Aeroderivative Gas Turbine Research Articles

Methodologies for predicting the part-load performance of aero-derivative gas turbines

Abstract Prediction of the part-load performance of gas turbines is advantageous in various applications. Sometimes reasonable part-load performance is sufficient, while in other cases complete agreement with the performance of an existing machine is desirable. This paper is aimed at providing some guidance on methodologies for predicting part-load performance of aero-derivative gas turbines. Two different design models – one simple and one more complex – are created. Subsequently, for each of these models, the part-load performance is predicted using component maps and turbine constants, respectively. Comparisons with manufacturer data are made. With respect to the design models, the simple model, featuring a compressor, combustor and turbines, results in equally good performance prediction in terms of thermal efficiency and exhaust temperature as does a more complex model. As for part-load predictions, the results suggest that the mass flow and pressure ratio characteristics can be well predicted with both methods. The thermal efficiency and exhaust temperature, however, are not well predicted below 60–70% load when using turbine constants and assuming constant efficiencies for turbomachinery.

A Systematic Comparison and Multi-Objective Optimization of Humid Power Cycles—Part I: Thermodynamics

The steam injected gas turbine (STIG), humid air turbine (HAT), and TOP Humid Air Turbine (TOPHAT) cycles lie at the center of the debate on which humid power cycle will deliver optimal performance when applied to an aeroderivative gas turbine and, indeed, when such cycles will be implemented. Of these humid cycles, it has been claimed that the TOPHAT cycle has the highest efficiency and specific work, followed closely by the HAT, and then the STIG cycle. In this study, the systems have been simulated using consistent thermodynamic and economic models for the components and working fluid properties, allowing a consistent and nonbiased appraisal of these systems. Part I of these two papers focuses purely on the thermodynamic performance and the impact of the system parameters on the performance; Part II will study the economic performance. The three humid power systems and up to ten system parameters are optimized using a multi-objective Tabu Search algorithm, developed in the Cambridge Engineering Design Centre.

A Systematic Comparison and Multi-Objective Optimization of Humid Power Cycles—Part II: Economics

The steam injected gas turbine (STIG), humid air turbine (HAT), and TOP Humid Air Turbine (TOPHAT) cycles lie at the center of the debate on which humid power cycle will deliver optimal performance when applied to an aeroderivative gas turbine and, indeed, when such cycles will be implemented. Of these humid cycles, it has been claimed that the TOPHAT cycle has the highest efficiency and specific work, followed closely by the HAT and then the STIG cycle. In this study, the systems have been simulated using consistent thermodynamic and economic models for the components and working fluid properties, allowing a consistent and nonbiased appraisal of these systems. Part I of these two papers focused on the thermodynamic performance and the impact of the system parameters on the performance, Part II studies the economic performance of these cycles. The three humid power systems and up to ten system parameters are optimized using a multi-objective Tabu Search algorithm, developed in the Cambridge Engineering Design Centre.

공기부양선의 추진 및 부양축계 비틀림진동 해석 연구

A propulsion and lift shafting system in an air cushion vehicle is flexible multi-elements system which consists of two aeroderivative gas turbines with own bevel gears, four stage lift fan reduction gear, two stage propulsion reduction gear, air propellers and high capacity of lifting fans. In addition, the system includes the multi-branched shafting with multi-gas turbine engines and thin walled shaft with flexible coupling. Such a branched shafting system has very intricate vibrating characteristics and especially, the thin walled shaft with flexible couplings can lower the torsional natural frequencies of shafting system to the extent that causes a resonance in the range of operating revolution.<BR> In this study, to evaluate vibrational characteristics some analytical methods for the propulsion and lift shafting system are studied. The analysis, including natural frequencies and mode shapes, for five operation cases of the system is conducted using ANSYS code with a equivalent mass-elastic model.

