Aerobatic aircraft have become popular for the training of military pilots, and nowadays an increasing number of such airframes are being developed. Modern turboprop engines provide high performance allowing the pilots to get similar handling characteristics to military jet aircraft engines. Prior to the availability of high performance turboprops, the basic pilot training was conducted using jet aircraft. Furthermore, the introduction of electronic control systems on last-generation turboprop engines enables single lever control, making it an ideal candidate for this type of aerobatic and training airframes. This new type of engine operation is however accompanied by several challenges from the point of view of the engine design and installation aerodynamics. GEAC has gone through a complex design process, in cooperation with the airframer, to validate the design of a new aerobatic aircraft inlet in the context of developing an aerobatic version of the H80 engine. In order to ensure a) surge-free operation, b) optimal engine performance and c) effective ice/FOD separation in inclement weather conditions and during any kind of aerobatic maneuver, the team has done extensive CFD predictions of the flow behaviour, performance/operability studies and finally a ground test campaign. First, a back-to-back comparison of the aerobatic inlet geometry versus a reference commuter inlet geometry was conducted. Then, flight conditions were simulated in calm and crosswind environments. Distortion patterns were examined using in-house developed tools and the diverse sources of distortion were identified. One of the results is the introduction of geometry improvements to guarantee improved performance and extended engine operability range. Advanced propeller modeling techniques were introduced and benchmarked in order to have the most exact representation of the propeller aerodynamic effect on inlet flow. Finally, a test campaign was conducted for validation purposes. An exhaustive instrumentation, data acquisition system and detailed test program were developed to validate CFD methods and assumptions made during the design phase, and to raise our confidence in the flight conditions simulation results.

Nowadays total inlet temperature of gas turbine is far above the permissible metal temperature; as a consequence, advanced cooling techniques must be applied to protect from thermal stress and to reduce the risk of creep failure, oxidation and corrosion of components located in the high pressure stages, such as first vane. Film cooling has been widely used to control temperature of high temperature and high pressure vanes. In a film cooled vane the air taken from last compressor stages is ejected through discrete holes to provide a cold layer between hot mainstream and turbine components. A comprehensive understanding of phenomena concerning the complex interaction of hot gases with coolant flows in a vane passage plays a major role in the definition of a well performing film cooling scheme. The aim of this study is the measurement of adiabatic effectiveness on the first stage vane of a heavy duty GT by means of coolant concentration technique based on Pressure Sensitive Paint (PSP). The investigation of coolant distribution on airfoils and platforms was done in order to make feasible possible optimizations and to validate numerical design tools. The experimental analysis was performed on a static test article replicating an annular sector made up of two cooled airfoils and three passages. An actual first stage vane (scale 1:1) with complete internal cooling scheme has been tested at different coolant conditions and imposing two values of density ratio (DR = 1.0;1.5). Film protection was generated by a showerhead on the leading edge and by cylindrical holes on pressure and suction side and on the platforms; finally a cutback with elongated pedestals was employed for the protection of the pressure side trailing edge. Results, reported in terms of detailed 2D maps of film cooling effectiveness and averaged trends, point out the effect of coolant-to-mainstream mass ratio and density ratio. Beyond the results obtained in this specific vane geometry, the use of PSP was proven to be a promising technique for direct measurements on real geometries: as a matter of fact, the opportunity to get detailed results of pressure and adiabatic effectiveness distributions is of outstanding importance for the design and optimization of vanes and blades cooling systems.

Given the constant increase in world energy demand, gas turbine operators are continuously looking for turbo-machinery improvements, both in terms of increased power and extended maintenance intervals, limiting, as much as possible, the downtime for upgrading. In 2006, GE Oil & Gas engineers launched the Power Crystal™ development program to enhance the output power or extend the maintenance interval of the MS5002C and D heavy duty gas turbines. This effort resulted in an upgrade kit potentially to be installed during a standard major inspection, which include a single crystal material 1st stage high pressure turbine blade and additional improvements, such as new coatings for combustor hardware and improved cooling of the 1 st stage high pressure turbine nozzle and 1 st stage high pressure turbine wheel. The upgrade kit was validated through an extensive test campaign, which included test-rig component tests in advance of the First Engine to Test (FETT). All critical-to-quality parameters of the gas turbine were investigated, such as turbine gas path component temperatures and stresses, performance and operability. This paper describes the background for the upgrade, discusses the new kit features, how the test program was built and conducted, and reports the experience accumulated on the gas turbine during the initial field operation.

