Compressor blade cutting method and compressor blade for turbine containment test

Abstract

The present invention provides a compressor blade cutting method for turbine containment test, belonging to the technical field of turbines. The present invention comprises the following steps: 1) punching a hole at the center of a predetermined cutting section of a predetermined broken compressor blade; 2) slotting both sides after punching to form a slotted notch, and controlling the remaining area on both sides to be equal. The present invention ensures that the remaining areas on both sides of the slotted notch on the broken section of the compressor blade with a three-dimensional curved surface shape remain equal by punching a hole at the center of the predetermined cutting section of the predetermined broken compressor blade, and slotting from the middle to both sides at the same time, thereby weakening the compressor blade. Since the blade body at the slotted notch is thicker, the stress concentration is not obvious, thereby ensuring that the stress levels at both ends of the slotted notch of the compressor blade remain consistent under high speed conditions, and the breaking speed can be accurately calculated. At the same time, the blade body gradually becomes thinner along the cracking direction, and the cracking process will be an accelerated process, which can effectively control the flying posture of the broken blade.

Description

Technical Field

[0001] The present invention relates to the technical field of turbines, and in particular to a method for cutting compressor blades for turbine containment testing, and more particularly to a method for cutting blades with a three-dimensional curved surface shape for turbine casing containment testing so as to enable axial flow and mixed flow compressor blades to centrifugally fly off within a predetermined high speed range. Background Art

[0002] The compressor in the turbine is a mechanical device that transmits mechanical energy to the gas and completes the gas working medium compression process in the turbine thermal cycle to increase the gas pressure. It is one of the key components in the turbine rotor system. According to the flow direction of the airflow in the compressor, the compressor can be divided into an axial flow compressor and a centrifugal compressor. When it is working, the air pressure entering the turbine is increased to provide high-pressure air to the combustion chamber to improve the efficiency of the turbine thermal cycle. The working characteristics of the compressor rotor lead to a higher operating speed than the power turbine rotor. Therefore, the compressor in the turbine needs to withstand the huge centrifugal stress, aerodynamic force and vibration load caused by high-speed rotation. This harsh working environment makes the compressor one of the main components that determine the life of the turbine. Once the compressor blades are damaged and fail, it will lead to extremely serious consequences. Therefore, the structural strength of the casing outside the compressor blades is very important, so it is extremely important to carry out the containment test of the compressor casing.

[0003] At present, the casing containment test for centrifugal breakage of turbine compressor blades is usually carried out by prefabricating a slotted notch breakage method at the predetermined cross section of the predetermined breakage blade. Since the compressor blade itself has a three-dimensional curved surface shape, the traditional cutting method cuts from both sides of the blade body to the middle. The cutting tool is easy to interfere with the blades on both sides, which is difficult to operate and cannot ensure that the left and right cutting grooves are in the same plane. In addition, the traditional cutting method cannot ensure uniform stress at the remaining cross section in the middle. At this time, the asymmetry of the centrifugal loads on the left and right sides will cause the blade to twist and deform. The local stress at the remaining cross section is affected by the centrifugal load and the torsional load at the same time, causing difficulties in controlling the breakage speed and breakage attitude. Therefore, a reasonable and effective cutting method is needed to effectively ensure that the remaining cross sections on both sides of the cutting are consistent and avoid the problem of stress concentration, so as to accurately control the breakage speed and breakage attitude of the compressor blade. Summary of the invention

[0004] In view of this, in order to solve the technical problem that the blade flying posture is affected by the slotting notch being cut from both ends to the middle in the traditional cutting method, on the one hand, the present invention provides a compressor blade cutting method for turbine containment test, which ensures that the remaining areas on both sides of the slotting notch of the compressor blade with a three-dimensional curved surface on the flying section remain equal by punching a hole at the center of a predetermined cutting section of the predetermined flying blade, and slotting from the middle to both sides at the same time, thereby weakening the compressor blade. Since the blade is thicker at the notch, the stress concentration is not obvious, thereby ensuring that the stress levels at both ends of the slotting notch of the compressor blade remain consistent under high-speed conditions, and the blade flying speed can be accurately estimated. At the same time, the blade thickness gradually becomes thinner along the cracking direction, and the cracking process will be an accelerated process, which can effectively control the flying posture of the flying blade.

