CN113389659B - Design method of high-temperature fuel gas channel with low heat sink - Google Patents
Design method of high-temperature fuel gas channel with low heat sink Download PDFInfo
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- CN113389659B CN113389659B CN202110848263.8A CN202110848263A CN113389659B CN 113389659 B CN113389659 B CN 113389659B CN 202110848263 A CN202110848263 A CN 202110848263A CN 113389659 B CN113389659 B CN 113389659B
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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
- F02K9/96—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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- 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
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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
- F02K9/60—Constructional parts; Details not otherwise provided for
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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
- F02K9/60—Constructional parts; Details not otherwise provided for
- F02K9/62—Combustion or thrust chambers
- F02K9/64—Combustion or thrust chambers having cooling arrangements
Abstract
The invention discloses a design method of a high-temperature fuel gas channel with low heat sink, which comprises the following steps: acquiring the minimum heat flux density required to be conducted at each position along the high-temperature gas channel; determining the value range of the actual heat flux density required to be conducted at each position along the way of the high-temperature gas channel based on the minimum heat flux density; matching design is carried out on the number of the cooling grooves, the groove width and the groove height based on the flow of the coolant, and the heat transfer coefficient of the cooling structure is obtained; based on the actual heat flux density required to be conducted at each position along the way of the high-temperature gas channel the heat transfer coefficient of the cooling structure obtains the heat conduction resistance of the channel wall; and selecting the value of a design parameter to adapt to the heat conduction resistance of the channel wall, wherein the size parameter comprises the number of layers of the annular cavity, the thickness of each wall surface, the height of each annular cavity and the distance length between adjacent supporting ribs in each annular cavity. By optimally designing the specific size of the channel wall, the minimum consumption of working medium heat sink on the premise of ensuring safe work of the high-temperature fluid channel is realized.
Description
Technical Field
The invention relates to the technical field of high-temperature fuel gas channel design, in particular to a low-heat-sink high-temperature fuel gas channel design method.
Background
In the application process of the high-temperature gas channel, the wall surface of the high-temperature gas channel generally has an upper working temperature limit in consideration of the high-temperature resistance strength of the channel wall material, and when the fluid temperature exceeds the upper usable material temperature limit, a proper heat dredging scheme is required to be adopted to ensure that the temperature of the inner wall of the channel works below the usable limit temperature of the material.
The heat dredging scheme which can work for a long time is generally an active cooling scheme, and particularly adopts a flow channel which is reasonably arranged in a wall surface and through which a cooling working medium flows, so that heat which exceeds the safe working bearing range of the inner wall of a gas channel is taken away in time, the temperature of the inner wall of the channel is kept to be lower than the limit working temperature, and the temperature of the cooling working medium is increased in the process. However, in practical applications, it is often necessary to operate the inner wall of the hot gas channel as uniformly as possible and slightly below its limit operating temperature. In this case, when the cooling flow, the allowable temperature rise, the area, and the like are insufficient, and the cooling capacity of the coolant is insufficient, the inner wall of the gas passage is overheated, and the cooling fails. However, if the mass of the cooling working medium, the allowable temperature rise, the cooling area and the like are increased too much, the conducted heat flow is too much, too much working medium heat sink is consumed, and energy waste is caused. Therefore, under the background condition, the active cooling scheme of the high-temperature fuel gas channel needs to be optimally designed, so that the high-temperature fuel gas channel can be ensured to reliably work under the condition that the heat sink consumption of the coolant is as low as possible.
Disclosure of Invention
Aiming at the defects in the prior art, the invention provides a high-temperature gas channel design method with low heat sink, which realizes that the heat sink consumption of the working medium is minimum on the premise of ensuring the safe work of the high-temperature gas channel.
In order to achieve the purpose, the invention provides a method for designing a high-temperature gas channel with low heat sink, wherein the high-temperature gas channel comprises a channel wall and a cooling structure, the channel wall comprises a plurality of wall surfaces with cylindrical structures, and the wall surfaces are sleeved layer by layer, wherein a cylindrical-structure annular cavity is arranged between every two adjacent wall surfaces, each two adjacent wall surfaces are connected through a support rib, the support ribs in the adjacent annular cavities are staggered with each other, the cooling structure is a plurality of cooling grooves which are arranged on the outermost wall surface at intervals along the circumferential direction, heat insulation materials are filled in the annular cavities, and the innermost wall surface is provided with a heat insulation coating;
the design method specifically comprises the following steps:
step 4, obtaining the heat conduction resistance of the channel wall based on the actual heat flux density required to be conducted at each position along the high-temperature gas channel and the heat transfer coefficient of the cooling structure;
and 6, carrying out finite element calculation and checking on the design result in the step 5, if the design result exceeds the constraint condition, modifying the value range of the actual heat flow density, and repeating the steps 3-5 until the constraint condition is met.
