snowmaking nozzle comprising an outer housing.

WO2019223848A, wherein the applicant and inventor of the present application is listed as one of the inventors, describes a burner nozzle with similar construction as the present invention. However, WO2019223848A is considered another, non-related technical field.

There is a need for an improved snowmaking nozzle to reduce or eliminate the above mentioned disadvantages of known techniques. It is an objective of the present invention to achieve this and to provide further advantages over the state of the art.

SUMMARY

It is an object of the present invention to mitigate, alleviate or eliminate one or more of the above-identified deficiencies and disadvantages in the prior art and solve at least the above mentioned problem.

The present invention will become apparent from the detailed description given below. The detailed description and specific examples disclose preferred embodiments of the invention by way of illustration only. Those skilled in the art understand from guidance in the detailed description that changes and modifications may be made within the scope of the invention.

Hence, it is to be understood that the herein disclosed invention is not limited to the particular component parts of the device described or steps of the methods described since such device and method may vary. It is also to be understood that the terminology used herein is for purpose of describing particular embodiments only, and is not intended to be limiting. It should be noted that, as used in the specification and the appended claim, the articles "a", "an" and "the" are intended to mean that there are one or more of the elements unless the context explicitly dictates otherwise. Thus, for example, reference to "a unit" or "the unit" may include several devices, and the like. Furthermore, the words "comprising", "including", "containing" and similar wordings does not exclude other elements or steps.

BRIEF DESCRIPTION OF THE DRAWINGS

The above objects, as well as additional objects, features and advantages of the present invention, will be more fully appreciated by reference to the following illustrative and nonlimiting detailed description of example embodiments of the present invention, when taken in conjunction with the accompanying figures.

Fig.1 shows a side view of a prior art lance type snowmaking gun,

Fig.2 shows a perspective view of a prior art fan type snowmaking gun,

Fig.3 shows how a conventional nozzle produces a fan shaped liquid water sheet which poorly matches the nucleator air spray which is ejected towards the flat sheet centre,

Fig.4 shows a perspective view of an embodiment of the present invention,

Fig.5 shows a longitudinal cross section of the embodiment of the present invention shown in fig.4 with arrows indicating the paths of travel for water and air through the nozzle,

Fig.6 and 7 shows two alternative perspective views of the embodiment of the present invention shown in fig.5,

Fig.8 shows an example of a possible retrofit configuration of an embodiment of the present invention on a conventional lance type snowmaking gun with an air cooling jacket,

Fig.9 shows an example of a circular liquid sheet and central air pillow formed by an embodiment of the present invention.

DETAILED DESCRIPTION

The present invention will now be described with reference to the accompanying drawings, in which preferred example embodiments of the invention are shown. The invention may, however, be embodied in other forms and should not be construed as limited to the herein disclosed embodiments. The disclosed embodiments are provided to fully convey the scope of the invention to the skilled person.

Fig.4-7 shows an embodiment of a snowmaking nozzle 14 according to the present invention comprising an inner and outer nozzle parts 1 and 2 which fit together in a tongue and groove 9 configuration. When assembled, the inner and outer nozzle parts 1 and 2 provide an circular water nozzle slit opening 3 which communicates with a water channel inlet 7. The nozzle 14 functionally has a longitudinal center axis and a rotationally mainly symmetric configuration. The nozzle 14 further comprises a coaxial inner air inlet channel 8 which opens into an air discharge opening 4 with a minimum area section. The annular coaxial outer water discharge slit opening 3 has a radius and a thickness which is determined by the nozzle inner part 1 outer diameter and the nozzle outer part 2 inner diameter. The nozzle 14 further comprising an air deflector and nuclei generator 5 shown with the shape of a cone arranged downstream of the coaxial inner air discharge opening 4. The air deflector and nuclei generator 5 has a shape and configuration which deflects the discharged air 16 outwards and thus intersects the annular water sheet 15 produced by the circular water nozzle slit opening 3, i.e. the extension of the air deflector and nuclei generator 5 surface plane is arranged to cross the radius of the annular water sheet 15 produced by the circular water nozzle slit opening 3.

The snowmaking nozzle 14 according to the present invention generates a uniform liquid sheet, ejected from the nozzle slit opening 3. The nozzle according to the present invention, provides a uniform water sheet 15, -uninterrupted by any internal mechanical and/or air mixing atomization- which is easier to atomize or break –up than conventional liquid jet. When the uniform, annular liquid sheet 15 exits the nozzle from the slit opening 3, the sheet thickness will be directly related to the distance between the inner and outer part 1 and 2. As an example only, if the inner diameter is 30 mm and the outer diameter is 30,2mm, the resulting sheet thickness produced by the nozzle will be (30,2/2-30/2) 0,1mm or 100 microns. This sheet will need to be further broken up, and this occurs when the water sheet hits and then gets re-directed outwards by air.

