CN1761527A - nozzle - Google Patents

Abstract

A nozzle (10) for producing a flat spray pattern, the nozzle comprising: a fluid channel terminating in an end wall having an outlet orifice (20), the fluid channel having at least one deflector (3, 4) which deflects the fluid towards the orifice; and adjustable means (21, 22) for varying the cross section of the orifice. An artificial snowmaking device comprising: at least one nozzle of the above type, the nozzle being tilted upwards when in use so as to eject a plume of water droplets, the nozzle being positioned near an ejector of compressed air, the variation of the cross section of the orifice affecting the characteristics of the plume.

Description

nozzle

technical field

The present invention relates to a nozzle, in particular to a flat nozzle, particularly but not exclusively for use in snowmaking equipment. The invention also relates to a snowmaking device.

Background technique

There are many types, designs and configurations of nozzles which are particularly useful in industrial applications where fluids are sprayed. These nozzles are used in the irrigation, cleaning, spraying and fire suppression industries. Spray systems including such nozzles have a wide variety of industrial applications. Nozzles are also used in snowmaking equipment, and the main use of the nozzle which is the subject of the present invention is in snowmaking equipment.

Flat nozzles that produce a flat spray pattern are known. They dispense liquids in flat or flake jets. Some nozzles use an oval orifice where the axis of the spray pattern is the continuation of the axis of the inlet pipe connection. Other nozzles use deflectors, deflecting surfaces that cause the spray pattern to deviate from the axis of the inlet pipe connection. There are also a variety of different nozzles that provide a flat spray pattern. These different nozzles provide significantly different spray patterns. The adjustability of such nozzles is generally limited to liquid pressure changes.

There are several parameters that contribute to successful snowmaking. The constant fluctuation of these parameters means that efficient snowmaking equipment needs to be continuously adjusted in order to guarantee optimum efficiency. Adjustability and the resulting efficiency are very important to successful snowmaking and often to the economics of a ski resort.

The invention and its variants solve the problems of nozzle design producing flat spray patterns and of snowmaking equipment.

Contents of the invention

According to one aspect of the present invention there is provided a nozzle for producing a flat spray pattern comprising: a fluid channel terminating in an end wall having an outlet orifice, the fluid channel having at least one deflection deflecting the fluid towards the nozzle devices; and adjustable means for changing the cross-section of the hole. Preferably, the fluid channel has at least two wall sections which converge towards the aperture. The means for varying the cross-section of the hole may comprise a movable gate moved from opposite sides of the hole in order to close or increase the cross-section of the hole.

Preferably, the end wall is provided with a transverse member extending across the end of the fluid channel, the tube supporting an axially movable pin adapted to move across the bore in order to reduce or increase the cross-section of the bore.

In a preferred embodiment, means are provided for controlling the axial movement of the pin.

In a preferred embodiment, the nozzle comprises a T-shaped piece, the legs of which are tubes defining the fluid passage, and the head of the T-shaped piece is a tube located across the end of the fluid channel, the holes located in the T-shaped and axially aligned with the fluid passage, and a pin terminating in a flat surface is positioned at each end of the head of the T-piece so as to be movable along the T-piece so that the end surface of the pin can traverse the hole Motion to change the section of the hole.

In a preferred embodiment, the fluid channel and the cross member are circular and the diameter of the fluid channel is the same as the diameter of the cross member. It is also preferred that the pins move the same distance in opposite directions when adjusting the section of the hole.

According to another aspect of the present invention there is provided snowmaking apparatus comprising: at least one flat water nozzle which, in use, is inclined upwards so as to eject a plume of water droplets, the nozzle being positioned in a compressed air Near the injector, the nozzle has an outlet hole; and means for varying the cross-section of the hole in order to adjust the characteristics of the plume to the ambient conditions.

Preferably, the compressed air injector is arranged downstream of the nozzle. The compressed air injector preferably includes an array of holes. The width of this injector is equal to the width of the plume at the air injector.

Preferably, four flat nozzles are positioned at intervals in the horizontal plane, the distance between the nozzles being equal to the maximum width of each plume.

According to yet another aspect of the present invention, there is provided snowmaking equipment comprising: a rotatable mast supporting a head comprising at least two spaced apart flat water nozzles, each nozzle having an outlet hole, each nozzle positioned proximate the compressed air injectors; and means for varying the cross-section of the orifices so as to vary the output of the respective nozzles.

Preferably, the head is vertically adjustable while maintaining the angle of inclination of the water and air nozzles. In a preferred embodiment, the plume of water droplets escaping from each nozzle is directed tangentially against the underside of the air injector. Preferably, the air injector has a row of spaced apart plurality of outlet holes, the width of the row being substantially the same as the width of the plume at the air injector.

Preferably, the head comprises four nozzles spaced apart such that the plumes meet at their widest points.

