Patent Description:
It is thought that a significant amount of the potentially harmful substances are generated through the burning and/or combustion of the tobacco and the constituents of the burnt tobacco in the tobacco smoke itself.

Low temperature combustion of organic material such as tobacco is known to produce tar and other potentially harmful by-products. There have been proposed various smoking substitute systems in which the conventional smoking of tobacco is avoided.

Known smoking substitute systems include electronic systems that permit a user to simulate the act of smoking by producing an aerosol (also referred to as a "vapour") that is drawn into the lungs through the mouth (inhaled) and then exhaled. The inhaled aerosol typically bears nicotine and/or a flavourant without, or with fewer of, the health risks associated with conventional smoking.

In general, smoking substitute systems are intended to provide a substitute for the rituals of smoking, whilst providing the user with a similar, or improved, experience and satisfaction to those experienced with conventional smoking and with combustible tobacco products.

The popularity and use of smoking substitute systems has grown rapidly in the past few years. Although originally marketed as an aid to assist habitual smokers wishing to quit tobacco smoking, consumers are increasingly viewing smoking substitute systems as desirable lifestyle accessories. There are a number of different categories of smoking substitute systems, each utilising a different smoking substitute approach. Some smoking substitute systems are designed to resemble a conventional cigarette and are cylindrical in form with a mouthpiece at one end. Other smoking substitute devices do not generally resemble a cigarette (for example, the smoking substitute device may have a generally box-like form, in whole or in part).

One approach is the so-called "vaping" approach, in which a vaporisable liquid, or an aerosol former, sometimes typically referred to herein as "e-liquid", is heated by a heating device (sometimes referred to herein as an electronic cigarette or "e-cigarette" device) to produce an aerosol vapour which is inhaled by a user. The e-liquid typically includes a base liquid, nicotine and may include a flavourant. The resulting vapour therefore also typically contains nicotine and/or a flavourant. The base liquid may include propylene glycol and/or vegetable glycerine.

A typical e-cigarette device includes a mouthpiece, a power source (typically a battery), a tank for containing e-liquid and a heating device.

E-cigarettes can be configured in a variety of ways. For example, there are "closed system" vaping smoking substitute systems, which typically have a sealed tank and heating element. The tank is prefilled with e-liquid and is not intended to be refilled by an end user. One subset of closed system vaping smoking substitute systems include a main body which includes the power source, wherein the main body is configured to be physically and electrically couplable to a consumable including the tank and the heating element. In this way, when the tank of a consumable has been emptied of e-liquid, that consumable is removed from the main body and disposed of. The main body can then be reused by connecting it to a new, replacement, consumable. Another subset of closed system vaping smoking substitute systems are completely disposable, and intended for one-use only.

There are also "open system" vaping smoking substitute systems which typically have a tank that is configured to be refilled by a user. In this way the entire device can be used multiple times.

An example vaping smoking substitute system is the myblu™ e-cigarette. The myblu™ e-cigarette is a closed system which includes a main body and a consumable. The main body and consumable are physically and electrically coupled together by pushing the consumable into the main body. The main body includes a rechargeable battery. The consumable includes a mouthpiece and a sealed tank which contains e-liquid. The consumable further includes a heater, which for this device is a heating filament coiled around a portion of a wick. The wick is partially immersed in the e-liquid, and conveys e-liquid from the tank to the heating filament. The system is controlled by a microprocessor on board the main body. The system includes a sensor for detecting when a user is inhaling through the mouthpiece, the microprocessor then activating the device in response. When the system is activated, electrical energy is supplied from the power source to the heating device, which heats e-liquid from the tank to produce a vapour which is inhaled by a user through the mouthpiece.

<CIT> discloses a cartridge for an aerosol-generating system with heater protection.

<CIT> discloses an electronic cigarette, a heating assembly and heating bodies thereof.

For a smoking substitute system it is desirable to deliver nicotine into the user's lungs, where it can be absorbed into the bloodstream. However, the present disclosure is based in part on a realisation that some prior art smoking substitute systems, such delivery of nicotine is not efficient. In some prior art systems, the aerosol droplets have a size distribution that is not suitable for delivering nicotine to the lungs. Aerosol droplets of a large particle size tend to be deposited in the mouth and/or upper respiratory tract. Aerosol particles of a small (e.g. sub-micron) particle size can be inhaled into the lungs but may be exhaled without delivering nicotine to the lungs. As a result the user would require drawing a longer puff, more puffs, or vaporising e-liquid with a higher nicotine concentration in order to achieve the desired experience.

Accordingly, there is a need for improvement in the delivery of nicotine to a user in the context of a smoking substitute system.

In a first aspect, the present invention provides a smoking substitute apparatus comprising:.

The provision of an airflow path portion that extends towards the base portion of the housing to a transverse portion in which the vaporiser is provided may help to prevent or reduce leakage from the housing. Such an arrangement means that the airflow path includes at least one turn/deflection between the air inlet and the vaporiser. This makes it more difficult for any liquid in the vaporiser to pass from the vaporiser to the air inlet.

Further, the base portion may represent an in use lower end of the component and therefore, in a normal (typically upright) orientation of the component, gravity may prevent liquid from travelling up the first portion of the airflow path from the vaporiser to the air inlet.

Still further, the orientation of the heatable portion of the wick substantially parallel to the direction of airflow in the vaporiser is considered to contribute to the generation of a more desirable particle size and/or more homogeneous particle size distribution for the aerosol.

The air inlet may be longitudinally spaced from the base portion of the housing by a distance that is greater than <NUM>. The distance may be greater than <NUM>, or e.g. greater than <NUM>.

The airflow path may comprise a third portion extending longitudinally from the second portion to the outlet (formed in the mouthpiece portion). In this respect, a user may draw air into and along the airflow path by inhaling at the outlet (i.e. using the mouthpiece portion).

The third portion of the airflow path may be substantially parallel to the first portion of the airflow path. The third portion of the airflow path may be longer (i.e. in a longitudinal direction) than the first airflow path. The second portion of the airflow path may be substantially perpendicular to the first and/or third portions of the airflow path.

The airflow path may be generally U-shaped (the first and third portions forming stems of the "U" and the second portion forming the base of the "U"). In this respect, the second portion of the airflow path may connect the first and third portions of the airflow path. The airflow path may comprise at least two turns (e.g. each around about <NUM>°) between the vaporiser and the air inlet. The airflow path may comprise at least one turn between the vaporiser and the outlet.

The heatable portion of the wick is cylindrical in shape, preferably circularly cylindrical. The principal axis of the heatable portion of the wick may extend substantially parallel to the airflow direction in the second portion of the airflow path.

The second portion of the airflow path may have a length that is longer than the length of the heatable portion of the wick. This can ensure that the heatable portion of the wick is exposed to a substantially uniform airflow direction in the vaporiser.

The apparatus may have a bypass air inlet. The bypass air inlet may be provided into the third portion of the airflow path, downstream of the vaporiser. The provision of a bypass air inlet allows the flow conditions at the vaporiser to be suitable to generate particular particle size characteristics for the aerosol. In particular, for a particular flow rate through the apparatus, the provision of a bypass allows the flow rate through the vaporiser to be lower and therefore the velocity of the airflow at the wick and/or the turbulence intensity of the airflow at the wick to be lower. This is considered to be beneficial for the generation of useful particle size characteristics for the aerosol.

The apparatus comprises a tank for housing an aerosol precursor (e.g. a liquid aerosol precursor). The aerosol precursor may comprise an e-liquid, for example, comprising a base liquid and e.g. nicotine. The base liquid may include propylene glycol and/or vegetable glycerine. Hence, the apparatus may be a vaping smoking substitute apparatus.

The second portion of the airflow path may be disposed between (i.e. axially between) the tank and the base portion of the housing. The vaporiser may be disposed between the tank and the base portion of the housing. Thus, the wick may be disposed between the tank and the base portion of the housing.

The base portion of the housing may permit electrical contacts to extend through the base portion to the heater. Other than this, it is preferred that the base portion of the housing is sealed and therefore does not permit liquid to leak through it.

The housing may comprise a width, length and depth dimensions. The depth may be smaller than each of the width and the length. The wick may be oriented in the direction of the width dimension of the component.

The length of the housing may be greater than the width of the housing. The housing may be elongate, and the elongate axis may be in the length direction.

The housing may comprise opposing front and rear walls spaced by opposing first and second side walls extending therebetween. The distance between the side walls of the housing may define a width of the housing. The distance between the front and rear walls may define a depth of the housing. The width of the housing may be greater than the depth of the housing. The wick may be oriented so as to extend, at least in part, in a direction from the front wall to the rear wall.

The first portion of the airflow path may be defined within a first passage between a wall of the tank and a wall of the housing. The wall of the housing partly defining the first portion of the airflow path may be the first side wall of the housing. The wall of the tank defining the first portion of the airflow path may be a first tank wall. Thus the first portion of the airflow path/first passage may be defined between the first tank wall and the first side wall.

The third portion of the airflow path may be defined within a second passage between a wall of the tank and a wall of the housing. The wall of the housing partly defining the third portion of the airflow path may be the second side wall of the housing. The wall of the tank defining the third portion of the airflow path may be a second tank wall. Thus the third portion of the airflow path/second passage may be defined between the second tank wall and the second side wall.

The tank may be disposed between (in a transverse direction) the first and the third portions of the airflow path.

