A method for determining the pressure of building pressure by mixing gas with starting medium and a building pressure system

Abstract

The present invention provides a method for determining the pressure of a gas mixture of fuel gas and starting medium during pressure build-up and a pressure build-up system. The method includes: considering the gas mixture of fuel gas and starting medium as a homogeneous medium and determining the pressure build-up P1 at this time; regarding the gas mixture as an independent medium, introducing the flow area distribution coefficient α of the fuel gas, then the flow area distribution coefficient of the starting medium is 1-α, and determining the pressure build-up P2 at this time; introducing the mixing coefficient β to represent the mixing degree, and the pressure of the pressure build-up of the mixture is: P mix =β·P1+(1-β)·P2, where 0 < β < 1. The pressure build-up system includes a gas cylinder, a pressure reducing valve, a throttle ring, a stop valve, a check valve, a mixing chamber, and a pressure build-up throat connected by pipelines. When a liquid oxygen-methane gas generator provided by the present invention conducts a hot test under the condition that the flow rate of the starting medium and the fuel gas are of the same order of magnitude, the fuel gas and starting medium mixing pressure build-up system, the system design method, and the method for determining the mixing pressure build-up ensure the accurate control of the flow rate of the starting medium and the accurate determination of the pressure build-up during the hot test of the gas generator.

Description

Technical Field

[0001] The present invention belongs to the technical field of hot tests of gas generators, and particularly relates to a method for determining the pressure build-up of the mixing of liquid oxygen-methane gas and starting medium and a pressure build-up system. Background Art

[0002] During the steady-state operation of a liquid rocket engine, the turbine pump speed is tens of thousands of revolutions per minute. The process of the turbine pump speed rising from 0 rev / min to the rated condition is called the starting process. According to whether there is external energy assistance, the starting schemes are divided into two categories: self-starting and forced starting. When the forced starting scheme is adopted, if the direct forced starting scheme of the main turbine is used and the front of the turbine stator is not divided into a starting medium cavity and a gas cavity, the starting medium for starting (such as inert gases like nitrogen and helium or gunpowder gas) will build pressure in front of the main turbine, and the pressure build-up generally ranges from 0.3 MPa to 5 MPa. Since the front of the main turbine is the outlet of the gas generator, the ignition process of the gas generator will then be carried out under a relatively large back pressure condition, and there will be differences in the filling characteristics of the medium, ignition time, required ignition energy, etc.

[0003] Before the overall engine test, the gas generator is generally tested separately. At this time, the test should be carried out according to the back pressure condition under the engine starting state, and generally, the flow of starting medium such as nitrogen is used to simulate the back pressure condition. When simulating a relatively low back pressure condition, or when the self-pressure build-up of the gas generator is relatively low, the pressure build-up after the mixing of the starting medium such as nitrogen and the gas (driving medium) is not considered. Generally, only considering the medium with a larger flow rate can also obtain better accuracy. When the flow rate of the starting medium such as nitrogen is of the same order of magnitude as the gas flow rate (the small flow rate accounts for more than 20% of the large flow rate), only considering the pressure build-up of one medium will bring a large deviation. Summary of the Invention

[0004] In order to overcome the deficiencies in the prior art, the inventor of the present invention has conducted intensive research and provided a pressure build-up system for the mixing of liquid oxygen-methane gas and starting medium such as inert gas, a system design method, and a determination method for the pressure build-up of the mixing when the flow rate of the starting medium and the gas flow rate are of the same order of magnitude during the hot test of the liquid oxygen-methane gas generator, so as to ensure the accurate control of the starting medium flow rate and the accurate determination of the pressure build-up during the hot test of the gas generator.

[0005] The technical solution provided by the present invention is as follows:

[0006] In a first aspect, a method for determining the pressure build-up of the mixing of liquid oxygen-methane gas and starting medium includes:

[0007] Considering the mixed gas of the gas and the starting medium as a homogeneous medium, and determining the pressure build-up at this time as P 1 ;

[0008] Consider the mixed gas as an independent medium, introduce the flow area distribution coefficient of the gas, and the flow area distribution coefficient of the starting medium is 1-α. The pressure build-up at this time is determined to be P 2 , where 0<α<1;

[0009] The mixing coefficient β is introduced to represent the mixing degree, and the pressure of mixing pressure is: P mix =β·P 1 +(1-β)·P 2 , where 0<β<1.