Description of drawings

Below will introduce embodiment of the present invention by example, in the accompanying drawing:

Fig. 1 is the perspective view of artificial snow making equipment;

Figure 2 is a side view of artificial snowmaking equipment at three different vertical positions;

Fig. 3 is the plan view of artificial snow making equipment;

Figure 4 is a side view of the snowmaking apparatus supported on an uneven inclined surface;

Figure 5 is a detailed perspective view of the head of the snowmaking apparatus shown in Figure 1;

Figures 6a, 6b and 6c are cross-sectional views along line 6-6 of Figure 5 showing the water jets and air nozzles in three different relative positions;

Figure 7 is an enlarged cross-sectional view of the head portion surrounded by circle 7 in Figure 5;

Figure 7a is a cross-sectional view of two adjacent nozzles showing the means for adjusting the nozzles;

Figures 8a and 8b are cross-sectional views along line 8-8 of Figure 7 showing the water jet outlet in two positions;

Figure 9 is a sectional view along line x showing the physical correlation of the water injector and the air injector;

10 is a cross-sectional view showing the correlation of a water plume in contact with an air jet;

Figure 11 is an underside perspective view of the air injector;

Fig. 12 is a perspective view of the head portion of the snowmaking equipment used in the second embodiment;

Figure 13 is a plan view of the head;

Figures 14a and 14b are plan views of the head showing the movement of the mechanism for adjusting the flat nozzle;

Figure 15 is an enlarged perspective view of area 15 of Figure 13 showing the adjustment mechanism for the flat nozzle; and

Figure 16 is an enlarged perspective view of area 16 of Figure 13 showing the relationship between the flat water nozzles and the air nozzles.

Detailed ways

The preferred embodiments shown in the drawings relate to snowmaking equipment comprising adjustable flat nozzles. The present invention covers the nozzles themselves, which can be used in a variety of blasting industries, as well as the snowmaking equipment including the nozzles, but it should be understood that the snowmaking equipment has many other features that contribute to improved design and operation.

The nozzle 10 is shown in detail in FIGS. 7 and 8 . Although it is shown in relation to snowmaking equipment, it should be understood that the nozzle can also be used in many fields that have nothing to do with snowmaking at all. This nozzle can be used in any industrial spraying application that requires a variable flat nozzle.

As shown in FIGS. 7 to 10 , the adjustable nozzle 10 includes a T-shaped piece 11 whose legs 12 are cylindrical fluid channels, which are fixed on a rectangular mounting plate 13 . A cylindrical tube 15 is welded transversely to the end of the leg 12, the cylindrical tube 15 having a circular outlet hole 20 positioned coaxially with the axis of the fluid passage. The tube 15 is hollow so as to accommodate a pair of cylindrical pins 21,22. Each pin is cylindrical and terminates in a flat surface 23 at one end. The O-ring 24 is seated in a groove 25 on the exterior of the pin, the groove 25 being spaced from but proximate to the surface 23 . The other end of the pin is provided with an external thread 26 arranged to screw into a threaded sleeve 30 which is then welded on a radial flange 31 connected to a large Hollow sleeve 32. As shown in Figure 10, the circular cross-section of the T-piece head 15 is provided with two converging surfaces 3 and 4 which cause the water flowing towards the hole 20 to converge towards it. The flat ends 23 of the pins 21 , 22 are manipulated to vary the cross-section of the hole 20 . As the pin moves within the tube, the end gradually closes the hole 20, as shown in Figures 8a and 8b.

In another alternative, the tee head (not shown) may be of triangular cross-section, with opposite sides converging towards the aperture. A square tube with a hole in one corner also provides two converging walls.

In another embodiment, the head is a rectangular block having an elongated slot with a hole in the base of the slot. The pins are block shaped to slide in the slots. The adjacent end of the pin is beveled to define a surface that converges with the straight edge of the pin near the hole to define an adjustable slot across the hole.

The nozzles described above provide a flat spray pattern. The exact pattern varies depending on the position of the pins 21 , 22 in the holes 20 .

Movement of the pin guide 32 moves the pins 21 , 22 so as to change the cross-section of the hole 20 . When the pin guide is connected with a suitable servo, the nozzle can have a continuously variable outlet depending on the position of the pin. Ideally, each pin moves the same amount in opposite directions.

The advantage of the nozzle is that its outlet can be varied while maintaining full input fluid pressure. This is in contrast to most flat nozzles where the adjustability is adjusted by changing the input fluid pressure, or by changing the nozzle orifice by changing the nozzle tip.

Although in the preferred embodiment the outlet aperture 20 of the nozzle is circular, it will be appreciated that other shapes are also contemplated. A larger diameter hole will provide a smaller spray angle, while a smaller hole diameter will increase the spray angle. On the other hand, wider slots provide a very wide spray angle. By increasing the width of the hole 20 by moving the pins 21, 22 away from each other, fluid flow can be increased. Conversely, by bringing the pins 21, 22 closer together, the fluid flow can be reduced. Preferably, the pressure is always kept constant, ie at its maximum value. Use at maximum pressure results in higher velocities and smaller spray particle sizes. Pins closer together will result in smaller jet particles and smaller fluid flow, which is ideal for snowmaking.

Although the variable flat nozzle 10 described above is specifically designed for use in snowmaking equipment, it should be understood that the nozzle may also be used in a variety of other industrial applications. Adjustment of the nozzle can be done manually by using a wrench, Allen key or similar tool to move the pin, or by a more automated means by actuating the pin guide, as shown in FIG. 7 .

1 to 11 show a snowmaking installation S using a row of four nozzles 10 of the type described above. As shown in Figure 3, the nozzles 10 are spaced so that the plumes of water particles ejected from the nozzles meet at their greatest width.

