CN101738316A - Method for designing structure of low-cost test combustion chamber with reliable thermal protection - Google Patents

Abstract

The invention discloses a method for designing a structure of a low-cost test combustion chamber with reliable thermal protection. The combustion chamber comprises a body barrel segment, a connecting flange, a nozzle part, a connecting bolt and a measuring filler neck part. The combustion chamber adopts a capacitive type structure; the body barrel segment is made of a pure copper material with a high thermal conductivity; and the nozzle part is made from a copper-infiltrated tungsten material. In the invention, a thermal analysis aided design method is required to be used firstly, which needs to establish a computation mode and a computing method at first and then perform an iterative design process of the structural design and the thermal analysis. The computation mode adopts an unsteady thermal-dimensional heat conducting differential equation and the computed heat exchange mainly comprises heat convection from the gas to the chamber wall and the radiant heat exchange, the heat conduction in the chamber wall, the convection from the chamber wall to the outside and the radiant heat exchange. The thermal analysis aided design method comprises a global computing analysis and a local correcting and computing analysis. The method can minimize the materials used under the condition that the combustion chamber has the reliable thermal protection and greatly reduce the cost.

Description

Construction design method with low-cost test combustion chamber of reliable thermal protection

[technical field]

The present invention relates to a kind of be used for short time test have reliable thermal protection and a low-cost chamber structure method for designing.The present invention is used in particular for being applied to the Combustion chamber design method of liquid-propellant rocket engine test.

[background technology]

In the development process of thrust chamber, particularly in the development process as the ejector filler of thrust chamber primary clustering, need carry out the burning test research of a large amount of short time; In addition, to the heat transfer characteristic of thrust chamber or heat flow measurement research and in testing, also must carry out the burning test research of short time.

Carry out in the thrust chamber experimental study, generally adopt two kinds of chamber structure forms, promptly hold hot type and water cooling formula.And in order to obtain in test data the most widely, the experimental study of more fully carrying out, and can save cost and cycle, thrust chamber body portion need have the convenience of measurement, parts are easy to characteristics such as replacing and displacement.Because the test period demand is shorter, with regard to the unnecessary water-cooled structure that adopts complexity.And hold the hot type structure have simple in structure, cost is low, be convenient to advantage such as maintenance, and is suitable for the work of short time.General rocket engine field holds the hot type structure and is divided into two kinds of forms: 1, adopt tungsten to ooze ablation resistant materials such as copper, because the ablation resistance of material is extensive use of in the rocket engine field, particularly the larynx as thrust chamber jet pipe part serves as a contrast, but it is big that tungsten oozes rerum natura instability, the deviation of copper product long run test, material is easily oxidized, and often need combustion chamber wall surface is carried out temperature survey in the test, measuring accuracy just can not be reliable like this, and tungsten oozes copper machine work difficulty, cost height, and is very undesirable in the application of cylindrical section.2, adopt high thermal conductivity material such as fine copper because the rerum natura good stability of the long run test of red copper can guarantee the precision that wall surface temperature is measured reliably, and red copper to ooze the copper product cost with respect to tungsten lower; But because the low shortcoming of heat-resistant limit of copper product, the locular wall design of therefore general firing chamber is very thick in to satisfy the needs of test period, and generally can install and measure or portfire in body portion red copper body inside, will inevitably influence local heating's effect of red copper, ablate if design the unreasonable local overheating that causes possibly.These two kinds of methods all have application, but the cost of these two kinds of materials is not low, and particularly when the outside dimension of part is big more, along with the increase of radial dimension, will make material volume increase fast more, cost increases just fast more; If but the material that adopts is very few or localized design is unreasonable, it is not enough or heat-transfer effect is bad to make the firing chamber hold thermal effect, ablates easily, causes thermal protection unreliable.Therefore need a kind of concrete method and make the firing chamber of designing both have reliable thermal protection, have minimum cost again, this method for designing was not also reported.

[summary of the invention]

The purpose of this invention is to provide a kind of be used for short time test have reliable thermal protection and a low-cost chamber structure method for designing, particularly suitable under the larger-size situation in firing chamber.