The MS5002E is a 32 MW-class, two-shaft gas turbine suitable for both mechanical and generator drive applications. Its design, based on the latest heavy-duty gas turbine technology, delivers 36% of thermal efficiency and maintains NOx emissions below 25 ppm. After an extensive validation program performed on the First Engine to Test (FETT), the first production unit was shipped to the Yara fertilizer company for its ammonia and nitrate fertilizer plant at Sluiskil in the Netherlands. Yara is the world’s largest supplier of crop nutrients, with sales to more than 120 countries. The unit entered into commercial operation on November 2007, supporting Yara in meeting its environmental plan by replacing an existing, less efficient gas turbine. The engine is operated in generator drive mode, producing 30+ MW of electric power and 50 tons per hour of steam, which is used in the plant process. As of this writing, the unit has exceeded 18,000 hours of continuous service. The performance results and reliability are unusually high for a new machine. This article reports the experience accumulated on the gas turbine during field operations, based both on the day-by-day activity (condition monitoring) and on the special introductory inspection program carried on to date. The improvements already introduced and being introduced on subsequent fleet units are discussed as well. The day-by-day monitoring is supported by an extensive quantity of data collected from the machine and sent via Internet connection to the GE Oil&Gas Remote Monitoring & Diagnostic Center in Florence.

CO 2 compression significantly contributes to the overall efficiency penalty and capital cost increase resulting from CO 2 capture. Performance improvement measures for this process step hence have the potential of considerably improving the overall economic picture for CO 2 -lean power generation from fossil fuels. The present paper gives an insight into the thermodynamics of CO 2 compression in a natural gas combined cycle power plant with post-combustion CO 2 capture. The work aims at gaining a better understanding of the boundary conditions, thermodynamic limitations, and performance entitlement governing the CO 2 compression process. With the help of process simulation, different technically feasible strategies for compressing CO 2 are evaluated, quantified, and compared against their thermodynamic entitlement; the compression power reduction and the maximum cost allowable for the performance improvement measures suggested are estimated.

GE Oil&Gas has recently launched a new heavy-duty gas turbine, the MS5002E, which underwent an extensive theoretical and experimental study on fuel flexibility. Today, fuel flexibility is one of the most challenging requirements in the Oil&Gas market. The fuel flexible operation demands a wide variety of assessments, ranging from rig tests of the combustor to theoretical consolidation of the results. The present paper describes the used methodology to increase the capabilities of burning diverse gaseous fuels, at fixed geometry. It analyzes all factors affecting the operation of the combustor with the goal to identify and extend the boundaries. Such boundaries are a result of multiple variables, like resistance to flashback and autoignition, emissions, pressure pulsations and capability of igniting. Flashback is when the reaction velocity overtakes the flow velocity and the flame moves back to the fuel injection points, threatening the integrity of the hardware. The resistance of the MS5002E to flashback and flame holding was evaluated by performing extensive experiments on a single fuel nozzle. Flame holding test results were then used to develop a transfer function for the prediction of the flame holding behavior of different mixtures. Another variable of interest is the resistance to autoignition: MS5002E took advantage of previously defined transfer functions from GE Energy that estimate the temperature above which a given mixture is likely to autoignite, at fixed pressure. Since the MS5002E is a DLN machine, it was also necessary to exclude the possibility of lean-blow-out in the whole operating range: dedicated tests on a single-can basis were used for this scope. Emissions and pressure pulsations were extensively measured on a single-can basis, since these parameters are fundamental for a lean premixed combustor. For particular mixtures, like those with high content of inert gases, the capability of igniting repeatably and reliably is an additional requirement that needs experimental validation. The combination of all the aforementioned variables determines the composition limit of the fuel mixture that the machine can tolerate. As a result of all the assessment, it was possible to achieve an increase in the maximum allowable concentrations for the following constituents: propane (up to 20%), nitrogen (up to 20% with no modifications to the control algorithms; up to 25% with minor modifications to the control algorithms) and hydrogen (up to 5%). Future tests will deliver increased capabilities also for ethane and butane.

