fan

Abstract

A fan is disclosed comprising a nozzle having an air outlet through which an air flow is discharged in an axial direction. The fan comprises an axial disturbance device for imparting velocity disturbances to the air flow in the axial direction at a first frequency.

Description

TECHNICAL FIELD

[0001] The present invention relates to a fan, in particular a room fan or a table fan. BACKGROUND

[0002] It is known to provide fans with relatively large diameter nozzles which correspondingly discharge larger diameter jets. This can be desirable, for example, to provide air to a larger volume of a room, or to a larger area of a user's head and / or body. In practice, design constraints such as fan size or aesthetic considerations are often limiting factors in the size of the fan (e.g. room fan or table fan) nozzle. SUMMARY

[0003] The present invention provides a fan comprising a nozzle having an air outlet through which an air flow is discharged in an axial direction; and an axial perturbation device for imparting velocity perturbations to the air flow in the axial direction at a first frequency.

[0004] The perturbation device can therefore cause a series of annular vortices to be generated at the air outlet at the first frequency. The vortices can be aligned in the axial direction. The series of vortices can cause the jet to expand radially with respect to the axial direction. That is, for a given nozzle diameter, the velocity of the jet can be increased in the axial direction by perturbing the jet, which can increase the diameter of the jet downstream of the outlet. This can improve the versatility of a fan having a nozzle of fixed shape and / or diameter.

[0005] The first frequency can be selected to correspond to the natural frequency of an annular vortex mode in the jet. This can cause amplification of the annular vortex mode, resulting in coherent annular vortices on the scale of the nozzle or jet diameter.

[0006] Optionally, the fan is operable in a first operating mode in which the axial perturbation device is inactive, and a second operating mode in which the axial perturbation device is active and imparts velocity perturbations to the air flow at the first frequency.

[0007] In this way, the fan can be operated in a first operating mode in which the air jet is discharged from the nozzle without perturbing the air flow, which can reduce entrainment of ambient air into the jet. This can be advantageous in the case that the air is conditioned air, for example purified air. The fan can also be operated in a second operating mode in which the air flow is perturbed in the axial direction to increase the diameter of the jet downstream of the nozzle, for example to jet air towards a user's face or a larger area of the body.

[0008] Optionally, the fan comprises a radial perturbation device for imparting velocity perturbations to the air flow in a plane orthogonal to the axial direction at a second frequency.

[0009] For example, the radial perturbation device can apply the velocity perturbation in a radial direction orthogonal to the axial direction at the second frequency, and / or apply the velocity perturbation helically around an axis aligned with the axial direction. This can cause successive toroidal vortices in the series of toroidal vortices to be radially displaced relative to one another. As a result, the airflow in the jet can be entrained by the radially displaced toroidal vortices, and the jet can expand or split in one or more radial directions, or the jet can inflate and expand in all directions. In this way, the fan can provide variable airflow characteristics, such as different shaped jets, from a single nozzle.

[0010] Optionally, the ratio of the first frequency to the second frequency is greater than 1. The ratio of the first frequency to the second frequency can be at least 2. This can allow the jet to expand or split in at least one radial direction, for example so that the jet forks in a plane of bifurcation aligned with the axial direction.

[0011] Optionally, the ratio of the first frequency to the second frequency is not greater than 4. This can allow the jet to expand or split in more than one plane parallel to the axial direction. This can limit the range of the first and / or second frequencies.

[0012] Optionally, the fan can be operable in a first operating mode in which the axial and radial perturbation devices are inactive, a second operating mode in which the axial perturbation device is active and applies a velocity perturbation to the airflow at the first frequency, and the radial perturbation device is inactive, and a third operating mode in which the axial perturbation device is active and applies a velocity perturbation to the airflow at the first frequency, and the radial perturbation device is active and applies a velocity perturbation to the airflow at the second frequency.

[0013] In this way, the axial and radial perturbation devices can cooperate to induce a change in the behaviour of the jet, for example causing the jet to split or expand in one or more directions.

[0014] Optionally, the fan can be operable in a fourth operating mode in which the radial perturbation device applies a velocity perturbation to the airflow at a third frequency, and the third frequency is different to the second frequency.

[0015] In this way, in the fourth operating mode, the behaviour of the jet can be different to the jet in the third operating mode, for example to increase the versatility of the fan.

[0016] Optionally, the second and third frequencies are selected so that the airflow expelled from the nozzle forks in the third operating mode and inflates in the fourth operating mode.

[0017] In the third mode of operation, the first frequency can be an integer multiple of the second frequency, or can be sufficiently close to an integer multiple of the second frequency, for example, twice or three times the second frequency. In this way, each toroidal vortex produced can follow the path of another toroidal vortex produced previously. That is, the vortex can move in a regular, repeating pattern around an axis aligned with the axial direction, which can result in the jet splitting or expanding in one or more radial directions.

[0018] In the fourth mode of operation, the frequencies can be selected such that successively produced toroidal vortices move in an irregular pattern around an axis aligned with the axial direction. That is, one vortex can not follow exactly the path of another vortex produced previously. In this way, the toroidal vortices can interact to cause the jet to inflate and expand in multiple radial directions, which can be arbitrary radial directions.

[0019] Optionally, the ratio of the first frequency to the second frequency is about 2.0, and the ratio of the first frequency to the third frequency is about 2.5.

[0020] That is, the first frequency can be twice the second frequency, to cause successively produced vortices to be displaced alternately on opposite sides of the axis in a plane parallel to the axis. This can form a series of radially staggered toroidal vortices in a plane downstream of the nozzle. Depending on the first and second frequencies, the vortices can be displaced in one or more radial directions. Thus, the airflow in the jet can be entrained by the radially displaced toroidal vortices, causing the jet to expand in one or more radial directions. The jet can split or bifurcate into two or more jets.

