Aero-structure interaction during turbomachinery blade design has become an important area of research due to its critical applications in aero engines and land based gas turbines. Studies reveal that a certain mistuning leads to stress build up through mode localization under operating conditions. This paper deals with comparative case studies of aero-structure interaction for free standing and various laced LP blade configurations of a gas turbine. The lacing wire provides better structural integrity as it is more aerodynamic and feasible when compared to cases of free standing blades without lacing wires. Hence calling for the optimum positioning checks at ¼ th , ½, ¾ th and combined positioning at ¼ th and ¾ th along the length of LP compressor blades. The lacing wire of both circular and elliptical cross sections are considered for comparative study for better aerodynamic performance. Assuming 100% fixity at blade root, the study involves critical parametric evaluations involved in achieving mechanical integrity in airfoil design and blade platform design. Mechanical integrity involves stress checks, frequency margins, Campbell Diagram, gross yield stress, Stress Stiffening and Spin Softening of blades and so on, for design and off-design conditions for a given stage efficiency of 93% in an ideal LP compressor of a gas turbine engine.

Heavy-duty gas turbines are designed to deliver maximum performance within their respective technology class and emissions limits. In order to achieve performance goals consistent with hot section durability constraints, it has become more critical than ever for engineers to have an economical, dependable, and accurate measurement of the average exhaust gas temperature and the associated profiles. Simple thermocouples “rakes” have been used for many years to meet the basic need of measuring planar average temperature. In addition, recent testing experience has shown that the measured radial temperature profile data from these same “rakes” can play a key role in the diagnosis of performance issues and also in the characterization of hardware upgrades. For example, high technology hot section spin-offs from F, G, and H class turbines have been applied as upgrades to older B and E class turbines with dramatic impact on the exhaust temperature pattern. Another example has been the use of pressure/temperature exhaust “rakes” in F class turbines to diagnose changes in the radial temperature profile that result from combustion system upgrades. In both cases, the careful measurement and interpretation of these temperature patterns is crucial to the proper setting of control algorithms that govern performance levels and exhaust emissions. Advances in the design and arrangement of exhaust thermocouple rakes, and in the analysis methods used to interpret the resultant test data, are presented. Several recent cases of using rakes to diagnose performance issues and to characterize the temperature pattern for the purpose of optimizing control settings are discussed.

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.

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.