KR20220122346A - Method for stabilizing combustion of hydrogen-methan mixed fuel - Google Patents

Abstract

The present invention relates to a method of stabilizing combustion of a hydrogen-methane mixed fuel and, more specifically, to a method of stabilizing combustion of a hydrogen-methane mixed fuel, wherein sensitivity to external disturbance decreases as the hydrogenation rate of the hydrogen-methane mixed fuel increases in over-concentrated premixed gas, thereby stabilizing combustion, and sensitivity to external disturbance decreases as the hydrogenation rate of the hydrogen-methane mixed fuel increases in thin premixed gas, thereby stabilizing combustion. The present invention relates to a method of stabilizing combustion of a hydrogen-methane mixed fuel in a gas turbine or a combustor, comprising the steps of: (a) producing a mixed fuel composed of hydrogen-methane; (b) creating an equivalent ratio of the mixed fuel and air; and (c) supplying oxygen to control the speed of flame propagation during combustion of the mixed fuel. Provided is a method of stabilizing combustion of a hydrogen-methane mixed fuel, wherein the over-concentrated premixed gas composition is maintained with the equivalent ratio of the mixed fuel and air in step (b) being equal to or greater than 1.1 and equal to or smaller than 1.4, and sensitivity to external disturbance is reduced by increasing the hydrogenation rate of the mixed fuel. The equivalent ratio is Φ = (F/A)_actual/(F/A)_theoretic = injected air amount/theoretic air amount, and the equivalent ratio of the over-concentrated premixed gas is equal to or greater than 1.1.

Description

Method for stabilizing combustion of hydrogen-methane mixed fuel {METHOD FOR STABILIZING COMBUSTION OF HYDROGEN-METHAN MIXED FUEL}

The present invention relates to a method of stabilizing combustion of a hydrogen-methane mixed fuel, and more particularly, as the hydrogenation rate of a hydrogen-methane mixed fuel in an over-concentrated premixed gas increases, the sensitivity to external disturbances decreases to stabilize combustion, The present invention relates to a combustion stabilization method of a hydrogen-methane mixed fuel in which the sensitivity to external disturbance decreases as the hydrogenation rate of the hydrogen-methane mixed fuel increases in a lean premixed gas, thereby stabilizing the combustion.

Hydrogen is a very unstable element, and due to its high diffusion power and high combustion reaction rate, it is highly likely to cause thermoacoustic instability in commercial combustors when used as a fuel. Here, thermoacoustic instability mainly occurs inside the gas turbine and in the high-temperature and high-pressure combustion chamber, and pressure and heat fluctuations occur. If the phase difference between pressure and heat is different, a larger energy form is formed, which can cause fire or explosion accidents due to accumulation of thermal stress and excessive vibration.

On the other hand, Patent Registration No. 10-1544388 proposes a method for improving the idle operation and catalyst efficiency of a natural gas and hydrogen mixed fuel engine. However, the mixed fuel is limited to securing stability for idle operation, and there is a problem in that it is impossible to use a fuel mixed with hydrogen and methane in a commercial combustor including an actual marine engine, gas turbine, or rocket propellant. It is a time when development research is required.

Korean Patent No. 10-1544338

The present invention was invented to solve the above problems, and the higher the hydrogen addition rate under the condition of an equivalence ratio of 1.1 or more and 1.4 or less, the higher the hydrogen addition rate, the more combustion stability is secured, preventing large-scale explosion accidents, and having a high calorific value during combustion, the equivalence ratio It is a technical solution to provide a method for stabilizing the combustion of a hydrogen-methane mixed fuel in which combustion stability can be secured as the hydrogen addition rate is lowered in the lean premixed gas condition of 0.6 or more and 0.9 or less.

In order to solve the above technical problem, the present invention provides the steps of (a) preparing a mixed fuel composed of hydrogen-methane, (b) creating an equivalent ratio of the mixed fuel and air, and (c) for the mixed fuel In the combustion stabilization method of a hydrogen-methane mixed fuel for a gas turbine or combustor comprising; The equivalence ratio maintains the over-concentrated premixed gas composition of 1.1 or more and 1.4 or less, and increases the hydrogen addition rate to the mixed fuel, thereby reducing the sensitivity to external disturbance. to provide.

이고, 과농 예혼합 가스는 당량비가 1.1이상을 의미한다.)(the equivalence ratio

, and the excessively concentrated pre-mixed gas means that the equivalence ratio is 1.1 or more.)