[0021] In this way, in the third mode of operation, the fan can provide a split or expanded jet from a single nozzle. For example, the jet expelled from the nozzle in the third mode of operation can be directed at two or more users simultaneously, or can expand in a vertical direction to improve coverage of a user’s body.

[0022] In the fourth mode of operation, the jet can inflate or expand in multiple radial directions. This can provide a more dispersed airflow to a room. This effect can be achieved without any baffles or other such devices. The inflated jet can increase entrainment and mixing of the ambient air, which can be advantageous when supplying conditioned air to a room.

[0023] Optionally, the radial perturbation device comprises an actuator configured to oscillate the air outlet at the second frequency.

[0024] The actuator can be mechanically and / or magnetically coupled to at least a portion of the nozzle, such as the nozzle tip. The actuator can be any suitable actuator, such as an electromechanical actuator, an electromagnetic actuator, a hydraulic actuator, or a pneumatic actuator. For example, the radial perturbation device can include one or more actuators for imparting linear motion in one or more corresponding radial directions. In this way, the nozzle can be oscillated in a linear, elliptical, or circular motion by one or more actuators. Alternatively, the actuator can include a motor and a connecting rod or a suitable gear system for causing circular motion of the air outlet.

[0025] Alternatively, the radial perturbation device may be an acoustic perturbation device, for example comprising one or more acoustic devices, such as speakers, arranged circumferentially around the air outlet. Adjacent acoustic devices may be operated sequentially at a second frequency to impart a helical velocity perturbation to the airflow discharged from the nozzle. Alternatively, opposing acoustic devices arranged on either side of the air outlet may be operated sequentially at a second frequency to impart a radial velocity perturbation to the airflow discharged from the nozzle.

[0026] Optionally, the actuator oscillates the air outlet with a peak to peak amplitude greater than 1% of the nozzle diameter.

[0027] The nozzle diameter may be the diameter of the air outlet. The actuator may oscillate the air outlet with a peak-to-peak amplitude between 1% and 10% of the nozzle diameter, or equal to or greater than 10% of the nozzle diameter. The actuator may oscillate the air outlet with a peak-to-peak amplitude between 3% and 7% of the nozzle diameter, such as 5% of the nozzle diameter. For example, when the nozzle diameter is approximately 92 mm, the radial perturbation device may displace the air outlet by between 2 mm and 6 mm, such as between 3 mm and 5 mm, such as 4 mm.

[0028] Optionally, the axial perturbation device is an acoustic perturbation device.

[0029] In this way, the fan may comprise fewer moving parts.The acoustic perturbation device may be electronically controlled, which may improve control over the frequency and / or amplitude of the perturbations.

[0030] Alternatively or additionally, the axial perturbation device may comprise a mechanical or electromechanical component, such as a movable blade, a flow restrictor, or a flexible wall or membrane. The fan may comprise a duct for conveying air from the air flow generator to the nozzle, and the axial perturbation device may vary the air flow velocity in the duct, thereby perturbing the velocity of the air flow discharged from the nozzle in the axial direction.

[0031] Alternatively, the axial perturbation means may move the air outlet in an axial direction at a first frequency, for example by moving at least a portion of the nozzle back and forth in an axial direction, or it may comprise means for deforming the shape of the nozzle, for example for changing the diameter of the nozzle at a first frequency.

[0032] Optionally, the velocity perturbation applied by the axial perturbation means has a peak-to-peak amplitude greater than 1% of the air flow velocity at the air outlet.

[0033] The velocity perturbation can have a peak-to-peak amplitude between 1% and 50%, or equal to or greater than 50%. The velocity perturbation can have a peak-to-peak amplitude of approximately 25%. For example, the average outlet velocity at the air outlet can be between 2.5 metres per second (m / s) and 3.5 m / s, for example 3 m / s, and the peak-to-peak amplitude of the axial perturbation can be between 0.03 m / s and 1.5 m / s, for example 0.75 m / s. Increasing the amplitude of the perturbation can increase the strength of the vortex, which can increase the effect of the jet expansion, splitting and / or inflation, for example by increasing the expansion or bifurcation angle of the expanding or split jet.

[0034] Optionally, the air flow is discharged at a flow rate of between 10 l / s and 100 l / s.

[0035] Optionally, the diameter of the air outlet is between 45 mm and 200 mm.

[0036] Optionally, the first frequency is less than 60 Hz.

[0037] In this way, jet splitting and / or expansion can be achieved at a first and / or second frequency in the audible range which is lower. The first and second frequencies can be sub-audible, for example less than 30 Hz, less than 25 Hz or less than 20 Hz. The first frequency can be between 10 Hz and 30 Hz, and / or the second frequency can be between 5 Hz and 15 Hz.

[0038] That is, the nozzle diameter and air flow rate can be selected to provide the desired functionality at a sub-audible perturbation frequency. This can reduce the acoustic signature of the fan, which can be particularly advantageous where the axial and / or radial perturbation means is an acoustic perturbation means.

[0039] Applying an axial velocity perturbation to the air flow can result in an increase in entrainment of ambient air into the jet. By using a nozzle of relatively large diameter, reduced entrainment of ambient air can be achieved. This can be beneficial, for example, when using purified air. The reduction in entrainment of ambient air can result in higher purity air reaching the user. A larger diameter nozzle and / or a lower air flow rate can reduce the perturbation frequency required to achieve jet splitting, expansion and / or inflation, thereby reducing the acoustic signature of the fan.

[0040] Optionally, the fan comprises flow conditioning means for conditioning the velocity profile of the air flow delivered to and / or discharged from the nozzle.

[0041] The flow conditioning device can make the velocity profile of the air flow exiting the nozzle more uniform, e.g. more axisymmetric and / or less turbulent. The flow conditioning device can reduce vortex flow in the flow. The fan can comprise a duct for conveying the air flow, e.g. from an air flow generator to the nozzle. The duct can comprise a sedimentation chamber, which can act as a flow conditioning device.