In one embodiment, in step 1,
considering the case of gas radiation, the process of obtaining the minimum heat flux density is as follows:
q min ＝h wg (T aw -T mh )+q r (1)
in the formula, q min At minimum heat flux density, T mh Is the reliable working temperature, T, of the inner wall of the high-temperature gas channel aw For the recovery temperature of the gas surface of the high-temperature gas channel, h wg Is the convective heat transfer coefficient between the fuel gas in the high-temperature fuel gas channel and the inner wall of the high-temperature fuel gas channel, q r Is the gas radiation heat flow;
wherein:
in the formula, T c，ns The total temperature of the high-temperature fuel gas is determined, r is a local recovery coefficient, M is the local fuel gas flowing Mach number of each position along the high-temperature fuel gas channel, and k is the specific heat ratio of the fuel gas mixture; setting a certain section X of high-temperature fuel gas generated by combustion of the liquid rocket engine, and obtaining a corresponding virtual engine throat area A by iterative solution according to the flowing Mach number M of the high-temperature fuel gas t ：
And then the heat convection coefficient h of the high-temperature fuel gas and the wall surface wg Can be obtained from the Bartz formula:
in the formula, D t The equivalent throat diameter is the diameter of the throat,
c pg is the specific heat at constant pressure of gas, mu g Is gas dynamic viscosity, pr g Is the Plantt number, p, of the gas c.ns Is the total pressure of high-temperature fuel gas, c * The characteristic speed can be obtained by thermal calculation of a rocket engine, R is the curvature radius of a nozzle at the throat part, the influence of the term is small, and R = D can be taken at the position t σ is a correction coefficient;
if the inner wall of the high-temperature gas channel is provided with the heat insulation coating, T in the formula is required to be used mh Replacing with the gas side temperature T of the heat insulation coating tcg Further, further
In the formula, delta tc And λ tc The thickness and the thermal conductivity of the thermal insulation coating are respectively shown, in this case, the combination of the two types of the thermal insulation coatings (1) and (6) is adopted, and an iterative solution method is adopted to obtain T tcg Further, q is obtained min 。
In one embodiment, the calculation process of the correction coefficient is as follows:
in one embodiment, in step 3, the number of cooling slots, the slot width, and the slot height are designed to be matched based on the flow rate of the coolant, specifically:
obtaining the flow velocity V of the coolant L Wherein the flow velocity V of the coolant L Is in the range of 1 to 10m/s and is based on the flow velocity V of the coolant L Obtaining the total flow area A of each cooling tank L ：
In the formula, ρ L It is the density of the coolant that is,
is the flow rate of the coolant;
on the basis of the above steps:
A L ＝N L W L H L (9)
in the formula, N L 、W L 、H L N is selected as the number, width and height of the cooling grooves L 、W L 、H L Is chosen such that it satisfies the total flow area A L And (4) finishing.
In one embodiment, in step 3, the heat transfer coefficient of the cooling structure is calculated by:
in the formula, h wL Heat transfer coefficient, p, for cooling structures L Is the density of the coolant, λ L Is the heat conductivity coefficient of the coolant, pr L As the prandtl number, V, of the coolant L Flow rate of coolant, μ L Viscosity of the coolant, D L For the hydraulic diameter of the cooling channel, for a rectangular channel, there are:
in one embodiment, step 4, the heat conduction resistance of the channel wall is obtained based on the actual heat flow density required to be conducted at each position along the high-temperature gas channel and the heat transfer coefficient of the cooling structure, specifically:
the relationship between the total heat conduction thermal resistance, the temperature difference between the inner wall and the outer wall of the high-temperature gas channel and the actual heat flux density is as follows:
the derivation yields:
wherein q is the actual heat flux density of the high-temperature gas channel, R w Denotes the thermal conductivity resistance, T, of the channel walls L Which is indicative of the temperature of the coolant,
denotes the thermal resistance of convective heat transfer, R, on the coolant side g Comprehensive thermal resistance of a gas side:
wherein, the gas side comprehensive thermal resistance R g Comprising gas-side pairsThermal resistance by heat exchange, radiation and thermal resistance delta of thermal barrier coating tc /λ tc The combined action of the above-mentioned ingredients.
