DE2256906A1 - PULSING COMBUSTION DEVICE - Google Patents

Description

Pulsating combustion device

The invention relates to a pulsating combustion device with two symmetrical combustion chambers open at one end and each closed at one end End an inlet for a fuel-oxidizing agent mixture and at the open end an outlet for combustion gases, as well as an ignition device.

The use of pulsating or according to the principle of Rocking fire incinerators offer many advantages, especially in cases where heat is transferred shall be.

Since the combustion process is almost like constant-space combustion the combustion intensity is high. Therefore, for a given heat output or heating power, the Dimensions of the combustion chamber relatively small.

Since the combustion gases are generated intermittently, the heat transfer resistance at the boundary layer is reduced.

309822/0860

- 2 - 42 205

Therefore, the heat exchange surfaces can be made correspondingly smaller for a given capacity of the system. If required, high heating outputs can be achieved.

The exhaust gases can be easily discharged due to the pressure generated in the combustion chamber. Because of this, you can Flue ducts or chimneys with a small clear width can be used. Such a drainage line can be in the form of a several meters long pipe that is passed through an outside wall of a building.

So far, pulsating combustion devices are neither in industrial buildings nor in larger residential buildings Extent has been used. The reasons for this are that they cause excessive noise and that the Costs for appropriate noise abatement measures are high. The lamb reduction according to the interference method mainly influences the fundamental frequency, somewhat the harmonic frequency of the combustion device. It is therefore necessary, in order to achieve maximum effect, to ensure that the majority of the produced Noise has the fundamental frequency. This is can only be achieved through careful adjustment under actual operating conditions. Any subsequent deviation from the Voting conditions, for example a change in the Feed pressure or the throughput leads to a change in the sound spectrum emitted by the combustion device and thus to a decrease in the effectiveness of noise reduction devices used.

It is a special form of training for those who work in a pulsating manner Combustion devices with duo (twin) arrangement of the alternately working combustion chambers are known.

309822/0860 / ₃

- 3 - 42 205

225690e

Such an agreement, with the / resulting results are achieved is described in the applicant's patent application P 20 06986. It has at least two combustion chambers each with an inlet for a fuel-oxidizer mixture, an outlet for Combustion gases, an ignition device and with a signal or. Pulse pick-up device is provided. Every impulse Receiving device is attached to a control channel of a flow-controlled logical switching element in the form of a multi-way valve designed as a fluidic element, the outlets of which are each connected to the inlet of a combustion chamber.

In this known embodiment of a pulsating combustion device, there are no mechanical shut-off devices or valves are required. Their operating frequency range is not only dependent on their natural resonance frequency. In addition, it has a large control range and only requires a small blower for gas discharge »

The invention is based on the object of developing the above-described pulsating combustion device and to be improved in such a way that the use of flow-controlled logic switching elements is dispensed with can be.

With a combustion unit, this task is the same as at the beginning described type solved, which is characterized according to the invention in that the acoustic properties of each combustion chamber are at least substantially equivalent to those of a quarter-wave tube, and that the open Ends of the combustion chambers are opposite one another and leave a lateral exit slot which is of the order of magnitude of the cross-sectional area of the combustion chambers lies.

/ 4 3Q9822 / 08 SO

42 205

The combustion chambers are preferably cylindrical tubular bodies.

When designing the combustion chambers, it should be taken into account that pressure waves are generated in each combustion chamber in such a way that an alternating pulse sequence comes about.

The internal shape of the incinerator must be chosen in this way be that the pressure waves generated in each combustion chamber run regularly and symmetrically with the smoothest possible profile. The lack of fine structures in the generated pressure waveform ensures that the phase shifted when superimposed Pressure waves produce a minimum of noise or noise.

The ignition device can consist of one arranged in the associated combustion chamber and one electrical high-voltage source connected stabilization and ignition device exist.

The lateral outlet is preferably as - apart from arranged symmetrically distributed along its circumference, for Alignment and / or reinforcement of the mechanical strength of the device serving fasteners - continuous Formed slot.

The outlets of the two combustion devices must be opposite one another on either side of an intermediate space in such a way that that the cross-sectional area of the annular slot thus obtained is not larger than the cross-sectional area a combustion tube. The combined outlets should then be enclosed in a container, which has a single outlet. The cross-sectional area of this outlet is no larger than the cross-sectional area of a combustion tube "In this way, that the exit pulses are perpendicular

30y822 / 0860

- 5 - 42 205

meet and not in the prior to their combination Atmosphere.

Each combustion chamber can be surrounded by a jacket or a container through which a Let Flud pass through. The combustion chambers can also have a common fluid jacket or air reservoir. The outlets of the combustion chambers can be provided with devices to reduce noise.

The system used to supply fuel and air is to ensure that the pressure fluctuations generated do not adversely affect the supply. For this purpose there is the inlet for the fuel-oxidizing agent mixture at each combustion chamber according to the invention an inlet nozzle whose pressure drop is selected so that during operation there is no return flow of combustion gas residues into the supply line.

