CN104391132B - Device and method for measuring engine combustion flow field speed based on molecular absorption spectrum - Google Patents

Abstract

The invention provides a device and a method for measuring engine combustion flow field speed based on molecular absorption spectrum. The measuring device comprises a laser setting unit, a laser beam-splitting unit, a measuring unit, a data acquiring system and a data processing unit, wherein the laser beam-splitting unit and the laser setting unit are connected and positioned at one side of an engine combustion flow field; the measuring unit comprises two laser detectors which are positioned at the other side of the engine combustion flow field and opposite to the laser beam-splitting unit; the data processing unit is used for processing data stored in the data acquiring system to obtain the fuel flow field speed. Based on the molecular absorption spectrum, a laser decaying pulse signal caused by fuel gas component concentration changes is used as a cross-correlation analysis random signal to realize cross-correlation speed measurement, so that the device and the method for measuring engine combustion flow field speed based on molecular absorption spectrum provided by the invention can obtain relevant data by only needing to enable laser to pass through a to-be-tested combustion flow field. The device has the advantages of a simple structure, a non-contact type and high sensitivity.

Description

Engine burn flow field velocity measuring device and method based on molecular absorption spectrum

Technical field

The invention belongs to flow field velocity field tests, and in particular to a kind of engine burn flow based on molecular absorption spectrum Field velocity measuring device and method.

Background technology

In engine combustion flow field in aero-engine, rocket engine etc. with hydrocarbon as fuel, flow field speed Degree is one of analysis fired state, the important parameter of engine evaluated performance.But due to flow field velocity and gas flow temperature it is higher, And burning, Multiphase Flow, heat and mass transfer process are sufficiently complex, and to measurement many difficulties are brought.

At present, the measuring method of conventional engine burn flow field speed degree is intrusive mood measuring method and image measurement method. Intrusive mood measuring method is placed in test component in flow field, not only easy interference flowing field, or even can cause the change in flow field, and ties Fruit generally needs further amendment, and precision is not high；Image measurement method generally needs stream field to add trace particle, and for engine For Combustion Flow Field, it is uniformly added into that trace particle is more difficult in flow field, while trace particle image is easily by very strong burning Flare up fire is fallen into oblivion, and trace particle can also affect burning.

The content of the invention

The present invention is carried out to solve the above problems, based on molecular absorption spectrum, with Gas Components in Combustion Flow Field The laser intensity change that change in concentration is caused is turned to fluctuating signal, by the cross-correlation of the fluctuating signal of the beam laser of upstream and downstream two point Analysis, obtains the cross-correlation transition time, and with reference to the spacing of two beam laser, calculates Combustion Flow Field tachometric survey, there is provided Yi Zhongfei Engine burn flow field velocity measuring device and method of the contact based on molecular absorption spectrum, realizes high temperature and high speed Combustion Flow Field Tachometric survey, further improve the ease of existing flow field velocity measurement apparatus, at the same improve measurement sensitivity.

Present invention employs following technical scheme：

The engine burn flow field velocity measuring device based on molecular absorption spectrum that the present invention is provided, starts for measurement Flow field velocity in machine Combustion Flow Field, has the feature that, including：Laser setup unit, for setting the work of laser instrument Wavelength and intensity；Laser beam splitter unit, positioned at engine combustion flow field side, including the laser for exporting laser setup unit point Into the laser beam splitter of two beams；Measuring unit, it is relative positioned at engine combustion flow field opposite side, and laser beam splitter unit, including Transmitted light laser detector of the two beam laser of two reception laser beam splitter unit output Jing after Combustion Flow Field to be measured；And data Processing unit, is processed the signal of probe unit, obtains Combustion Flow Field speed.

The engine burn flow field velocity measuring device based on molecular absorption spectrum that the present invention is provided, can also allow with this The feature of sample, also includes：Data collecting system, for laser intensity signal and data processing list that record preserves measuring unit The result of unit.