Parametric Analysis of Combined Cycles Equipped With Inlet Fogging

In recent years, deregulation in the power generation market worldwide combined with significant variation in fuel prices and a need for flexibility in terms of power augmentation specially during periods of high electricity demand (summer months or noon to 6:00 p.m.) has forced electric utilities, cogenerators and independent power producers to explore new power generation enhancement technologies. In the last five to ten years, inlet fogging approach has shown more promising results to recover lost power output due to increased ambient temperature compared to the other available power enhancement techniques. This paper presents the first systematic study on the effects of both inlet evaporative and overspray fogging on a wide range of combined cycle power plants utilizing gas turbines available from the major gas turbine manufacturers worldwide. A brief discussion on the thermodynamic considerations of inlet and overspray fogging including the effect of droplet dimension is also presented. Based on the analyzed systems, the results show that high pressure inlet fogging influences performance of a combined cycle power plant using an aero-derivative gas turbine differently than with an advanced technology or a traditional gas turbine. Possible reasons for the observed differences are discussed.

05/01798 Regulatory and voluntary approaches for enhancing building energy efficiency: Lee, W. L. and Yik, F. W. H. Progress in Energy and CombustionScience, 2004, 30, (5), 477–499

The capabilities of the chemical recuperation of exhaust and compressor intercooling heat from gas turbines have been investigated in this paper considering methanol as primary fuel for the Reheat InterCooled (intercooler heat is recovered) Aeroderivative Gas Turbine. The model includes an exergy analysis method and a simplified blade cooling model. The location of the intercooler, the reheat combustion chamber as well as the overall pressure ratio have been optimized. Comparisons are made with the Chemically Recuperated Gas Turbine CRGT cycles using methane as a primary fuel.

Parametric Analysis of Existing Gas Turbines With Inlet Evaporative and Overspray Fogging

With deregulation in the power generation market and a need for flexibility in terms of power augmentation during the periods of high electricity demand, power plant operators all over the world are exploring means to augment power from both the existing and new gas turbines. An approach becoming increasingly popular is that of the high pressure inlet fogging. In this paper, the results of a comprehensive parametric analysis on the effects of inlet fogging on a wide range of existing gas turbines are presented. Both evaporative and overspray fogging conditions have been analyzed. The results show that the performance parameters indicative of inlet fogging effects have a definitive correlation with the key gas turbine design parameters. In addition, this study indicates that the aeroderivative gas turbines, in comparison to the heavy-duty industrial machines, have higher performance improvement due to inlet fogging effects. Plausible reasons for the observed trends are discussed. This paper represents the first systematic study on the effects of inlet fogging for a large number (a total of 67) of gas turbines available from the major gas turbine manufacturers.

Pioneering Gas Turbine-Electric System in Cruise Ships: A Performance Update

Recent marine projects have extended the range of applications for GE's LM aeroderivative gas turbines in commercial marine markets. The world's first all gas turbine-powered cruise ship, GTS Millennium, entered service in June 2000. The in-service performance of the combined gas turbine electric and steam system (COGES) will be discussed further in this paper.

Tuning Your Fuel-Gas Delivery System

Saudi Aramco has focused more attention in recent years on fuel-gas conditioning for land-based industrial and aeroderivative combustion gas turbines (CGTs). Hydrocarbon dew points and entrained solids are two important fuel quality issues that frequently trouble CGT operators, partly because they cannot be guaranteed by the fuel suppliers and they are rarely monitored by the operators. This paper addresses these issues and offers some practical advice to optimize the design and operation of fuel gas delivery systems. Saudi Aramco has been testing an automated on-line dew point monitor capable of detecting both hydrocarbon and aqueous dew points in natural gas. Dew point monitoring, conducted at three locations on the fuel gas grid, revealed wide variations in the hydrocarbon and aqueous dew points due to a variety of conditions. Gas production and pipeline operations accounted for the most dramatic variations in dew points, but exposure of pipelines to the weather can also be important. Measurement of pipeline solids for the purpose of sizing and placement of particle filters have also been explored. Pipeline scraping, gas velocities, length of pipeline span, pipeline junctions, and control valves are all considerations for solid control strategies. The optimized design and operation of a CGT fuel system is highly dependent on dew point control and efficient removal of entrained pipeline solids. Practical experience in monitoring hydrocarbon and aqueous dew points, pipeline solids control, and optimizing fuel conditioning equipment are considered.