[0042] Alternatively or additionally, the flow conditioning device can comprise a flow straightener in the duct and / or the nozzle. The flow straightener can comprise a mesh, a screen, a honeycomb structure or any other suitable flow straightener.

[0043] The flow conditioning device can improve the spreading, splitting and / or expanding function of the fan, e.g. in any of the first to fourth operating modes.

[0044] Optionally, the fan comprises a flow orientation device for controlling the direction of the air flow exiting the nozzle.

[0045] The flow orientation device is operable to control the direction of the air flow exiting the nozzle. That is, the flow orientation device can change the axial direction of the jet exiting the air outlet. The flow orientation device can control the direction of the spreading, splitting and / or expanding jet, e.g. in any of the first to fourth operating modes. For example, the plane of a radially spreading or splitting jet can be tilted in one or more different directions.

[0046] The fan can be operable in a fifth operating mode in which the flow orientation device continuously and / or periodically changes the direction of the jet exiting the nozzle, e.g. automatically directing a splitting or spreading jet in different parts of a room, or in the direction of two or more users.

[0047] Optionally, the flow orientation device comprises one or more guide vanes.

[0048] The guide vanes or louvres can be adjustable to adjust the direction of the air flow exiting the nozzle. Alternatively or additionally, the flow orientation device can comprise a gimbal device for gimbaling at least part of the nozzle to direct the air outlet in different directions.

[0049] The fan can comprise a flow straightener, and the orientation of at least part of the flow straightener can be changed to change the direction of the jet in any of the first to fifth operating modes. That is, the flow orientation device can comprise one or more adjustable flow straighteners.

[0050] Optionally, the fan is a room fan or a table fan.

[0051] The fan can be a fan heater, cooler, humidifier, dehumidifier, and / or purifier. The fan can include an airflow generator for generating an airflow that is delivered to the nozzle. The airflow delivered to and / or expelled from the nozzle can include conditioned air from an air conditioning device, e.g., a device configured to heat, cool, purify, humidify, and / or dehumidify air. BRIEF DESCRIPTION OF DRAWINGS

[0052] Embodiments will now be described, by way of example only, with reference to the accompanying drawings:

[0053] Figure 1 is a side view schematic of a fan according to one example;

[0054] Figure 2 is a front view schematic of a fan of Figure 1

[0055] Figure 3 is a front view schematic of an optional radial perturbation device of a fan of Figure 1

[0056] Figure 4 is a front view schematic of another optional radial perturbation device of a fan of Figure 1

[0057] Figure 5A is a side view schematic showing annular vortices resulting from operation of an axial perturbation device of a fan of Figure 1

[0058] Figure 5B is a side view schematic showing modification of a jet expelled from a fan of Figure 1

[0059] is a schematic of a jet expelled from a fan of Figure 1

[0060] is a schematic of a wide jet expelled from a fan of Figure 1

[0061] is a schematic of a bifurcated jet expelled from a fan of Figure 1

[0062] Figure 6D is a schematic of a diffuse jet expelled from a fan of Figure 1

[0063] Figure 7A is a schematic of a fan of Figure 1 ​​​​​​​​​a side view schematic of a fan of 1 in a jet expansion mode of operation showing example flow regulation and flow direction devices;

[0064] Figure 7B is Figure 7A a schematic of a fan of 1 showing a directed bifurcated jet resulting from operation of the flow direction devices;

[0065] Figure 7C is Figure 7A a front view schematic of an example cross section of the flow regulation or flow direction devices of 1 and / or 7B;

[0066] Figure 7D is Figure 7A and 7B a schematic of a fan of 1 showing optional flow direction devices. DETAILED DESCRIPTION

[0067] The details of the method and system according to the examples will become apparent from the following description, with reference to the drawings. In the description, numerous specific details are set forth in order to provide a thorough understanding of the examples. The description references "example" or the like, means that a particular feature, structure, or characteristic described in connection with the example is included in at least one example, but not necessarily in other examples. It should further be noted that the examples shown in the drawings are described in various

[0068] In the following description, examples are described in relation to a room or table fan having a circular nozzle. It will be appreciated that features and underlying concepts of the examples can be applied to other kinds of fans.

[0069] Figure 1 A side view of an example of a fan 10 is shown, including a duct 100 and a nozzle 200, which includes a converging portion 210 and an air outlet 230. The converging portion 210 converges from the duct 100 to a nozzle outlet 220. The air outlet 230 is arranged adjacent to the nozzle outlet 220. In this way, air received by the nozzle 200 is compressed via the nozzle outlet 220 towards the air outlet 230, thereby increasing the speed of the air flow. In other examples, the nozzle 200 is any other suitable shape, for example a diverging nozzle 200, or a straight nozzle 200, for example a constant diameter nozzle 200. The air flow is directed along Figure 1 The air flow is expelled through the air outlet 230 in an axial direction shown by arrow 310, thereby forming an air jet 300, which is for example directed into a room or towards a user. The axial direction 310 is parallel to the "z" coordinate, as shown in Figure 1The "x" and "y" coordinates define a plane that is orthogonal to the z coordinate. That is, the z coordinate corresponds to the axial direction 310, and the x and y coordinates correspond to radial directions, which in this example are perpendicular to the axial direction 310.

[0070] Figure 2 The fan 10 is shown as viewed along an axis parallel to the axial direction 310. The fan includes a circular air outlet 230, but other suitable shapes can be employed, such as an elongated or square air outlet 230.

