Simple Cycle Gas Turbine Research Articles

Compressor intake-air cooling in gas turbine plants

The generated power and efficiency of gas turbine plants depend on the temperature of the inlet air. At high ambient temperatures, a power loss of more than 20%, combined with a significant increase in specific fuel consumption, compared to ISO standard conditions (15 °C), can be observed. The purpose of this work is to present a computer simulation of the integration of an innovative technology for reducing the intake-air temperature in gas turbine plants. Following a description of the air-cooling system, simulation results for two test cases are presented: a simple cycle gas turbine and a combined cycle plant. First, the effect of ambient air temperature variation on the power output and efficiency is presented for both cases. Next, the results from the integration of an evaporative cooler and of the air-cooling system under consideration are presented and discussed, demonstrating the gain in power output and efficiency that can be achieved.

Introduction and Performance Prediction of a Nutating-Disk Engine

A new type of internal combustion engine and its thermodynamic cycle are introduced. The core of the engine is a nutating nonrotating disk, with the center of its hub mounted in the middle of a Z-shaped shaft. The two ends of the shaft rotate, while the disk nutates. The motion of the disk circumference prescribes a portion of a sphere. A portion of the area of the disk is used for intake and compression, a portion is used to seal against a center casing, and the remaining portion is used for expansion and exhaust. The compressed air is admitted to an external accumulator, and then into an external combustion chamber before it is admitted to the power side of the disk. The accumulator and combustion chamber are kept at constant pressures. The engine has a few analogies with piston-engine operation, but like a gas turbine it has dedicated spaces and devices for compression, burning, and expansion. The thermal efficiency is similar to that of comparably sized simple-cycle gas turbines and piston engines. For the same engine volume and weight, this engine produces less specific power than a simple-cycle gas turbine, but approximately twice the power of a two-stroke engine and four times the power of a four-stroke engine. The engine has advantages in the 10 kW to 200 kW power range. This paper introduces the geometry and thermodynamic model for the engine, presents typical performance curves, and discusses the relative advantages of this engine over its competitors.

Turbomachines for application in LOTHECO powerplants (turbomachines for LOTHECO)

The improvement of the technical and economic performance of electric power generation is a continuous effort. An example is the step from simple-cycle (open-cycle) gas turbines to combined-cycle powerplants. Later, STIG and HAT cycles were introduced and, more recently, the LOTHECO concept was proposed. This concept unites features of the standard combined-cycle powerplant and of the HAT cycle by using low-temperature external heat––and not the exhaust energy of the gas turbine––to humidify the high pressure combustion air. (LOTHECO is the acronym for “combined-cycle powerplant with integrated low-temperature heat”.) An obstacle to the introduction of LOTHECO plants is the fact that in their simplest configuration they require newly designed or at least extensively modified gas turbines. This is because the compressor and the turbine mass flow rates, when adjusted to the LOTHECO conditions, are quite different. To improve this situation, alternatives to the original LOTHECO plant concept must be developed. It is found that combinations of standard gas turbines and expanders are solutions almost equivalent in terms of efficiency and specific work to the original LOTHECO plant with an adjusted gas turbine. Less desirable possibilities appear to be combinations of industrial compressors and expanders because of the relatively low inlet temperature of expanders currently available on the market.

New Thermal Governor Model Selection and Validation in the WECC

This is a follow-on paper to A New Thermal Governor Modeling Approach in the WECC (Western Electricity Coordinating Council (WECC) was formerly the Western Systems Coordinating Council (WSCC). Thermal plants embraces conventional fired steam, nuclear steam, simple cycle gas turbine, and combined cycle gas turbine plants. The paper describes the steps being taken to obtain validated data for the new governor models. It was recognized that the developmental database that was created to prove the new thermal governor model should not be used to perform operation or planning studies. Invalid governor data for real-time operation simulations gives rise to risks and liabilities in the determination of intertie limits. Due to the large number of governors involved (about 1100 units) and the short timeline for obtaining data in critical 2003 summer operation studies, a concerted effort is being made to assist generator owners to select and validate the appropriate governor model codes for their units. This effort includes a workshop and the issue of detailed guidelines and validation methodologies for governor modeling.