In one embodiment, in step 5, the values of the design parameters including the number m of the ring cavities and the thickness δ of each wall surface are selected to adapt to the thermal conductivity and resistance of the channel walls in step 4 n Height H of each ring cavity n And the distance length L between adjacent supporting ribs in each ring cavity n ，n＝1,2,…,m；
Under the condition of giving gas side parameters, coolant side parameters, channel wall physical parameters, wall radiation parameters and the like, the temperature distribution and the heat conduction resistance R of the gas channel wall can be obtained by a finite element method w ；
In the initial design, the temperature of the inner and outer side walls of each ring cavity is assumed to be consistent and is T ns And T nX Calculating by the following simplified calculation formula, after the optimized parameters are determined, refining and checking are carried out, and finally, each design parameter of the channel wall is determined, wherein the simplified calculation method specifically comprises the following steps:
for the channel wall with m ring cavities, the heat conduction thermal resistance mainly comprises the heat conduction thermal resistance of m +1 wall surfaces and the radiation thermal resistance of m ring cavities, and as the ring cavities are filled with heat insulation materials, the radiation thermal resistance of the ring cavities is considered to be 0, so when m =1, the heat conduction thermal resistance R of the channel wall 1w The following equation is satisfied:
in the formula of lambda w Represents the wall material thermal conductivity, delta 1 Denotes the wall thickness of the first wall, H 1 Denotes the height of the first layer of the ring cavity, L 1 Represents the length of the space between adjacent support ribs within the first layer of annular cavities, delta f Representing the wall thickness of the last layer of wall surface, wherein epsilon is the surface blackness of the wall surface material;
thereafter, every time the number of m increases by 1, the following parameter is added to the right term of the above equation (14):
in the formula, delta n Represents the wall thickness of the n-th wall surface, H n Denotes the height of the ring cavity of the nth layer, L n Showing the distance length between adjacent support ribs in the ring cavity of the nth layer;
and finally:
based on numerical simulation, the method takes the lightest structural mass as an optimization target and takes the thermal stress requirement, the maximum temperature of the wall surface, the coolant flow, the temperature rise and the like as constraints, and selects m and delta n 、δ f 、H n 、L n Wherein n =1,2, ·, m.
The invention provides a design method of a high-temperature gas channel with low heat sink, which forms a channel wall of the high-temperature gas channel by sleeving a plurality of cylindrical wall surfaces layer by layer, and forms an annular cavity between the adjacent wall surfaces, so that heat flow transmitted from the inner wall of the channel to the outer wall of the channel is greatly reduced, and the minimum consumption of working medium heat sink on the premise of ensuring safe work of the high-temperature fluid channel is realized by optimally designing the specific size of the channel wall.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the structures shown in the drawings without creative efforts.
FIG. 1 is a schematic structural view of a wall surface of a high-temperature gas channel in an embodiment of the present invention;
FIG. 2 is a schematic diagram of a first embodiment of a support rib according to the present invention;
FIG. 3 is a schematic diagram of a second embodiment of a support rib according to the present invention;
FIG. 4 is a schematic diagram of a third embodiment of a support rib according to the present invention;
FIG. 5 is a schematic diagram illustrating a fourth exemplary embodiment of a support rib according to the present invention;
FIG. 6 is a schematic diagram illustrating a fifth exemplary embodiment of a support rib according to the present invention;
FIG. 7 is a schematic diagram of a sixth embodiment of a support rib according to the present invention;
fig. 8 is a schematic flow diagram of a method for designing a high-temperature fuel gas channel with low heat sink in the embodiment of the present invention.
Reference numbers: wall 1, annular chamber 2, support rib 3, cooling trough 4, floor 5.
The implementation, functional features and advantages of the objects of the present invention will be further explained with reference to the accompanying drawings.
Detailed Description
The technical solutions in the embodiments of the present invention will be described clearly and completely with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be obtained by a person skilled in the art without inventive step based on the embodiments of the present invention, are within the scope of protection of the present invention.
