Patent Publication Number: US-2022211114-A1

Title: Electronic aerosol provision device

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a National Phase entry of PCT Application No. PCT/GB2020/050949, filed Apr. 14, 2020, which claim priority to GB 1905425.3, filed Apr. 17, 2019, the entire disclosures of which are incorporated herein by reference. 
    
    
     FIELD 
     The present disclosure relates to an electronic aerosol provision device. 
     BACKGROUND 
     A typical electronic aerosol provision device includes an internal air path which provides a channel between one or more inlets and one or more outlets. A user of the electronic aerosol provision device inhales on the air outlet(s) to create an airflow through the device along the channel from the air inlet(s) to the air outlet(s). 
     An electronic aerosol provision device generally also includes a source (precursor) material which is used for forming a vapor or aerosol. For example, some devices include a reservoir of liquid and a heater which is used to vaporize liquid from the reservoir. In other devices, a heater may be used to generate volatiles from a solid material, and these in turn form a vapor or liquid. In some cases, the liquid or solid material may be provided in a replaceable cartridge. The vapor or aerosol is usually generated in, or migrates into, the channel from the air inlet(s) to the air outlet(s), and is conveyed by the airflow along the channel and out through the air outlet(s) for inhalation by a user. 
     The user experience of such an electronic aerosol provision device is dependent upon the vapor or aerosol that exits the device for inhalation. 
     SUMMARY 
     The disclosure is defined in the appended claims. 
     The approach described herein provides an electronic aerosol provision system comprising an air pathway between an air inlet and an air outlet and a vaporizer for generating vapor into the air pathway. The air pathway between the air inlet and the vaporizer is configured to support laminar air flow. 
     The approach described herein provides an electronic aerosol provision system, comprising an air pathway between an air inlet and an air outlet, a vaporizer for generating vapor into the air pathway, and a facility for adjusting the air pathway to control turbulence within the air pathway. 
     It will be appreciated that features and aspects of the disclosure described above in relation to the first and other aspects of the disclosure are equally applicable to, and may be combined with, embodiments of the disclosure according to other aspects of the disclosure as appropriate, and not just in the specific combinations described above. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Various embodiments of the disclosure will now be described, by way of example only, with reference to the accompanying drawings, in which: 
         FIG. 1  shows an example electronic aerosol provision system. 
         FIG. 2  shows an electronic aerosol provision system having a linear airflow channel configured to support laminar airflow according to the approach described herein. 
         FIG. 3  shows distributions of aerosol particle sizes generated by an electronic aerosol provision system such as shown in  FIG. 1 . 
         FIG. 4  shows distributions of aerosol particle sizes generated by an electronic aerosol provision system such as shown in  FIG. 2 . 
         FIG. 5  shows an electronic aerosol provision system having a smoothly curved airflow channel configured to support laminar airflow according to the approach described herein. 
         FIG. 6  shows an electronic aerosol provision system having a facility for adjusting the air pathway to control turbulence according to the approach described herein. 
         FIG. 7  shows another electronic aerosol provision system having a facility for adjusting the air pathway to control turbulence according to the approach described herein. 
     
    
    
