Ejector Ratio Test Method for Direct-Connected Core Engine Test Stand

Abstract

Provide a method for testing the entrainment ratio of a direct-connected core engine test stand, including the following steps: S1 Make the direct-connected core engine in any steady-state stage of the core engine; S2 Set a first measurement section at the outlet of the direct-connected core engine, and measure the first temperature T g on the first measurement section, and obtain the first specific heat capacity at constant pressure Cp of the gas on the first measurement section g , set a second measurement section upstream of the inlet of the direct-connected core engine, and measure the second temperature T TC on the second measurement section, and obtain the second specific heat capacity at constant pressure Cp of the gas on the second measurement section TC , set a third measurement section in the ejector barrel, and measure the third temperature T mix on the third measurement section; S3 Calculate the entrainment ratio β through the T g , Cp g , T TC , Cp TC and T mix . Through the above test method, the entrainment ratio of the test stand can be tested conveniently and quickly, and the measurement equipment and cost required in the measurement process can be effectively reduced.

Description

Technical Field

[0001] The present invention relates to an aviation direct-connected core engine test stand, and particularly to a test method for the entrainment ratio. Background Art

[0002] The aviation core engine test stand is one of the core engine ground test links, used to test and analyze the performance of the aviation core engine to check whether it meets the design standards. As Figure 1 shown, the high-temperature and high-speed gas discharged from the outlet 152 of the direct-connected core engine 15 flows along the center line into the ejector barrel 14, and at the same time forms an entrainment effect on the peripheral air of the outlet 152, so that the air flow in the test workshop 10 flows into the ejector barrel 14 along the annular channel formed by the annular wall of the ejector barrel 14 and the core hot gas, thereby causing the pressure in the ejector barrel 14 to drop. Under the action of the pressure difference, the outside atmosphere is promoted to flow into the test workshop 10 through the bypass intake tower (not shown in the figure).

[0003] This air flow enters from the bypass intake tower of the test workshop, thus forming a ventilation effect on the test workshop 10, ensuring that the temperature of the equipment working environment in the test workshop 10 is close to a constant temperature, and reducing the risk of the external test cables of the direct-connected core engine 15 being burned due to the backflow of hot gas. In the ejector barrel 14, the high-temperature gas is mixed with the low-temperature air, and the temperature of the hot gas continuously decreases, and finally flows from the tail in the ejector barrel 14 to the exhaust tower 16, and flows into the outside atmosphere upward after noise reduction treatment in the exhaust tower 16.

[0004] The entrainment ratio of the test stand refers to the ratio of the air flow rate flowing through the test workshop to the intake air flow rate of the core engine. The larger the entrainment ratio value, the better the entrainment effect in the test workshop and the less the backflow of hot gas; the smaller the entrainment ratio value, the worse the entrainment effect in the test workshop. If the entrainment ratio value is less than 0.8, it indicates that there may be backflow of hot gas in the test workshop.

[0005] The existing measurement method for the entrainment ratio is to arrange pitot tubes in the straight section of the bypass intake tower or in the test workshop to measure the total pressure and static pressure of the bypass intake air. In the data acquisition system, the Mach number and air density of the bypass intake air are calculated by using the measured data and the atmospheric weather station, and finally the flow rate flowing through the test workshop is obtained. However, the cross-sectional dimensions of the bypass intake tower or the test workshop are usually large. The above test method requires a measurement section to be accurately measured, and 16 - 25 pitot tube probes are evenly arranged in the measurement section for measurement. During the measurement process, due to the velocity distortion in the intake air flow field of the test workshop of the core engine test stand, there will be deviations in the measured total pressure and static pressure, and the error transmission will ultimately lead to deviations in the calculated flow rate; and each pitot tube needs to be checked for leakage to ensure the validity of the test data, resulting in a long test preparation period and a high comprehensive cost. Summary of the Invention

[0006] An object of the present invention is to provide a method for testing the entrainment ratio of a test stand, which can simply obtain the entrainment ratio of a direct-connected core engine test stand, effectively reduce the measurement steps, and reduce the measurement cost.

[0007] The method for testing the entrainment ratio of a test stand to achieve the above object includes the following steps: S1 Make the direct-connected core engine be in any steady state stage of the core engine; S2 Set a first measurement section at the outlet of the direct-connected core engine, measure the first temperature T on the first measurement section g , and obtain the first specific heat capacity at constant pressure Cp of the gas on the first measurement section g , set a second measurement section upstream of the inlet of the direct-connected core engine, measure the second temperature T on the second measurement section TC , obtain the second specific heat capacity at constant pressure Cp of the gas on the second measurement section TC , set a third measurement section in the ejector barrel, measure the third temperature T on the third measurement section mix ; S3 Determine the entrainment ratio β through T g , Cp g , T TC , Cp TC and T mix .

