KR20100122698A - Testing method and test stand for the determination of the cavitation characteristics of pump - Google Patents

Abstract

PURPOSE: A method and a device for testing the cavitation characteristic of a pump are provided to change the thermodynamic state of working fluid and not heating the whole fluid within a tank, thereby remarkably reducing the working load. CONSTITUTION: A flow valve(10) and an drain valve(26) control supply or discharge of a gas phase supply pipe line(32) of cryogenic liquid. A thermal heat exchanger(11) heats the cryogenic liquid and makes the gas phase. The gas phase flow rate, and pressure and temperature sensors(28,27/29,30) measure the temperature, pressure and flow rate of the gas phase. A gas phase supply pressure controller(13) for the gas phase supply controls the flow rate of the gas phase.

Description

Test method and test facility for testing cavitation characteristics of pumps {Testing method and test stand for the determination of the cavitation characteristics of pump}

FIELD OF THE INVENTION The present invention relates to test methods and facilities for determining the cavitation characteristics of a pump using cryogenic fluids (eg liquid oxygen, liquid hydrogen, etc.) as the operating medium.

The method for measuring the cavitation characteristics of a pump using cryogenic fluid is to perform the test under constant internal energy of the pump working fluid (cryogenic fluid) and to lower the pump inlet pressure, and to saturate the working medium under constant pressure. There is a way to perform the test with varying internal energy up to two states. The first method is the traditional method performed for a general pump, and the second method is important for cryogenic pumps using cryogenic fluid as the working medium. In the pump test to check the operating capacity and cavitation characteristics of the pump, the first method and the second method are continuously performed, and the present invention relates to an improved test facility and test method for implementing the second method.

In order to verify the cavitation characteristics of the pump, the cavitation test facility should be able to change the thermodynamic state of the cryogenic fluid supplied to the pump. In the present invention, in order to check the cavitation characteristics of the pump, an additional gaseous supply line is installed to make the cryogenic liquid into a gaseous phase and introduced into the main supply pipe of the pump, whereby gaseous and liquid cryogenic fluids are mixed. Will occur. This makes it possible to make the state of the working medium entering the pump inlet into a liquid saturated flow state, and increase the gaseous supply to make the flow of the pump inlet into a two-phase saturated state.

When using the present invention, it is possible to perform the test of the pump while changing the test conditions in one test procedure, and as a result, it is possible to reduce the number and cost of test execution.

The conventional technique for the second method proceeds to the following process using the test facility having the structure as shown in FIG.

After the cryogenic fluid is filled in the storage tank 1, the cryogenic fluid is pressurized to P ₁ of FIG. 3 by injecting a non-condensable gas through the pressurizing valve 3. At this time, the pressure measurement is made of the tank pressure sensor (7). Thereafter, the entire cryogenic fluid in the tank is heated to a temperature T ₁ using a heated heat exchanger 33 and checked using a temperature sensor 8. Filling and cooling of the supply pipe are performed by flowing a small flow rate of fluid into the cryogenic fluid supply valve 14 and the supply pipe cooling and discharge valve 19, respectively, using a flow sensor 17 and a flow regulator 18. do. The degree of cooling is measured by the temperature sensor 23. With the flow valve 20 open, the pump 16 is rotated to the required operating conditions using an electric driver or a gas driver. The operating state of the pump is determined by the rotation speed and flow rate of the pump rotor and the pump discharge pressure.

The saturation of the flow is obtained by the pump inlet pressure dropping from P ₁ to P ₂ in FIG. 3 due to the pressure drop occurring as the fluid passes through the orifice 38. The two-phase saturation flow state is achieved by reducing the tank pressure through the drain valve 5 and reducing the pump inlet pressure to P ₃ of FIG. ₃ by the orifice 38. A pressure sensor 21, a temperature sensor 22, and a gas phase flow meter 15 are used to confirm the two-phase state. In this test method, replacement of the orifice 38 has been required to change the level of the biphasic state. The existing method described above was used to test pumps for the J-2 rocket engine in the US and the RD-56 rocket engine in Russia using oxygen and hydrogen as propellants.

