การวิเคราะห์การสั่นสะเทือนทางกลของระบบกังหันน้ำโรงไฟฟ้าลำรางชลประทาน เขื่อนแม่งัดสมบูรณ์ชล

Abstract

The EGAT Irrigation Valve Based Micro Hydro Project is a hydro turbine power plant located in the province of Chiang Mai that frequently suffers turbine bearing failure. The estimated expense of repairs is 11.34 million Thai baht. In order to identify solutions for fixing, improving, and engineering design, it is important to simulate the finite element analysis (FEA) to determine the root cause of the mechanical failure that resulted in the failure of the turbine bearing. The FEA modeling verified the model's accuracy by comparing it to an actual test using a variety of techniques, including generator support plate deflection, natural frequency comparison with a vibration test for critical speed, and modal analysis. According to the FEA results, the structure is sufficiently strong to support the weight. A safety factor of 2.89 is found. The range of values for the generator support plate deflection is 0.26 to 0.46 millimeters. A comparison of the FEA results and the analysis of the dial gauge indicator's measurement of the supported plate's deflection revealed an average mean absolute percentage error (MAPE) of 6.85 percent. A comparison of natural frequencies revealed that mode 1 had a frequency range of 10.23–11.36 Hz, while mode 2 had a frequency range of 13.30–14.57 Hz, with a MAPE of 6.81%. The comparison verified the acceptable accuracy of the FEA simulation model for analysis. According to the FEA of linear dynamic response, short-term damage to the turbine bearing was caused by shaft misalignment exceeding permissible specifications as a result of the structure's natural frequencies in modes 1 and 2, corresponding to the operation frequencies of the generator during start-up and shut-down. Hence, the structure was improved through the utilization of 3D design software and FEA simulation with the original data. The structure was conceptualized in the shape of a cylindrical structure that has reinforcement fins along its outer surface. It is able to improve the natural frequency of mode 1 to 37.57 Hz and that of mode 2 to 38.16 Hz, which is 200 percent higher than the rated operation frequencies and 41 percent higher than the maximum operational frequencies. The generator support plate's deflection can be reduced from 0.25–0.39 mm to 0.01 millimeters. Modifications to the newly designed structure were given approval in 2024. When the upgrades are finished, a natural frequency test will be executed using previously tested methods, allowing the newly designed structure to serve as a prototype for a small hydropower generator.