WO2023277724A1

WO2023277724A1 - Pulsating combustion apparatus with increased efficiency

Info

Publication number: WO2023277724A1
Application number: PCT/RU2021/000282
Authority: WO
Inventors: Ильгиз Амирович Ямилев
Original assignee: Ильгиз Амирович Ямилев
Priority date: 2021-07-02
Filing date: 2021-07-02
Publication date: 2023-01-05
Also published as: CN117501046A

Abstract

The invention relates to the field of power engineering and can be used in heating systems, more particularly in water heaters or boilers, in recovery systems fuelled by the combustion of associated gas, and in electric power generating systems. A pulsating combustion apparatus comprises a combustion chamber, an air and hot gas feed device connected to the inlet of the combustion chamber, and at least one resonance tube connected to the outlet of the combustion chamber. Connected directly or indirectly to the outlet of the at least one resonance tube is a first Helmholtz resonator containing a chamber and at last one tube, wherein the natural frequency of the first Helmholtz resonator is lower than the combustion pulsation frequency and the Q factor of the first Helmholtz resonator is higher than one. Connected directly or indirectly to the air and hot gas feed device is a second Helmholtz resonator containing a chamber and at last one tube, wherein the natural frequency of the second Helmholtz resonator is lower than the combustion pulsation frequency and the Q factor of the second Helmholtz resonator is higher than one. The invention allows an even greater increase in the efficiency of the apparatus.

Description

Pulsating combustion apparatus with increased efficiency

Technical field

The invention relates to the field of energy and can be used in heating systems, in particular in water heaters or boilers, in recovery systems operating on the combustion of associated gas, in power generation systems.

Prior Art

Pulsed combustion devices are widely known, containing a combustion chamber, an ignition device, fuel supply devices, air supply devices and exhaust channels for removing combustion products. Such devices have high efficiency, but create significant noise and vibration. Attempts are being made to further increase efficiency, in addition, attempts are being made to reduce noise and vibration. The increase in efficiency and the problem of reducing noise and vibration in pulsating combustion devices were solved in different ways.

Known mufflers for compressors with pulsating gas flow and similar devices. US Pat. No. 2,943,641 describes a damper based on Helmholtz resonators, the damping factor depends on the ratio of the noise frequency to the natural frequency of the resonator.

In the pulsating combustion device according to US 4639208, sound-absorbing materials are installed on the path from the combustion chamber to the check valve to reduce the noise level. In the pulsating combustion device according to US Pat. No. 4,259,928, a silencer is used in the air supply channel, coupled with an air check valve, and in addition, this silencer itself is located inside the enclosing cavity, which is located in a vessel with water. A silencer is also installed in the flue gas channel.

The pulsating combustion device according to US 4,477,246 contains an air supply silencer and an exhaust gas silencer, which are combined into a two-cylinder housing, consisting of an outer and an inner cylinder, which are divided into low-frequency and high-frequency noise reduction chambers.

In the pulsating combustion device according to US 4475621, the air damper enclosure is covered with sound-absorbing material, and the flue gas duct contains a gas-to-gas heat exchanger.

In the pulsating combustion device according to US 5,020,987, an improved mechanical gas medium check valve is used to reduce the noise level, which makes it possible to reduce the amplitude of pressure fluctuations in the combustion chamber.

In the pulsating combustion device according to patent US4919085, a silencer is installed in the flue gas outlet channel, consisting of two chambers connected by a pipe. To increase the efficiency of the pulsating combustion device and to reduce the noise level, these cavities are placed in a vessel with a coolant. A muffler is installed in the air supply channel, on one side connected to the fan, on the other side with an air chamber enclosing the air valve and having inner and outer walls, the space between which is filled with sand.

Closest to the proposed apparatus is a device for pulsating combustion, in which Helmholtz resonators with a natural resonant frequency below the frequency of working combustion pulsations are used in the flue gas outlet channel and in the air supply channel to increase efficiency and reduce noise. Additionally, the efficiency is increased by the location of the pipes of the Helmholtz resonators of the smoke channel inside the pipes of the Helmholtz resonators for air supply and / or the location of the pipes of the Helmholtz resonators for air supply inside the pipes of the Helmholtz resonators of the smoke channel (WO 2020117087, pub. 11.06.2020).

