A method for characterizing the heat release rate of a liquid mist swirl flame based on chemiluminescence

Abstract

The present application relates to a kind of liquid mist swirl flame heat release rate characterization method based on chemiluminescence, it is related to combustion test and diagnosis field, include three kinds of respectively based on single-component free radical chemiluminescence, double-component free radical chemiluminescence and three-component free radical chemiluminescence to the quantitative calculation model of combustion heat release rate (HRR).The model is suitable for the quantitative calculation of liquid mist swirl flame heat release rate, is the reliable index of flame heat release rate.The present application is suitable for the liquid mist swirl flame combustion of various industrial grade applications such as ethanol, aviation kerosene, methanol, biomass fuel etc., has practical significance to the flame control and monitoring of industrial combustion.

Description

Technical Field

[0001] This invention belongs to the field of combustion diagnostics and testing technology, and particularly relates to a method for characterizing and calculating the heat release rate of liquid mist swirling flames based on chemiluminescence. Background Technology

[0002] Liquid atomization combustion is widely used in energy and power devices such as heavy-duty gas turbines, aero engines, oil and gas boilers, and liquid rocket engines. Its principle involves atomizing liquid fuel into micron-sized droplets through a nozzle. After the droplets evaporate upon heating, they mix with swirling air, achieving complete combustion. To improve combustion efficiency and monitor and control combustion instability, monitoring and controlling the heat release rate (HRR) and reaction degree of the liquid atomization swirling flame are crucial industrial problems that need to be solved. However, the heat release rate in actual combustion processes is difficult to measure directly. Therefore, establishing an index that can reliably characterize the heat release rate is essential. In experiments, researchers typically use parameters proportional to the heat release rate to indirectly measure the flame heat release rate.

[0003] One of the most commonly used diagnostic techniques for hydrocarbon fuel flames is measuring the chemiluminescence radiation of the flame. The principle of chemiluminescence is that the large amount of energy released during fuel combustion excites the gas and solid phases, generating a series of excited-state free radicals. When these excited-state free radicals transition back to lower energy levels, they emit photons of a specific frequency, resulting in luminescence. Because chemiluminescence occurs in a narrow region close to the reaction zone and is instantaneous, it is directly related to the equivalence ratio of combustion, the heat release rate, and other parameters.

[0004] However, currently regarding OH * CH * C2 * The correlation between the chemiluminescence intensity of free radicals and the flame heat release rate is only applicable to simple gaseous fuel flames and remains at the qualitative characterization stage. Compared to gaseous fuels, research on chemiluminescence in liquid mist swirling flames commonly used in industry, such as in aero engines and gas turbines, is even scarcer. Whether the relationship between free radical chemiluminescence and flame heat release rate is applicable, or its applicable boundaries, remains unclear in current research. Furthermore, the accuracy of calculating chemiluminescence and flame heat release rate using conventional mathematical models is currently very low, making them unsuitable as indicators of heat release rate. Therefore, to achieve monitoring and control of heat release rate in liquid mist swirling flames in industry, a characterization method applicable to the combustion heat release rate of liquid fuels is urgently needed. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a rapid and accurate method for characterizing the heat release rate of combustion of liquid fuels.

[0006] To solve the above-mentioned technical problems, the present invention is achieved through the following three technical solutions:

[0007] Technical Solution 1:

[0008] A method for characterizing the heat release rate of a liquid mist swirling flame based on chemiluminescence includes:

[0009] Obtain OH- spontaneously generated during the combustion of liquid fuels * CH * and C2 * The chemiluminescence intensity of any one of the three free radicals;

[0010] Based on the chemiluminescence intensity of any free radical, the thermal release rate of the liquid fuel mist swirling flame is obtained:

[0011]

[0012]

[0013]

[0014] In the formula, HRR is the heat release rate of the liquid fuel mist swirling flame; α1, α2, and α3 are the values ​​of OH used respectively. * CH * and C2 * Chemiluminescence intensity is used as the independent variable to calculate the corresponding power coefficient of the heat release rate; k1, b1, k2, b2, k3, b3 are the corresponding linear coefficients.

