CN102426094B - Measuring system for cooling performance of gas nozzle - Google Patents
Measuring system for cooling performance of gas nozzle Download PDFInfo
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- CN102426094B CN102426094B CN 201110255198 CN201110255198A CN102426094B CN 102426094 B CN102426094 B CN 102426094B CN 201110255198 CN201110255198 CN 201110255198 CN 201110255198 A CN201110255198 A CN 201110255198A CN 102426094 B CN102426094 B CN 102426094B
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Abstract
The invention belongs to the technical field of heat treatment of cold-rolled metal sheets, in particular to a measuring system for cooling performance of a gas nozzle in a heat treatment process. The measuring system for the cooling performance of the gas nozzle is characterized by consisting of an air supply system, a gas nozzle, an electric heating system and a measuring system, wherein the air supply system comprises a fan, a first butterfly valve, a flow pore plate and an air bellow; an air outlet end of the air bellow is provided with a gas nozzle block; the electric heating system consists of a transformer, a thyristor pressure regulator, a copper bar cable and an electric heating flat plate; the electric heating flat plate is positioned between the gas nozzle block and an open end of a measuring black box of the measuring system; the measuring system consists of the measuring black box and a thermal infrared imager; one end of the measuring black box is the open end and faces the electric heating flat plate of the electric heating system, and the other end of the measuring black box is provided with a thermal imager observation hole; and the thermal infrared imager is arranged outside the thermal imager observation hole. The system can be used for off-line measurement of the cooling performance of the gas nozzle in various modes, and is easy and convenient to operate and good in safety.
Description
Technical field
The invention belongs to strip heat treatment technics field, cold rolled metal, relate in particular to the measuring system of the gas nozzle cooling performance in the Technology for Heating Processing.
Background technology
Along with the demand of each industry to high quality of products constantly increases, the sheet metal process of thermal treatment is required more and more stricter, in heat treatment process, in order to obtain the metal plate and belt product of certain mechanical property and excellent surface characteristic, sheet metal need be heated to more than the critical temperature, then with the gas cooling means of jetting, and strict control cooldown rate is in the scope of technology permission.Therefore, in order to develop the cooling device that adapts to this meticulous Technology for Heating Processing, need test and check the jet performance of cooling device of gas, guarantee to adapt to the needs of Technology for Heating Processing.But because thermal treatment is often carried out in special atmosphere (as pure nitrogen gas, nitrogen and hydrogen mixed gas, pure hydrogen, nitrogen and ammonia gas mixture etc.), these gases are very dangerous or can't install direct measurement by experiment, therefore need to substitute with the air of safety, and with the data of the air that measures, be converted into real work atmosphere state in the engineering prototype.
Summary of the invention
Technical matters to be solved by this invention is: a kind of measuring system of gas nozzle cooling performance is provided, and this system can carry out off-line measurement to the gas nozzle cooling performance, and easy and simple to handle, and security is good.
The present invention solves the technical scheme that its technical matters adopts: the measuring system of gas nozzle cooling performance is characterized in that it is made up of air feed system, gas nozzle, electric heating system and measuring system; Air feed system comprises blower fan, first butterfly valve, flow-through orifice, bellows; The air intake of bellows is connected with the delivery outlet of blower fan by first airduct, and first airduct is provided with first butterfly valve and flow-through orifice; The outlet air end of bellows is provided with the gas nozzle group;
Electric heating system is made up of transformer, silicon-controlled voltage regulation device, copper bar cable and Electrothermal plate; The input end of transformer links to each other with the AC power of 380V, and the output terminal of transformer is provided with the silicon-controlled voltage regulation device, and the output terminal of silicon-controlled voltage regulation device is linked to each other with Electrothermal plate by the copper bar cable; Electrothermal plate is between the openend of the measurement black box of gas nozzle group and measuring system;
Measuring system is formed by measuring black box and thermal infrared imager; An end of measuring black box is openend and towards the Electrothermal plate of electric heating system, and the other end of measuring black box is provided with the thermal imaging system observation port, and the thermal imaging system observation port outside is provided with thermal infrared imager.
In the described bellows homogenizing plate is installed, homogenizing plate is between the air intake and outlet air end of bellows, and homogenizing plate is porous plate or flase floor, can make the air that feeds gas nozzle flow more even.