[0005] To achieve the above object, the present invention provides the following technical solutions:

[0006] A method for cutting compressor blades for turbine containment testing comprises the following steps:

[0007] 1) Punching a hole at the center of the predetermined cutting section of the predetermined blown-off compressor blade;

[0008] 2) After perforation, slots are cut on both sides at the same time to form slot gaps, and the remaining areas on both sides are controlled to be equal.

[0009] Preferably, in step 1), the diameter of the hole is 0.5 mm.

[0010] Preferably, the lengths of the grooves on both sides are L1 and L2 respectively, the total length is L, L=L1+L2, the widths of the grooves on both sides are 1mm, and both ends of the groove notch are semi-circular corners of R0.5mm.

[0011] Preferably, the following steps are also included before step 1):

[0012] 1.1) Check the verticality of the inclination base. After the check, divide the lower gland into equal parts according to the number of compressor blades, mark the outer cylindrical surface of the lower gland, and use the center positioning stud to apply a certain pre-tightening force to the lower gland to prevent it from moving circumferentially and radially;

[0013] 1.2) Then place the compressor wheel sleeve on the center positioning stud, rotate the compressor wheel circumferentially to adjust the position of the compressor wheel so that the center of the predetermined cutting section of the predetermined flying compressor blade is consistent with the circumferential position of the equal division point of the lower gland, and then start punching.

[0014] Preferably, after step 1.1) and before step 1.2), the method further includes:

[0015] 1.1.1) Determine whether the center axis of the predetermined cutting section of the compressor blade to be cut off is consistent with the equal division point of the lower pressure cover in the actual cutting process according to the equal division position on the lower pressure cover. If not, slightly rotate the lower pressure cover to make it consistent.

[0016] Preferably, during the containment test, if the compressor blades of the pre-cut grooves are centrifugally broken off when the compressor wheel speed is increased to within the target speed range, the containment test is terminated; if the compressor blades of the pre-cut grooves are not centrifugally broken off, cutting is continued, and the cutting lengths ΔL1 and ΔL2 are increased at the same time, so that the remaining cross-sectional areas on both sides of the slotted notch continue to remain equal, and then the above containment test is repeated until the test is terminated.

[0017] On the other hand, the present invention also provides a compressor blade for turbine containment test, which is manufactured according to the above-mentioned compressor blade cutting method for turbine containment test.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] 1) The present invention prefabricates grooves from the center to both sides at the center of the predetermined flying section of the compressor blade, thereby reducing the interference between the cutting tool and the adjacent blades during the specific implementation process, effectively reducing the damage to the structural strength of the adjacent blades, and avoiding the problem of strength weakening of the adjacent blades due to insufficient structural strength.

[0020] 2) The remaining area S on both sides of the groove gap of the present invention is 1 With S 2 The stress state on the remaining cross section is consistent, and the blade body is thicker at the notch, so the stress concentration is not obvious, and the break speed can be estimated more accurately. At the same time, the blade body gradually becomes thinner along the cracking direction, and the cracking process will be an accelerated process, which can effectively control the flying posture of the broken blade.

[0021] 3) The present invention aims at compressor blades with three-dimensional curved surface shapes, and uses a cutting inclination base with a certain angle θ to tilt the compressor wheel at a certain angle, so that the predetermined cutting section of the predetermined flying blade is perpendicular to the horizontal direction, making the cutting of the compressor blade easier and improving the operability of the cutting technology.

[0022] 4) In the compressor blade cutting method described in the present invention, a lower pressure cover is designed at the lower end of the compressor blade and is firmly fitted with the tooling during operation. The lower pressure cover has scale lines on its outer cylindrical surface that divide the circumference equally according to the number of blades, which facilitates the circumferential positioning of the compressor blade during the cutting process, thereby ensuring the cutting accuracy and improving work efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1A schematic diagram of the predetermined cross-sectional cutting dimensions for compressor blades;

[0024] Figure 2 It is a schematic diagram of the compressor blade cutting implementation scheme;

[0025] Figure 2 In the middle, 1. Center positioning stud, 2. Compressor wheel, 3. Flying cutting section, 4. Lower pressure cover, 5. Inclined base. DETAILED DESCRIPTION

[0026] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention; it is obvious that the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments, and all other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making creative work are within the scope of protection of the present invention.