[0015] The method for determining the coefficients α1, α2, α3, k1, b1, k2, b2, k3, and b3 is as follows:

[0016] The flame heat release rate was calculated based on the experimental conditions of different fuels and nonlinearly fitted with the collected free radical chemiluminescence intensity according to formulas (1)-(3) to obtain the OH- * CH * and C2 * The correction factor for calculating the flame thermal release rate based on the chemiluminescence intensity of any one of the three free radicals.

[0017] Technical Solution Two:

[0018] A method for characterizing the heat release rate of a liquid mist swirling flame based on chemiluminescence includes:

[0019] Obtain OH- spontaneously generated during the combustion of liquid fuels * CH * and C2 * The chemiluminescence intensity of any two of the three free radicals;

[0020] Based on the chemiluminescence intensity of any two free radicals, the thermal release rate of the liquid fuel mist swirling flame is obtained:

[0021]

[0022]

[0023]

[0024] In the formula, HRR is the heat release rate of the liquid fuel mist swirling flame; β1, γ1, β2, γ2, β3, and γ3 are the values ​​of OH groups respectively. * CH * and C2 * The corresponding power coefficients for calculating the heat release rate are given as independent variables for the chemiluminescence intensity of any two free radicals; k4, b4, k5, b5, k6, and b6 are the corresponding linear coefficients.

[0025] The method for determining the coefficients β1, γ1, β2, γ2, β3, γ3, k4, b4, k5, b5, k6, b6 is as follows:

[0026] The flame heat release rate was calculated based on the experimental conditions of different fuels and nonlinearly fitted with the collected free radical chemiluminescence intensity according to formulas (4)-(6) to obtain the OH- * CH * and C2 * The correction factor for calculating the flame thermal release rate is the chemiluminescence intensity of any two of the three free radicals.

[0027] Technical Solution 3:

[0028] A method for characterizing the heat release rate of a liquid mist swirling flame based on chemiluminescence includes:

[0029] Obtain OH- spontaneously generated during the combustion of liquid fuels * CH * and C2 * Chemiluminescence intensities of three free radicals;

[0030] Based on the chemiluminescence intensity of three free radicals, the thermal release rate of the liquid fuel mist swirling flame was obtained:

[0031] HRR=k7*OH x *CH y *C2 z +b7 (7)

[0032] In the formula, HRR is the heat release rate of the liquid fuel mist swirl flame; x, y, z are the values ​​of the heat release rate using OH- * CH *and C2 * The intensity of the triradical chemiluminescence is used as the independent variable to calculate the corresponding power coefficient of the heat release rate; k7 and b7 are the corresponding linear coefficients.

[0033] The method for determining the coefficients x, y, z, k7, and b7 is as follows:

[0034] The flame heat release rate was calculated based on the experimental conditions of different fuels and nonlinearly fitted with the collected free radical chemiluminescence intensity according to formula (7) to obtain the OH- * CH * and C2 * Correction factors for calculating the flame thermal release rate using the chemiluminescence intensity of three free radicals.

[0035] Compared with the prior art, the beneficial effects of the present invention are:

[0036] 1. The present invention characterizes the heat release rate by collecting the free radical chemiluminescence intensity of liquid mist swirling flames, thereby realizing a method for characterizing the heat release rate of industrial-grade liquid mist swirling flames. This method can be used to calculate the heat release rate of combustion of various liquid fuels commonly used in industrial combustion, and has practical significance for improving combustion efficiency and monitoring and controlling combustion instability.

[0037] 2. The characterization method of the present invention is based on the spontaneous chemiluminescence radiation of flame. The measurement process does not require external means such as lasers. The measurement equipment is simple and has the advantages of low cost and instantaneous measurement. The heat release rate is directly obtained from the intensity of free radical chemiluminescence, which is fast and efficient.