Aspects of Cooled Gas Turbine Modeling for the Semi-Closed O2/CO2 Cycle With CO2 Capture

In order to capture the behavior of the oxyfuel cycle operating with high combustor-outlet temperature, the impact of blade and vane cooling on cycle performance must be included in the thermodynamic model. As a basis for a future transient model, three thermodynamic models for the cooled gas turbine are described and compared. The first model, known previously from the literature, models expansion as a continuous process with simultaneous heat and work extraction. The second model is a simple stage-by-stage model and the third is a more detailed stage-by-stage model that includes velocity triangles and enables the use of advanced loss correlations. An airbreathing aeroderivative gas turbine is modeled, and the same gas turbine operating in an oxyfuel cycle is studied. The two simple models show very similar performance trends in terms of variation of pressure ratio and turbine inlet temperature in both cases. With the more detailed model, it was found that, without any change of geometry, the turbine rotational speed increases significantly and performance drops for the maintained geometry and pressure ratio. A tentative increase of blade angles or compressor pressure ratio is found to increase turbine performance and decrease rotational speed. This indicates that a turbine will require redesign for operation in the oxyfuel cycle.

The Effect of Water Injection on Multispool Gas Turbine Behavior

Abstract Background: The injection of water droplets into industrial gas turbines is now commonplace and is central to several proposed advanced cycles. These cycles benefit from the subsequent reduction in compressor work, the increase in turbine work, and (in the case of recuperated cycles) reduction in compressor delivery temperature, which all act to increase the efficiency and power output. An investigation is presented here into the effect such water droplets will have on the operating point and flow characteristics of an aeroderivative gas turbine cycle. Method of Approach: The paper first describes the development of a computer program to study the effects of water injection in multispool industrial gas turbines. The program can operate in two modes: the first uses pre-determined nondimensional wet compressor maps to match the components and is instructive and fast but limited in scope; the second uses the compressor geometries as input and calculates the wet compressor operating conditions as and when required. As a result, it is more computationally demanding, but can cope with a wider range of circumstances. In both cases the compressor characteristics are calculated from a mean-line analysis using suitable loss, deviation and blockage models, coupled with Lagrangian-style droplet evaporation calculations. The program has been applied to a three-spool machine to address issues such as the effects of water injection on power output and overall efficiency, and the off-design nature of the compressor operation. Results: Preliminary results calculated on this basis show similar trends to predictions for single-shaft machines, namely that air mass flow rates and pressure ratios are increased by water injection, and that early stages of the compressor are shifted towards choke and rear stages towards stall. The LP compressor in particular operates at severely off-design conditions. Conclusions: The predicted overall performance of the three-spool machine shows a substantial power boost and a marginal increase in thermal efficiency.

Gas path fault diagnosis framework for a three-shaft gas turbine

A diagnostic framework has been developed for the detection of faults in the gas path of a three-shaft aeroderivative gas turbine thermodynamically similar to the Rolls Royce RB211-24GT. The framework involves a large-scale integration of artificial neural networks (ANNs) designed and trained to detect, isolate and assess faults in the gas path components of the engine. The approach has the capacity to assess both multiple-component and multiple-sensor faults. The results obtained demonstrate the promise of ANNs applied to engine diagnostic activities.