The engine burn flow field velocity measuring device based on molecular absorption spectrum that the present invention is provided, can also allow with this The feature of sample：Laser setup unit and laser beam splitter unit are connected by optical fiber.

The engine burn flow field velocity measuring device based on molecular absorption spectrum that the present invention is provided, can also allow with this The feature of sample：Laser beam splitter unit also include two collimaters, laser beam splitter connection, for laser beam splitter is separated two Shu Guang is exported in the way of perpendicular to flow field direction and along the axially in parallel arrangement in flow field.

Further, present invention also offers a kind of engine burn flow field tachometric survey side based on molecular absorption spectrum Method, it is characterised in that comprise the following steps：

The modulation of laser works wavelength is arrived selected Gas Components molecular absorption line by step 1, laser setup unit, than Such as H₂The 7185.597cm of O molecules^-1、7168.437cm^-1Deng；

Step 2, laser beam splitter unit is divided into the laser that laser setup unit is exported axially flat along Combustion Flow Field to be measured Two beams of row arrangement, and by the incident engine combustion flow field to be measured of two beam laser verticals, transmitted light by opposite laser acquisition list Unit receives；

Step 3, data processing unit is processed the signal of probe unit, obtains Combustion Flow Field speed.

The engine burn flow field speed measurement method based on molecular absorption spectrum that the present invention is provided, can also allow with this The feature of sample：Data processing unit as random signal x (t) and y (t) of cross-correlation analysis, opens two laser transmission signals Open up the cross-correlation function analysis of two signals：

Wherein, T is the integral mean time, and τ is time variable, R_xy(τ) in τ=τ₀Maximum is reached, cross-correlated signal Transition time is τ₀。

The engine burn flow field speed measurement method based on molecular absorption spectrum that the present invention is provided, can also allow with this The feature of sample：The computational methods of Combustion Flow Field speed are：V_avg=d/ τ₀, wherein d is the distance between two beam laser.

Invention effect and effect

The invention provides a kind of engine burn flow field velocity measuring device and method based on molecular absorption spectrum, surveys Trial assembly is put including laser setup unit, laser beam splitter unit, measuring unit, data collecting system and data processing unit, is swashed Light beam splitting unit is connected by optical fiber and laser setup unit, and positioned at engine combustion flow field side, measuring unit includes two Laser detector, data processing unit, for logarithm relative positioned at engine combustion flow field opposite side, and laser beam splitter unit Processed according to the data stored in acquisition system, obtained Combustion Flow Field speed, because the present invention is based on molecular absorption spectrum, will The laser attenuation fluctuating signal that Gas Components change in concentration is caused realizes that cross-correlation tests the speed as the random signal of cross-correlation analysis, So that the engine burn flow field velocity measuring device based on molecular absorption spectrum and method of present invention offer only need two Beam determines that the laser of wavelength obtains related data by passing through Combustion Flow Field to be measured, by processing related data, can obtain To Combustion Flow Field speed, the shortcomings of overcoming the easy interference flowing field of contact type measurement method, affect burning, with simple structure, non-connect The high advantage of touch, sensitivity.

Description of the drawings

Fig. 1 is the structural representation of the engine burn flow field velocity measuring device based on molecular absorption spectrum of the present invention Figure；

Fig. 2 is the flow chart of the engine burn flow field speed measurement method based on molecular absorption spectrum of the present invention.

Specific embodiment

Below in conjunction with the specific embodiment of concrete this explanation of accompanying drawing.

Fig. 1 is the structural representation of the engine burn flow field velocity measuring device based on molecular absorption spectrum of the present invention Figure.

As shown in figure 1, the engine burn flow field velocity measuring device 100 based on molecular absorption spectrum sets including laser Unit 1, laser beam splitter unit 2, measuring unit 4, data collecting system 5 and data processing unit 6, laser setup unit 1 leads to Cross optical fiber 3 and laser beam splitter unit 2 connects, laser beam splitter unit 2 is located at the Combustion Flow Field to be measured 20 after engine burner 10 Side, measuring unit is located at the opposite side of Combustion Flow Field to be measured 20, and laser beam splitter unit 2 is relative, data collecting system 5 one End and measuring unit 4 connect, and the other end and data processing unit 6 connect.

