CN114580142A - Method for sucking mass flow rate in active injection high-mode test of solid rocket engine - Google Patents
Method for sucking mass flow rate in active injection high-mode test of solid rocket engine Download PDFInfo
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Abstract
The invention relates to the field of solid rocket engines, in particular to a mass flow rate suction method for an active-injection high-mode test of a solid rocket engine. The method comprises the following steps: establishing a two-dimensional infinite slit suction mass flow rate calculation model; obtaining a leading edge sweepback suction mass flow rate through the circular hole suction mass flow rate model; deducing a pumping choking critical condition, and determining a choking pressure ratio according to an isentropic relation when wave front and wave rear Mach numbers are determined; and (4) verifying a suction mass flow rate model, verifying the effectiveness of the model through FLUENT numerical simulation, calculating the subsonic front edge as a supersonic front edge, taking the area in the model as the area of a circular hole, and comparing and verifying through the model and a numerical simulation result. The invention is not only suitable for circular hole suction, but also suitable for slit without sweepback angle and sweepback long slit suction meeting supersonic velocity front edge condition; the calculation method is convenient and high in precision.
Description
Technical Field
The invention relates to the field of solid rocket engines, in particular to a two-stage active injection system for a high-modulus test of a solid rocket engine.
Background
The development of a missile defense system provides strict requirements for the penetration capacity of a remote missile, a thrust vector technology such as a ball-and-socket spray pipe and a ball-and-socket spray pipe is adopted to become a trend of solid rocket engine design, the inlet end of a diffuser is very large due to the swing of the spray pipe, the pressure is low, a high-mode test run on the solid rocket engine gradually develops from single-stage injection to a second-stage injection system, and a suction system is usually designed for the high-mode test active injection system for effective injection and prevention of backflow.
At present, the most similar suction flow model to the present invention is a single-hole supersonic suction flow model established based on a CFD numerical simulation result by Bunnag and based on the prandtl-meier dilatational wave theory, assuming that the suction flow completely passes through the lower half section of the obstacle shock wave, according to the observed typical flow characteristics of the suction hole, including shock wave separation distance, shear layer, obstacle shock wave position, etc. The physical concept of the model is clear, but many parameters need to be determined, particularly the shock wave separation distance needs to be calculated iteratively, and the engineering practical value is effective.
The existing supersonic velocity suction mass flow rate model can be basically divided into two types, one type is based on the existing experimental data, and a suction flow coefficient is obtained according to the fitting of parameters such as Mach number, pressure ratio and the like; the other is a semi-empirical model, partial parameters of the pumping mass flow are obtained according to the theory of the shock wave and the expansion wave of the supersonic compressible flow, and other partial parameters are given through experience or corrected by introducing other parameters according to the deviation from the experimental result. The calculation accuracy of the existing suction mass flow rate model needs to be improved, and the engineering application range is limited.
Disclosure of Invention
Technical problems to be solved by the invention
The invention provides a method for sucking mass flow rate in an active injection high-mode test of a solid rocket engine, which aims to solve the problems of low calculation precision, limited engineering application range and the like of the existing sucking mass flow rate model.
Technical scheme adopted by the invention for solving technical problem
The invention discloses a calculation method for calculating the suction mass flow rate of a circular hole according to the Plantt-Meyer expansion wave theory, the supersonic velocity choking theory and the polygonal approximation circular hole progressive technology.
Advantageous effects obtained by the present invention
According to the Mach number of the flow channel, the critical pressure ratio of suction congestion is calculated, and the working pressure boundary of a suction system is determined; the invention is not only suitable for circular hole suction, but also suitable for slit without sweepback angle and sweepback long slit suction meeting supersonic velocity front edge condition; according to the pressure parameters of the flow channel and the suction cavity, the suction mass flow rate can be directly calculated according to the suction model, and the suction model can also reflect the strength of the flow parameters influencing the suction mass flow rate; the calculation method is convenient and high in precision.
Drawings
FIG. 1: a schematic diagram of a local flow field structure of the suction hole;
FIG. 2: supersonic leading edge suction;
FIG. 3: a slit with a sweep angle alpha;
FIG. 4: the circle inscribed polygon approaches the round hole;
FIG. 5: sucking a choking model at supersonic speed;
FIG. 6: and (4) the evolution law of the flow coefficient of different polygons.