The essence of the invention

The technical problem solved by the invention is a further increase in the efficiency of the pulsating combustion device.

List of drawings

On FIG. 1 shows the proposed apparatus with the location of the tube of the Helmholtz resonator of the smoke channel in the tube of the Helmholtz resonator of the air channel. On FIG. 2 shows the proposed apparatus with the arrangement of several tubes of the Helmholtz resonator of the smoke channel in the tube of the Helmholtz resonator of the air channel. On FIG. 3 shows the proposed apparatus with the arrangement of several tubes of the Helmholtz resonator of the air channel in the tube of the Helmholtz resonator of the smoke channel.

On FIG. 4 shows a graph of the efficiency of the apparatus as a function of the area of heat exchange between the flue gas flow and the air flow.

On FIG. 5 shows the proposed apparatus with a hole in the chamber of the Helmholtz resonator, which reduces the quality factor of the Helmholtz resonator.

On FIG. 6 shows a fragment of the proposed apparatus with an element that improves the start of the pulsating combustion apparatus.

Examples of preferred embodiments of the invention

On FIG. 1, the pulsating combustion device comprises a combustion chamber 3 placed in a vessel 1 with a coolant 2 and a resonant pipe 4 connected to the combustion chamber 3. An assembly for separate air and combustible gas supply is connected to the combustion chamber 3, containing an air duct 5 with holes 6 for the passage of combustible gas. With the air and combustible gas supply unit, an air check valve 7 and a combustible gas check valve 8 are connected. The check valve 8 of combustible gas is located in the chamber 9 of the fence. After the resonance tube 4, the first Helmholtz resonator 10 is installed, formed by the smoke chamber 11 and the chimney 12 located after it. The Helmholtz resonator 10 has its own resonant frequency below the combustion pulsation frequency and a quality factor of at least 1. The air and combustible gas supply unit is located in the air chamber 13 , with which an air pipe 14 is connected. The chamber 13 and the pipe 14 form a second Helmholtz resonator 15, which also has its own resonant frequency below the combustion pulsation frequency and a quality factor of at least 1. The chimney 12 is located in the air pipe 14. The chamber 11 is directly connected to the resonant pipe 4. The air chamber 13 is connected to the air and gas supply unit through the air check valve 7.

The efficiency of the pulsating combustion device depends on the temperature of the flue gases released into the atmosphere. The lower this temperature, the higher the efficiency. The temperature of the air entering combustion is lower than the temperature of the coolant, so the presence of heat exchange between the air and flue streams lowers the temperature of the flue gases at the outlet, which increases the efficiency, as indicated in W02020117087. Increasing the area of heat exchange between air and smoke flows leads to an additional increase in efficiency.

To increase the efficiency, it is possible to increase the heat exchange area, for which increase the cross-sectional area and the length of pipes 12 and 14. However, this method has a limitation due to the fact that in this case the flow velocity decreases, which reduces the efficiency of heat exchange between pipes and smoke and air flows . In addition, with an increase in the length of the pipes, standing waves can occur in them, which disrupts the operation of the pulsating combustion device. This method increases the efficiency, but does not allow you to get the maximum possible result from increasing the heat exchange area between the smoke and air flows. On FIG. 2, the first Helmholtz resonator 16, formed by the chamber 17 and the chimneys 18 located after it, has a natural resonant frequency below the combustion pulsation frequency and a quality factor of at least 1, and the second Helmholtz resonator 19, formed by the air chamber 20 and the air pipe 21 connected to it, also has its own resonant frequency below the combustion pulsation frequency and a quality factor of at least 1. Smoke pipes 18 are located inside the air pipe 21. This design allows you to significantly increase the area of heat exchange between smoke and air flows without reducing the flow velocity and without creating conditions for standing waves in pipes 18 and 21. The air and combustible gas supply unit consists of a pre-mixing chamber 22 and a combustible mixture channel 23. The air and gas check valve 24 and the combustible gas check valve 25 are connected to the air and gas supply unit. When pre-mixing air and combustible gas, it is necessary to protect the check valves from overheating and to control the combustion start phase in relation to pressure fluctuations in the combustion chamber 26 . For this, flame arresters 27 as in US 5106292, flame arresters as in JPH 03225101, flame retardant generator as in FR 0856440 can be installed. The chamber 17 is directly connected to the resonant tube 28. The chamber 20 is connected to the air and combustible gas supply unit by means of a check valve 24 for air.

