Solar Turbines Alignment Mechanism

Designing a High Precision Linear Positioning System

For Gas Turbine Alignment

Spring 2021 MAE 156B Sponsored Project

University of California, San Diego

Sponsored by Solar Turbines: Lucas Massey, Matt Ostiguy, Gregor Robertson

About Solar Turbines:

Solar Turbines is a leading provider of energy solutions that features an extensive line of gas turbine-powered compressor sets, mechanical drive packages, and generator sets. Solar manufactures the world’s most widely used family of mid-sized industrial gas turbines. Currently, Solar is in the design process for designing a new mounting system for their T-250 engine which measures 28 ft. in length and weighs approximately 32,000 lbs.

The Problem:

Currently, maintenance on a Solar Turbines machine can take up to 3 days. Much of this time is spent ensuring proper alignment between the turbine output shaft, and the gearbox input shaft. If the two shafts are not aligned, damage inducing vibration can be introduced to the turbine and can eventually lead to engine failure. In an effort to greatly increase the efficiency of the alignment process, Solar Turbines has recently been designing a new, six-strut mounting design, which can move the turbine in all 6 degrees of freedom. Since the struts can not extend on their own, they are being designed to travel linearly in one degree of freedom in order to adjust the overall orientation of the engine. With the kinematics of the overall position of the turbine in relation to the new six-strut mount design already solved for, Solar engineers are in need of a design of a linear positioning system that is cable of unlocking, moving into position, and locking back into place with high degrees of accuracy while also supporting forces up to 48,000 lbf per strut.

Project Goal:

To investigate various linear motion devices in order determine the best candidate for Solar Turbines. The new motion device must be capable of accuracy and precision of 50 thousandths of an inch. Our team will produce a recommendation to Solar Turbines, as well as a Request for Quote which Solar Turbines can submit to various vendors.

So What?

Alignment is essential for ensuring the full operational life of rotating machinery especially at the scale of the T-250 engine, as even the slightest misalignment can cause undesirable vibrations that can potentially damage to the machine. Having a alignment mechanism that can efficinetly adjust each strut foot independently at high degrees of accuracy is one of the major cruxes of Solar's new six strut mount design.

In a Nutshell

At the core of this project’s problem is a relatively simple free body diagram of the strut foot bearing the load from the turbine with an accompanying pushing force acting to adjust the position of the foot. Note that this FBD is representative of the aft strut which is exposed to the worst case loadings and is the focus of this project. F denotes the reaction force from the turbine applied axially through the aft strut. During the alignment process, F is equal to 12,000 lbf; however, when the turbine is in operation and the foot is locked in place, F is equal to 48,000 lbf. Fr denotes the friction force between the foot and base that provides linear motion. N is the normal force and Fpush is the required pushing force (thrust) needed in order to overcome static friction and adjust the position of the foot.