LM9000 Passive Clearance Control (PCC)

This paper describes the design of the free power turbine (FPT) of LM9000, in particularly the design of its passive clearance control system.

The LM9000 is an Aeroderivative Gas Turbine able to deliver a power in a range of 67-75MW with 42% simple cycle efficiency , derived from the proven GE90 jet engine fitted on the Boeing 777. Its core engine has many common parts with the GE90-115B, the most powerful commercial flight engine in the world.

What differs from GE90 is instead the booster that has been redesigned after removing the fan and the LPT that has been replaced by an intermediate pressure turbine (IPT) and by the FPT. The IPT drives the booster, while the FPT is a free low-pressure turbine designed for both power generation and industrial application, in particularly for LNG plants.

The LM9000 is an ideal solution to support grids with growing renewable sources, power your industrial needs, provide peaking power for hot days or give a reliable baseload to your isolated power island and it provides power in under 10 mins.

The FPT has been designed capable to operate for two intervals of 72000 hours and for this reason blades have thicker foils than aviation standards and subsequently disks are thicker to sustain higher pull loads but also the casing is thicker so to be able to contain a possible blade failure without releasing parts outside of the engine.

Even if made of thicker parts, the FPT has been designed still with very tight clearances. This has been possible with the help of a clearance control system. The PCC allows also casing to work at lower temperatures and therefore allows casing to meet the challenging requirement of 144000 hour of life.

The application of PCC in industrial application is not new. PCC are used on LM6000 and LMS100, but their field feedbacks are not always positive.

Design constraints, low manufacturing capability for production of few parts, high environment variability because PCC is located outside the GT, harsh environments and long periods of usage still make the design of this component challenging.

A big effort has been made by design team to meet product spec requirements. Design has been validated through extensive heat transfer and mechanical simulations. Part life but also blade and seal clearances have been estimated for all sorts of operating condition. A great investment has been made by company to mitigate all possible risks, including a dedicated test campaign.