A method for measuring temperature and concentration in engine combustion chamber

Abstract

The present invention discloses a method for measuring the temperature and concentration of an engine combustion chamber, and belongs to the technical field of temperature measurement. The method for measuring the temperature and concentration of an engine combustion chamber includes the following steps: selecting OH as a temperature measuring molecule, calculating the emission spectrum of OH, and obtaining a theoretical emission spectrum; normalizing the theoretical emission spectrum to obtain a normalized theoretical emission spectrum; using the radiation transmission effect to introduce a correction equation related to the flame temperature and the OH concentration to correct the normalized theoretical emission spectrum; establishing a mapping network between the actual emission spectrum and the flame temperature T and the OH concentration; and calculating the flame temperature T and the OH concentration according to the actual emission spectrum. The method for measuring the temperature and concentration of an engine combustion chamber described in the present invention can solve the problem of inaccurate temperature measurement in the existing supersonic combustion chamber, and can obtain the concentration of OH.

Description

Technical Field

[0001] The invention relates to the technical field of temperature measurement, and in particular to a method for measuring the temperature and concentration of an engine combustion chamber. Background Art

[0002] In the supersonic combustion chamber of an engine, obtaining the temperature or component concentration of the combustion process is an important guarantee for correctly calculating the combustion efficiency. In the supersonic combustion chamber, the air flow velocity is fast, the temperature is high, the oxidation is strong, and the working environment of the combustion chamber is harsh. The detection method must be able to withstand high temperature, high pressure, and high oxidation working conditions. Intrusive measurement cannot work properly because it interferes with the original flow field, and it is impossible to directly obtain the physical properties of the combustion field.

[0003] The existing patent CN202011077100.6 discloses a supersonic combustion chamber temperature measurement device and its measurement method based on deep learning. By selecting OH as the temperature measurement molecule, the A2Σ+-X2Π emission spectrum of OH is calculated; the OH after combustion is monitored outside the combustion chamber by using an optical fiber probe and transmitted to the spectrometer; a mapping network from emission spectrum to temperature is established through deep learning based on the broadening and signal-to-noise ratio of the spectrometer; the spectrometer and deep learning are integrated into the spectral device with the help of a hardware carrier, which contains The spectrum of the spectrum; the flame characteristic temperature is calculated instantly based on the observed value using the deep learning model. The above patent solves the problems of difficult observation of scramjet engines, complex and equipment-dependent traditional non-contact measurement methods, and inaccurate measurement methods based on emission spectra and poor noise suppression. However, during the transmission of electromagnetic waves in the combustion chamber, a radiation transmission effect occurs when the electromagnetic waves pass through the medium. Radiation transmission refers to the absorption, scattering and emission process that occurs when electromagnetic waves (such as visible light, infrared, ultraviolet rays, etc.) pass through a medium. When radiation passes through a medium, it may be absorbed or scattered by particles in the medium, and the medium may also spontaneously emit new radiation. Therefore, the radiation transmission effect affects the accuracy of the observed spectrum, and thus affects the accuracy of the measurement. Summary of the invention

[0004] The purpose of the present invention is to provide a method for measuring the temperature and concentration of an engine combustion chamber, so as to solve the problem of inaccurate temperature measurement in the existing supersonic combustion chamber.

[0005] To achieve the above object, the present invention provides a method for measuring the temperature and concentration of an engine combustion chamber, comprising the following steps:

[0006] S1. Select OH as the temperature measuring molecule and calculate the Emission spectrum, obtain theoretical emission spectrum;

[0007] S2, normalizing the theoretical emission spectrum to obtain a normalized theoretical emission spectrum;

[0008] S3. Calculate the emission spectrum under the radiation transfer effect, and calculate the correction equation according to the difference between the emission spectrum under the radiation transfer effect and the theoretical emission spectrum; the emission spectrum under the radiation transfer effect is:

[0009] ;

[0010] in, is the theoretical emission spectrum of OH single molecule, is the wavelength, is the absorption rate, is the emission source term, is the coordinate on the light path;

[0011] S4, establishing a mapping network between the actual emission spectrum and the flame temperature T and OH concentration;

[0012] S5. Calculate the flame temperature T and OH concentration based on the actual emission spectrum.