     DETAILED DESCRIPTION 
     Aspects and features of various examples are described herein. Some of these aspects and features may be implemented conventionally and these may not be described in detail in the interests of brevity. It will be appreciated that such aspects and features which are not described in detail may be implemented in accordance with suitable conventional techniques. 
     The present disclosure relates to electronic aerosol provision systems, which may also be referred to as electronic vapor provision systems, e-cigarettes, and so on. In the following description, the terms “e-cigarette”, “electronic cigarette”, “electronic aerosol provision system” and “electronic vapor provision system” may be used interchangeably unless the context demands otherwise. Likewise the terms “device” and “system” may be used interchangeably, for example, an “electronic aerosol provision system” should be regarded as the same as an “electronic aerosol provision device”, unless the context demands otherwise. Furthermore, as is common in this technical field, the terms “vapor” and “aerosol”, and related terms such as “vaporize”, “aerosolise”, and “volatilize”, may likewise be used interchangeably unless the context demands otherwise. 
     Such electronic aerosol provision systems/devices are often provided in modular form, for example, comprising a control unit and a cartomizer (the latter being a combination of a cartridge and a vaporizer). The term electronic aerosol provision system/device is used herein to denote one or more modules (such as the control unit) that act (comprise components) to generate an aerosol or vapor. Such a system/device may be configured to receive one or more additional modules, for example, a module (cartridge) containing liquid or other precursor to be vaporized, or may be provided in combination with one or more additional modules. 
     One common configuration for an electronic aerosol provision system/device having a modular assembly is to comprise a reusable part (the main control unit) and a replaceable (disposable) cartridge part, also referred to as a consumable. The replaceable cartridge part often contains the vapor (aerosol) precursor material and may (in some implementations) also contain a vaporizer (aerosolizer) to form a cartomizer. The reusable part often contains a power supply, for example, a rechargeable battery, and control circuitry for the device/system. These parts may contain further components depending on functionality. For example, the reusable part may contain a user interface for receiving user input and displaying operating status characteristics, while the replaceable cartridge part may contain a temperature sensor for helping to control the temperature of the vaporizer. 
     A cartridge part is usually electrically and mechanically coupled to a control unit for use. When the vapor precursor material in a cartridge is exhausted (fully consumed), or the user wishes to switch to a different cartridge having (for example) a different vapor precursor material, the cartridge may be removed from the control unit and a replacement cartridge provided in its place. Devices conforming to this type of two-part modular configuration are sometimes referred to as two-part devices. 
     Some of the example devices/systems described herein are based on an elongated two-part device/system that utilises disposable cartridges. However, it will be appreciated that the approach described herein may also be adopted for different configurations of an electronic aerosol provision system/device, for example, single-part devices or modular devices comprising more than two parts, refillable devices and single-use disposable devices. In addition, the approach described herein may be applied to devices/systems having other geometries (not necessarily elongate), for example, based on so-called box-mod high performance devices that typically have more of a box-like shape. 
       FIG. 1  is a schematic cross-sectional representation of a first electronic aerosol provision device  20 . The e-cigarette  20  comprises two main sections, namely a control section  22  and a cartridge section  24 . In some implementations, the cartridge section and the control section are separate parts which can be detached from one another. In normal use, the control part  22  and the cartridge part  24  are releasably coupled together at an interface  26 . When the cartridge part  24  is exhausted (after depletion of an aerosol precursor material therein), or the user wishes to switch to a different cartridge, the cartridge  24  may be detached from the control part  22 . The detached cartridge may then be disposed of (if fully depleted) and a replacement cartridge coupled to the control part. Another possibility is that the same cartridge part  24  may be refilled and re-attached to the control part  22 . In other implementations, the cartridge part  24  might be refillable in situ, i.e. while still attached to the control part  22  (in which case the cartridge section  24  might potentially be permanently attached to the control section  22 ). 
     The interface  26  generally provides a structural (mechanical), electrical and airflow path connection between the control section  22  and the cartridge section  24 . For example, the interface  26  may provide appropriately arranged electrical contacts for establishing various electrical connections between the two sections. Likewise, the interface may support (define) an airflow channel (path) between the two sections as appropriate. 
     It will be appreciated that other implementations of the electronic aerosol provision system  20  may have a different configuration; moreover, different features from different implementations as described herein may be mixed together as appropriate. For example, in some implementations, the control section  22  and the cartridge section  24  might be fixed together (rather than being detachable); as noted above, this might be the case when the cartridge section  24  is re-Tillable in situ. In some implementations, a vaporizer may be provided in the control section  22  rather than in the cartridge section  24 , in which case the interface  26  might be configured to support the transfer of a vapor precursor (such as a liquid) from the cartridge section  24  to the control section  22 —but without necessarily supporting the transfer of electrical power from the control section  22  to the cartridge section  24 . In some implementations, the interface  26  may support a wireless transfer of power from the control section to the cartridge section, for example, based on electromagnetic induction. In this case, a direct physical (electrical) connection between the control section  22  and the cartridge section  24  may not be provided. Furthermore, in some implementations, the airflow path through the electronic aerosol provision device  20  might not go through the control section  22 , hence the interface  26  might not include an airflow channel connection between the control section  22  and the cartridge section  24 . The skilled person will be aware of various other potential modifications. 
     In the example of  FIG. 1 , the cartridge section  24  comprises a cartridge housing  62  which may be made of plastic or any other suitable material. The cartridge housing  62  supports other components of the cartridge section  24  and provides a mechanical interface with the control section  22  as part of interface  26 . The cartridge section includes an airflow channel (or pathway)  72  and a mouthpiece  70  which defines an air outlet  71  from the airflow channel  72 . 
     Within the cartridge housing  62  is a reservoir  64  that contains a liquid to provide a vapor precursor material; this is often referred to as an e-liquid. The liquid reservoir  64  in the device of  FIG. 1  has an annular shape about (around) the airflow channel  72 . The shape of the reservoir  64  is defined by an outer wall, provided by the cartridge housing  62 , and an inner wall that forms the outside or boundary of the airflow channel  72  through the cartridge section  24 . The reservoir  64  is closed at each end to retain the e-liquid, by mouthpiece  70  at the downstream end of the cartridge section  24  and by the housing  62  forming interface  26  at the upstream end. 
     The cartridge section  24  further comprises a wick (liquid transport element)  66  and a heater (vaporizer)  68 . In the device shown in  FIG. 1 , the wick  66  extends transversely across the cartridge airflow channel  72 , i.e. perpendicular to the airflow direction along channel  72 . Each end of the wick is configured to draw liquid from the reservoir  64  through one or more openings in the inner wall of the liquid reservoir  64 . The e-liquid infiltrates the wick  66  and is drawn along the wick  66  by capillary action (i.e. wicking). The heater  68  may comprise an electrically resistive wire coiled around the wick  66 , for example a nickel chrome alloy (Cr20Ni80) wire, and the wick  66  may comprise a glass fibre bundle or a cotton fibre bundle. Many other options will be apparent to the skilled person; for example, the wick might be made of ceramic, the wick and heater coil might be arranged longitudinally rather than transversely, there might be multiple heater coils  68 , there might be multiple wicks  66 , the heater  68  may have a planar configuration, and so on. 