When the gas nozzle of described gas nozzle group was the narrow slit nozzle, the gas nozzle quantity of gas nozzle group was no less than 3; If the gas nozzle of gas nozzle group is the round mouth nozzle, the gas nozzle quantity of gas nozzle group is no less than 7.
Described thermal imaging system observation port is 1-4.
First airduct between the delivery outlet of first butterfly valve and blower fan is connected second airduct, second airduct with diffuse device and be connected, second airduct is provided with second butterfly valve.
Compared with prior art, the present invention has following main beneficial effect: 1. this system can carry out off-line measurement to the gas nozzle cooling performance that adopts in the metal plate material heat treatment unit before the engineering construction debugging; Because directly not testing under the special atmosphere (as pure nitrogen gas, nitrogen and hydrogen mixed gas, pure hydrogen, nitrogen and ammonia gas mixture etc.) that the engineering prototype adopts, easy and simple to handle, security is good.2. before the equipment commencement of commercial operation, by this system, whether the parameter designing that can test (measurement) gas nozzle satisfies the process for cooling demand, reduces engineering design and risks of construction; 3. gaging nozzle cooling characteristics curve can be used for the mathematical model parameter calculating of second control system, is conducive to first class control system with the rotation speed of fan control fan operation of optimum, the economy of raising equipment operation; 4. be used for the more high performance gas cooled nozzle of exploitation, and carry out reliable experiment test.
Description of drawings
Fig. 1 is the measuring principle of measurement system figure of gas nozzle cooling performance.
Fig. 2 is the facility installation drawings of many thermal imaging systems when measuring simultaneously.
Facility installation drawing when Fig. 3 is the measurement of separate unit thermal imaging system.
Fig. 4 is direct electrically heated wiring schematic diagram.
Fig. 5 is tinsel/electrically heated wiring schematic diagram of paper tinsel Wound-rotor type.
Among the figure: 1-blower fan exhaust box; The 2-blower fan; 3-first butterfly valve (Hand-operated butterfly valve); The 4-flow-through orifice; The 5-bellows; The 6-homogenizing plate; The 7-gas nozzle; 8-measures black box; 9-thermal imaging system observation port; The 10-thermal infrared imager; The 11-AC power; The 12-transformer; 13-silicon-controlled voltage regulation device; 14-copper bar cable; The 15-Electrothermal plate; 16-diffuses device; The 17-electrode; 18-observation port blind plate; 19-mark fine wire; The snakelike metal forming of 20-/silk; 21-second butterfly valve.
Embodiment
As shown in Figure 1, the measuring system of gas nozzle cooling performance, it is made up of air feed system, gas nozzle, electric heating system and measuring system; Air feed system comprises blower fan 2, first butterfly valve 3, flow-through orifice 4, bellows 5; The air intake of bellows 5 is connected by the delivery outlet of first airduct with blower fan 2, and first airduct is provided with first butterfly valve 3 and flow-through orifice 4; The outlet air end of bellows 5 (air-out end face) is provided with the gas nozzle group, and first airduct between the delivery outlet of first butterfly valve 3 and blower fan 2 is connected second airduct, second airduct with diffuse device 16 and be connected, second airduct is provided with second butterfly valve 21;
Electric heating system is made up of transformer 12, silicon-controlled voltage regulation device 13, copper bar cable 14 and Electrothermal plate 15; The input end of transformer links to each other with the AC power of 380V 11, and the output terminal of transformer is provided with silicon-controlled voltage regulation device 13, and the output terminal of silicon-controlled voltage regulation device 13 is linked to each other with Electrothermal plate 15 by copper bar cable 14; Electrothermal plate 15 is between the openend of the measurement black box of gas nozzle group and measuring system;
Measuring system is formed by measuring black box and thermal infrared imager 10; An end of measuring black box is openend and towards the Electrothermal plate 15 of electric heating system, and the other end of measuring black box is provided with thermal imaging system observation port 9, and thermal imaging system observation port 9 outsides are provided with thermal infrared imager 10.