[0010] In the second aspect, a system for building pressure by mixing liquid oxygen and methane gas with a starting medium comprises a gas cylinder, a pressure reducing valve, a throttle ring, a stop valve, a one-way valve, a mixing chamber and a pressure building throat; the gas cylinder contains a starting medium and is connected to the mixing chamber through a pipeline for conveying the starting medium, and a pressure reducing valve, a throttle ring, a stop valve and a one-way valve are sequentially installed on the pipeline from the gas cylinder end to the mixing chamber end; the mixing chamber is connected to the outlet pipeline of the gas generator to convey the mixed gas to the pressure building throat, and the pressure building throat is used to simulate the working state of the gas generator to ensure that the pressure in the mixing chamber meets the test assessment requirements under a certain starting medium and gas flow rate, and the mixed gas is output to the turbine pump after passing through the pressure building throat.

[0011] In a third aspect, a design method for a pressure building system for mixing liquid oxygen, methane gas and starting medium includes:

[0012] S1, according to the gas generator pressure P under stable working conditions g , gas flow qm g , and the thermodynamic parameter gas constant R g , gas temperature T g , isentropic index k of gas g , determine the throat area A of the pressure-building throat 7 喉 ;

[0013]

[0014] S2, according to the throat area A of the pressure-building throat 喉 , Ignition back pressure P of the gas generator to be assessed i , gas constant R i , starting medium temperature T i , isentropic index k of the starting medium i , determine the required starting medium flow rate qm i ;

[0015]

[0016] S3. Adopt the method for determining the pressure of mixing and building pressure to determine the operating parameters when the gas and the starting medium build pressure together, which is used to check the structural safety factor and the influence on the operating parameters of the gas generator;

[0017] S4. Determine the outlet pressure P of the pressure reducing valve according to the pressure of mixing and building pressure determined in step S3 减 ;

[0018] According to the required flow rate of the starting medium determined in step S2, refer to the single-medium pressure building formula to determine the flow area A at the throttle ring 节 , and determine the aperture of the throttle ring according to the flow area A 节 ;

[0019]

[0020] S5. Select the pressure of the gas cylinder according to the outlet pressure of the pressure reducing valve, and determine the required gas cylinder volume according to the working time.

[0021] According to a method for determining the pressure of mixing and building pressure of liquid oxygen-methane gas and a starting medium and a pressure building system provided by the present invention, the following beneficial effects are achieved:

[0022] (1) A method for determining the pressure of mixing and building pressure of liquid oxygen-methane gas and a starting medium provided by the present invention can accurately calculate the pressure of mixing and building pressure of the gas and the starting medium, and successfully ensures the ignition test assessment of the gas generator under high backpressure conditions;

[0023] (2) A method for determining the pressure of mixing and building pressure of liquid oxygen-methane gas and a starting medium and a pressure building system provided by the present invention can evaluate in advance the influence of mixing and building pressure on the structural pressure bearing and the operating conditions of the gas generator;

[0024] (3) A design method for a system for mixing and building pressure of liquid oxygen-methane gas and a starting medium provided by the present invention can accurately design the flow path configuration of the starting medium. Description of the Drawings

[0025] Figure 1 is a schematic structural diagram of a system for mixing and building pressure of liquid oxygen-methane gas and a starting medium provided by the present invention.

[0026] Description of the Reference Numerals in the Drawings

[0027] 1 - gas cylinder; 2 - pressure reducing valve; 3 - throttle ring; 4 - stop valve; 5 - check valve; 6 - mixing cavity; 7 - pressure building throat; 8 - sensor. Detailed Embodiments

[0028] The present invention will be described in detail below, and the features and advantages of the present invention will become clearer and more definite with these descriptions.

[0029] The term "exemplary" as used herein means "serving as an example, embodiment, or illustration". Any embodiment illustrated herein as "exemplary" should not necessarily be construed as superior or better than other embodiments. Although various aspects of the embodiments are shown in the drawings, the drawings are not necessarily drawn to scale unless otherwise specified.

[0030] According to a first aspect of the present invention, there is provided a method for determining the pressure of a liquid oxygen-methane fuel gas mixed with a starting medium to build pressure. The liquid oxygen-methane fuel gas and the starting medium are mixed and pressurized before the turbopump, and the method includes the following steps:

[0031] S1. Consider the mixture of the fuel gas and the starting medium as a homogeneous medium, and the pressure at this time is P 1 , P 1 . The determination process of is as follows:

[0032] S1.1. The isentropic exponents of the fuel gas and the starting medium (k g and k i respectively) are weighted and averaged by mass flow rate to obtain the isentropic exponent k of the mixture 1 ;

[0033]

[0034] In the formula, qm g is the fuel gas flow rate; qm i is the starting medium flow rate.