     During use, electrical power may be supplied to the heater  68  to vaporize an amount of e-liquid (vapor precursor material) drawn to the vicinity of the heater  68  by the wick  66 . The vaporized e-liquid then becomes entrained in air drawn along the cartridge airflow channel  72  towards the mouthpiece outlet  70  for user inhalation. The rate at which e-liquid is vaporized by the vaporizer (heater)  68  generally depends on the amount of power supplied to the heater  68 , as well as the wicking or liquid transport capacity of wick  66 . In some devices, the rate of vapor generation (the vaporisation rate) can be adjusted by changing the amount of power supplied to the heater  68 , for example through the use of pulse width or frequency modulation techniques. In general, the e-liquid vapor formed by the heater  68  cools in the airflow channel  72  and at least partially condenses into particles (small droplets of liquid), thereby forming an aerosol. It is this aerosol that is then inhaled by a user through mouthpiece outlets  71 . 
     The control section  22  shown in  FIG. 1  comprises an outer housing  32  with an opening that defines an air inlet  48  for the e-cigarette  20 , a battery  46  for providing electrical power to operate the e-cigarette  20 , control circuitry  38  for controlling and monitoring the operation of the e-cigarette  20 , a user input button  34  and a visual display indicator  44 . The outer housing  32  is configured to receive the cartridge section  24 , thereby providing a smooth integration (union) of the two sections or parts at the interface  26 . For example, the outer housing  32  may include clips or slots or any other suitable engagement features for receiving corresponding features of the cartridge section  24 . 
     The battery  46  is generally rechargeable such as through a charging connector in the control section housing  32 , e.g. a USB connector (not shown in  FIG. 1 ). The user input button  34  may be used to perform various control functions. The display  44  may (for example) comprise one or more LEDs for displaying information about the charge status of the battery  46  or any other suitable information or indication. In some implementations, the user input button  34  and the display  44  may be integrated as a single component. The control circuitry  38  is suitably configured (programmed) to control the operation of the electronic cigarette, for example to regulate the supply of power from the battery  46  to the heater  68  for generating vapor. 
     The air inlet  48  connects to an airflow path  50  through the control section  22 . The control part section path  50  in turn connects to the cartridge airflow channel  72  via the interface  26  when the control part  22  and cartridge part  24  are connected together. Thus, when a user inhales on the mouthpiece  70 , air is drawn in through the air inlet  48 , along the control section air path  50 , through the interface  26 , along the cartridge airflow channel  72 , and out through the opening of the mouthpiece  70  for user inhalation. In the example of  FIG. 1 , the airflow path  50  is configured so that the airflow through air inlet  48  is perpendicular to the airflow through the air outlet  71  during a user inhalation. In particular, the air inlet  48  is arranged on a side of the outer housing  32  (rather than the base). Such an air inlet may be termed a side hole. The airflow path  50  incorporates a corner or angle whereby the airflow during an inhalation transitions sharply from a first direction of airflow from the air inlet  48  to the corner to a second direction of airflow from the corner to the interface  26 . As can be seen in  FIG. 1 , the second direction of travel is perpendicular to the first direction of travel. 
       FIG. 2  is a schematic cross-sectional representation of a second electronic aerosol provision device  200 . The components of the e-cigarette  200  of  FIG. 2  are generally the same as or similar to those described in relation to  FIG. 1  (and labelled with like reference numbers), and so these components will not be discussed again. However, in contrast to the first e-cigarette  20  of  FIG. 1 , which comprises a side hole air inlet  48 , the second e-cigarette  200  of  FIG. 2  comprises an air inlet  248  in the base (or bottom) of the e-cigarette (where the orientation of an e-cigarette is defined in the conventional manner such that the mouthpiece  71  is at the top). With this location for the air inlet  248 , the control section airflow pathway  250  and the cartridge section airflow pathway  72  are coaxially aligned such that there is a straight air path along the length of the airflow channel. Thus as shown in  FIG. 2 , the airflow channels  250 ,  72  of electronic vapor provision device  200  are aligned such that airflow through the device from the air inlet  248  to the vaporizer  68  and then out through the mouthpiece  70  follows a substantially straight line (linear) pathway, i.e. heading in substantially a single direction, without changing direction, curving, bending, etc. 
     Although  FIG. 2  shows one example in which the airflow pathways in the control section  22  and in the cartridge section  24  have a coaxial (co-aligned) configuration, it will be appreciated that such a configuration may be achieved differently in other implementations. Furthermore, while e-cigarette  200  is shown as having two modules (cartridge part  24  and control part  22 ), other implementations with a coaxial configuration for airflow pathways  52  and  72  may be implemented as a one-piece device, or else as a system comprising more than two modules. 
     The straight (linear) configuration of the airflow channel  250  through the control section  22  in  FIG. 2 , compared with the angled (cornered) configuration in the airflow channel  50  of e-cigarette  20  in  FIG. 1 , helps to support a laminar airflow within the channel  250 . In a laminar airflow (also referred to herein as a linear airflow), the air generally all flows in parallel in the same direction. For example, for laminar airflow along a cylindrical pipe, all the air flows in parallel in an axial direction along the pipe. The airflow velocity along the pipe has a radial profile according to distance from the centre of the pipe. The air flowing along the central axis of the pipe flows most quickly, while the airflow velocity then gradually drops with radial distance away from the centre to a zero velocity adjacent the edge or wall of the pipe in a region referred to as the boundary layer. 
     In contrast to laminar flow, the presence of features such as corners, bends, obstructions, etc. along an airflow path generally introduces turbulence into the airflow. This turbulent airflow (also referred to herein as non-linear airflow) is created by, and reflects, localised variations in air pressure and other instabilities. For example, air flowing around (but close to) an obstruction may have a higher pressure than air flowing further away from the obstruction; this may then be balanced by a region of relatively low pressure immediately after the obstruction. Localised movements of air in effect seek to rebalance the air pressure variations, and thereby introduce turbulence into the airflow. 
     Note that turbulence may also arise even in an axially aligned channel shown in  FIG. 2 . For example, if the air is pushed through a pipe too quickly (i.e. with too great a pressure difference), the high level of radial shear resulting from different axial velocities at different radial distances out from the centre of the channel disrupts the airflow, leading to instabilities and other forms of turbulence. 
     A dimensionless parameter known as the Reynolds number (R) is often used to characterise the laminar and turbulent flow regimes. The Reynolds number is defined as R=uL/v, where u is the flow speed, v the viscosity, and L is a linear scale size of the flow (this might be the diameter of a pipe, for example). A low Reynolds number will generally produce laminar flow, while a high Reynolds number will generally produce turbulent flow. The transition between laminar flow and turbulent flow might typically occur for R in the range 2000-3000 (although this transition point is typically sensitive to various factors, and may lie outside the above range in some circumstances). Note that increasing the flow speed increases the Reynolds number, and hence may induce a transition to turbulent flow, as noted above. In contrast, increasing the viscosity will decrease the Reynolds number; this can be regarded as a higher viscosity damping out turbulent motion. 
       FIGS. 3 and 4  are graphs showing the frequency distributions of particle sizes produced by the first and second example e-cigarettes, namely the side-hole device  20  of  FIG. 1  and the linear flow device  200  of  FIG. 2  respectively. The particle size refers to the size of particles or droplets in the vapor or aerosol exiting the device through air outlets  71 . Each graph shows ten repeated measurements of the particle size distribution. Statistical summaries of the frequency distribution of the particle sizes for each measurement are provided in Tables 1 and 2 below. 
     