[0071] In this example, the air outlet 230 abuts the nozzle outlet 220, as Figure 1 shown, and is movable relative to the nozzle outlet 220. A suitable seal is formed between the nozzle outlet 220 and the air outlet 230 so that air flows from the nozzle outlet 220 to the air outlet 230. In some examples, the air outlet 230 is spaced apart from the nozzle outlet 220, and a seal (not shown) is provided between the air outlet 230 and the nozzle outlet 220. In some examples, the nozzle outlet 220 is the air outlet 230. In some examples, the seal and / or the nozzle 200 is at least partially constructed of a flexible or otherwise deformable material to allow the air outlet 230 to move relative to the nozzle 230 and / or the conduit 100.

[0072] As shown by arrow 11 in Figure 1 , the conduit 100 receives air at one end thereof. The air is received by the conduit 100 from an air flow generator (not shown). Any suitable air flow generator can be used to supply air to the conduit 100, the nozzle 200, and / or the air outlet 230. For example, the air flow generator can include an impeller in an axial, centrifugal, or cross-flow arrangement. In some examples, the impeller is driven by an electric commutated (EC) motor, although this need not be the case in other embodiments.

[0073] In some examples, the air is supplied to the conduit 100 and / or the nozzle 200 via an air conditioning device for conditioning the air. The air conditioning device is any one of a heater, a cooler, a purifier, a humidifier, or any other air conditioning device. That is, in some examples, the air received by and expelled from the air outlet 230 is heated, cooled, purified, humidified, or otherwise conditioned. In some examples, the fan 10 includes the air flow generator and / or the air conditioning device. In other examples, the air flow generator and / or the air conditioning device is located away from the fan 10 and is configured to supply conditioned or unconditioned air to the fan 10.

[0074] In the present example, the conduit 100 is straight. In some examples, the conduit comprises a bend, such that the airflow from the airflow generator changes direction in the bend. In some examples, the conduit comprises a plurality of sections, comprising a combination of straight sections and curved sections. In some examples, the conduit comprises and / or sections of the conduit are interspersed between the flow conditioning devices described above and / or below with reference to Figures 7A-7D In some examples, the conduit 100 is absent, and the air is received by the nozzle directly from the airflow generator.

[0075] With reference to Figure 1 and 2 , the fan comprises an axial disturbance device 400 and a radial disturbance device 500. In some examples, the radial disturbance device 500 is absent, and the fan comprises only the axial disturbance device 400. The axial disturbance device is used to impose a velocity disturbance of an axial disturbance frequency on the airflow in the axial direction 300. In the present example, the axial disturbance device is an acoustic disturbance device comprising a loudspeaker 410, for example a subwoofer. The loudspeaker 410 is coupled to the conduit 100 by a channel 420. That is, the air on one side of the loudspeaker 410 is in fluid communication with the airflow in the conduit 100 via the channel 420. The loudspeaker oscillates in the direction indicated by arrow 400a in Figure 1 at an axial disturbance frequency. This imposes a sinusoidal velocity fluctuation on the airflow in the conduit 100, and hence on the airflow expelled through the air outlet 230. The average flow rate and velocity out of the nozzle are unaffected. The effect of applying the axial velocity disturbance is discussed below with reference to Figures 5A-5B .

[0076] In some examples, the axial disturbance device 400 is coupled to the nozzle 200, for example to the converging section 210, the nozzle outlet 220 or the air outlet 230. In some examples, the axial disturbance device 400 is comprised in the conduit 100 or the nozzle 200. In some examples, the axial disturbance device 400 comprises a mechanical or electromechanical component, for example a moveable paddle, restrictor or flexible wall or membrane within the conduit 100, for example for varying the air flow rate in the conduit 100. In some examples, the axial disturbance device 400 comprises an actuator (not shown) for moving the nozzle 200 and / or the air outlet 230 back and forth along the axial direction 310, for example to impose the axial velocity fluctuation directly into the airflow expelled from the air outlet 230. In some examples, the axial disturbance device 400 comprises a device for deforming the shape of the nozzle 200 and / or the air outlet 230, for example for varying the diameter of the air outlet 230 at the axial disturbance frequency.

[0077] The radial perturbation device 500 includes a radial actuator 510, for example a piston 510 including a connecting arm 511 connected to the air outlet 230. The air outlet 230 here is a ring including a circular opening, and the connecting arm 511 is connected to the ring. The radial actuator 510 is configured to oscillate at a radial perturbation frequency, such that the connecting arm 511 moves in a direction indicated by the arrow 500a here aligned with the y coordinate. This causes the air outlet 200 to oscillate in a direction indicated by the arrow 500b here also aligned with the y coordinate, at the radial perturbation frequency. This is to impart a radial velocity fluctuation at the radial perturbation frequency to the air flow expelled from the air outlet 230. Figure 2 Figure 2

[0078] The radial actuator 510 is any suitable kind of actuator, for example a mechanical, electromechanical, hydraulic or pneumatic actuator. In the present example, the radial actuator 510 includes a loudspeaker configured to move the connecting arm 511. In some examples, the radial actuator 510 includes any other suitable electronic mover, for example a piezoelectric actuator or a servo-controlled motor arrangement.

[0079] In some examples, the radial perturbation device 500 is configured to move the air outlet 230 in more than one radial direction. In some examples, the radial perturbation device 500 includes more than one radial actuator 510 connected to the air outlet 230 or other part of the nozzle 200 to move the air outlet 230 in a respective more than one radial direction. That is, in some examples, the radial perturbation device 500 includes more than one radial actuator 510 that are spaced apart circumferentially around the air outlet 230 and oriented at different angles relative to the air outlet 230. In some examples, moving the air outlet in more than one radial direction includes moving the air outlet in a circular motion.

[0080] Figure 3 Such an arrangement is shown including a plurality of radial actuators 520a-520d spaced apart circumferentially around the air outlet. In this example, the radial actuators 520a-520d are electromagnetic actuators 520a-520d including at least one electromagnet switchable to produce an electromagnetic field. The air outlet 230 here includes a ferrous material, and when the electromagnet is operated to produce an electromagnetic field, the air outlet 230 is attracted to the electromagnet 520a-520d. In this way, by sequentially activating opposing electromagnets, the air outlet 230 can be moved in at least one radial direction, for example in the x or y direction. For example, by sequentially activating the magnets along a circumference, the air outlet 230 can be moved in a circular motion.