In the described bellows 5 homogenizing plate 6 is installed, homogenizing plate 6 is between the air intake and outlet air end of bellows 5, and homogenizing plate 6 is porous plate or flase floor, can make the air that feeds gas nozzle 7 flow more even.
When the gas nozzle of described gas nozzle group was the narrow slit nozzle, the gas nozzle quantity of gas nozzle group was no less than 3 (generally adopting 3-20); If the gas nozzle of gas nozzle group is the round mouth nozzle, the gas nozzle quantity of gas nozzle group is no less than 7 (generally adopting 7-30).
Described thermal imaging system observation port 9 is 1-4 (concrete number is determined as required).
Because surge takes place easily when underload blower fan 2, therefore when starting blower fan and low discharge when 10～20% blower fan rated flows (flow≤) need open second butterfly valve 21 of bypass; When compressor flow increases to its rated flow (rated flow of blower fan, should be gas nozzle under maximum experiment flow velocity, the gas pipeline total flow 110～150%) (or the P-V curve that provides with reference to blower fan producer of back more than 1/3rd, determine that the flow value of surge can not take place blower fan), close second butterfly valve 21 of bypass.
The present invention is cardinal rule with the heat balance method of, and air is blasted gas nozzle to be measured, and electrically heated flat board is cooled off.Treat that plate temperature is stable, after namely system reaches thermal equilibrium, measure heating current and voltage, as the cooling power of gas nozzle this moment, and by thermal conduction study Nu/Re
nPrinciple of similarity is scaled the cooling power of nozzle when other gas cooling mediums or operating mode.
The measuring method of gas nozzle cooling performance provided by the invention, specifically: be heat eliminating medium with the air at room temperature, by one group of nozzle Electrothermal plate is carried out heat of cooling balance test, electrical heating power when recording the planar surface medial temperature and reaching certain stationary value, with this power as the cooling power of nozzle under this state, and use the Martin theory of comparatively generally acknowledging in the gas jet heat transfer problem as the basic similarity criterion between different operating modes, be converted into the cooling power of nozzle under the operating mode in the practical engineering application.
The present invention based on the Martin theory think, at the round nozzle array of vertical fluid:
2000≤Re≤100,000，
0.004≤f≤0.04
2≤H/D≤12
In the formula, Nu is the dull and stereotyped average nusselt number of going up gas, and Pr is the Prandtl number of gas, and Re represents Reynolds number,
A heat compensator conducting property number representing this nozzle array, f are nozzle array coefficient (being the aperture area of nozzle and the ratio of the nozzle array total area).
If the spray box form of circular hole is directly opened in the exit, need revise w with cross-sectional constriction coefficient ε, D, f:
In the formula, the nozzle place gas velocity after w ' expression is shunk, the nozzle diameter after D ' expression is shunk, the nozzle array coefficient after f ' expression is shunk.
For the parallel slits array:
f
0(H/S)＝[60+4(H/S-2)
2]
-1/2
1500≤Re≤40,000，
0.008≤f≤2.5f
0(H/S)
1≤H/D≤40
In the formula, f
0The array features coefficient of expression narrow slit nozzle
In the calculating formula of two kinds of nozzles, reynolds number Re=wS/ ν, Prandtl number Pr=ν/α
Wherein H is that nozzle is to the vertical range (m) of solid surface, D is circular jet nozzle diameter (m), B is gap nozzle width (m), S is flow performance size (circular jet nozzle S=D, gap nozzle S=2B), w is jet velocity (m/s), and ν is kinematics viscosity (m2/s), α is the thermal diffusivity (m2/s) of gas, and f is nozzle array coefficient (being the aperture area of nozzle and the ratio of the nozzle array total area).
Following relation is arranged between the convective heat-transfer coefficient h between nusselt number Nu and gas and flat board:
In the formula, h is convective heat-transfer coefficient, and S represents the flow performance size.
If be labeled as 1 under every physical parameter of air when carrying out this experiment, the gas that uses in the engineering prototype is 2, then for same nozzle sets, has following similarity relation:
Cooling power
Wherein define Δ T=T
Dull and stereotyped-T
Gas
By recording the Q1 (being the pressure cooling power of the nozzle of bubbling air) under the air at room temperature medium, can be according to above-mentioned formula, according to rerum natura and the actual temperature difference T of employed gas in the engineering
2, obtain the cooling power Q of gas in the engineering prototype
2
Below in conjunction with embodiment and accompanying drawing, the invention will be further described.
