question: why the flame on my gas camping stove gets smaller towards the end of the bottle until it finally runs out rather than being the same size until suddenly becomes empty
comment: The contents of the cylinder are pressurized. When there is less gas, there is less pressure, resulting in a smaller flame.
passages: This explains why there is no sound when the flame is heating the gauze: all air flowing through the tube is heated by the flame, so when it reaches the gauze, it is already hot and no pressure increase takes place.
   Variations in local propagation speed of a laminar flame arise due to what is called flame stretch. Flame stretch can happen due to the straining by outer flow velocity field or the curvature of flame; the difference in the propagation speed from the corresponding laminar speed is a function of these effects and may be written as:
  
  where formula_27 is the laminar flame thickness, formula_28 is the flame curvature, formula_29 is the unit normal on the flame surface pointing towards the unburnt gas side, formula_30 is the flow velocity and formula_31 are the respective Markstein numbers of curvature and strain.
   In a Bunsen flame, a steady flow rate is provided which matches the flame speed so as to stabilize the flame. If the flow rate is below the flame speed, the flame will move upstream until the fuel is consumed or until it encounters a flame holder. If the flow rate is equal to the flame speed, we would expect a stationary flat flame front normal to the flow direction. If the flow rate is above the flame speed, the flame front will become conical such that the component of the velocity vector normal to the flame front is equal to the flame speed.
   Section::::Premixed flame configuration.:Stagnation flame.
  
  Here, the pre-mixed gases flow in such a way so as to form a region of stagnation (zero velocity) where the flame may be stabilized.
  
  Section::::Premixed flame configuration.:Spherical flame.
  
  In this configuration, the flame is typically initiated by way of a spark within a homogeneous pre-mixture. The subsequent propagation of the developed premixed flame occurs as a spherical front until the mixture is transformed entirely or the walls of the combustion vessel are reached.
  
  Section::::Applications.
   A turbulent premixed flame can be assumed to propagate as a surface composed of an ensemble of laminar flames so long as the processes that determine the inner structure of the flame are not affected. Under such conditions, the flame surface is wrinkled by virtue of turbulent motion in the premixed gases increasing the surface area of the flame. The wrinkling process increases the burning velocity of the turbulent premixed flame in comparison to its laminar counterpart.
  
  The propagation of such a premixed flame may be analysed using the field equation called as G equation for a scalar formula_32 as:
   Studies of solid single- and double-base propellant reactions suggest a series of zones or phases as the reaction proceeds from the surface into the solid. The deepest portion of the solid experiencing heat transfer melts and begins phase transition from solid to gas in a "foam zone". The gaseous propellant decomposes into simpler molecules in a surrounding "fizz zone". Energy is released in a luminous outer "flame zone" where the simpler gas molecules react to form conventional combustion products like steam and carbon monoxide. Propellants designed for a minimum heat transfer pressure may fail to sustain the "flame zone" at lower pressures.
   The underlying flame physics can be understood with the help of an idealized model consisting of a uniform one-dimensional tube of unburnt and burned gaseous fuel, separated by a thin transitional region of width formula_1 in which the burning occurs. The burning region is commonly referred to as the flame or flame front. In equilibrium, thermal diffusion across the flame front is balanced by the heat supplied by burning.
  
  Two characteristic timescales are important here. The first is the thermal diffusion timescale formula_2, which is approximately equal to
   Piobert's law
  
  Piobert's law applies to the reaction of solid propellant grains to generate hot gas. It is stated: "Burning takes place by parallel layers where the surface of the grain regresses, layer by layer, normal to the surface at every point."
  