The first and second tank walls may be spaced from one another so as to define the tank therebetween. The first and second tank walls may extend longitudinally from the mouthpiece towards the base of the housing. The first and second tank walls may be substantially parallel. Each of the first and second tank walls may extend between (and span) the front and rear walls of the housing.

Each of the first and second tank walls may extend from the mouthpiece portion (i.e. internally in the housing). Each of the first and second tank walls may be integrally formed with the mouthpiece portion.

The tank may be partly defined by a wall of the housing (e.g. the front or rear wall).

The vaporiser may be disposed in a vaporising chamber. The vaporising chamber may form part of the airflow path (i.e. the second portion of the airflow path).

The vaporising chamber may be defined by one or more chamber walls. The wick may extend in a direction substantially parallel to a direction joining the first and second opposing chamber walls. The first and second chamber walls may separate (i.e. partially separate) the vaporising chamber from aerosol precursor in the tank. The first and second chamber walls may each comprise a respective opening through which a respective end of the wick projects such that the wick is fluid communication with aerosol precursor in the tank. In this way a central portion (heatable portion) of the wick may be exposed to fluid flow in airflow path and end portions of the wick may be in contact with aerosol precursor (e.g. e-liquid) stored in the tank. The wick may comprise a porous material. Thus, aerosol precursor may be drawn (e.g. by capillary action) along the wick, from the tank to the exposed portion of the wick.

A transverse chamber wall (e.g. a third wall) may separate the vaporising chamber from aerosol precursor in the tank. In this respect, the transverse chamber wall partly defines the tank. An opening may be provided in the transverse chamber wall for the flow of air into the aerosol precursor tank (i.e. so as to allow for pressure equalisation in the tank). Furthermore, the ends of the wick extend through the transverse chamber wall to be in contact with the aerosol precursor in the tank.

The vaporising chamber may be defined by an insert received into an open (e.g. lower) end of the housing. The chamber walls may be walls of the insert.

The heatable portion of the wick may be cylindrical. The heater may be a heating element which may be in the form of a filament wound about the heatable portion of the wick (e.g. the filament may extend helically about the wick). The filament may be wound about the heatable portion of the wick. The heating element may be electrically connected (or connectable) to a power source. Thus, in operation, the power source may supply electricity to (i.e. apply a voltage across) the heating element so as to heat the heating element. This may cause liquid stored in the wick (i.e. drawn from the tank) to be heated so as to form a vapour and become entrained in fluid flowing along the airflow path. This vapour may subsequently cool to form an aerosol in the airflow path (e.g. the third portion of the airflow path).

In a second aspect there is provided a smoking substitute system comprising a base unit, and a smoking substitute apparatus according to the first aspect, wherein the smoking substitute apparatus is removably engageable with the base unit.

In a third aspect there is provided a method of using a smoking substitute apparatus according to the first aspect to generate an aerosol.

Further optional features will now be set out. These may be applied singly or in any combination to any aspect.

The smoking substitute apparatus may be in the form of a consumable. The consumable may be configured for engagement with a main body. When the consumable is engaged with the main body, the combination of the consumable and the main body may form a smoking substitute system such as a closed smoking substitute system. For example, the consumable may comprise components of the system that are disposable, and the main body may comprise non-disposable or non-consumable components (e.g. power supply, controller, sensor, etc.) that facilitate the generation and/or delivery of aerosol by the consumable. In such an embodiment, the aerosol precursor (e.g. e-liquid) may be replenished by replacing a used consumable with an unused consumable.

Alternatively, the smoking substitute apparatus may be a non-consumable apparatus (e.g. that is in the form of an open smoking substitute system). In such embodiments an aerosol former (e.g. e-liquid) of the system may be replenished by re-filling, e.g. a reservoir of the smoking substitute apparatus, with the aerosol precursor (rather than replacing a consumable component of the apparatus).

In light of this, it should be appreciated that some of the features described herein as being part of the smoking substitute apparatus may alternatively form part of a main body for engagement with the smoking substitute apparatus. This may be the case in particular when the smoking substitute apparatus is in the form of a consumable.

Where the smoking substitute apparatus is in the form of a consumable, the main body and the consumable may be configured to be physically coupled together. For example, the consumable may be at least partially received in a recess of the main body, such that there is an interference fit between the main body and the consumable. Alternatively, the main body and the consumable may be physically coupled together by screwing one onto the other, or through a bayonet fitting, or the like.

Thus, the smoking substitute apparatus may comprise one or more engagement portions for engaging with a main body. In this way, one end of the smoking substitute apparatus may be coupled with the main body, whilst an opposing end of the smoking substitute apparatus may define a mouthpiece of the smoking substitute system.

The smoking substitute apparatus may comprise a reservoir (also referred to as a "tank" above) configured to store an aerosol precursor, such as an e-liquid. The e-liquid may, for example, comprise a base liquid. The e-liquid may further comprise nicotine. The base liquid may include propylene glycol and/or vegetable glycerine. The e-liquid may be substantially flavourless. That is, the e-liquid may not contain any deliberately added additional flavourant and may consist solely of a base liquid of propylene glycol and/or vegetable glycerine and nicotine.

The reservoir may be in the form of a tank. At least a portion of the tank may be light-transmissive. For example, the tank may comprise a window to allow a user to visually assess the quantity of e-liquid in the tank. A housing of the smoking substitute apparatus may comprise a corresponding aperture (or slot) or window that may be aligned with a light-transmissive portion (e.g. window) of the tank. The reservoir may be referred to as a "clearomizer" if it includes a window, or a "cartomizer" if it does not.

In operation, the power source may apply a voltage across the heating element so as to heat the heating element by resistive heating. This may cause liquid stored in the wick (i.e. drawn from the tank) to be heated so as to form a vapour and become entrained in air flowing through the passage. This vapour may subsequently cool to form an aerosol in the airflow path, typically downstream from the heating element.

In use, the user may puff on a mouthpiece of the smoking substitute apparatus, i.e. draw on the smoking substitute apparatus by inhaling, to draw in an air stream therethrough. A portion, or all, of the air stream (also referred to as a "main air flow") may pass through the vaporisation chamber so as to entrain the vapour generated at the heater. That is, such a main air flow may be heated by the heater (although typically only to a limited extent) as it passes through the vaporisation chamber. In addition, a portion of the air stream (also referred to as a "dilution air flow" or "bypass air flow") may bypass the vaporisation chamber and be directed to mix with the generated aerosol downstream from the vaporisation chamber. That is, the dilution air flow may be an air stream at an ambient temperature and may not be directly heated at all by the heater. The dilution air flow may combine with the main air flow for diluting the aerosol contained therein. The dilution air flow may merge with the main air flow along the passage downstream from the vaporisation chamber. Alternatively, the dilution air flow may be directly inhaled by the user without passing though the passage of the smoking substitute apparatus.

As a user puffs on the mouthpiece, vaporised e-liquid entrained in the passing air flow may be drawn towards the outlet of the passage. The vapour may cool, and thereby nucleate and/or condense along the passage to form a plurality of aerosol droplets, e.g. nicotine-containing aerosol droplets. A portion of these aerosol droplets may be delivered to and be absorbed at a target delivery site, e.g. a user's lung, whilst a portion of the aerosol droplets may instead adhere onto other parts of the user's respiratory tract, e.g. the user's oral cavity and/or throat. Typically, in some known smoking substitute apparatuses, the aerosol droplets as measured at the outlet of the passage, e.g. at the mouthpiece, may have a droplet size, d<NUM>, of less than <NUM>.

In some embodiments of the invention, the d<NUM> particle size of the aerosol particles is preferably at least <NUM>, more preferably at least <NUM> or at least <NUM>. Typically, the d<NUM> particle size is not more than <NUM>, preferably not more than <NUM>, not more than <NUM>, not more than <NUM>, not more than <NUM>, not more than <NUM>, not more than <NUM> or not more than <NUM>. It is considered that providing aerosol particle sizes in such ranges permits improved interaction between the aerosol particles and the user's lungs.

The median particle droplet size, d<NUM>, of an aerosol may be measured by a laser diffraction technique. For example, the stream of aerosol output from the outlet of the passage may be drawn through a Malvern Spraytec laser diffraction system, where the intensity and pattern of scattered laser light are analysed to calculate the size and size distribution of aerosol droplets. As will be readily understood, the particle size distribution may be expressed in terms of d<NUM>, d<NUM> and d<NUM>, for example. Considering a cumulative plot of the volume of the particles measured by the laser diffraction technique, the d<NUM> particle size is the particle size below which <NUM>% by volume of the sample lies. The d<NUM> particle size is the particle size below which <NUM>% by volume of the sample lies. The d<NUM> particle size is the particle size below which <NUM>% by volume of the sample lies. Unless otherwise indicated herein, the particle size measurements are volume-based particle size measurements, rather than number-based or mass-based particle size measurements.

The spread of particle size may be expressed in terms of the span, which is defined as (d<NUM>-d<NUM>)/d<NUM>. Typically, the span is not more than <NUM>, preferably not more than <NUM>, preferably not more than <NUM>, preferably not more than <NUM>, preferably not more than <NUM>, preferably not more than <NUM>, or not more than <NUM>.