This outward directional change is created when the air 16 exiting the air discharge opening 4 is allowed to expand; an expansion which is assisted by the air deflector and nuclei generator 5. The liquid water sheet 15 will expand outwards from its axis and this will break up the sheet and create individual water droplets, the size of which are mainly dictated by said liquid water sheet thickness, and thus by the nozzle slit opening 3. The air and water path through and out of the nozzle is indicated in fig 5. Inside the cone, a low pressure zone will be created due to the Coanda effect, and this effect will ensure that the water sheet is stabilized. The air deflector and nuclei generator 5, here shown as a cone, will also ensure that ice nucleation occurs due to the J/T effect of the air, i.e. rapid cooling following the air expansion. The rapidly expanding high pressure air will provide a “cushion” shaped by the air deflector and nuclei generator 5, here shown as a cone, and thus set the spray angle.

Although the air deflector and nuclei generator 5 is shown in the form of a cone, other shapes and configurations are also possible, e.g. spherical, half-spherical, spinning-top shape, a surface that is concave or convex etc., as well as a surface with a pattern that may effect the quality of produced snow, e.g. a multi-faceted surface (diamond shape); helical, herringbone, bevel type facets and/or grooves. As an example, a multi-faceted surface may reduce the negative pressure below a cone shaped air deflector and nuclei generator 5, and increase the material thickness, which may help prevent cracking.

In the shown embodiment, the air flowing into the air channel 8 is directed via a convergent throat part before it exits out of the air discharge opening 4. In the shown embodiment, the convergent throat part chokes the airflow and allows for a rapid expansion after the divergent part of the air discharge opening 4. This divergent part might be removed, so that the expansion is allowed to develop closer to the air channel outlet. As the chocked airflow is allowed to expand, pressure will drop rapidly, and an instant cooling of the air will follow. This rapid cooling will reduce the dew point of the air, where the water expelled from the air will form water droplets. These droplets will freeze on the nuclei generator, as this is cooled down from the expanded air. Due to the velocity of the expanded air, these water droplets, when frozen to ice, will tear off the nuclei generator and be mixed with the liquid sheet, now in the break -up process. Other shapes than a convergent throat part which chokes the air can be contemplated.

If the air deflector and nuclei generator 5 is cone shaped or otherwise has a fixed angle, the high velocity over the upper surface of the air deflector and nuclei generator 5 will create a low-pressure zone in the center core area, which will contribute to stabilizing the root of the spray mixture, allowing the mixing zone to be much less affected by cross winds etc. This short and stable mixing zone allows for a high installation freedom of the nozzle; it can be located closer to ground to limit loss of snow production due to wind as the short, stable and effective mixing zone will allow for such.

When the liquid exits the nozzle slit 3, forms a uniform sheet 15 with a given thickness and meets the expanding air 16, the mass average velocity will be rather low. This is because even if the air has a high velocity, the exiting water has a low velocity; from a mass point of view, the mass of the water will be far higher, thus keeping the mass average velocity low. This again gives a quicker reduction in mass speed, further due the angle given by the nuclei generator, this will increase spray surface area and thus reduce the speed. Since the water channel upstream the slit has a higher volume, velocity and pressure drop is kept low.

In the shown embodiment, the inner and outer part 1, 2 is fitted together using a tongue and groove arrangement 9; this also ensures that there are no leakages between air/liquid channels 7, 8. The nozzle is fitted onto a double pipe arrangement, where air goes in center and liquid on the outside. The nozzle itself is fitted using a cap screw. It is understood that this may be done otherwise, i.e. in a one-piece configuration, or with three or more parts.

If the narrow slit has a tendency to freeze during standstill, it is possible to have a small heater arrangement in order to melt any ice blocking the slit.

A possible and potentially feasible method for producing a nozzle 14 according to the present invention is by 3D printing of metallic materials (so called AM, Additive Manufacturing). This is still somewhat of a novel fabrication and expensive technology, but this will change.

Having a circular sheet 15 formed spray with a given thickness exiting the nozzle slit 3, -and also the mixture -the benefit of such a circular sheet formed spray can be utilized and enhanced by creating a low pressure zone which can promote suction if enclosed inside a jacket 12, such as a de Laval like venture nozzle, ref. fig 8. As long as there is a wide and circular spray, a certain amount of air is needed to balance the flow; if the spray is located close to a void space upstream, the spray will collapse due to the low pressure zone. It is possible to overcome this by leaving the spray open, but by arranging a jacket 12 around the nozzle arrangement, the low pressure will create a suction, further increasing the speed of the air sucked into the tube, further lowering the temperature of the air meeting the atomized spray. Fig.8 shows a possible retrofit of the nozzles according to the present invention on a conventional lance type snowmaking gun, where the top nozzle also is shown with a surrounding jacket 12, which, as mentioned, can enhance the efficiency of the snowmaking nozzle 14 even further.