It should be noted that all directional indicators (such as up, down, left, right, front, back \8230;) in the embodiments of the present invention are only used to explain the relative positional relationship between the components, the motion situation, etc. in a specific posture (as shown in the attached drawings), and if the specific posture is changed, the directional indicator is changed accordingly.
In addition, the descriptions related to "first", "second", etc. in the present invention are only for descriptive purposes and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of the feature. In the description of the present invention, "a plurality" means at least two, e.g., two, three, etc., unless specifically limited otherwise.
In the present invention, unless otherwise expressly stated or limited, the terms "connected," "secured," and the like are to be construed broadly, and for example, "secured" may be a fixed connection, a removable connection, or an integral part; the connection can be mechanical connection, electrical connection, physical connection or wireless communication connection; they may be directly connected or indirectly connected through intervening media, or they may be interconnected within two elements or in a relationship where two elements interact with each other unless otherwise specifically limited. The specific meanings of the above terms in the present invention can be understood by those skilled in the art according to specific situations.
In addition, the technical solutions in the embodiments of the present invention may be combined with each other, but it must be based on the realization of the technical solutions by those skilled in the art, and when the technical solutions are contradictory to each other or cannot be realized, such a combination of the technical solutions should not be considered to exist, and is not within the protection scope of the present invention.
As shown in fig. 1, the present embodiment discloses a high-temperature gas channel, which includes a channel wall and a cooling structure located at the periphery of the channel wall, specifically, the channel wall includes a plurality of tubular wall surfaces 1, and each wall surface 1 is sleeved layer by layer, wherein a tubular annular cavity 2 is provided between two adjacent wall surfaces 1, and each two adjacent wall surfaces 1 are connected through a support rib 3, and the support ribs 3 in two adjacent annular cavities 2 are staggered with each other, that is, the support rib in any annular cavity is located at the middle position between two adjacent support members in the adjacent annular cavity. The cooling structure is a plurality of cooling grooves 4 which are arranged on the wall surface 1 of the outermost layer at intervals along the circumferential direction, the adjacent cooling grooves 4 are separated by ribbed plates 5, and heat-insulating materials are filled in the annular cavity. The channel wall is set to be of a structure with multiple layers of wall surfaces 1, so that heat flow transmitted from the inner wall of the channel wall to the outer wall of the channel wall is greatly reduced, and the minimum heat sink consumption of the working medium of the high-temperature gas channel is realized on the premise of ensuring safe work. In this embodiment, the inner wall of the high-temperature gas channel is generally made of a material that can be manufactured by advanced manufacturing technologies such as additive manufacturing, and the inner wall of the high-temperature gas channel can be in direct contact with the gas, and a heat insulation coating or an oxidation resistant coating can be additionally added. It should be noted that the support rib 3 in the high-temperature gas channel may be a solid rib structure as shown in fig. 1, a hollow circular tube or square tube structure as shown in fig. 2-3, or a combination structure of a solid rib and a hollow circular tube or square tube as shown in fig. 4-7.
Based on the high-temperature gas channel with the above structure, referring to fig. 8, the embodiment discloses a design method of a high-temperature gas channel with low heat sink, which specifically includes:
For the minimum heat flow density required to be conducted at any position along the high-temperature gas channel, the acquisition process under the condition of considering the gas radiation is as follows:
q min ＝h wg (T aw -T mh )+q r (1)
in the formula, q min Is the minimum heat flow density; t is a unit of mh The reliable working temperature of the inner wall of the high-temperature gas channel is determined by the material characteristics of the wall surface, and the unit is K; t is aw The unit is K, which is the recovery temperature of the gas surface of the high-temperature gas channel; h is a total of wg The heat convection coefficient between the fuel gas in the high-temperature fuel gas channel and the inner wall of the high-temperature fuel gas channel is W.m -2 ·K -1 ，q r Is the gas radiation heat flow;
in the formula, epsilon w,ef Effective wall blackness, σ 0 Is Stefin-Boltzmann constant, σ 0 ＝5.67×10 -8 W/(m 2 ·K 4 )，ε g Is the emissivity of high temperature gas, alpha w Is the wall gas absorption ratio, T g The temperature is high-temperature gas static temperature;
wherein:
in the formula, T c，ns The total temperature of the high-temperature fuel gas is M, the local fuel gas flowing Mach number of each position along the high-temperature fuel gas channel is M, and k is the specific heat ratio of the fuel gas mixture; r is the local coefficient of restitution, expressed as the ratio of the temperature increase due to friction to the temperature increase due to adiabatic compression, determined experimentally or estimated from the following simplified relationship of the prandtl number, namely the relationship corresponding to laminar and turbulent flows, respectively:
setting a certain section X of high-temperature fuel gas generated by combustion of the liquid rocket engine, and obtaining a corresponding virtual engine throat area A by iterative solution according to the flowing Mach number M of the high-temperature fuel gas t ：
Thereby the heat convection coefficient h of the high-temperature fuel gas and the wall surface wg Can be obtained from the Bartz formula:
in the formula, D t The equivalent throat diameter is the diameter of the throat,
c pg is the specific heat at constant pressure of gas, mu g Is gas dynamic viscosity, pr g Is the Plantt number, p, of the gas c.ns Is the total pressure of high-temperature fuel gas, c * The characteristic speed can be obtained by thermal calculation of a rocket engine, R is the curvature radius of a nozzle at the throat part, the influence of the term is small, and R = D can be taken at the position t σ is a correction coefficient;
if the inner wall of the high-temperature gas channel is provided with the heat insulation coating, the T in the formula is required to be used mh Gas side temperature T of heat insulation coating tcg Further, it is possible to obtain
In the formula, delta tc And λ tc Respectively the thickness and the heat conductivity of the heat insulation coating, in this case, the combination of the two types (1) and (6) and an iterative solution method are adopted to obtain T tcg Further, q is obtained min 。
The calculation process of the correction coefficient sigma is as follows:
for any position along the path of the high-temperature fuel gas channel, the minimum heat flow density is q min The actual heat flux density of which is generally in ratio to q min Slightly larger, e.g. at a minimum heat flux density of q min The initial value range of the actual heat flux density q can be located: 1.05q min ≤q≤1.5q min And in the subsequent checking process of the step 6, adjusting the initial value range of the actual heat flow density q based on the checking structure.
And 3, matching and designing the number, the width and the height of the cooling grooves based on the flow of the coolant, and obtaining the heat transfer coefficient of the cooling structure.
Generally speaking, the selectable flow rate range is wide, and the initial value of the flow rate can be 1-10 m/s. However, from a design point of view, too high a flow rate means a small flow area of the coolant and a large pressure loss; a low flow rate means a large flow area for the coolant and increased processing costs. Therefore, for the purpose of optimizing the design, it is common to construct optionsSelecting an intermediate flow velocity V L =5m/s as initial value and based on the flow velocity V of the coolant L Obtaining the total flow area A of each cooling tank L ：
In the formula, ρ L It is the density of the coolant that is,
is the flow rate of the coolant;
on the basis of the above steps:
A L ＝N L W L H L (9)
in the formula, N L 、W L 、H L N is selected as the number, width and height of the cooling grooves L 、W L 、H L Is chosen such that it satisfies the total flow area A L And (4) finishing. In this embodiment, the selectable range of the groove width is wide, but the value of the groove width is 1-6 mm in consideration of pressure bearing and processing. Meanwhile, the rib plates are arranged between the grooves, the width of each rib plate is not more than the width of each groove generally, and the rib plates are not too narrow in consideration of structural strength, so that the width of each rib plate is limited to be 0.4-3 mm, and after the width of each groove and the width of each rib plate are determined, the number of the cooling grooves and the height of each groove can be determined.
And the calculation process of the heat transfer coefficient of the cooling structure is as follows:
in the formula, h wL Heat transfer coefficient, p, for cooling structures L Is the density of the coolant, λ L Is the heat conductivity coefficient of the coolant, pr L Is the prandtl number, V, of the coolant L Flow rate of coolant, μ L Viscosity of the coolant, D L For the hydraulic diameter of the cooling channel, for a rectangular channel, there are:
step 4, obtaining the heat conduction resistance of the channel wall based on the actual heat flux density required to be conducted at each position along the high-temperature gas channel and the heat transfer coefficient of the cooling structure, and specifically comprising the following steps:
the relationship between the total heat conduction resistance, the temperature difference between the inner wall and the outer wall of the high-temperature gas channel and the actual heat flux density is as follows:
the derivation yields:
wherein q is the actual heat flux density of the high-temperature gas channel, R w Denotes the thermal conductivity and resistance of the channel wall, T L Which is indicative of the temperature of the coolant,
denotes the thermal convection resistance, R, of the coolant side g Comprehensive thermal resistance of a gas side:
wherein, the gas side comprehensive thermal resistance R g Comprising the thermal resistance of the gas side for heat convection, the thermal resistance of radiation and the thermal resistance delta of a heat-insulating coating tc /λ tc The combined action of the above-mentioned ingredients.