Due to the substantial increase in sources of gas, natural gas interchangeability is a key subject in the industry today. The extensive pipeline network means that natural gas arriving at appliances, boilers, burners and power plant turbines could come from anywhere. Fuel compositions vary from one source to another. Moreover, most recently, Liquefied Natural Gas has emerged as a major source and the composition of gas derived from LNG substantially differs from the natural gas one. In Dry Low NOx (DLN) systems, those changes in fuel composition can cause dangerous increase in combustion dynamics and can also affect the NOx emissions of the machine. Therefore, in order to meet the growing market demand for gas turbine combustors able to tolerate significant alterations in fuel composition, a system capable of burning gases with differing and variable over time Wobbe Indexes was developed. This innovative system does not involve any combustion hardware modifications. It allows the use of a premixed combustion system that complies with emissions, reliability, and safety, even when burning a fuel that is distinctly different from the original design gas. In particular, the system was developed in order to meet the requirements of a customer for burning any continuously and slowly varying mixture of two fuel gases, whose Wobbe Indexes difference is up to 25%. Since the burner is designed for 100% of the gas with lower Wobbe Index, the gas that has a higher WI needs to be heated, in order to achieve a target Modified Wobbe Index; the same happens for any mixture of the two gases. The system is based on a closed loop control on the Modified Wobbe Index of the fuel. Two turbine control gas chromatographs, located upstream the combustor inlet, measure the gas characteristics (LHV, specific gravity and temperature) and calculates the MWI. If it is different from the target one, it is corrected by modifying the temperature set point of a heat exchanger. The hardware is completed with one more plant gas chromatograph, located upstream the heat exchanger, for evaluating the fast and complete switch from one gas to the other one. In addition to the normal operation, that is with the 100% Lower Wobbe Index gas (L) or 100% Higher Wobbe Index gas (H) or any continuously and slowly varying mixture of these two gases, the system allows both the black and the normal start, the complete switch back and forth between 100% L gas and 100% H gas and load sheds and rejection. Moreover the two gases can be burned in diffusion combustion mode, as available, without requiring any increase in temperature, with no limitation from firing to full load. The capability of the system to adjust to all of the previously described events, potentially dangerous and damaging for the Gas Turbine combustion system, makes it suitable for applications that burn different lots of gases coming from different LNG sources, since it allows the turbine to accommodate the differences in Wobbe Index, due to various gas lots on a pipe line.

Major limitations for power turbine blades for oil & gas and industrial applications are Creep and HCF (High Cycle Fatigue). Power Turbine blades, being normally uncooled, are generally not affected by high temperature gradients; therefore LCF (Low Cycle Fatigue) doesn’t constitute their main limiting life factor. If creep is often not a limiting factor for aircraft engines blades, where inspection, maintenance and replacement intervals are more frequent, it becomes one of the key drivers for an industrial gas turbine where required flow path components life is at least one order larger. To avoid HCF failures, it would be desirable to avoid stimuli crossing natural frequencies in the entire operative range. However, due to the wide operative range and high number of stimuli present, the avoidance of potential resonance crossings is often not possible. This is the one of the reasons why a prototype validation campaign is usually performed, where, during the test, vibratory stress levels are compared to HCF endurance limits. This paper describes the processes used in GE Infrastructure Oil&Gas to verify, design, develop and test a PT (Power Turbine) blade for an upgraded 35 MW-class aero-derivative gas turbine. Initial assessment phases, new material selection, concurrent engineering efforts, bench testing characterization and final validation on FETT (First Engine to Test) are described. A particular focus is given to the analytical tools (i.e. modal cyclic symmetry analysis) used during the design phase and validation tests.

The PGT25+G4 gas turbine, latest in GE Infrastructure Oil&Gas PGT25 two-shaft aeroderivative family, is a 34 MW-class gas turbine for mechanical drive and power generation applications and maintains the same efficiency and availability of the previous PGT25+. The PGT25+G4 was validated through an extensive test program, which included some key test-rigs such as the full-scale LM2500+G4 Gas Generator test and other component tests, in advance of the First Engine to Test (FETT). The FETT included an equivalent-to-production configuration package (gas turbine, auxiliaries and control system), ran in a dedicated area in GE Oil&Gas Test Facilities to validate the machine for both mechanical drive and power generation applications. All critical-to-quality parameters of the HSPT (High Speed Power Turbine) were investigated, such as turbine gas path components temperatures and stresses, PT performances and PT operability when coupled with the LM2500+G4 Gas Generator. First production unit is currently in operation at Alliance Pipeline Canada Windfall 1 Compression Station. This paper describes the gas turbine main features, how the test program was built and discusses FETT results. Moreover, gas turbine field operation experience and lessons learned are presented.

In gas turbines, High Cycle Fatigue (HCF) bucket failures are mainly prevented by avoiding resonance frequencies in the operative range. Due to the high number of stimuli present, avoiding potential resonance crossings is often not possible. In these cases, failures can be avoided by controlling vibratory stress levels in order not to exceed high cycle fatigue endurance limits. This paper describes the processes used in GE Infrastructure, Oil&Gas to design, develop and test a new high-pressure turbine bucket for a 32 MW-class industrial gas turbine for mechanical drive and power generation applications. Initial design phases, material selection, concurrent engineering efforts, bench testing characterization and final validation on FETT (First Engine to Test) are described. A particular focus is given to the analytical tools (i.e. Modal Cyclic Analysis) used in the design phase and the validation tests (i.e. Ping Test and Laser Doppler Vibration) including the development of a dedicated instrumentation technique, which allowed the unit not to be disassembled (High Temperature Strain Gauge Splicing).