The Recuperative Auto Thermal Reforming and Recuperative Reforming Gas Turbine Power Cycles With CO2 Removal—Part II: The Recuperative Reforming Cycle

The relatively innovative gas turbine based power cycles R-ATR and R-REF (recuperative–auto thermal reforming GT cycle and recuperative–reforming GT cycle) here proposed, are mainly aimed to allow the upstream CO2 removal by the natural gas fuel reforming. The second part of the paper is dedicated to the R-REF cycle: the power unit is a gas turbine (GT), fuelled with reformed and CO2 cleaned gas, obtained by the addition of several sections to the simple GT cycle, mainly: • reformer section (REF), where the reforming reactions of methane fuel with steam are accomplished: the necessary heat is supplied partially by the exhausts cooling and, partially, with a post-combustion, • water gas shift reactor (WGSR), where the reformed fuel is, shifted into CO2 and H2 with the addition of water, and • CO2 removal unit for the CO2 capture from the reformed and shifted fuel. No water condensing section is adopted for the R-REF configuration. Between the main components, several heat recovery units are applied, together with GT cycle recuperator, compressor intercooler, and steam injection into the combustion chamber. The CO2 removal potential is close to 90% with chemical absorption by an accurate choice of amine solution blend: the heat demand for amine regeneration is completely self-sustained by the power cycle. The possibility of applying steam blade cooling (the steam is externally added) has been investigated: in these conditions, the R-REF has shown efficiency levels close to 43–44%. High values of specific work have been observed as well (around 450–500 kJ/kg). The efficiency is slightly lower than that found for the R-ATR solution, and 2–3% lower than CRGTs with CO2 removal and steam bottoming cycle, not internally recuperated. If compared with these, the R-REF offers higher simplicity due to absence of the steam cycle, and can be regarded as an improvement to the simple GT. In this way, at least 5–6 points efficiency can be gained, together with high levels of CO2 removal. The effects of the reformed fuel gas composition, temperature, and pressure on the amine absorption system for the CO2 removal have been investigated, showing the beneficial effects of increasing pressure (i.e., pressure ratio) on the specific heat demand.

Combined cycle power plant with integrated low temperature heat (LOTHECO)

The major driver to enhance the efficiency of the simple gas turbine cycle has been the increase in process conditions through advancements in materials and cooling methods. Thermodynamic cycle developments or cycle integration are among the possible ways to further enhance performance. The current paper presents the possibilities and advantages from the LOTHECO natural gas-fired combined cycle concept. In the LOTHECO cycle, low-temperature waste heat or solar heat is used for the evaporation of injected water droplets in the compressed air entering the gas turbine's combustion chamber. Following a description of this innovative cycle, its advantages are demonstrated by comparison between different gas turbine power generation systems for small and large-scale applications, including thermodynamic and economic analysis. A commercial gas turbine (ALSTOM GT10C) has been selected and computed with the heat mass balance program ENBIPRO. The results from the energy analysis are presented and the features of each concept are discussed. In addition, the exergy analysis provides information on the irreversibilities of each process and suggested improvements. Finally, the economic analysis reveals that the combined cycle plant with a heavy-duty gas turbine is the most efficient and economic way to produce electricity at base load. However, on a smaller scale, innovative designs, such as the LOTHECO concept, are required to reach the same level of performance at feasible costs.

Conceptional Design Modeling of Combined Power Generation Cycle for Optimum Performance

The present paper studies the general characteristics and evaluates the optimum performance of a simple two-stage compression partial oxidation gas turbine (POGT) cycle that has been combined with a Rankine cycle. The controlling parameters of the combined cycle that give optimum performance are determined and fitted into functional correlation equations. The values of the first-law efficiency and the second-law efficiency (ηI and ηII, respectively) for the combined cycle are compared with those obtained for single POGT cycles. The effects of irreversibilities of the different units of the cycles are considered in the study. The combination of a POGT cycle with the Rankine cycle has achieved a maximum enhancement in net work output of ∼28.76% and optimum values of ηI ≈ 58% and ηII ≈ 80%. The present findings can form a very important basis for a complete phenomenological design of a combined POGT/Rankine cycle to achieve optimum performance.