As shown in FIG. 5 , the snowmaking apparatus S includes a mast M that is pivotable about an adjustable base structure B that includes three legs mounted on adjustable sliders 55 . Legs 51, 52, 53. The three legs 51, 52, 53 extend outwardly about 2 meters and are equally spaced around a common pitch circle. The legs 51, 52, 53 support an adjustable triangular support structure 60 on which the mast M is rotatably mounted. The mast comprises a base structure B concentrically mounted vertical post 61 having a rearwardly facing trailing edge arm 62 terminating in a mounting bracket 63 which in turn pivotally supports two Close and spaced parallelogram linkages 64,65. Parallelogram links 64, 65 pivotally support a head assembly H in the form of a pair of triangular support frames 66, 67 rigidly secured to the spray head H.

The spray head H is shown in FIG. 5 and consists essentially of an elongated water tube 71 called a manifold, from which extend four adjustable nozzle assemblies 10 of the type described above, as shown in FIGS. 7-9. Each nozzle 10 is also associated with a compressed air injector 75 , as shown in FIG. 5 . The injectors 75 are interconnected by pipes 76 and are supplied by a common source of compressed air. A row of nozzles 10 and air injectors 75 support a wind vane 74, as shown in FIGS. 1 and 3 . Compressed air and water are supplied to the head H through flexible pipes that extend down the mast M to the ground, as shown in FIG. 4 .

The parallelogram connecting rods 64, 65 are structures that are close in parallel and spaced apart. Each parallelogram link 64, 65 includes two elongated arms 68, 69 as shown in FIG. The other end is pivotally mounted on the triangular frame 66 or 67 on the spray head H. As shown in FIG. The parallelogram linkage is able to adopt different vertical positions, as shown in Figure 2. In the highest position, the arms 68, 69 extend vertically, while in the lowest position, the arms 68, 69 extend slightly below horizontal. In each case, the triangular support for the injector assembly is held at the same angle to the horizontal. The triangular frames 66 , 67 can be covered in panels to act as secondary wind blades for the main blade 74 . The parallelogram connecting rod is installed on the rear edge arm 80, and the rear edge arm 80 is connected with the spring 81, and the spring 81 is installed on the backward extending flange 82 of the base of the mast M. The spring 81 acts to push the parallelogram links 64, 65 so that they assume a vertical position, and the blade 74 is struck by the force of the wind to deflect the assembly downwards against the spring, resulting in a lower position. It should be understood that the springs are adjustable, and that other mechanisms such as pneumatic or hydraulic dampers could be substituted for the springs. The maximum height of the assembly S is about 6 meters.

As mentioned above, the spray head H comprises four adjustable flat nozzles, each flat nozzle being connected to a compressed air injector. The dependence of each adjustable flat nozzle 10 on compressed air is shown in FIGS. 9 to 11 . The air injector 75 is in the form of an inclined injector body 76 of triangular cross-section, which is inclined downward at 21° from the horizontal. The injector body 75 terminates in a plurality; preferably between three and fourteen; of small holes 77 . The underside of each hole 77 has a trailing edge fan-shaped groove 78, and the fan-shaped groove 78 cuts the underside of the air injector. The structure of the water injector 10 is such that as shown in FIG. The water hits the underside of the air injector 75 first when contacting the hole 77 . The hole 77 in the angled nozzle body end 79 is drilled so that it extends to the bottom surface to meet the trailing edge scalloped groove 78 . A thin edge defined at the top of the hole reduces the surface area for sticking ice. Also, the velocity of the water plume P clears the ice as it passes through the hole.

Figures 6a to 6c show the adjustability of the air nozzles and water jets 10. The air tube 76 is mounted on an elongated shaft 101 which is axially movable around a sleeve 102 which is held on the support bracket by screws. The injector 75 is then mounted on a shaft rotatable about a substantially horizontal axis, as shown in Figures 6a and 6c. The injector 75 can also be tilted relative to the air tube 76 via the flange bracket assembly 105, as shown in Figure 6c. The positions of the water jets and the water supply arm are substantially fixed on the support bracket as shown in Figures 6a, 6b and 6c.

The adjustment of the size of the nozzle hole is performed by moving the pins 21 , 22 . As shown in FIGS. 7 and 8 , in order to move the pins so as to vary the section of the outlet opening 20 of each nozzle 10 , the pin bearing sleeve 30 is connected to the slide 32 by means of a web 39 . The slide is positioned coaxially with the air tube 76 and each sleeve 32 is arranged to fit over the air tube 76 as shown in FIG. 7 a . All left sleeves 30 of the adjustable nozzle 10 are connected to the first elongated rod 90 and all right sleeves 30 are connected to the second elongated rod 91 . Rods 90 and 91 are bolted to each sleeve 32 such that movement of the rods 90 , 91 has the effect of moving the sleeve 32 to in turn move the pin 21 or 22 into and out of the bore 20 of each nozzle 10 . Rods 90 and 91 are coupled to threaded bosses 97 , 98 which externally support threaded rods 92 , 93 projecting from opposite sides of helical gear 94 . The helical gear 94 meshes with a second helical gear 95 which is connected to a shaft 96 extending downwardly from the mast so that it can be driven from the base of the mast. Thus, rotation of the shaft 96 rotates the two rods 92 , 93 protruding from the helical gear 94 . The two rods 92, 93 have opposite threads, so the left shaft has a left hand thread, which has the effect of moving the boss 97 to move the first rod 90 in a first direction, while the right shaft 93 has a right hand thread, which has the effect of moving the boss 97 in a first direction. The movement of the sleeve 98 has the effect of moving the rod 91 in the opposite direction.