[0013] Preferably, in S2, the normalized theoretical emission spectrum is The calculation formula is

[0014] ;

[0015] in, is the emission spectrum of OH single molecule wavelength point, is the maximum value of the OH single molecule emission spectrum, For single molecule.

[0016] Preferably, in S3, the correction equation considering the second-order approximation is

[0017] ;

[0018] in, is the normalized absorbance, is the maximum absorption intensity, is the OH number density, is the absorption length.

[0019] Preferably, the normalized absorbance is

[0020] ;

[0021] ;

[0022] in, is the absorption rate, is the average gas density of OH molecules, is the average molar concentration of OH molecules, is Avogadro's constant, is the absorption spectrum intensity, is the gas molar mass of OH, is the maximum absorption rate.

[0023] The advantages and positive effects of the engine combustion chamber temperature and concentration measurement method described in the present invention are: the present invention uses the radiation transmission effect to introduce a correction equation for flame temperature and OH concentration in the normalized theoretical emission spectrum, corrects the theoretical emission spectrum, and improves the accuracy of combustion chamber flame temperature measurement. By using an existing algorithm to establish a mapping network between the actual emission spectrum and the flame temperature and OH concentration, the flame temperature and OH concentration can be obtained according to the actual emission spectrum.

[0024] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a flow chart of the method for measuring the temperature and concentration of the combustion chamber of an engine of the present invention;

[0026] Figure 2 The influence of radiation transfer effect on emission spectrum;

[0027] Figure 3 This is a flow chart of temperature and concentration calculation in an embodiment of the present invention;

[0028] Figure 4 OH concentration along the flame direction calculated for the embodiment of the present invention;

[0029] Figure 5 The flame temperature along the flame direction calculated for the embodiment of the present invention;

[0030] Figure 6 is the effect of OH concentration on the emission spectrum shift;

[0031] Figure 7 is the effect of absorption length on emission spectrum shift. DETAILED DESCRIPTION

[0032] In the description of the present invention, it should be noted that the terms "upper", "lower", "inside", "outside", etc. indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, or the positions or positional relationships in which the invented product is usually placed when in use. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention. In the description of the present invention, it should also be noted that, unless otherwise clearly specified and limited, the terms "setting", "installation", and "connection" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be an indirect connection through an intermediate medium, or it can be a connection between the two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0033] The embodiments of the present invention are described in detail below in conjunction with the accompanying drawings.

[0034] like Figure 1 A method for measuring the temperature and concentration of an engine combustion chamber comprises the following steps:

[0035] S1. Select OH as the temperature measuring molecule and calculate the Emission spectrum and obtain the theoretical emission spectrum.

[0036] The calculation method of the theoretical emission spectrum of OH is calculated using the method mentioned in the existing patent CN202011077100.6.

[0037] S2. Normalize the theoretical emission spectrum to obtain a normalized theoretical emission spectrum.

[0038] The normalized theoretical emission spectrum is calculated as follows:

[0039] ;

[0040] in, is the emission spectrum of OH single molecule wavelength point, is the maximum value of the OH single molecule emission spectrum, For single molecule.

[0041] S3, calculating the emission spectrum under the radiation transmission effect, and calculating the correction equation according to the difference between the emission spectrum under the radiation transmission effect and the theoretical emission spectrum;

[0042] The emission spectrum under the radiative transfer effect is:

[0043] ;

[0044] in, is the theoretical emission spectrum of OH single molecule, is the wavelength, is the OH single molecule absorption intensity, is the emission source term, is the coordinate on the light path.

[0045] The corrected equation is and The difference, through To consider the absorption effect, use its solution Single-molecule theoretical emission spectroscopy The difference between the absorption substance concentration and the corrected temperature is quantitatively obtained. After theoretical derivation, the second-order approximation of the difference is as follows:

[0046] ;

[0047] in, is the normalized absorbance, is the maximum absorption intensity, is the OH number density, is the absorption length.