Runs in a pulsed combustion device a steady sequence of explosions or deflagrations, where heat is released periodically. The vibration frequency is controlled acoustically or otherwise.

For a combustion chamber in a pulsating one Combustion device according to the invention results following workflow:

(1) When starting up, supply of fuel and air to the common room,

(2) the air-gas mixture is ignited by an ignition spark. The resulting combustion takes place in the combustion chamber an overpressure is generated which expels the combustion gases through the open end of the combustion chamber.

(3) During the expansion and discharge of the combustion gases, a negative pressure is created in the combustion device

309 822/0860

/ 6

- 6 - 42 205

generated, which is used to supply a further air-gas filling is drawn into the incinerator.

The work steps (2) and (3) are then repeated.

As soon as the pulsating combustion got under way in the system each new filling is ignited by residual cores or residual particles from the previous combustion. the Ignition device is no longer needed, the process is self-sustaining.

With steady operating conditions in coupled with each other Combustion devices run these processes in such a way that the pressure waves at the open ends of the combustion chambers are out of phase.

A standing quarter wave is created in the resonance tube, a pressure node at the outlet and in the area of the combustion zone has a feck belly. The period frequency depends mainly on the length of the resonance tube.

The invention is explained below with the aid of schematic drawings of several exemplary embodiments with further details explained. In the drawing shows:

1 shows a combustion device with combustion chambers arranged parallel to one another, the outlet ends of which are bent so that they face each other, and

2 shows a combustion device with rectilinearly aligned combustion chambers.

The drawing shows combustion chambers 1 and 2, the closed one Have inlet ends 3 and 4 and open outlet ends 5 and 6, respectively. Each combustion chamber has close to its closed End of an ignition device 7 or 8.

309822/0860 / 7

- 7 - 42 205

At the closed ends of the combustion chambers there are inlet nozzles 9 and 10 for the fuel-oxidant mixture arranged »which are connected to supply lines 11 and 12, respectively. To prevent combustion gases from flowing back into the supply lines Suitable devices, for example in the form of aerodynamically designed shut-off devices, are to be prevented or valves 13 and 14 are provided. In Pig. 1, the nozzles are arranged axially, while in the arrangement shown in Fig. 2, the supply of the fuel-oxidizing agent mixture takes place tangentially.

At the opposite open ends of the combustion chambers, there is a lateral outlet slot 15 which extends from an outlet chamber 16 is enclosed. This can serve both as a device for noise reduction as well as to the To slow down pressure build-up and to promote the interaction between the two combustion chambers.

The distance between the outlet ends of the combustion chambers is chosen so that the sound pressure waves are mutually exclusive influence and that the extraction of the combustion gases comes about in a suitable manner, without the transfer of the To disturb pressure wave significantly.

The combustion chambers are surrounded by a heating jacket 17 in the form of a container to which a liquid, for example Water, via an inlet 18 and heated liquid can be supplied or removed via an outlet 19. The outlet 19 can, for example, to a central heating system be connected.

EXAMPLE·

With a pulsating combustion device In the embodiment shown in Fig. 1, the combustion chambers had one in an axial view and between the Nozzle and the face at the outlet measured length of 1275 mi

309322 / 086Q. . /8th

- 8 - 42 205

and a diameter of 37 »5 mm. These dimensions correspond to the equivalent of a quarter-wave tube. The width of the annular slot was 5 mm. As fuel methane mixed with air was used. The fuel-air volume ratio was between 0.09 and 0.14. Satisfactory results were achieved under all test operating conditions. As a control range the ratio was about 2: 1.

Compared to two individual, independently operated incinerators, a noise reduction in of the order of 35 dB.

/ Claims 309822/0860

Claims (4)

EXPECTATIONS \1. ι Pulsating combustion device with two symmetrical combustion chambers open at one end, each with an inlet for a fuel-oxidant mixture at the closed end and at the open end an outlet for combustion gases and an ignition device have, characterized in that the acoustic properties of each combustion chamber (1,2) at least substantially equivalent to those of a quarter-wave tube are, and that the open ends (5,6) of the combustion chambers (1,2) are opposite one another and one lateral Outlet opening (15) in the order of magnitude of the cross-sectional area leave the combustion chambers (1,2). 2. Combustion device according to claim 1, characterized in that the combustion chambers (1,2) are cylindrical tubular bodies. 3. Combustion device according to claim 1 or 2, characterized in that the lateral outlet opening (15) apart from being symmetrical along its circumference distributed, serving to align and / or strengthen the mechanical strength of the device Connecting means is a continuous slot. 4. Combustion device according to one of claims 1 to 3 »characterized in that the inlet (3 or 4) for the Fuel-oxidizing agent mixture, an inlet nozzle 309822/0860 42 205 (9 or 10), the pressure drop of which is chosen so that its operating behavior is equivalent to that of an aerodynamic shut-off device and a backflow of combustion gases in the supply line (11, 12) prevents. 309822/0860