Fine adjustment of the position of the pins 21 , 22 is possible by adjusting the threaded ends 26 of the pins inside the sockets with an Allen key as shown in Figures 8a and 8b.

12 to 16 show a second embodiment of a head 110 for snowmaking equipment. It should be understood that the head will be supported by a mast assembly of the type described above.

Head 110 includes four spray head assemblies 111-114 mounted across a main beam 115 in the form of a generally rectangular aluminum extrusion. The main beam 115 provides a secure base for each spray head assembly 111 - 114 and also supports a centrally located wind mechanism 120 which facilitates adjustment of the flat water nozzle 10 . A pair of elongated drive rails 116 , 117 , also extruded from aluminum, are positioned in parallel alignment behind the main beam 115 to be driven by the wind mechanism 120 to in turn move the adjustment pins 21 , 22 of the nozzle 10 .

As shown in FIG. 12 , the wind mechanism 120 is centrally positioned on the beam 115 and the four nozzle assemblies 111 - 114 are positioned equally spaced apart along the beam 115 . The wind mechanism 120 shown in more detail in Figure 15 includes a wind shaft (not shown) which exits from under the head. The shaft enters the wind block 121 and drives two coaxially extending shafts 123, 124 extending parallel to the rails from each side of the wind block through helical gears (not shown). The gears provide a 7:1 ratio for fine control and mechanical advantage. Each shaft is threadedly engaged with drive blocks 125 , 126 fixed on rectangular brackets 130 , 131 , and the rectangular brackets 130 , 131 are mounted on the main beam 115 in a sliding fit. Each drive block 125, 126 is reverse threaded such that rotation of shafts 123, 124 in the same direction causes linear movement of blocks 125, 126 in opposite directions and slides carriages 130, 131 in opposite directions. Each bracket 130, 131 is then bolted to a different drive rail so that, as shown in FIG. 5, the left bracket 130 drives the outer rail 117 and the right bracket 131 drives the inner rail 116. Rotation of the shaft entering the mast base in this way has the effect of causing the drive rails 116, 117 to move in opposite directions.

The nozzle assemblies 111 to 114 are identical, with one nozzle assembly 111 being shown in more detail in FIG. 16 . The nozzle assembly 111 includes a fixed center bracket 140 bolted to the main beam 115 . The rear surface 141 of the center bracket 140 is in turn welded to a flange 142 and a pair of vertical posts 143 , 144 which engage a nozzle arm support 150 . The center bracket 140 also supports a water jet body 145 in the shape of a rectangular block. The water jet body 145 includes a water inlet passage 146 from a water inlet pipe 147 and a head passage 148 in the manner of the above embodiments. The head channel 148 supports two adjustment pins 21 , 22 which move axially across the outlet aperture 20 in the same manner as the previous embodiment. The ends of the pins 21, 22 are bolted to flanges 152, 153 which are supported by pin drivers 154, 155 which enclose the main beam 115 so as to be slidable on the main beam 115 . Pin drivers 154, 155 are also secured to flanges 156, 157 which are bolted to drive rails 116, 117, respectively, such that movement of the drive rails moves the pin drivers.

The air nozzle 75 is coupled into the nozzle arm support 150 through the nozzle arm 160 so as to be coupled with the air supply pipe 161 . The nozzle arm support 150 is adjustable vertically by a nut 163 engaging the post 143, horizontally by a threaded connection 164 along the length of the arm, and by two pivotal links 165 connecting the air nozzle to the arm. Rotate in different planes. This universal adjustability enables fine adjustment of the relationship between the air nozzle 75 and the flat water nozzle 10 . This relationship is the same as that described above in the specification.

Referring to FIG. 15 , the operation of the wind mechanism 20 reverses the drive rails 116 , 117 to reverse the pin drivers 154 , 155 to move the pins 21 , 22 to change the cross-section of the outlet hole 20 of the flat nozzle 10. . Figures 14a, 14b illustrate actuation in order to move the pins towards each other (Figure 14a) and away from each other (Figure 14b).

An advantage of the assembly is that the use of square tubes provides positive guidance of the components and a strong support on which the nozzle assembly can be mounted. The nozzle assembly is also secured to the main support with some axial adjustment so that, during assembly, the position of the nozzle along the length of the main support can be varied. Since the movement of the pin is about a maximum of 4mm, the mechanism must have a certain level of precision in order to provide precise incremental changes. This is achieved by using a bracket structure with square tubes and a 2m head.