The Recuperative-Auto Thermal Reforming and the Recuperative-Reforming Gas Turbine Power Cycles With CO2 Removal—Part I: The Recuperative-Auto Thermal Reforming Cycle

The relatively innovative gas turbine based power cycles R-ATR and R-REF (Recuperative–Auto Thermal Reforming GT cycle and Recuperative–Reforming GT cycle) here proposed are mainly aimed to allow the upstream CO2 removal by the way of natural gas fuel reforming. The power unit is a gas turbine (GT), fueled with reformed and CO2 cleaned syngas produced by adding some basic sections to the simple GT cycle: • auto thermal reforming (ATR) for the R-ATR solution, where the natural gas is reformed into CO, H2,CO2,H2O, and CH4; this endothermic process is completely sustained by the heat released from the reactions between the primary fuel CH4, exhausts and steam. • water gas shift reactor (WGSR), where the reformed fuel is, as far as possible, shifted into CO2 and H2 by the addition of water. • water condensation, in order to remove a great part of the fuel gas humidity content (this water is totally reintegrated into the WGSR). • CO2 removal unit for the CO2 capture from the reformed fuel. Among these main components, several heat recovery units are inserted, together with GT cycle recuperator, compressor intercooler, and steam injection in combustion chamber. The CO2 removal potential is close to 90% with chemical scrubbing using an accurate choice of amine solution blend: the heat demand is completely provided by the power cycle itself. The possibility of applying steam blade cooling by partially using the water released from the dehumidifier downstream the WGSR has been investigated: in these conditions, the R-ATR has shown an efficiency range of 44–46%. High specific work levels have also been observed (around 450–550 kJ/kg). These efficiency values are satisfactory, especially if compared with ATR combined cycles with CO2 removal, more complex due to the steam power section. If regarded as an improvement to the simple GT cycle, R-ATR shows an interesting potential if directly applied to a current GT model; however, partial redesign with respect to the commercially available version is required. Finally, the effects of the reformed fuel gas composition and conditions on the amine CO2 absorption system have been investigated, showing the beneficial effects of increasing pressure (i.e., pressure ratio) on the thermal load per kg of removed CO2.

Integration of steam injection and inlet air cooling for a gas turbine generation system

The temperature of exhaust gases from simple cycle gas turbine generation sets (GENSETs) is usually very high (around 500 °C), and a heat recovery steam generator (HRSG) is often used to recover the energy from the exhaust gases and generate steam. The generated steams can be either used for many useful processes (heating, drying, separation etc.) or used back in the power generation system for enhancing power generation capacity and efficiency. Two well-proven techniques, namely steam injection gas turbine (STIG) and inlet air cooling (IAC) are very effective features that can use the generated steam to improve the power generation capacity and efficiency. Since the energy level of the generated steam needed for steam injection is different from that needed by an absorption chiller to cool the inlet air, a proper arrangement is required to implement both the STIG and the IAC features into the simple cycle GENSET. In this study, a computer code was developed to simulate a Taipower’s Frame 7B simple cycle GENSET. Under the condition of local summer weather, the benefits obtained from the system implementing both STIG and IAC features are more than a 70% boost in power and 20.4% improvement in heat rate.

Hybrid systems for distributed power generation based on pressurisation and heat recovering of an existing 100 kW molten carbonate fuel cell

In this paper, different pressurisation and heat recovering techniques for an existing 100 kW molten carbonate fuel cell developed by Ansaldo fuel cells (formerly Ansaldo Ricerche) such as electrically driven compressors for anode (fuel) and cathode side (air), turbocharger, simple cycle gas turbine and regenerated gas turbine are analysed and discussed. The analysis has been carried out using for the FCS–MCFC stack simulation a model developed by the Thermochemical Power Group of the University of Genoa carefully tested with available experimental design point data. The design point hybrid system configurations have been analysed in detail using the code HS-MCFC based on the cited MCFC stack model and developed using Simulink language [Master Thesis, University of Genoa, 2001]. The different hybrid systems design point performance are presented and discussed in great detail, taking into account efficiency, specific power, costs, feasibility, and the need of modification of the existing FC–MCFC systems. Due to the size of the hybrid systems investigated (100–150 kW) they are very interesting for distributed power generation applications.

Siemens posts power plant orders worth €1.3 billion

With a high back-work ratio and a high exhaust-temperature, the simple cycle gas-turbine generation system usually has a low generation-efficiency especially when the ambient weather is hot. Among many technologies to improve the efficiency of a simple-cycle gas-turbine, inlet-air cooling, and steam reinjection are considered the best ways to modify an existing simple cycle unit without major destruction to its original integrity. To evaluate the individual effects after system modifications, a computer code for the simulation of the power-generation system was developed and validated in this study, and the ABSIM code developed by Oak Ridge National Laboratory was adopted to simulate the absorption refrigeration system. Based on the calculated improvement and the associated benefits, the estimated cost of refurbishment and other operational costs, economic analyses were performed under the current fuel and cost structures. Results indicate that the system with the steam reinjection feature has the highest generation-efficiency and thus the most potential profit on investment, while the system with both inlet-air cooling and steam reinjection features can generate the highest power-output and release the least exergy via the flue gases.