Method provided by the invention is by gas nozzle and by thermally equilibrated between the Electrothermal plate of its cooling, measure the nozzle cooling power under this state, then by the reduction formula of nozzle under gas with various medium and duty, obtain under actual engineering operation state the cooling power of this nozzle.
Desired temperature in this experiment, is taken all factors into consideration the back and is determined according to the temperature range of the thermometal flat board that is cooled in the engineering prototype, the temperature resistant capability of flat board 15 and the optimum measurement temperature range of thermal infrared imager 10 by the laboratory technician.Can only get the intermediate value in above-mentioned three's common factor interval, carry out one group of experiment; Improve the reliability of experimental measurements as needs, can be in above-mentioned three temperature ranges be occured simultaneously, get a temperature set-point every about 20 ℃～30 ℃, carry out many group experiments repeatedly, will organize experimental result more then and carry out curvilinear regression.The setting value of flow in the experiment should guarantee under this flow, the Re basically identical during nozzle operation in the reynolds number Re at nozzle place and the engineering prototype (deviation range be no more than Re's in the engineering prototype ± 20%).
The measuring method of gas nozzle cooling performance, it comprises the steps:
The first step, the preparation of the measuring system of gas nozzle cooling performance: the measuring system of gas nozzle cooling performance is made up of air feed system, gas nozzle, electric heating system and measuring system; Air feed system comprises blower fan exhaust box 1, blower fan 2, first butterfly valve 3, flow-through orifice 4, bellows 5; The air intake of bellows 5 is connected by the delivery outlet of first airduct with blower fan 2, and first airduct is provided with first butterfly valve 3 and flow-through orifice 4; The outlet air end of bellows 5 is provided with the gas nozzle group, and homogenizing plate 6 is installed in the bellows 5, and homogenizing plate 6 is between the air intake and outlet air end of bellows 5, and homogenizing plate 6 is porous plate or flase floor, can make the air that feeds gas nozzle 7 flow more even; First airduct between the delivery outlet of first butterfly valve 3 and blower fan 2 is connected one second airduct, second airduct with diffuse device 16 and be connected [namely air feed system also have a bypass to enter by second butterfly valve 21 diffuse device 16 and diffuse (gas diffuse mouthful)] in addition, second airduct is provided with second butterfly valve 21.
When the gas nozzle 7 of described gas nozzle group was the narrow slit nozzle, the gas nozzle quantity of gas nozzle group was no less than 3; If the gas nozzle 7 of gas nozzle group is the round mouth nozzle, the gas nozzle quantity of gas nozzle group is no less than 7.
Electric heating system is made up of AC power 11, transformer (reducing transformer) 12, silicon-controlled voltage regulation device 13, copper bar cable 14 and Electrothermal plate (heating panel) 15; The input end of transformer links to each other with the AC power of 380V 11, and the output terminal of transformer is provided with silicon-controlled voltage regulation device 13, and the output terminal of silicon-controlled voltage regulation device 13 is linked to each other with Electrothermal plate 15 by copper bar cable 14; Electrothermal plate 15 is between the openend of the measurement black box of gas nozzle group and measuring system.
Measuring system is formed by measuring black box and thermal infrared imager 10; An end of measuring black box is openend and towards Electrothermal plate, and the other end of measuring black box is provided with thermal imaging system observation port 9, and thermal imaging system observation port 9 outsides are provided with thermal infrared imager 10.Described thermal imaging system observation port 9 is 1-4.