In order to explain the operation of the snowmaking equipment described above, and especially to explain the advanced and important features that lead to improved snowmaking technology, a general introduction to the scientific principles of snowmaking is first necessary.

artificial snow

Artificial snow is a heat exchange process. Heat is removed from the snowmaking water by evaporative and convective cooling, and released to the surrounding environment. This heat creates a microclimate within the snowplume that will be significantly different from ambient conditions. There are many variables that will affect snowmaking. The three most important variables are wet bulb temperature, nucleation temperature and droplet size. Wet bulb temperature; the temperature of the water droplets present in the snow gun; usually between +1°C and +6.5°C. Once the water droplet passes the nozzle and is released into the air, it rapidly decreases in temperature due to expansion and convective cooling, as well as evaporation effects. The droplet temperature will continue to decrease until equilibrium is reached.

This is the wet bulb temperature, which is just as important as the dry bulb (ambient) temperature in predicting snowmaking success. For example, artificial snowmaking at -2°C temperature and 10% humidity is equivalent to artificial snowmaking at -7°C temperature and 90% humidity.

Once the wet bulb temperature is known, it must also be estimated whether the water droplets will actually condense at that temperature. Ice is the result of a liquid (water) becoming solid (ice) through a condition called nucleation. In order to condense, a water droplet must first reach its nucleation temperature. There are two types of nucleation: homogeneous and heterogeneous nucleation.

Homonucleation occurs in pure water, where there is no contact with any other foreign substances or surfaces. The transition from the liquid state to the solid state occurs by homonucleation, by lowering the temperature or by changing the pressure. However, temperature has the main effect on the conversion of water to ice or ice to water. In homonucleation, nucleation begins when a very small volume of water molecules reaches the solid state. This small volume of molecules is called a nucleus and becomes the basis for further growth until all the water is transformed. The growth process is controlled by the rate at which the latent heat released is removed. Molecules stick to and leave the nucleus at approximately equal and very rapid rates. As more molecules attach to the nucleus, the release of energy makes the attached molecules cooler than the unattached molecules. Growth continues until all molecules are attached. At this point a solid state (ice) forms. Many people think that pure water freezes at 0°C or 32°F. In fact, nucleation (freezing) of pure water will take place down to -40°C or -32°F. This is more likely to happen in laboratory experiments, or more likely in the upper atmosphere (upper troposphere).

Heterogeneous nucleation occurs when ice forms at temperatures above -40°C or -40°F due to the presence of foreign material in the water. This foreign material acts as crystal nuclei and grows more rapidly than pure water nuclei. The location where ice nuclei form is called the ice nucleation site. Like homogeneous nucleation, heterogeneous nucleation is controlled by two main factors: the free energy change upon nucleation and the dynamics of fluctuating nuclei growth. In heterogeneous nucleation, the structure of the molecules and the interaction energy at the nucleation site will have a major influence on the transformation of water into ice. Artificial snowmaking involves a heterogeneous nucleation process. There are a variety of materials and substances that can act as nucleators; each promotes icing at a particular temperature, or nucleation temperature. These nucleating agents are generally classified as high temperature (ie, silver iodide, dry ice, ice, and nucleated proteins) or low temperature (ie, calcium, magnesium, dust, and silt) nucleating agents. Cryogenic nucleating agents are abundant in untreated snowmaking water. The nucleation temperature of water for artificial snow is between -10°C and -7°C.

The study found that 95 percent of natural, untreated water droplets will freeze over a wide range of temperatures, with an average temperature of 182°F. Introducing a consistent high temperature nucleant to water will raise the freezing point. As the water droplets cool, heat is released to the atmosphere at the rate of one calorie per gram of water. As it condenses into ice crystals, the droplet will release the rest of its energy at a rate of 80 calories per gram of water. This rapid release of energy raises the temperature of the water droplets to 32°F, which will still continue to freeze. This is the reason we are used to thinking that water freezes at 32°F or 0°C. As long as the water remains at or below 32°F or 0°C, the water will continue to freeze, but only after first cooling to its nucleation temperature. Any excess energy will be dissipated into the atmosphere. Because the distribution of different nucleating agents in a given volume of water is always random, the size of the water droplet or the number of high temperature nucleating agents has an important effect on the temperature at which freezing occurs (nucleation temperature). In pure water, as the droplet size decreases, the likelihood that the droplet will contain high temperature nucleating agents also decreases. Conversely, larger water droplets will be more likely to contain high temperature nucleating agents. The best-case scenario for a snowmaker is that every drop of water that passes through the nozzle of the snow gun contains at least one high-temperature nucleant and freezes in the plume.

The relationship between nucleation temperature change and droplet size was summarized into two statistically valid conclusions. First, a 50% increase in droplet size will result in a one degree F increase in nucleation temperature. Second, a 50% reduction in droplet size will result in a 3 degree F decrease in nucleation temperature. This conclusion is based on an average droplet size of 300 microns, suggesting that reducing droplet size may have the opposite effect on promoting high-temperature nucleation unless sufficient high-temperature nucleating agents are present. Observing the relationship between droplet size and evaporation, it has been shown in cloud seeding studies that a 50% reduction in droplet size increases the evaporation rate by a factor of 4. Droplets that are 50% smaller evaporate completely by falling to exactly one-eighth of the distance an average 300 micron droplet falls. This result further indicates that the use of very small droplets will produce undesired results, especially when water loss is a major concern. Regarding the relationship between droplet size and nucleation temperature, the production and efficiency of artificial snow can be increased by using high-temperature nucleating agents and larger water droplets. This method often increases water flow, reduces evaporation, and produces more snow on the ground. In fact studies have shown that a 20% increase in water flow can increase snow volume by 40% when droplet size and nucleation temperature are optimized.

summarize

The snowmaking process involves spraying water droplets into cool surrounding air, heat is transferred from the water droplets to the surrounding air, and the water droplets begin to freeze. When there is a sufficient temperature difference and sufficient suspension time between the water droplet and the air, the water droplet will condense before hitting the ground. The volume of water that can be turned into snow depends on many factors.

