LM9000 Free Power Turbine Validation: Advanced Test Bench

In Oil&Gas framework, both for on-shore and off-shore applications, the need of innovative turbomachineries in terms of efficiency, weight, maintenance and versatility is quickly growing. In this scenario, the union of the best solutions from aeronautical and Oil&Gas worlds can represent a technological advantage. This is the idea behind the LM9000, the latest BHGE 67-75 MW gas turbine.

The LM9000 is composed by a gas generator, derived from the GE90-115B twin shaft turbofan, coupled to a free power turbine and it is entirely designed with aviation design criteria. Both the gas generator and the free power turbine use rolling element bearings that contribute to reduce the weight and the complexity of the engine and its auxiliary system architecture. The free power turbine (FPT) represents the new element and it allows delivering a flexible energy supply both for mechanical drive and power generation applications.

For the considerable dimensions, weight and characteristics of the FPT, it was necessary a large effort to build a dedicated test bench that is in a class by itself in the Oil&Gas industry. The aim of this paper is to describe the design solutions adopted to realize an advanced test bench to validate the FPT sump area.

The test rig is in 1:1 scale and includes the main FPT components such as the casing, the labyrinth seals and a mock-up of the shaft mounted on three roller bearings. The three tons shaft is driven by an electric motor able to investigate a wide range of speeds in both sense of rotation. A set of hinges and servo-actuators can move the test rig around 2 axes to simulate pitch and roll angles in off-shore applications. The whole structure is instrumented with a large variety of sensors including also telemetry and optical fibers for lube oil levels in the drain chamber. It was also possible to simulate design and off-design conditions including extreme values of oil pressure, oil temperature, pitch and roll angles, shaft speed, thrust load and buffering air. The results were mainly evaluated in terms of bearing performances, lube oil levels, part temperatures, lube oil and buffering air system.

Concluding, the test bench was crucial to validate the sump configuration for on-shore and off-shore applications and to define the inputs range in which the FPT will operate properly and safely. In addition to that, the test rig provides a high flexibility to perform complex tests for different configurations by reason of its 20 tons payload capability, considerable volume for the test article installation and flexible modular design.