[0048] Using the radiation transfer effect to introduce the modified equation The specific process is:

[0049] First, the influence of radiation transfer effect on the emission spectrum is explained.

[0050] The influence of radiation transfer effect on emission spectrum is as follows Figure 2 shown. Figure 2 The difference between the theoretical simulation spectra observed from different angles and the emission spectra corresponding to the maximum temperature of the observed path is shown. Figure 2 As shown in the figure, after considering the radiation transmission, the relative maximum value of the G1 emission peak changes. After 310nm, the radiation transmission effect causes these peaks to become relatively larger. This is due to the absorption effect, which is approximately

[0051] ;

[0052] For thin optical media, it is approximately But when When the distribution is no longer uniform, and the medium is thicker or the absorption rate is large enough, the observed spectrum will deviate from the distribution due to the existence of the second term. As a result, some peaks may not correspond to the theoretical spectrum.

[0053] When the thin optical medium assumption is established, the observed spectrum actually corresponds to the absolute intensity of the spectrum that can be observed. At this time, the absorption length, or the state of material aggregation, must be measured by setting a reference material for comparison without instrument calibration. This is a common view in the past. Under the influence of absorption, the distribution of the absorbing material will affect the normalized distribution of the spectrum.

[0054] The following analysis is conducted for a uniformly distributed one-dimensional luminescence scenario and shows the extent to which the distribution of absorbing material affects the radiation transfer effect.

[0055] The theoretical emission spectrum is denoted as , which is the normalized result of the single-molecule emission spectrum, Right now , the theoretical single molecule absorption intensity is , the normalized absorption intensity is The maximum absorption intensity is The following analysis only considers the changes in the wavelength dimension, and other variables are regarded as parameters.

[0056] ;

[0057] ;

[0058] in, is the normalized theoretical emission spectrum, is the emission spectrum at wavelength, is the maximum value of the emission spectrum.

[0059] The relationship between the single molecule absorption line intensity and the absorptivity is:

[0060] ;

[0061] The approximate absorption spectrum is

[0062] .

[0063] In thin optical media, the normalized spectrum captured experimentally is:

[0064] ;

[0065] in, is the average molecular molar concentration, is the molecular average gas density, is Avogadro's constant, is the maximum value of the first-order approximate spectral intensity.

[0066] If the instrument is not accurately calibrated, it is usually and Sal to analyze the captured emission spectra.

[0067] ;

[0068] In the expression Due to the effect of normalization, it will not actually be reflected in the normalized spectrum.

[0069] For the same situation, the approximate solution is expanded into two terms, and the theoretical observation spectrum of the second-order approximation is:

[0070] ;

[0071] Then the normalized result of the theoretical observation spectrum is:

[0072] ;

[0073] but

[0074] ;

[0075] , is the maximum value of the second-order approximate spectral intensity. In order to analyze the impact more specifically, in the independent variable v Perform equivalent infinitesimal analysis in the direction of change, consider the first-order infinitesimal, and record , since the original function is an increasing function, so the maximum value of the independent variable corresponds to The maximum value of

[0076] ;

[0077] but

[0078] ;

[0079] in, , is the normalized spectrum of the absorption line. In comparison, for the ideal case of the theoretical model, ,So

[0080] ;

[0081] but

[0082] .

[0083] In the case of first-order infinitesimal equivalence, the difference between two normalized spectra is and the distribution term in the wavelength dimension In addition to the constant term, is a normalized distribution in the wavelength dimension, which affects the peak shift. This distribution is related to the emission spectrum and the absorption spectrum. and The product of is related to The size of is related to temperature, and is the number density of the absorbing species, which can be expressed as ;but

[0084] .

[0085] It can be seen that under the influence of radiation transmission, the difference between the normalized spectrum and the theoretical molecular spectrum is Directly related to the number density of the absorbing species.

[0086] S4. Establish a mapping network between the actual emission spectrum and the flame temperature T and OH concentration.