Detailed Description
The technical scheme of the invention is to invent a calculation mode for calculating the suction mass flow rate of the circular hole according to the Plantt-Meier dilatational wave theory, the supersonic velocity choking theory and the polygonal approximation circular hole progressive technology.
In order to make the objects, features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in detail below. It is obvious that the described embodiments are only some, not all embodiments of the proposed solution. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The two-dimensional infinite long slit suction mass flow rate calculation model has a two-dimensional infinite long slit aperture D, flow field structures such as expansion waves and barrier shock waves are shown in figure 1, and the basic assumption for establishing the two-dimensional infinite long slit supersonic velocity suction model is as follows:
(1) the front edge of the suction hole is a disturbance point of the supersonic flow field to generate an expansion wave, the disturbance is transmitted along the direction of the expansion wave, and a streamline after the expansion wave is a straight line, so that no pressure difference exists in the direction vertical to the streamline, and the pressure difference is equal to the back pressure behind the suction hole.
(2) Suction is a pressure driven phenomenon, the suction flow rate being primarily dependent on the back pressure, which in turn varies the suction mass flow rate by varying the angle of deflection of the air flow at the suction orifice.
(3) The depth L of the suction hole is very small compared to the hole diameter D, and the flat plate is regarded as being free of thickness, i.e., L is 0. The incoming flow conditions are known as Mach number M1, pressure P1 and temperature T1, while the back pressure P2 at the suction orifice is known, and γ is the gas specific heat ratio. Determining the physical quantities M2, T2, p at the suction orifice inlet from the isentropic flow relationship2As shown in the schematic diagram of the structure of the suction hole local flow field in fig. 1.
According to the theory of supersonic velocity isentropic, the Mach number, the density and the temperature after the wave are respectively
The streamline after the expansion wave in figure 1 is a straight line, for a certain suction hole dimension L, a dimension Leff is corresponding to the last expansion wave, all the gas in the dimension enters the suction hole, and if the Mach angle between the last expansion wave and the streamline after the wave is mu 2, the mass flow rate of suction is provided
Theta is the flow line deflection angle, given by the Prandtl-Meyer relationship
θ＝υ(M2)-υ(M1) (5)
The circular hole suction mass flow rate model is popularized to establish the circular hole suction mass flow rate model by the two-dimensional infinite slit suction model. For a certain incoming flow mach number M1, the suction hole leading edge is divided into a subsonic leading edge and a supersonic leading edge, which is shown in fig. 2. The suction chamber backpressure disturbances do not affect the supersonic leading edge physical quantity, but have some effect on the subsonic leading edge, and this difference is the root cause for the difference in the subsonic/supersonic suction flow rates.
Now, considering the case of a sweep angle α, as shown in fig. 3, where the sweep angle α is a, for a slit of a supersonic swept leading edge, disturbance is limited in the mach cone, physical quantity of the supersonic leading edge is not affected, the incoming flow still expands according to the P-M expansion wave theory, the velocity after expansion is decomposed into a velocity V2t along the leading edge and a velocity V2n perpendicular to the leading edge, the flow direction length is L, and for the flow direction width W, the mass flow rate is L
Wherein
V2n＝V2sinα (7)
Obtaining leading edge sweep suction mass flow rate
Wherein the sweepback suction area A is LWsweepsin α, whereby the mass flow rate is further converted into
Under the condition of a supersonic front edge, the suction mass flow rate is independent of a backswept angle and only related to a suction area, namely a supersonic suction area law, which is an external expression that the back pressure of a suction cavity does not influence the inflow condition of the supersonic front edge, and is increased by a factor sin theta compared with the mass flow rate in a spray pipe, wherein the sin theta is dependent on the inflow Mach number and the ratio of the back pressure of the suction cavity to the inflow static pressure.
The curvature of the front edge of the circular hole is continuously changed, is equivalent to infinite deformation in geometry, and is provided with a supersonic front edge and a subsonic front edge which correspond to different suction mechanisms. In order to simplify the problem, the circular holes are approximately replaced by circular holes inscribed with triangles, quadrangles, pentagons and hexagons, continuously-changed front edges are converted into superposition of front edges with different curvatures, as shown in figure 4 that the polygons inscribed in the circles approach the circular holes, circular hole suction is converted into polygon suction, and a circular hole suction model is established by applying an ultrasonic suction area law. The polygonal suction mass flow rate is independent of the sweep angle below the supersonic leading edge, and depends only on the suction area, so the circular orifice suction mass flow rate expression is the same as the supersonic leading edge slit.