[0008] In one embodiment, the formula for determining the entrainment ratio β through the T g , Cp g , T TC , Cp TC and T mix in S3 is

[0009] In one embodiment, a plurality of temperature test points are set on the first measurement section, the second measurement section and the third measurement section, and the first temperature T g , the second temperature T TC and the third temperature T mix are respectively the averages of the plurality of temperature test points on the corresponding test sections.

[0010] In one embodiment, the third measurement section is located in the straight section of the ejector barrel, 6D1 in to 8D1 in away from the inlet of the ejector barrel, where D1 in is the diameter of the inlet of the ejector barrel.

[0011] In one embodiment, the second measurement section is not less than 3D2 away from the inlet of the direct-connected core engine in , where D2 in is the diameter of the inlet of the direct-connected core engine.

[0012] During the above-mentioned ejector ratio test on the test bench, since the heat loss of the exhaust gas from the direct-connected core engine after flowing through the ejector barrel is equal to the heat increase of the air in the test workshop after mixing with the exhaust gas, the air flow ratio in the ejector ratio concept can be converted into a temperature ratio through the law of conservation of energy and the basic formulas of thermodynamics. By only measuring the first temperature T of the high-temperature gas at the outlet of the direct-connected core engine g , the second temperature T of the low-temperature air in the test workshop TC and the third temperature T of the mixed gas in the ejector barrel mix , and obtaining the first specific heat capacity at constant pressure Cp of the gas g and the second specific heat capacity at constant pressure Cp of the gas TC , the ejector ratio can be obtained without counting the flow rate values, which improves the measurement efficiency. And since the outlet temperature of the direct-connected core engine is a safety monitoring parameter of the core engine, there is no need to additionally configure an exhaust temperature measuring point, effectively simplifying the measurement steps and saving the measurement cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] The above and other features, properties, and advantages of the present invention will become more apparent from the following description in conjunction with the drawings and embodiments, where:

[0014] Figure 1 is a flowchart of the test bench ejector ratio test method.

[0015] Figure 2 is a schematic diagram of the test workshop.

[0016] Figure 3 is a schematic diagram of the test bench ejector barrel.

[0017] Figure 4 is a schematic diagram of an embodiment of the temperature measurement points on the first measurement section.

[0018] DESCRIPTION OF THE REFERENCE NUMERALS

[0019] 10 Test workshop

[0020] 14 Ejector barrel

[0021] 16 Exhaust tower

[0022] 15 Direct-connected core engine

[0023] 20 Temperature measurement point

[0024] 21 First measurement section

[0025] 22 Second measurement section

[0026] 23 Third measurement section

[0027] 151 Inlet

[0028] 152 Outlet

[0029] 141 Ejector Inlet

[0030] 143 Straight Section Specific Embodiment

[0031] The present invention will be further described below in conjunction with specific embodiments and the accompanying drawings. More details are set forth in the following description to facilitate a full understanding of the present invention. However, the present invention is clearly capable of being implemented in many other ways different from this description. Those skilled in the art can make similar generalizations and deductions according to the actual application situation without departing from the connotation of the present invention. Therefore, the scope of protection of the present invention should not be limited by the content of this specific embodiment. It should be noted that these and subsequent other drawings are only examples and are not drawn under the condition of equal proportions, and should not be used to limit the actual scope of protection required by the present invention. It should be noted that the core engine test bench ejector ratio test method designed by the present disclosure is applied to the field of direct-connected core engines.

[0032] As Figure 3 shown, the direct-connected core engine test bench ejector ratio test method first performs step S1 to make the direct-connected core engine 15 in any core engine steady state stage. The steady state of the core engine (steady-state of core engine) refers to the state where the internal air flow and components of the core engine are in thermal equilibrium, indicating that the state parameters of the core engine do not change with time or fluctuate slightly within a certain control range. For example, when the core engine is in a working state where the actual working power reaches 60% or 70% of the designed rated power, and the internal of the core engine maintains stability and various operating parameters do not change at this time, it can be determined that the core engine is in the core engine steady state stage. In the actual test process, the core engine steady state stage includes but is not limited to the above embodiments, as long as any core engine steady state stage where the internal air flow and components of the core engine are in thermal equilibrium can be used.

