Heavy Duty Gas Turbine Research Articles

The thermie energy farm project

Within the framework of the THERMIE Programme 1994 of the European Union (EU), a group of European organisations constituted by USF/Smogless S.p.A. (a subsidiary of US Filter), EDP-Electricidade de Portugal S.A., Energia Verde S.p.A., and Lurgi Energie und Umwelt GmbH is implementing the THERMIE Energy Farm (TEF) project aimed at the demonstration of the technical and economic feasibility of power-generation from biomass, using the Integrated Gasification Combined-Cycle concept. At a site close to Pisa (Italy), a plant with a net power output of approximately 12 MW e will be erected; it will feature an atmospheric, air-blown, circulating fluidized-bed (CFB) gasifier, integrated with a 10.9 MW e, single-shaft, heavy-duty gas turbine, suited to burn the low-calorific value fuel gas produced by the gasifier, and a heat recovery steam generator which provides steam to a 5 MW e condensing steam-turbine. The design fuel consists of a mixture of wood chips from short rotation forestry and forest and agricultural residues, including olive stones and grape-seed flour. The financial viability of the project relies on the incentive provided by the Italian government with a premium price per kWh of electricity produced from renewables and on the financial contribution from the EU. The implementation phase was started in May 1997, when three main supply-contracts were signed. The commissioning phase is envisaged to commence during autumn 2000.

5632143 Gas turbine system and method using temperature control of the exhaust gas entering the heat recovery cycle by mixing with ambient air

Combustion dynamics constitutes one of the most challenging areas in combustion research. Many facets of this subject have been investigated over the past few decades for their fundamental and practical implications. Substantial progress has been accomplished in understanding analysis, modeling, and simulation. Detailed laboratory experiments and numerical computations have provided a wealth of information on elementary dynamical processes such as the response of flames to variable strain, vortex rollup, coupling between flames and acoustic modulations, and perturbed flame collisions with boundaries. Much recent work has concerned the mechanisms driving instabilities in premixed combustion and the coupling between pressure waves and combustion with application to the problem of instability in modern low NOx heavyduty gas turbine combustors. Progress in numerical modeling has allowed simulations of dynamical flames interacting with pressure waves. On this basis, it has been possible to devise predictive methods for instabilities. Important efforts have also been directed at the development of the related subject of combustion control. Research has focused on methods, sensors, actuators, control algorithms, and systems integration. In recent years, scaling from laboratory experiments to practical devices has been achieved with some successebut limitations have also been revealed. Active control of combustion has also evolved in various directions. A number of experiments on laboratory-scale combustors have shown that the amplitude of combustion instabilities could be reduced by applying control principles. Full-scale terrestrial application to gas turbine systems have allowed an increase of the stability margin of these machines. Feedback principles are also being explored to control the point of operation of combustors and engines. Operating point control has special importance in the gas turbine field since it can be used to avoid operation in unstable regions near the lean blowoff limits. More generally, closed loop feedback concepts are useful if one wishes to improve the combustion process as demonstrated by applications to automotive engines. Many future developments of combustion will use such concepts for tuning, optimization, and emissions reduction. This article proposes a broad survey of these fast-moving areas of research.

Development of a Catalytic Combustor for a Heavy-Duty Utility Gas Turbine

The most effective technologies currently available for controlling NOx emissions from heavy-duty industrial gas turbines are diluent injection in the combustor reaction zone, and lean premixed Dry Low NOx (DLN) combustion. For ultralow emissions requirements, these must be combined with selective catalytic reduction (SCR) DeNOx systems in the gas turbine exhaust. An alternative technology for achieving comparable emissions levels with the potential for lower capital investment and operating cost is catalytic combustion of lean premixed fuel and air within the gas turbine. The design of a catalytic combustion system using natural gas fuel has been prepared for the GE model MS9OO1E gas turbine. This machine has a turbine inlet temperature to the first rotating stage of over 1100°C and produces approximately 105 MW electrical output in simple cycle operation. The 508-mm-dia catalytic combustor designed for this gas turbine was operated at full-scale conditions in tests conducted in 1992 and 1994. The combustor was operated for twelve hours during the 1994 test and demonstrated very low NOx emissions from the catalytic reactor. The total exhaust NOx level was approximately 12–15 ppmv and was produced almost entirely in the preburner ahead of the reactor. A small quantity of steam injected into the preburner reduced the NOx emissions to 5–6 ppmv. Development of the combustion system has continued with the objectives of reducing CO and UHC emissions, understanding the parameters affecting reactor stability and spatial nonuniformities that were observed at low inlet temperature, and improving the structural integrity of the reactor system to a level required for commercial operation of gas turbines. Design modifications were completed and combustion hardware was fabricated for additional full-scale tests of the catalytic combustion system in March 1995 and January 1996. This paper presents a discussion of the combustor design, the catalytic reactor design, and the results of full-scale testing of the improved combustor at MS9OO1E cycle conditions in the March 1995 and January 1996 tests. Major improvements in performance were achieved with CO and UHC emissions of 10 ppmv and 0 ppmv at baseload conditions. This ongoing program will lead to two additional full-scale combustion system tests in 1996. The results of these tests will be available for discussion at the June 1996 Conference in Birmingham.

