The Development of Turboexpander-Generators for Gas Pressure Letdown Part 3: Design Validation

Abstract

This paper is a follow-up to GT2021-60125 (“Design and Analysis”) and GT2021-60317 (“Economic Analysis”), which collectively covered the design, analysis, and economics of innovative Turboexpander Generators (TEG) used in pressure letdown (PLD) applications. This paper describes the testing data of a family of TEGs, 280 kW and 125 kW, for natural gas pressure letdown applications. The TEGs are supported by active magnetic bearings (AMB). Machine design for the two TEGs is very similar for ease of manufacturing and control system design, with wheel design being the primary difference. A comprehensive controls analysis and AMB closed-loop dynamics study were presented earlier. This paper compares predicted and measured transfer functions along with the pre and post brush seals installation data. Drop testing results on the touchdown bearing are shown along with the full-speed touch-down events. Active front-end variable speed drive (VSD) design is presented along with the power generation results. Finally, measured force vs deflection data is presented for a tolerance ring, used as the resilient element for the touchdown bearings.