In the present invention, according to the hydrogenation rate and flame propagation rate for the mixed fuel, the flame propagation rate is 35 to 38 cm/s at 90 to 99.9 vol% of methane and 0.1 to 10 vol% of hydrogen, and 70 to 90 vol% of methane and hydrogen It is a hydrogen-methane mixed fuel with a flame propagation speed of 35-42 cm/s at 10-30 vol% and combustion stabilization in the range of 35-46 cm/s at a flame propagation speed of 35-46 cm/s at 50-70 vol% of methane and 30-50 vol% of hydrogen. It features a combustion stabilization method.

In addition, the present invention provides the steps of (a) preparing a mixed fuel composed of hydrogen-methane, (b) creating an equivalent ratio of the mixed fuel and air, and (c) burning the mixed fuel, flame propagation speed In a combustion stabilization method of a hydrogen-methane mixed fuel for a gas turbine or combustor, comprising the step of supplying oxygen to control In the case of a lean pre-mixed gas composition of

이고, 희박 예혼합 가스는 당량비가 0.9이하을 의미한다.)(The equivalent ratio is

, and the lean pre-mixed gas means that the equivalence ratio is 0.9 or less.)

According to the method for stabilizing combustion of a hydrogen-methane mixed fuel by means of solving the above problems, when hydrogen-methane is mixed and used as a fuel, the stability of combustion is ensured, thereby preventing a large-scale explosion accident.

In addition, there is an effect of having a calorific value suitable for use as fuel in a commercial combustor including a marine engine, a gas turbine, or a rocket propellant when the hydrogen-methane mixed fuel is combusted.

1 is a flowchart illustrating a method for stabilizing combustion of a hydrogen-methane mixed fuel according to the present invention.
2 is a graph showing the stabilization of a hydrogen-methane mixed fuel in a lean pre-mixed gas condition according to the present invention.
3 is a graph showing the stabilization of a hydrogen-methane mixed fuel in an over-concentrated pre-mixed gas condition according to the present invention.
4 is an experimental schematic diagram showing the combustion stability of a hydrogen-methane mixed fuel according to the present invention.
5 is a photograph showing the degree of flame for each area according to FIG. 3 .
6 is a photograph and graph showing characteristics of each area according to FIG. 3 .

Hereinafter, an embodiment of the present invention will be described in detail with reference to the accompanying FIGS. 1 to 6 . On the other hand, in the drawings and detailed description, drawings and descriptions of configurations and actions that can be easily understood by those skilled in this field are simplified or omitted. In particular, in the drawings and detailed descriptions, detailed descriptions and illustrations of specific technical configurations and actions of elements not directly related to the technical features of the present invention are omitted, and only the technical configurations related to the present invention are briefly illustrated or described. did.

Prior to explaining the present invention, the world's dependence on petroleum energy is gradually shifting to a gas energy source, and as a measure to prevent global warming, the proportion of hydrogen, a clean energy source, is greatly expanded. However, because of its high diffusive power and high combustion reaction rate, hydrogen is likely to develop thermoacoustic instability in commercial combustors including gas turbines and rocket propellants. Thermoacoustic instability is a perturbation of pressure and heat itself, and when the phase difference is in phase, a larger energy is formed and there is a risk of explosion during combustion. Accordingly, it is necessary to stably create a ratio of hydrogen-methane mixed fuel for the instability of combustion.

1 is a flowchart illustrating a method for stabilizing combustion of a hydrogen-methane mixed fuel according to the present invention.

The present invention supplies oxygen to control the flame propagation speed during the steps of preparing a mixed fuel composed of hydrogen-methane (S1), creating an equivalent ratio of the mixed fuel and air (S2), and burning the mixed fuel It is made to include a step (S3), and is applied to a gas turbine or combustor.

By the step (S2) of composing the equivalence ratio of the mixed fuel and air, the equivalence ratio of 1.1 or more and 1.4 or less is maintained and the hydrogenation rate to the mixed fuel is increased while maintaining the composition of the over-concentrated premixed gas to reduce the sensitivity to external disturbance. can

Alternatively, by the step (S2) of composing the equivalence ratio of the mixed fuel and air, the equivalence ratio of 0.6 or more and 0.9 or less of the lean pre-mixed gas composition is maintained and the hydrogen addition rate to the mixed fuel is reduced to reduce the sensitivity to external disturbance. can do it

Here, the equivalence ratio means the ratio of fuel and air, and can be calculated by the following <Equation 1>. The over-concentrated premix gas has an equivalence ratio of 1.1 or more, and the range of the equivalence ratio in which combustion is stabilized in the present invention in a fuel-rich state with more fuel than air may be selected as 1.1 or more and 1.4 or less.

In addition, the lean premix gas has an equivalence ratio of 0.9 or less and a fuel lean state with more air than fuel, and in the present invention, the range of the equivalence ratio to be stabilized by combustion may be selected to be 0.6 or more and 0.9 or less.