[0081] In some examples, Figure 3 ​​The radial actuators 520a-520d of the radial perturbation device 500 are any suitable actuators, such as those described above with reference to Figure 1 and Figure 2 In other examples, the radial perturbation device is an acoustic perturbation device that includes, for example, one or more speakers directed toward the air outlet in one or more radial directions. That is, in some examples, Figure 1 and 2 the radial actuators 510 and / or Figure 3 the radial actuators 520a-520d are replaced with acoustic perturbation devices. In this way, the radial perturbation device 500 can be configured to impart sinusoidal radial velocity fluctuations to the air stream expelled from the nozzle without physically moving the air outlet.

[0082] Figure 4 An example alternative arrangement for moving the air outlet 230 in a circular motion is shown. In this example, the radial actuators 530a, 530b are electric motors 530a, 530b coupled to the air outlet 230 via respective links 540a, 540b. Each link includes first and second connectors 541a, 542a, 541b, 542b. With reference to one of the electric motors 530a, the second connector 542a is coupled to the shaft of the electric motor 530a eccentrically via the first connector 541a. That is, the second connector 542a is offset from the center of the shaft of the electric motor 530a. In this way, operation of the electric motors 530a, 530b in the directions shown by the arrows labeled 550a, 550b in Figure 4 causes the air outlet 230 to move in a circular motion in the x-y plane, as shown by the arrow labeled 560 in Figure 4 . The electric motors 530a 530b are any suitable electric motors known to those skilled in the art, such as servo motors. In some examples, there are any number of electric motors 530a, 530b, such as only one electric motor or more than two electric motors. In other examples, the air outlet 230 is moved in one or more radial directions in any suitable way, such as in a circular motion, for example, by using any other suitable links and / or transmission systems, such as by using a sun gear or cam system.

[0083] We now discuss the operation of the fan 10 with reference to Figures 5A to 7D .

[0084] Low-entrainment mode

[0085] In the present example, the fan 10 can operate in a low entrainment operating mode in which the axial and radial perturbation devices 400, 500 are inactive and the entrainment of ambient air into the jet 300 is relatively low. That is, in the low entrainment operating mode, the air stream expelled from the nozzle 200 passes through the air outlet 230 without being perturbed by the axial and radial perturbation devices. Figure 6A shows a schematic view of the jet 300 expelled from the air outlet 230. The jet 300 has a potential core (not shown) which extends downstream of the air outlet 230, for example between 4 and 7 times the diameter of the air outlet 230 downstream of the air outlet 230, for example between 5 and 6 times the diameter of the air outlet 230. The potential core is primarily composed of air expelled from the fan 10, for example conditioned air as described above. Outside the potential core, ambient air surrounding the jet 300 begins to mix with the air in the jet 300. Accordingly, in some examples, it is desirable to increase the diameter of the air outlet 230 in order to minimise entrainment and increase the length of the potential core, thereby ejecting the conditioned air further downstream of the nozzle 200 into the room and / or towards the user.

[0086] Medium entrainment mode

[0087] The fan 10 of the present example can operate in a medium entrainment operating mode in which the axial perturbation device 400 is active, while the radial perturbation device 500 is inactive. In the medium entrainment mode, the axial perturbation device 400 is configured to impart velocity perturbations or fluctuations to the air stream expelled from the air outlet 230 at an axial perturbation frequency, as described above. The axial perturbation frequency is selected to correspond to the natural frequency of a toroidal vortex mode in the jet. In this way, as shown in Figure 6B, the axial perturbation device 400 causes a series of toroidal vortices 350a, 350b to be generated at the air outlet at the axial perturbation frequency. The toroidal vortices 350a, 350b are toroidal vortices which travel in the axial direction 310 and have a central axis (not shown) which is aligned with the axial direction 310. Each toroidal vortex 350a, 350b is substantially circular when viewed along the axial direction 310, for example due to the shape of the air outlet 230. Figure 5A Figure 5A A cross-section through the toroidal vortices 350a, 350b in the y-z plane is shown. The air flow within the toroidal vortices is moving faster than the air flow outside the toroidal vortices. In this way, the local air flow circulates around an imaginary axis, forming a closed loop around the central axis, as indicated by the arrows labelled 351. The diameter of each toroidal vortex 350a, 350b is comparable to the diameter of the air outlet 230. In some examples, the diameter of each toroidal vortex 350a, 350b increases as the vortex 350a, 350b travels downstream from the air outlet 230. Figure 5A

[0088] ​​Local circulation 351 causes the air in jet 300 to expand in all radial directions. That is, annular vortices 350a, 350b entrain air flow in jet 300 to increase the diameter of jet 300 downstream of nozzle 200. This is illustrated schematically in FIG. 6B. Here, the modified jet is shown with solid line 320, while the jet 300 produced in the low entrainment mode of operation is shown with dashed line 300. In the medium entrainment mode of operation, annular vortices 350a, 350b generally increase the entrainment of ambient air into jet 320. This results in a shorter potential core. The medium entrainment mode of operation can be used in examples to increase the area of air flow that is ejected into a room or towards a user, for example to cover more of the user’s face or body.

