Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
  • F23C—METHODS OR APPARATUS FOR COMBUSTION USING FLUID FUEL OR SOLID FUEL SUSPENDED IN  A CARRIER GAS OR AIR 
  • F23C15/00—Apparatus in which combustion takes place in pulses influenced by acoustic resonance in a gas mass
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
  • F23N—REGULATING OR CONTROLLING COMBUSTION
  • F23N5/00—Systems for controlling combustion
  • F23N5/16—Systems for controlling combustion using noise-sensitive detectors

Definitions

• the present invention relates to a method and device for supervision and control of a heat generator with pulsa- ting combustion.
• a heat generator of this type can be constructed m different ways, but m an exemplary commercially available variation it comprises a Helmholtz resonator with a reso- nant chamber arranged as a combustion chamber, a pulse tube connected to the combustion chamber at one of its ends, a decoupler with an exhaust pipe being connected to its other end, an inlet chamber with an initiation blower, a valve controlled by the pulse pressure m the combustion chamber for regulating the connection between the inlet chamber and the combustion chamber, a device for injecting fuel m the combustion chamber, and an ignition device for igniting the fuel m the combustion chamber.
• the initiation blower When this heat generator is to be started or m tia- ted, the initiation blower is started, which sucks m air m the inlet chamber and creates a certain overpressure, whereupon an ignition device (a spark plug) is activated, at the same time as fuel is injected, so that the fuel is ignited and herewith a rythmic movement of the valve can commence.
• an ignition device a spark plug
• a heat generator of the type mentioned above must have a completely dependable supervision system, which determines whether it is operative or not . In a conventional furnace with an open fire this can occur by means of a photocell or the like, but m a pulsating heat generator supervision may be difficult to attain.
• SE-B-462 661 it is known to utilize the frequency of the pressure variations for this purpose.
• the pressure variations m the inlet chamber are sensed, and their frequency is compared with a predetermined frequency, so that the ignition device and the initiation blower can be shut down, when the frequency of the pressure variations shows a requisite conformity with the predetermined frequency.
• a furnace or heat generator has a certain resonant frequency for physical reasons, and this frequency is dependent on the construction and te pe- rature of the furnace, type and quality of the fuel and air surplus, and so on.
• the frequency does not give a clear indication of the function of the heat generator; it would be advantageous to have a better signal of the generator function. It has also m practice appeared that the method with frequence measurement caused great problems m that an initiation which should have been approved has not actually been approved.
• a better way of supervising and controlling a heat generator or furnace of this kind is according to the invention attained m that the amplitude of the sound generated during the operation of the heat generator and/or the gas pressure is sensed and that the initiation means or electrical operative system of the heat generator is shut down, when the amplitude reaches a predetermined value or falls outside a predetermined area, respectively.
• the shut down should here occur with a certain delay, so that for example singular pressure increases and explosions m the furnace are not taken as an indication of approved operation or do not lead to the shut down of the furnace .
• the amplitude m the inlet chamber is sensed and the ignition device and the initiation blower are shut down, when the amplitude reaches a predetermined value.
• a supervising and controlling device for carrying out the method according to the invention has an electronic circuit device for emitting a signal for shutting down the initiation means or a signal for shutting down the electrical operative system of the heat generator at the receipt from a sensor of an amplitude signal over a predetermined value or outside a predetermined area.
• This circuit device is preferably supplemented with a delay circuit .
• the electronic circuit device can be supplemented with an adaptation unit.
• the circuit device can m such a case be phantom fed with current from the fire controller.
• the senor can be arranged m the inlet chamber, and the initiation means can comprise the ignition device and the initiation blower.
• the pressure connection of the sensor can here be provided with a snorkel, which extends down to the bottom of the inlet chamber. Oil or water which possibly leaks m will hereby lead to a shut down of the furnace, as the measured amplitude hereby decreases.
• the invention is based on the principle that the sensor senses the amplitude for the sound generated at the combustion.
• the sensor therefore needs not be placed m the inlet chamber of the furnace - even if this is the preferred position - but may for example alternatively be posi- tioned m the combustion chamber itself, between the fur- nace body and the outer shell of the furnace or even completely outside the furnace.
• the supervision and control of the pulsating genera- tor need not only cover the initiation, but it can be equally essential to shut off the electric operative system of the generator, when the sensed amplitude falls outside a predetermined area, which indicates that the operation of the furnace is defective.
• the invention is equally applicable to all types of pulsating heat generators and is not limited to use at the embodiment chosen as an example.
• Fig 1 s a very diagrammatic vertical sectional view of a heat gene- rator with pulsating combustion
• Figs 2 and 3 are block diagrams of two embodiments of supervising and controlling devices according to the invention.
• the heat generator of the present type shown m Fig 1 which works with pulse combustion according to a previously known technique, is disposed m a water tank 10 with an inlet 11 and an outlet 12 for the water, which m a known way shall be circulated m a water based heating system.
• the heat generator comprises a Helmholtz resonator with a resonant chamber 13 and a pulse tube 14, which is connected to the resonant chamber at one of its ends .
• the resonant chamber forms the combustion chamber of the heat generator and is provided with a nozzle 15 for the supply of gaseous, liquid or fluidized fuel via a magnet valve 16 and with a spark plug 17, connected to an initiation transformer 17A.
• An inlet chamber 18 is connected to the combustion chamber through an air inlet 19, which is controlled by a valve 20.