Existing test facilities to verify the cavitation characteristics of the pump could simulate only one pump operating condition in one test. The present invention ameliorates these shortcomings so that it is possible to change several thermodynamic states of cryogenic fluids during a single test, thus enabling testing of several operating conditions at once. This saves the time and cost of verifying the cavitation characteristics of the pump and facilitates the preparation and performance of the test.

 The present invention relates to a facility for checking the cavitation characteristics of a pump using cryogenic fluid (eg liquid oxygen, liquid hydrogen, etc.) as the working medium.

In order to verify the cavitation characteristics of the pump, the cavitation test facility should be able to change the thermodynamic state of the cryogenic fluid supplied to the pump. In the present invention, in order to check the cavitation characteristics of the pump, an additional gaseous supply line is installed to make the cryogenic liquid into a gaseous phase and into the main supply pipe of the pump, so that the gaseous condensation occurs after the gaseous and liquid cryogenic fluids are mixed. do. This makes it possible to make the state of the working medium entering the pump inlet into a liquid saturated state, and to increase the gaseous supply to make the flow of the pump inlet into a two-phase saturated state.

When using the present invention, it is possible to perform the test of the pump while changing the test conditions during one test procedure, and as a result, it is possible to reduce the number and cost of test execution.

In the present invention, unlike the conventional cavitation characteristic measuring apparatus, it is possible to change the thermodynamic state of the working fluid during the test and it is not necessary to heat the entire fluid in the tank can significantly reduce the amount of work during the cavitation test of the pump.

In addition, the test can be carried out in a simple way by changing the various conditions during the execution of a single test, reducing the difficulty of performing the test and greatly reducing the cost and time required to prepare and perform the test.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. Prior to this, terms or words used in this specification and claims should not be construed in a common or dictionary sense, and the inventors will be required to properly define the concepts of terms in order to best describe their invention. Based on the principle that it can, it should be interpreted as meaning and concept corresponding to the technical idea of the present invention.

Therefore, the embodiments described in the specification and the configuration shown in the drawings are only the most preferred embodiment of the present invention and not all of the technical idea of the present invention, at the time of the present application, various equivalents that can replace them It should be understood that there may be water and variations.

1 is a structural diagram of a test facility used in the present invention, Figure 2 is a structural diagram of a test facility according to the prior art for measuring the cavitation characteristics, Figure 3 is a liquid saturated state and a two-phase saturated state to explain the formation 4 is a graph illustrating the general cavitation characteristics of the pump, and is a photograph showing the condensation process from the cryogenic liquid to the gas phase.

Cavitation characteristic measurement test facility of the pump according to the present invention is configured as shown in FIG. When using the test facility proposed in the present invention, the process of filling the cryogenic fluid in the storage tank 1 and then heating is omitted. The cooling of the cryogenic fluid supply line 31 and the driving of the pump 16 are the same as in the conventional method, but the process of changing the thermodynamic state parameters of the working medium is different from the conventional method.

That is, in the present invention, the liquid saturated flow state and the two-phase saturated flow state at the inlet of the pump 16 are injected through the cryogenic liquid supply pipe line 31 with the cryogenic liquid gas phase through condensation of the gas phase and the heating of the cryogenic liquid. Obtained.

As shown in Figure 1, the present invention is a test apparatus for checking the cavitation characteristics of a pump using a cryogenic fluid (liquid oxygen, liquid hydrogen, etc.) as a working medium, the cryogenic temperature connected to the pump 16 from the storage tank (1) Cavitation characteristics confirmation test of the pump, characterized in that it comprises a gas supply pipe line 32 is connected to the fluid supply pipe line 31 to make the cryogenic liquid into a gas state to supply to the inlet of the pump 16 It is about a facility.