<Equation 1>

은 이론적인 연료와 공기의 질량의 비로 본 발명에서 이론공기량이라 칭하고, 분자의

는 실제 현장에서 투입된 연료와 공기의 질량비로 본 발명에서 주입공기량으로 칭한다. 예를 들어 F:A 질량비가 1.2:16으로 투입되는 경우

으로 당량비가 1.2로 도출되어 연료 과농 상태라고 할 수 있다.)(By Equation 1 above, Φ is the equivalence ratio, F is the mass ratio of fuel, and A is the mass ratio of air.

is the ratio of the theoretical mass of fuel and air, called the theoretical amount of air in the present invention, and the

is the mass ratio of fuel and air input at the actual site, and is referred to as the amount of injected air in the present invention. For example, if the F:A mass ratio is 1.2:16

Therefore, the equivalence ratio is derived as 1.2, which can be said to be fuel-rich.)

And in the heavily enriched premixed gas, the flame propagation rate is 35-38 cm/s at 90~99.9% by volume of methane and 0.1~10% by volume of hydrogen, depending on the hydrogenation rate and flame propagation rate for the mixed fuel, and 70~90% by volume of methane and hydrogen The flame propagation rate is 35-42 cm/s at 10-30 vol%, and combustion stabilization is achieved as the hydrogenation rate is increased in the range of 35-46 cm/s at the flame propagation rate of 50-70 vol% methane and 30-50 vol% hydrogen. This corresponds to region III' of FIG. 3 .

An experiment to evaluate the stability thereof is shown in FIG. 4 . The conditions of the experiment to evaluate the combustion stability of hydrogen-methane mixed fuel are as follows.

Since gas turbines or commercial combustors generally adopt an open system system, they belong to a resonator that can generate an acoustic field. When abnormal heat emission occurs due to combustion instability in the resonator, it may develop into thermoacoustic instability in which both thermal energy and acoustic waves are amplified due to interaction with the existing acoustic field. When thermoacoustic instability occurs, there is a problem with vibration and noise inside the combustor system, and if it continues, a combustor explosion may occur.

In addition, the quarter-wave resonator adopted as a combustor has an open upper part of the tube and a closed lower part. According to the pressure distribution, the upper part of the pipe corresponds to a node and the lower part of the pipe corresponds to the antinodes, and the velocity distribution is opposite to the pressure distribution. The tube can be made of transparent acrylic, and the experiment can be carried out with an inner diameter of 3 cm and a length of 100 cm. In addition, a fully automatic opening/closing system composed of a pneumatic cylinder and a solenoid valve may be installed in the upper part of the burner. When the switching system is closed, the premixed gas is charged to atmospheric pressure, and then the switching system is opened at the same time as ignition starts in the spark igniter. The flame generated after ignition propagates to the bottom of the tube, and the propagation behavior of the flame was photographed with a high-speed camera. A microphone was installed at the bottom of the burner to measure acoustic waves. All sequential control of the system is done through the program controller. In order to visualize the flow field of the flame front, it can be observed by adopting a non-scattering technique using a diode laser of 532 nm.

The composition ratio of the hydrogen-methane mixed fuel used in the experiment can be adjusted to 50 to 99.9 vol% of methane and 0.1 to 50 vol% of hydrogen. When the hydrogen content is 50% by volume or more, the composition ratio can be limited in this way because hydrogen, not methane, becomes the standard for the mixed fuel.

In addition. In the experiment, the equivalence ratio of the rich pre-mixed gas is 1.2, and the equivalence ratio of the lean pre-mixed gas is set to 0.8. Basically, the gas composition used in the gas turbine adopts a gas composition with an equivalence ratio close to 1, and when the equivalence ratio is far from 1, the heat release rate is low and the operation efficiency is poor, so an equivalence ratio close to 1 can be adopted. .

In addition, the flame propagation speed can be changed by adjusting the amount of oxygen according to the nitrogen dilution rate <Equation 2> at a fixed equivalence ratio in the experiment.

<Equation 2>

(By Equation 2 above, D is the nitrogen dilution rate.)

The results of the experiment according to the above conditions are as follows, and are shown in FIGS. 5 to 6 . 5 is a photograph showing the flame degree for each region when hydrogen-methane mixed fuel is burned under the excessively concentrated premixed gas condition of the present invention, and FIG. did.

First, as shown in FIGS. 5 to 6, region I is a stable flame, region II is primary thermoacoustic instability, region Ⅲ is secondary thermoacoustic instability, region Ⅲ′ is restabilization of secondary thermoacoustic instability, region IV is It can be defined as an explosive turbulent flame.

