CN106650242B - A cost evaluation method for long-term in-orbit evaporation control of cryogenic propellant - Google Patents

Abstract

The present invention relates to a kind of cost evaluation methods for cryogenic propellant in-orbit evaporation capacity control for a long time, this method considers the leaking heat of the long-term in-orbit storage evaporation amount control system each group part of cryogenic propellant comprehensively, and exhaust can utilize cooling capacity, cryogenic propellant in-orbit storage system evaporation capacity and evaporation rate for a long time are obtained first, evaporation capacity control measure bring weight cost is obtained again, and then the smallest optimal design operating condition of weight cost is obtained, for instructing the design of the in-orbit storage system of cryogenic propellant.The system effectivenesies indexs such as the present invention is light using system weight, power is few, realizability establish Engineering Assessment Method as optimization aim, can effectively carry out cryogenic propellant in-orbit evaporation capacity control system analysis for a long time.

Description

A cost evaluation method for long-term in-orbit evaporation control of cryogenic propellant

technical field

The invention relates to a cost evaluation method used for long-term on-orbit evaporation control of low-temperature propellants, belonging to the field of long-term on-orbit storage and management of low-temperature propellants.

Background technique

Low-temperature propellants have been widely used in domestic and foreign launch vehicles and upper stages due to their high specific impulse, non-toxic, non-polluting, and relatively low price. Cryogenic propellants are considered to be the most economical and efficient chemical propellants for entering space and orbital transfer, and are also the preferred propellants for future human lunar exploration, Mars exploration and longer-distance deep space exploration. Although low-temperature propellant has high performance, its boiling point is low, and it is easy to evaporate due to heat, and it is difficult to store for a long time. Due to the loss of low-temperature propellant, the performance of the launch vehicle and the execution of the mission will be significantly affected. Therefore, taking reasonable and effective measures to solve the control problem of low-temperature propellant evaporation, and finally achieve non-destructive storage, is an important prerequisite for long-term in-orbit application of low-temperature propellant, and it is also an urgent problem to be solved.

SUMMARY OF THE INVENTION

The object of the present invention is to overcome the above-mentioned defects of the prior art, and to provide a cost evaluation method for the long-term in-orbit evaporation control of low-temperature propellant, which obtains the evaporation and evaporation rate of the low-temperature propellant long-term in-orbit storage system, and then The weight cost brought by the evaporation control measures is obtained, and then the optimal design condition with the smallest weight cost is obtained, which is used to guide the design of the cryogenic propellant on-orbit storage system.

The above-mentioned purpose of the present invention is mainly achieved through the following technical solutions:

A cost assessment method for long-term in-orbit evaporation control of cryogenic propellant, comprising the following steps:

(1), determine the low-temperature propellant on-orbit storage net heat leakage Q _loss ;

(2) According to the net heat leakage Q _loss , the latent heat of evaporation γ corresponding to the saturation temperature of the low-temperature propellant, and the on-orbit working time t, the evaporation amount of the low-temperature propellant under different working conditions is obtained and evaporation rate i represents different working conditions, i=1, 2, ..., N, where N is the number of working conditions;

(3), to obtain the weight increase brought by the introduction of the refrigerator under different working conditions under the same conditions with the corresponding evaporation Summation to get the system weight penalty under this condition Traverse the weight cost of the system under all operating conditions Find System Weight Costs the minimum value of ;

(4), record system weight cost The working condition corresponding to the minimum value is taken as the optimal working condition.

In the above-mentioned cost evaluation method for long-term in-orbit evaporation control of cryogenic propellant, the specific method for determining the net heat leakage Q _loss of cryogenic propellant in orbit storage in the step (1) is as follows:

Q _loss =Q _MLI +Q _struts +Q _parastitic +Q _penetrations -Q _vapor -Q _cryocooler

Among them: Q _MLI is the heat leakage of the thermal insulation material on the surface of the propellant tank; Q _struts is the heat leakage of the propellant tank support structure; Q _parastitic is the heat leakage of the _{refrigerator ;} The cryo-propellant exhaust can utilize the cooling capacity; Q _cryocooler represents the cooling capacity of the cryocooler.

