Air management device

Abstract

An environmental air management device 100 (such as a fan, air purifier, humidifier, dehumidifier, air conditioner or heater) comprises an airflow generator (such as a fan) within a housing 102 having

Description

BACKGROUND A conventional domestic fan typically includes a set of blades mounted for rotation about an axis, and a drive apparatus for rotating the set of blades to generate an airflow. SUMMARY An aspect of the present invention provides an environmental air management device, comprising: (i) a housing comprising an air inlet through which air is drawn into the device, (ii) an airflow generation unit configured to move the air at least partially through the housing, (iii) an air entrainment assembly, comprising: (a) an airflow director, the airflow director delimiting a through hole, the through hole defining an air outlet at an end of the airflow director through which the air flows out of the device, and (b) a collar having a first end and a second end, the collar extending at least partially around the airflow director. The first end of the collar is arranged closer to the air outlet than the second end. A perimeter of the air outlet has a greater length than a perimeter of the first end, thereby defining one or more airflow channels extending at least partially along the collar and between the collar and the airflow director. In use, ambient air is drawn at least partially along (or across) the one or more airflow channels and out of the first end of the collar. The ambient air that is drawn along (or across) the one or more airflow channels is entrained and accelerated by the airflow from the air outlet (referred to herein as the primary airflow). The environmental air management device (which may be alternatively known as an airflow assembly, a fan, an air purifier, a humidifier, a dehumidifier, an air conditioner, or a heater) can provide advantages over conventional environmental air management devices. For example, the geometry interacts with the ambient air, manipulating the path of entrained air such that there may be an increase in the primary flow rate for a given sound power level. The presence of the collar manipulates the entrained airflow to increase the discharge coefficient of the air outlet. Reference to the discharge coefficient herein describes the restriction of a component, and a higher discharge coefficient means less restriction. One way in which the discharge coefficient is increased by the collar is by creating a cone of accelerated air around the primary airflow. The cone of entrained air may therefore extend around the primary airflow, where the entrained airflow moves slower than the faster moving primary airflow in the centre. This may act as a diffuser for the primary airflow, reducing the overall restriction of the system. The device may therefore diffuse the primary flow using the entrained airflow to increase the static pressure at a plane at the air outlet. Because of the increased discharge coefficient, the environmental air management device may also improve energy efficiency compared to an environmental air management device without the collar, for example. In examples where the device can purify air, the device can also purify a room quicker. The increased purification speed may be because the product can be run at a higher flow rate for the same sound power level. A higher flow rate of purified air will clean a room more quickly. In examples, the second end of the collar is arranged upstream of the airflow that is flowing through, or out of, the device. Put another way, the second end may be arranged upstream of the airflow flowing out of the air outlet (i.e., the primary airflow). The second end of the collar may therefore be arranged upstream of the first end of the collar. The second end may be arranged closer to the airflow generator than the first end. In examples, the collar is ring-shaped (so the perimeters at the first and second ends are circular). In other examples, the perimeters at the first and second ends may have any shape and may be the same shape or a different shape. In examples, the airflow director is tubular such that the through hole forms a channel. The air outlet is therefore at an end of the channel. In an example, a cross-sectional area of the collar at the second end is greater than a cross-sectional area of the collar at the first end (such that the collar flares outwards towards the second end). The air flowing out of the air outlet (and through the through hole) is the air from the airflow generation unit (rather than the ambient air), so may be referred to as a primary airflow. In examples, the airflow generation unit is arranged within the housing. In examples, the airflow generation unit comprises an impeller to draw air into the housing and move the air out of the air outlet. In examples, the airflow generation unit comprises a compressor. The compressor may comprise, in some examples, a motor, impeller and stator assembly. In a particular example, there are a plurality of airflow channels, and the airflow channels are distributed, such as equally distributed, around the airflow director. The sides of the airflow channels may be defined by the inner surface of the collar and the outer surface of the airflow director. In other examples, the airflow channels may be defined by other surfaces, such as one or more tubular structures arranged between the collar and the airflow director. In examples, the airflow channels are separate from each other, such that air flowing along one airflow channel cannot pass into another airflow channel. In a particular