Bernard Arthur Couture

Wear Prediction of Strip Seals Through Conductance

Labyrinth seal assemblies are often used to reduce gas and/or steam leakage in turbines. Caulked-in continuous strip seals are one of the common forms of seals employed on both the rotating and stationary components of turbines. Labyrinth seals perform best when minimum clearances are achieved during the steady state operation of the turbine. However, the design of the turbine and its operation during transient periods of start-up, shut-down and hot re-start often result in interference between the seal components. In the case of the strip seals, this leads primarily to wear of the strip, which in effect adds to leakage. The aim of this paper is to show that strip tip heating and melting during the rub is the main mechanism of wear in the strip. Hence thermal conductivity through the strip and into the body mass in which it is caulked is the primary controlling factor in seal wear. This paper will discuss the use of thermal conductivity and geometry of the strip in predicting wear during high speed rubs against a proprietary material. A close correlation between calculated and experimental strip seal wear data with a number of seal alloys will be demonstrated. Test data will indicate that material properties such as tensile strength and hardness have a minor effect on the wear behavior of continuous seal elements during high-speed rubs.Copyright

Active Retractable Seals for High-efficiency Steam Turbines

*† ‡ § ** Rotor end leakage at the high-pressure section accounts for about 20% of the total leakage loss in a steam turbine. Advanced sealing technology at end packing locations can bring about significant improvement in overall turbine efficiency. In this paper, we propose an active seal, which can be retracted during rotor transients. As a result, tighter clearances can be designed and preserved during the life of the turbine. The concept is an extension of commonly used Variable Clearance Positive Pressure Packing technology, where the seal opens and closes depending on the pressure differential across it. The proposed extension involves the addition of a bypassing mechanism across the seal, which can actively control the pressure differential and hence the opening and closure of the seal. The design concept was initially demonstrated in a subscale test rig. Operational validation was performed through extensive testing on a full-scale rig.

Dry, Low Emissions for the H’ Heavy-Duty Industrial Gas Turbines: Full-Scale Combustion System Rig Test Results

The lean, premixed DLN2.5H combustion system was designed to deliver low NOx emissions from 50% to 100% load in both the Frame 7H (60 Hz) and Frame 9H (50 Hz) heavy-duty industrial gas turbines. The H machines employ steam cooling in the gas turbine, a 23:1 pressure ratio, and are fired at 1440 C (2600 F) to deliver over-all thermal efficiency for the combined-cycle system near 60%. The DLN2.5H combustor is a modular can-type design, with 14 identical chambers used on the 9H machine, and 12 used on the smaller 7H. On a 9H combined-cycle power plant, both the gas turbine and steam turbine are fired using the 14-chamber DLN2.5H combustion system. An extensive full-scale, full-pressure rig test program developed the fuel-staged dry, low emissions combustion system over a period of more than five years. Rig testing required test stand inlet conditions of over 50 kg/s at 500 C and 28 bar, while firing at up to 1440 C, to simulate combustor operation at base load. The combustion test rig simulated gas path geometry from the discharge of the annular tri-passage diffuser through the can-type combustion liner and transition piece, to the inlet of the first stage turbine nozzle. The present paper describes the combustion system, and reports emissions performance and operability results over the gas turbine load and ambient temperature operating range, as measured during the rig test program.Copyright

Latest Developments In Wear Prediction of Strip Seals Through Conductance

This paper discusses the latest developments in the ability to predict wear of strip seals in turbine engines. Caulked-in continuous strip seals are a common form of seals employed on both the rotating and stationary components of gas and/or steam turbines. These seals perform best when minimum clearances are achieved during the steady state operation of the turbine, and when a sharp tip profile can be maintained. However, interference between the stationary and rotating seal components often occurs during transient periods of startup, shutdown and hot re-start. In the case of the strip seals, this leads primarily to wear of the strip, which increases leakage and reduces turbine performance. The aim of this paper is to present the latest findings showing that thermal conductivity through the strip and into the body mass in which it is caulked are the primary factors in controlling seal wear within the range of materials and parameters tested. This paper will discuss the latest experimental validation of a model that uses thermal conductivity and geometry of the strip in predicting wear during high speed rubs against a proprietary material.