On FIG. 3, the first Helmholtz resonator 29, formed by the smoke chamber 30 and the chimney 31 located after it, has a natural resonant frequency below the combustion pulsation frequency and a quality factor of at least 1. The second Helmholtz resonator 32, formed by the air chamber 33 and connected to it air pipes 34, has a natural resonant frequency below the combustion pulsation frequency and a quality factor of at least 1. The air check valve 35 may have chambers at the inlet and outlet, as in JPH03225101A. A chamber with a pipe (or chambers connected by pipes) form a third Helmholtz resonator 36 (resonators) with a natural resonant frequency above the combustion pulsation frequency, and chambers connected by holes form low-pass filters 37. The air pipes 34 are located inside the chimney 31. This solution allows to obtain an efficiency increase similar to that shown in FIG. 2. The smoke chamber 30 is connected to the resonant pipes 38 by means of a transition element 39, which may be a low-pass filter in the form of a chamber with an outlet, or may be a fourth Helmholtz resonator with a resonant frequency above the combustion pulsation frequency in the form of a chamber and a branch pipe (at Fig. 3 are not shown). The air chamber 33 is connected to the air and gas supply unit by means of resonators 36, an air check valve 35, and low-pass filters 37.

An increase in the heat exchange area leads to an increase in the resistance of the tubes of the Helmholtz resonators. This leads to a decrease in the quality factor of the resonators. Reducing the quality factor of the Helmholtz resonator increases the loss of vibration energy. As stated in W02020117087, the potential energy of the working combustion oscillations is distributed between the combustion chamber and the chamber of the Helmholtz resonator of the smoke channel in inverse proportion to the volumes of the chambers. The energy losses of oscillations in the Helmholtz resonator of the smoke channel are the losses of part of the energy of the working oscillations of combustion. This leads to a decrease in the quality factor of the working combustion resonator. As stated in W02020117087, the working pulsator (combustion resonator formed by the combustion chamber and resonant tubes) has a quality factor margin due to the limitation of the amplitude of pressure fluctuations in the combustion chamber by the combustion start angle, while the quality factor of the working pulsator is greater than 1. If, taking into account losses in the smoke resonator Helmholtz quality factor of the working pulsator becomes lower than the quality factor limited by the angle of the start of combustion, then the heat exchange between the working pulsator and the coolant decreases, which leads to a decrease in the efficiency of the working pulsator. The optimal heat exchange area is such an area at which the sum of the efficiency of the working pulsator and the added efficiency of heat exchange between the pipes of the smoke and air channels has a maximum value.

On FIG. 4 shows a plot of efficiency versus heat exchange area between the smoke stream and the air stream. Line 40 shows the efficiency of the working pulsator without limiting the quality factor by the angle of the start of combustion. Line 41 shows the efficiency of the working pulsator when the quality factor is limited by the angle of the start of combustion. Line 42 shows the increase in efficiency by heat exchange between the smoke stream and the air stream. Line 43 shows the total value of the efficiency of the working pulsator and the addition of efficiency by heat exchange between the smoke stream and the air stream. The optimal heat exchange area between the smoke stream and the air stream is shown by pointer 44.

With an increase in the area of heat exchange between the smoke flow and the air flow, the resistance of the tubes of the Helmholtz resonator of the air channel increases. The resistance of the tubes of the Helmholtz resonators of the air channel determines the required average air pressure difference between the atmosphere and the combustion chamber, which is necessary for the operating flow of combustion air. With high resistance, the necessary air flow for combustion is not provided. Air enters the combustion chamber in flow pulsations. Therefore, the Helmholtz resonators of the air channel must have losses of oscillation energy not higher than a certain value, respectively, the Helmholtz resonators of the air channel must have a quality factor not lower than a certain value.