In second step, the blank assay of nozzle cooling is opened AC power 11, starts silicon-controlled voltage regulation device 13, and voltage is progressively heightened, and the heating circuit that electric current constitutes by copper bar cable 14 and Electrothermal plate 15 is with Electrothermal plate 15 heating; Timing should be incremental on the voltage, goes up 10% (the avoiding the voltage toning, with the protection experimental facilities) that AM depth is no more than current magnitude of voltage at every turn, and be stabilized at least 40 seconds time of this heating power; If the thickness of the Electrothermal plate 15 (big (area 〉=150000～200000mm of thickness 〉=3～5mm) and area
2), its thermal capacitance and thermal inertia are also bigger, answer the time of proper extension temperature stabilization, guarantee the surface temperature of the Electrothermal plate 15 that observes by thermal infrared imager 10, and fluctuating range is kept and is this time tested below 3% of setting value in 30 seconds; The gauger changes by the surface temperature of thermal infrared imager 10 observation Electrothermal plates 15, reaches the experiment setting value up to the plate face medial temperature of its Electrothermal plate 15; In order to improve the measuring accuracy of temperature, the experiment setting value of the plate face medial temperature of Electrothermal plate 15 should be higher than air and environment temperature more than 30 ℃ at least, and experiment setting value higher limit is determined by material heatproof degree and the thermal infrared imager range of Electrothermal plate 15; After Electrothermal plate 15 is stabilized in desired temperature, measure electric current and the magnitude of voltage of whole heating circuit; Wherein magnitude of voltage can record by the voltage table that silicon-controlled voltage regulation device 13 carries, and current value can use the pincerlike meter galvanometer to record; Duplicate measurements current/voltage value surpasses 3 times, and 2 minor ticks are no less than 5min, with each current value I
0With magnitude of voltage V
0Note the average value P of its product
0System radiating amount when (being average heating power) forces cooling as no nozzle.
The 3rd step, close electric heating system earlier, start air feed system; Before the measuring system of gas nozzle cooling performance is used, need at first start air feed system, and gather the data on flows of bellows 5; Because surge takes place easily when underload blower fan 2, therefore when starting blower fan and low discharge when 10～20% blower fan rated flows (flow≤) need open second butterfly valve 21 of bypass; When compressor flow increases to its rated flow (rated flow of blower fan, should be nozzle under maximum experiment flow velocity, the gas pipeline total flow 110～150%) (or the P-V curve that provides with reference to producer of back more than 1/3rd, determine that the flow value of surge can not take place blower fan), close second butterfly valve 21 of bypass, strengthen the aperture of the butterfly valve 3 on the major loop gradually, the gas flow that records until flow-through orifice 4 reaches the gas flow (setting value of air mass flow in the experiment that experiment is set, should guarantee under this flow, the Re deviation of the jet hole in the reynolds number Re at jet hole place and the engineering prototype is no more than ± and 20%).
In the experiments of measuring, air is at the flow velocity w at nozzle place
1Gas flow/cross-section area of nozzle that=flow-through orifice 4 records; This flow velocity need guarantee its Re when setting
1=w
1S
1/ ν
1Scope in the scope of application of Martin theory, namely for narrow slit nozzle Re
11500～40000, for round mouth nozzle Re
1Be 2000～100000, Re
1Air is at the Reynolds number at nozzle place, S
1The flow performance size of expression nozzle.In order to guarantee the measuring accuracy of flow-through orifice 4, nozzle place gas velocity should not be lower than 10m/s simultaneously.Narrow slit nozzle sets, its nozzle quantity are no less than 3; If round mouth nozzle, its quantity are no less than 7.
The 4th step, Electrothermal plate heating: repeat the step in second step, start electric heating system, but measured temperature should surpass 5min stabilization time.The heating power that record this moment is designated as P
1(with each current value I
1With magnitude of voltage V
1Note, the mean value of its product is P
1).
In the 5th step, the measurement of air cooling power: deduction falls this heat dissipation capacity under this Electrothermal plate temperature of measuring system of gas nozzle cooling performance, is the pressure cooling power of the nozzle of bubbling air, is designated as Q
1=P
1-P
0
In the 6th step, the conversion of nozzle cooling power: the nozzle cooling power under the engineering actual motion state is designated as Q
2, then
W wherein
1Be the flow velocity (by flow/nozzle exit long-pending calculate) of air in the measuring system at the nozzle place, ν
1Be the kinematic viscosity of air, Δ T
1Be the temperature difference of Electrothermal plate and nozzle place air, k
1Be the coefficient of heat conductivity (the gas rerum natura table that can look into heat transfer handbook obtain) of air under experimental temperature, Pr
1Prandtl number (the gas rerum natura table that can look into the heat transfer handbook obtains) for air; w
2Be the flow velocity (gas that uses in the engineering prototype is generally pure nitrogen gas, nitrogen and hydrogen mixed gas, pure hydrogen, or nitrogen and ammonia gas mixture etc.) of gas in the engineering prototype, ν
2Be the kinematic viscosity of gas medium in the engineering prototype, Δ T
2Be the temperature difference of the Electrothermal plate that is cooled surface with nozzle place gas, k
2Be the coefficient of heat conductivity of gas in the engineering prototype, Pr
2Prandtl number for gas medium in the engineering prototype.