       
         
           
               
             
               
                 TABLE 1 
               
             
            
               
                   
               
               
                 “Side-hole” e-cigarette 
               
            
           
           
               
               
               
               
               
               
               
            
               
                   
                 Date - Time 
                 File 
                 Cv(%) 
                 Dx(10) 
                 Dx(50) 
                 Dx(80) 
               
               
                   
               
               
                    [V] 
                 4 Dec. 2017 - 16:15:03.0384 
                 171204 Side Hole r1 1.1 
                 1.0014 
                 0.39 
                 1.12 
                 2.56 
               
               
                    [V] 
                 4 Dec. 2017 - 16:15:32.9526 
                 171204 Side Hole r1 1.2 
                 0.0016 
                 0.47 
                 1.28 
                 2.69 
               
               
                    [V] 
                 4 Dec. 2017 - 16:16:02.9672 
                 171204 Side Hole r1 1.3 
                 0.0016 
                 0.63 
                 1.44 
                 3.00 
               
               
                    [V] 
                 4 Dec. 2017 - 16:16:33.0216 
                 171204 Side Hole r1 1.4 
                 0.0020 
                 0.32 
                 1.68 
                 3.33 
               
               
                    [V] 
                 4 Dec. 2017 - 16:17:03.0560 
                 171204 Side Hole r1 1.5 
                 0.0016 
                 0.65 
                 1.50 
                 3.15 
               
               
                    [V] 
                 4 Dec. 2017 - 16:17:33.0904 
                 171204 Side Hole r1 1.6 
                 0.0021 
                 0.92 
                 1.77 
                 3.33 
               
               
                    [V] 
                 4 Dec. 2017 - 16:18:03.1246 
                 171204 Side Hole r1 1.7 
                 0.0016 
                 0.86 
                 1.71 
                 3.32 
               
               
                    [V] 
                 4 Dec. 2017 - 16:18:33.1584 
                 171204 Side Hole r1 1.8 
                 0.0017 
                 0.87 
                 1.70 
                 3.23 
               
               
                    [V] 
                 4 Dec. 2017 - 16:19:03.1926 
                 171204 Side Hole r1 1.9 
                 0.0017 
                 0.74 
                 1.55 
                 3.08 
               
               
                    [V] 
                 4 Dec. 2017 - 16:19:33.2272 
                 171204 Side Hole r1 1.10 
                 0.0017 
                 0.96 
                 1.81 
                 3.37 
               
               
                   
               
               
                 [V] = Volume 
               
               
                 [N] = Number 
               
            
           
         
       
     
     
       
         
           
               
             
               
                 TABLE 2 
               
             
            
               
                   
               
               
                 “Direct linear flow” e-cigarette 
               
            
           
           
               
               
               
               
               
               
               
            
               
                   
                 Date - Time 
                 File 
                 Cv(%) 
                 Dx(10) 
                 Dx(50) 
                 Dx(80) 
               
               
                   
               
               
                    [V] 
                 14 Dec. 2017 - 11:56:39.4 . . .  
                 171214 al bh beta 58 r1 1.1 
                 0.0014 
                 0.20 
                 0.53 
                 1.36 
               
               
                    [V] 
                 14 Dec. 2017 - 11:57:09.3 . . .  
                 171214 al bh beta 58 r1 1.2 
                 0.0011 
                 0.23 
                 0.62 
                 1.53 
               
               
                    [V] 
                 14 Dec. 2017 - 11:57:39.3 . . .  
                 171214 al bh beta 58 r1 1.3 
                 0.0013 
                 0.22 
                 0.68 
                 1.93 
               
               
                    [V] 
                 14 Dec. 2017 - 11:58:09.4 . . .  
                 171214 al bh beta 58 r1 1.4 
                 0.0012 
                 0.27 
                 0.85 
                 1.24 
               