[0033] After the direct-connected core engine 15 is in any direct-connected core engine steady state stage, step S2 is performed. A first measurement section 21 is set at the outlet 152 of the direct-connected core engine 15 to measure the first temperature T g on the first measurement section 21, and obtain the first specific heat capacity at constant pressure Cp of the gas on the first measurement section 21 g ; a second measurement section 22 is set upstream of the inlet of the direct-connected core engine 15 to measure the second temperature T TC on the second measurement section 22, and obtain the second specific heat capacity at constant pressure Cp of the gas on the second measurement section 22 TC ; a third measurement section 23 is set in the ejector to measure the third temperature T mixThe above values can be recorded manually or directly obtained by the data acquisition system in the test workshop. After obtaining the above values, step S3 is quickly executed to efficiently complete the test work. Step S3 is to calculate the entrainment ratio β through the first temperature T obtained in step S2 g , the first specific heat capacity at constant pressure Cp of the gas g , the second temperature T TC , the second specific heat capacity at constant pressure Cp of the gas TC and the third temperature T mix It should be noted that the entrainment ratio β calculated at this time is the entrainment ratio β when the direct-connected core engine 15 is in the steady-state stage of this core engine

[0034] When the direct-connected core engine 15 is in the idle state during the steady-state stage, the exhaust gas temperature at the outlet remains relatively stable with the air temperature in the test workshop, and the entrainment ratio β does not change. However, when the direct-connected core engine rises from the idle state in the steady-state stage to a non-idle state in the steady-state stage, the entrainment ratio β of the test bench will change. Therefore, to determine whether the test bench is normal under various operating conditions, it is necessary to change the steady-state stage of the core engine based on steps S1 - S3, repeat steps S2 and S3, and obtain the entrainment ratios under multiple steady-state stages of the core engine. Select the minimum value among the entrainment ratios under multiple steady-state stages of the core engine and compare the minimum value with 0.8 to judge the operating condition of the test bench. If the minimum entrainment ratio is still greater than 0.8, it indicates that the overall entrainment effect of the test workshop is normal and there is no problem of hot gas backflow

[0035] For example, when the operating state of the direct-connected core engine 15 is below 60% of the rated power, obtain the entrainment ratio β1 under the steady state of this core engine according to steps S1 - S3; when the operating state of the direct-connected core engine 15 is at 80% of the rated power, obtain the entrainment ratio β2 under the steady state of this core engine according to steps S1 - S3. If β1 is less than β2, then compare β1 with the standard entrainment ratio value of 0.8. If the smaller entrainment ratio β1 is still greater than the standard entrainment ratio value of 0.8, it indicates that the overall operating effect of the direct-connected core engine test bench is normal, and it is thus judged that there is no phenomenon of hot gas backflow in the test workshop

[0036] The specific measurement positions of the first measurement section 21, the second measurement section 22, and the third measurement section 23 can refer to Figure 1 and Figure 2 . As a preferred implementation, the third measurement section 23 is located in the straight section 143 of the ejector barrel 14, within a range of approximately 6D1 in ~8D1 in from the inlet 141 of the ejector barrel, where D1 inis the diameter of the ejector barrel inlet 141. By setting the third measurement section 23 at a distance of six to eight times the inlet diameter from the ejector barrel inlet 141, it is possible to ensure sufficient mixing of the exhaust gas from the outlet 152 of the direct-connected core engine 15 and the air in the test workshop 10 at the third measurement section 23, and improve the third temperature T mix of the measurement accuracy.

[0037] In one embodiment, referring to Figure 1 as described, the first measurement section 21 is located at the core engine tail nozzle, and the temperature at the tail nozzle is used as the first temperature T g . In another embodiment, the first measurement section 21 can also be located at the outlet of the high-pressure turbine of the direct-connected core engine, and the first temperature T g is the temperature at the outlet of the high-pressure turbine of the direct-connected core engine.

[0038] In one embodiment, the second measurement section 22 is located at a distance not less than 3D2 inn from the inlet of the direct-connected core engine 15, where D2 in is the diameter of the inlet 151 of the direct-connected core engine 15. By setting the second measurement section 22 at a distance not less than three times the inlet diameter from the inlet of the direct-connected core engine 15, it is possible to ensure that the gas at the second measurement section 22 is ordinary air in the test workshop 10 that is not disturbed by the exhaust gas discharged from the direct-connected core engine 15, thereby improving the measurement accuracy of the second temperature T TC at the second measurement section 22.