The smoking substitute apparatus (or main body engaged with the smoking substitute apparatus) may comprise a power source. The power source may be electrically connected (or connectable) to a heater of the smoking substitute apparatus (e.g. when the smoking substitute apparatus is engaged with the main body). The power source may be a battery (e.g. a rechargeable battery). A connector in the form of e.g. a USB port may be provided for recharging this battery.

When the smoking substitute apparatus is in the form of a consumable, the smoking substitute apparatus may comprise an electrical interface for interfacing with a corresponding electrical interface of the main body. One or both of the electrical interfaces may include one or more electrical contacts. Thus, when the main body is engaged with the consumable, the electrical interface of the main body may be configured to transfer electrical power from the power source to a heater of the consumable via the electrical interface of the consumable.

The electrical interface of the smoking substitute apparatus may also be used to identify the smoking substitute apparatus (in the form of a consumable) from a list of known types. For example, the consumable may have a certain concentration of nicotine and the electrical interface may be used to identify this. The electrical interface may additionally or alternatively be used to identify when a consumable is connected to the main body.

Again, where the smoking substitute apparatus is in the form of a consumable, the main body may comprise an identification means, which may, for example, be in the form of an RFID reader, a barcode or QR code reader. This identification means may be able to identify a characteristic (e.g. a type) of a consumable engaged with the main body. In this respect, the consumable may include any one or more of an RFID chip, a barcode or QR code, or memory within which is an identifier and which can be interrogated via the identification means.

The smoking substitute apparatus or main body may comprise a controller, which may include a microprocessor. The controller may be configured to control the supply of power from the power source to the heater of the smoking substitute apparatus (e.g. via the electrical contacts). A memory may be provided and may be operatively connected to the controller. The memory may include non-volatile memory. The memory may include instructions which, when implemented, cause the controller to perform certain tasks or steps of a method.

The main body or smoking substitute apparatus may comprise a wireless interface, which may be configured to communicate wirelessly with another device, for example a mobile device, e.g. via Bluetooth®. To this end, the wireless interface could include a Bluetooth® antenna. Other wireless communication interfaces, e.g. WiFi®, are also possible. The wireless interface may also be configured to communicate wirelessly with a remote server.

A puff sensor may be provided that is configured to detect a puff (i.e. inhalation from a user). The puff sensor may be operatively connected to the controller so as to be able to provide a signal to the controller that is indicative of a puff state (i.e. puffing or not puffing). The puff sensor may, for example, be in the form of a pressure sensor or an acoustic sensor. That is, the controller may control power supply to the heater of the consumable in response to a puff detection by the sensor. The control may be in the form of activation of the heater in response to a detected puff. That is, the smoking substitute apparatus may be configured to be activated when a puff is detected by the puff sensor. When the smoking substitute apparatus is in the form of a consumable, the puff sensor may be provided in the consumable or alternatively may be provided in the main body.

The term "flavourant" is used to describe a compound or combination of compounds that provide flavour and/or aroma. For example, the flavourant may be configured to interact with a sensory receptor of a user (such as an olfactory or taste receptor). The flavourant may include one or more volatile substances.

The flavourant may be provided in solid or liquid form. The flavourant may be natural or synthetic. For example, the flavourant may include menthol, liquorice, chocolate, fruit flavour (including e.g. citrus, cherry etc.), vanilla, spice (e.g. ginger, cinnamon) and tobacco flavour. The flavourant may be evenly dispersed or may be provided in isolated locations and/or varying concentrations.

The present inventors consider that a flow rate of <NUM> min-' is towards the lower end of a typical user expectation of flow rate through a conventional cigarette and therefore through a user-acceptable smoking substitute apparatus. The present inventors further consider that a flow rate of <NUM> min-' is towards the higher end of a typical user expectation of flow rate through a conventional cigarette and therefore through a user-acceptable smoking substitute apparatus. Embodiments of the present invention therefore provide an aerosol with advantageous particle size characteristics across a range of flow rates of air through the apparatus.

The aerosol may have a Dv50 of at least <NUM>, at least <NUM>, at least <NUM>, at least <NUM>, at least <NUM>, at least <NUM>, at least <NUM>, at least <NUM>, at least <NUM> or at least <NUM>.

The aerosol may have a Dv50 of not more than <NUM>, not more than <NUM>, not more than <NUM>, not more than <NUM>, not more than <NUM>, not more than <NUM>, not more than <NUM>, not more than <NUM>, not more than <NUM>, not more than <NUM>, not more than <NUM>, not more than <NUM>, not more than <NUM>, not more than <NUM>, not more than <NUM>, not more than <NUM>, not more than <NUM>, not more than <NUM>, not more than <NUM> or not more than <NUM>.

A particularly preferred range for Dv50 of the aerosol is in the range <NUM>-<NUM>.

The air inlet, flow passage, outlet and the vaporisation chamber may be configured so that, when the air flow rate inhaled by the user through the apparatus is <NUM> min-<NUM>, the average magnitude of velocity of air in the vaporisation chamber is in the range <NUM>-<NUM>-<NUM>. The average magnitude velocity of air may be calculated based on knowledge of the geometry of the vaporisation chamber and the flow rate.

When the air flow rate inhaled by the user through the apparatus is <NUM> min-<NUM>, the average magnitude of velocity of air in the vaporisation chamber may be at least <NUM>-<NUM>, or at least <NUM>-<NUM>, or at least <NUM>-<NUM>, or at least <NUM>-<NUM>.

When the air flow rate inhaled by the user through the apparatus is <NUM> min-<NUM>, the average magnitude of velocity of air in the vaporisation chamber may be at most <NUM>-<NUM>, at most <NUM>-<NUM>, at most <NUM>-<NUM>, at most <NUM>-<NUM>, at most <NUM>-<NUM>, at most <NUM>-<NUM> or at most <NUM>-<NUM>.

When the calculated average magnitude of velocity of air in the vaporisation chamber is in the ranges specified, it is considered that the resultant aerosol particle size is advantageously controlled to be in a desirable range. It is further considered that the configuration of the apparatus can be selected so that the average magnitude of velocity of air in the vaporisation chamber can be brought within the ranges specified, at the exemplary flow rate of <NUM> min-<NUM> and/or the exemplary flow rate of <NUM> min-<NUM>.

The aerosol generator may comprise a vaporiser element loaded with aerosol precursor, the vaporiser element being heatable by a heater and presenting a vaporiser element surface to air in the vaporisation chamber. A vaporiser element region may be defined as a volume extending outwardly from the vaporiser element surface to a distance of <NUM> from the vaporiser element surface.

The air inlet, flow passage, outlet and the vaporisation chamber may be configured so that, when the air flow rate inhaled by the user through the apparatus is <NUM> min-<NUM>, the average magnitude of velocity of air in the vaporiser element region is in the range <NUM>-<NUM>-<NUM>. The average magnitude of velocity of air in the vaporiser element region may be calculated using computational fluid dynamics.

When the air flow rate inhaled by the user through the apparatus is <NUM> min-<NUM>, the average magnitude of velocity of air in the vaporiser element region may be at least <NUM>-<NUM>, or at least <NUM>-<NUM>, or at least <NUM>-<NUM>, or at least <NUM>-<NUM>.

When the air flow rate inhaled by the user through the apparatus is <NUM> min-<NUM>, the average magnitude of velocity of air in the vaporiser element region may be at most <NUM>-<NUM>, at most <NUM>-<NUM>, at most <NUM>-<NUM>, at most <NUM>-<NUM>, at most <NUM>-<NUM> or at most <NUM>-<NUM>.

When the average magnitude of velocity of air in the vaporiser element region is in the ranges specified, it is considered that the resultant aerosol particle size is advantageously controlled to be in a desirable range. It is further considered that the velocity of air in the vaporiser element region is more relevant to the resultant particle size characteristics than consideration of the velocity in the vaporisation chamber as a whole. This is in view of the significant effect of the velocity of air in the vaporiser element region on the cooling of the vapour emitted from the vaporiser element surface.

Additionally or alternatively is it relevant to consider the maximum magnitude of velocity of air in the vaporiser element region.

Therefore, the air inlet, flow passage, outlet and the vaporisation chamber may be configured so that, when the air flow rate inhaled by the user through the apparatus is <NUM> min-<NUM>, the maximum magnitude of velocity of air in the vaporiser element region is in the range <NUM>-<NUM>-<NUM>.

When the air flow rate inhaled by the user through the apparatus is <NUM> min-<NUM>, the maximum magnitude of velocity of air in the vaporiser element region may be at least <NUM>-<NUM>, or at least <NUM>-<NUM>, or at least <NUM>-<NUM>, or at least <NUM>-<NUM>.

When the air flow rate inhaled by the user through the apparatus is <NUM> min-', the maximum magnitude of velocity of air in the vaporiser element region may be at most <NUM>-<NUM>, at most <NUM>-<NUM>, at most <NUM>-<NUM>, at most <NUM>-<NUM>, at most <NUM>-<NUM>, at most <NUM>-<NUM>, at most <NUM>-<NUM> or at most <NUM>-<NUM>.

The air inlet, flow passage, outlet and the vaporisation chamber may be configured so that, when the air flow rate inhaled by the user through the apparatus is <NUM> min-<NUM>, the maximum magnitude of velocity of air in the vaporiser element region is in the range <NUM>-<NUM>-<NUM>.