example, the airflow director is coupled to or abuts the collar at the first end. In other cases, the airflow channels may be connected, rather than being entirely separated from each other. In examples, the collar has a length measured between the first and second ends, wherein the collar is arranged relative to the air outlet such that at least 50% of the length of the collar is upstream of the air outlet, relative to the air flowing out of the air outlet. This configuration means that a high proportion of the collar is arranged closer to the airflow generation unit, which ensures efficient use of material and minimises the device height, while manipulating the airflow to increase the discharge coefficient and provide acoustic attenuation. The length of the collar may be measured along an axis that is perpendicular to a plane defined by the air outlet. The length may be measured along an average airflow path. The length may be the average length of the collar. In a particular example, the collar is arranged relative to the air outlet such that at least 80% of the length of the collar is upstream of the air outlet. In another example, the collar is arranged relative to the air outlet such that at least 90% of the length of the collar is upstream of the air outlet. Such a configuration may help increase the discharge coefficient of the outlet. In a further example, the collar is arranged relative to the air outlet such that at least 95% of the length of the collar is upstream of the air outlet. In a particular example, the collar is arranged relative to the air outlet such that 100% of the length of the collar is upstream of the air outlet, relative to the air flowing out of the air outlet. The first end of the collar may therefore be flush / level with the air outlet, or the first end may be offset upstream of the air outlet. In one example, the first end of the collar is offset upstream of the air outlet by between 2mm and 7mm. In a particular example, the first end of the collar is offset upstream of the air outlet by around 5mm. Accordingly, in examples, there is a distance of 2mm to 7mm between the first end and the air outlet. The offset / distance is measured along an axis that is perpendicular to a plane defined by the air outlet, or along the average airflow path. Expressed differently, the first end of the collar may be offset upstream of the air outlet by between 0.003 times the perimeter of the collar at the first end and 0.011 times the perimeter of the collar at the first end, such as 0.0079 times the perimeter of the collar at the first end. In examples, the first end of the collar is flush with the air outlet. Having the first end flush with the air outlet has been found to provide the advantages described above, without having to increase the height profile of the device. Accordingly, in some examples, there is a 0mm offset between the first end and the air outlet, where the offset is measured along an axis that is perpendicular to a plane defined by the air outlet or along the average airflow path. In other examples, the first end of the collar is offset downstream of the air outlet. The first end of the collar may therefore extend “above” the air outlet. Extending the height of the collar above the air outlet has been found to further increase the flow rate of the airflow for a fixed RPM of the air generation unit (such as the impeller). The inventors have found that collars having a length longer than around 80mm can improve performance of the device. Expressed differently, the length may be longer than around 0.13 times the perimeter of the collar at the first end or greater than about 0.35 times a diameter of the collar at the first end. In particular, the inventors have found that the length of the collar can impact both the acoustic performance and the flow rate, even though the collar may not directly interact with the primary airflow from the air outlet. Accordingly, in examples, the collar has a length, measured between the first and second ends, of greater than about 80mm or greater than about 0.13 times the perimeter of the collar at the first end or greater than about 0.35 times a diameter of the collar at the first end. In particular examples, the length is between about 80mm and about 120mm or between about 0.13 and 0.19 times the perimeter of the collar at the first end or between about 0.35 and 0.52 times the diameter of the collar at the first end. Lengths within this range can provide a balance between providing the above-mentioned advantages, while also maintaining a compact device. In examples, the air outlet has an area, Ai, the one or more airflow channels have a combined area, A2, the combined area being defined at a plane arranged at the air outlet, and an exit area ratio, Aexit, which is greater than or equal to about 0.275 and less than about 1, where Aexit = Al I (Al + A2). Aexit therefore describes the ratio of how much space at a plane defined by the air outlet is available for the primary flow relative to that of the total area within the collar. Keeping Aexit between 0.275 and 1 offers a performance improvement. If Aexit is too low (<0.275) it can mean that the area available for the primary flow is reduced, and this restriction will require the air generation unit to be increased in power, making the product louder. Aexit will also have an impact on the attenuation of the noise. A low Aexit means that a larger ratio of the exit area is blocked, providing attenuation to the noise sources inside the product. The inventors have found that an Aexit within this range provides a balance between the above considerations. The