  Section::::History.
   Since the time averaged pressure is equal at all points of the tube, it is not straightforward to explain the different flame heights. The flame height is proportional to the gas flow as shown in the figure. Based on Bernoulli's principle, the gas flow is proportional to the square root of the pressure difference between the inside and outside of the tube. This is shown in the figure for a tube without standing sound wave. Based on this argument, the flame height depends non-linearly on the local, time-dependent pressure. The time average of the flow is reduced at the points with oscillating pressure and thus flames are lower.
   Diffusion flames can be laminar diffusion flames (e.g. candles and matches burning in the air etc.) or turbulent diffusion flames (e.g. furnaces, turbo-machinery, some liquid-fuel rocket engines and internal combustion engines) depending on the nature of mixed gas flow. Further, the flame shapes of this kind of burning are divided into two categories oxygen-rich diffusion flames and oxygen-deficient. Flame shapes also depend on the discharging velocity of fuel and air. Eddies inside the air flow plays an important role in deciding the flame shapes. With increase in discharging velocity of fuel into the air laminar diffusion flames tends to become turbulent diffusion flames. This leads to an increase in the flame height and finally it gains a maximum height (critical limit). After this limit further increase in the jet velocity of the fuel adds to instability of turbulent flame. The position where laminar flame is changing into turbulent flame is termed as "break-up point". Increase in jet velocity after critical limit results in decrease of the whole flame height. Beyond this point the height of the break-up point reaches a certain value where even after increasing the jet velocity of fuel the flame height will not change. Studies by Hawthorne et al. prove that the chemical reaction rates in turbulent diffusion flames and in laminar diffusion flames are almost similar.
   Section::::Disadvantages.
  
  The disadvantages of Steady Laminar Flamelet model due to above mentioned reason are:
  
  1. It does not account for the curvature effects which can change the flame structure and is more detrimental while the structure hasn’t reached the quasi-steady state.
  
  2. Such transient effects also arise in turbulent flow, the scalar dissipation experience a sudden change. As the flame structure take time to get stabilize.
  
  To improve the above SLFM models, few more models has been proposed like Transient laminar flamelet model ( TLFM) by Ferreira .
  
  Section::::Further reading.
   Under contrasting conditions, however, the inner structure of the premixed flame may be entirely disrupted causing the flame to extinguish either locally (known as local extinction) or globally (known as global extinction or blow-off). Such opposing cases govern the operation of practical combustion devices such as SI engines as well as aero-engine afterburners. The prediction of the extent to which the inner structure of flame is affected in turbulent flow is a topic of extensive research.
  
  Section::::Premixed flame configuration.
  
  The flow configuration of premixed gases affects the stabilization and burning characteristics of the
  
  Section::::Premixed flame configuration.:Bunsen flame.
   Flame cutting (firearms)
  
  Flame cutting is a destructive phenomenon that occurs in some firearms (usually revolvers) as a result of hot gases under high pressure.
   BULLET::::3. When a liquid boils it turns into a gas. The resulting gas takes up far more space than the liquid did.
   A premixed flame is a flame formed under certain conditions during the combustion of a premixed charge (also called pre-mixture) of fuel and oxidiser. Since the fuel and oxidiser—the key chemical reactants of combustion—are available throughout a homogeneous stoichiometric premixed charge, the combustion process once initiated sustains itself by way of its own heat release. The majority of the chemical transformation in such a combustion process occurs primarily in a thin interfacial region which separates the unburned and the burned gases. The premixed flame interface propagates through the mixture until the entire charge is depleted. The propagation speed of a premixed flame is known as the flame speed (or burning velocity) which depends on the convection-diffusion-reaction balance within the flame, i.e. on its inner chemical structure. The premixed flame is characterised as laminar or turbulent depending on the velocity distribution in the unburned pre-mixture (which provides the medium of propagation for the flame).
   One experimental study has suggested that the effect is caused by the ionization process occurring mostly at the base of the flame, making it more difficult for the electrode further from the base of the flame to attract positive ions from the burner, yet leaving the electron current largely unchanged with distance because of the greater mobility of the electron charge carriers.
  
  Section::::See also.
  
  BULLET::::- Flame detection
  
  BULLET::::- Flame supervision device
  
  Section::::External links.
  
  BULLET::::- A video of a flame being used as a rectifier in a simple AM radio
  
  BULLET::::- Using a flame as a triode amplifier
   The size of the flame can be adjusted to a limited extent by the valves on the torch and by the regulator settings, but in the main it depends on the size of the orifice in the tip. In fact, the tip should be chosen first according to the job at hand, and then the regulators set accordingly.
  