A kind of have a reliable thermal protection low-cost test combustion chamber construction design method, and the designed firing chamber of this method comprises: parts such as body portion cylindrical section, joint flange, jet pipe part, coupling bolt and measurement pressure inlet.The firing chamber is adopted and is held the hot type structure, and the short material of body portion cylinder adopts the materials such as fine copper of high thermal conductivity, and jet pipe partly adopts tungsten to ooze exotic materials such as copper.Must at first adopt a kind of heat to analyze auxiliary design method.The heat that adopts is analyzed auxiliary design method at first needs to establish computation model and computing method, carries out structural design and thermoanalytical Iterative Design process again.Computation model adopts the three-dimensional unstable state heat conduction differential equation, the heat interchange of being calculated mainly comprise by combustion gas in the convection heat transfer of locular wall and radiation heat transfer, locular wall heat conduction and by convection current and the radiation heat transfer of locular wall to the external world; Adopt the Bartz formula to calculate the heat transfer of combustion gas, adopt experience radiation heat transfer formula to calculate the radiation heat transfer of combustion gas, adopt large space heat transfer free convection empirical correlation formula to calculate the heat transfer of outer wall, and ignore the radiation heat transfer of outer wall environment to locular wall to locular wall.Heat is analyzed auxiliary design method and is comprised overall calculation analysis and local check computational analysis.

Of the present invention have advantage and the good effect that reliable thermal protection low-cost test combustion chamber method for designing has and be: (1) is owing to only partly adopt resistant to elevated temperatures tungsten to ooze copper at jet pipe, and what adopt at the firing chamber of volume maximum body portion cylindrical section is the relatively low red copper material of cost, so just greatly reduce cost, can guarantee body portion temperature measurement accuracy again; (2) owing to adopted hot supplementary structure method for designing, and finish the Iterative Design of structure design and computational analysis, and carried out the hot computational analysis method that holistic approach and subrange are checked, this method for designing purpose is to make material volume used under the reliable situation of thermal protection minimum, therefore can guarantee that cost is minimum under the reliable situation of thermal protection.

[description of drawings]

Fig. 1 is a firing chamber body portion whole assembling synoptic diagram

Fig. 2 is hot auxiliary design method process flow diagram

Fig. 3 is the temperature profile of red copper cylindrical section

Fig. 4 is a red copper cylindrical section radial displacement distribution plan

Fig. 5 is that tungsten oozes copper nozzle section temperature profile

Fig. 6 is that tungsten oozes copper nozzle section radial displacement distribution plan

Fig. 7 is a pressure tap localized heat analyzing three-dimensional temperature profile

[embodiment]

Further specify the present invention below in conjunction with accompanying drawing with embodiment, present embodiment is a test liquid-propellant rocket engine thrust chamber.

The firing chamber of implementing the method design mainly comprises: body portion cylindrical section 1, joint flange 2, afterbody jet pipe 3, coupling bolt 4 and necessary pressure survey pressure inlet 5.

Whole design process is arranged as follows:

1, at first must set up CALCULATION OF THERMAL model and computing method:

1) thrust chamber chamber wall temperature computation model

It is the zoning that red copper and tungsten ooze the copper locular wall, is unstable state heat conduction, and body portion structure presents typical three-dimensional character, adopts the three-dimensional unstable state heat conduction differential equation:

$\mathrm{pc}\frac{\∂t}{\∂\mathrm{\τ}}=\frac{\∂}{\∂x}\left(\mathrm{\λ}\frac{\∂t}{\∂x}\right)+\frac{\∂}{\∂y}\left(\mathrm{\λ}\frac{\∂t}{\∂y}\right)+\frac{\∂}{\∂z}\left(\mathrm{\λ}\frac{\∂t}{\∂z}\right)+\stackrel{\·}{\mathrm{\Φ}}---\left(1\right)$

Boundary condition is determined by heat conduction at the interface, convection current, three kinds of heat exchange modes of radiation.

Because temperature variation is bigger in computing time, the physical parameter that must consider material carries out multiple spot interpolation processing with the material property parameter with variation of temperature along with variation of temperature.The finite element division is carried out in the whole zone of finding the solution, the utilization differential equation (1) and integration, simultaneous equations:

$\left[C\left(T\right)\right]\left\{\stackrel{\·}{T}\right\}+\left[K\left(T\right)\right]\left\{T\right\}=\left\{Q(T,t)\right\}---\left(2\right)$

[K] is conductance matrix, comprises coefficient of heat conductivity, convection coefficient and radiance and shape coefficient; [C] is the specific heat matrix, the increase of energy in the taking into account system; { T} is the node temperature vector;

Be the derivative of temperature to the time; { Q} is a node rate of heat flow vector, comprises thermal source.Initial-value problem with the partial differential equation problem of time and spatial domain discrete ordinary differential equation for n node temperature in spatial domain.