Aerodynamic Design and Testing of an Axial Flow Compressor With Pressure Ratio of 23.3:1 for the LM2500+ Gas Turbine

The LM2500+ gas turbine, rated between 39,000–40,200 shaft horsepower (shp), was introduced for field service in 1998. This growth aero-derivative gas turbine is suitable for a variety of power generation applications, such as co-generation and combined cycle, as well as mechanical drive applications. At the heart of the LM2500+ 25% power increase is an up-rated derivative 17-stage axial compressor. This paper describes the aerodynamic design and development of this high-pressure ratio single-spool compressor for the LM2500+ gas turbine. The compressor is derived by zero-staging the highly efficient and reliable LM2500 compressor to increase the flow by 23% at a pressure ratio of 23.3:1. The aerodynamic efficiency of the compressor is further improved by using three-dimensional, custom-tailored airfoil designs similar to those used in the CF6-80C2 high-pressure compressor. The compressor achieved a peak polytropic efficiency above 91%, meeting all its operability objectives. The technical requirements and overall aerodynamic design features of the compressor are presented first. Next, the zero stage match point selection is described and the procedure used to set up the vector diagrams using a through-flow code with secondary flow and mixing is outlined. Detailed design results for the new transonic airfoils in the compressor using three-dimensional viscous analysis are presented. The compressor instrumentation and performance test results are discussed. The performance of the zero stage is separated from that of the baseline compressor with the CF6-80C2 airfoils to show the improvement in efficiency with the new airfoils.

Control of gas turbine power plants by means of the weighted one-step-ahead adaptive technique

The one-step-ahead controllers represent a branch of minimum prediction error adaptive controllers. They combine the parameter estimation of the controlled system model with the control scheme; therefore, they are especially suitable for non-linear and time-varying systems. Since the estimated parameters are updated at each time step (by using the sampled data), these methods can be adopted for non-linear applications. Consequently, the one-step-ahead controllers do not require knowledge of the dynamic characteristics of the controlled system (e.g. state-space systems or transfer functions). Sometimes, in the gas turbine field, the control system could produce an excessive control effort, due to sudden variations of the electric load. In order to reduce this control action, the weighted one-step-ahead adaptive (WOSAA) control algorithm considers a penalty associated with the control effort using an appropriate cost function. In this way, the control variable does not assume values that are too large, even when the gas turbine undergoes sudden changes in the external load. As a consequence, the robustness and stability features of the WOSAA control system are increased. The results show that the WOSAA control technique, applied to both the double-shaft aero-derivative gas turbine and the single-shaft heavy-duty gas turbine, effectively counteracts the load reduction with limited overshoot in the controlled variables with reduced control effort.

Residual Life Prediction of Turbine Blades of Aeroderivative Gas Turbines

Various methods have been proposed for predicting residual creep life of turbine blades. However, these conventional methods cannot be applied to predict residual lives with appropriate accuracy. This communication describes an alternative method, which is non-destructive and primarily based on blade extension measurements. Blade elongation measurements can be utilized in creep-life prediction as a non-destructive method and they are believed to give reasonable criteria for blade retirement. (orig.)

Thermodynamic analysis of chemically recuperated gas turbines

Significant research effort is currently centred on developing advanced aero-derivative gas turbine systems for electric power generation applications, in particular for intermediate duty operation. Compared to industrial gas turbines, aero-derivatives offer high simple cycle efficiency, a quick and frequent start capability without significant maintenance cost penalty. A key element for high system performance (efficiency and power output) is the development of improved heat recovery systems, leading to advanced cycles such as the STeam Injected Gas Turbine (STIG) cycle, Humid Air Turbine (HAT) cycle or the Chemically Recuperated Gas Turbine (CRGT) cycle. In this paper the chronology of development of this last technology and a detailed description of our research program “Thermodynamic analysis of chemically recuperated gas turbines” is presented. A comparative study of the performance potentials of CRGT cycles and the other advanced cycles for design and off-design mode is presented. The analysis method accounts for turbine blade cooling requirements, which have a decisive impact on cycle performance. Exergy calculations are included in the analysis method. Research perspectives for this technology are suggested.