inventors have found that an Aexit greater than 0.275 provides a performance improvement, where the performance is defined as the primary airflow rate while running the product at 60 dB(A) ref 20 pPa. The performance improvement is measured relative to an identical device that does not include the air entrainment assembly. In examples, both devices being compared include a cone, which is discussed below. Ai is a cross-sectional area of the air outlet (i.e., the area through which the air flows). A2 is defined at a plane arranged at the air outlet that is within the collar, but without the air outlet area, Ai. In the case that the first end of the collar is offset from the plane, A2 should be taken at the plane of the air outlet with the dimensions of the collar projected onto the plane of the air outlet. A2 is the combined cross-sectional area of the airflow channels (i.e., the area through which the ambient air flows). In examples, Aexit is between about 0.3 and about 0.5. In other examples, Aexit is between about 0.4 and about 0.45, such as about 0.42. As set out above, Aexit may be less than 1. As an example, if A2= 0, Aexit = 1 (this may be the case if the air outlet was circular and occupies all of the space within the collar). As Aexit gets closer to 1, A2 approaches 0. As such, Aexit must be less than 1. As Aexit tends towards 1, A2 tends towards 0. Aexit being less than 1 means that A2 cannot be zero (i.e., there must be some entrainment area). In examples, a perimeter ratio, P, is greater than about 1 and less than or equal to about 2.15, where P = P1 / P2, Pi is the perimeter of the air outlet, and P2 is the perimeter of the first end of the collar. P therefore determines the spatial rate of mixing and affects the rate of entrainment at the air outlet. A high P means that the primary airflow has a large shearing perimeter and has high potential to entrain air. P must be chosen such that there is sufficient shearing distance to entrain air. This can be paired with an Aexit that balances the area available for entrained air with the restriction and exit velocity of the primary airflow. In examples, P is between about 1.8 and about 2.1. In other examples, P is between about 1.8 and about 1.9, such as about 1.82. In examples, an entrainment entrance area, A3, is defined between the collar and the airflow director, the entrainment entrance area being a minimum cross-sectional area between the collar and the airflow director that the ambient air is drawn through (the ambient air forms the entrained air once drawn through the airflow channel(s) and entrained by the primary airflow). An air entrainment area ratio, Aentrainment, is greater than or equal to about 0 and less than or equal to about 0.5, where Aentrainment = A3 / A2. Aentrainment describes the ratio of the entrance area for entrained air to the exit area for the entrained air. This defines the potential for entrained flow to be pulled inside the collar. The range includes 0 because it is possible to have no entrance area (i.e., A3 = 0, such as when the second end of the collar is closed) and the design will still provide useful benefits because the collar can still manipulate the entrained air in a useful way. The upper limit of 0.5 has been found empirically to provide substantially no performance improvements by the inventors. A3 is measured on a plane that is perpendicular to an airflow surface (such as the inner surface) of the collar. As mentioned, the minimum area between the collar and the airflow director must be used. This may be where the spacing between the collar and airflow director is narrowest. A3 is therefore the minimum cross-sectional area that the entrained flow must pass through as it enters the collar. A3 extends around the airflow director. A3 must also include all of the entrained flow entering upstream of the outlet plane. If the collar is perforated (such as having one or more air inlets formed along the collar), then A3 should also include the area of the perforations downstream of the measurement plane. In examples, Aentrainment is between about 0.1 and about 0.3. In other examples, Aentrainment is between about 0.1 and about 0.2, such as about 0.15. In examples, A2 cannot be zero (i.e., there must be some entrainment area). In examples, the environmental air management device further comprises a cone arranged at least partially within the through hole of the airflow director. A cone can help smooth the flow of the air that exits the air outlet. In examples, an apex of the cone is arranged upstream of the air outlet, relative to the air flowing out of the air outlet. The inventors have found that having the apex positioned upstream of the air outlet can protect the airflow generation unit, such as the compressor, during drop. In one example, a distance between the apex and a plane defined by the air outlet, as measured along an axis that is perpendicular to the plane defined by the air outlet, is about 12 mm. In examples, an apex of the cone is arranged relative to the air outlet such that a distance between the apex and a plane defined by the air outlet, as measured along an axis that is perpendicular to the plane defined by the air outlet, is between about -5mm and about +12 mm. A negative value means the distance is measured in the downstream direction, whereas a positive distance means the distance is measured in the upstream direction. Positioning the apex higher up (closer to, or in the downstream direction) has the advantage of reducing swirl in the airflow and straightening the flow. Positioning the apex lower down (in the upstream direction) may make the outlet less