In the above cost evaluation method for long-term in-orbit evaporation control of low-temperature propellant, the formula for calculating the heat leakage Q _MLI of the thermal insulation material on the surface of the propellant tank is as follows:

Among them, T _hot is the outside temperature of the thermal insulation layer of the tank; T _cold is the temperature of the liquid low-temperature propellant inside the tank, and N _s is the total number of layers of multi-layer thermal insulation materials.

In the above cost evaluation method for long-term in-orbit evaporation control of low-temperature propellant, the calculation formula of the heat leakage Q _struts of the propellant tank support structure is as follows:

Q _struts for liquid oxygen propellant:

Among them: C ₁ is the design margin factor, C ₂ is 0.44, M _tank is the weight of the cryogenic propellant tank; M _propellant is the weight of the cryogenic propellant;

Q _struts for liquid hydrogen propellant:

Where: C' ₂ is 0.021.

In the above-mentioned cost evaluation method for long-term in-orbit evaporation control of cryogenic propellant, the calculation formula of Q _penetrations of tank pipeline leakage is as follows:

Among them: C ₁ is the design margin factor; T _hot is the temperature outside the thermal insulation layer of the tank; T _cold is the temperature of the liquid low-temperature propellant inside the tank, and V _tank is the volume of the tank.

In the above-mentioned cost evaluation method for long-term in-orbit evaporation control of cryogenic propellant, the formula for calculating the leakage heat Q _parastitic of the refrigerator is as follows:

in, is the input power of the refrigerator, T _h o _t is the temperature outside the insulation layer of the tank; T _cold is the temperature of the liquid low-temperature propellant inside the tank; C ₁ is the design margin factor, and C″ ₂ is the shadow factor.

In the above cost evaluation method for long-term in-orbit evaporation control of low-temperature propellant, the formula for calculating the available cooling capacity Q _vapor of low-temperature propellant exhaust is as follows:

Among them, t is the on-orbit time, _{cp,T is the specific heat capacity of the propellant at the exhaust outlet pressure, T vapor_begin is} the exhaust outlet temperature, and T _{vapor_last} is the temperature after the exhaust available cold energy is used up.

In the above-mentioned cost evaluation method for long-term in-orbit evaporation control of low-temperature propellant, in the step (2), the evaporation of low-temperature propellant under different working conditions is obtained and evaporation rate The specific method is as follows:

In the above-mentioned cost evaluation method for long-term in-orbit evaporation control of cryogenic propellant, the weight increase caused by the introduction of a refrigerator in the step (3) Including the weight of the refrigerator Radiator weight Solar array weight Electronic equipment weight Pipe weight and cable weight

In the above cost evaluation method for long-term in-orbit evaporation control of cryogenic propellant, the weight of the refrigerator itself The calculation formula is as follows:

Where: T _c is the cold head temperature of the refrigerator.

In the above-mentioned cost estimation method for long-term in-orbit evaporation control of cryogenic propellant, the weight of the radiator The calculation formula is as follows:

Solar array weight The calculation formula is as follows:

Electronic equipment weight The calculation formula is as follows:

Pipe weight The calculation formula is as follows:

Cable weight The calculation formula is as follows:

in: input power for the refrigerator; is the weight of the refrigerator itself.

In the above cost evaluation method for long-term in-orbit evaporation control of cryogenic propellant, the input power of the refrigerator is The calculation formula is as follows:

In the above-mentioned cost evaluation method for long-term in-orbit evaporation control of cryogenic propellant, the step (3) also includes the weight of heat insulating material introduced under different working conditions under the same conditions with the corresponding evaporation Summation to get the system weight penalty under this condition Traverse the weight cost of the system under all operating conditions Find System Weight Costs the minimum value of .