[0038] 3. The model used in the characterization method of this invention has better accuracy than the models of other conventional fitting algorithms, especially the two-component model and the three-component model. Attached Figure Description

[0039] Figure 1 C2 in Embodiment 1 of the present invention * Chemiluminescence-HRR raw data;

[0040] Figure 2 Graph of single-component free radical chemiluminescence-HRR calculation model in Example 1 of this invention;

[0041] Figure 3 CH in Embodiment 2 of the present invention * C2 * Chemiluminescence-HRR raw data distribution;

[0042] Figure 4 This is a data graph of the two-component free radical chemiluminescence-HRR calculation model in Example 2 of the present invention;

[0043] Figure 5This is a data graph of the three-component free radical chemiluminescence-HRR calculation model in specific embodiment 3. Detailed Implementation

[0044] To more intuitively illustrate the calculation accuracy of the model proposed in this invention, the invention will be further described in detail below with reference to specific embodiments.

[0045] This invention provides a method for using OH spontaneously generated during combustion * (310nm), CH * (430nm), C2 * This method uses the spontaneous chemiluminescence radiation intensity of three free radicals (515 nm) and their combinations as variables to quantitatively characterize and calculate the combustion heat release rate. It includes three models based on single-component, two-component, and three-component free radical chemiluminescence, respectively, to quantitatively calculate the combustion heat release rate. The calculation models are empirical formulas derived from extensive experimental data and are applicable to calculating the heat release rate of liquid mist swirling flames using different fuels. The specific application method for any fuel is as follows:

[0046] 1. A light-collecting system is used to acquire the chemiluminescence signal emitted by the flame, and the light signal is collected to the corresponding chemiluminescence measurement equipment, such as a spectrometer or photomultiplier tube (PMT). Filters of the corresponding wavelength band are installed in front of the measurement equipment according to the desired spontaneous emission wavelength of the free radical, and the measured chemiluminescence intensity of the free radical is recorded.

[0047] 2. Calculate the heat release rate of the flame under specific operating conditions according to the reference formula.

[0048] 3. The flame heat release rate under specific working conditions in step 2 and the collected free radical chemiluminescence intensity are nonlinearly fitted according to the mathematical model provided by this invention to obtain the calculation correction coefficient applicable to the fuel.

[0049] 4. Substituting the correction coefficients obtained in step 3 into the model can be used to calculate the heat release rate of the fuel under any operating conditions.

[0050] Note: Only one calibration test is needed for each fuel to determine its correction factor, which can then be used to calculate the heat release rate of that fuel under any operating conditions.

[0051] The specific calculation model proposed in this invention is as follows:

[0052] (1) Single-component free radical chemiluminescence-HRR

[0053]

[0054]

[0055]

[0056] In the formula, HRR is the heat release rate of the liquid fuel mist swirling flame, and α1, α2, and α3 are the values ​​of OH used respectively. * CH * and C2 * Chemiluminescence intensity is used as the independent variable to calculate the corresponding power coefficient of the heat release rate. k1, b1, k2, b2, k3, b3 are the corresponding linear coefficients.

[0057] (2) Two-component radical chemiluminescence-HRR

[0058]

[0059]

[0060]

[0061] In the formula, HRR is the heat release rate of the liquid fuel mist swirling flame; β1, γ1, β2, γ2, β3, and γ3 are the values ​​of OH groups respectively. * CH * and C2 * The corresponding power coefficients for calculating the heat release rate are used as independent variables for the chemiluminescence intensities of any two free radicals. k4, b4, k5, b5, k6, and b6 are the corresponding linear coefficients.

[0062] (3) Three-component radical chemiluminescence-HRR

[0063] HRR=k7*OH x *CH y *C2 z +b7

[0064] In the formula, HRR is the heat release rate of the liquid fuel mist swirl flame; x, y, z are the values ​​of the heat release rate using OH- * CH * and C2 * The triradical chemiluminescence intensity is used as the independent variable to calculate the corresponding power coefficient of the heat release rate. k7 and b7 are the corresponding linear coefficients.

[0065] The overall quantitative characterization effect of the three models on HRR is as follows: three-component > two-component > one-component.