  Section::::Types of flame.:Welding.
   To use the stove, a small amount of fuel (preferably 2% salicylic acid in alcohol) is poured into the stove and ignited. The pot is then placed above the stove, on a windscreen or stand. The flame is small at first, only burning from the inner chamber. Once the fuel has warmed up (requiring about one minute) its vapor will pass through the perforations and form a ring of flame. Enough heat from the flame is passed to the fuel to maintain full combustion until the fuel runs out.
  
  Section::::Operation and performance.:Ratings.
   Flame arresters should be used only in the gas group and conditions they have been designed and tested for. Since the depth on an arrester is specified for certain conditions, changes in the temperature, pressure, or composition of the gases entering the arrester can cause the flame spatial velocity to increase, making the design of the arrester insufficient to stop the flame front ("propagation"). The deflagration may continue downstream of the arrester.
   The extra carbon product will cause soot to form, and the less oxygen used, the more soot will form. There are other unbalanced ratios where incomplete combustion products such as carbon monoxide (CO) are formed, such as:
  
  Section::::Complete and incomplete combustion.:Flame temperature.
   Under certain conditions, mainly in terms of geometrical conditions (such as partial confinement and many obstacles in the flame path that cause turbulent flame eddy currents), a subsonic flame may accelerate to supersonic speed, transitioning from deflagration to detonation. The exact mechanism is not fully understood,
  
  and while existing theories are able to explain and model both deflagrations and detonations, there is no theory at present which can predict the transition phenomenon.
  
  Section::::Examples.
  
  A deflagration to detonation transition has been a feature of several major industrial accidents:
  
  BULLET::::- 1970 Propane vapour cloud explosion in Port Hudson
  
  BULLET::::- Flixborough disaster
   Whereas in a usual flame molecules break down to small fragments and combine with oxygen producing carbon dioxide (i.e. burn), in a cool flame, the fragments are relatively large and easily recombine with each other. Therefore, much less heat, light and carbon dioxide is released; the combustion process is oscillatory and can sustain for a long time. A typical temperature increase upon ignition of a cool flame is a few tens of degrees Celsius whereas it is on the order of 1000 °C for a conventional flame. 
   Other factors, particularly the fuel chemistry and its propensity for forming soot, have an influence on luminosity.
  
  The Victorian chemist, Edward Frankland, studied luminosity in flames and discovered that their luminosity also increased with pressure.
  
  Section::::Bunsen burner.
  
  One of the most familiar instances of a luminous flame is produced by a Bunsen burner. This burner has a controllable air supply and a constant gas jet: when the air supply is reduced, a highly luminous, and thus visible, orange 'safety flame' is produced. For heating work, the air inlet is opened and the burner produces a much hotter blue flame.
   Detonation flame arresters made by most manufacturers employ layers of metal ribbons with crimped corrugations. The internal narrow passages of the crimped corrugations make up the element matrix. These passages are measured as the hydraulic diameter and are made smaller for gases having smaller maximum experimental safe gaps (MESG).
  
  Under normal operating conditions the flame arrester permits a relatively free flow of gas or vapor through the piping system. If the mixture is ignited and the flame begins to travel back through the piping, the arrester will prohibit the flame from moving back to the gas source.
   The heat transfer rate of smokeless propellants increases with pressure; so the rate of gas generation from a given grain surface area increases at higher pressures. Accelerating gas generation from fast burning propellants may rapidly create a destructively high pressure spike before bullet movement increases reaction volume. Conversely, propellants designed for a minimum heat transfer pressure may cease decomposition into gaseous reactants if bullet movement decreases pressure before a slow burning propellant has been consumed. Unburned propellant grains may remain in the barrel if the energy-releasing "flame zone" cannot be sustained in the resultant absence of gaseous reactants from the inner zones.
  
raw_presuppositions: Gas should come out of a camping stove at the same rate until it runs out. Gas should come out of a bottle at the same rate until it runs out.
raw_corrections: When there is less gas, there is less pressure, resulting in a smaller flame. When there is less gas, there is less pressure, resulting in a smaller flame.