When the air flow rate inhaled by the user through the apparatus is <NUM> min-<NUM>, the maximum magnitude of velocity of air in the vaporiser element region may be at most <NUM>-<NUM>, at most <NUM>-<NUM>, at most <NUM>-<NUM>, at most <NUM>-<NUM>, at most <NUM>-<NUM>, at most <NUM>-<NUM>, at most <NUM>-<NUM> or at most <NUM>-<NUM>.

It is considered that configuring the apparatus in a manner to permit such control of velocity of the airflow at the vaporiser permits the generation of aerosols with particularly advantageous particle size characteristics, including Dv50 values.

Additionally or alternatively is it relevant to consider the turbulence intensity in the vaporiser chamber in view of the effect of turbulence on the particle size of the generated aerosol. For example, the air inlet, flow passage, outlet and the vaporisation chamber may be configured so that, when the air flow rate inhaled by the user through the apparatus is <NUM> min-<NUM>, the turbulence intensity in the vaporiser element region is not more than <NUM>%.

When the air flow rate inhaled by the user through the apparatus is <NUM> min-<NUM>, the turbulence intensity in the vaporiser element region may be not more than <NUM>%, not more than <NUM>%, not more than <NUM>%, not more than <NUM>%, not more than <NUM>%, not more than <NUM>%, not more than <NUM>% or not more than <NUM>%.

It is considered that configuring the apparatus in a manner to permit such control of the turbulence intensity in the vaporiser element region permits the generation of aerosols with particularly advantageous particle size characteristics, including Dv50 values.

Following detailed investigations, the inventors consider, without wishing to be bound by theory, that the particle size characteristics of the generated aerosol may be determined by the cooling rate experienced by the vapour after emission from the vaporiser element (e.g. wick). In particular, it appears that imposing a relatively slow cooling rate on the vapour has the effect of generating aerosols with a relatively large particle size. The parameters discussed above (velocity and turbulence intensity) are considered to be mechanisms for implementing a particular cooling dynamic to the vapour.

More generally, it is considered that the air inlet, flow passage, outlet and the vaporisation chamber may be configured so that a desired cooling rate is imposed on the vapour. The particular cooling rate to be used depends of course on the nature of the aerosol precursor and other conditions. However, for a particular aerosol precursor it is possible to define a set of testing conditions in order to define the cooling rate, and by extension this imposes limitations on the configuration of the apparatus to permit such cooling rates as are shown to result in advantageous aerosols. Accordingly, the air inlet, flow passage, outlet and the vaporisation chamber may be configured so that the cooling rate of the vapour is such that the time taken to cool to <NUM> is not less than <NUM>, when tested according to the following protocol. The aerosol precursor is an e-liquid consisting of <NUM>% freebase nicotine and the remainder a <NUM>:<NUM> propylene glycol and vegetable glycerine mixture, the e-liquid having a boiling point of <NUM>. Air is drawn into the air inlet at a temperature of <NUM>. The vaporiser is operated to release a vapour of total particulate mass <NUM> over a <NUM> second duration from the vaporiser element surface in an air flow rate between the air inlet and outlet of <NUM> min-'.

Additionally or alternatively, the air inlet, flow passage, outlet and the vaporisation chamber may be configured so that the cooling rate of the vapour is such that the time taken to cool to <NUM> is not less than <NUM>, when tested according to the following protocol. The aerosol precursor is an e-liquid consisting of <NUM>% freebase nicotine and the remainder a <NUM>:<NUM> propylene glycol and vegetable glycerine mixture, the e-liquid having a boiling point of <NUM>. Air is drawn into the air inlet at a temperature of <NUM>. The vaporiser is operated to release a vapour of total particulate mass <NUM> over a <NUM> second duration from the vaporiser element surface in an air flow rate between the air inlet and outlet of <NUM> min-'.

Cooling of the vapour such that the time taken to cool to <NUM> is not less than <NUM> corresponds to an equivalent linear cooling rate of not more than <NUM>/ms.

The equivalent linear cooling rate of the vapour to <NUM> may be not more than <NUM>/ms, not more than <NUM>/ms, not more than <NUM>/ms, not more than <NUM>/ms or not more than <NUM>/ms.

The testing protocol set out above considers the cooling of the vapour (and subsequent aerosol) to a temperature of <NUM>. This is a temperature which can be considered to be suitable for an aerosol to exit the apparatus for inhalation by a user without causing significant discomfort. It is also possible to consider cooling of the vapour (and subsequent aerosol) to a temperature of <NUM>. Although this temperature is possibly too high for comfortable inhalation, it is considered that the particle size characteristics of the aerosol are substantially settled by the time the aerosol cools to this temperature (and they may be settled at still higher temperature).

Accordingly, the air inlet, flow passage, outlet and the vaporisation chamber may be configured so that the cooling rate of the vapour is such that the time taken to cool to <NUM> is not less than <NUM>, when tested according to the following protocol. The aerosol precursor is an e-liquid consisting of <NUM>% freebase nicotine and the remainder a <NUM>:<NUM> propylene glycol and vegetable glycerine mixture, the e-liquid having a boiling point of <NUM>. Air is drawn into the air inlet at a temperature of <NUM>. The vaporiser is operated to release a vapour of total particulate mass <NUM> over a <NUM> second duration from the vaporiser element surface in an air flow rate between the air inlet and outlet of <NUM> min-'.

The equivalent linear cooling rate of the vapour to <NUM> may be not more than <NUM>/ms, not more than <NUM>/ms, not more than <NUM>/ms, not more than <NUM>/ms, not more than <NUM>/ms, not more than <NUM>/ms, not more than <NUM>/ms, not more than <NUM>/ms, not more than <NUM>/ms, not more than <NUM>/ms, not more than <NUM>/ms, not more than <NUM>/ms, not more than <NUM>/ms, not more than <NUM>/ms, not more than <NUM>/ms, not more than <NUM>/ms, not more than <NUM>/ms, not more than <NUM>/ms, not more than <NUM>/ms or not more than <NUM>/ms.

It is considered that configuring the apparatus in a manner to permit such control of the cooling rate of the vapour permits the generation of aerosols with particularly advantageous particle size characteristics, including Dv50 values.

Further background to the present invention and further aspects and embodiments of the present invention will now be discussed with reference to the accompanying figures.

<FIG> illustrate a smoking substitute system in the form of an e-cigarette system <NUM>. The system <NUM> comprises a main body <NUM> of the system <NUM>, and a smoking substitute apparatus in the form of an e-cigarette consumable (or "pod") <NUM>. In the illustrated arrangement the consumable <NUM> (sometimes referred to herein as a smoking substitute apparatus) is removable from the main body <NUM>, so as to be a replaceable component of the system <NUM>. The e-cigarette system <NUM> is a closed system in the sense that it is not intended that the consumable should be refillable with e-liquid by a user.

As is apparent from <FIG>, the consumable <NUM> is configured to engage the main body <NUM>. <FIG> shows the main body <NUM> and the consumable <NUM> in an engaged state, whilst <FIG> shows the main body <NUM> and the consumable <NUM> in a disengaged state. When engaged, a portion of the consumable <NUM> is received in a cavity of corresponding shape in the main body <NUM> and is retained in the engaged position by way of a snap-engagement mechanism. In other embodiments, the main body <NUM> and consumable <NUM> may be engaged by screwing one into (or onto) the other, or through a bayonet fitting, or by way of an interference fit.

The system <NUM> is configured to vaporise an aerosol precursor, which in the illustrated arrangement is in the form of a nicotine-based e-liquid <NUM>. The e-liquid <NUM> comprises nicotine and a base liquid including propylene glycol and/or vegetable glycerine. In the present embodiment, the e-liquid <NUM> is flavoured by a flavourant. In other embodiments, the e-liquid <NUM> may be flavourless and thus may not include any added flavourant.

<FIG> shows a schematic longitudinal cross sectional view of the smoking substitute apparatus forming part of the smoking substitute system shown in <FIG>. In <FIG>, the e-liquid <NUM> is stored within a reservoir in the form of a tank <NUM> that forms part of the consumable <NUM>. In the illustrated embodiment, the consumable <NUM> is a "single-use" consumable <NUM>. That is, upon exhausting the e-liquid <NUM> in the tank <NUM>, the intention is that the user disposes of the entire consumable <NUM>. The term "single-use" does not necessarily mean the consumable is designed to be disposed of after a single smoking session. Rather, it defines the consumable <NUM> is not arranged to be refilled after the e-liquid contained in the tank <NUM> is depleted. The tank may include a vent (not shown) to allow ingress of air to replace e-liquid that has been used from the tank. The consumable <NUM> preferably includes a window <NUM> (see <FIG>), so that the amount of e-liquid in the tank <NUM> can be visually assessed. The main body <NUM> includes a slot <NUM> so that the window <NUM> of the consumable <NUM> can be seen whilst the rest of the tank <NUM> is obscured from view when the consumable <NUM> is received in the cavity of the main body <NUM>. The consumable <NUM> may be referred to as a "clearomizer" when it includes a window <NUM>, or a "cartomizer" when it does not.

In some arrangements, the e-liquid (i.e. aerosol precursor) may be the only part of the system that is truly "single-use". That is, the tank may be refillable with e-liquid or the e-liquid may be stored in a non-consumable component of the system. For example, in such arrangements, the e-liquid may be stored in a tank located in the main body or stored in another component that is itself not single-use (e.g. a refillable cartomizer).