In the above-mentioned cost evaluation method for long-term in-orbit evaporation control of cryogenic propellant, the weight of insulating material The calculation formula is as follows:

Where: ρ _m is the average areal density of the multi-layer thermal insulation material reflective screen; t _m is the thickness of the reflective screen; ρ _s is the average areal density of the multi-layer thermal insulation material spacer, t _s is the spacer thickness; is the interlayer density of the multi-layer thermal insulation material, N _s is the total number of layers of the multi-layer thermal insulation material, and A is the area of the multi-layer thermal insulation material.

Compared with the prior art, the present invention has the following beneficial effects:

(1) The present invention comprehensively considers the heat leakage of each component of the low-temperature propellant long-term in-orbit storage evaporation control system and the available cooling capacity of exhaust gas, and designs a cost evaluation method for in-orbit evaporation control. Firstly, the evaporation volume and evaporation rate of the long-term in-orbit storage system of cryogenic propellant are obtained, and then the weight cost brought by the evaporation control measures is obtained, and then the optimal design condition with the smallest weight cost is obtained, which is used to guide the cryogenic propellant in-orbit storage system. the design of.

(2) The present invention takes system efficiency indicators such as system light weight, low power, and achievability as optimization goals, establishes an engineering evaluation method, and can effectively carry out long-term on-orbit evaporation control system analysis of low-temperature propellants.

(3) The cost evaluation method for the long-term on-orbit evaporation control of the low-temperature propellant of the present invention has traversed all the on-orbit time, all the refrigeration capacity, all the thickness of the insulating material and all the propellant weights, etc., considering the factors comprehensively, greatly improving the The accuracy and reliability of the evaluation method.

(4) The cost evaluation method for long-term in-orbit evaporation control of low-temperature propellant of the present invention has the advantages of high reliability, wide coverage and high precision.

Description of drawings

FIG. 1 is a flowchart of a cost evaluation method for long-term in-orbit evaporation control of low-temperature propellant in an embodiment of the present invention.

Detailed ways

Below in conjunction with accompanying drawing and specific embodiment, the present invention is described in further detail:

The concrete realization steps of the cost evaluation method for on-orbit evaporation control of the present invention are as follows:

(1) Calculation method for the net heat leakage Q _loss of the evaporation control system for long-term in-orbit storage of cryogenic propellants:

According to the energy balance, the calculation of the net heat leakage of the system is shown in formula (1):

Q _loss =Q _MLI +Q _struts +Q _parastitic +Q _penetrations -Q _vapor -Q _cryocooler (1)

Among them: Q _MLI is the heat leakage of the thermal insulation material on the surface of the propellant tank; Q _struts is the heat leakage of the propellant tank support structure; Q _parastitic is the heat leakage of the _{refrigerator ;} The cryo-propellant exhaust can utilize the cooling capacity; Q _cryocooler represents the cooling capacity of the cryocooler.

The formula for calculating the heat leakage Q _MLI of the thermal insulation material on the surface of the propellant tank is shown in formula (2):

Among them, T _hot is the outside temperature of the thermal insulation layer of the tank, in K; T _cold is the temperature of the liquid low-temperature propellant inside the tank, in K; N _s is the total number of layers of multi-layer thermal insulation materials, for example, N _s is the value of 10 to 100.

The heat leakage Q _struts calculation of the propellant tank support structure is based on the thermal conductivity data of the support insulation structure (PODS) developed by NASA:

For the calculation formula of Q _struts of liquid oxygen propellant, see formula (3):

Among them, C ₁ is the design margin factor, for example, the value is 1 to 1.2, C ₂ is 0.44, M _tank is the weight of the cryogenic propellant tank, the unit is kg; M _propellant is the cryogenic propellant weight, the unit is kg.

