Energy utilization from low-grade fuels of either fossil or renewable origin, or from medium-temperature heat sources such as solar, industrial waste heat, or small nuclear reactors, for small-scale power generation via steam cycles, can be reasonably enhanced by a simple technology shift. This study evaluates the technical feasibility of a compact power generation package comprising a steam turbine directly coupled to a high-speed alternator delivering around 8–12 MW of electrical power. Commercial or research-phase high-speed electrical generators at MW-scale are reviewed, and a basic thermodynamic design and flow-path analysis of a steam turbine able to drive such a generator is attempted. High-speed direct drives are winning new grounds due to their abilities to be speed-controlled and to avoid the gearbox otherwise typical for small system drivetrains. These two features may offer a reasonable advantage to conventional drives in terms of higher reliability and better economy. High-speed alternators with related power electronics are nowadays becoming increasingly available for the MW-size market. A generic 8 to 12 MW synchronous alternator running respectively at 15,000 to 10,000 rpm, have been used as a reference for evaluating the fundamental design of a directly coupled steam turbine prime mover. The moderate steam parameter concept suits well for converting mid-temperature thermal energy into electrical power with the help of low-tech steam cycles, allowing for distributed electricity production at reasonable costs and efficiency. Steam superheat temperatures below 350°C (660°F) at pressures of maximum 20 bar would keep the steam volumetric flow sufficiently high in order to restrain the turbine losses typical for small-scale turbines, while helping also with simpler certification and safety procedures and using primarily established technology and standard components. The proposed steam turbines designs and their characteristics thereof have been evaluated by computer simulations using the in-house code ProSteam and its sub-procedures AXIAL and VaxCalc, by courtesy of Siemens Industrial Turbomachinery and its steam turbine division located in Finspong, Sweden. The first results from this study show that high-speed steam turbines of the proposed size and type are possible to design and manufacture based on conventional components, and can be expected to deliver a very satisfactory performance at variable power output.

The SGT-400 industrial gas turbine was launched in 1997 and is now a proven and mature product in the market place for both power generation and mechanical drive applications. Rated at a nominal power of 12.9MW (electrical) and 13.4MW (shaft), this gas turbine has achieved sales of more than 180 units and exceeded 1,300,000 fleet operational hours. The natural progression for the SGT-400 was to build on this experience by developing a power enhancement from the current rating to a 15MW class of engine. This paper describes the key design features of the power enhancement along with the steps taken to validate the product in a risk controlled manner. Existing proven product design complemented by new technological advancements has enabled a 12% increase in gross power output for the core engine. The latest design tools and methods result in a 15MW engine offering the highest efficiency in its class. The design upgrades to the existing gas turbine are predominantly in the compressor section which has been given an increased inlet annulus area to accommodate the extra massflow through the core. The 15MW gas turbine core maintains common interfaces with the package as the current rating, so can be retrofitted in earlier installations if required.

In the past two decades the wind turbine industry has witnessed a considerable number of catastrophic accidents, many of which were due to gearbox failure. Ever increasing power ratings at decreased rotor speeds result in rotor torques of some million Nm. This imposes tooth loads and planet/pinion bearing loads on the order of a hundred tons within the first step-up stage. Such heavily loaded gearboxes, correctly (or rather innocently) designed according to the relevant codes, can be self-destructive. Due consideration should be given to the elastic environment in which the gears exist. Otherwise, appreciable, unsymmetrical/unequal elastic deformations in unwanted directions lead to gear tooth edge loading, in addition to overloading the bearing(s) near that edge. Designers of wind turbine gearing have in recent years identified several concepts and measures to be taken for counteracting the asymmetry of elastic deformations or mitigating their effects. In addition to giving a brief survey of such new design concepts, this paper suggests the use of selected types of curved-tooth cylindrical gears (so-called C-gears), primarily for their self-aligning capability; they allow four degrees of freedom (4-DOF), in contrast to the 3-DOF spur and helical gears and the 2-DOF double-helical gears. In addition, these gears offer a unique set of further advantages. When used in at least the most heavily loaded, first step-up stage, the design will be rendered quasi-exactly constrained; largely tolerant of misalignment due to elastic deformations, and the gearbox reliability should be improved, by design.