               
                    [V] 
                 14 Dec. 2017 - 11:58:39.4 . . .  
                 171214 al bh beta 58 r1 1.5 
                 0.0012 
                 0.25 
                 0.76 
                 1.99 
               
               
                    [V] 
                 14 Dec. 2017 - 11:59:09.4 . . .  
                 171214 al bh beta 58 r1 1.6 
                 0.0011 
                 0.23 
                 0.72 
                 2.15 
               
               
                    [V] 
                 14 Dec. 2017 - 11:59:39.5 . . .  
                 171214 al bh beta 58 r1 1.7 
                 0.0015 
                 0.20 
                 0.55 
                 1.56 
               
               
                    [V] 
                 14 Dec. 2017 - 12:00:09.5 . . .  
                 171214 al bh beta 58 r1 1.8 
                 0.0015 
                 0.22 
                 0.65 
                 1.91 
               
               
                    [V] 
                 14 Dec. 2017 - 12:00:39.5 . . .  
                 171214 al bh beta 58 r1 1.9 
                 0.0015 
                 0.54 
                 1.25 
                 2.41 
               
               
                    [V] 
                 14 Dec. 2017 - 12:01:09.6 . . .  
                 171214 al bh beta 58 r1 1.10 
                 0.0014 
                 0.30 
                 0.97 
                 2.47 
               
               
                   
               
               
                 [V] = Volume 
               
               
                 [N] = Number 
               
            
           
         
       