The effect of gas turbine coolant modulation on the part load performance of combined cycle plants. Part 2: Combined cycle plant

For combined cycle plants that consist of heavy-duty gas turbine and single-pressure heat recovery steam generator, the effect of gas turbine coolant modulation on plant performance is analysed. Two distinct schemes for gas turbine load control are adopted (the fuel-only control and the variable compressor geometry control), based on the gas turbine calculation in Part 1 of this series of papers. Models for heat recovery steam generator and steam turbine are combined with the gas turbine models of Part 1 to result in a complete analysis routine for combined cycles. The purpose of gas turbine coolant modulation is to minimize coolant consumption by maintaining the turbine blade temperatures as high as possible. It is found that the coolant modulation leads to reduction in heat recovery capacity, which decreases steam cycle power. However, since the benefit of coolant modulation for the gas turbine cycle is large enough, the combine cycle efficiency is improved.

The effect of gas turbine coolant modulation on the part load performance of combined cycle plants. Part 1: Gas turbines

This paper demonstrates a favourable influence of turbine coolant modulation on the part load performance of gas turbines. A general simulation programme is developed, which is capable of accurately estimating the design and part load performance of modern heavy-duty gas turbines characterized by intensive turbine blade cooling Investigations are made for a typical gas turbine and two distinct load control schemes are considered: the fuel-only control and the variable compressor geometry control. Maintaining blade temperatures as high as possible whose purpose is to minimize coolant consumption is simulated. It is found that the coolant modulation makes the part load characteristics deviate from usual behaviours and creates a considerable enhancement of part load thermal efficiency. For the fuel-only control with coolant modulation, it is predicted that efficiency can be higher than design efficiency over a wide range of part load operation.

Design and Test of a New Axial Compressor for the Nuovo Pignone Heavy-Duty Gas Turbines

This axial compressor design was primarily focused to increase the power rating of the current Nuovo Pignone PGT10 Heavy-Duty gas turbine by 10 percent. In addition, the new 11-stage design favorably compares with the existing 17-stage compressor in terms of simplicity and cost. By scaling the flowpath and blade geometry, the new aerodynamic design can be applied to gas turbines with different power ratings as well. The reduction in the stage number was achieved primarily through the meridional flowpath redesign. The resulting higher blade peripheral speeds achieve larger stage pressure ratios without increasing the aerodynamic loadings. Wide chord blades keep the overall length unchanged thus assuring easy integration with other existing components. The compressor performance map was extensively checked over the speed range required for two-shaft gas turbines. The prototype unit was installed on a special PGT10 gas turbine setup, that permitted the control of pressure ratio independently from the turbine matching requirements. The flowpath instrumentation included strain gages, dynamic pressure transducers, and stator vane leading edge aerodynamic probes to determine individual stage characteristics. The general blading vibratory behavior was proved fully satisfactory. With minor adjustments to the variable stator settings, the front stage aerodynamic matching was optimized and the design performance was achieved.

Split Stream Boilers for High-Temperature/High-Pressure Topping Steam Turbine Combined Cycles

Research and development work on high-temperature and high-pressure (up to 1500°F TIT and 4500 psia) topping steam turbines and associated steam generators for steam power plants as well as combined cycle plants is being carried forward by DOE, EPRI, and independent companies. Aeroderivative gas turbines and heavy-duty gas turbines both will require exhaust gas supplementary firing to achieve high throttle temperatures. This paper presents an analysis and examples of a split stream boiler arrangement for high-temperature and high-pressure topping steam turbine combined cycles. A portion of the gas turbine exhaust flow is run in parallel with a conventional heat recovery steam generator (HRSG). This side stream is supplementary fired opposed to the current practice of full exhaust flow firing. Chemical fuel gas recuperation can be incorporated in the side stream as an option. A significant combined cycle efficiency gain of 2 to 4 percentage points can be realized using this split stream approach. Calculations and graphs show how the DOE goal of 60 percent combined cycle efficiency burning natural gas fuel can be exceeded. The boiler concept is equally applicable to the integrated coal gas fuel combined cycle (IGCC).