Performance of Evaporative Cycle Gas Turbines Derived from Aeroengines

The modie cation of thethermodynamiccyclecould bean attractive opportunity for improving the performance of aeroderivative gas turbines. The simulation of a aeroderivative gas turbine modie ed to realize a nonintercooled regenerative water-injected (RWI) cycle is presented. The thermodynamic analysis of the RWI cycle shows that aeroderivative gas turbines with a pressure ratio from 16 to 20 can reach thermal efe ciency of 45%. The design of the enhanced gas turbine is carried out under the hypotheses that the compressor is unchanged and that the stator vanesofthetwo-stagehigh-pressureturbinearepartiallyopened to accommodateto thelargermasse owproduced by water injection. The other characteristics of the turbine stator blades (internal and external area and internal coolantpassages )andtherotorbladesaresupposed unchanged.Astage-by-stageoff-design model, including blade cooling and hydrodynamics, is introduced for predicting the performance of the modie ed high-pressure turbine. The effects produced by modie cation of the cycle are then evaluated. The off-design incidence angles at the rotor inlet of both the stages appear to limit the maximum amount of the water that can be injected per air mass unit. The increase of the blade temperature instead can be compensated by decreasing the turbine inlet temperature or by refrigerating the cooling air. The mathematical model adopted for simulating the on-design and the off-design behavior of the enhanced gas turbine is described.

Evaluation and Application of Data Sources for Assessing Operating Costs for Mechanical Drive Gas Turbines in Pipeline Service

This paper evaluates and demonstrates how the public domain data provided by individual interstate pipeline companies to FERC, when combined with individual company equipment lists, can be used to regress industry information on cost of operations and maintenance, fuel gas used, and cost of fuel and power. The paper describes the methods of analysis and identifies their limitations. The paper presents results of such regression analysis as average and variance of cost and fuel usage for industrial gas turbines and aeroderivative gas turbines. It provides further comparisons between gas turbine prime movers, reciprocating engine prime movers, and electric motor drives, and presents annual costs per installed horsepower as a function of turbine size. The paper is based on work performed for PRC International and the Gas Research Institute. [S0742-4795(00)01003-6]

Royal Navy Experience of Propulsion Gas Turbines and How and Why This Experience is Being Incorporated Into Future Designs

The Royal Navy (RN) has in-service experience of both marinized industrial and aero derivative propulsion gas turbines since the late 1940s. Operating through a Memorandum of Understanding (MOU) between the British, Dutch, French, and Belgian Navies the current in-service propulsion engines are marinized versions of the Rolls Royce Tyne, Olympus, and Spey aero engines. Future gas turbine engines, for the Royal Navy, are expected to be the WR21 (24.5 MW), a 5 to 8 MW engine and a 1 to 2 MW engine in support of the All Electric Ship Project. This paper will detail why the Royal Navy chose gas turbines as prime movers for warships and how Original Equipment Manufacturers (OEM) guidance has been evaluated and developed in order to extend engine life. It will examine how the fleet of engines has historically been provisioned for and how a modular engine concept has allowed less support provisioning. The paper will detail the planned utilization of advanced cycle gas turbines with their inherent higher thermal efficiency and environmental compliance and the case for all electric propulsion utilizing high speed gas turbine alternators. It will examine the need for greater reliability/availability allowing single generator operation at sea and how by using a family of 3 engines a nearly flat Specific Fuel Consumption (SFC) down to harbour loads can be achieved. [S0742-4795(00)01203-5]

Exergetic optimization of intercooled reheat chemically recuperated gas turbine

The capabilities of the chemical recuperation of exhaust and compressor intercooling heat from gas turbines have been investigated in this paper considering methanol as primary fuel for the Reheat InterCooled (intercooler heat is recovered) Aeroderivative Gas Turbine. The model includes an exergy analysis method and a simplified blade cooling model. The location of the intercooler, the reheat combustion chamber as well as the overall pressure ratio have been optimized. Comparisons are made with the Chemically Recuperated Gas Turbine CRGT cycles using methane as a primary fuel.