In addition, the present invention, the gaseous supply piping line 32, the flow rate valve for controlling the supply of cryogenic liquid to the gaseous supply piping line 32, or discharge from the gaseous supply piping line 32, respectively ( 10) a drain valve 26; and a heated heat exchanger 11 for heating the cryogenic liquid into a gas phase; and a gas phase flow sensor 28 for measuring the temperature, pressure, and flow rate of the gas phase, respectively, and the gas phase pressure. Sensors 27 and 29, and a gas phase temperature sensor 30; and a gas phase supply pressure regulator 13 for adjusting the flow rate of the gas phase; And a gas phase supply valve 25 for controlling supply of the gas phase to the inlet of the pump 16.

In addition, the present invention is provided in the gas phase supply pipe line 32, an orifice (37) which is installed in front of the drain valve 26 to adjust the amount and drain rate of the gas phase to be drained; and the gas phase supply valve 25 An orifice 12 installed in front of the gas to control an amount and a supply speed of the gas phase; And a gas phase pressure sensor 35 and a gas phase temperature sensor 36 installed between the gas phase supply valve 25 and the orifice 12 to measure gas pressure and temperature, respectively. do.

That is, the present invention is the test equipment shown in Figure 2 used in the method of performing the test while changing the internal energy to a saturated state or a two-state operating medium under a constant pressure of the equipment used in the method for testing the cavitation characteristics of the pump Will be improved.

In detail, the present invention relates to a cryogenic fluid supply line (31) and a cryogenic liquid connected to a storage tank (1) containing cryogenic liquid for cavitation test of the pump (16) from the storage tank (1) to the pump (16). It is composed of a gaseous supply piping line 32 for making the gas phase into the cryogenic fluid supply piping line (31). A gaseous supply piping line 32 is provided with a heated heat exchanger 11 to heat the cryogenic liquid to form a gas phase, and to adjust the flow rate of the gas phase to the liquid saturated flow state and the two phase ( It is possible to create a saturated flow state.

To make these conditions easier, the gaseous supply piping line 32 includes a flow valve 10, a drain valve 26, a heated heat exchanger 11, a gas phase flow sensor 28, and a gas phase pressure. Sensors 27 and 29, gas phase temperature sensor 30, gas phase supply pressure regulator 13, and gas phase supply valve 25 may be included.

In addition, orifices 37 and 12 may further include a gas phase pressure sensor 35 and a gas phase temperature sensor 36.

Hereinafter, a test for checking the cavitation characteristics of the pump by using the cavitation characteristic confirmation test facility will be described.

The present invention is a test method for confirming the cavitation characteristics of a pump using a cryogenic fluid (liquid oxygen, liquid hydrogen, etc.) as a working medium,

Opening the flow valve 10 and the drain valve 26 of the gas phase supply pipe line 32 to inject cryogenic liquid, and the injected cryogenic liquid is heated to a gaseous heat exchanger 11 to form a gas phase (S11). And the gaseous phase made in step S11 is introduced into the cryogenic fluid supply pipe line 31 while the gas phase supply valve 25 is opened and the drain valve 26 is closed, and the liquid saturated flow state at the inlet of the pump 16. After obtaining the step of measuring the characteristics of the cavitation of the pump 16 in the state (S12); And increasing the pressure of the gas phase supply pressure regulator 13 in the state of step S12 to increase the flow rate of the gas phase to obtain a two-phase (including vapor phase) saturated flow state at the inlet of the pump 16, and then increase the pressure of the gas phase. The cavitation characteristics of the pump 16 according to the amount of gas phase (vapor) contained in the cryogenic fluid supplied to the pump 16 by measuring the gas flow rate and the flow rate increase by the gas phase pressure sensor 27 and the gas phase flow sensor 28, respectively. It relates to a cavitation characteristic confirmation test method comprising a; measuring (S13).