[0066] Example 1:

[0067] Using the aforementioned single-component radical chemiluminescence-HRR calculation model, the C2O2 content in the liquid mist swirl flames of four liquid fuels (ethanol, aviation kerosene, sustainable aviation kerosene, and n-heptane) was analyzed. * Chemiluminescence intensity and HRR were calculated and analyzed, and the process and results are as follows:

[0068] 1. A light-collecting system is used to acquire the light signal of the liquid mist swirling flame, which is then fed into a photomultiplier tube. A 515nm filter is installed in front of the photomultiplier tube to record C2. * The chemiluminescence intensity was used for data analysis. After performing background noise reduction, transmittance correction, and instrument response correction on the collected chemiluminescence, accurate free radical chemiluminescence intensity was obtained.

[0069] 2. Calculate the heat release rate of the flame under specific operating conditions using the reference formula. The experimental operating conditions for each fuel are determined by both air velocity and equivalence ratio, with an air velocity of 5 m / s and an equivalence ratio of 0.05 as the interval. The experimental operating condition ranges for each fuel are as follows:

[0070]

[0071] 3. Using the C2 proposed in this invention * A single-component free radical chemiluminescence-HRR calculation model was used to analyze the C2 of each fuel under different operating conditions in step 2. * Nonlinear fitting of chemiluminescence intensity with HRR yielded four C2 fuels: ethanol, aviation kerosene, sustainable aviation kerosene, and n-heptane. * Model correction coefficients α3, k3, b3 for calculating HRR using single radical chemiluminescence.

[0072] 4. Substitute the coefficients α3, k3, and b3 obtained in step 3 into C2. * A single-component free radical chemiluminescence-HRR calculation model. The obtained model can be used to calculate the HRR under any operating condition, and correlation analysis (i.e., accuracy verification) can be performed with the original results.

[0073] The fitting results for α3, k3, and b3 for the four fuels mentioned above in Example 1 are as follows:

[0074]

[0075] The table below compares the C2 values ​​of four fuels calculated using conventional one-dimensional mathematical models (linear, exponential, polynomial, trigonometric functions, etc.). * Based on the HRR correlation coefficient and the results of the single-component free radical chemiluminescence model proposed in this invention, the four one-dimensional mathematical model expressions are as follows:

[0076] Linear model: HRR = k8 * C2 + b8

[0077] Exponential model: HRR = k9 * exp(c1 * C2)

[0078] Polynomial model: HRR = k 10 *C2 2 +k 11 *C2+b10

[0079] Trigonometric function model: HRR = k 12 *sin(c2*C2+b 11 )

[0080] In the formula, k, b, and c with different subscripts are the coefficients of the corresponding one-dimensional model.

[0081]

[0082] By comparing the fitting correlation coefficients of various HRRs calculated by conventional models with the original data in the table, it can be seen that the single-component free radical chemiluminescence-HRR model proposed in this invention can improve the accuracy of HRR calculation by 20%-40% and is applicable to a variety of liquid fuels.

[0083] Example 2:

[0084] Using the aforementioned two-component radical chemiluminescence-HRR calculation model, the CH4 content in the liquid mist swirl flame of four liquid fuels (ethanol, aviation kerosene, sustainable aviation kerosene, and n-heptane) was analyzed. * C2 * Chemiluminescence intensity and HRR were calculated and analyzed, and the process and results are as follows:

[0085] 1. A light-collecting system is used to acquire the light signal from the liquid mist swirling flame, which is then fed into a photomultiplier tube. A dichroic mirror is used to split the light signal into two paths. 430nm and 515nm filters are installed before the photomultiplier tubes corresponding to the two light signals to record the CH (chromatic atomization). * C2 * The chemiluminescence intensity was used for data analysis. After performing background noise reduction, transmittance correction, and instrument response correction on the collected chemiluminescence, accurate free radical chemiluminescence intensity was obtained.

[0086] 2. Calculate the heat release rate of the flame under specific operating conditions according to the reference formula. The experimental conditions for each fuel are the same as in Example 1:

[0087]

[0088] 3. Using the CH proposed in this invention * C2 * A two-component free radical chemiluminescence-HRR calculation model was used to analyze the CH4 of each fuel under different operating conditions in step 2. * C2 * Nonlinear fitting of chemiluminescence intensity with HRR yielded results for four fuels: ethanol, aviation kerosene, sustainable aviation kerosene, and n-heptane. * C2 * Model correction coefficients β3, γ3, k6, b6 for calculating HRR using two types of free radical chemiluminescence.