[0039] The above embodiments only take a direct-connected core engine of one model as an example. Those skilled in the art will understand that when the model of the direct-connected core engine changes, the specific measurement positions of the first measurement section 21, the second measurement section 22, and the third measurement section 23 can be changed according to the specific test environment without departing from the scope of the present disclosure.

[0040] To further improve the accuracy of the test, a preferred embodiment is that multiple temperature test points are provided on the first measurement section 21, the second measurement section 22, and the third measurement section 23, and the first temperature T g , the second temperature T TC and the third temperature T mix are respectively the averages of the multiple temperature test points on the first measurement section 21, the second measurement section 22, and the third measurement section 23.

[0041] Referring to Figure 4 for understanding, four temperature test points 20 are evenly distributed along the circumferential direction of the first measurement section 21, and the first temperature T g on the first measurement section 21 is the average of the data measured by the four temperature test points 20. The setting method of the temperature test points 20 includes but is not limited to Figure 4In the illustrated embodiment, in other embodiments, the tester may increase the number of temperature test points 20 or change the measurement positions of the temperature test points 20 according to the actual test situation to increase the measurement accuracy without departing from the scope of the present disclosure.

[0042] The arrangement of the temperature test points on the second measurement section 22 and the third measurement section 23 may refer to the first measurement section 21 described in the above embodiment, and will not be elaborated here.

[0043] The gas on the second measurement section 22 is ordinary low-temperature air in the test workshop 10. Therefore, the second specific heat capacity at constant pressure Cp of the second gas on the second measurement section 22 TC is obtained according to the air specific heat capacity at constant pressure table and the second temperature T. TC The air specific heat capacity at constant pressure table may refer to the specific content in "Engineering Thermodynamics (Fourth Edition)" (written by Shen Weidao and Tong Jungeng, published by Higher Education Press), and will not be elaborated here.

[0044] The first measurement section 21 is located at the outlet 152 of the direct-connected core engine 15. Those skilled in the art can understand that the gas composition on the first measurement section 21 is a high-temperature gas mixture released in the combustion chamber of the direct-connected core engine, including such as C a H b , CO x , O2, HC, NO x and other chemical components.

[0045] The first specific heat capacity at constant pressure Cp of the gas mixture on the first measurement section 21 g is obtained by the exhaust gas composition and components measured in the combustion chamber component test through the calculation formula of the specific heat capacity of the mixed gas. The calculation formula of the specific heat capacity at constant pressure of the mixed gas may also refer to "Engineering Thermodynamics (Fourth Edition)" (Shen Weidao, Tong Jungeng, etc., published by Higher Education Press), and will not be elaborated here.

[0046] It should be noted that in the above entrainment ratio test method, when the direct-connected core engine changes to the steady state stage, the components and proportions of the gas mixture on the first measurement section 21 will change. However, since the model of the direct-connected core engine 15 remains the same during the test, and the change of the gas mixture under multiple steady state stages of the direct-connected core engine during the test has a negligible impact on the value of the specific heat capacity at constant pressure Cp g of the mixed gas, therefore, in the actual test process, the first specific heat capacity at constant pressure Cp g can be approximately regarded as a stable value, determined by the first specific heat capacity at constant pressure calculated according to the components and proportions of the gas mixture at any steady state stage of the direct-connected core engine. There is no need to re-measure the gas composition in the combustion chamber when the direct-connected core engine changes its working state, which can reduce the test steps and simplify the test process.

[0047] As a preferred embodiment, in step S3, through the said T g , Cp g , T TC , Cp TC and T mix the calculation method for determining the entrainment ratio β is The calculation principle thereof can be referred to the following explanation.

[0048] Since the direct-connected core engine 15 discharges the high-temperature gas mixture, the ordinary low-temperature air in the test workshop 10 is involved. Therefore, the temperature of the ordinary low-temperature air in the test workshop 10 will increase after mixing with the high-temperature gas mixture, while the temperature of the high-temperature gas mixture will decrease after mixing with the high-temperature gas mixture. According to the law of conservation of energy, the heat released due to the temperature decrease of the high-temperature gas mixture is equal to the heat obtained due to the temperature increase of the ordinary low-temperature air.

[0049] Combined with Figure 1 Understand that the first temperature T g is the temperature of the high-temperature gas mixture, the second temperature T TC is the temperature of the ordinary low-temperature air, and the third temperature T mix is the temperature of the mixed gas of the low-temperature air and the high-temperature gas in the ejector barrel. In comparison with the third temperature T mix which is an intermediate temperature value, the heat released when the first temperature T g of a certain flow rate of gas drops to the third temperature T mix is equal to the heat obtained when the second temperature T TC of a certain flow rate of gas rises to the third temperature T mix . Therefore, according to the laws of thermodynamics, the heat equality formula Q g Cp g T g +Q TC Cp TC T TC =(Q g Cp g +Q TC Cp TC )T mix is obtained, where Q TC is the air flow rate flowing through the test workshop, and Q g is the intake air flow rate of the direct-connected core engine.