The quality factor of the Helmholtz resonator reflects the ratio of vibration energy to the loss of vibration energy. The energy loss of the Helmholtz resonator oscillations consists of the loss of kinetic energy on the active resistance of the resonant tubes and the loss of potential energy of pressure in the chamber. Potential pressure energy occurs when there are holes or slots in the chamber. For example, the chambers of the flue gas Helmholtz resonators may have openings for connection to a condensate drain. On FIG. 5 in the smoke chamber 45 there is a hole 46 for connecting the pipe 47 of the condensate drain system, which reduces the quality factor of the Helmholtz resonator 48 formed by the smoke chamber 45 and the chimney 49. A large drop in the quality factor of the Helmholtz resonator 48 with hole 46 can lead to a drop in the efficiency of the working pulsator without the use of heat exchange between the smoke stream and the air stream. The smoke chamber 45 of the Helmholtz resonator 48 formed by the smoke chamber 45 and the chimney 49 is directly connected to the resonant tube 50. The air chamber 51 of the Helmholtz resonator 52 formed by the air chamber 51 and the air tube 53 is connected to the air and gas supply unit by means of a return air valve 54. The partition 55 is the wall of the chamber 51 and at the same time the wall of the chamber 45.

High efficiency is achieved by the high quality factor of the working pulsator. With a high quality factor of the pulsator, few turbulent vortices are created during blowing, combustible gas and air are poorly mixed, so it is difficult to get a combustible mixture on the spark plug at the right time. Starting the pulsating combustion apparatus is difficult. To improve startup stability, the solution shown in FIG. 6. Air from the Helmholtz air resonator chamber 57 enters the combustion chamber 56 through the check valve 58 of the air and the air duct 59. The combustible gas enters the combustion chamber 56 through the check valve 60 of the gas and slots 61. Part 62 of the air flow is mixed with the combustible gas and discarded by the guides elements 63 to the spark plugs 64. The guide element 63 consists of two walls, one of which is located with a gap relative to the duct, and the other is installed with a gap relative to the combustion chamber 56. Said walls are connected to the air duct 59 and the combustion chamber 56 by a rib located radially relative to the air duct 59.

To calculate the quality factor of the working pulsator, Helholtz resonators and the parameters required for this, the equations below are used.

The quality factor of the working pulsator (resonator), taking into account the quality factor of the Helmholtz smoke resonator, is equal to:

one

Q 1 D 1

2, V _{1 +} V ₂ Q 2 (1) where Q is the quality factor of the working pulsator, taking into account losses in the smoke resonator,

6 - quality factor of the working pulsator without a smoke resonator,

62 - quality factor of the Helmholtz smoke resonator,

r r , ,

- the volume of the smoke resonator chamber, "* ³ .

In WO 2020117087 it was stated that the quality factor of the resonator

Helmholtz is equal to:

where b* is the quality factor of the Helmholtz resonator,

^X L- resistance of the total acoustic inductance L of one or more pipes to oscillations with a resonant frequency

, Pa-sec! m ³ ,

^ - total active resistance of one or more pipes, Pa-sec / m ³

The chamber of the Helmholtz resonator may have holes or slots, for example, to drain condensate. Then, in addition to losses of vibrational energy on the resistance of pipes, there will also be losses of pressure energy to the chamber. The quality factor of such a Helmholtz resonator is equal to:

where ^R is the quality factor of the Helmholtz resonator,

^Xl - resistance of the total acoustic inductance L of one or more pipes to oscillations with a resonant frequency

, Pa - sec / m ³ _? - resistance of the acoustic capacitance of the chamber to vibrations with a resonant frequency ^ , Pa - sec / m ^b _?

^R ' - total active resistance of one or more pipes, Pa -sec / m ³

^2 - total active resistance of holes and / or slots of the chamber, Pa ^-sec / m

WO 2020117087 also stated that the resistance of a Helmholtz resonator chamber with acoustic capacitance to vibrations with frequency / is equal to:

where “ ^c _ is the resistance of the acoustic capacitance with oscillations with a frequency / Pa -sec / m ³

/ . oscillation frequency, Hz,

C - acoustic capacity, m / Pa

WO 2020117087 also stated that the resistance of Helmholtz resonator tubes with a total acoustic inductance L to oscillations with frequency / is equal to:

X _b \u003d 2

(five)

Xh resistance of acoustic inductance L to vibrations with frequency / Pa -sec / m ³ f - oscillation frequency, Hz,