Dual-Use Conversion of a High-Mach-Number Jet Engine Test Cell for Industrial Gas Turbine Low-Emission Combustor Development

With the recent trend of reducing U.S. military expenditures, it has become desirable to develop dual use of certain Department of Defense facilities. These efforts have a commercial purpose, while still retaining a military benefit. The goals of these efforts are to make U.S. business more competitive in world markets, to develop the technology to solve pressing national problems, and to maintain intact the necessary talent pool and equipment for possible military needs. In a recent initiative described in this paper, test cell equipment at the Arnold Engineering Development Center, Arnold AFB, Tennessee, was modified and expanded to allow development by the Westinghouse Electric Corporation of low-emission combustors for heavy-duty gas turbines for commercial power generation.

The Cascaded Humidified Advanced Turbine (CHAT)

This paper introduces the Cascaded Humidified Advanced Turbine (CHAT) plant, a gas turbine based power generation plant utilizing intercooling, reheat, and humidification. It is based upon the integration of an existing heavy duty gas turbine with an additional shaft comprising industrial compressors and high pressure expander. CHAT capitalizes on the latest proven gas turbine technology, which, combined with a sophisticated thermal cycle configuration, results in substantial improvement in gas turbine efficiency, compared to a simple cycle, while still maintaining typical advantages and merits of a combustion turbine plant. Built with a commercial combustion turbine and available industrial compressors and expanders, the CHAT plant does not require extensive product development and testing. As a result, the CHAT power plant can be offered with specific capital costs up to 20 percent lower than the combined cycle plant, and with competing efficiency. Compared to a combined cycle plant, the CHAT plant offers lower emissions (due to air humidification) and other significant operating advantages with regard to start-up time and costs, better efficiency at part load, lower power degradation at higher ambient temperatures, and simpler operations and maintenance due to elimination of the complexities and costs associated with steam production. The CHAT plant also integrates very effectively with coal gasification and particularly well with the water quench design. This feature has been discussed in previous publications.

Development of 12 % CrNb Steel for Heavy Duty Gas Turbine Discs.

Effect of adding elements on creep rupture strength and toughness for heat resistant 12%Cr steel of 1300°C class gas turbine disc was investigated. Creep rupture strength was increased by addition of Mo, W, V, Nb, and N. It was found that the addition of Nb causes a significant increase of creep rupture strength due to fine dispersion of NbC and of ductility due to grain refining. Chemical composition of 12Cr-2.5Ni-2Mo-0.2V-0.08Nb-N steel is determined for gas turbine disc application. Preparation of real scale disc was carried out by electro-slag remelting process in order to avoid the segregation of adding elements in ingot. It is resulted that the mechanical properties of real scale disc specimen show the equivalent properties of small specimens. The steel discs for gas turbine were manufactured from the new steel.

排気再燃型ガスタービン・リパワリングシステム導入 高効率コージェネレーションシステム

As an example at recent Co-generation system for industry use, we introduce its characteristic and operational result of Repowering system with exhaust gas reburning which was first applied in Japan. The repowering system is composed of power boiler and steam turbine which were in use, and of 4 MW class heavy-duty gas turbine set newly. The power boiler was reformed to convert heavy oil into city gas, and for conduction gas turbine exhaust gas. This system produces reduction of energy use about 15%, and of NOx, CO2 emission about 30%.

Performance and Economic Enhancement of Cogeneration Gas Turbines Through Compressor Inlet Air Cooling

Gas turbine air cooling systems serve to raise performance to peak power levels during the hot months when high atmospheric temperatures cause reductions in net power output. This work describes the technical and economic advantages of providing a compressor inlet air cooling system to increase the gas turbine’s power rating and reduce its heat rate. The pros and cons of state-of-the-art cooling technologies, i.e., absorption and compression refrigeration, with and without thermal energy storage, were examined in order to select the most suitable cooling solution. Heavy-duty gas turbine cogeneration systems with and without absorption units were modeled, as well as various industrial sectors, i.e., paper and pulp, pharmaceuticals, food processing, textiles, tanning, and building materials. The ambient temperature variations were modeled so the effects of climate could be accounted for in the simulation. The results validated the advantages of gas turbine cogeneration with absorption air cooling as compared to other systems without air cooling.

Effect of Material Degradation on Impact Damage of Cast Ni-Base Superalloy IN738LC.

Nickel-base superalloy IN738LC is widely used for heavy-duty gas turbine buckets. But the buckets in current advanced gas turbines are exposed to extremely high temperature, which induces significant material degradation during service. Therefore an evaluation of the resistance against damage caused by foreign objects is required to establish a material degradation assessment system. In order to investigate the damage caused by impact from a projectile, the long-time aged material at 750°C-900°C up to 24000h of IN738LC are artificially produced and the single-particle fracture test was made on a particle impact test rig. In this study, introducing the fracture model, in which the strain rate controlling process is that dislocations move past γ' precipitates by looping, the critical velocity of impact fracture is explained as a function of projectile size, target thickness, mechanical property such as material elongation and the microstructural parameter of a ratio of the second power of the γ' interparticle distance to the γ' mean diameter. Furthermore, using measured impact loads, the relationship between normalized deformation work induced by impact projectile and impact velocity is discussed.