가스터빈의 설계 성능과 부분부하 성능 사이의 상관관계 분석

This study analyzed the dependence of part load performance of simple cycle gas turbines on their design performance. Various parametric calculations were carried out to examine effects of design temperature ratio, pressure ratio and component efficiencies using a simplified analysis. In addition, a more practical analysis was done for realistic design conditions with the aid of a comprehensive performance analysis program. The results show that gas turbines with higher design performance exhibit less efficiency degradation during part load operation. The influence of power control method (fuel only centre) and air flow control) on part load performance was examined as well.

Performance improvement for a simple cycle gas turbine GENSET––a retrofitting example

Due to the serious power shortage in Taiwan, many simple cycle gas turbine generation sets (GENSETs) that were originally designated to serve as peak load units are forced to operate continuously during the entire summer season. The retrofitting projects have been seriously considered to convert these GENSETs (which have the advantage of fast startup, but suffer from low power output and thermal efficiency at high ambient temperature) into more advanced cycle units with higher efficiency and higher output. Among many proven technologies, such as inlet air cooling, intercooling, regeneration, reheating and steam-injection gas turbine (STIG) etc., STIG is found to be one of the most effective in boosting both the output capacity and thermal efficiency. The results from computer simulation indicated that the retrofitting of existing GE Frame 6B simple cycle unit into STIG cycle can boost the output from about 38 to 50 MW, while the generation efficiency can be increased from about 30% to 40%. Besides, the power output of STIG cycle is less sensitive to ambient temperature than that of simple cycle. NO x reduction to less then 25 ppm (when LNG is used) and operating flexibility under variable heat demand could be achieved.

Industrial applications of the air bottoming cycle

An air bottoming cycle (ABC) was proposed in the late 1980s as an alternative for the conventional steam bottoming cycle. Now this cycle is being considered as a compact and simple bottoming cycle in various applications: as an upgrading option for simple-cycle gas turbines in the offshore industry; as a hot-air cogeneration plant; or as a heat recovery installation at high-temperature furnaces. This paper evaluates the technical and economic feasibility of the ABC in the cogeneration scheme, where hot air from the air turbine is supplied to food processing industries (industrial bakeries and milk powder factories). Another application is the heat recovery unit of a glass-melting furnace. In this option the air turbine driven by waste heat also provides pre-heated air to the furnace. Based on the results of this study, two demonstration projects are scheduled for realization with support from a governmental agency and industrial partners.

Bayer to cut further jobs

The waste heat recovery (HR) systems are employed to increase the overall thermal efficiency of electric generation units (EGUs). Although the emission factors (in terms of gram of pollutants per unit of thermal energy consumed or electric energy generated) generally decreases after installing HR systems, the emission rates in terms of grams of pollutants per unit of time remain unchanged. However, HR systems reduce stack exit temperature, resulting in lower effective emission heights, which lead to higher near-source ground level concentrations (GLCs) of air pollutants. In order to comprehensively evaluate the near-source air quality impact from deploying HR systems, we proposed a new modeling framework by integrating a computationally efficient Gaussian-based dispersion model (AERMOD) and a (relatively) more accurate computational fluid dynamics (CFD) model. As a demonstration of the proposed framework, we investigated the HR impact on NOx concentrations near a simple cycle gas turbine located in Brentwood, NY. Specifically, we applied the AERMOD modeling system to screen the hourly GLCs over five years, and highest values (and the corresponding hours) were shown to cluster into two main meteorological conditions: the stable atmospheric boundary layer with relatively high wind speed (Stable, HW) and the unstable atmospheric boundary layer with relatively low wind speed (Unstable, LW). These two conditions were further simulated using a CFD model that have been extensively evaluated previously for detailed analysis. By setting different stack exit temperatures, the near-source air quality impact of different waste heat conversion rates was evaluated. We introduced a concept called the heat recovery amplified factor (HRAF), defined as the ratio between the maximum GLC with HR system and that without HR system, as an indicator of HR impact. HRAF was shown to be much more sensitive to temperature in the Unstable, LW condition than in the Stable, HW condition. Although the results were limited to a specific simple cycle gas turbine, the proposed modeling framework and HRAF can be used for evaluating the HR systems impact for other emission sources.