restrictive (if Ai stays constant). In examples, the collar and airflow director are configured such that the ambient air is drawn through the second end of the collar, along the one or more airflow channels and out of the first end of the collar. Having the second end of the collar open to allow the ambient air to flow into the collar and along the length of the collar allows the airflow to be directed relative to the airflow out of the air outlet such that the discharge coefficient is increased. The airflow channel(s) are therefore open at both ends of the channel(s). In examples, a gap is defined between the collar and the airflow director at the second end. In some cases, the collar additionally or alternatively comprises one or more air inlets formed along the collar, and ambient air is drawn through the one or more air inlets. In examples, a majority (or all) of the inlets are closer to the second end than the first end. In alternative examples, the second end of the collar is closed, such that the ambient air is drawn through the first end of the collar, at least partially along or across the one or more airflow channels and out of the first end of the collar. In examples, the perimeter of the air outlet is substantially star shaped. The air outlet may therefore be star shaped. A star shape, especially when coupled with a collar that is circular shaped, has been found to provide a particularly effective mechanism for entraining air into the primary airflow. A star shape comprises a plurality of arms, lobes, protrusions or points that form the star shape. Accordingly, in examples, the air outlet comprises a plurality of arms forming the star shape of the air outlet. In examples, the air outlet comprises between about 6 and about 10 arms forming the star shape of the air outlet. In a particular example, the air outlet comprises 8 arms forming the star shape. In examples, the air outlet comprises a plurality of arms forming the star shape of the air outlet, an airflow channel is defined between each adjacent arm of the plurality of arms, thereby forming a plurality of airflow channels extending at least partially along the collar and between the collar and the airflow director, and a first subset of the plurality of airflow channels have a first radial width, and a second subset of the plurality of airflow channels have a second radial width, the second radial width being greater than the first radial width. Accordingly, the two sides of each arm may have different radial lengths. The inventors have found that different, such as alternating, widths of channels provides an improvement in performance of the device. In examples, there are an equal number of channels in the first subset and the second subset, such as four channels in each subset. The radial width is measured radially from the collar and towards a centre of the air outlet, and is measured parallel to (i.e., along) a plane defined by the air outlet. In examples, the channels having the different radial widths are arranged to alternate in size around the collar. In examples, the perimeter of the first end of the collar is substantially circular. Additionally, or alternatively, a perimeter of the second end of the collar is substantially circular. In examples, the environmental air management device further comprises an air treatment unit configured to adjust one or more characteristics of the air that is drawn into the device. In examples, the one or more characteristics may be one or more of: an air purification (e.g., an air quality level), a temperature (heating or cooling), a velocity, and a humidity. In examples, the environmental air management device is a freestanding environmental air management device. For example, the device may be configured to be placed on a floor, worktop, etc, during normal use. In examples, the environmental air management device is a floor-standing environmental air management device. For example, the device may be configured to be placed on a floor during normal use. In examples, the environmental air management device is at least one of: an air purifier, a fan, an air conditioner, a humidifier, a dehumidifier, an air heater, and an air cooler. In the above examples, the perimeter of the air outlet has a greater length than a perimeter of the first end. In other examples, the perimeters may have the same length. In further examples, the perimeter of the air outlet has a shorter length than a perimeter of the first end. This may be the case where the perimeter of the collar at the first and / or second ends may have the same shape as the perimeter of the air outlet. Accordingly, a further aspect of the invention provides an environmental air management device, comprising: (i) a housing comprising an air inlet through which air is drawn into the device, (ii) an airflow generation unit configured to move the air at least partially through the housing, (iii) an air entrainment assembly, comprising: (a) an airflow director, the airflow director delimiting a through hole, the through hole defining an air outlet at an end of the airflow director through which the air flows out of the device, and (b) a collar having a first end and a second end, the collar extending at least partially around the airflow director. The first end of the collar is arranged closer to the air outlet than the second end. A perimeter of the first end has an equal or a greater length than a perimeter of the air outlet, thereby defining one or more airflow channels extending at least partially along the collar and between the collar and the airflow director. In use, ambient air is drawn at least partially along or across the one or more airflow channels and out of the first end of the collar. In examples, the perimeter ratio, P, is greater than about 0 and less than about 1, where P = P1 / P2, Pi is the perimeter of the air outlet, and P2 is the perimeter of the first end of the collar. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a perspective view of an environmental air management device 100 according to an example; Figure 2 is a side view of the device of Figure 1; Figure 3 is a perspective view of the device of Figure 1 with the collar removed; Figure 4 is a perspective view of the collar in isolation; Figure 5 is a top-down view of the device of Figure 1; Figure 6 is a side view cross-section of the air entrainment assembly; Figure 7 is a perspective view cross-section of the air entrainment assembly; Figure 8 shows the velocity of the airflow when the collar is and is not present; Figure 9 is a side view of another example device; Figure 10 is a schematic drawing of different areas and perimeter lengths on the device; and Figure 11 shows two perspective views of two alternative the air entrainment assemblies. DETAILED DESCRIPTION Figures 1 and 2 depict an environmental air management device 100 according to an example. In this example, the device 100 is an air purifier, and is primarily designed to stand on a floor or tabletop within a room or other environment during normal use. Figure 1 shows a perspective view of the device 100, and Figure 2 shows a side view of the device 100. The device 100 comprises a housing 102 (also known as a body 102) and the housing 102 comprises an air inlet 104 through which air can be drawn into the device 100 during operation. In this example, the air inlet 104 comprises a plurality of inlet openings in the form of apertures or holes formed in the housing 102. An airflow generation unit (the location of which is identified by a dashed outline 144 in Figure 2), which can include an impeller, causes air from the room / environment to be drawn into the housing 102 via the air inlet 104. The airflow generation unit can therefore move air through the housing 102. In examples, the device 100 further comprises an air treatment unit configured to adjust one or more characteristics of the air that is drawn into the device. In examples, the one or more characteristics may be one or more of: an air purification (e.g., an air quality level), a temperature (heating or cooling), a velocity, and a humidity. In the present example, the air treatment unit forms a part of the airflow generation unit 144, but in other examples, they may be separate. The device 100 further comprises an air entrainment assembly 106, which comprises an airflow director 108, and a collar 110. The airflow director 108 delimits a through hole through which air flows, and the through hole defines an air outlet 112 at an end (in this case top end) of the airflow director 108. The air drawn into the housing 102 therefore passes through the housing, along the airflow director 108 and out of the air outlet 112, such as along the general direction of the dashed arrow PA. The airflow that is drawn into the housing 102 via the air inlet 104 and that exits the air outlet 112 is referred to herein as the primary airflow (PA). In this example, a perimeter of the air outlet 112 is substantially star shaped. The air outlet 112 of this example has 8 arms forming the star shape. The collar 110 is ring-shaped and extends around the airflow director 108. Figure 3 shows a perspective view of the device 100 with the collar 110 removed. Figure 4 shows a perspective view of the collar 110 in isolation. The collar 110 has a first end 110a (also known as a top end) and a second end 110b (also known as a bottom end). The collar 110 has a length, L, extending between the first and second ends 110a, 110b, as seen in Figure 2. As shown, the first end 110a of the collar 110 is arranged closer to the air outlet 112 than the second end 110b. As will be discussed later, in this example, a gap or spacing exists between the collar 110 and the airflow director 108 at the second end 110b. The second end 110b of the collar 110 is arranged upstream of the air outlet 112 relative to the primary airflow PA that is flowing out of the air outlet 112. In this example, a perimeter of the collar 110 at the first end 110a is substantially circular. As shown in Figure 4, the perimeter of the collar 110 at the second end 110b is substantially circular, and is also larger than the perimeter at the first end 110b. The collar 110 is therefore wider at the second end 110b, and therefore flares outwards towards the second end 110b. In addition to the air outlet 112 being star shaped and the collar 110 being circular, the perimeter of the air outlet 112 has a greater length than the perimeter of the first end 110a, and as such, a plurality of airflow channels 114 are formed between the collar 110 and the airflow director 108. Each airflow channel 114 extends at least partially along an inner surface of the collar 110 and an outer surface of the airflow director 108. Each airflow channel 114 is defined between each pair of arms forming the star shape of the air outlet 112. Accordingly, in this example, there are 8 airflow channels 114. The plurality of airflow channels 114 are distributed around the air outlet 112. Figure 5 shows a top-down view of the device 100, and in particular, the air entrainment assembly 106. The airflow channels 114 extend generally in a direction that is out of the page. The presence of such airflow channels 114 means that ambient air can be drawn along (or across) the airflow channels 