The invention thus introduces several advantageous aspects;

● Sheet formation, where externally atomized by expanding sheet / break -up

● Centre located nuclei generator 5, seeding the droplets with nuclei from the inside out ● As the flows meet externally from the nozzle 14 (i.e. external mixing), any variance in liquid and / or air flow will not affect the performance

● The center located air deflector and nuclei generator 5 is allowed to be cooled down by the expanded air; as the liquid sheet will be deflected by the expanded air, the nuclei generator will not be warmed up by the warmer water liquid sheet; it will remain cooled and shred off ice particles (nucleis).

When designing a snowmaking nozzle 14, the high surface tension of water (on the order of at least 3 times higher compared to other liquids), it has to be ensured that the spray out of the nozzle is monodisperse (equal droplet size) as possible. In order to obtain a mainly monodisperse spray, it is necessary to pay attention to how the spray is ejected from the nozzle; a spray from a conventional nozzle orifice opening will have the form of a jet that will need to be broken up means of a high pressure drop, i.e. a high water feed pressure. The droplet breakup will still be somewhat erratic and chaotic, so within the mix of droplets, some will be small, some will be large. The larger ones will not necessarily become snow crystals, they may just fall to the ground as untransformed water droplets and form compact ice. In the nozzle according to the present invention this is addressed by ejecting the water from the nozzle as a sheet; a sheet is easier to break up compared to a jet. The fundamental principle of the disintegration of a liquid consists of increasing its surface area; if the water is ejected in the form of a cylindrical rod or sheet, it will easily becomes unstable and disintegrate into drops). The droplet size will be more or less dictated by the sheet size; a sheet size on 200 microns will give a quite uniform droplet size in the vicinity 200 microns. Further, this sheet is generated by a slit which is independent of the supply pressure; the sheet will be 200 microns regardless if the water supply pressure is 1 barg or 30 barg - only the capacity will change. By using a pump with a variable speed drive (VSD), e.g. a centrifugal pump, snow production capacity can easily be adjusted to the ambient conditions. At marginal conditions, capacity will be lower, lower pump speed and thus pressure and power consumption. When temperature drops, capacity will be higher by increasing pump speed. If a water reservoir is kept at high altitude and if the snow gun is located at a lower altitude, only the elevation different might be sufficient to generate pressure for snowmaking; this will further reduce power consumption.

As mentioned above, the nozzle 14 according to the present invention produces a circular spray pattern 15 with a surface area that can be far greater than a conventional flat nozzle (ref. figs 3 and 9 for comparison); this gives a higher water/air ratio and will increase cooling of the water and increase snow production at similar capacity compared to a snow gun using a fan nozzle. In order to utilize the increased surface area fully, the nucleation process also needs to be controlled. Nucleation involves forming a core of a snow crystal, and according to the present invention, this process is controlled and enhanced by means of the air deflector and nuclei generator 5. The compressed air that is ejected via a core venture air channel 4 can ensure flow through the throat with a velocity >1 Mach. The evaporative moisture in the air from the core venturi air channel 4 will be spontaneously dried and form miniscule water droplets; these will freeze upon hitting the air deflector and nuclei generator 5 and form miniscule ice crystals that will be teared off and ejected into the water spray from the nozzle slit opening 3, thereby starting nucleation. The air pressure needs to be > 2 barg, but typically not much higher than 4 barg, as this air pressure interval will be sufficient for water freeze-out. A higher pressure will just give more water, and this is not needed. This air will deflect over the air deflector and nuclei generator 5, here shown as a cone, cool it down and then generate ice for nucleation. The air deflector and nuclei generator 5 will also dictate a spray angle for the mixture.

Further enhancement of the invention is achieved by adding a surrounding jacket 12 around the spray nozzle itself, ref. fig 8, e.g. in the form of a de Laval or venturi -like nozzle. The purpose is to increase the air velocity around the water droplets, thus further assisting in a rapid cool down and hence snow formation. The entrained air formed by the spray, where the spray forms a low pressure zone in close proximity (e.g. Coanda effect), similar to the concept used in air amplifiers, will increase the air velocity and at the same time decrease the air temperature; this will be a fan-free arrangement only using the inherent suction generated by the spray itself.

According to the present invention, the snowmaking nozzle 14 comprises a longitudinal center axis A and a rotationally mainly symmetric configuration, with a coaxial inner air discharge conduit 4 and an annular coaxial outer water discharge slit 3. The annular coaxial outer water discharge slit 3 having a radius and a thickness, the nozzle further comprising an air deflector and nuclei generator 5 downstream of the coaxial inner air discharge conduit 4.