On the outer side of the circular hole, a part of subsonic front edge exists, pressure disturbance of the suction cavity can be spread into the Mach cone on the upper edge of the suction hole, so that the assumption of uniform incoming flow of the supersonic suction area rate is not satisfied, and errors can be caused. Since the perturbations in the mach cone are very weak and the subsonic front occupies only a small fraction, for an incoming mach number M1 of 2.0, the subsonic front occupies one third, while for higher mach numbers the ratio of subsonic front is smaller and negligible.
The critical condition of congestion is pumped, the congestion is the reaction that supersonic disturbance can not propagate upstream, and the condition for determining congestion occurrence is very key and has wide application. The suction mass flow rate increases gradually with decreasing back pressure for a given static pressure, static temperature and mach number, and does not decrease with decreasing back pressure when the back pressure decreases to a certain extent, a condition known as suction choking, which is a typical operating condition of a suction system. The condition for occurrence of congestion can be deduced according to the P-M dilatational wave theory. For certain conditions of incoming flow Mach number M1 and static pressure P1, mu 1 and mu 2 are Mach angles corresponding to a first expansion wave and a last expansion wave respectively, and an included angle between the two expansion waves is
As shown in the supersonic suction congestion model of fig. 5.
According to the supersonic flow theory
According to the geometric relationship of FIG. 6, the expansion fan angle is
When the angle of the expansion fan
When the Mach angle is equal to the incoming flow Mach angle mu 1
The last expansion wave is parallel to the inlet of the suction hole, the downstream disturbance of the suction hole cannot be propagated upstream under the supersonic speed condition, and the congestion occurs, so the Mach number meets the relational expression when the congestion occurs
Another expression of the above formula is
M2sinθ＝1 (14)
When the wave front and the wave rear Mach number are determined, the choking pressure ratio is determined according to the isentropic relation
And (4) verifying the suction mass flow rate model, namely verifying the effectiveness of the model through FLUENT numerical simulation, calculating the subsonic front edge as the supersonic front edge, taking the area in the model as the area of a circular hole, and comparing and verifying the model and a numerical simulation result. The flow coefficient Q represents a dimensionless parameter of the suction mass flow rate and is defined as
Wherein
For actually pumping the mass flow rate
Is defined as
Verification of an uncongested suction mass flow rate model is that the diameter D of a circular hole is 10 mm, the incoming flow Mach number M1 is 2.0, the pressure P1 is 101325.0Pa, the temperature T1 is 300.0K, the back pressure P2 of a suction cavity is 50662.5Pa, the flow coefficient Qmodel obtained by the suction model is 7.91e-2, and the evolution law of the flow coefficients of different polygons is shown in FIG. 6. The supersonic velocity suction congestion model shows that the CFD calculated flow coefficient is firstly lower than the model, then higher than the model, and finally gradually approaches the suction model along with the increase of the number of the polygon edges. For a circular hole, the difference between the CFD and the model flow coefficient is 1.4%, and when the order of the polygon is equal to or more than 4, the error of the flow coefficient is less than 2.2%. For a circular orifice, the flow coefficient of the model is lower than the CFD calculation.
The effectiveness of the suction model in the case of congestion is further verified by comparison with CFD. The geometry and mesh used for the unchoked suction holes were still used for the numerical verification, with the inflow pressure and temperature being P1-101325.0 Pa and T1-300.0K, respectively. For an incoming flow mach number M1 of 2, based on a suction congestion model,static pressure ratio of choking2/P10.2651, the flow coefficient Qmodel corresponding to the pressure ratio is 9.50 e-2. By reducing the pressure ratio, the model versus numerical simulation results are shown in table 1 below.