Laser setup unit 1 includes laser controller 11 and laser instrument 12, and laser controller 11 is used to modulate laser instrument 12 Operation wavelength and intensity；Laser beam splitter unit 2 includes 1 × 2 laser beam splitter 21 and collimater 22 and collimater 23, collimation Device 22 and collimater 23 keep at a certain distance away and are placed in parallel, the laser that 1 × 2 laser beam splitter 21 transmits in laser instrument 12 point Into two beams, respectively laser of two beams along the axially in parallel arrangement of Combustion Flow Field is output as by collimater 22 and collimater 23：Laser 221 With laser 231, perpendicular to flow field direction, spacing is d for laser 221 and laser 231；Measuring unit 4 includes the He of laser detector 41 Laser detector 42, it is relative with collimater 22 and collimater 23 respectively, for receiving laser 221 and the Jing of laser 231 burnings to be measured Transmitted light behind flow field, and convert optical signals to voltage signal；Data collecting system 5 is used for record and preserves laser detector spy The voltage signal of survey and the result of data processing unit；Data processing unit 6 is used for the electricity in data collecting system 5 Pressure signal carries out cross-correlation analysis, obtains the transition time of two signals, and basis signal transition time computational flow speed.

Fig. 2 is the flow process of the engine burn flow field speed measurement method based on molecular absorption spectrum in the present embodiment Figure.

As shown in Fig. 2 being comprised the following steps based on the engine burn flow field speed measurement method of molecular absorption spectrum：

Step 1, determines the key component of combustion gas, such as H₂O、CO₂、O₂Deng, by the molecular absorption spectrum for consulting each component, Stronger molecular absorption line is selected as the operation wavelength of laser instrument；

Step 2, is inhaled the operation wavelength modulation of laser instrument 12 to selected Gas Components molecule using laser controller 11 Receive spectral line；

Step 3, laser instrument 11 is live to engine test by Laser Transmission by optical fiber 3, and using 1 × 2 laser beam splitter Laser is divided into two beams, two beam laser difference collimator 22 and collimater 23 by device 21, is formed perpendicular to flow field direction, and spacing is The laser 221 and laser 231 of d；

Step 4, laser 221 and laser 231 parallel through Combustion Flow Field to be measured 20, and respectively by the laser detector on opposite 41 and laser detector 42 receive, while converting optical signals to electric signal；

Step 5, the signal of two laser detectors of data collecting system real time record；

Step 6, random signal x (t) and y of the data processing unit using the transmission signal of two laser as cross-correlation analysis T (), carries out the cross-correlation function analysis of two signals：

And try to achieve signal transit time τ₀；

Step 7, data processing unit obtains Combustion Flow Field speed V according to cross-correlation measuring principle_avg：V_avg=d/ τ₀, and The Combustion Flow Field speed that process is obtained, in being stored in data collecting system.

In the present embodiment, when laser is by Combustion Flow Field to be measured, if laser frequency v and GAS ABSORPTION composition transitions frequency Identical, then laser energy is absorbed, and due to molecule absorption, laser intensity decay, attenuation is described by Beer Lambert law： Incident intensity meets with transmitted light intensity：

I_t/I_i=exp (- k_vL)

Wherein, I_iFor incident laser light intensity；I_tFor laser by length for L area to be measured after transmitted light intensity；k_vFor spectrum suction Coefficient is received, it is proportional with concentration；L is the distance between collimater and laser detector.

Understand that the laser for determining wavelength, can be by corresponding group behind combustion zone to be measured by Beer Lambert law Divide and absorb, and laser attenuation amount is directly proportional to concentration.

In the present embodiment, due to burn pulse characteristic, concentration of component with time pulsatile change, according to Bill-Lambert Law understands the transmitted light intensity of two beam laser also not stopping pulsatile change with the time, therefore data collecting system needs real time record two The signal of individual laser detector.