For the calculation formula of Q _struts of liquid hydrogen propellant, see formula (4):

Wherein, C ₁ is a design margin factor, for example, it ranges from 1 to 1.2, and C' ₂ is 0.021.

The formula for calculating the heat leakage Q _penetrations of the tank pipeline is as follows

Among them, C1 is the design margin factor, for example, the value is 1 to 1.1, and V _tank is the volume of the tank.

The heat entering the system through the refrigerator when the refrigerator is not working is mainly based on the data of the AIRS refrigerator in the "Spacecraft ThermalControl Handbook". The formula for calculating the leakage heat Q _parastitic of the refrigerator is as follows:

Among them, C ₁ is the design margin factor, which ranges from 1 to 1.2, and C″ ₂ is the shadow factor (representing the proportion of the time the aircraft is in the shadow, and the refrigerator does not work when it is in the shadow area), Input power to the chiller.

The formula for calculating the available cooling capacity Q _vapor for the evaporative exhaust of low-temperature propellant is as follows:

in, is the low temperature propellant evaporation, t is the on-orbit time, and ranges from 1 to 500; c _{p, T} is the specific heat capacity of the propellant under the exhaust outlet pressure; T _{vapor_begin} is the exhaust outlet temperature, and T _{vapor_last} is the exhaust available. The temperature after the cooling capacity is used up.

The refrigerating capacity of the cryocooler is determined by its refrigerating capacity, here specifically refers to the refrigerating capacity Q _cryocooler of the cryocooler corresponding to the storage temperature of the propellant (saturation temperature), which ranges from 0 to 80.

(2) For the simultaneous equations (1) to (9), according to the corresponding latent heat of evaporation γ of the low-temperature propellant saturation temperature and the on-orbit working time t, the net heat leakage Q _loss and the low-temperature propellant evaporation under different operating conditions are obtained and evaporation rate i represents different working conditions, i=1, 2, ..., N, where N is the number of working conditions;

(3), system cost calculation method

Obtain the weight increase brought by the introduction of the refrigerator under different working conditions under the same conditions with the corresponding evaporation Summation to get the system weight penalty under this condition Traverse the weight cost of the system under all operating conditions Find System Weight Costs the minimum value of .

Weight gain due to introduction of chillers Including the weight of the refrigerator Radiator weight Solar array weight Electronic equipment weight Pipe weight and cable weight

which is:

According to the current performance of the cryogenic refrigerator, the weight of the refrigerator under different working conditions is given The calculation formula is as follows:

Where: T _c is the cold head temperature of the refrigerator.

Radiator weight The calculation formula is as follows:

Solar array weight The calculation formula is as follows:

Electronic equipment weight The calculation formula is as follows:

Pipe weight The calculation formula is as follows:

Cable weight The calculation formula is as follows:

in: input power for the refrigerator; is the weight of the refrigerator itself.

The input power of the refrigerator in the above formula Calculated as follows:

System weight penalty under this condition It is expressed as follows:

In addition, this step also includes the weight of the thermal insulation material introduced under different working conditions under the same conditions with the corresponding evaporation Summation to get the system weight penalty under this condition Traverse the weight cost of the system under all operating conditions Find System Weight Costs the minimum value of .

which is It can be expressed as follows:

The weight of the insulation material The calculation formula is as follows:

Where: ρ _m is the average areal density of the multi-layer thermal insulation material reflective screen; t _m is the thickness of the reflective screen; ρ _s is the average areal density of the multi-layer thermal insulation material spacer, t _s is the spacer thickness; is the interlayer density of the multi-layer thermal insulation material, N _s is the total number of layers of the multi-layer thermal insulation material, and A is the area of the multi-layer thermal insulation material.

The specific values in this embodiment are: Take 15～25layers/cm, ρ _m =0.00881kg/m ² ; t _m =0.0064mm; ρ _s =0.0073kg/m ² , t _s =0.13mm; N _s take 10～100, A is equal to the surface area of the tank .