Initial Water Temperature - The higher temperature of the water means more heat needs to be removed before freezing occurs.

High Temperature Nucleating Agent - Once a water droplet reaches a temperature of 0°C, it requires the presence of a high temperature nucleating agent before the droplet can give off its latent heat and turn into snow.

Droplet Size - The size of a water droplet determines its ability to transform into snow. There are a number of ways to transform a stream of water into droplets of different sizes, using water nozzles and compressed air being the two main methods. Small water droplets provide a greater surface area relative to the surrounding air, but are prone to vaporization at low humidity and are less likely to have high-temperature nucleating agents. The smaller the water droplets, the less massive they are and are susceptible to higher winds that can carry them away - smaller particles also have lower velocities and longer suspension times. Small water droplets require edge snowmaking temperatures due to the larger surface area and longer suspension time which are advantageous when the temperature difference with the surrounding air is low. The larger surface area also contributes to the evaporative cooling effect.

Larger water droplets have smaller surface area, greater mass, higher velocity and greater chance of high temperature nucleating agents. When the surrounding air is colder, the temperature difference to the particle temperature is greater, so greater heat transfer can occur. The latent heat given off by the water particles is easily dissipated into the surrounding air. The faster the speed, the more heat exchange.

Thus, snow guns produce smaller droplet sizes in marginal conditions and larger particles in colder conditions.

Suspension Time - The longer the water droplets are in contact with the surrounding air, the more chances the particles have to condense. The greater the production of a snow gun, the higher it will be in the air. Droplets ejected at higher velocities also have greater suspension times. It is imperative to keep the snow gun as high as possible and shoot the pellets as fast as possible.

Water Volume - Although the above factors are given, only a certain volume of water will be able to turn into snow, depending on the efficiency of the above factors. Control of water volume needs to be included in any snow gun design in order to compensate for changes in ambient temperature.

High Temperature Nucleating Agent - Most snow guns have a system for generating high temperature nucleating agent primarily in the form of ice crystals. This is usually obtained by combining water and compressed air.

Compressed Air - Air is a gas, or rather a gas mixture. Unlike liquids, gases are compressible; a given volume of air can fit into a very small space. However, in order to fill this smaller space, the gas will have a higher pressure. Fundamental laws of physics state that the pressure of a gas and its volume are related to its temperature, and that as the pressure increases, so does the temperature. But the temperature doesn't have to stay high - it can go down.

When compressed air is released and returns to its original pressure, a large amount of mechanical energy is released. At the same time absorb a lot of heat. There are at least two features that make compressed air a very important factor in snowmaking. The mechanical energy released by the air causes the water stream to break up into fine droplets, which are then ejected into the atmosphere. When the compressed air leaves the gun, it absorbs heat - in other words cools.

State-of-the-art technology for artificial snow

There are currently four different methods of making snow:

1. Fan gun

2. Internal mixing air water gun

3. External mixing air water gun

4. Water gun only

Fan guns consist of a larger barrel with a surrounding electric fan that forces large volumes of ambient air through the barrel. At the end of the barrel there is a structure of water nozzles, usually arranged in rows, which can be opened independently of each other. Each row can include up to 90 small-capacity hollow-cone nozzles that produce very fine particles. The water particles are sprayed into the surrounding air by the mass of air generated by the fan. Fan guns usually have an outer ring called a coring ring. The ring has a small number of tiny air/water nozzles that work the same way as the internal mixing air/water nozzles. A compressor is used to operate the ring. The main function of the nucleation ring is to generate ice crystals. The ice crystals are transported along the exterior of the main water plume before being sucked into the plume and thus nucleating the main water plume. Operation of the fan gun is performed by opening a row of nozzles at a time and adapting the water pressure to the nozzles. Once you get enough pressure on one row, open the other row and adjust the water pressure.

Internal mix air/water lance consisting of compressed air and water lines converging into a common chamber with outlet holes. Compressed air enters the common chamber and expands, breaking up the water stream into smaller particles and ejecting them into the surrounding air. The operation of the gun is done internally by regulating the water pressure into the common chamber The common characteristic of the gun is that the air flow decreases when the water flow increases and vice versa. Water pressure usually cannot exceed air pressure, which is usually 80-125 psi. A variety of orifice and mixing chamber shapes are available to produce various plumes and droplet sizes.

External mixing air/water guns, usually comprising a fixed orifice flat nozzle structure arranged in the head, which sprays water into the surrounding air. The head is usually placed on the pole so that the water droplets have longer suspension time, because there is no compressed air to break the water flow into smaller particles or push them. Like the fan gun, the outer mixing gun has a nucleating nozzle that uses a smaller inner mixing nozzle to create ice crystals that are introduced into the main water plume. The control of the gun is done by changing the fixed orifice flat nozzles to different sizes or by opening multiple rows of nozzles like a fan gun.