Embodiment is acted on and effect

A kind of engine burn flow field velocity measuring device based on molecular absorption spectrum and method are present embodiments provided, Test device includes laser setup unit, laser beam splitter unit, measuring unit, data collecting system and data processing unit, Laser beam splitter unit is connected by optical fiber and laser setup unit, and positioned at engine combustion flow field side, measuring unit includes two Individual laser detector, data processing unit, for right relative positioned at engine combustion flow field opposite side, and laser beam splitter unit The data stored in data collecting system are processed, and obtain Combustion Flow Field speed, because the present embodiment is based on molecule absorption light Spectrum, the laser attenuation fluctuating signal that Gas Components change in concentration is caused realizes cross-correlation as the random signal of cross-correlation analysis Test the speed so that the engine burn flow field velocity measuring device based on molecular absorption spectrum and method of the present embodiment offer is only Two beams are needed to determine that the laser of wavelength obtains related data by passing through Combustion Flow Field to be measured, to related data Reason, is obtained Combustion Flow Field speed, the shortcomings of overcoming the easy interference flowing field of contact type measurement method, affect burning, with structure letter The high advantage of single, contactless, sensitivity.

The invention is not restricted to the scope of specific embodiment, for those skilled in the art, as long as respectively Kind of change described claim limit and the spirit and scope of the present invention that determine in, these changes be it will be apparent that All are using the innovation and creation of present inventive concept in the row of protection.

Claims (4)

1. a kind of engine burn flow field velocity measuring device based on molecular absorption spectrum, for measuring engine combustion flow field In flow field velocity, it is characterised in that include：

Laser setup unit, for setting the operation wavelength and intensity of laser instrument；

Laser beam splitter unit, positioned at engine combustion flow field side, including the laser for exporting the laser setup unit It is divided into the laser beam splitter of two beams, the two-beam that the laser beam splitter is separated is with perpendicular to flow field direction and axially flat along flow field The mode of row arrangement is exported；

Measuring unit, it is relative positioned at engine combustion flow field opposite side, and the laser beam splitter unit, including two receptions Transmitted light laser detector of the two beam laser of the laser beam splitter unit output Jing after Combustion Flow Field to be measured；And

Data processing unit, is processed the signal of the probe unit, obtains Combustion Flow Field speed,

Wherein, the operation wavelength is the absorption line of the Gas Components molecule of selected fixation.

2. the engine burn flow field velocity measuring device based on molecular absorption spectrum according to claim 1, its feature It is also to include：

Data collecting system, the laser intensity signal and the data processing unit for the record preservation measuring unit Result.

3. the engine burn flow field velocity measuring device based on molecular absorption spectrum according to claim 1, its feature It is：

Wherein, the laser setup unit and the laser beam splitter unit are connected by optical fiber.

4. a kind of engine burn flow field speed measurement method based on molecular absorption spectrum, it is characterised in that including following step Suddenly：

Step 1, laser setup unit is arrived the Gas Components molecular absorption line of selected fixation by the modulation of laser works wavelength；

Step 2, laser beam splitter unit is divided into the laser that the laser setup unit is exported in space two beams parallel to each other, and The incident engine combustion flow field to be measured of the two beams laser vertical, transmitted light are received by the laser acquisition unit on opposite；

Step 3, data processing unit is processed the signal of the probe unit, using two laser transmission signals as mutual Random signal x (t) and y (t) of analysis are closed, carries out the cross-correlation function analysis of two signals：

$R_{xy}\left(\mathrm{\τ}\right)=\underset{T\→\mathrm{\∞}}{\lim }\frac{1}{T}{\∫}_0^{T}x\left(t\right)x(t+\mathrm{\τ})dt$

And try to achieve signal transit time τ₀, and according to computational methods V of Combustion Flow Field speed_avg=d/ τ₀, obtain Combustion Flow Field speed Degree,

Wherein, T is the integral mean time, and τ is time variable, and d is the distance between two beam laser.