[0035] S1.2. The molar masses of the fuel gas and the starting medium (M g and M i respectively) are weighted and averaged by mass flow rate to obtain the molar mass M of the mixture 1 ;

[0036]

[0037] S1.3. The specific heat at constant pressure of the fuel gas, the starting medium, and the mixture are determined respectively using the isentropic exponent and the molar mass;

[0038]

[0039]

[0040] Among them, Cp g is the specific heat at constant pressure of the fuel gas; Cp i is the specific heat at constant pressure of the starting medium; Cp 1 is the specific heat at constant pressure of the mixture;

[0041] S1.4. According to the law of conservation of energy, the temperature T of the mixture is determined 1 ;

[0042] Cp1 ·qm 1 ·T 1 =Cp g ·qm g ·T g +Cp i ·qm i ·T i

[0043]

[0044] S1.5, the isentropic index k of the mixed gas 1 , molar mass M 1 , mixed gas temperature T 1 Substitute the parameters into the single medium pressure building formula to obtain the pressure building P 1 .

[0045]

[0046] Where A is the flow area.

[0047] S2, the mixed gas is identified as an independent medium, and the flow area distribution coefficient of the introduced gas is α, 0<α<1, then the flow area distribution coefficient of the starting medium is (1-α), and the pressure build-up is P 2 , P 2 The determination process is:

[0048] The gas pressure building equation is:

[0049]

[0050] The starting medium pressure building equation is:

[0051]

[0052] By combining the above equations, the flow area distribution coefficient α and the pressure build-up P can be determined. 2 .

[0053] S3, the actual pressure build-up is often between P 1 and P 2 The mixing coefficient β is introduced between 0 and 1, which represents the mixing degree. The gas and the starting medium are mixed in the mixing chamber. When the mixing position of the gas and the starting medium in the mixing chamber is located at or near the outlet of the mixing chamber, β is 0; when the mixing position of the gas and the starting medium in the mixing chamber is close to the outlet of the mixing chamber, β takes a smaller value; when it is far from the outlet of the mixing chamber, β takes a larger value; the final mixing pressure is: P mix =β·P 1 +(1-β)·P 2 .

[0054] According to a second aspect of the present invention, a liquid oxygen methane gas and starting medium mixing and pressure building system is provided, including a gas cylinder 1, a pressure reducing valve 2, a throttle orifice 3, a stop valve 4, a check valve 5, a mixing chamber 6, and a pressure building throat 7; the starting medium is contained in the gas cylinder 1, and is connected to the mixing chamber 6 through a pipeline for transporting the starting medium. A pressure reducing valve 2, a throttle orifice 3, a stop valve 4, and a check valve 5 are sequentially installed on the pipeline from the gas cylinder end to the mixing chamber end; the mixing chamber 6 is communicated with the outlet pipeline of the gas generator, and the mixed gas is transported to the pressure building throat 7. The pressure building throat 7 is used to simulate the working state of the gas generator, ensuring that the pressure in the mixing chamber 6 meets the test assessment requirements under a certain starting medium and gas flow rate. The mixed gas is output to the turbopump after passing through the pressure building throat 7. Preferably, a pressure sensor and / or a temperature sensor are arranged in the pipeline between the pressure reducing valve 2 and the throttle orifice 3.

[0055] In a preferred embodiment, the pressure reducing valve satisfies that the outlet pressure of the pressure reducing valve reaches more than 1.3 times of the mixing and pressure building pressure, that is, P 减 ≥1.3P mix .

[0056] In a preferred embodiment, the aperture of the throttle orifice is determined by the flow area of the throttle orifice. The flow area A 节 of the throttle orifice satisfies the following formula:

[0057] In a preferred embodiment, the throat area A 喉 of the pressure building throat 7 is determined by the pressure P g of the gas generator, the gas flow rate qm g , and the thermodynamic parameters (gas constant R g , temperature T g , isentropic exponent k g ) under stable operating conditions:

[0058]

[0059] According to a third aspect of the present invention, a design method for a liquid oxygen methane gas and starting medium mixing and pressure building system is provided, including:

[0060] S1: Determine the throat area A g of the pressure building throat 7 according to the pressure P g of the gas generator, the gas flow rate qm g , and the thermodynamic parameters (gas constant R g , temperature T g , isentropic exponent k 喉 under stable operating conditions;

[0061]

[0062] Gas constant R g and R i are both 8.314 J / mol·K, and their meanings are the same.

