CN112196696A - Modification method for improving acoustic energy dissipation of partition plate nozzle - Google Patents

Modification method for improving acoustic energy dissipation of partition plate nozzle Download PDF

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CN112196696A
CN112196696A CN202011014304.5A CN202011014304A CN112196696A CN 112196696 A CN112196696 A CN 112196696A CN 202011014304 A CN202011014304 A CN 202011014304A CN 112196696 A CN112196696 A CN 112196696A
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acoustic energy
energy dissipation
acoustic
dissipation
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CN112196696B (en
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杨立军
李敬轩
朱烁烁
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Beihang University
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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02K—JET-PROPULSION PLANTS
    • F02K9/00—Rocket-engine plants, i.e. plants carrying both fuel and oxidant therefor; Control thereof
    • F02K9/42—Rocket-engine plants, i.e. plants carrying both fuel and oxidant therefor; Control thereof using liquid or gaseous propellants
    • F02K9/44—Feeding propellants
    • F02K9/52—Injectors
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02K—JET-PROPULSION PLANTS
    • F02K9/00—Rocket-engine plants, i.e. plants carrying both fuel and oxidant therefor; Control thereof
    • F02K9/42—Rocket-engine plants, i.e. plants carrying both fuel and oxidant therefor; Control thereof using liquid or gaseous propellants
    • F02K9/60—Constructional parts; Details not otherwise provided for
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02K—JET-PROPULSION PLANTS
    • F02K9/00—Rocket-engine plants, i.e. plants carrying both fuel and oxidant therefor; Control thereof
    • F02K9/96—Rocket-engine plants, i.e. plants carrying both fuel and oxidant therefor; Control thereof characterised by specially adapted arrangements for testing or measuring

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  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Measuring Temperature Or Quantity Of Heat (AREA)

Abstract

The invention relates to a modification method for improving acoustic energy dissipation of a diaphragm nozzle, wherein the diaphragm nozzle can dissipate acoustic energy in a combustion chamber of a rocket engine due to thermal viscosity effect, so that unstable combustion is inhibited, and dissipation mainly occurs at the position where the distance between adjacent nozzles is smaller than a thermal viscosity boundary layer. By increasing the contact area of the outer surfaces of adjacent nozzles, the dissipation of acoustic energy by the diaphragm nozzles can be effectively improved. The invention provides a method for milling the relative partial cylindrical surfaces of adjacent nozzles by modifying the outer surfaces of the nozzles of the partition plates, thereby increasing the contact area. The effectiveness of the invention is proved through theoretical calculation, the invention is suitable for various rocket engine partition plate nozzles, and an effective means is provided for inhibiting the unstable combustion of the rocket engine.