[0089] Jet expansion mode

[0090] Fan 10 of the illustrated example can be operated in a jet expansion mode of operation. In the jet expansion mode of operation, both axial and radial perturbation devices 400, 500 are active. That is, as described above, the axial perturbation device imparts axial velocity perturbations to the air flow discharged from air outlet 230 at an axial perturbation frequency, while the radial perturbation device imparts one or more radial velocity perturbations to the air flow discharged from air outlet 230 at a radial perturbation frequency. As Figure 5B illustrated, this results in successive annular vortices 350a, 350b in the series of annular vortices produced by operation of axial perturbation device 400 being radially displaced relative to one another. In the illustrated example, the forced ratio of the axial perturbation frequency to the radial perturbation frequency is 2, and air outlet 230 oscillates back and forth in the y direction as Figure 5B indicated by arrows labelled 500c. That is, the axial perturbation frequency is twice the radial perturbation frequency. In other examples, air outlet 230 moves in a circular motion as described above at the radial perturbation frequency, which is half the axial perturbation frequency.

[0091] Operating the axial and radial perturbation devices at a forced ratio of 2 results in successive annular vortices 350a, 350b being produced on opposite sides of an axis aligned with axial direction 310. This results in vortices 350a, 350b being radially staggered downstream of air outlet 230, as Figure 5B illustrated. Successive vortices 350a, 350b interact with one another such that the central axis of each vortex is tilted away from the axial direction. In this way, the successively produced annular vortices 350a, 350b travel in opposite directions that are tilted away from axial direction 310. Annular vortices 350a, 350b entrain air flow in jet 300 to pull jet 300 towards either side, resulting in jet 300 expanding in the y direction. In some examples, as illustrated in the schematic of FIG. 6C, jet 300 splits into two distinct jets 330a, 330b.

[0092] In the illustrated example, the airflow in the jets 330a, 330b is ejected in first and second diverging directions 331a, 331b that diverge from one another at a divergence angle a. That is, the jet 300 expands in a divergence plane that is oriented parallel to the axial direction 310 and parallel to the first and second diverging directions 331a, 331b. The angle a can be increased by increasing the amplitude of the radial and / or axial perturbations. Increasing the axial and / or radial perturbation amplitude can increase the jet intensity, resulting in well-defined diverging jets 330a, 330b. Selecting a ratio of three results in a triviation or expansion of the jet 300 in three radial directions. For example, when the air outlet 230 is moved in a circular motion by the radial perturbation device 500 at a forced ratio of 3, successive annular vortices 350a, 350b are ejected at three equidistant locations around a circle described by the center of the air outlet 230 when viewed along the axial direction 310. This results in the annular vortices 350a, 350b expanding helically downstream of the air outlet 230 and results in the jet 300 expanding in three directions (not shown). In other words, in the jet expansion operating mode, the axial perturbation frequency is an integer multiple of the radial perturbation frequency, for example 2, 3 or no more than 4 times the radial perturbation frequency, to induce expansion or splitting of the jets 330a, 330b in one or more radial directions.

[0093] Diffusion mode

[0094] In the present example, the fan can be operated in a diffusion operating mode in which both the axial and radial perturbation devices 400, 500 are active. In this operating mode, the air outlet 230 is moved in a circular motion as described above, although in other examples the air outlet 230 is moved in a plurality of other radial directions. In the diffusion operating mode, the axial perturbation frequency is a non-integer multiple of the radial perturbation frequency. That is, the forced ratio is a non-integer, for example a number between 1 and 2, between 2 and 3 or between 3 and 4. In this way, the successively generated annular vortices 350a, 350b move in an irregular pattern around an axis aligned with the axial direction 310. That is, one vortex 350a can not follow exactly the previous generated other vortex 350b.

[0095] In the diffusion operating mode, the forced ratio is suitably far from an integer, for example more than 0.2 or 0.3 units from an integer, so that the annular vortices 350a, 350b interact to expand the jet in a plurality of radial directions, which can be arbitrary radial directions. This increases the entrainment of ambient air into the jet 300 and results in the jet becoming as Figure 6DA diffuser jet 340 is shown. This may be referred to herein as an expansion jet 340. In some examples, for example, an expansion jet 340 with a high level of entrainment may better mix the conditioned air exhausted from the fan 10 with the ambient air in the room. This may be to better heat, cool, purify, or otherwise condition the air throughout the room.

[0096] Precession mode

[0097] In some examples, the fan 10 is operated in a precession mode of operation. Here, the axial and radial perturbation devices 400, 500 are operated using non-integer forcing ratios, such as in an expansion mode of operation, where the forcing ratios are close enough to integers so that the successively generated annular vortices 350a, 350b closely (but not exactly) follow the paths of the previously generated annular vortices 350a, 350b. In some examples, the forcing ratios are within 0.2 or 0.1 units of an integer. In this way, the jet 300 is caused to diverge or expand in one or more radial directions 330a, 330b, as shown in FIG6C. The expanding or diverging jets 330a, 330b precess about an axis aligned with the axial direction 310.

[0098] Flow regulation and direction

[0099] Figure 7A Shown Figure 1 1 , which includes a flow conditioning device 600 for adjusting the velocity profile of the airflow delivered to the nozzle 200. In this example, the flow conditioning device 600 is a flow straightener 600 that is used to make the velocity profile more uniform, e.g., more axisymmetric and / or less turbulent. A more uniform velocity profile is desirable to improve the formation of the annular vortices 350a, 350b and thereby improve the expansion, splitting, and / or expansion functions of the fan 10, as described above.

[0100] The flow straightener 600 of this example is located in the duct 100. In other examples, the flow straightener 600 is positioned at any suitable location upstream of the air outlet 230. In some examples, the flow straightener 600 is located after a curved portion of the duct 100, or between an air flow generator (not shown) and the air outlet 230. The flow straightener 600 has a profile suitable for straightening the airflow. Figure 7C Schematic diagrams of two example profiles when viewed in the z-direction are shown, such as a mesh profile 601 and a blade profile 602, although other profiles, such as a honeycomb or other hexagonal close-packed profiles, are also contemplated. In other examples, the flow conditioning device 600 alternatively or additionally includes a settling chamber (not shown) in the conduit 100. The settling chamber includes a portion with a relatively wide diameter and / or a relatively long portion along the direction of airflow through the conduit 100, such that the velocity distribution forms a more uniform velocity distribution through the settling portion.