Figure 1 is a flowchart of the cost evaluation method for long-term on-orbit evaporation control of low-temperature propellant in the embodiment of the present invention. In the embodiment of the present invention, the optimal working condition obtained according to the above method is: The rail time is more than 7 days. Compared with only passive heat insulation measures, the addition of active refrigerators has obvious technical advantages and the system cost is the smallest.

The above is only the best specific embodiment of the present invention, but the protection scope of the present invention is not limited to this. Substitutions should be covered within the protection scope of the present invention.

Contents that are not described in detail in the specification of the present invention belong to the well-known technology of those skilled in the art.

Claims (14)

1. A cost evaluation method for long-term on-track evaporation capacity control of a low-temperature propellant is characterized by comprising the following steps of: the method comprises the following steps:

(1) determining the net leakage heat Q of the low-temperature propellant in-orbit storage_loss；

(2) According to the net heat leakage Q_lossObtaining the evaporation capacity of the low-temperature propellant under different working conditions by the evaporation latent heat gamma corresponding to the saturation temperature of the low-temperature propellant and the on-orbit working time tAnd rate of evaporationi represents different working conditions, i is 1, 2, … …, N, wherein N is the number of working conditions;

(3) obtaining the weight increase brought by introducing the refrigerator under different working conditionsWill be in the same working conditionCorresponding amount of evaporationSumming to obtain the weight cost of the system under the working conditionTraversing system weight costs under all operating conditionsFinding system weight costMinimum value of (d);

(4) recording system weight costAnd taking the working condition corresponding to the minimum value as the optimal working condition.

2. The cost assessment method for long-term on-track evaporation rate control of a cryogenic propellant according to claim 1, wherein: determining the net leakage heat Q of the low-temperature propellant stored in the rail in the step (1)_lossThe specific method comprises the following steps:

Q_loss＝Q_MLI+Q_struts+Q_parastitic+Q_penetrations-Q_vapor-Q_cryocooler

wherein: q_MLIIndicating the heat leakage of the thermal insulation material on the surface of the propellant storage tank; q_strutsIndicating an amount of heat leakage from the propellant tank support structure; q_parastiticIndicating the heat leakage of the refrigerator; q_penetrationsIndicating the heat leakage of the storage tank pipeline; q_vaporIndicating the available cold energy for exhausting the low-temperature propellant; q_cryocoolerIndicating the refrigerating capacity of the refrigerator.

3. The cost assessment method for long-term on-track evaporation control of a cryogenic propellant according to claim 2, wherein: heat leakage quantity Q of heat insulating material on surface of propellant storage box_MLIThe calculation formula of (a) is as follows:

wherein, T_hotThe temperature of the outer side of the heat insulation layer of the storage tank; t is_coldThe temperature of the liquid low-temperature propellant in the storage tank is adopted;

N_sis the total number of the layers of the heat-insulating material.

4. The cost assessment method for long-term on-track evaporation control of a cryogenic propellant according to claim 2, wherein: heat leakage quantity Q of propellant storage box supporting structure_strutsThe calculation formula of (a) is as follows:

q for liquid oxygen propellants_struts：

Wherein: c₁To design a margin factor, C₂Is 0.44, M_tankThe weight of the low-temperature propellant storage tank; m_propellantIs the weight of the low-temperature propellant;

for liquid hydrogen pushQ of the injection_struts：

Wherein: c'₂Is 0.021; t is_hotThe temperature of the outer side of the heat insulation layer of the storage tank; t is_coldIs the temperature of the liquid cryogenic propellant inside the tank.

5. The cost assessment method for long-term on-track evaporation control of a cryogenic propellant according to claim 2, wherein: heat leakage Q of storage tank pipeline_penetrationsThe calculation formula of (a) is as follows:

wherein: c₁Designing a margin factor; t is_hotThe temperature of the outer side of the heat insulation layer of the storage tank; t is_coldIs the temperature, V, of the liquid cryogenic propellant inside the tank_tankIs the tank volume.