[0063] S2: Determine the flow rate qm of the required starting medium according to the throat area A of the pressure - building throat 7 喉 , the ignition back - pressure P of the gas generator to be tested i , and the thermodynamic parameters (gas constant R i , temperature T i , isentropic exponent k i ); i ;

[0064]

[0065] S3: Adopt the method for determining the mixing and pressure - building pressure to determine the operating parameters when the gas and the starting medium build pressure together (including the mixing and pressure - building pressure P 1 when the mixed gas is regarded as a homogeneous medium, the mixing and pressure - building pressure P 2 when the mixed gas is regarded as an independent medium, and the actual mixing and pressure - building pressure P mix ), which are used to check the structural safety factor, the influence on the operating parameters of the gas generator (such as propellant flow rate, mixing ratio, temperature), etc.; among them, the mixing and pressure - building pressures in the three cases of the operating parameters are obtained through the method for determining the mixing and pressure - building pressure described in the first aspect;

[0066] S4: Determine the outlet pressure P of the pressure - reducing valve 2 according to the mixing and pressure - building pressure determined in step S3 减 ; preferably, the outlet pressure P of the pressure - reducing valve 2 减 takes more than 1.3 times of the mixing and pressure - building pressure, that is, P 减 ≥1.3P mix ;

[0067] Determine the flow - through area A at the throttle ring 3 according to the required flow rate of the starting medium determined in step S2, referring to the single - medium pressure - building formula 节 , and determine the aperture of the throttle ring 3 according to the flow - through area A 节 . The throttle ring 3 can be used after calibrating the flow coefficient;

[0068]

[0069] Set a pressure sensor in front of the throttle ring 3 to ensure that the pressure is the designed value. At the same time, a temperature sensor can also be set to obtain more accurate inlet medium parameters of the throttle ring.

[0070] S5: Select the pressure of the gas cylinder 1 according to the outlet pressure of the pressure - reducing valve 2, and determine the required gas cylinder volume according to the working time.

[0071] Embodiment

[0072] During a certain test, the mass flow rate of the inert gas (N 2 ) was: 1 kg / s, and the mass flow rate of the fuel gas was: 0.85 kg / s. During this test, the inlet of the inert gas was adjacent to the outlet of the mixing chamber, and the mixing position of the inert gas and the fuel gas was equivalent to the outlet of the mixing chamber. The mixing coefficient β was selected as 0, and the calculation results are shown in Table 1 below.

[0073] Table 1

[0074] Status Test value Calculated value Deviation Separate gas pressure build-up 3.71 3.61 -2.7％ Gas and starting medium mixing pressure build-up 6.12 6.08 -0.7％

[0075] Through the above calculations and test system design, the ignition test assessment of a certain gas generator under high backpressure conditions was successfully ensured.

[0076] The present invention has been described in detail above in combination with specific embodiments and exemplary examples, but these descriptions should not be construed as limiting the present invention. Those skilled in the art understand that without departing from the spirit and scope of the present invention, various equivalent substitutions, modifications or improvements can be made to the technical solutions and their implementation manners of the present invention, and all of these fall within the scope of the present invention. The protection scope of the present invention is subject to the appended claims.

[0077] The content not described in detail in the specification of the present invention belongs to the well-known technology of those skilled in the art.

Claims

1. A method for determining the pressure build-up of the admixture of liquid oxygen methane gas and starting medium, characterized in that, it includes: Considering the mixture of fuel gas and starting medium as a homogeneous medium, determine the pressure build-up to be P at this time 1 ; Regarding the blended gas as an independent medium and introducing the flow area distribution coefficient α of the fuel gas, the flow area distribution coefficient of the starting medium is 1 - α, and determine the pressure build-up at this time as P 2 , where 0 < α < 1; The blending coefficient β is introduced to represent the degree of blending, and the pressure of the blended pressure building is: P mix = β·P 1 +(1 - β)·P 2 , where 0 < β < 1.

2. The method for determining the pressure build-up of the admixture of liquid oxygen methane gas and starting medium according to claim 1, characterized in that, The described P 1 The determination process includes the following steps: S1.1, obtaining the isentropic exponent k of the mixture gas by weighted average of the isentropic exponents of the fuel gas and the starting medium according to the mass flow rate 1 ; Where, qm g is the gas flow rate; qm i is the starting medium flow rate; k g is the isentropic exponent of the gas; k i is the isentropic exponent of the starting medium; S1.2, obtaining the molar mass M of the mixture gas by weighted average of the molar masses of the fuel gas and the starting medium according to the mass flow rate 1 ; where M g is the molar mass of the fuel gas; M i is the molar mass of the starting medium; S1.3, respectively use the isentropic exponent and molar mass to determine the specific heat at constant pressure of the gas, starting medium and admixture gas; Among them, Cp g is the specific heat at constant pressure of the fuel gas; Cp i is the specific heat at constant pressure of the starting medium; Cp 1 is the specific heat at constant pressure of the premixed gas; S1.