Water Only Gun - The water only snow gun has no compressed air or nucleating nozzles. The head consists of multiple flat nozzles mounted on taller masts, usually at least 6 meters high. This snow gun can only be used at temperatures below -6°C, and it is best to work with high temperature nucleating additives.

preferred embodiment

The snowmaking equipment that is the subject of the present application differs from the prior art in that it uses components of maximum efficiency in the process. Snowmaking equipment S is an external mixing air/water lance utilizing an array of four variable nozzles 10 arranged on a flat horizontal plane, which nozzles produce a flat output pattern of water. Compressed air is introduced into the water plume P of the flat structure and has the same dimensions as the water plume at the point of intersection. A distinctive feature of this snowmaking equipment is that the lance is controlled by adjusting the nozzle aperture and thus changing the water flow. This allows maximum water pressure to be used to produce a constant droplet size with higher speed and thrust than normal snow guns.

Compressed air is introduced directly into the water plume P at the point where it has the greatest energy. The maximum energy from the compressed air greatly increases the evaporation of the water particles and enables maximum cooling and ejection of the water droplets. The temperature at the outlet of the air hole can be reduced to -40°C, which reduces the temperature of the main water plume to about 0°C or lower. The extremely cold air also produces ice crystals, some of which are carried in the main water plume, while some Ice crystals are blown out of the plume and re-breathed at greater distances. This high concentration of ice crystals ensures that there is enough high temperature nucleating agent to seed most of the water droplets.

When ice crystals are injected into the main water plume before the plume temperature is 0°C, the ice crystals will melt, which is why other external mixing guns will produce ice crystals that are injected into the plume at a greater distance from the water nozzle, so that , before the introduction of ice crystals, the main water has enough time to take away the heat in the water by the surrounding air. In windy conditions, some ice crystals may be blown away, reducing the nucleation of the main water.

An internal mixing gun uses compressed air in the same way, except it doesn't use water pressure energy, as it will adjust to control water flow. The maximum water pressure for most internal mixing guns usually does not exceed the compressed air pressure (ie 7 bar - whereas variable flat injectors can operate at pressures in excess of 40 bar). The nature of fixed chambers dictates that the more water used, the smaller the volume of air in the chamber and vice versa. Compressed air is the only means used to spray out and atomize the water; when the amount of compressed air is limited by the greater water flow, the efficiency will decrease. Because the energy of the water is not harnessed, the volume of compressed air used must be increased, making the gun more expensive and noisier to operate.

The snowmaking apparatus of the preferred embodiment uses the same amount of compressed air regardless of water flow, giving a more linear curve and allowing for greater production per pistol, and it allows direct air flow through the use of smaller air holes. Lower consumption of compressed air in the supply plume results in much quieter operation. The energies of these two media give the same efficiency, capable of producing a constant plume of water particles of uniform media size with the highest possible velocity and with high temperature nucleating agents (ice crystals).

Because the external mixing gun does not use compressed air to atomize the water plume, the droplets formed will be much larger with a greater range of different sizes within the plume. At lower pressures, the droplets can be as large as 1000 to 4000 microns, with preferred embodiments producing droplets in the 300 to 600 micron range.

The preferred embodiment has a very high plume velocity and surface area, which allows more ambient air to be drawn into the plume, thereby increasing cooling. Wind vanes 74 on the head H resemble pitched airfoils and direct wind from behind the head to accelerate past the nozzle exits, increasing the amount of cooling air entering the plume and helping to accelerate its velocity.

The preferred embodiment utilizes a portable mast structure which allows the positioning of the head at a height of 1 meter to 6 meters above the ground. The main mast part forms a parallelogram on top of which the head is mounted, maintaining a constant angle as the mast is lowered and raised, so that the trajectory of the plume is constant. Other snow gun poles have fixed poles so that as the pole is lowered, the angle of the head is progressively more towards the ground, making the snow gun less effective. Most external mixing guns cannot be lowered because they rely on the height of the mast to create sufficient suspension time for the droplets to freeze. The device of the preferred embodiment is capable of producing snow efficiently at 1 meter above the ground - efficiency increases with height.

Most of the 6m poles used for snow guns are in permanent fixed ground positions. The apparatus of the preferred embodiment can be towed by a snowmobile and placed in various locations. The legs of the mast are fitted with sliders so that it can be easily towed and the standoffs are adjustable so that the mast can be leveled on uneven terrain, see Figure 4. The flat shape of the support reduces the threat to the skier. The main mast is rotatable at the base, which allows the head to turn with the wind. The wind vanes on the head H catch the wind and push the head downstream of the wind in the same way as a vane. This increases the efficiency of the gun, as headwinds affect the efficiency of the plume by blowing the main water and reducing surface area and velocity. The mast is balanced by a spring 81 which quickly and easily raises and lowers the mast. The wind blades 74 are tilted upwards and it automatically lowers in height by pushing the head closer to the ground in higher winds. This helps to deposit more snow on the piste; if the mast is held at its maximum height in high wind conditions, the resulting snow will have a greater chance of being blown away.

In thick ice conditions, the head is lowered under the ice's own weight so that it can be easily removed by personnel.