In other words, the present invention will be described in detail by opening the flow valve 10 and the drain valve 26 in the gaseous supply piping line 32, and the cryogenic liquid (gas phase is also included using the heat exchanger 11). Heat) to form a gaseous phase. At this time, the gas phase temperature, pressure and flow rate is measured using the gas phase flow sensor 28, the gas phase pressure sensor 29, and the gas phase temperature sensor 30. The gas phase supply valve 25 is opened and the drain valve 26 is closed to obtain the liquid saturated flow state. The gas phase is introduced into the cryogenic fluid supply pipe line 31 through the gas phase supply valve 25, and the cavitation characteristics of the pump 16 are measured. Thereafter, the gas phase flow rate is increased by increasing the pressure with the gas phase pressure regulator 13 to obtain a two-phase saturated flow state. The gas phase pressure increase and the flow rate increase are measured by the gas phase pressure sensor 27 and the gas phase flow sensor 28, and the pump 16 according to the amount of gas phase (vapor) contained in the cryogenic fluid supplied to the pump 16. Measure the cavitation characteristics of Cavitation characteristics of a typical pump are shown in FIG.

4 is a curve showing the change in pump head roughly according to the volume ratio (δ) of gas (vapor) and liquid. Where U _vapor is the volume of gas and U _liquid is the volume of liquid.

3 is a saturation diagram illustrating the formation of a liquid saturated state and a two-phase saturated state. In FIG. 3, P _s and T _s are the pressure and temperature of a liquid in a saturated state after filling in a storage tank. _l is the temperature in the tank after heating, P _l is the pressurized pressure of the tank, P ₂ and P ₃ are the pressure at the pump inlet, and T ₂ and T ₃ are the temperature at the pump inlet at saturation at P ₂ and P ₃ , T _s1 is the saturation temperature at the pressure in the tank.

The mass flow rate of the gas phase to create the liquid saturated and two-phase saturated states can be calculated by the following equation (A), which is a variation of the energy equation.

m _g1 / m _l1 = {c _l (T _l2 -T _l1 ) + r _l δρ _g2 / ρ _l2 } / {c _g (T _g1 -T _l1 ) + r _g } (A)

Where m _l and m _g are the flow rates of liquid and gas, c _l and c _g are the specific heat of liquid and gas, T _l and T _g are the temperature of liquid and gas, and r _l and r _g are the heat of vaporization of liquid and the condensation of gas. , ρ _l and ρ _g are the density of the liquid and gas, δ is the volume ratio of the gas phase and liquid phase, the index 1 and 2 means the inlet of the gas phase feed pipe line 32 and the inlet of the pump 16, respectively.

The saturated liquid state to be simulated corresponds to δ ₂ = 0, and in a two-phase saturated flow state, δ ₂ > 0. T _l1 is considered to be less than the saturation temperature T _s1 at the pressure in the tank.

The gas phase input into the cryogenic fluid supply piping line 31 includes the length (l _mix ) of the gas and liquid phase mixing zone from the pump inlet, the pressure sensor 21, the temperature sensor 22 and the gas phase flow rate in the flow (vapor volume). The measuring device 15 is made at a position separated by the sum of the lengths to be installed. The length (l _mix ) of the mixed region of the gas phase and the liquid phase can be determined by the empirical formula (B) obtained from the experimental results of the gas phase condensation in the cryogenic liquid.

_{l mix = d [2.4 + L} p (0.33L p -1.5) Re 0.3 Pr 0 .5 / Ia] (B)

Where l _mix = length of the gas and liquid phase mixing zone, d = diameter of the pipe for supplying the gas phase to the cryogenic fluid supply line, Lp (Laplace number = ρ _l ν _l (w _g -w _l ) / σ _l ), Re (Reynolds number = w _l D _{π pe} / ν _l ), Pr (Prandtl number = ρ _l ν _l c _l / λ _l ), Ia (Jacob number = c _l (T _s -T _l ) ρ _l / ρ _l r _l ), w _l and w _g are the gas phase velocities at the liquid velocity and the flow velocity of the feed line, T _l and T _s are the temperature and saturation temperature of the liquid, and λ _l and ν _l are the thermal conductivity coefficients. And kinematic coefficients, ρ _l and ρ _g, are the densities of liquids and gases, and r _l and c _l are the heat and specific heat of vaporization of the liquid.