4. Determine the temperature T of the blended gas according to the law of conservation of energy 1 ; where, T i is the temperature of the starting medium, and T g is the temperature of the fuel gas; S1.5, substitute the isentropic exponent k 1 , molar mass M 1 , temperature T of the blended gas 1 and other parameters into the single-medium pressure-building formula to obtain the pressure P 1 ; In the formula, A is the flow area.

3. The method for determining the pressure build-up of the admixture of liquid oxygen methane gas and starting medium according to claim 2, characterized in that, The described P 2 The determination process includes the following steps: The gas pressure build-up equation is: The starting medium pressure build-up equation is: Combine the above equations to determine the flow area distribution coefficient α and the pressure build-up P 2 .

4. The method for determining the pressure build-up of the admixture of liquid oxygen methane gas and starting medium according to claim 1, characterized in that, The determination rule of the admixture coefficient β is: The admixture of gas and starting medium is carried out in the admixture chamber. When the admixture position of the gas and starting medium in the admixture chamber is at or near the outlet of the admixture chamber, β is taken as 0; when the admixture position of the gas and starting medium in the admixture chamber is closer to the outlet of the admixture chamber, β is taken as a smaller value, and when it is farther from the outlet of the admixture chamber, β is taken as a larger value.

5. A liquid oxygen methane gas and starting medium admixture pressure build-up system, characterized in that, The invention comprises a gas cylinder (1), a pressure reducing valve (2), a throttle ring (3), a stop valve (4), a check valve (5), a mixing chamber (6) and a pressure building throat (7); the gas cylinder (1) contains a starting medium and is connected to the mixing chamber (6) through a pipeline for conveying the starting medium; the pressure reducing valve (2), the throttle ring (3), the stop valve (4) and the check valve (5) are sequentially installed on the pipeline from the gas cylinder end to the mixing chamber end; the mixing chamber (6) is connected to the outlet pipeline of the gas generator to convey the mixed gas to the pressure building throat (7); the pressure building throat (7) is used to simulate the working state of the gas generator to ensure that the pressure in the mixing chamber (6) meets the test assessment requirements under the starting medium and gas flow rate, and the mixed gas is output to the turbine pump after passing through the pressure building throat (7); the pressure reducing valve satisfies that the pressure at the outlet of the pressure reducing valve reaches more than 1.3 times the mixing pressure building pressure, P 减 ≥1.3P mix .

6. The liquid oxygen methane gas and starting medium admixture pressure build-up system according to claim 5, characterized in that, The flow area A of the throttle ring 节 satisfies the following formula: Among them, P 减 is the outlet pressure of the pressure reducing valve; qm i is the starting medium flow rate; k i is the isentropic exponent of the starting medium; R i is the gas constant R i ; T i is the temperature of the starting medium.

7. The liquid oxygen methane gas and starting medium admixture pressure build-up system according to claim 5, characterized in that, The throat area A of the pressure-building throat 喉 satisfies the following formula: Among them, P g is the pressure of the gas generator under stable operating conditions; qm g is the gas flow rate; R g is the gas constant; T g is the gas temperature; k g is the isentropic exponent of the gas.

8. The liquid oxygen methane gas and starting medium admixture pressure build-up system according to claim 5, characterized in that, A pressure sensor and / or a temperature sensor are arranged in the pipeline between the pressure reducing valve and the throttle ring.

9. A design method for a liquid oxygen methane gas and starting medium admixture pressure build-up system, characterized in that, it includes: S1. Determine the throat area A of the pressure - building throat according to the gas generator pressure P g under steady - state conditions, the gas flow rate qm g , the thermodynamic parameter gas constant R g , the gas temperature T g , and the isentropic exponent k of the gas g ; 喉 ​ S2, determine the required flow rate qm of the starting medium according to the throat area A of the pressure-building throat 喉 , the ignition back pressure P of the gas generator to be tested i , the gas constant R i , the temperature T of the starting medium i , the isentropic exponent k of the starting medium i , and i ; S3, adopt the pressure build-up determination method of the admixture to determine the working condition parameters when the gas and the starting medium build up pressure together, so as to check the structural safety factor and the influence on the working condition parameters of the gas generator; S4. Determine the outlet pressure P of the pressure reducing valve according to the blending and pressure building pressure determined in step S3 减 ; According to the required starting medium flow rate determined in step S2, determine the flow area A at the throttle circle with reference to the single-medium pressure building formula 节 , according to the flow area A 节 determine the aperture of the throttle circle; S5, select the pressure of the gas cylinder according to the outlet pressure of the pressure reducing valve, and determine the required gas cylinder volume according to the working time.

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