And 5, selecting design parameter values to adapt to the heat conduction and heat resistance of the channel wall in the step 4, wherein the design parameters comprise the number m of layers of the annular cavity and the thickness delta of each wall surface n Height H of each ring cavity n And the distance length L between adjacent supporting ribs in each ring cavity n N =1,2, \8230;, m; the method comprises the following specific steps:
at given gas side parametersUnder the conditions of coolant side parameters, channel wall physical property parameters, wall radiation parameters and the like, the temperature distribution and the heat conduction resistance R of the gas channel wall can be obtained by a finite element method w The gas side parameters comprise a convective heat transfer coefficient and a recovery temperature, and the coolant side parameters comprise a convective heat transfer coefficient and a coolant temperature;
in the initial design, the temperature of the inner and outer side walls of each ring cavity is assumed to be consistent and is T ns And T nX The method comprises the following steps of calculating by using a simplified calculation formula, refining and checking after the optimized parameters are determined, and finally determining all design parameters of the channel wall, wherein the simplified calculation method specifically comprises the following steps:
for the channel wall with m ring cavities, the heat conduction thermal resistance mainly comprises the heat conduction thermal resistance of m +1 wall surfaces and the radiation thermal resistance of m ring cavities, and as the ring cavities are filled with heat insulation materials, the radiation thermal resistance of the ring cavities is considered to be 0, so when m =1, the heat conduction thermal resistance R of the channel wall 1w The following equation is satisfied:
in the formula of lambda w Represents the wall material thermal conductivity, delta 1 Denotes the wall thickness of the first wall, H 1 Denotes the height of the first layer of the ring cavity, L 1 Representing the length of the spacing, δ, between adjacent support ribs in the first layer of the annulus f The wall thickness of the last wall is shown, and ∈ is the surface blackness of the wall material, and in this example, ∈ =0.8.
Thereafter, every time the number of m increases by 1, the following parameters are added to the right term of the above equation (14):
in the formula, delta n Represents the wall thickness of the n-th wall surface, H n Denotes the height of the ring cavity of the nth layer, L n Showing the spacing length between adjacent support ribs in the ring cavity of the nth layer.
And finally:
based on numerical simulation, the method takes the lightest structural mass as an optimization target, takes the thermal stress requirement, the maximum temperature of the wall surface, the coolant flow, the temperature rise and the like as constraints, and selects m and delta n 、δ f 、H n 、L n Wherein n =1,2, ·, m.
During the numerical simulation, the thickness δ of the layer closest to the gas side 1 The thickness can be properly selected, preferably 0.5-1.5 mm, while the thickness of the wall surface of other layers can be 0.3-1 mm, and the value range of the height of each ring cavity is 1-4 mm; the distance length between adjacent supporting ribs in each ring cavity ranges from 2 mm to 10mm.
And 6, completing the initial structural design of the high-temperature gas channel after completing the design of the sizes and the numerical values, performing finite element calculation and checking on the basis of the initial structural design, and repeating the steps 3-5 after modifying the value range of the actual heat flow density if constraint conditions are exceeded, wherein the constraint conditions comprise the thermal stress requirement, the maximum temperature of the wall surface, the coolant flow and the temperature rise. If the checking structure exceeds the constraint condition, the value range of the actual heat flux density is expanded, for example, the value range of the actual heat flux density is changed from 1.05q min ～1.5q min Modified to 1.5q min ～1.7q min . If the checking result has a margin, the value range of the actual heat flux density is narrowed, for example, the value range of the actual heat flux density is set to 1.05q min ～1.5q min Modified to 1.05q min ～1.3q min 。
The above description is only a preferred embodiment of the present invention, and is not intended to limit the scope of the present invention, and all modifications and equivalents of the present invention, which are made by the contents of the present specification and the accompanying drawings, or directly/indirectly applied to other related technical fields, are included in the scope of the present invention.