6. The cost assessment method for long-term on-track evaporation control of a cryogenic propellant according to claim 2, wherein: heat leakage quantity Q of refrigerator_parastiticThe calculation formula of (a) is as follows:

wherein,for input of power to the refrigerator, T_hotThe temperature of the outer side of the heat insulation layer of the storage tank; t is_coldThe temperature of the liquid low-temperature propellant in the storage tank is adopted; c₁To design a margin factor, C₂"is a shading factor.

7. The cost assessment method for long-term on-track evaporation control of a cryogenic propellant according to claim 2, wherein: cold quantity Q capable of being utilized by low-temperature propellant exhaust_vaporThe calculation formula of (a) is as follows:

wherein t is the on-track time, c_p,TSpecific heat capacity, T, of propellant at exhaust outlet pressure_{vapor_begin}Is the exhaust outlet temperature, T_{vapor_last}The temperature after the cold has been used up can be utilized for the exhaust.

8. The cost evaluation method for long-term on-track evaporation capacity control of a low-temperature propellant according to any one of claims 1 to 7, wherein: the evaporation capacity of the low-temperature propellant under different working conditions is obtained in the step (2)And rate of evaporationThe specific method comprises the following steps:

9. the cost evaluation method for long-term on-track evaporation capacity control of a low-temperature propellant according to any one of claims 1 to 7, wherein: the steps areWeight increase due to introduction of the refrigerator in step (3)Including the weight of the refrigerator itselfRadiator weightSolar array weightWeight of electronic equipmentWeight of pipelineAnd cable weight

10. The cost assessment method for long-term on-track evaporation rate control of a cryogenic propellant according to claim 9, wherein: self weight of refrigeratorThe calculation formula of (a) is as follows:

wherein: t is_cIs the cold head temperature of the refrigerator; q_cryocoolerIndicating the refrigerating capacity of the refrigerator.

11. The cost assessment method for long-term on-track evaporation rate control of a cryogenic propellant according to claim 9, wherein:

radiator weightThe calculation formula of (a) is as follows:

solar array weightThe calculation formula of (a) is as follows:

weight of electronic equipmentThe calculation formula of (a) is as follows:

weight of pipelineThe calculation formula of (a) is as follows:

weight of cableThe calculation formula of (a) is as follows:

wherein:inputting power to the refrigerator;the weight of the refrigerator itself.

12. The cost assessment method for long-term on-track boil-off control of a cryogenic propellant according to claim 11, wherein: input power of the refrigeratorThe calculation formula of (a) is as follows:

wherein: q_cryocoolerIndicating the refrigerating capacity of the refrigerating machine; t is_hotThe temperature of the outer side of the heat insulation layer of the storage tank; t is_cIs the cold head temperature of the refrigerator.

13. The cost assessment method for long-term on-track evaporation rate control of a cryogenic propellant according to claim 1, wherein: the step (3) also comprises the weight of heat insulation materials introduced under different working conditionsWill be in the same working conditionCorresponding amount of evaporationSumming to obtain the weight cost of the system under the working conditionTraversing system weight costs under all operating conditionsFinding system weight costIs measured.

14. The cost assessment method for long-term on-track evaporation control of a cryogenic propellant according to claim 13, wherein: weight of heat insulating materialThe calculation formula of (a) is as follows:

wherein: rho_mThe average surface density of the multi-layer heat insulation material reflecting screen; t is t_mIs the thickness of the reflecting screen; rho_sIs the average areal density, t, of the multi-layer insulation spacer_sIs the spacer thickness;is the interlayer density of the multi-layer heat insulating material, N_sThe total number of the layers of the multi-layer heat insulation material is shown, and A is the area of the multi-layer heat insulation material.