In one possible embodiment of the present invention, two cooling effects are used to enable snowmaking at marginal temperatures: the cold sink effect via the cone shaped air deflector and nuclei generator 5, and additional cooling obtained by the surrounding jacket 12 around the spray nozzle itself, which, as mentioned, can be in the form of a de Laval venture like nozzle. This embodiment is suitable for retrofit and upgrade of conventional lance systems, where a small modification will enable the lance system to obtain all the benefits of a fan system and more, but without the accompanying cost.

In addition, the nozzle 14 according to the present invention can also be integrated into a fan system, which out increase efficiency and enable easier control of the system.

In one possible embodiment of the present invention, the water discharge slit 3 has a radius of 20 to 100 mm.

In one possible embodiment of the present invention, the water discharge slit 3 has a thickness of 40 – 400 microns.

In one possible embodiment of the present invention, the air deflector and nuclei generator 5 is mainly rotationally symmetric around the longitudinal center axis A.

In one possible embodiment of the present invention, the air deflector and nuclei generator 5 has the shape of a cone, where cone has an angle of 60 to 130°, preferably 80 -120°.

In one possible embodiment of the present invention, if the air deflector and nuclei generator 5 has the shape of a cone or other configuration with a mainly circular perimeter, the outer perimeter has a radius less or equal to the radius of the water discharge slit 3.

Summarizing some of the possible benefits of the present invention:

Combined water / nucleation ejected from a single nozzle – external mixing, avoiding possible reverse flow of water (high pressure) into a lower pressure (air) stream,

Monodisperse droplets produced over the complete range (i.e. turn-down),

Capacity is controlled by pump speed, thus no need for separate control valves at the snow gun,

Due to the high air velocity, in the core of the spray, this will be virtually unaffected by changing wind direction,

End point of nozzle (vertical throw height) is less critical due to the super-cooled air cooling down the water, thus reducing the need for hanging time,

Simple retrofit onto existing lance types (replacing head),

Due to simple construction, more lances can be used to ensure improved coverage (capacity will be controlled by the supply pump),

Nozzle outer part can be changed all depending drier/wetter snow requirements exceeding the pure turn-down provided

Can be used both for a lance and fan type snow gun – the only difference will be throwing length (one can make a generic snow gun and just add a fan to achieve the fan system benefit),

Since the spray is ejected in a cone shaped pattern, the total surface area of the spray will be, compared to a fan nozzle, with same spray angle and at same length, on the order of > x3 at same capacity,

Installing an outer jacket will further lower the air temperature with approx.2 degrees Celcius, thereby increasing snowmaking during marginal conditions.

Claims

1. A snowmaking nozzle (14) for atomizing water and ensuring nucleation by means of compressed air, the nozzle functionally having a longitudinal center axis (A) and a rotationally mainly symmetric configuration, the nozzle comprising a coaxial inner air discharge conduit (4) and an annular coaxial outer water discharge slit (3), c h a r c t e r i z e d i n that the annular coaxial outer water discharge slit (3) having a radius and a thickness, the nozzle further comprising an air deflector and nuclei generator (5) downstream of the coaxial inner air discharge conduit (4).

2. A snowmaking nozzle (14) according to claim 1, where the water discharge slit (3) has a radius of 20 to 100 mm.

3. A snowmaking nozzle (14) according to claim 1, where the water discharge slit (3) has a thickness of 40 – 400 microns.

4. A snowmaking nozzle (14) according to claim 1, where the air deflector and nuclei generator (5) is mainly rotationally symmetric around the longitudinal center axis (A).

5. A snowmaking nozzle (14) according to any of the previous claims, where the air deflector and nuclei generator (5) has the shape of a cone, where cone has an angle of 60 to 130°, preferably 80 -120°.

6. A snowmaking nozzle (14) according to claim 5, where the air deflector and nuclei generator (5) with the shape of a cone, has an outer perimeter with a radius less or equal to the radius of the water discharge slit (3).

7. A snowmaking nozzle (14) according to claim 1, where the air deflector and nuclei generator (5) has the shape of a sphere, half-sphere, spinning-top, a concave surface, a convex surface, a multi-faceted surface, a helical patterned surface, a herringbone patterned surface and/or surface with bevel type facets and/or grooves.

8. A snowmaking nozzle (14) according to any of the previous claims, comprising a surrounding jacket (12).

9. A snowmaking nozzle (14) according to claim 8, where the surrounding jacket (12) has the form of a de Laval nozzle.

10. A snowmaking nozzle (14) according to claim 1, comprising a heater element.

11. Method for producing a snowmaking nozzle (14) according any of the previous claims, by 3D printing of metallic material.