[0027] In the description of the present invention, it should be noted that the terms "upper", "lower", "inside", "outside", "top / bottom" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0028] In view of the fact that the notch cut from both ends to the middle in the traditional cutting method affects the compressor blade break-off posture, the present invention provides a compressor blade cutting method for turbine containment test, which punches holes at the center of the predetermined cutting section of the predetermined break-off blade and simultaneously notches from the middle to both sides, ensuring that the remaining areas of the three-dimensional curved blade of the compressor wheel on both sides of the notch on the break-off section remain equal, thereby weakening the compressor rotor blade. The method causes little damage to adjacent blades, is simple and easy to operate, and can significantly improve the test success rate and the accuracy of the compressor blade break-off speed.

[0029] The technical solution of the present invention is clearly described in detail below with reference to the accompanying drawings.

[0030] like Figure 1-2 As shown, the compressor blade cutting method for turbine containment test provided by the present invention has a specific implementation scheme as follows:

[0031] 1) During the compressor blade cutting process, the verticality of the inclination base 5 is first checked. For compressor blades with three-dimensional curved surfaces, the compressor rotor blade disk is tilted at a certain angle θ through the inclination base 5, so that the axis of the predetermined flying section is perpendicular to the horizontal direction, making it easier to cut and slot the rotor blades. After the verification, the lower pressure cover 4 is divided into equal parts according to the number of compressor blades, and the outer cylindrical surface of the lower pressure cover 4 is marked. Subsequently, a certain preload force is applied to the lower pressure cover 4 with the center positioning stud 1; the compressor wheel 2 is radially positioned by the center positioning stud 1, and the lower pressure cover 4 is designed at the lower end of the compressor wheel 2 and fits tightly with the inclination base 5. Before cutting, the lower pressure cover 4 is divided into equal parts according to the number of blades on its outer cylindrical surface to facilitate the circumferential positioning of the compressor blades during the cutting process.

[0032] 2) After the above work is completed, the center axis of the cut section 3 and the equal division point of the lower gland 4 can be determined according to the equal division position on the lower gland 4 during the actual cutting process. If not, slightly rotate the lower gland 4 to make it consistent. After completion, use the center positioning stud 1 to press the lower gland 4 tightly to prevent it from moving circumferentially and radially.

[0033] 3) Then, place the compressor wheel 2 on the central positioning stud 1, adjust the position of the compressor wheel 2 circumferentially so that the center line of the predetermined cutting surface 3 of the predetermined flying blade is consistent with the equal division point of the lower gland, and then start to perform electric pulse perforation on the center line of the predetermined cutting section 3 of the predetermined flying blade of the compressor, with a perforation diameter of about 0.5mm.

[0034] 4) Then insert a 0.3mm diameter wire into the central hole of the compressor blade and start wire cutting while grooving on both sides to control the remaining area S on both sides. 1 With S 2 The stress state on the remaining cross section is equal, ensuring that the blade breaking posture is not affected during the test. Figure 1 The dimension diagram shown is a prefabricated slotted notch, the slot lengths on both sides of which are L1 and L2 respectively, the total length is L, the slot width is 1mm, and the two ends of the slot are semi-circular corners of R0.5mm.

[0035] 5) After cutting, use composite glue to measure the total length of the slot notch L=L1+L2 to see if it meets the cutting length requirements specified in the test plan. If the result meets the tolerance range requirements, it can be used for inclusion testing.

[0036] 6) During the containment test, if the blade of the pre-cut groove is centrifugally broken when the compressor wheel 2 is accelerated to the target speed range, the containment test is terminated; if the pre-cut blade is not centrifugally broken, continue cutting and increase the lengths of L1 and L2 by ΔL1 and ΔL2, so that the remaining area S of the slotted side is 1With S 2 Continue to maintain equality and then repeat the above inclusion test until the test is completed.

[0037] The following is an explanation using a specific application example.

[0038] (1) Compressor blade perforation

[0039] The purpose of perforating the compressor blade is to facilitate the subsequent wire cutting machine threading, because the cutting plan is to expand the cutting groove from the middle part of the compressor blade root to both sides. First, find the center position of the pre-cut section of the pre-flighted blade in the precision carving processing center.

[0040] The punching position is set in the middle of the intended cutting groove. In the 3D model, the radius of the punching position from the center line is measured to be R57mm, and the axial distance of the punching position from the reference plane is 12mm. The same relative position relationship is set in the machining center.

[0041] In the machining center, the tool is controlled to move to the middle of the two blades, the axial distance from the reference plane is controlled to be -12mm, and then the tool moves counterclockwise in an arc with a radius of R57mm until it touches the blade. The punching point is marked with the tool; after marking the punching point, the tool is replaced with an electric pulse perforating tool head, and a hole is punched at the marked point. The perforation diameter is Φ 0.5mm.