When consulting the heat transfer handbook, the qualitative temperature of gas is generally the mean value of nozzle exit temperature and heated plate surface temperature.What pay special attention to is, if the mixed gas in the engineering prototype can chemical reaction take place or phase transformation is arranged in its working temperature interval, then can not adopt method of the present invention to measure.
The installation method of the measuring system of brief description gas nozzle cooling performance.
Because the field range of thermal infrared imager (thermal imaging system) 10 is limited, (the area that can measure when tested Electrothermal plate area is big, field range by the thermal imaging system camera lens determines), the temperature survey that thermal imaging system possibly can't cover whole Electrothermal plate zone.For this reason, can take two kinds of solutions.When many thermal imaging systems, take the mode as Fig. 2, drive a plurality of thermal imaging system observation ports (observation port) 9 (being no more than 4 usually) at measurement black box 8, set up many thermal imaging systems 10 and measure simultaneously, pass the thermal imaging photo of all thermal imaging systems 10 back computer then, splice in real time.When a thermal imaging system 10 is only arranged, can take the mode as Fig. 3, drive a plurality of observation ports 9 (being no more than 4 usually), when measuring, with the temporary transient no observation port of observation port blind plate 18 sealings, to avoid space outerpace thermal imaging is impacted earlier at every turn.Under same stable measurement state, measure with same thermal imaging system gradation then, more each thermal imaging photo is spliced.Convenience for stitching image, need make marks at Electrothermal plate or thermal imaging photo, but common mark can't obtain projection on the infrared thermal imaging photo, therefore black box 8 inside can measured, press close to Electrothermal plate 15 places, along laterally with vertically pull on several marks with fine wire 19 (generally selecting the finer wire of diameter below 1mm for use), because the tinsel temperature is lower than Electrothermal plate temperature, can form one elongated dark-coloured lines at infrared photograph, as the mark line of infrared thermal imaging photomosaic.
The direct type of heating of Electrothermal plate has two kinds, and a kind of is dull and stereotyped own as the conductor heating power, and another kind is that the conductor heating power is installed in Electrothermal plate.Mode as shown in Figure 4, be with Electrothermal plate 15 itself as conductor, be clamped between the electrode 17, directly the mode of heating power.Electrothermal plate is selected the bigger metal material of resistance, and not optional aluminium, the metal that copper constant resistance rate is little are in order to avoid the voltage heating power concentrates on the outer lead copper bar 14.The planar surface ceiling temperature of this kind type of heating is higher, for example adopt the heat-resistance stainless steel plate, maximum surface temperature can reach 500～600 ℃ (in air), but because the problems such as structural homogenity of material inside, the temperature homogeneity on Electrothermal plate surface is relatively poor, surface temperature difference can surpass 10 ℃, and serious may reach 50 ℃.When if the Electrothermal plate maximum surface temperature is lower than 250 ℃, can select the type of heating as Fig. 5, select high temperature insulation organic material (as high-temperature silica gel) as plate material, dull and stereotyped inner with aluminium or copper metal forming/silk, cover dull and stereotyped entire area in snakelike coiling mode.The temperature homogeneity of this mode is good, generally can guarantee Electrothermal plate temperature deviation everywhere in 5 ℃, and electrical heating power reaches as high as 4W/cm
2
Application example 1:
If adopt 50 ℃ pure nitrogen gas in the prototype engineering, the gas velocity w of nozzle place
2=30m/s, the metal sheet surface temperature is 160-240 ℃, when the air themperature when carrying out this experiment test is 20 ℃:
Step 1: because plate temperature is lower than 250 ℃, should select the Electric heating as Fig. 5 for use;
Step 2: if only carry out one group of experiment, preferred 200 ℃ of the design temperature of Electrothermal plate 15; If carry out many group experiments, can select design temperature 160 ℃, 180 ℃, 200 ℃, 220 ℃, the 240 ℃ tests that experimentize respectively.