Description

Modification method for improving acoustic energy dissipation of partition plate nozzle
Technical Field
The invention relates to a method for modifying a nozzle of a partition plate of a combustion chamber of a liquid rocket engine.
Background
In the working process of the liquid rocket engine, the problem of unstable combustion is easily caused in the combustion chamber. The unstable combustion refers to the pressure pulsation periodically and the pulsation amplitude exceeds 5% of the pressure in the combustion chamber, and the unstable combustion can be divided into low-frequency unstable, medium-frequency unstable and high-frequency unstable according to the frequency domain characteristics of the pressure pulsation.
Since the unstable combustion causes structural damage to the combustion chamber, it is necessary to suppress the unstable combustion. In the passive control method for suppressing the high frequency instability of the combustion chamber, the diaphragm nozzle is an effective method, and the mechanism is that the energy of the combustion response cannot maintain the energy required by the pressure oscillation through damping dissipation effect. According to research and experience of the liquid rocket engine, the radial partition plate is arranged on the injection surface, so that the tangential instability of high frequency can be effectively inhibited, and the radial instability of the high frequency can be effectively inhibited by arranging the hub partition plate.
At present, a clapboard nozzle for controlling unstable combustion is mainly cylindrical, and researches show that the acoustic energy dissipation can be changed by changing the contact surface of a channel, so that the thermal viscous dissipation effect is improved, and the effect of enhancing and inhibiting the unstable combustion of an engine is achieved.
Disclosure of Invention
Against the background, the invention provides a modification method for improving acoustic energy dissipation of a baffle nozzle, namely milling partial cylindrical surfaces opposite to adjacent nozzles, and increasing the contact area of a tiny gap area so as to improve the thermal viscosity dissipation effect. The invention provides the law of influence of various parameters on acoustic energy dissipation in the modification method through theoretical model calculation, and is helpful for guiding the design of the clapboard nozzle of the rocket engine adopting the modification method.
The technical scheme adopted by the invention is as follows:
a modification method for improving acoustic energy dissipation of a diaphragm nozzle is characterized in that for different milling degrees, as shown in figure 1, acoustic energy dissipation is changed to realize different sound absorption effects. Xi is the milling degree which represents the proportion of the milled part, the larger the value is, the more the milled part is, and the definition is:
Figure BDA0002698546090000021
where R is the radius of the cylinder and d is the length of the uncut portion of the cylinder.
Calculation of acoustic energy dissipation:
the diaphragm nozzle model is simplified into a rectangular slit pipe internal acoustic wave propagation model with an area gradient. A plane sound wave is transmitted in the tube with a rectangular slit with variable cross section, the height of the rectangular slit is 2a, the width of the rectangular slit is 2b, the cross section area of the rectangular slit is 2a multiplied by 2b, wherein a > b, and the tube has no average flow. Assuming that the pipe wall is rigid, the velocity of the medium particles near the pipe wall is 0, and the farther away from the pipe wall, the less the medium particles are constrained by the pipe wall, the higher the velocity, and then a velocity gradient is generated in the pipe, relative motion is generated between the media layers, and the medium particles are acted by viscous force. Similarly, assuming the wall is constant, there is a heat exchange effect between the medium particles and the medium particles are thus subjected to heat transfer.
According to the momentum equation of the N-S equation, because the viscous force mainly acts on the cross section direction, neglecting the action of the viscous force on the slit length direction, the following can be obtained:
Figure BDA0002698546090000031
wherein ρ is density, η is dynamic viscosity, u is velocity, y is slit width direction, i is imaginary unit, ω is acoustic frequency, p is pressure, x is slit length direction, subscript 0 parameter represents balance value, and parameters not labeled with 0 are all disturbance parameters.
Similarly, neglecting the effect of thermal conduction in the direction of the slit length x, the energy equation can be derived:
Figure BDA0002698546090000032
wherein κ is heat transfer coefficient, T is gas temperature, CpIs the specific heat at constant pressure.
The boundary conditions of the velocity and temperature on the cross section are that when y ═ b, u ═ 0, and T ═ 0, the velocity and temperature distributions on the cross section are determined, and then averaged over the cross section:
Figure BDA0002698546090000033
Figure BDA0002698546090000034
wherein the subscript a represents the average value of the disturbance parameter in the cross-section, F (delta)1)、F(δ2) Are respectively delta1、δ2Function of (c):
Figure BDA0002698546090000035
Figure BDA0002698546090000036
wherein, delta1、δ2Acoustic viscous dissipation boundary layer thickness and acoustic thermal conduction dissipation boundary layer thickness, respectively, defined as:
Figure BDA0002698546090000041
Figure BDA0002698546090000042
the expression of the half width b of the variable cross-section rectangular slit along the change of the length x direction is as follows:
Figure BDA0002698546090000043
parameter bmIs the minimum gap value between adjacent diaphragm nozzles.
According to an ideal gas state equation:
Figure BDA0002698546090000044
the continuity equation can be written as:
Figure BDA0002698546090000045
where t is the time variable and c is the speed of sound.
Substituting the calculated average speed and temperature of the cross section into a continuity equation to obtain a wave equation:
Figure BDA0002698546090000046
wherein γ is a specific heat ratio.
After the wave equation is obtained, the distribution of the sound wave pressure in the axial space position can be analyzed through numerical calculation, and the pressure disturbance is the sound wave A which is propagated downstream+And an acoustic wave A propagating upstream-I.e. p ═ a++A-And the velocity is disturbed ua＝kF(δ1)(A++A-)/ρ0ω, wave number of acoustic wave:
Figure BDA0002698546090000047
by solving the pressure disturbance and the speed disturbance, the acoustic wave amplitude A propagating downstream can be obtained+And the amplitude A of the acoustic wave propagating upstream-。
Defining a dissipation coefficient:
Figure BDA0002698546090000051
subscripts 1 and 2 represent the energy loss at the inlet and outlet, respectively, and the dissipation factor E represents the loss of acoustic energy due to hot tack, with higher values indicating higher losses.
Under the conditions of certain working frequency, gas temperature and environmental pressure of the rocket engine, different minimum gaps have different acoustic energy dissipation coefficients, and an optimal gap exists, so that the acoustic energy dissipation coefficient is maximum, as shown in fig. 2. FIG. 2 illustrates the change rule of the acoustic energy dissipation coefficient with different minimum clearances under the conditions of normal temperature and pressure, the working frequency of 1000Hz, the radius of the cylinder of 10mm and the cylindrical surface. And calculating the maximum dissipation under the optimal clearance when different milling degrees are obtained.
According to the invention, aiming at different partition plate nozzle cylinder radiuses, the maximum sound energy dissipation is firstly reduced and then increased along with the milling degree.
According to the invention, aiming at different working frequencies, the maximum acoustic energy dissipation is firstly reduced and then increased along with the milling degree.
According to the invention, aiming at different gas temperatures, the maximum sound energy dissipation is firstly reduced and then increased along with the milling degree.
The invention has the advantages and effects that: the baffle nozzle can effectively change the sound energy dissipation, and has the advantages of simple structure, convenient installation, low cost and easy processing.
Drawings
FIG. 1 is a schematic view of a milled bulkhead nozzle.
Fig. 2 shows the dissipation factor of the acoustic energy at different gaps.
Fig. 3 maximum acoustic energy dissipation factor as a function of milling level.
Fig. 4 shows the variation of the maximum acoustic energy dissipation factor with milling degree at different cylinder radii.
Fig. 5 shows the variation of the maximum acoustic energy dissipation factor with milling level for different operating frequencies.
FIG. 6 shows the variation of the maximum acoustic energy dissipation coefficient with milling degree for different combustion gas temperatures.
The symbols in the figure are as follows: radius of R cylinder, half width of slit between b partitions, bmMinimum gap of the partition plate, xi milling degree, E sound energy dissipation coefficient, f working frequency and T fuel gas temperature.
The specific implementation mode is as follows:
the present invention will now be described in detail with reference to the accompanying figures 1-6. In this embodiment, the acoustic energy dissipation is effectively changed by changing the milling degree of the cylindrical surface of the nozzle of the partition plate, and the specific implementation description is as follows:
in this embodiment, under normal temperature and pressure, the working frequency f is 1000Hz, the radius R of the cylinder of the nozzle of the partition board is 10mm, the milling degree variation range is 0-0.9, and the minimum gap b is selectedmThe variation range is 0-0.5 mm, and the variation rule of the maximum sound energy dissipation along with the milling degree is obtained by calculating a wave equation, as shown in the figure. FIG. 3 shows the change rule of the maximum acoustic energy dissipation along with the milling degree, wherein the working frequency is 1000Hz, the radius of the cylinder of the nozzle of the partition plate is 10mm, the change range of the minimum clearance is 0-0.5 mm. It can be seen that as the milling degree becomes larger, the maximum acoustic energy dissipation is reduced firstly and then becomes larger, and the turning point appears in xi of 0.26, which proves that the milling diaphragm nozzle can effectively change the acoustic energy dissipation.
Because the rocket engines of different models are different, conditions such as the cylinder radius, the working frequency, the gas temperature and the like of the clapboard nozzle are different, and in order to verify that the milled clapboard nozzle can effectively change the acoustic energy dissipation under various conditions, the acoustic energy dissipation under different conditions needs to be calculated.
Fig. 4 shows the rule that when the working frequency at normal temperature and normal pressure is 1000Hz, the radius of the cylinder is respectively 2.5mm, 5mm, 7.5mm, 10mm, 12.5mm and 15mm, the milling degree is changed, the change range is 0-0.9, and the maximum acoustic energy dissipation changes along with the milling degree. It can be seen that under different cylindrical radii, the maximum acoustic energy dissipation is increased with the degree of milling, and is decreased first and then increased, and the inflection points are respectively set at xi ═ 0.235, xi ═ 0.26, and xi ═ 0.26. Therefore, the milled diaphragm nozzle can effectively change the acoustic energy dissipation under the condition of different cylinder radiuses.
Fig. 5 shows the rule that when the radius of the cylinder is 10mm at normal temperature and normal pressure, and the working frequencies are 400Hz, 800Hz, 1000Hz, 1200Hz, 1600Hz and 2000Hz respectively, the milling degree is changed, the change range is 0-0.9, and the maximum acoustic energy dissipation changes along with the milling degree. It can be seen that under different operating frequency conditions, the maximum acoustic energy dissipation is increased along with the milling degree, and is decreased first and then increased, and the inflection point is ξ ═ 0.26. The acoustic energy dissipation of the milled diaphragm nozzle can be effectively changed under the conditions of different working frequencies.
Fig. 6 shows the change rule of the milling degree when the working frequency is 1000Hz when the radius of the normal-pressure cylinder is 10mm, and the gas temperature is 293K, 500K, 1000K, 1500K, 2000K, 2500K, respectively, the change range is 0-0.9, and the maximum acoustic energy dissipation is along with the change of the milling degree. It can be seen that under different gas temperature conditions, the maximum acoustic energy dissipation is increased with the increasing milling degree, and is decreased first and then increased, and the inflection points are respectively set to xi ═ 0.26, xi ═ 0.235, xi ═ 0.26, xi ═ 0.285, and xi ═ 0.285. Therefore, the milled diaphragm nozzle can effectively change the acoustic energy dissipation under different gas temperature conditions.
Correspondingly, according to the above results, the partition plate nozzle is composed of a series of partition plate nozzles extending to the combustion chamber, the partition plate nozzles are arranged in a certain arrangement mode, the cylindrical rows with partial cylindrical surfaces milled are formed, and a cylindrical grid type sound absorption channel is formed, so that the sound energy dissipation can be effectively changed under the conditions of different cylindrical radiuses, working frequencies and gas temperatures.
The specific implementation process of the invention is as follows with reference to the attached drawings: substituting the parameter values in each embodiment into a wave equation, solving the wave equation numerically to obtain the distribution condition of the pressure disturbance on the space, obtaining the distribution condition of the speed disturbance on the space through a relational expression of the speed disturbance and the pressure disturbance, combining the relational expressions of the pressure disturbance, the speed disturbance and the sound wave amplitude to obtain the sound wave amplitude propagated downstream and the sound wave amplitude propagated upstream, and further obtaining the loss condition of the energy of the sound wave under the action of thermal viscous dissipation through a dissipation coefficient definition expression.
The above description of the invention and its embodiments is not intended to be limiting, and the illustrations in the drawings are intended to represent only one embodiment of the invention. Without departing from the spirit of the invention, it is within the scope of the invention to design structures or embodiments similar to the technical solution without creation.