     
     The final three columns of each Table define parameters of the particle size distribution for that measurement. Thus in the first line of Table 1, Dx(10)=0.39 implies that 10% of the particles have a size less than 0.39 microns (μm), Dx(50)=1.12 implies that 50% of the particles have a size less than 1.12 microns (μm) (i.e. this is the median size), and Dx(00)=2.56 implies that 90% of the particles have a size less than 2.56 microns (μm). A comparison of  FIGS. 3 and 4  (and the associated tables) clearly shows that the particle sizes are generally smaller for a direct linear flow e-cigarette (such as shown in  FIG. 2 ) than for a side-hole e-cigarette (such as shown in  FIG. 1 ). It is also suggested that the direct linear flow measurements of  FIG. 4  produce a slightly tighter (more compact) distribution than the side-hole measurements of  FIG. 3 . 
     Without being bound by theory, it is considered that the laminar (non-turbulent) airflow may form an aerosol having a smaller particle size than the non-laminar (turbulent) airflow because the turbulence causes more collisions between aerosol particles, and such collisions may lead to coagulation between particles and hence a growth in particle size. In contrast, when the airflow is laminar, coagulation among particles might be reduced since the airflow is substantially all in parallel, aligned with the axial direction. Consequently, there is less mixing in the airflow, and hence less potential for coagulation. It is also possible that turbulence brings more vapor into contact with particles, and hence leads to a faster condensation of vapor onto the particles (compared with laminar flow), thereby leading to a larger particles. This faster condensation of vapor onto the existing particles may occur in addition to, or in place of, the faster coagulation of particles. 
     It has been found that an enhanced user experience can be achieved by an electronic vapor provision system that generally provides an aerosol having a smaller particle size for inhalation by the user. Without being bound by theory, this user preference for a smaller particle size may arise from one or more factors, such as easier absorption of the particles by tissue, increased lightness or diffusiveness of the particles, greater uniformity (consistency) of the particles, increased travel distance of the particles, etc. 
     In view of this user preference, the airflow configuration of the e-cigarette  200  of  FIG. 2  is advantageous with respect to the airflow configuration of the e-cigarette  20  of  FIG. 1 , because the straight airflow channel  250  of  FIG. 2  helps to provide laminar airflow, and hence a smaller particle size, compared with the angled airflow channel  50  of  FIG. 1 . In practice, in many actual devices, the airflow may have both laminar and turbulent components. Increasing the proportion of laminar components at the expense of the turbulent components should still help promote a reduced particle size and hence an improved user experience. Accordingly, the benefits of providing a laminar flow are not binary (all or nothing), but rather can be realised by incrementally increasing the proportion of laminar flow in a given device. 
       FIG. 5  is a schematic cross-sectional representation of a third electronic aerosol provision device  500 . The components of the e-cigarette  500  of  FIG. 5  are generally the same as or similar to those described in relation to  FIG. 1  (and labelled with like reference numbers), and so these components will not be discussed again. In contrast to the example e-cigarette  20  of  FIG. 1 , which comprises a side hole air inlet  48  with an angled airflow channel  50 , and also in contrast to the example e-cigarette  200  of  FIG. 2 , which comprises an air inlet  248  in the base (or bottom) of the e-cigarette  200  to provide a straight line (linear) airflow channel  250 , the e-cigarette  500  of  FIG. 5  comprises an airflow pathway  550  in the control section  22  which is side-opening  548  (like the e-cigarette  20  of  FIG. 1 ), but having a smooth, continuous curve for the airflow channel  550  between the air inlet  548  (side-hole) and the interface  26 . 
     Configuring the airflow pathway  550  to have such a continuous curve, rather than a sharp corner or angle, helps to support laminar air flow. Thus implementing an air pathway  550  which imparts a gradual change in direction of the airflow allows the device to comprise a side-hole but with a lower level of turbulence (if any), compared with the configuration of  FIG. 1 . An example e-cigarette  500  may therefore have an airflow channel  550  with a radius of curvature greater than 5 mm, greater than 10 mm, or preferably greater than 15 mm, to reduce (or eliminate) turbulence (compared with the configuration of  FIG. 1 ), and so help to reduce particle size in the aerosol provided by the device. 
     In some implementations, the continuous curve of the airflow channel  550  may only extend part-way between the air inlet  548  and the interface  26 . For example, the airflow channel  550  may have a smoothly curved portion near air inlet  548 , followed by a linear portion near the interface  26  (or conversely, the airflow channel  550  may have a smoothly curved portion near the interface  26 , following on from a linear portion near the air inlet  548 ). More generally, there may be more than one continuous curve or more than one linear section in the airflow channel  550 . A further possibility is that a continuous curve (or multiple such curves) might be approximated by a sequence of short linear sections, whereby the change in orientation of between any two successive linear sections is small, for example, in the range of 1-5 degrees, so as to limit or avoid the introduction of turbulence. 
       FIG. 6  is a schematic cross-sectional representation of a fourth electronic aerosol provision device  600 . The components of the e-cigarette  600  of  FIG. 6  are generally the same as or similar to those described in relation to  FIG. 1  (and labelled with like reference numbers), and so these components will not be discussed again. In contrast to the e-cigarettes shown in  FIGS. 1, 2 and 5 , which have fixed airflow channel configurations, the e-cigarette  600  of  FIG. 6  has an airflow pathway  650  which may be modified to change the level of turbulence in air inhaled through the device. In other words, the e-cigarette  600  of  FIG. 6  includes a facility to adjust the air pathway to control the amount of turbulence within the air pathway, and hence to change the particle size distribution in the aerosol produced by the e-cigarette  600 . 
     The airflow channel  650  of e-cigarette  600  comprises two sections, a first movable channel section  610  and a second fixed section  610 . These two sections are joined by an appropriate coupling or connector  615 . The first movable airflow channel section  610  therefore extends from the air inlet  648  to the coupling  615 , while the second airflow channel section  611  extends from the coupling  615  to the interface  26 . The movable airflow channel section  610  in effect is able to rotate about the coupling  615  to reposition the air inlet  648 . In particular, the position of the air inlet  648  can be rotated as indicated by the arrows between position A and position A′. In position A′, the e-cigarette  600  approximates the side-hole configuration shown in  FIG. 1 , while in position A the e-cigarette  600  approximates the direct linear flow (bottom hole) configuration shown in  FIG. 2 . 
     The e-cigarette  600  includes a switch or button  625  for a user to rotate the movable section  610  between positions A and A′. This switch  625  may be provided with a suitable mechanical coupling (not shown) to accomplish this rotation of the movable section  610 . Another possibility is that the rotation of section  610  is performed using electrical power from battery  46  (again under the control of switch or button  625 ). Other actuation mechanisms may be implemented, including direct movement by a user of the movable section  610 , in which case button/switch  625  might be omitted. 
