Efficiency Of Gas Turbine Cycle Research Articles

Sensitivity of transpiration cooled gas turbine cycle efficiency and coolant requirement to changes in cooling parameters

The maximum temperature at the gas turbine inlet gets restricted due to metallurgical constraints, which can be increased using blade cooling. Among different techniques for cooling blades in the gas turbine, the transpiration cooling of blades permits quite a high temperature at the turbine inlet. The objective of this study is to analyse the sensitivity of transpiration cooled gas turbine cycle performance for cooling parameterssuch as allowable blade material temperature, film cooling effectiveness, and internal cooling efficiency, so that the most important cooling parameters may be focused upon for the improvement of gas turbine cycle performance. In this study, it is found that the cycle efficiency is more sensitive to allowable blade material temperature followed by film cooling effectiveness and to internal cooling efficiency only a little bit. This study shows that with the use of cooling, for an increase in allowable blade temperature by 50 K, the gas turbine cycle efficiency increases by 0.15% . Also, the increase in film cooling effectiveness from 0.4 to 0.5 increases the cycle efficiency by 0.13% . Furthermore, with an increase in cooling efficiency from 0.7 to –0.8 the cycle efficiency increases by 0.03% only.

Simulation and optimization of a combined cycle power plant with low heating value fuel gas

Combined cycle power plant (CCPP) usually plays an important role in balancing byproduct gas generation and consumption in integrated iron and steel plant. The low heat value fuel gases, such as blast furnace gas (BFG) or mixed gas with Coke oven gas (COG) and BFG, are preferred to be used in high-efficient CCPP for power generation. In practice, the general heat value of mixed gas can be set in the range of 3500–4400[Formula: see text]kJ/Nm3. This paper presents a methodology to simulate operating parameters of CCPP with BFG. A generic model of gas turbine with open loop stage cooling employing air is used to simulate the performance of gas turbines cycle under different compressor pressure ratios and turbine inlet temperatures (TIT). The isentropic efficiencies for gas compressor and gas turbine are supposed to be constants and set corresponding to published industrial experience. The steam cycle is composed of classical double-pressure heat recovery steam generator (HRSG) and steam turbines according to gas turbine outlet temperature. Specific work, gas turbine cycle efficiency, cogeneration thermal efficiency and coolant air flow requirements are evaluated to find the optimal compressor pressure ratio and TIT. The research results are useful to select the optimum operating parameters of CCPP with BFG. Performance features were estimated with the help of compression ratios 12.5–20 and combustor exit temperature 1150–1350[Formula: see text]C.

Fault diagnosis analysis and health management of thermal performance of multi-source data fusion equipment based on fog computing model

Waste heat boiler will be restricted by the exhaust parameters of gas turbine, at the same time, it will affect the thermal characteristics of steam side, and its flue gas resistance will directly affect the power and efficiency of gas turbine cycle, which will have an important impact on the efficiency of combined cycle system. Therefore, it is necessary to monitor the running status of the equipment in time, identify the early signs of faults, and make accurate judgments on fault location, fault degree and development trend, so as to improve the reliability and availability of the unit. The thermal system is the main part of thermal power plant production, so the fault diagnosis of this part is particularly important. In this paper, a method of thermal performance fault diagnosis and health management for multi-source data fusion equipment based on fog computing model is proposed. Using the theory of multi-source data fusion analysis, the qualitative values of the parameters of the fog computing model are marked, and the causes of the failure of the failure variables are obtained. Complete the fault subspace identification, and comprehensively evaluate the equipment status according to multi-attribute decision. This method is conducive to the accurate identification of early faults and the accurate judgment of fault degree and fault trend

Parametric Shape Optimization of Pin-Fin Arrays Using a Surrogate Model-Based Bayesian Method

Pin-fin arrays are generally present in trailing-edge regions of gas-turbine blades for internal cooling purposes. An elevated temperature is important to enhance the thermodynamic efficiency of gas-turbine cycles, and internal blade-cooling mechanisms are employed to mitigate material failure at these high temperatures. It is also important to have high heat transfer at a limited pressure drop to ensure that the overall cycle efficiency is not affected by power loss from driving the flow through internal cooling circuits. A pin-fin shape optimization has been carried out, with the array performance efficiency factor as the objective function, using surrogate modeling-based Bayesian methods. Surrogate modeling/machine learning approaches are instrumental in exploring global solutions to optimization problems using an exploration versus exploitation approach. This ensures prudent use of computational resources for computationally expensive computational fluid dynamics simulations. By varying geometric parameters of the pin fins, a three-dimensional design space has been explored to obtain an optimum pin-fin shape that has the maximum efficiency in the developing region of the flow. An improvement in the efficiency parameter of 1.4 times that of the baseline was obtained in a three-row pin-fin case, and the results were compared with those of genetic-algorithm-based optimization (nondominated sorted genetic algorithm–II). Computation time for optimization was saved by 52%, as an optimum was obtained at lower number of iterations when compared to the genetic algorithm approach, with a 1.2% higher objective function value. This shows an improvement in performance of the current novel approach compared to another stochastic method.