The device of the preferred embodiment has the same efficiency and output as a fan gun, but produces larger water particles. Buying a fan gun is more expensive and requires more electrical infrastructure on the mount, thus limiting its movement. Due to their size and weight, the movement of fan guns requires the use of expensive snowplowing machines. An expensive permanent tower design is also required to elevate the fan gun to 6 meters in the air, which presents additional hazards to personnel as the fan gun requires personnel to perform tasks at heights such as removing covers, controls, etc. deicing etc.

In a more advanced form of embodiment, the wet bulb temperature sensor incorporates an ambient temperature sensor which also detects the temperature of the water. Also includes water pressure sensor. The computer continuously monitors the sensor readings and selects the optimum nozzle aperture to produce snow with maximum efficiency under the set conditions. Therefore, the use of an electrically powered servo motor enables continuous adjustment of the nozzle orifice in response to changing environmental conditions. Variations in the direction and strength of the wind are accommodated by vanes at the mast head which point the mast downwind and the head at the proper height dictated by the wind. Parallel links ensure that the nozzle can be tilted at right angles to the horizontal regardless of the effective height of the mast.

Claims (24)

1. A nozzle for producing a flat spray pattern, the nozzle comprising a fluid passageway terminating in an end wall having an outlet orifice, the fluid passageway having at least one deflector to deflect fluid toward the orifice; and adjustable means to vary the cross-section of the bore.

2. The nozzle of claim 1, wherein the fluid passageway has two deflectors in the shape of wall portions converging toward the orifice.

3. A nozzle as claimed in claim 1 or claim 2, wherein the means for varying the cross-section of the bore comprises a movable shutter moving from opposite sides of the bore so as to reduce or increase the cross-section of the bore.

4. A nozzle according to any preceding claim, wherein the end wall is provided with a cross member extending across the end of the fluid passageway, the cross member supporting an axially movable pin adapted for movement across the aperture so as to reduce or increase the cross-section of the aperture.

5. Nozzle according to claim 4, wherein means are provided for controlling the axial movement of the pin.

6. A nozzle as claimed in claim 4 or 5, wherein the pins move the same distance in opposite directions when adjusting the cross-section of the bore.

7. A nozzle according to any one of claims 4 to 6, wherein the fluid passageway and the cross-member are circular.

8. The nozzle of claim 7, wherein the diameter of the fluid passageway is the same as the diameter of the cross member.

9. The nozzle of any one of claims 1 to 8 wherein each pin is coupled to an internally threaded block and a shaft is threadedly engaged with each block, whereby rotation of the shaft moves the blocks to move the pins in opposite axial directions.

10. A nozzle for producing a flat spray pattern, the nozzle comprising a tee, the legs of the tee being tubes defining a fluid passage and the head of the tee being a tube positioned across the ends of the fluid passage, a bore being positioned in the head of the tee in axial alignment with the fluid passage, the head tube defining two deflectors which converge towards the bore, a pin terminating in a flat end surface being positioned at each end of the head of the tee so as to be movable along the tee so that the end surface of the pin can move across the bore so as to vary the cross-section of the bore.

11. The nozzle of claim 10, wherein the pin is threadably engaged with the head of the tee, whereby axial movement of the pin across the bore is effected by rotation of the pin.

12. Snowmaking equipment comprising at least one nozzle according to any one of the preceding claims, the nozzle being inclined upwardly in use to emit a plume of water droplets, the nozzle being positioned adjacent the jet of compressed air, the cross-sectional variation of the orifice affecting the characteristics of the plume.

13. A snow grooming apparatus comprising at least one flat water nozzle inclined upwardly in use to project a plume of water droplets, the nozzle being positioned adjacent a jet of compressed air, the nozzle having an outlet orifice; and means for varying the cross-section of the orifice in order to adjust the characteristics of the plume to suit the environmental conditions.

14. Snowmaking equipment according to claim 12 or 13, wherein an ejector of compressed air is provided downstream of the nozzle.

15. The snowmaking equipment according to claim 14, wherein the jet of compressed air comprises a row of holes.

16. The snowmaking equipment of claim 15, wherein the width of the sprayer is equal to the width of the plume of water droplets.

17. The snowmaking equipment according to any one of claims 12 to 16 wherein the plume of water droplets escaping from the nozzle is directed tangentially against the underside of the air jet.

18. The snowmaking equipment according to any one of claims 12 to 17, wherein four flat nozzles are positioned at intervals in the horizontal plane, the spacing of the nozzles being equal to the maximum width of each plume.

19. Snowmaking equipment according to any one of claims 12 to 18, wherein the water nozzles, nozzles and jets of compressed air are supported on a head which is pivotally inclined to the self-erecting mast.

20. The snowmaking equipment of claim 19, wherein the mast is rotatable about a vertical axis.

21. The snowmaking equipment according to claim 19 or 20, wherein the head is vertically adjustable relative to the mast while maintaining the angle of inclination of the water and air nozzles.

22. The snowmaking equipment according to any one of claims 19 to 21, wherein the head includes four nozzles spaced so that the plumes meet at their widest point.

23. A nozzle substantially as herein described with reference to and as illustrated in the accompanying drawings.

24. Snow making apparatus substantially as herein described with reference to and as illustrated in the accompanying drawings.

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