     Although the e-cigarette  600  has been described above as having two operational positions for movable section  610  corresponding to A and A′ (so that the position shown in  FIG. 6  is transitional between these two operational positions), other implementations may have one or more additional operational positions intermediate A and A′. Some implementations may allow a continuous adjustment, i.e. the movable section  610  can be located at any desired position intermediate A and A′. It will be appreciated that the portion  621  of the control section housing  32  in which air inlet  648  is formed will be arranged to accommodate the desired range of positions for the air inlet  648 . 
     By moving the position of the air inlet  648  from position A to position A′ (through any supported intermediate positions) an increasing level of turbulence can be imparted to the airflow—which as described above, will generally result in an aerosol having a larger particle size. This provides users with control over a parameter (particle size) which has a direct physical impact on their experience of using the e-cigarette  600 . In particular, different particle sizes (large or small) may be preferred by different users, or for different cartridges, different e-liquids, or just in different user circumstances. The use of button  625  to control the position of air inlet  648  by moving section  610  to adjust turbulence provides users with a control over aerosol particle size according to their specific preferences and circumstances. 
     For example, in a first orientation, as indicated by position A, the movable channel section  610  is co-aligned with the remainder of the airflow channel  650 , in particular fixed section  611 , and so turbulence is minimised. In a second orientation, as indicated by position A′, the movable channel section  610  is now perpendicular to the remainder of the airflow channel  650  and so turbulence is introduced (or increased). Note that this mechanism allows the level of turbulence to be altered with little or no change to the overall flow rate. In particular, the size of the air inlet  648  and hence the amount of air inhaled during a puff is substantially maintained regardless of the orientation of the movable channel section  610 , however, the particle size distribution for the puff is dependent on (and controlled by) the location setting of the movable channel section  610 . 
     As described above, the orientation of the movable airflow section  610  may be selected by a user interacting with the device through a mechanical switch  625  or similar device such as a wheel or lever to allow the user to tailor the particle size to his/her particular preference. In some implementations, this adjustment of the movable airflow section  610  may be performed using the user input button  34  or the visual display indicator  44  (in place of, or additionally to, using switch  625 ). The changes to the orientation may be performed very quickly, for example during or between puffs (activations of the heater  68 ), thereby allowing the user to quickly adjust the particle size to a desired setting. A further possibility is that in some circumstances at least, the orientation of the movable channel section  610  may be automatically performed by the control circuitry  38 , for example, after recognising that a particular cartridge  24  containing a particular e-liquid has been attached to the control unit  22 . 
       FIG. 7  is a schematic cross-sectional representation of a fifth electronic aerosol provision device  700 . The components of the e-cigarette  700  of  FIG. 7  are generally the same as or similar to those described in relation to  FIG. 1  (and labelled with like reference numbers), and so these components will not be discussed again. More particularly, the e-cigarette  700  of  FIG. 7  has a configuration which is very similar the e-cigarette  200  of  FIG. 2 , but further includes, like the e-cigarette  600  of  FIG. 6 , a facility to adjust the particle size distribution in the aerosol produced by the e-cigarette  700 . 
     Thus as shown in  FIG. 7 , e-cigarette  700  comprises a fixed airflow pathway  750  extending to air inlet  748  using a direct linear flow configuration, the same as for e-cigarette  200  as shown in  FIG. 2 . However, the e-cigarette  700  further includes a mechanism  715  (shown in schematic form in  FIG. 7 ) to alter the configuration of the air pathway  750  so as to modify the relative proportion of laminar and turbulent airflow within the air pathway  750 , thereby providing some control over the resulting particle size distribution of the aerosol produced by the e-cigarette  700 . The mechanism  715  may be operated by a user via button or switch  725  in a similar manner to the use of button  625  in e-cigarette  600  to move the airflow channel section  610 . Likewise, the operation of mechanism  715  might be performed using the user input button  34  or the visual display indicator  44  (in place of, or additionally to, using switch  725 ) or at least partly automatically by the control circuitry  38 . 
     One implementation of mechanism  715  is a shaped diaphragm or aperture which may be changed, for example, between a simple circular shape for the opening to a star shape (or any other more complex shape) for the opening. The circular shape introduces relative little turbulence, and hence supports a higher proportion of laminar flow, whereas the more complex (detailed) star-shaped aperture tends to introduce more turbulence by creating more localised variations in pressure, and so leads to a lower proportion of laminar flow. The switching between the different aperture shapes may be actuated, for example, using button or switch  725 . 
     In other implementations, a wall feature, such as a baffle, fin or other obstruction (or multiple such items) may be moved into or out of the airflow path  750 . Inserting such a feature can again lead to more localised pressure variations that promote the formation of turbulence. Accordingly, the level of turbulence (and hence the resulting particle size) may be controlled by adjusting the extent of the insertion or extraction of such obstructions into the airflow channel  750  (e.g. by using button or switch  725 ). A similar effect could be achieved, for example, by forming or flattening surface texture or other topology on the inside walls of the airflow channel  750 . 
     Another potential implementation of mechanism  715  comprises a grill, grating or other similar structure, which may be moved into the airflow path  750  to increase the turbulence of the airflow. Typically the grating is formed of fine wire, or similar, such that the grating acts to disrupt and impart turbulence to the airflow, but does not inhibit the airflow rate. In some implementations, the grill  715  may be permanently located in the airflow path  750 , however, the configuration or some other property (or properties) of the grill might be varied, such as the size of individual openings within the grill, to change the amount of turbulence produced in the airflow. A further example of mechanism  715  is an airflow divider, which may be positioned in the airflow path  750  to divide the airflow channel into two or more subchannels. Both the separation of the airflow into the multiple air channels, and then the subsequent recombination of the airflow into a single channel, may lead to the formation of turbulence in the airflow. By varying the proportion of air in each component, the level of turbulence may be controlled. 
     In some implementations, the mechanism  715  may not only impact the relative proportion of laminar to turbulent flow, but also the rate of airflow through the e-cigarette for a given pressure drop or strength of inhalation—in effect, increasing the resistance to draw (RTD). For example, introducing fins or other obstructions into the airflow will generally act as additional RTD resistance to the airflow, in addition to increasing the amount of turbulence. It may be desirable however to allow a user to control the amount of turbulence (and hence particle size) while making little or no change to the RTD (and hence to the overall flow rate). One way of achieving this is for the e-cigarette to include a restrictor somewhere along the overall airflow path which is the primary restriction on the airflow through the e-cigarette. In such a configuration, any changes in RTD caused by different settings of the mechanism  715  will have a relatively low impact on the overall RTD experienced by a user. Another approach is for the different settings of the mechanism  715  to be designed to alter the amount of turbulence, but not the overall airflow resistance. For example, for the implementation discussed above using a circular aperture to reduce turbulence and a star-shaped aperture to increase turbulence, the sizes of the circular and star-shaped apertures may be arranged so as to provide the same airflow resistance (RTD contribution) for both apertures. 