The external wall of tank <NUM> is provided by a casing of the consumable <NUM>. The tank <NUM> annularly surrounds, and thus defines a portion of, a passage <NUM> that extends between a vaporiser inlet <NUM> and an outlet <NUM> at opposing ends of the consumable <NUM>. In this respect, the passage <NUM> comprises an upstream end at the end of the consumable <NUM> that engages with the main body <NUM>, and a downstream end at an opposing end of the consumable <NUM> that comprises a mouthpiece <NUM> of the system <NUM>.

When the consumable <NUM> is received in the cavity of the main body <NUM> as shown in <FIG>, a plurality of device air inlets <NUM> are formed at the boundary between the casing of the consumable and the casing of the main body. The device air inlets <NUM> are in fluid communication with the vaporiser inlet <NUM> through an inlet flow channel <NUM> formed in the cavity of the main body which is of corresponding shape to receive a part of the consumable <NUM>. Air from outside of the system <NUM> can therefore be drawn into the passage <NUM> through the device air inlets <NUM> and the inlet flow channels <NUM>.

When the consumable <NUM> is engaged with the main body <NUM>, a user can inhale (i.e. take a puff) via the mouthpiece <NUM> so as to draw air through the passage <NUM>, and so as to form an airflow (indicated by the dashed arrows in <FIG>) in a direction from the vaporiser inlet <NUM> to the outlet <NUM>. Although not illustrated, the passage <NUM> may be partially defined by a tube (e.g. a metal tube) extending through the consumable <NUM>. In <FIG>, for simplicity, the passage <NUM> is shown with a substantially circular cross-sectional profile with a constant diameter along its length. In other embodiments, the passage may have other cross-sectional profiles, such as oval shaped or polygonal shaped profiles. Further, in other embodiments, the cross sectional profile and the diameter (or hydraulic diameter) of the passage may vary along its longitudinal axis.

The smoking substitute system <NUM> is configured to vaporise the e-liquid <NUM> for inhalation by a user. To provide this operability, the consumable <NUM> comprises a heater having a porous wick <NUM> and a resistive heating element in the form of a heating filament <NUM> that is helically wound (in the form of a coil) around a portion of the porous wick <NUM>. The porous wick <NUM> extends across the passage <NUM> (i.e. transverse to a longitudinal axis of the passage <NUM> and thus also transverse to the air flow along the passage <NUM> during use) and opposing ends of the wick <NUM> extend into the tank <NUM> (so as to be immersed in the e-liquid <NUM>). In this way, e-liquid <NUM> contained in the tank <NUM> is conveyed from the opposing ends of the porous wick <NUM> to a central portion of the porous wick <NUM> so as to be exposed to the airflow in the passage <NUM>.

The helical filament <NUM> is wound about the exposed central portion of the porous wick <NUM> and is electrically connected to an electrical interface in the form of electrical contacts <NUM> mounted at the end of the consumable that is proximate the main body <NUM> (when the consumable and the main body are engaged). When the consumable <NUM> is engaged with the main body <NUM>, electrical contacts <NUM> make contact with corresponding electrical contacts (not shown) of the main body <NUM>. The main body electrical contacts are electrically connectable to a power source (not shown) of the main body <NUM>, such that (in the engaged position) the filament <NUM> is electrically connectable to the power source. In this way, power can be supplied by the main body <NUM> to the filament <NUM> in order to heat the filament <NUM>. This heats the porous wick <NUM> which causes e-liquid <NUM> conveyed by the porous wick <NUM> to vaporise and thus to be released from the porous wick <NUM>. The vaporised e-liquid becomes entrained in the airflow and, as it cools in the airflow (between the heated wick and the outlet <NUM> of the passage <NUM>), condenses to form an aerosol. This aerosol is then inhaled, via the mouthpiece <NUM>, by a user of the system <NUM>. As e-liquid is lost from the heated portion of the wick, further e-liquid is drawn along the wick from the tank to replace the e-liquid lost from the heated portion of the wick.

The filament <NUM> and the exposed central portion of the porous wick <NUM> are positioned across the passage <NUM>. More specifically, the part of passage that contains the filament <NUM> and the exposed portion of the porous wick <NUM> forms a vaporisation chamber. In the illustrated example, the vaporisation chamber has the same cross-sectional diameter as the passage <NUM>. However, in some arrangements the vaporisation chamber may have a different cross sectional profile compared with the passage <NUM>. For example, the vaporisation chamber may have a larger cross sectional diameter than at least some of the downstream part of the passage <NUM> so as to enable a longer residence time for the air inside the vaporisation chamber.

<FIG> illustrates in more detail the vaporisation chamber and therefore the region of the consumable <NUM> around the wick <NUM> and filament <NUM>. The helical filament <NUM> is wound around a central portion of the porous wick <NUM>. The porous wick extends across passage <NUM>. E-liquid <NUM> contained within the tank <NUM> is conveyed as illustrated schematically by arrows <NUM>, i.e. from the tank and towards the central portion of the porous wick <NUM>.

When the user inhales, air is drawn from through the inlets <NUM> shown in <FIG>, along inlet flow channel <NUM> to vaporisation chamber inlet <NUM> and into the vaporisation chamber containing porous wick <NUM>. The porous wick <NUM> extends substantially transverse to the airflow direction. The airflow passes around the porous wick, at least a portion of the airflow substantially following the surface of the porous wick <NUM>. In examples where the porous wick has a cylindrical cross-sectional profile, the airflow may follow a curved path around an outer periphery of the porous wick <NUM>.

At substantially the same time as the airflow passes around the porous wick <NUM>, the filament <NUM> is heated so as to vaporise the e-liquid which has been wicked into the porous wick. The airflow passing around the porous wick <NUM> picks up this vaporised e-liquid, and the vapour-containing airflow is drawn in direction <NUM> further down passage <NUM>.

The power source of the main body <NUM> may be in the form of a battery (e.g. a rechargeable battery such as a lithium ion battery). The main body <NUM> may comprise a connector in the form of e.g. a USB port for recharging this battery. The main body <NUM> may also comprise a controller that controls the supply of power from the power source to the main body electrical contacts (and thus to the filament <NUM>). That is, the controller may be configured to control a voltage applied across the main body electrical contacts, and thus the voltage applied across the filament <NUM>. In this way, the filament <NUM> may only be heated under certain conditions (e.g. during a puff and/or only when the system is in an active state). In this respect, the main body <NUM> may include a puff sensor (not shown) that is configured to detect a puff (i.e. inhalation). The puff sensor may be operatively connected to the controller so as to be able to provide a signal, to the controller, which is indicative of a puff state (i.e. puffing or not puffing). The puff sensor may, for example, be in the form of a pressure sensor or an acoustic sensor.

Although not shown, the main body <NUM> and consumable <NUM> may comprise a further interface which may, for example, be in the form of an RFID reader, a barcode or QR code reader. This interface may be able to identify a characteristic (e.g. a type) of a consumable <NUM> engaged with the main body <NUM>. In this respect, the consumable <NUM> may include any one or more of an RFID chip, a barcode or QR code, or memory within which is an identifier and which can be interrogated via the interface.

In the reference arrangements described above based on <FIG>, the heatable portion of the wick is arranged transversely to the direction of the airflow in the vaporiser (vaporisation chamber). However, the present inventors have realised that there are advantages to arranging the airflow path and the orientation of the heatable portion of the wick differently.

<FIG> shows a longitudinal cross sectional view of a smoking substitute apparatus <NUM> according to a first aspect. The drawing is schematic. It is intended that this apparatus is configured for use with a main body substantially as shown in <FIG>. Air flow through the apparatus is illustrated using straight arrows.

The air inlet <NUM> of the apparatus <NUM> is in the form of an aperture formed in the first side wall <NUM> of the housing <NUM>. In particular, the air inlet <NUM> is spaced along the first side wall <NUM> (in a longitudinal direction) from the base <NUM> of the housing <NUM> so as to be partway along the first side wall <NUM> from the base <NUM>. The outlet <NUM> is formed in the mouthpiece <NUM> and an airflow path extends from the air inlet <NUM> to the outlet <NUM>, such that a user can draw air through the airflow path by inhaling at the outlet <NUM>. As will be described in more detail below, the airflow path follows a generally U-shaped path through the apparatus <NUM>.

The airflow path comprises first, second and third airflow path portions. The first airflow path portion is defined by a first passage <NUM> extending longitudinally from the air inlet <NUM> towards the base <NUM> of the apparatus <NUM>. This first passage <NUM> is defined between a first tank wall <NUM> that is laterally spaced from the first side wall <NUM> (in which the air inlet <NUM> is formed) and that extends generally parallel to the first side wall <NUM>.

The third airflow path is similarly defined by a third passage <NUM> that is formed between a second tank wall <NUM> and the second side wall <NUM>. The second tank wall <NUM> is laterally spaced from and generally parallel to the second side wall <NUM>. Both the first <NUM> and second <NUM> tank walls span the front and rear walls (not shown) of the housing <NUM>. In this way, the tank <NUM> is partly defined between the first and second tank walls <NUM>, <NUM>, an upper wall <NUM> and the front and rear walls.