• the valve is arranged to operate m an automatic fashion for alternately closing at a supra-atmosphe- ric pressure m the combustion chamber and opening at a sub-atmospheric pressure therein m a rythmical movement
• the inlet chamber communicates with the external air through an inlet 21, which is provided with an initiation blower 22, via a silencer and/or a filter.
• the other end of the pulse tube is connected to a decoupler 23 having an exhaust pipe 24 connected to a chimney or other flue .
• the fuel injected m the combustion chamber 13 is ignited when entering the hot combustion chamber and will be burnt up m combination with the oxygen present m the combustion chamber, which results m a supra-atmospheric pressure and a closing of the valve 20 as a result of said supra-atmospheric pressure.
• the valve 20 is reopened to allow an inflow of air in the combustion chamber from the inlet chamber 18, followed by another ignition and combustion of fuel.
• combustion pulses having a regular frequency are generated in the combustion chamber.
• the heat generator is run intermittently in dependence of the temperature of the water in the tank 10 in a conventional way; when a predetermined increased temperature of the water is reached, the heat generator is turned off and then restarted, when the temperature is decreased to a predetermined lower temperature.
• the fuel must be ignited externally by means of the spark plug 17 and air must be forced into the inlet chamber by means of the initiation blower 22.
• the ignition device and the initiation blower are turned on at start up, but must be turned off when the heat generator is in normal operation, such a function being defined as a self-ignition of the fuel and the air being injected by a sub-atmospheric pressure in the heat combustion chamber.
• a supervising and controlling device for the heat generator as shown in Fig 1 is shown in Fig 2.
• a sensor 25 is arranged in the wall of the inlet chamber 18.
• the sensor 25 has the purpose of sensing the amplitude of the sound and/or gas pressure in the inlet chamber.
• the sensor 25 is preferably of a piezo electric type, but other types can also be used.
• the sound is supplied to the sensor 25 through a connection 25' in the inlet chamber 18.
• Signals corresponding to the highest and lowest pressures are supplied from the memories 26 and 27 to a differentiator 28, where the lowest value of the signal is subtracted from the highest value, so that a signal corresponding to the signal amplitude is supplied to a further differentiator 29.
• the obtained amplitude signal is compared with a predetermined minimum value for providing an output clearing signal if the amplitude signal, i e the amplitude to the sensor 25, is over the predetermined minimum level .
• a device of this kind can be called an amplitude controller.
• Fig 3 shows a version which is more developed in relation to the amplitude controller according to Fig 2.
• the description above of the device up to and including the emitted signal from the differentiator 29 is the same.
• This emitted signal is in this case supplied to a delay circuit 30, which has the function of only letting through otherwise approved signals with a certain, predetermined duration. In this way singular pressure increases or explosions in the heat generator will not be regarded as an approved operation.
• a so called fire controller which can make use of a photocell as sensor. It can be suitable also for pulse furnaces of the kind described above to utilize such a fire controller, which is approved and cheap due to mass production.
• a unit 31 which emits a signal 32 directly to a photocell input of the fire controller (not shown) .
• the device can be supplemented with a so called phantom feeder, which means that for example a sensor can have its current supply through the same line as it emits its signal .
• a so called phantom feeder which means that for example a sensor can have its current supply through the same line as it emits its signal .
• the current which the fire controller normally emits for reading the otherwise connected photocell be utilized as a driving current for all electronics in the amplitude controller.
• a separate current supply is thus obviated, which leads to a small amplitude controller circuit with a simple connection and a low cost.
• the device also becomes independent of utilized net currency.
• the pressure connection 25' of the sensor 25 can be provided with a snorkel 33, which is arranged in the inlet chamber 18 of the furnace and extends down to its bottom. If liquid due to some defect leaks into the inlet chamber 18 and the liquid enters the snorkel 33, the measured amplitude decreases largely, which thanks to the function of the amplitude controller results in a shut down of the fur- nace , as an approved operation can not be indicated.
• the amplitude controller according to the invention is preferably mechanically constructed for mounting together with the sensor at a suitable measurement position.
• the mounting is simplified and the frequency dependency is obviated that for example a connection hose would give rise to.
• the ignition device comprises a spark plug, but alternatives such as glow means are possible.
• the device for fuel injection can be a carburettor or a spreader instead of an orifice.
• the decoupling chamber can lastly be connected to a bubble chamber or the like instead of an exhaust tube or a chimney.

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• Engineering & Computer Science (AREA)
• Chemical & Material Sciences (AREA)
• Combustion & Propulsion (AREA)
• Mechanical Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Fluidized-Bed Combustion And Resonant Combustion (AREA)
• Regulation And Control Of Combustion (AREA)
• Control Of Combustion (AREA)

Applications Claiming Priority (3)

Publications (1)

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Family Applications (1)

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• 1999
  • 1999-03-18 SE SE9900980A patent/SE514161C2/sv not_active IP Right Cessation
• 2000
  • 2000-03-17 CA CA002366120A patent/CA2366120A1/en not_active Abandoned
  • 2000-03-17 EP EP00919211A patent/EP1161640A1/en not_active Withdrawn
  • 2000-03-17 AU AU39919/00A patent/AU3991900A/en not_active Abandoned
  • 2000-03-17 WO PCT/SE2000/000526 patent/WO2000055542A1/en not_active Application Discontinuation
• 2001
  • 2001-09-17 NO NO20014505A patent/NO20014505L/no not_active Application Discontinuation
  • 2001-09-18 US US09/955,342 patent/US20020037487A1/en not_active Abandoned

Non-Patent Citations (1)

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