TABLE 1 comparative validation of suction congestion model and CFD calculation results
In table 1, Case3 is a comparative verification carried out at the suction choking critical pressure ratio point, and Case2 and Case1 are calculated at the point lower than the critical pressure ratio point, which shows that the error of the model and the CFD is slightly increased but small as the pressure ratio is reduced, and the model has higher reliability. Numerical simulation shows that the suction flow coefficient of the subsonic front edge is smaller than that of the supersonic front edge, and therefore the conclusion is that the model flow coefficient is larger than the CFD numerical simulation result, but the result shown in the table 1 is opposite, and because the error is small, the error is from grid and boundary effect or transverse flow caused by the circular hole subsonic front edge, the determination cannot be carried out at present.
The method is not only suitable for the scheme design of the high-modulus test suction system, but also suitable for the design of the hypersonic inlet channel suction system. The hypersonic air inlet channel is decelerated and pressurized through multiple shock waves, the pressure of the inlet section is high, the back pressure is the atmospheric pressure of the high flying environment where the aircraft is located, the pressure is low, and the high flying environment is often in a suction choking state, so that the suction model established by the invention has engineering guidance value on the suction layout and scheme of the hypersonic air inlet channel;
the invention only aims at the single hole to establish the pumping model, but according to the parameters of Mach number, pressure and the like at different positions of a flow field, the invention also belongs to the scope of the invention for designing the multi-hole combined distributed pumping system based on the invention.
The pumping flow calculation method is verified by commercial software FLUENT numerical simulation on supersonic speed non-viscous complete gas (gas specific heat ratio gamma is 1.4), the calculation accuracy is slightly different according to different inflow conditions, the maximum error is about 3%, and the method is not verified by experiments at present. In practical engineering applications, the larger the boundary layer thickness at the suction location due to viscous effects, the larger the deviation of the suction model mass flow rate from the actual suction flow rate.
Claims (2)
1. A method for sucking mass flow rate in an active injection high-modulus test of a solid rocket engine is characterized by comprising the following specific steps:
s1: establishing a two-dimensional infinite-length slit suction mass flow rate calculation model, wherein the streamline after expansion wave is a straight line, and for a certain suction hole dimension L, a dimension L corresponding to the last expansion wave is providedeffThe gas in this dimension enters the suction holes completely, and the suction mass flow rate is assumed to be the Mach angle of the last expansion wave and the post-wave streamline is mu 2
Theta is the flow line deflection angle, given by the Prandtl-Meyer relationship
θ＝υ(M2)-υ(M1)；
S2: the circular orifice aspirates the mass flow rate model,
wherein
V2n＝V2sinα
Obtaining leading edge sweep suction mass flow rate
Wherein the sweepback suction area A is LWsweepsin α, hence the mass flow rate is further converted into
S3: deriving critical bands of suction congestionMember, M2sinθ＝1
When the wave front and the wave rear Mach number are determined, the choking pressure ratio is determined according to the isentropic relation
S4: and (4) verifying a suction mass flow rate model, verifying the effectiveness of the model through FLUENT numerical simulation, calculating the subsonic front edge as a supersonic front edge, taking the area in the model as the area of a circular hole, and comparing and verifying through the model and a numerical simulation result. The flow coefficient Q represents a dimensionless parameter of the suction mass flow rate and is defined as
Wherein
To actually pump the mass flow rate, of
Is defined as
2. The active-pilot high-mode-test suction mass flow rate method of the solid-rocket engine as recited in claim, wherein said S1 establishes the basic conditions of the two-dimensional infinite-length slit supersonic suction model:
s11: the front edge of the suction hole is a disturbance point of the supersonic flow field to generate an expansion wave, the disturbance is transmitted along the direction of the expansion wave, and a streamline after the expansion wave is a straight line, so that no pressure difference exists in the direction vertical to the streamline, and the pressure difference is equal to the back pressure behind the suction hole;
s12: suction is a pressure driven phenomenon, the suction flow rate is mainly dependent on the back pressure, which changes the suction mass flow rate by changing the angle of deflection of the air flow at the suction orifice;
s13: the depth L of the suction hole is very small compared to the hole diameter D, and the plate is considered to be without thickness, i.e., L is 0.
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| CN116046334A (en) * | 2023-03-21 | 2023-05-02 | 中国航空工业集团公司沈阳空气动力研究所 | Acoustic explosion measurement system and measurement method based on ballistic target equipment |
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| CN116046334A (en) * | 2023-03-21 | 2023-05-02 | 中国航空工业集团公司沈阳空气动力研究所 | Acoustic explosion measurement system and measurement method based on ballistic target equipment |
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