114 when the primary airflow PA is flowing out of the air outlet 112. In this example, where the first and second ends 110a, 110b of the collar 110 are “open”, ambient air is drawn into the airflow channels 114 from the second end 110b, along the inside of the collar 110 and out of the first end of the collar 110a. The ambient airflow is shown by arrows AA in Figure 2. The ambient airflow AA may alternatively be referred to as the entrained airflow. The gap / spacing between the inner surface of the collar 110 and the outer surface of the airflow director 108 at the second end 110b means that the second end 110b of the collar 110 is open to allow ambient air to flow into the airflow channels 114. Figure 6 shows a side view cross-section of the air entrainment assembly 106, where the gap between the airflow director 108 and the collar 110 (at the second end 110b) is more clearly visible. Figure 7 shows aperspective view cross-section of the air entrainment assembly 106. As shown most clearly in Figure 6, the through hole of the airflow director 108 has a cross-sectional width that increases further away from the air outlet 112 (i.e., “upstream” of the air outlet 112 and in the downwards direction away from the air outlet 112 in Figure 6). In some cases, the collar 110 additionally or alternatively comprises one or more air inlets formed through the collar 110, and ambient air is drawn through the one or more air inlets and into the airflow channels 114. For example, rather than or as well as drawing ambient air into the airflow channels 114 via the open second end 110b, the air may be drawn into the airflow channels 114 via the air inlets formed through the collar 110 (an example of such an arrangement is shown in Figure 11). As shown in Figure 8, the presence of the collar 110 manipulates the ambient airflow AA to form a ‘cone’ of accelerated air around the primary airflow PA, which reduces losses caused by expanding the airflow into the room / environment. Figure 8 shows the velocity of the airflow when the collar is not present (in the left image in Figure 8) and when the collar is present (in the right image in Figure 8). As discussed, by surrounding the primary airflow PA that flows out of the air outlet 112 with the ambient airflow AA, the flow rate of the primary airflow PA can be increased for a given sound power level of the device 100. The use of the collar 110 therefore helps reduce the sound power level of the device 110. The device 100 therefore allows the flow rate to be increased while maintaining a given sound power level, or alternatively allows the sound power level to be decreased while maintaining a given flow rate. The inventors performed a series of experiments that measured the power level (SWL) for 2 RPMs of the device 100 with and without the collar 110. This was performed for different flow rates. The inventors found that for all flow rates tested, the sound power level for a given flow rate was reduced. As discussed, the air outlet 112 has a star shape formed by a number of “arms” on the star. In some examples, the arms extend in length to the inner surface of the collar 110, thereby separating each of the airflow channels 114 from each other. As shown most clearly in Figure 5, although the arms each have the same radial length RI measured from the centre C of the air outlet, the two sides of each arm may have different radial lengths R2, R3, where the first side of a particular arm has a length R2 and the second side of the particular arm has a length R3, where R2 is greater than R3. When each arm of the plurality of arms has the same form, the difference in lengths results in adjacent airflow channels 114 having different radial widths (and different cross-sectional areas). As such, of the plurality of airflow channels 114, a first subset of the plurality of airflow channels have a first radial width R4, and a second subset of the plurality of airflow channels have a second radial width R5, the second radial width R5 being greater than the first radial width R4. For example, the first subset may include airflow channels 114a, and the second subset may include airflow channels 114b. In this example, there are 4 channels within each subset. The airflow channels 114 therefore alternate in size around the centre C. The radial widths of the channels 114 are measured radially from an inner surface of the collar 110 and towards the centre C of the air outlet 112, and parallel to (i.e., along) a plane 118 (see Figure 2) defined by the air outlet 112. In Figure 5, the plane of the air outlet 112 lies within the plane of the page. As mentioned, the collar 110 has a length L measured between the first and second ends 110a, 110b. As shown in Figure 2, the collar 110 is arranged relative to the air outlet 112 such that 100% of the length L of the collar 110 is upstream of the air outlet 112, relative to the primary airflow PA passing out of the air outlet 112. The length of the collar 110 is measured along an axis 116 that is perpendicular to a plane 118 defined by the air outlet 112. The first end 110a of the collar 110 is therefore offset upstream of the air outlet 112, such that the air outlet 112 is arranged above the first end 110a of the collar 110, as shown in Figure 2. In other examples, however, at least 50% of the length L of the collar 110 is upstream of the air outlet 112. In this example, there is a distance, D, of around 5mm between the first end 110a and the air outlet 112, where the offset / distance is measured along the axis 116. In other examples, the first end 110a may be offset downstream of the air outlet 112, as in the example