As shown in FIG. 6 , in the case of an excessively concentrated pre-mixed gas, region I is a relatively stabilized flame with no acoustic sound with hydrodynamic instability, and region II is accompanied by a vibrating flat flame and small noise. Combustion instability is defined as primary thermoacoustic instability. Region III is defined as secondary thermoacoustic instability as a flame that starts to appear wavy in a vibrating flat flame and transitions to turbulence after causing a loud noise. Region Ⅲ' is a region that is stabilized as the flame propagation speed increases, and is defined as the re-stabilization of secondary thermoacoustic instability. Lastly, after ignition in region IV, a wavy flame accompanied by a large noise goes through a short oscillation cycle and then immediately transitions to turbulence, which is the region where the strongest combustion instability is observed in the entire region.

Therefore, referring to FIG. 2 , when using as a hydrogen-methane mixed fuel, when a lean pre-mixed gas is prepared, the sensitivity to external disturbance increases as the hydrogen addition rate increases, leading to extreme combustion instability along with explosive pressure amplification. do. Accordingly, when 50% by volume of methane and 50% by volume of hydrogen are mixed, an explosive turbulent flame is observed despite the low flame propagation speed.

In addition, referring to FIG. 3 , when using as a hydrogen-methane mixed fuel, when an over-enriched pre-mixed gas is prepared, as the addition rate of hydrogen increases, the reaction sensitivity to external disturbance decreases, thereby realizing a stable combustion environment. have. Therefore, when 50% by volume of methane and 50% by volume of hydrogen are mixed, restabilization of secondary thermoacoustic instability corresponding to region Ⅲ′ in the above experiment is observed despite a relatively high flame propagation speed of 40 cm/s. .

That is, according to the hydrogen-methane mixed fuel gas composition of the present invention, when a hydrogen-methane mixed fuel is used in a gas turbine or a combustor where thermoacoustic instability may occur, an over-rich premixed gas composition of 1.1 or more and 1.4 or less is adopted to increase the hydrogenation rate. Increasing it can ensure combustion stability as well as improving gas turbine operation efficiency, and when a lean premixed gas composition of 0.6 or more and 0.9 or less is adopted, lowering the hydrogen addition rate can improve operation efficiency.

Although the combustion stabilization method of the hydrogen-methane mixed fuel according to the embodiment of the present invention as described above has been illustrated according to the above description and drawings, this is merely an example and various other methods are provided without departing from the technical spirit of the present invention. It will be appreciated by those skilled in the art that changes and modifications are possible.

Claims (3)

(a) preparing a mixed fuel consisting of hydrogen-methane; and
(b) creating an equivalent ratio of the mixed fuel and air; and
(c) supplying oxygen to control the flame propagation speed during combustion of the mixed fuel; in a method for stabilizing combustion of a hydrogen-methane mixed fuel for a gas turbine or combustor comprising:
Step (b) is
Hydrogen-methane mixed fuel, characterized in that the equivalence ratio of the mixed fuel and air is maintained in an over-concentrated premixed gas composition of 1.1 or more and 1.4 or less, and the hydrogen addition rate to the mixed fuel is increased to reduce the sensitivity to external disturbances. combustion stabilization method
(The equivalent ratio is

, and the excessively concentrated pre-mixed gas means that the equivalence ratio is 1.1 or more.) 2. The method of claim 1
According to the hydrogenation rate for the mixed fuel and the flame propagation rate
A flame propagation rate of 35-38 cm/s in 90 to 99.9 vol% of methane and 0.1 to 10 vol% of hydrogen,
Flame propagation speed of 35-42 cm/s in 70-90 vol% of methane and 10-30 vol% of hydrogen,
Combustion stabilization method of hydrogen-methane mixed fuel, characterized in that the combustion is stabilized in the flame propagation speed of 35-46 cm/s in 50-70 vol% of methane and 30-50 vol% of hydrogen (a) preparing a mixed fuel consisting of hydrogen-methane; and
(b) creating an equivalent ratio of the mixed fuel and air; and
(c) supplying oxygen to control the flame propagation speed during combustion of the mixed fuel; in a method for stabilizing combustion of a hydrogen-methane mixed fuel for a gas turbine or combustor comprising:
Step (b) is
When the equivalence ratio of the mixed fuel and air is 0.6 or more and 0.9 or less, in the state of the lean pre-mixed gas composition,
Combustion stabilization method of hydrogen-methane mixed fuel, characterized in that the hydrogen addition rate to the mixed fuel is decreased to reduce the sensitivity to external disturbance
(The equivalent ratio is

, and the lean pre-mixed gas means that the equivalence ratio is 0.9 or less.)

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