Step 3: only to carry out one group of experiment, dull and stereotyped 15 desired temperature is got 200 ℃ and is example.ΔT
1＝200℃-20℃＝180℃。The physical property qualitative temperature of air is (20 ℃+200 ℃) ÷ 2=110 ℃, looks into the ν that the heat transfer handbook gets air
1=37.90 * 10
-6m
2/ s, Pr
1=0.68, k
1=0.04038W/m. ℃.In the engineering prototype, the qualitative temperature of nitrogen is (50 ℃+200 ℃) ÷ 2=125 ℃, looks into the heat transfer handbook, the ν of nitrogen
2=37.66 * 10
-6m
2/ s, Pr
2=0.684, k
2=0.03984W/m. ℃, the gas velocity setting value when then nozzle is tested is got w
1=w
2* ν
1/ ν
2=30.19m/s.
Step 4: at first carry out blank assay, when supposing not start air feed system, the thermoelectric (al) power that adds when flat board reaches thermal equilibrium is 5kW.
Step 5: carry out the test of cooling performance then.During practical operation, can't accomplish accurately to mate with temperature and speed setting value, general is the benchmark of system stability with the desired temperature, supposes the velocity amplitude w of actual measurement this moment
1Be 32m/s, adding thermoelectric (al) power is 50kW.
Step 6: the power conversion of typical condition.
In the engineering prototype, the cooling power Q of nozzle under the actual condition
2For
In the engineering prototype, the sheet metal temperature in the time of 200 ℃, Δ T2=200 ℃-50 ℃=150 ℃
Then the cooling power (unit kW) of this group nozzle under this operating mode is
Q
2＝(50kW-5kW)×[30m/s×37.90×10-6m
2/s÷32m/s÷(37.66×10-6m
2/s)]
(2/3)×(150℃÷180℃)×(0.03984W/m.℃÷0.04038W/m.℃)×(0.684÷0.68)＝35.80kW
Step 7: the nozzle cooling power of other operating modes converts.
In 160-240 ℃ of temperature range, when the cooling power during to other plate temperature values converts, (general ultimate value and reference temperature value differ in 50 ℃ because this temperature range span is little, can be considered and change not quite, but except when gas undergoes phase transition), the thermophysical property of nitrogen changes very little, can be similar to plate temperature nitrogen physical-property parameter replacement qualitatively in the time of 200 ℃.
For example for plate temperature 220 ℃ the time, Δ T2 '=220 ℃-50 ℃=170 ℃, the cooling power Q of nozzle
2' be:
Q
2’＝(50kW-5kW)×[30m/s×37.90×10-6m
2/s÷32m/s÷(37.66×10-6m
2/s)]
(2/3)×(170℃÷180℃)×(0.03984W/m.℃÷0.04038W/m.℃)×(0.684÷0.68)＝40.57kW
Nozzle cooling power during other temperature values can be calculated with reference to this example.
Application example 2:
If the gas that adopts in the engineering prototype, be nitrogen and hydrogen mixed gas (volume ratio of nitrogen and hydrogen is 9: 1), test setting, test and conversion step so substantially with example 1, but the actuating medium of this moment is mixed gas, therefore when step 3, determine the qualitative temperature of mixed gas and the thermal physical property parameter under this temperature.Use kinetic viscosity μ this moment
2Calculate the kinematic viscosity ν of mixed gas
2
Suppose that other operating modes are identical with example 1, namely mixing qualitative temperature is 125 ℃.