     Although mechanism  715  is shown in  FIG. 7  as implemented in the middle of airflow channel  750 , it may instead be implemented at the air inlet  748  or the interface  26 , or at any suitable location between the air inlet  748  and the interface  26 . In some implementations, the mechanism  715  may comprise multiple components at various locations along the air pathway  750 . Alternatively, the mechanism  715  may stretch along a substantial portion (e.g. most or all) of the airflow channel  750  between the air inlet  748  and the interface  26 . Furthermore, while the air pathway  750  shown in  FIG. 7  is substantially linear (a straight line), other implementations may have a curved air pathway, for example, similar to the shape shown in  FIG. 5  for e-cigarette  500 . 
     As described above, the present approach provides an electronic aerosol provision system or device comprising: an air pathway between an air inlet and an air outlet; and a vaporizer for generating vapor into the air pathway. The air pathway between the air inlet and the vaporizer is configured to support laminar airflow. 
     It has been found that such a laminar airflow can lead to smaller aerosol particles exiting the electronic aerosol provision system, which in turn can lead to a more favourable user experience. It is believed (without limitation) that a laminar airflow may produce a smaller particle size by reducing particle coagulation or by reducing vapor deposition onto particles. Although these physical effects generally happen downstream of the vaporizer, it is difficult to quiesce an airflow within the electronic aerosol provision system which is already turbulent. Accordingly the approach described herein seeks to prevent or reduce the formation of turbulence upstream of the vaporizer, which then helps to prevent or reduce turbulence at (and downstream of) the vaporizer. 
     An ideal device might have laminar (non-turbulent) airflow along the entire airflow pathway within the device, from air inlet to air outlet. However, it may be difficult in practice to achieve completely laminar airflow within the device, rather the air pathway between the air inlet and the vaporizer may be configured to support substantially (mostly) laminar airflow, for example, having at least 60%, 75%, 85%, 90% or 95% of the airflow through the electronic aerosol provision device being laminar. 
     There are various ways in which the air pathway, at least between the air inlet and the vaporizer, may be configured to support (mostly) laminar airflow. For example, the air pathway may comprise a linear (straight line) channel between the air inlet and the vaporizer; the absence of sharp bends or angles facilitates laminar flow. In some cases the air pathway between the air inlet and the vaporizer may include one or more curved portions; each of the one or more curved portions may have a radius of curvature greater than 5 mm and preferably greater than 15 mm. Again, the provision of gentle curves rather than sharp bends or angles facilitates laminar flow (and also gives more flexibility in the overall geometry of the device compared with having a straight line airflow). Laminar flow along the air pathway between the air inlet and the vaporizer may be further facilitated by ensuring this pathway is substantially free of (i) obstructions, for example, protrusions, grills, narrow apertures, etc., or (ii) topology for the walls of the air pathway, for example, surface texturing or other features, that would introduce turbulence into airflow along the air pathway. It will be appreciated that a similar approach may be adopted for the portion of the air pathway downstream of the vaporizer in order to reduce or prevent turbulence in this downstream portion. 
     The present approach also provides an electronic aerosol provision system (e.g. such as described above) which comprises a facility to control turbulence within the air pathway. In some implementations, the facility provides at least first and second settings, the first setting providing an airflow with a higher proportion of laminar flow relative to turbulence than the second setting. As noted above, the first setting will generally therefore produce an aerosol having a smaller particle size than the second setting. For example, the first setting may produce an aerosol having a median particle size (e.g. based on diameter) that is at least 10%, preferably at least 20%, smaller than the median particle size of an aerosol produced by the second setting, or the first setting produces an aerosol having a median particle size less than 1 micron and the second setting produces an aerosol having a median particle size greater than 1 micron. (It will be appreciated that these ratios/sizings are given by way of example only, since they are influenced by additional factors, such as the nature of the vaporizer). 
     It will be appreciated that while some devices may have just two settings of the facility, other devices may have more settings; furthermore some devices may support a continuous range of settings between upper and lower limits. In general, the facility may be operated by a user to control turbulence by selecting an appropriate setting, such as by actuating a button or slider, or touching a touch-sensitive input device. In this way, a user can select a setting that provides them with the most satisfactory user experience. In other cases, the facility might be alternatively (or additionally) operated on an automatic basis. For example, the device might detect that a particular cartridge or cartomizer has been installed, and set the facility to provide the most appropriate turbulence level for this cartridge. 
     There are various ways in which the facility may be implemented. For example, in some cases the facility might support movement of the airflow pathway such as to introduce or remove a linear channel between the air inlet and the vaporizer. Other ways of changing the turbulence level might be to use a (re)movable airflow divider to divide a portion of the air pathway into two or more channels; a variable aperture (or apertures) along the pathway; or one or more structures that can be introduced into or altered within the air pathway. Note that the facility might utilise multiple different approaches for changing the level of turbulence. 
     In some implementations, the facility is arranged to maintain a substantially constant airflow through the air pathway as the facility provides different levels of turbulence. For example, the facility may use a smooth (circular) aperture to reduce turbulence, or a more angled aperture, e.g. a star, to increase turbulence. The overall size of each aperture may then be configured such that the differently shaped apertures provide the same resistance to draw (and hence overall airflow). In this way, a user is able to adjust the particle size of the aerosol without also changing other parameters of the device, such as resistance to draw, which supports easier device management for a user. 
     In order to address various issues and advance the art, this disclosure shows by way of illustration various embodiments in which the claimed disclosure may be practiced. The advantages and features of the disclosure are of a representative sample of embodiments only, and are not exhaustive or exclusive. They are presented only to assist in understanding and to teach the claimed disclosure. It is to be understood that advantages, embodiments, examples, functions, features, structures, or other aspects of the disclosure are not to be considered limitations on the disclosure as defined by the claims or limitations on equivalents to the claims, and that other embodiments may be utilised and modifications may be made without departing from the scope of the claims. Various embodiments may suitably comprise, consist of, or consist essentially of, various combinations of the disclosed elements, components, features, parts, steps, means, etc. other than those specifically described herein, and it will thus be appreciated that features of the dependent claims may be combined with features of the independent claims in combinations other than those explicitly set out in the claims. The disclosure may include other embodiments not presently claimed, but which may be claimed in future.