Claims (7)
1. The design method of the high-temperature gas channel with low heat sink is characterized in that the high-temperature gas channel comprises a channel wall and a cooling structure, the channel wall comprises a plurality of wall surfaces with cylindrical structures, and the wall surfaces are sleeved layer by layer, wherein a cylindrical annular cavity is arranged between every two adjacent wall surfaces, every two adjacent wall surfaces are connected through a support rib, the support ribs in the adjacent annular cavities are staggered with each other, the cooling structure is a plurality of cooling grooves formed in the outermost wall surface at intervals along the circumferential direction, heat insulation materials are filled in the annular cavities, and a heat insulation coating is arranged on the innermost wall surface;
the design method specifically comprises the following steps:
step 1, acquiring minimum heat flux density required to be conducted at each position along the path of a high-temperature gas channel;
step 2, determining the value range of the actual heat flux density required to be conducted at each position along the way of the high-temperature gas channel based on the minimum heat flux density;
step 3, matching design is carried out on the number, the width and the height of the cooling grooves based on the flow of the coolant, and the heat transfer coefficient of the cooling structure is obtained;
step 4, obtaining the heat conduction resistance of the channel wall based on the actual heat flux density required to be conducted at each position along the high-temperature gas channel and the heat transfer coefficient of the cooling structure;
step 5, selecting values of design parameters to adapt to the thermal conduction resistance of the channel wall in the step 4, wherein the design parameters comprise the number of layers of the ring cavities, the thickness of each wall surface, the height of each ring cavity and the distance length between adjacent supporting ribs in each ring cavity;
and 6, performing finite element calculation checking on the design result in the step 5, if the design result exceeds the constraint condition, modifying the value range of the actual heat flow density, and repeating the steps 3-5 until the constraint condition is met.
2. The method for designing the high-temperature gas channel with low heat sink as claimed in claim 1, wherein in step 1,
in the case of considering the gas radiation, the minimum heat flux density is obtained by the following steps:
q min ＝h wg (T aw -T mh )+q r (1)
in the formula, q min At minimum heat flux density, T mh Is a reliable working temperature, T, of the inner wall of the high-temperature gas channel aw For the recovery temperature of the gas surface of the high-temperature gas channel, h wg Is the convective heat transfer coefficient between the fuel gas in the high-temperature fuel gas channel and the inner wall of the high-temperature fuel gas channel, q r Is the gas radiation heat flow;
in the formula, epsilon w,ef Effective wall blackness, σ 0 Is Stefin-Boltzmann constant, ε g Is the emissivity of high temperature gas, alpha w Is the wall gas absorption ratio, T g The static temperature of high-temperature gas is adopted;
wherein:
in the formula, T c，ns The total temperature of the high-temperature fuel gas is determined, r is a local recovery coefficient, M is the local fuel gas flowing Mach number of each position along the high-temperature fuel gas channel, and k is the specific heat ratio of the fuel gas mixture; setting a certain section X of high-temperature fuel gas generated by combustion of the liquid rocket engine, and obtaining a corresponding virtual engine throat area A by iterative solution according to the flowing Mach number M of the high-temperature fuel gas t ：
And then the heat convection coefficient h of the high-temperature fuel gas and the wall surface wg Obtained from Bartz's equation:
in the formula D t The equivalent throat diameter is that of the throat section,
c pg is the specific heat at constant pressure of gas, mu g Is gas dynamic viscosity, pr g Is the prandtl number, p, of the gas c,ns Is the total pressure of high-temperature fuel gas, c * The characteristic speed is obtained by thermal calculation of the rocket engine, R is the curvature radius of the nozzle at the throat part, the influence of the term is small, and R = D is taken at the position t σ is a correction coefficient;
if the inner wall of the high-temperature gas channel is provided with the heat insulation coating, the T in the formula is required to be used mh Gas side temperature T of heat insulation coating tcg Further, further
In the formula, delta tc And λ tc Respectively the thickness and the heat conductivity of the heat insulation coating, in this case, the combination of the two types (1) and (6) and an iterative solution method are adopted to obtain T tcg Further, q is obtained min 。
3. The method for designing the high-temperature gas channel with the low heat sink as claimed in claim 2, wherein the calculation process of the correction coefficient is as follows:
4. the method for designing a high-temperature gas channel with low heat sink according to claim 3, wherein in step 3, the number of cooling grooves, the groove width and the groove height are designed to be matched based on the flow rate of the coolant, and specifically:
obtaining the flow velocity V of the coolant L Wherein the flow velocity V of the coolant L Is in the range of 1 to 10m/s and is based on the flow velocity V of the coolant L Obtaining the total flow area A of each cooling tank L ：
In the formula, ρ L It is the density of the coolant that is,
is the flow rate of the coolant;
on the basis of the above steps:
A L ＝N L W L H L (9)
in the formula, N L 、W L 、H L N is selected as the number, width and height of the cooling grooves L 、W L 、H L Is chosen such that it satisfies the total flow area A L And (4) finishing.