device 100 shown in Figure 9, or the first end 110a and the air outlet 112 may be flush / level with each other. As discussed, the inventors have found that collars 110 having a length L longer than around 80mm can improve performance of the device 100. To determine this, the inventors performed a series of experiments that determined how the primary flow rate of the primary airflow PA changes based on the length L of the collar 110 (compared to a device 100 with no collar 110). In this experiment, for each different length collar 110, the first end 110a remained at a constant distance D from the air outlet 112 for each test. The inventors found that, in general, a longer length L offers improved performance (i.e., a greater change / increase in primary flow rate). It was found that at lengths below 80mm, there was no performance increase, for this particular experiment. As visible throughout the Figures, the device 100 further comprises a cone 120 arranged at least partially within the through hole of the airflow director 108. A cone 120 helps smooth the flow of the primary airflow PA. As seen in Figures 1-3 in particular, the apex 120a of the cone 120 is arranged upstream of the air outlet 112, relative to the air flowing out of the air outlet 112, and upstream of the first end 110a of the collar 110, relative to the air flowing out of the air outlet 112. In a variation, such as that shown in Figure 9, the apex 120a may be arranged downstream of the first end 110a and downstream of the air outlet 112. As shown in Figure 10, the air outlet 112 has an area, Ai, such as a cross-sectional area, defined at the plane 118 arranged at the air outlet 112. The primary airflow PA therefore flows through this area. The airflow channels 114 have a combined / summed area, A2, such as a cross-sectional area. A2 is therefore the combined cross-sectional area of the airflow channels and the area through which the ambient airflow AA flows. The combined area A2 is defined at the plane 118. In examples where the first end 110a of the collar 110 is offset from the plane 118, A2 is taken at the plane 118 of the air outlet 112 with the dimensions of the collar 110 and airflow channels 114 projected onto the plane 118. In example devices 100 it is preferred that an exit area ratio, Aexit, is greater than or equal to about 0.275 and less than about 1, where Aexit = Ai / (Ai + A2). The exit area ratio Aexit therefore describes the ratio of how much space at the plane 118 is available for the primary flow relative to that of the total area within the collar 110. During testing, the inventors found that an exit area ratio greater than 0.275 provided a performance improvement, where the performance is defined as the primary airflow rate while running the product at 60 dB(A) ref 20 pPa. The performance improvement was measured relative to an identical device that does not include the air entrainment assembly. In examples, both devices being compared include a cone 120. As shown in Figure 10, the air outlet 112 has a perimeter Pi and the first end 110a of the collar 110 has a perimeter P2. In example devices 100 it is preferred that a perimeter ratio, P, is greater than about 1 and less than or equal to about 2.15, where P = P1 / P2. The perimeter ratio, P, determines the spatial rate of mixing and affects the rate of entrainment at the air outlet 112. During testing, the inventors found that a perimeter ratio, P of less than or equal to about 2.15 provided a performance improvement. As shown in Figure 10, an entrainment entrance area, A3, is defined between the collar 110 and the airflow director 108, where the entrainment entrance area is a minimum cross-sectional area between the collar 110 and the airflow director 108 that the ambient airflow AA flows through. A3 is measured on a plane that is perpendicular to an airflow surface (such as the inner surface) of the collar 110, as illustrated in the drawing on the left-hand side of Figure 11. As mentioned, the minimum area between the collar 110 and the airflow director 108 must be used. This may be where the spacing between the collar 110 and airflow director 108 is narrowest. A3 is therefore the minimum cross-sectional area that the entrained flow must pass through as it enters the collar, which in this example may be determined at point 134. A3 must also include all of the entrained flow entering upstream of the first end 110a. If the collar is perforated (such as having one or more air inlets formed along the collar, as shown in the drawing on the right-hand side of Figure 11), then A3 must also include the area of the perforations downstream of the measurement plane. Accordingly, as shown in Figure 11, the area A3 may be determined at point 134 (to ensure that the air inlets 136 are accounted for), whereas if the area A3 is determined at point 138, then the combined cross-sectional areas of the air inlets 136 must be added to the area A3 determined at point 136. In example devices 100 it is preferred that an air entrainment area ratio, Aentrainment, is greater than or equal to about 0 and less than or equal to about 0.5, where Aentrainment = A3 / A2. Aentrainment describes the ratio of the entrance area A3 for entrained air to the exit area A2 for the entrained air. This defines the potential for entrained flow to be pulled inside the collar 110. The range includes 0 because it is possible to have no entrance area (i.e., A3 = 0, such as when the second end 110b of the collar is closed). During testing, the inventors found that an air entrainment area ratio, Aentrainment, less than or equal to about 0.5 provided a performance improvement.

