Manuele Bigi

New high-temperature seal system for increased efficiency of gas turbines

With increasing fuel prices and significant pressure to reduce emissions, the efficient use of fuels in gas turbines is gaining ever more attention. Abradable seals in gas turbine compressors have contributed to improved efficiencies for quite some time now. To further enhance efficiency, current efforts focus on the seals in one of the hottest sections of the engine, the first turbine stage. Sulzer Metco and GE have designed and tested a new high-pressure turbine abradable seal system in the framework of a European consortium project led by GE Oil & Gas. In the scope of this project, Sulzer Metco developed a novel ceramic coating for application by atmospheric plasma spraying (APS). An engine test verified performance and economic advantages of the new seal system. The measured improvements in engine performance exceed the expected gains as predicted by model calculations.

Mechanical Performance of a Two Stage Centrifugal Compressor under Wet Gas Conditions

As subsea compression becomes a vital technology to the successful production of gas reserves in the North Sea, several technology issues will come to the forefront of the oil and gas industry. One of these important subjects is the capability to compress gas which includes a significant amount of liquids. Compressing wet gas requires knowledge in areas such as the prediction of turbomachinery performance with the mixed phase flow as well as the mechanical reliability of machinery in the same environment. This paper presents experimental results from a wet gas test campaign which, among other goals, is focused on characterizing the mechanical performance of a two stage compressor operating under wet gas conditions. Various mechanical parameters are monitored in the test program including rotor radial and axial vibration, rotor thrust, and shaft torque. A full array of wet gas conditions are tested with a suction pressure of 20 bar (300 psia) and liquid volume fractions in the range of 0.5 to 5%. The operating fluids are air and water, and the two stage compressor is operated at three speed lines ranging from high flow to low flow conditions. Significant variations are noted in the axial thrust, axial vibration and shaft torque. Thrust variations range from seemingly neutral thrust conditions at very low water injection rates to significant thrust increases (as compared to dry condition) for very high water injection rates. Rotor axial vibration is characterized by large amplitude and very low frequency, especially for the case in which the rotor thrust is balanced by the water injection. During higher levels of water injection, rotor axial vibration is generally characterized by relatively large amplitude and slightly higher frequency, although still very low as a percent of running speed. Variations in radial vibration are also noted, but to a much lesser extent.

Measured Performance of Two-Stage Centrifugal Compressor Under Wet Gas Conditions

The oil and gas industry is moving forward to access the most remote gas reserves and enhance the exploitation of the existing installation or postponing their tail-end. To achieve these accomplishments several technology challenges are being unveiled. In topside upstream application both offshore and onshore, one important technology issue is the capability to compress gas with a significant amount of liquids and it assumes a special interest in case of the facilities revamping. Nevertheless is in the subsea environment where this technology issue becomes really challenging. In order to properly design and size a compressor/motor system for subsea wet gas compression, one must be able to adequately predict the compressor performance with mixed phase flow.This paper presents the results from an experimental test program which investigated the performance of a centrifugal compressor at various wet gas conditions with elevated suction pressure. Performance tests are completed on a two stage centrifugal compressor with a mixture of air and water at suction pressures of 20 bar (300 psi). The compressor is subjected to flow with liquid volume fractions ranging from 0 to 5% along three speedlines.The performance measurements are made in accordance with ASME PTC-10 specifications with an additional torque measurement on the shaft between the compressor and gearbox. At each test condition, once the liquid is injected in the air flow, an increase in pressure ratio occurs. This testifies the compressor is still able to work in presence of water. However, increasing the amount of liquid injected a decreased polytropic head together with an increased absorbed actual power by the compressor cause a deterioration of its efficiency. Moreover when liquid is introduced into the flow, the discharge temperature of the compressor reduces significantly.The performance results and trends mentioned above are reviewed in the detail in this paper.Copyright

Clearance Reduction and Performance Gain Using Abradable Material in Gas Turbines

An improvement in the energy efficiency of industrial gas turbines can be accomplished by developing abradable seals to reduce the stator/rotor gap to decrease the tip leakage flow of gases in the hot gas components of the turbine. “ABRANEW” is a project funded by the European Commission aimed at developing a high temperature abradable material capable of controlled abrasion and resistant to erosion and oxidation. In order to define the basic parameters such as the component shape, the existing gap, the expected gap reduction, the seal thickness and other geometric parameters, a comprehensive review of the design of the blade/shroud/casing system was performed.Copyright