The second airflow path portion is in the form of a vaporising chamber <NUM> that extends transversely across the lower part of the housing <NUM> so as to connect lower ends of the first <NUM> and second <NUM> airflow passages. Thus, upon inhalation by a user, air may flow into the air inlet <NUM>, through the first passage <NUM>, through the vaporising chamber <NUM> (where vapour may be entrained in the air) and subsequently through the third passage <NUM> and on to where it is discharged (into a user's mouth) from the outlet <NUM> at the mouthpiece <NUM>, in communication with an upper end of the third passage <NUM>. Thus, the airflow path comprises at least two turns (at the air inlet <NUM> and the connection between the vaporising chamber <NUM> and the first passage <NUM>) between the vaporiser chamber <NUM> and the air inlet <NUM>. This may reduce the propensity for leakage of e-liquid out of the air inlet <NUM> (i.e. from the vaporising chamber <NUM>).

The vaporiser is located in the vaporising chamber <NUM> and comprises a porous wick <NUM> and a heater filament <NUM> coiled around the porous wick <NUM>. The heatable portion of the wick <NUM> (i.e. that part of the wick that has the heater filament <NUM> coiled around it) extends along the vaporising chamber <NUM> (substantially parallel to the direction of airflow through the vaporising chamber <NUM>). That is, the wick <NUM> extends in the width direction of the housing <NUM>.

The vaporising chamber <NUM> is bounded at its upper limit by a base wall of the tank and at its lower limit by the base <NUM> of the housing <NUM>.

The ends of the wick <NUM> are inserted through apertures in the base wall of the tank in order to allow the wick to be saturated with aerosol precursor (e-liquid) for communication along the wick to the heatable portion of the wick. In this way, the ends of the wick <NUM> are in contact with aerosol precursor (e-liquid) stored in the tank <NUM>. This e-liquid is transported along the wick <NUM> (e.g. by capillary action) to the heatable portion of the wick <NUM> that is exposed to airflow flowing through the vaporising chamber <NUM>. The transported e-liquid is heated by the heater filament <NUM> (when activated e.g. by detection of inhalation), which causes the e-liquid to be vaporised and to be entrained in air flowing along the wick <NUM>. This vaporised liquid may cool to form an aerosol in the vaporising chamber <NUM>, or in the third passage <NUM>, which may then be inhaled by a user.

The base of the apparatus accommodates the electrical interface of the apparatus. The electrical interface comprises two electrical contacts that are electrically connected to the heating filament <NUM>. In this way, when the apparatus is engaged with the main body, power can be supplied from the power source of the main body to the heating filament <NUM>.

<FIG> shows a second embodiment, which is a modification of <FIG>. The features of <FIG> corresponding to those in <FIG> are not described again. In <FIG>, there is provided a bypass air inlet, through the second side wall <NUM> into the third passage <NUM>. The provision of a bypass airflow allows the air flow in the vaporisation chamber to be more gentle (and therefore less turbulent and with lower velocity) for a particular total flow rate through the device than for <FIG>. This permits the generation of an aerosol with a larger particle size and with a tighter particle size distribution.

In the description above, it is explained that the shape and orientation of the first passage combined with the vaporisation chamber reduces the risk of e-liquid leakage. The shape of the third passage combined with the vaporisation chamber has corresponding advantages. In particular, there is a risk of e-liquid spitting from the heated wick. There is no straight line path from the wick to the outlet and therefore any drops of e-liquid emitted in this way should hit an internal wall of the apparatus rather than reach the outlet. Spitting and condensed e-liquid flow down to accumulate below the wick. This reduces the chance of the air inlet and/or outlet becoming blocked. E-liquid below the wick evaporates during operation of the apparatus due to radiative heat from the heater.

The inventors have considered the effect of the relative orientation of the heatable portion of the wick and the airflow direction in the vaporisation chamber. <FIG> shows the results of modelling on the velocity field of airflow and the volume fraction of vapour for a reference arrangement (left hand side) in which the air flow direction is perpendicular to the axis of the wick and for an embodiment (right hand side) in which the air flow direction is parallel to the axis of the wick.

Where the airflow direction is perpendicular to the wick (as shown on the left in <FIG>), there is a significant difference in conditions at the leading face of the wick compared to the trailing face of the wick. At the leading face, the vapour volume fraction is low, indicating that the vapour has condensed into an aerosol quickly as it is carried away from the wick. At the trailing face, the vapour volume fraction is high, indicating that the vapour is more slowly condensing into the aerosol. This modelling therefore shows that the cooling rate experienced by the vapour is significantly different at different parts of the wick. It is considered that cooling rate has a very significant effect on the particle size and particle size distribution of the aerosol. Therefore these differences in cooling rate are expected to lead to a broad particle size distribution.

Where the airflow direction is parallel to the wick (as shown on the right in <FIG>), conditions at the parts of the wick emitting vapour are more uniform. As can be seen, the vapour volume fraction is spatially relatively uniform along the wick. Therefore the vapour condenses relatively uniformly, independent of position along the wick. This modelling therefore shows that the cooling rate experienced by the vapour is relatively uniform at different parts of the wick. This is therefore considered to lead to a narrow particle size distribution. The heating and flow conditions in the vaporisation chamber can furthermore be controlled (in part by the use of a bypass if necessary) in order to generate an aerosol with a relatively large particle size, for example with dv50 in the range <NUM>-<NUM>.

There now follows a disclosure of certain experimental work undertaken to determine the effects of certain conditions in the smoking substitute apparatus on the particle size of the generated aerosol.

The experimental work reported here has relevance to one or more of the embodiments disclosed above, for example in view of the effects demonstrated on the particle size of the generated aerosol based on control of the flow conditions at the wick, such as when a bypass airflow is implemented.

Aerosol droplet size is a considered to be an important characteristic for smoking substitution devices. Droplets in the range of <NUM>-<NUM> are preferred in order to achieve improved nicotine delivery efficiency and to minimise the hazard of second-hand smoking. However, at the time of writing (September <NUM>), commercial EVP devices typically deliver aerosols with droplet size averaged around <NUM>, and to the knowledge of the inventors not a single commercially available device can deliver an aerosol with an average particle size exceeding <NUM>.

The present inventors speculate, without themselves wishing to be bound by theory, that there has to date been a lack of understanding in the mechanisms of e-liquid evaporation, nucleation and droplet growth in the context of aerosol generation in smoking substitute devices. The present inventors have therefore studied these issues in order to provide insight into mechanisms for the generation of aerosols with larger particles. The present inventors have carried out experimental and modelling work alongside theoretical investigations, leading to significant achievements as now reported.

This disclosure considers the roles of air velocity, air turbulence and vapour cooling rate in affecting aerosol particle size.

In this work, a Malvern PANalytical Spraytec laser diffraction system was employed for the particle size measurement. In order to limit the number of variables, the same coil and wick (<NUM> ohms Ni-Cr coil, <NUM> Y07 cotton wick), the same e-liquid (<NUM>% freebase nicotine, <NUM>:<NUM> propylene glycol (PG)/vegetable glycerine (VG) ratio, no added flavour) and the same input power (10W) were used in all experiments. Y07 represents the grade of cotton wick, meaning that the cotton has a linear density of <NUM> grams per meter.

Particle sizes were measured in accordance with ISO <NUM>:<NUM>(E), which is an international standard on laser diffraction methods for particle size analysis. This is particularly well suited to aerosols, because there is an assumption in this standard that the particles are spherical (which is a good assumption for liquid-based aerosols). The standard is stated to be suitable for particle sizes in the range <NUM> micron to <NUM>.

The results presented here concentrate on the volume-based median particle size Dv50. This is to be taken to be the same as the parameter d<NUM> used above.

The work reported here based on the inventors' insight that aerosol particle size might be related to: <NUM>) air velocity; <NUM>) flow rate; and <NUM>) Reynolds number. In a given EVP device, these three parameters are interlinked to each other, making it difficult to draw conclusions on the roles of each individual factor. In order to decouple these factors, experiments were carried out using a set of rectangular tubes having different dimensions. These were manufactured by 3D printing. The rectangular tubes were 3D printed in an MJP <NUM>3D printer. <FIG> illustrates the set of rectangular tubes. Each tube has the same depth and length but different width. Each tube has an integral end plate in order to provide a seal against air flow outside the tube. Each tube also has holes formed in opposing side walls in order to accommodate a wick.

<FIG> shows a schematic perspective longitudinal cross sectional view of an example rectangular tube <NUM> with a wick <NUM> and heater coil <NUM> installed. The location of the wick is about halfway along the length of the tube. This is intended to allow the flow of air along the tube to settle before reaching the wick.

<FIG> shows a schematic transverse cross sectional view an example rectangular tube <NUM> with a wick <NUM> and heater coil <NUM> installed. In this example, the internal width of the tube is <NUM>
The rectangular tubes were manufactured to have same internal depth of <NUM> in order to accommodate the standardized coil and wick, however the tube internal width varied from <NUM> to <NUM>. In this disclosure, the "tube size" is referred to as the internal width of rectangular tubes.

The rectangular tubes with different dimensions were used to generate aerosols that were tested for particle size in a Malvern PANalytical Spraytec laser diffraction system. An external digital power supply was dialled to <NUM>. 6A constant current to supply 10W power to the heater coil in all experiments. Between two runs, the wick was saturated manually by applying one drop of e-liquid on each side of the wick.

Three groups of experiments were carried out in this study:.