[0089] 4. Substitute the obtained β3, γ3, k6, and b6 coefficient values ​​into CH. * C2 * A two-component free radical chemiluminescence-HRR calculation model was developed. The resulting model can be used to calculate the HRR under any operating condition, and correlation analysis was performed with the original results to verify accuracy.

[0090] The fitting results for β3, γ3, k6, and b6 for the four fuels mentioned above in Example 2 are as follows:

[0091]

[0092] The table below shows the CH* and C2 values ​​for four fuels calculated using conventional two-dimensional mathematical models (linear and polynomial). * -HRR correlation coefficient and the results of the two-component free radical chemiluminescence model proposed in this invention, the two two-dimensional mathematical model expressions are as follows:

[0093] Two-dimensional linear model: HRR = p1*CH + p2*C2 + p3

[0094] Two-dimensional polynomial model:

[0095] HRR=p4+p5*CH+p6*C2+p7*CH 2 +p8*C2 2 +p9*CH*C2

[0096] In the formula, p1-p9 are the coefficients of the corresponding two-dimensional model.

[0097]

[0098] The results above show that the proposed two-component radical chemiluminescence-HRR model has a significantly higher computational accuracy than conventional mathematical models and is applicable to various liquid fuels. Furthermore, comparing the fitting correlation coefficient of the single-component radical chemiluminescence model in Example 1, it is evident that using two-component radical chemiluminescence to calculate HRR can further improve accuracy.

[0099] Example 3:

[0100] Using the aforementioned three-component radical chemiluminescence-HRR calculation model, the OH groups in the liquid mist swirl flame of ethanol fuel were analyzed. * CH * C2 * Chemiluminescence intensity and HRR were calculated and analyzed, and the process and results are as follows:

[0101] 1. A light-collecting system is used to acquire the light signal from the liquid mist swirling flame, which is then fed into a photomultiplier tube. Two dichroic mirrors are used to separate the light signal twice, creating three optical paths. 310nm, 430nm, and 515nm filters are then installed before the photomultiplier tubes corresponding to the three light signals to record the OH light. * CH * C2 * The chemiluminescence intensity was used for data analysis. After performing background noise reduction, transmittance correction, and instrument response correction on the collected chemiluminescence, accurate free radical chemiluminescence intensity was obtained.

[0102] 2. Calculate the heat release rate of the liquid mist swirl flame for ethanol fuel under the following operating conditions using the reference formula:

[0103]

[0104] 3. Using the three-component free radical chemiluminescence-HRR calculation model proposed in this invention, the OH under the experimental conditions in step 2 was analyzed. * CH * C2 * Nonlinear fitting of chemiluminescence intensity with HRR yielded results for OH- ethanol, aviation kerosene, sustainable aviation kerosene, and n-heptane fuels. * CH * C2 * Model correction coefficients x, y, z, k7, b7 for calculating HRR using three types of free radical chemiluminescence.

[0105] 4. Substitute the obtained x, y, z, k7, and b7 coefficients into OH. * CH * C2 * A three-component free radical chemiluminescence-HRR calculation model. The obtained model can be used to calculate the HRR under any operating condition, and correlation analysis is performed with the original results, i.e., accuracy verification.

[0106] The fitting results are: x = 1.0464, y = -0.3933, z = 0.0304, k7 = 39627, b7 = 3.0348.

[0107] OH in the liquid mist swirl flame of ethanol fuel * CH * C2 * The correlation coefficient between the three-component radical chemiluminescence-HRR calculation results and the original HRR data is 0.9966, proving that the three-component chemiluminescence-HRR model proposed in this invention has extremely high calculation accuracy for HRR.