[0101] In some examples, the fan 10 includes a flow direction device 610 operable to control the direction of the air stream expelled from the nozzle. In this example, the flow direction device 610 includes a flow straightener 600 having any suitable flow straightener profile 601, 602 as described above with reference to Figure 7C The flow direction device is pivotably mounted in the nozzle outlet 220, which here is also the air outlet 230, at a pivot point 611. In some examples, the flow direction device 610 is provided in a separate air outlet 230 as described above.

[0102] Operation of the flow direction device 610 includes pivoting the flow direction device 610 about the pivot point 610 to orient the flow straightener profile 601, 602 in different directions. This will change the axial direction 310 of the jet 300 expelled from the air outlet. Thus, the flow direction device 610 can be used both to straighten the air stream passing through the air outlet 230, thereby providing the benefits described above, and to direct the jet 300 expelled from the air outlet 230. In various examples, the flow direction device 610 is operable to control the direction of the low-entrainment jet 300 in low-entrainment mode, the medium-entrainment jet 310 in medium-entrainment mode, the split or expanded jet 330a, 330b in split mode, the diffusion or inflated jet 340 in diffusion mode, and / or the precessing jet 330a, 330b in precession mode. For example, the plane of the radially expanded or split jet 330a, 330b can be tilted in one or more different directions.

[0103] In some examples, the fan 10 can be operated in a flow direction operating mode in which the flow direction device 610 continuously and / or periodically changes the direction of the jet 300 expellable from the nozzle 200 in any of the operating modes described above. In some examples, this is done automatically, or manually at the request of a user, to direct the split or expanded jet to different parts of a room, or in the direction of one or more users.

[0104] In some examples, the flow direction device 610 can take any other suitable form. In some examples, the flow direction device 610 includes a flow straightener 600 having a vane profile 602 or "louver profile 602", and each guide vane or louver is pivoted individually about a respective axis. Figure 7D A schematic view of such an example flow direction device 610 is shown, which includes individual guide vanes 620 and corresponding pivot points 621. It will be appreciated that moving the guide vanes 620 together has the same effect in directing the jet 300 as moving the flow direction device 610 about a single pivot point 611. Figure 7A and 7BThe flow directing device 610 has a similar effect.

[0105] In other examples, the flow directing device 610 includes a universal joint mechanism (not shown) for directing the nozzle 200, the nozzle outlet 220, and / or the air outlet 230 in different directions. In this case, the nozzle 200 can be constructed of a flexible material to allow relative movement of the air outlet 230 relative to the nozzle 200. In some examples, the entire nozzle 200 is movable. It should be understood that any other suitable mechanism for redirecting the airflow can be used to achieve the same effect.

[0106] In this example, the fan 10 is a room fan or a desk fan. The flow rate of the air flow through the fan 10 is between 10 and 100 l / s, although any suitable flow rate can be used in other examples. In some examples, higher flow rates provide more intense jets and / or longer potential cores, for example for delivering higher volumes of conditioned air. In one embodiment, the flow rate is between 10 l / s and 40 l / s, for example between 20 l / s and 30 l / s, for example about 25 l / s. A flow rate between 10 l / s and 40 l / s can provide a suitable flow rate while being more comfortable for the user, having a lower noise signature, allowing a smaller diameter air outlet 230, and / or reducing interference with the ambient air, for example reducing interference with objects (e.g., paper) in the room or near the user.

[0107] The frequency of the axial disturbances required to generate the annular vortices 350a, 350b depends on the velocity of the airflow discharged through the air outlet 230 and the diameter of the air outlet 230. This relationship is expressed in terms of the so-called axial Strouhal number, which is defined as St a =f0d / U0, where f0 is the axial perturbation frequency, d is the diameter of the air outlet 230, and U0 is the average velocity of the air flow discharged through the air outlet 230. The velocity U0 can be obtained by considering the flow rate and the cross-sectional area of ​​the air outlet 230. In this example, the axial Strouhal number is between 0.4 and 0.65, for example, 0.5. In some examples, a Strouhal number between 0.4 and 0.55, for example, a Strouhal number between 0.45 and 0.5, causes the jet 300 to split into well-defined bifurcated jets 330a, 330b in a bifurcating and precessing operating mode. In some examples, a Strouhal number between 0.55 and 0.65, for example, 0.6, causes the jet 300 to expand in one or more radial directions, or to be effectively mixed, or to form less well-defined bifurcated jets 330a, 330b. In some examples, the Strouhal number is variable, such as by varying the axial perturbation frequency, to provide a user with flexibility in the form of the jets 330a, 330b ejected from the nozzle 200.

[0108] In the present example, the diameter of the air outlet 230 is selected to allow axial and radial disturbance frequencies to be less than 60 Hz for a given flow rate or velocity of the airflow through the air outlet 230. For example, for a given air flow rate, the diameter can be selected to provide sub-audible axial disturbance frequencies, for example frequencies below 30 Hz. By way of example only, with a Strouhal number of 0.4 and requiring an axial forcing frequency of less than 60 Hz, the minimum diameter of the air outlet 230 (which can be referred to herein as the "nozzle diameter") is: 44 mm for a flow rate of 10 l / s; 60 mm for a flow rate of 25 l / s; 76 mm for a flow rate of 50 l / s; 95 mm for a flow rate of 100 l / s.