[0087] In the actual application process, it is assumed that the actual emission spectrum is , calculate the actual shooting spectrum and single-molecule spectroscopy The difference between them can be used to construct traditional algorithms such as Newton-Raphson or other existing algorithms, such as iterative ,until ,exist Optimizing calculations in space And the emission spectrum captured The global minimum absolute value of is obtained, thereby obtaining the flame temperature T and OH concentration.

[0088] Figure 3 This is a flow chart of the embodiment of the present invention using the traversal algorithm to calculate the flame temperature and OH concentration. As shown in the figure, is the actual emission spectrum captured, The emission spectrum is corrected to take into account the absorption. ,get ,optimization ,get . judge <ε, ε is the set threshold. If the condition is met, the temperature is output and concentration , and get the temperature and concentration results. If the condition is not met, iterate and calculate the next temperature until the condition is met and output the temperature and concentration results.

[0089] The deep learning algorithm mentioned in the existing patent CN202011077100.6 can also be used to consider factors such as broadening and noise, and use the data mining capabilities of deep learning to obtain the network mapping relationship between the actual captured emission spectrum and the flame temperature T and OH concentration.

[0090] It is the OH concentration multiplied by the absorption length. In fact, the concentration can be obtained by calibrating the instrument. When the absorption length is unit 1, the algorithm constructed by calibrating the instrument obtains , the concentration is In application, the concentration measured by the calibrated instrument corresponds to the molecular number density when the unit length is 1.

[0091] Figure 4 The OH concentration along the flame direction calculated for the embodiment of the present invention is: Figure 5 The flame temperature along the flame direction calculated by the embodiment of the present invention.

[0092] S5. Calculate the flame temperature T and OH concentration based on the actual emission spectrum.

[0093] Figure 6 is the effect of OH concentration on the emission spectrum shift, Figure 7 is the effect of absorption length on emission spectrum shift. Figure 6 and Figure 7 It can be seen that, considering the medium emission, the component concentration and absorption length cause a shift in the normalized emission spectrum.

[0094] Therefore, the engine combustion chamber temperature and concentration measurement method of the present invention can solve the problem of inaccurate temperature measurement in the existing supersonic combustion chamber, and can obtain the OH concentration.

[0095] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that they can still modify or replace the technical solution of the present invention with equivalents, and these modifications or equivalent replacements cannot cause the modified technical solution to deviate from the spirit and scope of the technical solution of the present invention.

Claims

1. A method for measuring the temperature and concentration of an engine combustion chamber, characterized in that: The following steps are involved: S1. Select OH as the temperature measuring molecule and calculate the Emission spectrum, obtain theoretical emission spectrum; S2, normalizing the theoretical emission spectrum to obtain a normalized theoretical emission spectrum; S3, calculating the emission spectrum under the radiation transmission effect, and calculating the correction equation according to the difference between the emission spectrum under the radiation transmission effect and the theoretical emission spectrum; The emission spectrum under the radiative transfer effect is: ； in, is the theoretical emission spectrum of OH single molecule, is the wavelength, is the absorption rate, is the emission source term, is the coordinate on the light path; S4, establishing a mapping network between the actual emission spectrum and the flame temperature T and OH concentration; S5. Calculate the flame temperature T and OH concentration based on the actual emission spectrum.

2. The method for measuring the temperature and concentration in the combustion chamber of an engine according to claim 1, characterized in that: The S2 is the normalized theoretical emission spectrum of OH single molecule The calculation formula is ； in, is the emission spectrum of OH single molecule wavelength point, is the maximum value of the OH single molecule emission spectrum, For single molecule.

3. The method for measuring the temperature and concentration of an engine combustion chamber according to claim 2, characterized in that: In S3, the modified equation considering the second-order approximation is: ； in, is the normalized absorbance, is the maximum absorption intensity, is the OH number density, is the absorption length.

4. The method for measuring the temperature and concentration in the combustion chamber of an engine according to claim 3, characterized in that: The normalized single molecule absorption intensity is ； ； in, is the average gas density of OH molecules, is the average molar concentration of OH molecules, is Avogadro's constant, is the absorption spectrum intensity, is the gas molar mass of OH, is the maximum absorption rate.

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