L - acoustic inductance,

WO 2020117087 also stated that the camera has acoustic capacitance properties equal to:

where C is the acoustic capacitance, m ^b / Pa _^ Y is the adiabatic coefficient,

^P ° - average pressure in the chamber, Pa

V is the volume of the chamber, ^m . WO 2020117087 also stated that the pipe has an acoustic inductance property equal to:

_L-El L

^A (?) where L is acoustic inductance,

,

P is the density of the gas in the pipe,

, ^ - pipe length, ^m ,

A is the cross-sectional area of the pipe, for several pipes the sum

2 cross-sectional areas of pipes, ^m .

The total inductance of several parallel pipes of the same inductance: where L - total acoustic inductance, Pa -sec 1m

- acoustic inductance of one pipe, Pa -sec ² / m ^g p - number of parallel pipes of the same inductance.

The total inductance of several parallel pipes of different inductance is calculated taking into account the total inductance of two parallel pipes:

where L _ total acoustic inductance, ^Pa ^s ² 1 ^m ,

^L , ^L 2 - acoustic inductance of parallel pipes, Pa-sec ² / m ^ъ _?

In WO 2020117087 it was also stated that the active resistance of the pipe is equal to:

1 q l \u003d XP

2 A (10) where R is the active resistance of the pipe, Pa - sec / m ³ ₅ ^ - gas flow, ^ I ^sec ,

X _ the sum of the aerodynamic resistance coefficients of the pipe: inlet, outlet, along the length and local, for example, turns,

.3

P - gas density, ^kg ! m _?

A - m .2 pipe cross-sectional area,

The active resistance of a hole or slot is equal to:

where R is the active resistance of the hole or slot, Pa-sec 1m ³

^ - gas consumption,

, - aerodynamic drag coefficient of the hole or slot, equal to 0.5. Р - gas density, kg _/ ^m

A is the cross-sectional area of the pipe, ^m2 .

The total active resistance of several identical parallel resistances:

where R is the total active resistance, Pa-sec / m ³

D

1 - active resistance of each parallel active resistance, Pa · sec / m _? n is the number of parallel tubes of the same inductance. The total active resistance of several different parallel resistances is calculated taking into account the total active resistance of two parallel different resistances:

where R is the total active resistance, Pa-sec/m parallel active resistances, Pa-sec/m

Thus, the proposed invention provides an increase in the efficiency of the pulsating combustion apparatus by using a balance between the quality factor, active resistance, and pressure loss.

Claims

Claim

1. Apparatus for pulsating combustion, comprising a combustion chamber, a device for supplying air and combustible gas connected to the inlet of the combustion chamber and connected to the outlet of the combustion chamber, at least one resonant tube, while the first one is directly or indirectly connected to the outlet of at least one resonant tube a Helmholtz resonator containing a chamber and at least one tube, the natural frequency of the first Helmholtz resonator is below the combustion pulsation frequency and the quality factor of the first Helmholtz resonator is higher than unity, a second Helmholtz resonator is directly or indirectly connected to the device for supplying air and combustible gas, containing a chamber and at least one pipe, the natural frequency of the second Helmholtz resonator is lower than the combustion pulsation frequency and the quality factor of the second Helmholtz resonator is higher than unity.

2. Apparatus according to claim 1, wherein at least one tube of the second Helmholtz resonator is located inside the tube of the first Helmholtz resonator.

3. Apparatus according to claim 1, wherein at least one tube of the first Helmholtz resonator is located inside the tube of the second Helmholtz resonator.

4. Apparatus according to claim 1, wherein the second Helmholtz resonator is connected to the air and combustible gas supply by means of a low pass filter.

5. Apparatus according to claim 1, in which the second Helmholtz resonator is connected to the device for supplying air and combustible gas through a third Helmholtz resonator with a resonant frequency higher than the combustion pulsation frequency

6. The apparatus of claim 1, wherein the first Helmholtz resonator is connected to the output of at least one resonant tube via a low pass filter.

7. Apparatus according to claim 1, wherein the first Helmholtz resonator is connected to the output of at least one resonant tube via a fourth Helmholtz resonator with a resonant frequency above the combustion pulsation frequency.