[0050] The physical meaning of the first item on the left side of the above equation represents the heat of the high-temperature gas mixture located at the first measurement section 21, the physical meaning of the second item on the left side of the equation represents the heat of the ordinary low-temperature air located at the second measurement section 22, and the physical meaning of the right side of the equation represents the heat after the high-temperature gas mixture and the ordinary low-temperature air are mixed in the third measurement section 23 of the ejector barrel 14.

[0051] Shift the left and right sides of the above equation to obtain Q TC Cp TC (T mix -T TC ) = Q g Cp g (T g -T mix ) The physical meaning on the left side of the formula is the heat obtained by the ordinary low-temperature air in the test workshop 10 during the temperature rise in the ejector tube 14, and the physical meaning on the right side of the formula is the heat released by the high-temperature gas mixture at the outlet 152 during the temperature drop in the ejector tube 14.

[0052] The definition formula of the ejector ratio β of the test stand is That is, the ejector ratio β is equal to the air flow rate Q flowing through the test workshop TC and the intake air flow rate Q of the direct-connected core engine g ratio.

[0053] Substitute the formula Q TC Cp TC (T mix -T TC ) = Q g Cp g (T g -T mix ) with the definition formula of the ejector ratio β Combined, it can be transformed to obtain

[0054] Further derivation gives the calculation formula for the ejector ratio β of the test stand as

[0055] The above calculation formula transforms the ratio of flow rates into the ratio of temperatures. Only three temperature parameters need to be measured to obtain the ejector ratio of the test stand for the direct-connected core engine test stand, solving the problem of difficult measurement of the ejector ratio of the direct-connected core engine test stand, with low cost and operability; at the same time, it can verify the hot gas reflux phenomenon of the direct-connected core engine test stand. When the calculated ejector ratio value is less than 0.8, it can be determined that there is a high probability of hot gas reflux in the test workshop. In addition, since the exhaust gas temperature at the outlet of the direct-connected core engine is one of the core engine safety monitoring parameters, there is no need to additionally configure an exhaust gas temperature measurement point, and the values required for calculating the ejector ratio can be directly measured while detecting the temperature, effectively simplifying the measurement steps.

[0056] Although the present invention is disclosed above in preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make possible changes and modifications without departing from the spirit and scope of the present invention. Therefore, any modifications, equivalent changes and decorations made to the above embodiments based on the technical essence of the present invention without departing from the technical solution of the present invention all fall within the protection scope defined by the claims of the present invention.

Claims

1. A method for testing the entrainment ratio of a direct-connected core engine test stand, characterized in that The method includes the following steps: S1. Make the direct-connected core engine in any steady-state stage of the core engine; S2 sets a first measurement section at the outlet of the direct-connected core engine to measure the first temperature T at the first measurement section g and obtain the first specific heat capacity at constant pressure Cp of the gas at the first measurement section g , A second measurement section is arranged upstream of the inlet of the direct-connected core engine to measure a second temperature T at the second measurement section TC and obtain a second specific heat capacity at constant pressure Cp of the second gas at the second measurement section TC , A third measurement section is arranged in the ejector barrel to measure a third temperature T at the third measurement section mix ; T obtained by S3 from S2 g , Cp g , T TC , Cp TC and T mix Determine the entrainment ratio β, and the calculation formula for the entrainment ratio β is .

2. The ejector ratio test method for the direct-connected core engine test stand according to claim 1, characterized in that A plurality of temperature test points are provided on each of the first measurement section, the second measurement section, and the third measurement section, and the first temperature T g , the second temperature T TC , and the third temperature T mix are respectively the averages of the plurality of temperature test points on the corresponding test sections.

3. The ejector ratio test method for the direct-connected core engine test stand according to claim 1, characterized in that The third measurement section is located in the straight section of the ejector barrel, 6D1 away from the inlet of the ejector barrel in ~8D1 in , where D1 in is the diameter of the inlet of the ejector barrel.

4. The ejector ratio test method for the direct-connected core engine test stand according to claim 1, wherein, The second measurement cross-section is not less than 3D2 away from the inlet of the direct-connected core engine inn , where D2 in is the diameter of the inlet of the direct-connected core engine

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