GE Energy’s new gas turbine, the MS5002E, is a 30 MW-class industrial gas turbine for mechanical drive and power generation applications. The MS5002E (fig.1) is the latest in the Frame5 two-shaft family and, while it retains some features from previous versions, the machine has been specifically designed for low environmental impact and high reliability, in direct response to customer demand for high efficiency and availability [1] & [2]. Main features for the MS5002E are: • 32 MW base load power at ISO inlet conditions (no losses); • 36% thermal efficiency; • 11-stage axial compressor and 17:1 pressure ratio; • reverse flow, six cans, Dry Low NOx (DLN2 technology) combustion system; • two-stages reaction type HP turbine; • two-stages PT leveraged from the LM2500+ HSPT (High Speed Power Turbine); • HP speed operating range 90% (6709rpm) / 101% (7529rpm); • PT speed operating range 50% (2857rpm) / 105% (6000rpm); • exhaust gas temperature (EGT): ∼510°C; • two-baseplates configuration (gas turbine flange-to-flange unit and auxiliary system); • integrated enclosure and baseplate, providing maximum accessibility for maintenance. The design of the MS5002E has been validated through an extensive test program which has included some key-test rigs such as the Rotordynamic Test, the CTV Test (full-scale axial compressor test) and numerous component and full-scale combustion tests in laboratory, conducted in advance of the First Engine to Test (FETT). The MS5002E First Engine to Test was initially started in January 2003 and the validation program has been completed with a full gas turbine teardown, dirty layout (visual and dimensional inspections for each major gas turbine component in as-is conditions) and NDT inspection in June 2004. During engine teardown, disassembly/assembly procedures and tools have been tested and validated. Additional endurance and operability testing is ongoing and will be completed by the end of 2005. The First Engine to Test is a complete equivalent-to-production package including gas turbine, auxiliaries and control system. For the test, a dedicated plateau has been built in Massa, Italy [3]. The gas turbine has been equipped with over 1400 direct measurement points (for a total of more than 2400 direct and indirect measurements) covering the flange-to flange, the package and auxiliaries. All critical-to-quality parameters, such as turbine gas path components temperatures and stresses, combustor temperatures and dynamics, performances and emissions, have been carefully verified by means of redundant instrumentation. This paper presents how the test program has been built on the GE Energy NPI (New Product Introduction) Development Process and how results from tests are fed back to the gas turbine design process. The paper discusses test rig and facilities layout, gas turbine operation experience and lessons learned. Results from the tests and measurements are also discussed.

Dry, Low NOx (DLN) gas turbine combustion systems that use the lean, premixed combustion technique for emissions control are susceptible to dynamic pressure oscillations. During the initial full-load prototype testing of the MS5002E, excessive dynamic pressures were encountered when attempting fully premixed combustor operation, preventing the gas turbine from meeting a 15 ppm NOx emissions target. A series of experiments were performed to examine potential acoustic differences between the original laboratory fuel injection system and the prototype hardware used in the field test. The experimental results were used to validate an analytical model that was used to optimize the fuel circuit geometry for dynamics reduction. The resulting revised design demonstrated a ten-fold reduction in dynamic pressure amplitudes. As a result, the system was able to operate over the premixed mode operating range and provides the desired NOx levels with acceptable dynamic pressures and operability.

Increased computational capabilities make available for the aero/thermal designers new powerful tools to include more geometrical details, improving the accuracy of the simulations, and reducing design costs and time. In the present work, a low-pressure turbine was analyzed, modeling the rotor-stator including the wheel space region. Attention was focused on the interaction between the coolant and the main flow in order to obtain a more detailed understanding of the behavior of the angel wings, to evaluate the wall heat flux distribution, and to prevent hot gas ingestion. Issues of component reliability related to thermal stress require accurate modeling of the turbulence and unsteadiness of the flow field. To satisfy this accuracy requirement, a full 3D URANS simulation was carried out. A reduced count ratio technique was applied in order to decrease numerical simulation costs. The study was carried out to investigate a new two-stage Low Pressure Turbine from GE Infrastructure Oil&Gas to be coupled to a new aeroderivative gas generator, the LM2500+G4, developed by GE Infrastructure, Aviation.