Claims (5)

1. A modification method for improving acoustic energy dissipation in a diaphragm nozzle, comprising: for different milling degrees, the acoustic energy dissipation is changed, and different sound absorption effects are realized; xi is the milling degree which represents the proportion of the milled part, the larger the value is, the more the milled part is, and the definition is:
Figure FDA0002698546080000011
where R is the radius of the cylinder and d is the length of the uncut portion of the cylinder.
2. A modification method to improve acoustic energy dissipation in a diaphragm nozzle as defined in claim 1, wherein: the acoustic energy dissipation is calculated by simplifying the diaphragm nozzle model into a rectangular slit tube internal acoustic wave propagation model with an area gradient.
3. A modification method to improve acoustic energy dissipation in a diaphragm nozzle as set forth in claim 2, wherein: the method specifically comprises the following steps: the plane sound wave is transmitted in the tube of the variable cross-section rectangular slit, the height of the rectangular slit is 2a, the width of the rectangular slit is 2b, the cross-sectional area of the rectangular slit is 2a multiplied by 2b, wherein a > b, and no average flow exists in the tube; the pipe wall is rigid, medium particles near the pipe wall adhere to the pipe wall and have a velocity of 0, and the farther away from the pipe wall, the medium particles are restrained by the pipe wall to be small and have a high velocity, so that a velocity gradient is generated in the pipe, relative motion is generated among the media of the layers, and the medium particles are acted by viscous force.
4. A profiling method for improving acoustic energy dissipation in a diaphragm nozzle as claimed in claim 1 or claim 2, wherein: according to the momentum equation of the N-S equation, because viscous force acts on the cross section direction, neglecting the action of the viscous force on the slit length direction, the method obtains:
Figure FDA0002698546080000012
wherein ρ is density, η is dynamic viscosity, u is speed, y is slit width direction, i is imaginary unit, ω is acoustic frequency, p is pressure, x is slit length direction, subscript 0 parameter represents balance value, parameters not labeled with 0 are disturbance parameters;
similarly, neglecting the effect of thermal conduction in the direction of the slit length x, we obtain the energy equation:
Figure FDA0002698546080000021
wherein κ is heat transfer coefficient, T is gas temperature, CpIs the specific heat at constant pressure;
the boundary conditions of the velocity and temperature on the cross section are that when y ═ b, u ═ 0, and T ═ 0, the velocity and temperature distributions on the cross section are determined, and then averaged over the cross section:
Figure FDA0002698546080000022
Figure FDA0002698546080000023
wherein the subscript a represents the average value of the disturbance parameter in the cross-section, F (delta)1)、F(δ2) Are respectively delta1、δ2Function of (c):
Figure FDA0002698546080000024
Figure FDA0002698546080000025
wherein, delta1、δ2Acoustic viscous dissipation boundary layer thickness and acoustic thermal conduction dissipation boundary layer thickness, respectively, defined as:
Figure FDA0002698546080000026
Figure FDA0002698546080000027
the expression of the half width b of the variable cross-section rectangular slit along the change of the length x direction is as follows:
Figure FDA0002698546080000031
parameter bmIs the minimum gap value between adjacent baffle nozzles;
according to an ideal gas state equation:
Figure FDA0002698546080000032
the continuity equation is written as:
Figure FDA0002698546080000033
wherein t is a time variable, and c is a sound velocity;
substituting the obtained average speed and temperature of the cross section into a continuity equation to obtain a wave equation:
Figure FDA0002698546080000034
wherein γ is the specific heat ratio;
after the wave equation is solved, the distribution of the sound wave pressure in the axial space position is analyzed through numerical calculation, and the pressure disturbance is the sound wave A which is propagated downstream+And an acoustic wave A propagating upstream-I.e. p ═ a++A-And the velocity is disturbed ua＝kF(δ1)(A++A-)/ρ0ω, wave number of acoustic wave:
Figure FDA0002698546080000035
obtaining the acoustic wave amplitude A propagated downstream by solving the pressure disturbance and the speed disturbance+And the amplitude A of the acoustic wave propagating upstream-。
5. A profiling method for improving acoustic energy dissipation in a diaphragm nozzle as claimed in claim 1 or claim 2, wherein: defining an acoustic energy dissipation coefficient:
Figure FDA0002698546080000036
subscripts 1 and 2 represent the energy loss at the inlet and outlet, respectively, and the dissipation factor E represents the loss of acoustic energy due to hot tack, with higher values indicating higher losses.
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Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
RU2120560C1 (en) * 1997-08-06 1998-10-20 Федеральное государственное унитарное предприятие "Исследовательский центр им.М.В.Келдыша" Combustion chamber (versions)
JP4287349B2 (en) * 2004-09-30 2009-07-01 三菱重工業株式会社 Rocket injector
US20140075947A1 (en) * 2012-09-18 2014-03-20 United Technologies Corporation Gas turbine engine component cooling circuit
CN207297111U (en) * 2017-09-21 2018-05-01 德阳市海昌机械设备制造有限公司 A kind of novel steam turbine high intensity diaphragm structure
CN109057995A (en) * 2018-08-03 2018-12-21 北京航空航天大学 The partition nozzle best clearance design method and partition nozzle that can be dissipated based on sound
CN110805506A (en) * 2019-09-29 2020-02-18 北京航天动力研究所 Combined combustion stabilizing device

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
RU2120560C1 (en) * 1997-08-06 1998-10-20 Федеральное государственное унитарное предприятие "Исследовательский центр им.М.В.Келдыша" Combustion chamber (versions)
JP4287349B2 (en) * 2004-09-30 2009-07-01 三菱重工業株式会社 Rocket injector
US20140075947A1 (en) * 2012-09-18 2014-03-20 United Technologies Corporation Gas turbine engine component cooling circuit
CN207297111U (en) * 2017-09-21 2018-05-01 德阳市海昌机械设备制造有限公司 A kind of novel steam turbine high intensity diaphragm structure
CN109057995A (en) * 2018-08-03 2018-12-21 北京航空航天大学 The partition nozzle best clearance design method and partition nozzle that can be dissipated based on sound
CN110805506A (en) * 2019-09-29 2020-02-18 北京航天动力研究所 Combined combustion stabilizing device

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