[0108] The applicant declares that the above content is a further detailed description of the present invention in conjunction with specific ethanol, aviation kerosene, sustainable aviation kerosene, and n-heptane liquid fuels. The present invention is not limited to these four fuels, but is also applicable to any hydrocarbon liquid fuel in industrial applications.

Claims

1. A method for characterizing the heat release rate of a liquid mist swirling flame based on chemiluminescence, characterized in that, include: Obtain OH- spontaneously generated during the combustion of liquid fuels * CH * and C2 * The chemiluminescence intensity of any one of the three free radicals; Based on the chemiluminescence intensity of any free radical, the thermal release rate of the liquid fuel mist swirling flame is obtained: In the formula, HRR is the heat release rate of the liquid fuel mist swirling flame; α1, α2, and α3 are the values ​​of OH used respectively. * CH * and C2 * Chemiluminescence intensity is used as the independent variable to calculate the corresponding power coefficient of the heat release rate; k1, b1, k2, b2, k3, b3 are the corresponding linear coefficients.

2. The method for characterizing the heat release rate of a liquid mist swirling flame based on chemiluminescence according to claim 1, characterized in that, The method for determining the coefficients α1, α2, α3, k1, b1, k2, b2, k3, and b3 is as follows: The flame heat release rate was calculated based on the experimental conditions of different fuels and nonlinearly fitted with the collected free radical chemiluminescence intensity according to formulas (1)-(3) to obtain the OH- * CH * and C2 * The correction factor for calculating the flame thermal release rate based on the chemiluminescence intensity of any one of the three free radicals.

3. A method for characterizing the heat release rate of a liquid mist swirling flame based on chemiluminescence, characterized in that, include: Obtain OH- spontaneously generated during the combustion of liquid fuels * CH * and C2 * The chemiluminescence intensity of any two of the three free radicals; Based on the chemiluminescence intensity of any two free radicals, the thermal release rate of the liquid fuel mist swirling flame is obtained: In the formula, HRR is the heat release rate of the liquid fuel mist swirling flame; β1, γ1, β2, γ2, β3, and γ3 are the values ​​of OH groups respectively. * CH * and C2 * The corresponding power coefficients for calculating the heat release rate are given as independent variables for the chemiluminescence intensity of any two free radicals; k4, b4, k5, b5, k6, and b6 are the corresponding linear coefficients.

4. The method for characterizing the thermal release rate of a liquid mist swirling flame based on chemiluminescence according to claim 3, characterized in that, The method for determining the coefficients β1, γ1, β2, γ2, β3, γ3, k4, b4, k5, b5, k6, b6 is as follows: The flame heat release rate was calculated based on the experimental conditions of different fuels and nonlinearly fitted with the collected free radical chemiluminescence intensity according to formulas (4)-(6) to obtain the OH- * CH * and C2 * The correction factor for calculating the flame thermal release rate is the chemiluminescence intensity of any two of the three free radicals.

5. A method for characterizing the heat release rate of a liquid mist swirling flame based on chemiluminescence, characterized in that, include: Obtain OH- spontaneously generated during the combustion of liquid fuels * CH * and C2 * Chemiluminescence intensities of three free radicals; Based on the chemiluminescence intensity of three free radicals, the thermal release rate of the liquid fuel mist swirling flame was obtained: HRR=k7*OH x *CH y *C2 z +b7 (7) In the formula, HRR is the heat release rate of the liquid fuel mist swirl flame; x, y, z are the values ​​of the heat release rate using OH- * CH * and C2 * The intensity of the triradical chemiluminescence is used as the independent variable to calculate the corresponding power coefficient of the heat release rate; k7 and b7 are the corresponding linear coefficients.

6. The method for characterizing the heat release rate of a liquid mist swirling flame based on chemiluminescence according to claim 5, characterized in that, The method for determining the coefficients x, y, z, k7, and b7 is as follows: The flame heat release rate was calculated based on the experimental conditions of different fuels and nonlinearly fitted with the collected free radical chemiluminescence intensity according to formula (7) to obtain the OH- * CH * and C2 * Correction factors for calculating the flame thermal release rate using the chemiluminescence intensity of three free radicals.

Images