The desire to maintain power plant profitability, combined with current market fuel gas pricing is forcing power generation companies to constantly look for ways to keep their industrial gas turbine units operating at the highest possible efficiency. Gas Turbines Operation requires the compression of very large quantities of air that is mixed with fuel, ignited and directed into a turbine to produce torque for purposes ranging from power generation to mechanical drive of pumping systems to thrust for air craft propulsion. The compression of the air for this process typically uses 60% of the required base energy. Therefore management of the compression process efficiency is very important to maintain overall cycle efficiency. Since fouling of turbine compressors is almost unavoidable, even with modern air filter treatment, and over time results in lower efficiency and output, compressor cleaning is required to maintain gas turbine efficiency.

The need for increased design flexibility and reduced weight and volume for electric power generation infrastructure has driven an increased interest in the use of high speed generators directly driven by gas turbine prime movers for both military and commercial power generation applications. This transition has been facilitated by the use of dc distribution and recent advances in the performance of solid state power conversion equipment, enabling designers to decouple the power generation frequency from typical 60 Hz ac loads. Operation of the generator at the turbine output speed eliminates the need for a speed reduction gearbox and can significantly increase the volumetric and gravimetric power density of the power generation system. This is particularly true for turbines in the 3 to 10 MW power range which typically operate with power turbine speeds of 7,000 to 16,000 rpm. The University of Texas at Austin, Center for Electromechanics (UT-CEM) is currently developing a 3 MW high speed generator and turbine drive system for a hybrid vehicle propulsion system as a part of the Federal Railroad Administration’s Advanced Locomotive Propulsion System (ALPS) Program. The ALPS system consists of a 3 MW turbine/alternator prime mover coupled with a 480 MJ, 2 MW flywheel energy storage system. Although designed as the prime mover for a high speed passenger locomotive, the compact turbine/alternator package is well suited for use in marine applications as an auxiliary turbine generator set or as the primary propulsion system for smaller vessels. The ALPS 3 MW high speed generator and turbine drive system were originally presented at the ASME Turbo Expo 2005 [1]. This follow-on paper presents the results of mechanical spin testing and No-Load electrical testing of the high speed generator and the Static Load testing of the generator and turbine drive system at NAVSEA (Philadelphia, PA) with a fixed resistive load. The generator has been tested to a 1.5 MW power level in the Static Load procedures and is being prepared for the final test phase to include dynamic power exchange with the flywheel.

ASME codes cover testing of all types of gas turbines between the ASME PTC 22 and ASME PTC 55, which will be available by 2008. The testing of gas turbines in land-based units is handled in PTC 22, while the testing of Aircraft gas turbines is handled in PTC 55. The paper addresses the development of ASME Test Codes, and the testing of gas turbines for aircraft, power generation and mechanical drive gas turbines highlighting some of the many differences in the characteristics of both engines.

New low pressure (LP), stages for variable speed, mechanical drive and geared power generation steam turbines have been developed. The new blade and nozzle designs can be applied to a wide range of turbine rotational speeds and last stage blade annulus areas, thus forming a family of low pressure stages—High Speed (HS) blades and nozzles. Different family members are exact scales of each other and the tip speeds of the corresponding blades within the family are identical. Thus the aeromechanical and aerodynamic characteristics of the individual stages within the family are identical as well. Last stage blades and nozzles have been developed concurrently with the three upstream stages, creating optimised, reusable low pressure turbine sections. These blades represent a step forward in improving speed, mass flow capability, reliability and aerodynamic efficiency of the low pressure stages for the industrial steam turbines. These four stages are designed as a system using the most modern design tools applied on Power Generation and Aircraft Engines turbo-machineries. The aerodynamic performance of the last three stage of the newly designed group will be verified in a full-scale test facility. The last stage blade construction incorporates a three hooks, axial entry dovetail with improved load carrying capability over other blade attachment methods. The next to the last stage blade also uses a three hooks axial entry dovetail, while the two front stage blades employ internal tangential entry dovetails. The last and next to the last stage blades utilize continuous tip coupling via implementation of integral snubber cover while a Z-lock integral cover is employed for the two upstream stages. Low dynamic strains at all operating conditions (off and on resonance speeds) will be validated via steam turbine testing at realistic steam conditions (steam flows, temperatures and pressures). Low load, high condenser pressure operation will also be verified using a three stage test turbine operated in the actual steam conditions as well. In addition, resonance speed margins of the four stages have been verified through full-scale wheel box tests in the vacuum spin cell, thus allowing the application of these stages to Power Generation applications. Stator blades are produced with a manufacturing technology, which combines full milling and electro-discharge machining. This process allows machining of the blades from an integral disc, and thus improving uniformity of the throat distribution. Accuracy of the throat distribution is also improved when compared to the assembled or welded stator blade technology. This paper will discuss the aerodynamic and aeromechanical design, development and testing program completed for this new low pressure stages family.