The gaseous and liquid phases (l _mix ) are regions in the feed tube where gaseous non-equilibrium condensation takes place and are illustrated in the photograph of FIG. 5. Figure 5 (a) is a photograph showing the mixing process when the gas nitrogen is added to the liquid nitrogen when Lp> 1, Figure 5 (b) is when the gas nitrogen is added to the liquid nitrogen when Lp <1 The photo shows the process of mixing.

If the length l between the gas phase inlet point and the pump is greater than the gas and liquid phase mixing zone (l> l _mix ), a thermally equilibrium homogeneous flow is formed at the pump inlet (FIG. 5 (a)). However, when Lp is less than 0.4 to 0.8 depending on the physical properties of the liquid and gas phases, an unstable gas flow occurs in the liquid flow and rises above the flowing liquid, and condensation is not completed in the length l _mix (Fig. 5 (b)). ). Therefore, the pressure in the feed gas phase must be able to produce a rate that satisfies the condition Lp ≥ 1. In other words, as the pressure in the feed gas phase increases, the velocity of the feed gas phase will increase, and as the speed of the feed gas phase increases, Lp will increase, so that the pressure in the feed gas phase is sufficient to have a speed sufficient to satisfy Lp &gt; It must be large.

In this way, the test equipment of the invention is used to rapidly change the thermodynamic state of the working fluid at the pump inlet, so that the temperature of the supply fluid is less than the saturation temperature, heated to saturation, and the gas phase (vapor) is contained. The cavitation test can be carried out continuously in saturation.

Performing the cavitation test is to quickly change the thermodynamic state of the working fluid to create a variety of states and then to calculate the volume of the gas and liquid in each state to find the head according to the volume ratio of gas and liquid using FIG. It is possible.

As described above, although the present invention has been described by way of limited embodiments and drawings, the present invention is not limited thereto and is intended by those skilled in the art to which the present invention pertains. Of course, various modifications and variations are possible within the scope of equivalents of the claims to be described.

1 is a structural diagram of a test facility used in the present invention,

2 is a structural diagram of a test facility according to the prior art for measuring cavitation characteristics,

3 is a saturation diagram for explaining the formation of a liquid saturated state and a two-phase saturated state;

Figure 4 is a graph for explaining the general cavitation characteristics of the pump,

5 is a photograph showing the condensation process from the cryogenic liquid to the gas phase.

<Explanation of symbols for the main parts of the drawings>

1: Storage tank 3: Pressure valve

5: Drain valve 12,37,38: Orifice

7 tank pressure sensor 8 temperature sensor

10: flow valve

11,33: Heat exchanger 13: Pressure regulator for gas phase supply

14 Cryogenic fluid supply valve 15 Gas phase flow rate (vapor) measuring instrument

16 pump 17 flow sensor

18,34: flow regulator 19: supply pipe cooling and discharge valve

20: flow valve 21, 24: pressure sensor

22,23: temperature sensor 25: gas phase supply valve

26: drain valve 27, 29, 35: gas phase pressure sensor

28: gas phase flow sensor 30,36: gas phase temperature sensor

31 Cryogenic fluid supply piping line 32: Gas phase supply piping line

Claims (6)