2) computation model of heat interchange

Hold the exchange of the hot type heat of cooling mainly comprise by combustion gas in the convection heat transfer of locular wall and radiation heat transfer, locular wall heat conduction and by convection current and the radiation heat transfer of locular wall to the external world.

A) combustion gas is to the heat transfer of locular wall

The common calculation methods is exactly to adopt the Bartz formula to calculate the convection heat transfer of combustion gas to locular wall:

$\left\{\begin{array}{c}{q}_w=h_g(T_{\mathrm{gs}}-T_{\mathrm{wg}})\\ h_g=\mathrm{const}.\frac{1}{{d_t}^{0.2}}\left(\frac{{\mathrm{\η}}^{0.2}{c}_p}{{P_r}^{0.6}}\right){\left(\frac{{p_c}^{*}}{c^{*}}\right)}^{0.8}{\left(\frac{A_t}{A}\right)}^{0.9}\mathrm{\σ}\end{array}\right.---\left(3\right)$

High temperature and high pressure environment has determined that radiation heat transfer wherein also is quite strong, and evenly the combustion gas of composition to the radiant heat flux densitometer formula of wall is:

$q_r={\mathrm{\ϵ}}_{w,\mathrm{ef}}\mathrm{\σ}({\mathrm{\ϵ}}_g{T_g}^4-a_w{T}_{\mathrm{wg}}^4)---\left(4\right)$

For the firing chamber, think q _rConstant, from contracting nozzle section d _r=1.2d _tRadiant heat flux sharply descends later on, arrives throat and only is left 50% of maximum hot-fluid, and the throat back descends faster, compares A/A at area _t=2,3,4 places, radiant heat flux drops to 12%, 6%, 3% of maximum hot-fluid.So big die swell ratio place radiation can be ignored.

To conduct heat and radiation is carried out comprehensive heat exchange and handled:

q＝q _w+q _r＝h _t(T _gs-T _wg) (5)

Wherein q is the comprehensive heat exchange hot-fluid to the basin radiation, h _tBe integrated heat transfer coefficient.

B) heat exchange of outer wall

The convection heat transfer of outer wall adopts large space heat transfer free convection empirical correlation formula:

Nu＝C(Gr?Pr) ⁿ， $\mathrm{Gr}=\frac{\mathrm{ga\Δt}{l}^3}{v^2}---\left(6\right)$

3) computing method

To locular wall different convection current and radiant heat flux will be arranged for different interior wall temperature combustion gas, at first temperature be divided in the temperature extremes scope of material, to different interior calculation of Wall Temperature comprehensive heat exchange hot-fluid separately; Model is carried out in the zone of being concerned about divide and modeling,, need carry out three-dimensional modeling, belong to axisymmetric model as nozzle section as arranging lighter and piezometric tube to belong to complicated three-dimensional situation.Can in modeling tools such as solidworks, carry out, the result is imported in the ansys software, define nonlinear material attribute, environment attribute, and the integrated heat transfer coefficient at each temperature of aforementioned calculation is imported; Carry out thermal transient-stress coupling analysis.

In high pressure, hot environment, the analysis of body portion red copper and throat is primary, and the heat analysis of follow-up part also is necessary, the analysis in picture piezometric tube zone, and be connected to each other analysis of face or the like between sealing surface position, part, whole design process is exactly that analytical calculation and the mutual iteration of structural design arrangement are carried out, and is illustrated in figure 2 as heat and analyzes the Aided Design basic flow sheet.The analysis of below getting several key positions is introduced.

2, firing chamber overall dimensions and partial structurtes determines

Under the situation that throat opening area is determined, body portion critical feature size is the determining of internal diameter of firing chamber.Under the situation of same pressure and mixing ratio, firing chamber cylindrical section internal diameter is more little, and the fuel gas flow Mach number is big more, and heat exchange will be strong more; In addition, when adopting the red copper material, material has good thermal conductivity and appearance is hot, and the NATURAL CONVECTION COEFFICIENT OF HEAT of outer wall is little, and the firing chamber internal diameter is the bigger the better for the heat exchange protection, and locular wall is thick more good more, but this all brings cost height and physical dimension to increase.The inner surface heat protection to key in the limited heat run time of too big wall thickness does not have effect, because hot-fluid does not have the enough time to pass to outermost layer.So seek under the situation that satisfies the testing requirements time firing chamber internal diameter and wall thickness minimum.By repeatedly iterative analysis calculating, finally designing internal diameter in the present embodiment is 90mm, the cylinder red copper section of wall thickness 60mm.In addition, the rising of temperature and the higher expansivity of red copper material, the variation of its axial dimension at high temperature also is to investigate one of point, computation model is got body portion and is analyzed for one section.Hot analysis result obtain behind the thrust chamber steady operation body portion red copper temperature profile such as Fig. 3 (unit: K), body portion red copper radial displacement distribution plan (unit: m) as shown in Figure 4 behind the thrust chamber steady operation.