[0109] For a given Strouhal number, a larger diameter air outlet 230 requires a lower axial disturbance frequency to produce suitable annular vortices 350a, 350b. In this way, in some examples, an upper limit on the diameter of the air outlet 230 is set by design constraints. In other examples, the axial disturbance frequency is greater than 10 Hz, such that the resulting annular vortices 350a, 350b are less easily perceptible to a user. By way of further illustration, with a Strouhal number of 0.65 and requiring an axial disturbance frequency of greater than 10 Hz, the maximum nozzle diameter is: 93 mm for a flow rate of 10 l / s; 127 mm for a flow rate of 25 l / s; 160 mm for a flow rate of 50 l / s; 202 mm for a flow rate of 100 l / s. In this way, in some examples, the diameter of the air outlet 230 is between 45 and 200 mm, the axial disturbance frequency is between 10 Hz and 60 Hz, and the air flow rate is between 10 l / s and 100 l / s, such that the Strouhal number is between 0.4 and 0.65.

[0110] In some examples, the axial disturbance device 400 is configured to impart a velocity disturbance having a peak-to-peak (p-p) amplitude that is greater than 1% of the velocity of the airflow at the air outlet 230. In some examples, the p-p velocity disturbance amplitude is between 1% and 50% of the velocity of the airflow at the air outlet 230, although in other examples the amplitude is 50% or greater than 50% of the velocity of the airflow at the air outlet 230. The velocity at the air outlet 230 can be the instantaneous velocity at a location in the air outlet 230, and / or the time-averaged and / or spatially-averaged velocity at the air outlet 230.

[0111] In some examples, the radial perturbation device 500 is configured to oscillate the air outlet at a p-p amplitude greater than 1% of the nozzle diameter. In some examples, the radial perturbation device 500 oscillates the air outlet at a p-p amplitude between 1% and 10% of the diameter of the air outlet 230. In other examples, the radial perturbation device 500 oscillates the air outlet 230 at a p-p amplitude of 10% or greater than 10% of the diameter of the air outlet 230.

[0112] In some examples, the fan 10 includes a controller (not shown) for controlling operation of the fan 10. The controller controls any one or more of: the flow rate of air supplied to and / or expelled through the air outlet 230; the axial perturbation frequency; the axial perturbation amplitude; the radial perturbation frequency; and the radial perturbation amplitude. The controller controls the aforementioned parameters in response to user input, for example in response to a user selecting one of the modes described above, and / or in response to a specific user request, for example requiring the fan 10 to produce a well-defined bifurcated jet at a high flow rate. In some examples, the fan 10 includes physical controls for user input to the controller. In other examples, the controller receives commands or requests from the user remotely, for example through a remote control, or through a mobile application via an established communication network, for example a 3G, 4G, 5G, Wifi and / or Bluetooth connection. It will be appreciated that in examples the controller can be configured to provide any of the functionality and variability described above in response to user requests.

[0113] It will be appreciated that any feature described in relation to any one example can be used alone, or in combination with other features described, and can also be used in combination with one or more features of any of the other examples, or any combination of any other examples. Furthermore, equivalents and modifications not described above can also be employed without departing from the scope of the application, which is defined in the claims below.

Claims

1. A fan comprising: a nozzle having an air outlet through which an air stream is discharged in an axial direction; an axial perturbation device for imparting velocity perturbations to the air stream in the axial direction at a first frequency; and a radial perturbation device for imparting velocity perturbations to the air stream in a plane orthogonal to the axial direction at a second frequency, wherein the fan is operable in: a first operating mode in which the axial perturbation device is inactive; and a second operating mode in which the axial perturbation device is active and imparts velocity perturbations to the air stream at the first frequency, wherein the axial perturbation device imparts sinusoidal velocity fluctuations to the air stream discharged through the air outlet. The ratio of the first frequency to the second frequency is greater than 1.

2. The fan of claim 1, wherein, The ratio of the first frequency to the second frequency is not greater than 4.

3. The fan of claim 1 or 2, wherein, The fan is operable in:

4. The fan of claim 1 or 2, wherein, a first operating mode in which the axial perturbation device and the radial perturbation device are inactive; a second operating mode in which the axial perturbation device is active and imparts velocity perturbations to the air stream at the first frequency, and the radial perturbation device is inactive; and a third operating mode in which the axial perturbation device is active and imparts velocity perturbations to the air stream at the first frequency, and the radial perturbation device is active and imparts velocity perturbations to the air stream at the second frequency. The fan is operable in a fourth operating mode in which the radial perturbation device imparts velocity perturbations to the air stream at a third frequency, and the third frequency is different to the second frequency. The second frequency and the third frequency are selected so that the air stream discharged from the nozzle diverges in the third operating mode and expands in the fourth operating mode.

5. The fan of claim 4, wherein, The ratio of the first frequency to the second frequency is 2.0, and the ratio of the first frequency to the third frequency is 2.

5.

6. The fan of claim 5, wherein, The radial perturbation device comprises an actuator configured to oscillate the air outlet at the second frequency.

7. The fan of claim 5 wherein, The actuator oscillates the air outlet at a peak-to-peak amplitude greater than 1% of the diameter of the nozzle.

8. The fan of claim 1 or 2, wherein, The axial perturbation device is an acoustic perturbation device.

9. The fan of claim 8, wherein, The velocity perturbations imparted by the axial perturbation device have a peak-to-peak amplitude greater than 1% of the velocity of the air stream at the air outlet.

10. The fan of claim 1 or 2, wherein, The air stream is discharged at a flow rate between 10 l / s and 100 l / s.

11. The fan of claim 1 or 2, wherein, The diameter of the air outlet is between 45 mm and 200 mm.

12. The fan of claim 1 or 2, wherein, The first frequency is less than 60 Hz.

13. The fan of claim 1 or 2, wherein, 15. The fan of claim 1 or 2, comprising flow conditioning means for conditioning the velocity profile of the air stream delivered to and / or discharged from the nozzle.

14. The fan of claim 1 or 2, wherein, 16. The fan of claim 1 or 2, comprising flow direction means for controlling the direction of the air stream discharged from the nozzle. The flow direction means comprises one or more guide vanes. The fan is a room fan.

17. The fan of claim 16, wherein, ​ 18. The fan of claim 1 or 2, wherein, ​

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