5. The method for designing the high-temperature gas channel with the low heat sink as claimed in claim 4, wherein in step 3, the calculation process of the heat transfer coefficient of the cooling structure comprises:
in the formula, h wL Heat transfer coefficient, p, for cooling structures L Is the density of the coolant, λ L Is the heat conductivity coefficient of the coolant, pr L Is the prandtl number, V, of the coolant L Flow rate of coolant,. Mu. L Viscosity of the coolant, D L For the hydraulic diameter of the cooling channel, for a rectangular channel, there are:
6. the method for designing a high-temperature gas channel with low heat sink according to claim 5, wherein in step 4, the thermal conductivity and resistance of the channel wall are obtained based on the actual heat flux density required to be conducted at each position along the high-temperature gas channel and the heat transfer coefficient of the cooling structure, specifically:
the relationship between the total heat conduction thermal resistance, the temperature difference between the inner wall and the outer wall of the high-temperature gas channel and the actual heat flux density is as follows:
the derivation yields:
wherein q is the actual heat flux density of the high-temperature gas channel, R w Denotes the thermal conductivity and resistance of the channel wall, T L Which is indicative of the temperature of the coolant,
denotes the thermal resistance of convective heat transfer, R, on the coolant side g Comprehensive thermal resistance of a gas side:
wherein, the gas side comprehensive thermal resistance R g The comprehensive functions of the convective heat transfer thermal resistance and the radiation thermal resistance of the gas side and the thermal resistance of the heat insulation coating are included.
7. The method for designing the high-temperature gas channel with the low heat sink as recited in claim 1, wherein in step 5, values of design parameters are selected to adapt to the thermal conductivity and resistance of the channel wall in step 4, and the design parameters include the number m of the ring cavity layers and the thickness δ of each wall surface n Height H of each ring cavity n Adjacent supports in each ring cavityThe length L of the space between the ribs n ，n＝1,2,…,m；
Under the condition of given gas side parameters, coolant side parameters, channel wall physical property parameters and wall radiation parameters, obtaining the gas channel wall temperature distribution and the heat conduction resistance R by a finite element method w ；
In the initial design, the temperature of the inner and outer side walls of each ring cavity is assumed to be consistent and is T ns And T nX The method comprises the following steps of calculating by using a simplified calculation formula, refining and checking after the optimized parameters are determined, and finally determining all design parameters of the channel wall, wherein the simplified calculation method specifically comprises the following steps:
for the channel wall with m ring cavities, the heat conduction thermal resistance mainly comprises the heat conduction thermal resistance of m +1 wall surfaces and the radiation thermal resistance of m ring cavities, and as the ring cavities are filled with heat insulation materials, the radiation thermal resistance of the ring cavities is considered to be 0, so when m =1, the heat conduction thermal resistance R of the channel wall 1w The following equation is satisfied:
in the formula, λ w Represents the wall material thermal conductivity, delta 1 Denotes the wall thickness of the first wall, H 1 Denotes the height of the first layer of the ring cavity, L 1 Representing the length of the spacing, δ, between adjacent support ribs in the first layer of the annulus f The wall thickness of the last wall is shown;
thereafter, every time the number of m increases by 1, the following parameters are added to the right term of the above equation (14):
in the formula, delta n Represents the wall thickness of the n-th wall surface, H n Denotes the height of the ring cavity of the nth layer, L n Showing the distance length between adjacent support ribs in the ring cavity of the nth layer;
and finally:
based on numerical simulation, the method takes the lightest structural mass as an optimization target and takes the thermal stress requirement, the maximum temperature of the wall surface, the coolant flow and the temperature rise as constraints and selects m and delta n 、δ f 、H n 、L n Wherein n =1,2, ·, m.
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