Consulting the heat transfer handbook obtains:
Nitrogen μ=25.70 * 10
-6Kg/m.s, Pr=0.684, k=0.03984W/m. ℃, ρ=0.6824kg/m
3
Hydrogen μ=12.636 * 10
-6Kg/m.s, Pr=0.675, k=0.272W/m. ℃, ρ=0.04918kg/m
3
Then the thermophysical property parameter of mixed gas is as follows:
ρ
2＝0.1m
3×0.04918kg/m
3+0.9m
3×0.6824kg/m
3＝0.6191kg/m
3
The mass percent of nitrogen is 0.9m
3* 0.6824kg/m
3÷ (1m
3* 0.6191kg/m
3) * 100=99.206%
The mass percent of hydrogen is 0.1m
3* 0.04918kg/m
3÷ (1m
3* 0.6191kg/m
3) * 100=0.794%
The kinetic viscosity μ of mixed gas
2=(25.70 * 10
-6Kg/m.s * 99.206%+12.636 * 10
-6Kg/m.s * 0.794%) ÷ 100=25.60 * 10
-6Kg/m.s
The kinematic viscosity ν of mixed gas
2=μ
2/ ρ
2=25.60 * 10
-6Kg/m.s ÷ 0.6191kg/m
3=41.34m
2/ s
Heat-conduction coefficient k
2÷ 100=0.0417W/m. ℃ of=(0.03984W/m. ℃ * 99.206%+0.272W/m. ℃ * 0.794%)
Then carry out measurement operation and the calculating of the step 4-7 in the example 1.
If nozzle uses the cooling power test and conversion of other mixed gass (for example nitrogen and ammonia, hydrogen and ammonia), carry out with reference to the method for example 2.
Claims (6)
1. the measuring system of gas nozzle cooling performance is characterized in that it is made up of air feed system, gas nozzle group, electric heating system and measuring system; Air feed system comprises blower fan (2), first butterfly valve (3), flow-through orifice (4), bellows (5); The air intake of bellows (5) is connected by the delivery outlet of first airduct with blower fan (2), and first airduct is provided with first butterfly valve (3) and flow-through orifice (4); The outlet air end of bellows (5) is provided with the gas nozzle group;
Electric heating system is made up of transformer (12), silicon-controlled voltage regulation device (13), copper bar cable (14) and Electrothermal plate (15); The input end of transformer links to each other with the AC power of 380V (11), and the output terminal of transformer is provided with silicon-controlled voltage regulation device (13), and the output terminal of silicon-controlled voltage regulation device (13) is linked to each other with Electrothermal plate (15) by copper bar cable (14); Electrothermal plate (15) is between the openend of the measurement black box of gas nozzle group and measuring system;
Measuring system is formed by measuring black box and thermal infrared imager (10); An end of measuring black box is openend and towards the Electrothermal plate (15) of electric heating system, and the other end of measuring black box is provided with thermal imaging system observation port (9), and thermal imaging system observation port (9) outside is provided with thermal infrared imager (10).
2. the measuring system of gas nozzle cooling performance according to claim 1, it is characterized in that: homogenizing plate (6) is installed in the described bellows (5), homogenizing plate (6) is positioned between the air intake and outlet air end of bellows (5), and homogenizing plate (6) is porous plate or flase floor.
3. the measuring system of gas nozzle cooling performance according to claim 1, it is characterized in that: when the gas nozzle of described gas nozzle group was the narrow slit nozzle, the gas nozzle quantity of gas nozzle group was no less than 3.
4. the measuring system of gas nozzle cooling performance according to claim 1, it is characterized in that: the gas nozzle of gas nozzle group is the round mouth nozzle, the gas nozzle quantity of gas nozzle group is no less than 7.
5. the measuring system of gas nozzle cooling performance according to claim 1 is characterized in that: described thermal imaging system observation port (9) is 1-4.
6. the measuring system of gas nozzle cooling performance according to claim 1, it is characterized in that: first airduct between the delivery outlet of first butterfly valve (3) and blower fan (2) is connected second airduct, second airduct with diffuse device (16) and be connected, second airduct is provided with second butterfly valve (21).
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| CN102359871B (en) * | 2011-08-31 | 2013-09-18 | 中冶南方(武汉)威仕工业炉有限公司 | Measuring method of cooling performance of air nozzle |
| CN109902363B (en) | 2019-02-11 | 2020-12-11 | 大连理工大学 | Parameter design and numerical simulation method of jet trencher nozzle |
| CN110907731B (en) * | 2019-12-03 | 2022-08-12 | 国网陕西省电力公司电力科学研究院 | Transformer substation thermal state evaluation method and system based on temperature sensing |
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