Heavy duty gas turbines experience with ash-forming fuels

The heavy duty gas turbines operating in power plants can burn various fuels ranging from natural gas to heavy oils. Ash-forming fuels can have detrimental effects on the turbine hardware such as : combustion troubles, erosion, corrosion and fouling by ashes. For decades, progress has been made by the gas turbine industry, especially in the fields of superalloy metallurgy, coating and cooling technology. Furthermore, fuel treatments inspired by the petroleum and marine-engine industries (electrostatic and centrifuge desalting systems) and a vanadic corrosion inhibition philosophy based on magnesium additives have been developed to fully control corrosion.

Comparison of coating performance and degradation modes in heavy-duty land-based gas turbines

Significant operating experience has now been obtained on several different coating systems which have seen service in General Electric Co. heavy-duty gas turbines. Service times in excess of 10 000 h have been accumulated on several different MCrA1Y coatings, with and without overaluminide outer layers, and on PtA1 coatings. Since, in many instances, all these coatings were present in the same rotor, direct comparisons of performance and degradation are possible. This paper describes the coating requirements for long-life bucket protection, how each of these coating systems has performed, and the advantages and disadvantages of each.

化学蒸着法によって形成したガスタービン翼用高温耐食性ＮｉＡｌコーティング

NiAl was deposited by reduced pressure CVD to form hot corrosion resistant coatings for the cooling pessages of heavy duty gas turbine buckets.AlCl3 and AlCl were used as chemical reaction gases with H2 gas as carrier gas. An NiAl coating layer was formed by deposition and subsequent diffusion of Al into Ni base superalloy. Optimum coating conditions were surveyed to obtain a uniform coating thickness for the complex shaped cooling passage utilizing a simulation model.It was found that in the model bucket cooling passage the ratio of NiAl layer thickness at the outlet to that at the inlet was about 45% under coating conditions of 950-1000°C and 20-40Torr and using a reverse flow prevention device.

複合損傷シミュレーション解析によるＣｏ基超合金の高温低サイクル疲労寿命評価

A life assessment method is proposed for severely damaged components such as heavy-duty gas turbine nozzles. The method named “Multi-factor damage simulation analysis” is introduced as a sort of inverse problem analysis for actual complex damage phenomena influenced by temperature-stress distribution, microstructural inhomogeneity, environment, interaction of multiple cracks, and so on. The microstructural inhomogeneity model of Co-base nozzle superalloy FSX414 is constructed by using fractal geometry of random percolation cluster model. Multiple crack intiation and growth simulation is performed with a probabilistic damage parameter which is defined as the transition probability of crack initiation and growth in the form of monotonically increasing function of cycle.This method was applied for high temperature low cycle fatigure testing of FSX414 at 923K, 1023K, 1123K and 1223K by assigning relatively simple values for resistance R and driving force F. Arrhenius type temperature dependence was postulated for resistance R by taking account of the experimental results.The crack morphology obtained by the simulation and the crack length distribution were quite similar to the observation results of the failed low cycle fatigue specimen surface. Moreover, the temperature dependence of the rate of life expenditure (1/N25) coincided with the experimental results. Therefore, it is concluded that this method is a promising way to estimate the life of severely damaged component under complex situations.

Strength evaluation method and design optimization for ceramic gas turbine blades

The unified strength estimation method is proposed as a strength evaluation method which results in reliability design for ceramics application in heavy-duty gas turbines. This method is based on the weakest0link theory and complete time-dependent crack growth properties. A unified strength estimation method is also useful for the reliability analysis of rotating ceramic blades, taking account of the positive compression and the negative tensile ceramic mechanical characteristics.

Large Heavy-Duty Gas Turbines for Base-Load Power Generation and Heat Cogeneration

Article Large Heavy-Duty Gas Turbines for Base-Load Power Generation and Heat Cogeneration was published on March 1, 1989 in the journal International Journal of Turbo & Jet-Engines (volume 6, issue 1).

Flow in Liner Holes for Countercurrent Combustion Systems

Heavy-duty gas turbine combustion systems have a “reverse flow” combustion-cooling air network. High-temperature gradients have been observed in some combustion liners around the plain holes, or around the cylindrical inserts welded into the mixing holes. Flow visualization tests were performed in a countercurrent flow facility. Measurements of pressure and velocity distributions in and around the mixing hole jet were taken, and mass flow rates and discharge coefficients were calculated in order to characterize and compare the two geometries. The results with a plain hole (square-edged orifice) and the cylindrical insert show the presence of a sharp separation region at the trailing edge (combustion side) of the liner hole, which may cause the high-temperature gradients observed under operating conditions. The measured discharge coefficients show a dependence on the insert geometry, the flow parameter (K), and the bottom section (combustion side) countercurrent flow velocity.