Table <NUM> shows a list of experiments in this study. The values in "calculated air velocity" column were obtained by simply dividing the flow rate by the intersection area at the centre plane of wick. Reynolds numbers (Re) were calculated through the following equation: <MAT> where: ρ is the density of air (<NUM>/m<NUM>); v is the calculated air velocity in table <NUM>; µ is the viscosity of air (<NUM> × <NUM>-<NUM> m<NUM>/s); L is the characteristic length calculated by: <MAT> where: P is the perimeter of the flow path's intersection, and A is the area of the flow path's intersection.

Five repetition runs were carried out for each tube size and flow rate combination. Between adjacent runs there were at least <NUM> minutes wait time for the Spraytec system to be purged. In each run, real time particle size distributions were measured in the Spraytec laser diffraction system at a sampling rate of <NUM> per second, the volume distribution median (Dv50) was averaged over a puff duration of <NUM> seconds. Measurement results were averaged and the standard deviations were calculated to indicate errors as shown in section <NUM> below.

The Reynolds numbers in Table <NUM> are all well below <NUM>, therefore, it is considered fair to assume all the experiments in section <NUM> would be under conditions of laminar flow. Further experiments were carried out and reported in this section to investigate the role of turbulence.

Turbulence intensity was introduced as a quantitative parameter to assess the level of turbulence. The definition and simulation of turbulence intensity is discussed below (see section <NUM>).

Different device designs were considered in order to introduce turbulence. In the experiments reported here, jetting panels were added in the existing <NUM> rectangular tubes upstream of the wick. This approach enables direct comparison between different devices as they all have highly similar geometry, with turbulence intensity being the only variable.

<FIG> show air flow streamlines in the four devices used in this turbulence study. <FIG> is a standard <NUM> rectangular tube with wick and coil installed as explained in the previous section, with no jetting panel. <FIG> has a jetting panel located <NUM> below (upstream from) the wick. <FIG> has the same jetting panel <NUM> below the wick. <FIG> has the same jetting panel <NUM> below the wick. As can be seen from <FIG>, the jetting panel has an arrangement of apertures shaped and directed in order to promote jetting from the downstream face of the panel and therefore to promote turbulent flow. Accordingly, the jetting panel can introduce turbulence downstream, and the panel causes higher level of turbulence near the wick when it is positioned closer to the wick. As shown in <FIG>, the four geometries gave turbulence intensities of <NUM>%, <NUM>%, <NUM>% and <NUM>%, respectively, with <FIG> being the least turbulent, and <FIG> being the most turbulent.

For each of <FIG>, there are shown three modelling images. The image on the left shows the original image (colour in the original), the central image shows a greyscale version of the image and the right hand image shows a black and white version of the image. As will be appreciated, each version of the image highlights slightly different features of the flow. Together, they give a reasonable picture of the flow conditions at the wick.

These four devices were operated to generate aerosols following the procedure explained above (section <NUM>) using a flow rate of <NUM> Ipm and the generated aerosols were tested for particle size in the Spraytec laser diffraction system.

This experiment aimed to investigate the influence of inflow air temperature on aerosol particle size, in order to investigate the effect of vapour cooling rate on aerosol generation.

The experimental set up is shown in <FIG>. The testing used a Carbolite Gero EHA 12300B tube furnace <NUM> with a quartz tube <NUM> to heat up the air. Hot air in the tube furnace was then led into a transparent housing <NUM> that contains the EVP device <NUM> to be tested. A thermocouple meter <NUM> was used to assess the temperature of the air pulled into the EVP device. Once the EVP device was activated, the aerosol was pulled into the Spraytec laser diffraction system <NUM> via a silicone connector <NUM> for particle size measurement.

Three smoking substitute apparatuses (referred to as "pods") were tested in the study: pod <NUM> is the commercially available "myblu optimised" pod (<FIG>); pod <NUM> is a pod featuring an extended inflow path upstream of the wick (<FIG>); and pod <NUM> is pod with the wick located in a stagnant vaporisation chamber and the inlet air bypassing the vaporisation chamber but entraining the vapour from an outlet of the vaporisation chamber (<FIG>).

Pod <NUM>, shown in longitudinal cross sectional view (in the width plane) in <FIG>, has a main housing that defines a tank 160x holding an e-liquid aerosol precursor. Mouthpiece 154x is formed at the upper part of the pod. Electrical contacts 156x are formed at the lower end of the pod. Wick 162x is held in a vaporisation chamber. The air flow direction is shown using arrows.

Pod <NUM>, shown in longitudinal cross sectional view (in the width plane) in <FIG>, has a main housing that defines a tank 160y holding an e-liquid aerosol precursor. Mouthpiece 154y is formed at the upper part of the pod. Electrical contacts 156y are formed at the lower end of the pod. Wick 162y is held in a vaporisation chamber. The air flow direction is shown using arrows. Pod <NUM> has an extended inflow path (plenum chamber 157y) with a flow conditioning element 159y, configured to promote reduced turbulence at the wick 162y.

<FIG> shows a schematic longitudinal cross sectional view of pod <NUM>. <FIG> shows a schematic longitudinal cross sectional view of the same pod <NUM> in a direction orthogonal to the view taken in <FIG>. Pod <NUM> has a main housing that defines a tank 160z holding an e-liquid aerosol precursor. Mouthpiece 154z is formed at the upper part of the pod. Electrical contacts 156z are formed at the lower end of the pod. Wick 162z is held in a vaporisation chamber. The air flow direction is shown using arrows. Pod <NUM> uses a stagnant vaporiser chamber, with the air inlets bypassing the wick and picking up the vapour/aerosol downstream of the wick.

All three pods were filled with the same e-liquid (<NUM>% freebase nicotine, <NUM>:<NUM> PG/VG ratio, no added flavour). Three experiments were carried out for each pod: <NUM>) standard measurement in ambient temperature; <NUM>) only the inlet air was heated to <NUM>; and <NUM>) both the inlet air and the pods were heated to <NUM>. Five repetition runs were carried out for each experiment and the Dv50 results were taken and averaged.

In this study, modelling work was performed using COMSOL Multiphysics <NUM>, engaged physics include:
<NUM>) laminar single-phase flow; <NUM>) turbulent single-phase flow; <NUM>) laminar two-phase flow; <NUM>) heat transfer in fluids; and (<NUM>) particle tracing. Data analysis and data visualisation were mostly completed in MATLAB R2019a.

Air velocity in the vicinity of the wick is believed to play an important role in affecting particle size. In section <NUM>, the air velocity was calculated by dividing the flow rate by the intersection area, which is referred to as "calculated velocity" in this work. This involves a very crude simplification that assumes velocity distribution to be homogeneous across the intersection area.

In order to increase reliability of the work, computational fluid dynamics (CFD) modelling was performed to obtain more accurate velocity values:.

<NUM>) The average velocity in the vicinity of the wick (defined as a volume from the wick surface to <NUM> away from the wick surface)
<NUM>) The maximum velocity in the vicinity of the wick (defined as a volume from the wick surface to <NUM> away from the wick surface).

The CFD model uses a laminar single-phase flow setup. For each experiment, the outlet was configured to a corresponding flowrate, the inlet was configured to be pressure-controlled, the wall conditions were set as "no slip". A <NUM> wide ring-shaped domain (wick vicinity) was created around the wick surface, and domain probes were implemented to assess the average and maximum magnitudes of velocity in this ring-shaped wick vicinity domain.

The CFD model outputs the average velocity and maximum velocity in the vicinity of the wick for each set of experiments carried out in section <NUM>. The outcomes are reported in Table <NUM>.

Turbulence intensity (I) is a quantitative value that represents the level of turbulence in a fluid flow system. It is defined as the ratio between the root-mean-square of velocity fluctuations, u', and the Reynolds-averaged mean flow velocity, U: <MAT> where ux, uy and uz are the x-, y- and z-components of the velocity vector, ux, uy, and uz represent the average velocities along three directions.

Higher turbulence intensity values represent higher levels of turbulence. As a rule of thumb, turbulence intensity below <NUM>% represents a low-turbulence case, turbulence intensity between <NUM>% and <NUM>% represents a medium-turbulence case, and turbulence intensity above <NUM>% represents a high-turbulence case.

In this study, turbulence intensity was obtained from CFD simulation using turbulent single-phase setup in COMSOL Multiphysics. For each of the four experiments explained in section <NUM>, the outlet was set to <NUM> Ipm, the inlet was set to be pressure-controlled, and all wall conditions were set to be "no slip".

Turbulence intensity was assessed within the volume up to <NUM> away from the wick surface (defined as the wick vicinity domain). For the four experiments explained in section <NUM>, the turbulence intensities are <NUM>%, <NUM>%, <NUM>% and <NUM>%, respectively, as also shown in <FIG>.

The cooling rate modelling involves three coupling models in COMSOL Multiphysics: <NUM>) laminar two-phase flow; <NUM>) heat transfer in fluids, and <NUM>) particle tracing. The model is setup in three steps:.

A wave of <NUM> particles were release from wick surface at t = <NUM> second after the two-phase flow and heat transfer model has stabilised. The particle tracing physics has one-way coupling with the previous model, which means the fluid flow exerts dragging force on the particles, whereas the particles do not exert counterforce on the fluid flow. Therefore, the particles function as moving probes to output vapour temperature at each timestep.

The model outputs average vapour temperature at each time steps. A MATLAB script was then created to find the time step when the vapour cools to a target temperature (<NUM> or <NUM>), based on which the vapour cooling rates were obtained (Table <NUM>).