Influence of ambient condition on thermodynamic performance of the humid air turbine cycle

The role of ambient conditions in determining the thermodynamic performance of the Humid Air Turbine (HAT) cycle is analyzed by comparing the HAT cycle's performance variations with those manifested by the simple gas turbine cycle and the combined cycle. Turbine work has been found to increase as ambient temperature increases. This is because larger amounts of water vapor can be added to the airflow in the humidifier. As this effect counteracts the increase of compressor work, the net specific work that results is held almost constant regardless of the variation in ambient temperature. It is revealed that as ambient temperature increases, the HAT cycle may have more favorable power variations than the combined cycle.

A new analysis of recuperative gas turbine cycles

It is shown that the classical recuperator effectiveness is not an appropriate evaluation criterion for the gas turbine recuperator or a suitable independent thermodynamic parameter of the recuperative gas turbine cycle. Another parameter—the average heat transfer temperature difference in the recuperator—is recommended as the new criterion instead of the recuperator effectiveness. Therefore, the original classical analysis results of the recuperative gas turbine cycle are also inappropriate and it is necessary to give a new analysis. In this paper, the analytical expressions of the simple recuperative cycle efficiency and the optimum pressure ratio based on the new criterion are derived from general simplified assumptions. Some typical calculation results are also presented. With this new criterion, the optimum pressure ratio values for efficiency of a simple recuperative gas turbine cycle do not vary very much with the temperature ratio and are approximately equal to 3, much lower than the figures generally recognized before. A similar analysis for the recuperative gas turbine cycle with intercooler and reheater and an analysis ensuring approximately constant recuperator heat transfer area per unit power output are given also.

A comparison between the hat cycle and other gas-turbine based cycles: Efficiency, specific power and water consumption

The search for improved power cycles leads to various gas-turbine based cycles with very different characteristics and complexities, ranging from the traditional recuperated gas-turbine cycle to complexes' combinations of components such as intercooled compression, compressed air aftercooling, recuperation and/or reheat. In this work the HAT cycle (humid air turbine) is compared with the simple-cycle gas-turbine, the recuperated (and the intercooled-recuperated) gas-turbine cycles, the STIG (steam injection gas-turbines) and also with the combined-cycle. The focus of comparison is also put on the needed water quality and consumption, as well as on performance and emissions. The efficiency and/or specific power production advantages of each analyzed cycle are weighted against the cycle complexity, specific emissions and water needs. The different degrees of water purity for each use are also discussed and a differentiation is made between water circulation and water consumption. The possible best-range of applicability is addressed to each cycle, taking into account the power plant size and also the gas-turbine classical operating parameters as pressure ratio, turbine inlet temperature and operation profile.

Diurnal Thermal Energy Storage For Cogeneration Applications

Thermal energy storage can help cogeneration meet the chal-lenges of the 1990s by increasing the flexibility and performance ofcogeneration facilities . Thermal energy storage also allows a cogenera-tion facility to provide dispatchable electric power while providing aconstant thermal load.The first of two studies reported here focused on the relativeperformance and economic benefits of incorporating a diurnal TESsystem with a simple-cycle gas turbine cogeneration system to producedispatchable power during peak- and/or intermediate -demand periods.The r esults showed that the oil/rock storage system for TES was themost attractive option for the assumed thermal load quality .The second study evaluated the cost of power produced by acombined-cycle cogeneration plant integrated with thermal energystorage (CClr ES/Cogen ). The results indicate relatively poor economicprospects for int egrating TES with a combined-cycle cogenerationpower plant. However, system design optimization and reductions instorage media costs might improve the economics, perhaps enough tomake the CClrES/Cogen an attractive option for incremental peakpower production.In addition to the economic considerations, environmental factorsdue to the use of thermal energy storage with conventional cogenera-tion syst ems are also reported .

Analysis of a small steam injected gas turbine system with heat recovery

This paper describes a methodology and results for the analysis of a small steam injected gas turbine cogeneration system. A performance analysis program for the gas turbine engine is utilized with modifications required for the model of steam injection and the heat recovery steam generator (HRSG). The object of simulation is a simple cycle gas turbine engine under development which adopts a centrifugal compressor. The analysis is based on the off-design operation of the gas turbine and the compressor performance map is utilized. Analyses are carried out with the injection ratio as the main parameter. The effect of steam injection on the power and efficiency of gas turbine and cogeneration capacity is investigated. Also presented is the variation in the main operating parameters inside the HRSG. Remarkable reduction in NOx generation by steam injection is confirmed. In addition, it is observed that for the 100% power operation the temperature of the cooled first nozzle blade decreases by 100.deg. C at full steam injection, which seems to have a favorable effect on the engine life time.