[0042] (2) Blade cutting

[0043] Assemble the compressor wheel 2 with the cutting tool, and tighten the gland fixing rod to prevent circumferential sliding. Mark the matching position between the lower gland and the compressor disc according to the drilling positioning results to ensure that the rotor can be in the same marked position after repeated disassembly and assembly during each wire cutting.

[0044] During the blade wire cutting process, first use the outer four planes of the angled base to touch the wire, so as to ensure that the outer four planes of the angled base are parallel to the coordinate axis of the cutting machine. According to the distance and position relationship between the punching position (i.e. the starting position of the wire cutting slot) and the end face of the tooling, move to determine the starting position of the wire cutting, and ensure that the wire cutting threading position is as close to the punching center as possible. After the above work is completed, start cutting according to the pre-prepared cutting trajectory and cutting amount. Strictly cut according to the L1 and L2 dimensions specified in the inclusive test plan.

[0045] (3) Cutting size measurement

[0046] After the cutting of the press blade is completed, the cutting size is checked and measured. Due to the complex blade shape, the surface curve length of the slot cannot be directly measured with tools. Therefore, the curve distance of the vertices at both ends of the slot is first measured in the three-dimensional model as the measurement section. After the physical blade is slotted, the slot part is reshaped with a composite glue. After the composite is flattened, the straight-line distance of the vertices at both ends of the slot is measured and compared with the surface curve length of the vertices at both ends of the blade slot in the three-dimensional model to determine whether the slot size is accurate. The actual cutting amount L = 11.96mm, the surface curve length of the two ends of the blade slot measured in the three-dimensional model is 21.465mm, and after being reshaped with the composite glue, the slot length measured by flattening the composite is 21.46mm, which meets the test requirements.

[0047] It should be noted that the verification work of this application example is the same as the verification work steps mentioned above.

[0048] The above are only preferred specific implementations of the present invention; however, the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical solutions and improved concepts of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A method for cutting compressor blades for turbine containment testing, characterized in that: The steps include: 1) Punching a hole at the center of the predetermined cutting section of the predetermined blown-off compressor blade; 2) After perforation, slots are made on both sides at the same time to form slot notches, and the remaining areas on both sides are controlled to be equal; The lengths of the grooves on both sides are L1 and L2 respectively, the total length is L, L=L1+L2, the width of the grooves on both sides is 1mm, and the two ends of the groove notch are semi-circular corners of R0.5mm; During the containment test, if the compressor blades with pre-cut grooves are centrifugally broken off when the compressor wheel speed increases to within the target speed range, the containment test is terminated; if the compressor blades with pre-cut grooves are not centrifugally broken off, cutting is continued, and the lengths of L1 and L2 are increased by ΔL1 and ΔL2 at the same time, so that the remaining areas S1 and S2 on both sides of the grooves continue to remain equal, and then the above containment test is repeated until the test is completed.

2. A method for cutting compressor blades for turbine containment testing according to claim 1, characterized in that: In step 1), the diameter of the hole is 0.5 mm.

3. A method for cutting compressor blades for turbine containment testing according to claim 1, characterized in that: Before step 1), the following steps are also included: 1.1) Check the verticality of the inclination base. After the check, divide the lower gland into equal parts according to the number of compressor blades, mark the outer cylindrical surface of the lower gland, and use the center positioning stud to apply a certain pre-tightening force to the lower gland to prevent it from moving circumferentially and radially; 1.2) Then place the compressor wheel sleeve on the center positioning stud, rotate the compressor wheel circumferentially to adjust the position of the compressor wheel so that the center of the predetermined cutting section of the predetermined flying compressor blade is consistent with the circumferential position of the equal division point of the lower gland, and then start punching.

4. A method for cutting compressor blades for turbine containment testing according to claim 3, characterized in that: After step 1.1) and before step 1.2), the following should also be included: 1.1.1) Determine whether the center axis of the predetermined cutting section of the compressor blade to be cut off is consistent with the equal division point of the lower pressure cover in the actual cutting process according to the equal division position on the lower pressure cover. If not, slightly rotate the lower pressure cover to make it consistent.

5. A compressor blade for turbine containment testing, characterized in that: The compressor blade cutting method for turbine containment testing is obtained according to any one of claims 1-4.

Images