An Improved Blade Vibration Parameter Identification Method considering Tip Clearance Variation

Blade tip timing (BTT) technology is the most effective means for real-time monitoring of blade vibration. Accurately extracting the time of blade tip reaching the sensors is the key to ensure the accuracy of the BTT system. The tip clearance changes due to various complex forces during high-speed rotation. The traditional BTT signal extraction method does not consider the influence of tip clearance change on timing accuracy and introduces large timing errors. To solve this problem, a quadratic curve fitting timing method was proposed. In addition, based on the measurement principle of the eddy current sensors, the relationship among the output voltage of the eddy current sensor, tip clearance, and the blade cutting magnetic line angle was calibrated. A multisensor vibration parameter identification algorithm based on arbitrary angular distribution was introduced. Finally, the experiments were conducted to prove the effectiveness of the proposed method. The results show that in the range of 0.4 to 1.05 mm tip clearance change, the maximum absolute error of the timing values calculated by the proposed method is 26.0359 us, which is much lower than the calculated error of 203.7459 us when using the traditional timing method. When the tip clearance changed, the constant speed synchronous vibration parameters of No. 0 blade were identified. The average value of the vibration amplitude is 1.0881 mm. Compared with the identification results without changing tip clearance, the average value error of the vibration amplitude is 0.0017 mm. It is proved that within the blade tip clearance variation of 0.4 to 0.9 mm, the timing values obtained by the proposed timing method can accurately identify the vibration parameters of the blade.

The Influence of the Axial Rub Added in the Radial Rub on the Wear of the Seal Fins during the High Speed Rub of Labyrinth-Honeycomb Seal

Labyrinth-honeycomb seals are a state-of-the-art sealing technology commonly used in aero-engine interstage seal. The undesirable severe rub between the seal fins and the honeycomb due to the clearance change may induce the cracking of the seal fins. A pervious study investigated the wear of the seal fins at different radial incursion rates. However, due to the axial thrust and mounting clearance, the axial rub between the seal fins and the honeycomb may occur. Hence, this paper focuses on the influence of the axial rub added in the radial rub on the wear of the seal fins. The rub tests results, including rubbing forces and temperature, wear rate, worn morphology, cross-sectional morphology and energy dispersive spectroscopy results, are presented and discussed. Overall, the participation of the axial rub leads to higher rubbing forces, temperature, and wear rate. The tribo-layer on the seal fin is thicker and the cracks are more obvious at high axial incursion rate. These phenomena indicate the axial rub has a negative influence on the wear of the seal fins and should be avoided.

Numerical Calculation of Seal Clearance Change in Installation Process of a 1000MW Nuclear Steam Turbine HIP Casing

During installation process, most of 1000MW-class nuclear power steam turbines will undergo certain deformations due to their own big size and heavy weight, which will change seal clearances in the steam passage. The clearance change will affect steam turbine’s efficiency, and may cause rubbing faults and even strong abnormal vibration, affecting the safety of the steam turbine. Moreover, limited by the complex structure and measurement method, it is difficult to measure deformation and seal clearance accurately, so it is necessary to study the change tendency of the clearance in the installation process. In this paper, a HIP (High and Intermediate Pressure) casing of a 1000MW nuclear steam turbine was taken as the research object, and its 3D geometry model is established based on Pro/E software. By using ANSYS WORKBENCH, we calculated the deformation of the HIP casing during installation with five steps, which are named as: ① lower casing with lower diaphragms, ② step ① + upper diaphragms, ③ step ② + upper casing, ④ step ③ + bolting, and ⑤ replacing the support. Then we analyzed the change of the seal clearance during the installation process by deformation differences of some points under different conditions. The calculation results show that the maximum deformation of the HIP Casing during the installation process occurs in the middle of casing close to the IP (Intermediate Pressure) casing. The relative change of the clearance during the whole process is 0.6–0.8 mm. The change of seal clearance is largest at the first-stage of IP casing, and it can be 0.8mm during replacement of the support.

Experimental Investigation of Factors Influencing Operating Rotor Tip Clearance in Multistage Compressors

An analysis of compressor rotor tip clearance measurements using capacitance probe instrumentation is discussed for a three-stage axial compressor. Thermal variations and centrifugal effects related to rotational speed changes affect clearance heights relative to the assembled configuration. These two primary contributions to measured changes are discussed both independently and in combination. Emphasis is given to tip clearance changes due to changing loading condition and at several compressor operating speeds. Measurements show a tip clearance change approaching 0.1 mm (0.2% rotor span) when comparing a near-choke operating condition to a near-stall operating condition for the third stage. Additional consideration is given to environmental contributions such as ambient temperature, for which changes in tip clearance height on the order of 0.05 mm (0.1% rotor span) were noted for temperature variations of 15°C. Experimental compressor operating clearances are presented for several temperatures, operating speeds, and loading conditions, and comparisons are drawn between these measured variations and predicted changes under the same conditions.

Prediction of Fine Blanking Tool Deformation to Produce Multiple Turbocharger Vane Levers with Stainless Steel

The use of turbochargers improves engine power, reduces the rate of fuel consumption. The vane lever is an important part of a turbocharger that regulates the volume of hot exhaust gas. Until now it has been produced by a 4 cavity fine blanking tool, but it requires the use of an 8 cavity fine blanking tool for better productivity. In this paper, we conducted structural simulation of an 8 cavity fine blanking tool and predicted the deformation of fine blanking tool elements. The maximum vertical deformation of the die was 0.01222mm and the maximum horizontal deformation of the die was 0.00096mm. This deformation led to a clearance change in the 8 cavity fine blanking tool. According to the simulation results, the calculated clearance was increased to a maximum of 45.9%, decreased to a minimum of 49.0%. Through the fine blanking experiment with the manufactured 8 cavity fine blanking tool, we demonstrated that 8 vane levers could be simultaneously produced by the 8 cavity fine blanking tool.