Blog 3

 The team's Gantt chart has Milestone 1 and Milestone 2 listed for October 28 – November 11.  Currently, the team has completed a vibration analysis on the shaft, weight, and balance of the shaft, and compared the vibration data with the experimental data collected through the modal hammer. Diversity Hires has accomplished the initial stage of the Overspeed trip test system, focusing on vibration analysis and calculations. This specific phase was prioritized to show whether the rotor shaft exhibited characteristics of a rigid or flexible rotor. Understanding this distinction is critical: rigid rotor shafts possess a natural frequency higher than the rotor's operating speed, ensuring minimal vibration, while flexible rotor shafts with a natural frequency below the operating speed experience excessive vibration when reaching that critical rpm. To establish the nature of the rotor shaft, the team referenced the 'International Journal of Advance Research in Science and Engineering' to derive Equation 1, which calculated the shaft's natural frequency for comparison against the rotor's operating speed. This milestone was indispensable, enabling proactive measures to address potential vibrations in the event of a flexible rotor shaft.

Equation 1. The formula for critical speed

The team validated the dimensions and measurements of the shaft due to the Shafts step design and various traverse holes for the mounting of varied size Overspeed mechanical trips, as illustrated in Figure 1. This was done to guarantee that the shaft's moment of inertia reported by Sulzer was precise when calculating. The moment of inertia is important because it represents an object's resistance to rotational deformation. Diversity recruits determined the shaft's moment of inertia after validating the specifications by testing the shaft at Sulzer. This was done by subtracting the moment of inertia of the material taken from the shaft by the perforations from the moment of inertia of the shaft as a whole. 

Figure 1. Engineering schematic of shaft

Furthermore, the frequency analysis performed by the team was confirmed by the project engineer with whom they are collaborating at Sulzer. The shaft was rigorously examined at several spots using a modal hammer to determine its natural frequency. The hammer is outfitted with a force sensor that provides a voltage signal proportional to the excitation force, allowing the natural frequency or excitation force to be detected throughout the test. According to Sulzer, the estimated natural frequency and the experimental natural frequency were within an acceptable range of one another. This validated the team's estimates and accomplished the majority of Milestone 1. Additionally, the team referred to the ISO 1940 standards to ensure the weight and balance of the shaft fall within the allowable residual of the unbalanced shaft. The team determined that the shaft used for this project has a grade of 2.5. This was determined by looking at the grade quality of a compressor shaft.  After looking at the grade quality, the team referred to the balance quality graph and found the maximum allowable residual is 1500 gmm/kg. The team then inserted the shaft into a balance machine provided by Sulzer to ensure the shaft met the maximum allowable residual. As the team moves to Milestone 2, the current task in progress is designing a bearing housing on Solidworks. The team has already designed a 3D model of the shaft as shown in Figure 2.

 

Figure 2: 3D model of shaft

Bearing housings are essential components that ensure the optimal performance and longevity of bearings. Primarily, they shield bearings from environmental contaminants such as dust and moisture, safeguarding against potential damage and degradation. Moreover, these housings offer crucial support and alignment, maintaining stability and precise positioning for the bearings to operate efficiently, reducing friction, and preventing premature wear. Additionally, they aid in dissipating the heat generated during bearing operation, preventing overheating and damage. Some housings also feature seals to retain lubrication within the bearings and allow for easy maintenance, enabling swift inspection, adjustments, or replacements when necessary. 

One of the challenges the team faces in the upcoming weeks is scheduling time to meet with the engineers at Sulzer. The engineers that the team is working with are field engineers. The field engineers at Sulzer are currently on call and away from the office. Additionally, another challenge the team has identified is designing a bearing housing in SolidWorks. Ensuring dimensional compatibility between the housing and the shaft, managing complex geometries within the housing design, and aligning it accurately with the shaft model requires the team to take accurate measurements. Material selection for the housing, considering manufacturing feasibility, and structural analyses to verify its capacity to withstand operational forces are critical hurdles. Additionally, creating a robust interface and seamless assembly between the housing and shaft demands careful design and collaborative efforts to overcome these challenges, the team has set up Microsoft team meetings with the engineers at Sulzer to receive guidance and answer any questions the team has. The team has also planned to use the week of November 13, 2023, to take measurements of the bearings as well as conduct research into different bearing house designs. for the period of November 11 - November 25, the team hopes to complete Milestone 2 and begin Milestone 3. Milestone 2 involves the team compiling 3D CAD drawings of the bearing, bearing housing, and test fixture. To have a complete model of the test fixture, the components such as the shaft, bearing housing, and bearings, need to be designed and assembled into the final test fixture. The beginning of Milestone 3 involves the team establishing supplier relations to find bearings that fit within the budget of $10,000 allocated by Sulzer.