The red copper section inwall highest temperature is 1015K behind the steady operation as seen from Figure 3, and the heat-resistant limit of red copper is 1273K, for warranty test safety keeps certain design margin.The radial displacement of red copper inner wall is no more than 0.2mm as shown in Figure 4.

Throat is positioned at the middle part of jet pipe, and at nozzle section, rapid variation all takes place for combustion gas parameter and jet pipe profile, must carry out the overall thermal analysis to whole jet pipe; Because throat's temperature ascensional range is big, and tungsten oozes copper with thermal deformation in the heat run process, and throat dimension changed the fluctuation greatly that senior general causes constant pressure, this is worthless, must estimate the deflection of its heat run process in addition.Model adopts axisymmetric model, and inside and outside wall is got non-homogeneous and uniform the 3rd class thermal boundary condition that changes vertically according to heat exchange result of calculation respectively, upper and lower surface and get adiabatic boundary condition with the stainless steel surface of contact.Result of calculation obtains Jet Pipe Temperature and distributes as Fig. 5, and radial displacement distributes as shown in Figure 6.

Zone after red copper section inwall high-temperature region occurs in throat and leans on behind the steady operation as seen from Figure 5, the highest temperature is 2379K, the heat-resistant limit that tungsten oozes copper is more than the 3000K, with the stainless surface of contact highest temperature be 730K.The radial displacement of maximum throat was less than 0.01mm when Fig. 6 illustrated test, and larynx directly is 41mm, and so little displacement is negligible.

In addition at red copper cylindrical section internal arrangement pressure tap etc., need these regional areas be analyzed, otherwise may cause the danger of ablation, illustrate the analysis in pressure tap zone here, Temperature Distribution result is as shown in Figure 7.Model is taken as: half the quadrant body of symmetry that upwards contains pressure tap week, get the distance in 3 times of pressure measurement apertures on the axial direction from head of combustion chamber, consider the influence of bolt hole and sealing ring simultaneously, inner and outer boundary is got the 3rd class boundary condition, symmetrical boundary condition is got in two sides, and its lap is all got adiabatic boundary condition.The result as can be seen, the existence of pressure tap is little to the influence of the inwall highest temperature.

Claims (5)

1. have reliable thermal protection low-cost test combustion chamber construction design method, described firing chamber comprises: body portion cylindrical section (1), joint flange (2), jet pipe part (3), coupling bolt (4) and measurement pressure inlet part (5).The firing chamber is adopted and is held the hot type structure, and body portion cylindrical section adopts the pure copper material of high thermal conductivity, and jet pipe partly adopts tungsten to ooze exotic materials such as copper.It is characterized in that: must at first adopt a kind of heat to analyze auxiliary design method.(Reference numeral)

2. according to claim 1 have a reliable thermal protection low-cost test combustion chamber construction design method, and design procedure comprises: (1) establishes computation model and the computing method that heat is analyzed Aided Design; (2) carry out structural design and thermoanalytical Iterative Design process.

3. according to claim 2 have a reliable thermal protection low-cost test combustion chamber construction design method, it is characterized in that: the computation model that heat is analyzed Aided Design adopts the three-dimensional unstable state heat conduction differential equation, the heat interchange of being calculated mainly comprise by combustion gas in the convection heat transfer of locular wall and radiation heat transfer, locular wall heat conduction and by convection current and the radiation heat transfer of locular wall to the external world.

4. according to claim 3 have a reliable thermal protection low-cost test combustion chamber construction design method, it is characterized in that: adopt the Bartz formula to calculate the convection heat transfer of combustion gas locular wall, employing experience radiation heat transfer formula calculates the radiation heat transfer of combustion gas to locular wall, adopt large space heat transfer free convection empirical correlation formula to calculate the convection heat transfer of outer wall, and ignore the radiation heat transfer of outer wall environment.

5. describedly have a reliable thermal protection low-cost test combustion chamber construction design method according to claim 1 or 2 or 3, it is characterized in that: the heat that adopts is analyzed auxiliary design method and is comprised the overall calculation analysis and locally check computational analysis.

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