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The following paper provides an overview of GE's H SystemTM technology, and specifically, the design, development, and test activities associated with the DOE Advanced Turbine Systems (ATS) program. There was intensive effort expended in bringing this revolutionary advanced technology program to commercial reality. In addition to describing the magnitude of performance improvement possible through use of H SystemTM technology, this paper discusses the technological milestones during the development of the first 9H (50Hz) and 7H (60 Hz) gas turbines. 9 DE-FC21-95MC31176 Combustion The H SystemTM can-annular combustor system is a lean pre-mix Dry Low NOx (DLN) system, similar to the GE DLN combustion systems currently used in FA-class service. The H DLN 2.5 combustion system has demonstrated single digit NOx and CO levels at full power conditions in the GEAE full scale test rig. This technology is being fed back into the GE combustor design database. In addition, the uniform flow delivered by the tri-passage diffuser was confirmed during the combustor test program. The thermal barrier coating (TBC) coated liner and transition piece both required advances in design and part fabrication. Due to the high temperatures encountered, the material for both was changed to aill-222 from Nimonic-263. TBC was added to both parts to improve part life. The heat treatment process and TBC application methods developed will be utilized in other high-temperature applications. Rotor System An analytical computer structural model (using ANSYS) was constructed to develop a response surface for "backbone bending" due to bottom-to-top casing temperature gradients. These gradients distort the case relative to the unit rotor, causing rubbing of the compressor airfoil tips. Using the case distortion model, a refined understanding of the casing behavior was obtained, leading to a redesign of the air ventilation system around the exterior of the gas turbine. This analysis and design changes are being done for the rest of the GE Power Systems gas turbine product line to allow blade clearance reductions and corresponding increased performance. 13 DE-FC21-95MC31176 Conceptual Design The GE H SystemTM is a combined cycle plant. The hot gases from the gas turbine exhaust proceed to a downstream boiler or heat recovery steam generator (HRSG). The resulting steam is passed through a steam turbine, and the steam turbine output then augments that from the gas turbine. The output and efficiency of the steam turbine's "bottoming cycle" is a function of the gas turbine exhaust temperature. For a given firing temperature class, 2600°F / 1430°C for the H SystemTM, the gas turbine exhaust temperature is largely determined by the work required to drive the compressor, that is, in turn, affected by the "compressor pressure ratio." The H System'sTM pressure ratio of 23:1 was selected to optimize the combined cycle performance, while at the same time allowing for an uncooled last stage gas turbine bucket, consistent with past GEPS practice. The 23: 1 compressor...