Claims

1. An environmental air management device, comprising:a housing comprising an air inlet through which air is drawn into the device;an airflow generation unit configured to move the air at least partially through the housing;an air entrainment assembly, comprising:an airflow director, the airflow director delimiting a through hole, the through hole defining an air outlet at an end of the airflow director through which the air flows out of the device; anda collar having a first end and a second end, the collar extending at least partially around the airflow director;wherein:the first end of the collar is arranged closer to the air outlet than the second end;a perimeter of the air outlet has a greater length than a perimeter of the first end, thereby defining one or more airflow channels extending at least partially along the collar and between the collar and the airflow director; andin use, ambient air is drawn at least partially along the one or more airflow channels and out of the first end of the collar.

2. An environmental air management device according to claim 1, wherein the collar has a length measured between the first and second ends, wherein the collar is arranged relative to the air outlet such that at least 50% of the length of the collar is upstream of the air outlet, relative to the air flowing out of the air outlet.

3. An environmental air management device according to claim 2, wherein the collar is arranged relative to the air outlet such that at least 90% of the length of the collar is upstream of the air outlet.

4. An environmental air management device according to claim 3, wherein:the collar is arranged relative to the air outlet such that 100% of the length of the collar is upstream of the air outlet, relative to the air flowing out of the air outlet.

5. An environmental air management device according to claim 3, wherein the first end of the collar is flush with the air outlet.

6. An environmental air management device according to claim 2 or 3, wherein the first end of the collar is offset downstream of the air outlet.

7. An environmental air management device according to any preceding claim, wherein the collar has a length, measured between the first and second ends, of greater than about 80mm or greater than about 0.13 times the perimeter of the collar at the first end or greater than about 0.35 times a diameter of the collar at the first end.

8. An environmental air management device according to claim 7, wherein the length is between about 80mm and about 120mm or between about 0.13 and 0.19 times the perimeter of the collar at the first end or between about 0.35 and 0.52 times the diameter of the collar at the first end.

9. An environmental air management device according to any preceding claim, wherein:the air outlet has an area, Ai;the one or more airflow channels have a combined area, A2, the combined area being defined at a plane arranged at the air outlet; andan exit area ratio, Aexit, which is greater than or equal to about 0.275 and less than about 1, where Aexit = Ai / (Ai + A2).

10. An environmental air management device according to claim 9, wherein Aexit is between about 0.3 and about 0.5.

11. An environmental air management device according to any preceding claim, wherein a perimeter ratio, P, is greater than about 1 and less than or equal to about 2.15, where P = P1 / P2, Pi is the perimeter of the air outlet, and P2 is the perimeter of the first end of the collar.

12. An environmental air management device according to claim 11, wherein P is between about 1.8 and about 2.1.

13. An environmental air management device according to any preceding claim, wherein:the one or more airflow channels have a combined area, A2, the combined area being defined at a plane arranged at the air outlet;an entrainment entrance area, A3, is defined between the collar and the airflow director, the entrainment entrance area being a minimum cross-sectional area between the collar and the airflow director that the ambient air flows through; andan air entrainment area ratio, Aentrainment, is greater than or equal to about 0 and less than or equal to about 0.5, where Aentrainment = A3 / A2.

14. An environmental air management device according to claim 13, wherein Aentrainment is between about 0.1 and about 0.3.

15. An environmental air management device according to any preceding claim, further comprising a cone arranged at least partially within the through hole of the airflow director.

16. An environmental air management device according to claim 15, wherein an apex of the cone is arranged upstream of the air outlet, relative to the air flowing out of the air outlet.

17. An environmental air management device according to claim 15 or 16, wherein an apex of the cone is arranged relative to the air outlet such that a distance between the apex and a plane defined by the air outlet, as measured along an axis that is perpendicular to the plane defined by the air outlet, is about 12 mm.

18. An environmental air management device according to any preceding claim, wherein the collar and airflow director are configured such that the ambient air is drawn through the second end of the collar, along the one or more airflow channels and out of the first end of the collar.

19. An environmental air management device according to any of claims 1 to 17, wherein the second end of the collar is closed, such that the ambient air is drawn through the first end of the collar, at least partially along the one or more airflow channels and out of the first end of the collar.

20. An environmental air management device according to any preceding claim, wherein the perimeter of the air outlet is substantially star shaped.

21. An environmental air management device according to claim 20, wherein the air outlet comprises between about 6 and about 10 arms forming the star shape of the air outlet.

22. An environmental air management device according to claim 20 or 21, wherein:the air outlet comprises a plurality of arms forming the star shape of the air outlet;an airflow channel is defined between each adjacent arm of the plurality of arms, thereby forming a plurality of airflow channels extending at least partially along the collar and between the collar and the airflow director; anda first subset of the plurality of airflow channels have a first radial width, and wherein a second subset of the plurality of airflow channels have a second radial width, the second radial width being greater than the first radial width.

23. An environmental air management device according to any preceding claim, wherein the perimeter of the first end of the collar is substantially circular.

24. An environmental air management device according to any preceding claim, further comprising an air treatment unit configured to adjust one or more characteristics of the air that is drawn into the device.

25. An environmental air management device according to any preceding claim, wherein the environmental air management device is a freestanding environmental air management device.

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