Particle size measurement results for the rectangular tube testing are shown in Table <NUM>. For every tube size and flow rate combination, five repetition runs were carried out in the Spraytec laser diffraction system. The Dv50 values from five repetition runs were averaged, and the standard deviations were calculated to indicate errors, as shown in Table <NUM>.

In this section, the roles of different factors affecting aerosol particle size will be discussed based on experimental and modelling results.

The particle size (Dv50) experimental results are plotted against calculated air velocity in <FIG>. The graph shows a strong correlation between particle size and air velocity.

Different size tubes were tested at two flow rates: <NUM> Ipm and <NUM> Ipm. Both groups of data show the same trend that slower air velocity leads to larger particle size. The conclusion was made more convincing by the fact that these two groups of data overlap well in <FIG>: for example, the <NUM> tube delivered an average Dv50 of <NUM> when tested at <NUM> Ipm flow rate, and the <NUM> tube delivered a highly similar average Dv50 of <NUM> when tested at <NUM> Ipm flow rate, as they have similar air velocity of <NUM> and <NUM>/s, respectively.

In addition, <FIG> shows the results of three experiments with highly different setup arrangements: <NUM>) <NUM> tube measured at <NUM> Ipm flow rate with Reynolds number of <NUM>; <NUM>) <NUM> tube measured at <NUM> Ipm flow rate with Reynolds number of <NUM>; and <NUM>) <NUM> tube measured at <NUM> Ipm flow rate with Reynolds number of <NUM>. It is relevant that these setup arrangements have one similarity: the air velocities are all calculated to be <NUM>/s. <FIG> shows that, although these three sets of experiments have different tube sizes, flow rates and Reynolds numbers, they all delivered similar particle sizes, as the air velocity was kept constant. These three data points were also plotted out in <FIG> (<NUM>/s data with star marks) and they tie in nicely into particle size-air velocity trendline.

The above results lead to a strong conclusion that air velocity is an important factor affecting the particle size of EVP devices. Relatively large particles are generated when the air travels with slower velocity around the wick. It can also be concluded that flow rate, tube size and Reynolds number are not necessarily independently relevant to particle size, providing the air velocity is controlled in the vicinity of the wick.

In <FIG> the "calculated velocity" was obtained by dividing the flow rate by the intersection area, which is a crude simplification that assumes a uniform velocity field. In order to increase reliability of the work, CFD modelling has been performed to assess the average and maximum velocities in the vicinity of the wick. In this study, the "vicinity" was defined as a volume from the wick surface up to <NUM> away from the wick surface.

The particle size measurement data were plotted against the average velocity (<FIG>) and maximum velocity (<FIG>) in the vicinity of the wick, as obtained from CFD modelling.

The data in these two graphs indicates that in order to obtain an aerosol with Dv50 larger than <NUM>, the average velocity should be less than or equal to <NUM>/s in the vicinity of the wick and the maximum velocity should be less than or equal to <NUM>/s in the vicinity of the wick.

Furthermore, in order to obtain an aerosol with Dv50 of <NUM> or larger, the average velocity should be less than or equal to <NUM>/s in the vicinity of the wick and the maximum velocity should be less than or equal to <NUM>/s in the vicinity of the wick.

It is considered that typical commercial EVP devices deliver aerosols with Dv50 around <NUM>, and there is no commercially available device that can deliver aerosol with Dv50 exceeding <NUM>. It is considered that typical commercial EVP devices have average velocity of <NUM>-<NUM>/s in the vicinity of the wick.

The role of turbulence has been investigated in terms of turbulence intensity, which is a quantitative characteristic that indicates the level of turbulence. In this work, four tubes of different turbulence intensities were used to general aerosols which were measured in the Spraytec laser diffraction system. The particle size (Dv50) experimental results are plotted against turbulence intensity in <FIG>.

The graph suggests a correlation between particle size and turbulence intensity, that lower turbulence intensity is beneficial for obtaining larger particle size. It is noted that when turbulence intensity is above <NUM>% (medium-turbulence case), there are relatively large measurement fluctuations. In <FIG>, the tube with a jetting panel <NUM> below the wick has the largest error bar, because air jets become unpredictable near the wick after traveling through a long distance.

The results clearly indicate that laminar air flow is favourable for the generation of aerosols with larger particles, and that the generation of large particle sizes is jeopardised by introducing turbulence. In <FIG>, the <NUM> standard rectangular tube (without jetting panel) delivers above <NUM> particle size (Dv50). The particle size values reduced by at least a half when jetting panels were added to introduce turbulence.

<FIG> shows the high temperature testing results. Larger particle sizes were observed from all <NUM> pods when the temperature of inlet air increased from room temperature (<NUM>) to <NUM>. When the pods were heated as well, two of the three pods saw even larger particle size measurement results, while pod <NUM> was unable to be measured due to significant amount of leakage.

Without wishing to be bound by theory, the results are in line with the inventors' insight that control over the vapour cooling rate provides an important degree of control over the particle size of the aerosol. As reported above, the use of a slow air velocity can have the result of the formation of an aerosol with large Dv50. It is considered that this is due to slower air velocity allowing a slower cooling rate of the vapour.

Another conclusion related to laminar flow can also be explained by a cooling rate theory: laminar flow allows slow and gradual mixing between cold air and hot vapour, which means the vapour can cool down in slower rate when the airflow is laminar, resulting in larger particle size.

The results in <FIG> further validate this cooling rate theory: when the inlet air has higher temperature, the temperature difference between hot vapour and cold air becomes smaller, which allows the vapour to cool down at a slower rate, resulting in larger particle size; when the pods were heated as well, this mechanism was exaggerated even more, leading to an even slower cooling rate and an even larger particle size.

In section <NUM>, the vapour cooling rates for each tube size and flow rate combination were obtained via multiphysics simulation. In <FIG> and <FIG>, the particle size measurement results were plotted against vapour cooling rate to <NUM> and <NUM>, respectively.

The data in these graphs indicates that in order to obtain an aerosol with Dv50 larger than <NUM>, the apparatus should be operable to require more than <NUM> for the vapour to cool to <NUM>, or an equivalent (simplified to an assumed linear) cooling rate being slower than <NUM>/ms. From an alternative viewpoint, in order to obtain an aerosol with Dv50 larger than <NUM>, the apparatus should be operable to require more than <NUM> for the vapour to cool to <NUM>, or an equivalent (simplified to an assumed linear) cooling rate slower than <NUM>/ms.

Furthermore, in order to obtain an aerosol with Dv50 of <NUM> or larger, the apparatus should be operable to require more than <NUM> for the vapour to cool to <NUM>, or an equivalent (simplified to an assumed linear) cooling rate being slower than <NUM>/ms. From an alternative viewpoint, in order to obtain an aerosol with Dv50 of <NUM> or larger, the apparatus should be operable to require more than <NUM> for the vapour to cool to <NUM>, or an equivalent (simplified to an assumed linear) cooling rate slower than <NUM>/ms.

In this work, particle size (Dv50) of aerosols generated in a set of rectangular tubes was studied in order to decouple different factors (flow rate, air velocity, Reynolds number, tube size) affecting aerosol particle size. It is considered that air velocity is an important factor affecting particle size - slower air velocity leads to larger particle size. When air velocity was kept constant, the other factors (flow rate, Reynolds number, tube size) has low influence on particle size.

The role of turbulence was also investigated. It is considered that laminar air flow favours generation of large particles, and introducing turbulence deteriorates (reduces) the particle size.

Modelling methods were used to simulate the average air velocity, the maximum air velocity, and the turbulence intensity in the vicinity of the wick. A COMSOL model with three coupled physics has also been developed to obtain the vapour cooling rate.

All experimental and modelling results support a cooling rate theory that slower vapour cooling rate is a significant factor in ensuring larger particle size. Slower air velocity, laminar air flow and higher inlet air temperature lead to larger particle size, because they all allow vapour to cool down at slower rates.

While the invention has been described in conjunction with the exemplary embodiments described above, many variations will be apparent to those skilled in the art when given this disclosure. Accordingly, the exemplary embodiments of the invention set forth above are considered to be illustrative and not limiting. Various changes to the described embodiments may be made without departing from the scope of the invention.

Claim 1:
A smoking substitute apparatus (<NUM>) comprising:
a housing (<NUM>) comprising a base portion (<NUM>), a mouthpiece portion (<NUM>), and one or more walls (<NUM>, <NUM>) extending longitudinally from the base portion (<NUM>) towards the mouthpiece portion (<NUM>);
an air inlet (<NUM>) formed in a wall of the housing (<NUM>) and spaced longitudinally from the base portion (<NUM>);
an outlet (<NUM>) formed in the mouthpiece portion (<NUM>);
an airflow path extending from the air inlet (<NUM>) to the outlet (<NUM>), the airflow path comprising a first portion downstream of the air inlet (<NUM>) and extending longitudinally towards the base portion (<NUM>) of the housing (<NUM>), and a transversely extending second portion that is downstream of the first portion;
a tank (<NUM>) for housing an aerosol precursor, wherein a transverse chamber wall partly defines the tank; and
a vaporiser provided in the transversely extending second portion and comprising a wick (<NUM>) and a heating element (<NUM>) for heating a heatable portion of the wick, the heatable portion of the wick being cylindrical in shape and elongated in a direction substantially parallel to the direction of airflow in the second portion of the airflow path and wherein ends of the wick extend through the transverse chamber wall to be in contact with the aerosol precursor in the tank.