In a test apparatus for checking the cavitation characteristics of a pump using cryogenic fluid (liquid oxygen, liquid hydrogen, etc.) as the working medium, It is connected to the cryogenic fluid supply pipe line 31 connected to the pump 16 from the storage tank 1 to make the cryogenic liquid into a gaseous state and includes a gaseous supply pipe line 32 to supply to the inlet of the pump 16. Test facility to check the cavitation characteristics of the pump. The method of claim 1, The gas phase supply pipe line 32, The cryogenic liquid is supplied to the gaseous supply piping line 32, or the flow rate valve 10 and the drain valve 26 which respectively regulate the discharge from the gaseous supply piping line 32 and the cryogenic liquid are heated to the gas phase. Heated heat exchanger 11 to make; and the gas phase flow sensor 28, the gas pressure sensor 27, 29, and the gas phase temperature sensor 30 to measure the gas phase temperature, pressure, and flow rate respectively; A pressure regulator 13 for supplying gas phase to regulate the flow rate of the phase; And a gas phase supply valve (25) for controlling supply of the gas phase to the inlet of the pump (16). The method of claim 2, The gas phase supply pipe line 32, An orifice (37) installed in front of the drain valve (26) to adjust the amount of gaseous phase and the drain rate; and an orifice installed in front of the gaseous supply valve (25) to adjust the amount and supply rate of the gaseous phase. (12); And a gas phase pressure sensor 35 and a gas phase temperature sensor 36 installed between the gas phase supply valve 25 and the orifice 12 to measure gas pressure and temperature, respectively. Test facility to check the cavitation characteristics of the pump. In the test method for confirming the cavitation characteristics of a pump using cryogenic fluid (liquid oxygen, liquid hydrogen, etc.) as the working medium, Opening the flow valve 10 and the drain valve 26 of the gas phase supply pipe line 32 to inject cryogenic liquid, and heating the injected cryogenic liquid with the heating type heat exchanger 11 to form a gas phase (S11). ;Wow The gas phase made in the step S11 is introduced into the cryogenic fluid supply pipe line 31 with the gas phase supply valve 25 open and the drain valve 26 closed to obtain a liquid saturated flow state at the inlet of the pump 16. After that step (S12) measuring the characteristics of the cavitation of the pump 16; And In the state of the step S12 by increasing the pressure of the gas phase supply pressure regulator 13 to increase the flow rate of the gas phase to obtain a two-phase (including vapor phase) saturated flow state at the inlet of the pump 16 and then increase the pressure of the gas phase The flow rate increase was measured by the gas phase pressure sensor 27 and the gas phase flow sensor 28, respectively, to determine the cavitation characteristics of the pump 16 according to the amount of gas phase (vapor) contained in the cryogenic fluid supplied to the pump 16. Cavitation characteristics confirmation test method of the pump comprising a step (S13) to measure. The method of claim 4, wherein In the step S12, In order to obtain a liquid saturated flow state at the inlet of the pump 16, the position (l _mix ) at which the gas phase should be introduced into the cryogenic fluid supply pipe line 31 connected to the pump 16 is used by the following [Experimental Formula]. Cavitation characteristics confirmation test method of the pump, characterized in that for determining. [Equation] _{l mix = d [2.4 + L} p (0.33L p -1.5) Re 0.3 Pr 0 .5 / Ia] Where l _mix = length of the gas and liquid phase mixing zone, d = diameter of the pipe for supplying the gas phase to the cryogenic fluid supply line, Lp (Laplace number = ρ _l ν _l (w _g -w _l ) / σ _l ), Re (Reynolds number = w _l D _{π pe} / ν _l ), Pr (Prandtl number = ρ _l ν _l c _l / λ _l ), Ia (Jacob number = c _l (T _s -T _l ) ρ _l / ρ _l r _l ), w _l and w _g are the gas phase velocities at the liquid velocity and the flow velocity of the feed line, T _l and T _s are the temperature and saturation temperature of the liquid, and λ _l and ν _l are the thermal conductivity coefficients. And kinematic coefficients, ρ _l and ρ _g are the density of liquids and gases, r _l and c _l are the heat and specific heat of vaporization of the liquid. The method of claim 4, wherein In the step S12 or S13, In order to obtain a liquid saturated state or a two-phase saturated state at the inlet of the pump 16, the pressure of the feed gas phase is expressed as' dimensional dimension Lp (Laplace number = ρ _l ν _l (w _g -w _l ) / σ _l ) ≥ Cavitation characteristic verification test method characterized in that it can produce a speed that satisfies the condition of 1 '.

Images