A method for modelling compressor bleed in gas turbine analysis software

The modelling of compressor interstage bleed in a gas turbine is required at all phases of the engine design cycle. The effect of the physical geometry of the bleed offtake on compressor flow is an important consideration, but of equal importance is the analysis of the effect of bleed air on compressor work requirements and overall gas turbine cycle efficiency. Knowledge of bleed air properties (temperature, pressure, work) is of paramount importance to carry out a reliable preliminary cycle analysis.While interstage bleed modelling may be regarded as a small detail in the overall gas turbine cycle, it is of increasing importance in modern engine design due to the requirement to obtain performance optimisation in engines that have already had significant development. Consequently, even small improvements to the modelling process can yield beneficial improvements to the engine cycle.Current methods to identify these effects vary in terms of complexity and accuracy; in this paper, a novel method is proposed, which offers an innovative -yet simple- way to simulate any number of interstage bleeds within a compressor, without the need to compromise on model accuracy. This is achieved through implementation of two methods - 1) properties of the bleed air are calculated by utilising the polytropic relationship between pressure and temperature, and 2) compressor work requirements are calculated by use of the “superposition principle” by implementing the work requirements of the bleed into an initial ‘no bleed’ calculation. This method has been implemented in the Cranfield modelling software Turbomatch, and validated against test data from an industrial gas turbine. Analyses so far show that the method is quick, accurate, and compares extremely well to the test data.This novel, ‘integrated’ method has been shown to calculate interstage bleed properties in a gas turbine compressor without the need for complex modelling or artificial ‘splitting’ of components. This method is partially dependent on the assumption that stage pressure ratio can be estimated using constant stage temperature rise and compressor overall polytropic efficiency (although the use of overall isentropic efficiency was also investigated). Case studies performed on a number of Siemens industrial gas turbines suggest this is indeed the case, with calculated stage inlet/outlet pressure typically within 3% of the real engine comparison, although older technology compressors tend to be modelled less accurately than newer ones.For compressor work and overall cycle calculation, comparison of this method against test data shows that accuracies between 0.5% and 1% can be obtained down to low load conditions. Compared to compressor ‘splitting’ methods, which demonstrated relatively poor accuracy levels (above 20%), likely due to inaccurate compressor map selection, the alternative method is shown to be a suitable method to model bleed without the need for extensive manual model adjustment. It is also shown how this method can be used to quickly assess the effect of bleed stage and mass flow on the compressor running line, as well as on the surge margin.It should be noted that, while the engines used in the case study represent different engine designs and technology levels, they are from the same engine manufacturer and represent a gradual evolution of compressor technology using a similar design philosophy.

Three-dimensional optimal design of a cooled turbine considering the coolant-requirement change

Abstract Cooling technology is widely applied in modern turbines to protect the turbine blades, and extracting high-pressure cooling air from a compressor exerts a remarkable influence on the gas-turbine performance. However, the three-dimensional optimal design of a turbine in modern industrial practice is usually carried out by pursuing high component efficiency without considering possible changes in coolant requirement; hence, it may not exactly lead to improvement in the gas-turbine cycle efficiency. In this study, the turbine stator was twisted and leaned to achieve higher comprehensive efficiency, which is the cycle-based efficiency definition for a cooled turbine that considers both turbine aerodynamic performance and coolant requirement. First, the influence of twist and compound lean on turbine aerodynamic performance, considering stator-hub leakage, was investigated. Then, a method to predict the coolant requirement for turbines with different stator designs was applied, to evaluate coolant-requirement change at the design condition. The optimized turbines were finally compared to demonstrate the necessity of considering the coolant-requirement change in the optimal design. This indicated that proper twisting to open the throat area in the stator hub and compound lean to the pressure surface side could help improve the cooled-turbine comprehensive efficiency.

Influence of Different Biofuels on the Efficiency of Gas Turbine Cycles for Prosumer and Distributed Energy Power Plants

The efficiency of a gas turbine can be affected by the use of different biofuels usually with a relatively Lower Heating Value (LHV). The paper evaluates the impact of calorific value of fuel on turbine performance and analyzes the possibilities of optimizing turbine construction from the point of view of maximum efficiency for a particular fuel. The several variants of design of small power microturbines dedicated to various biofuels are analyzed. The calculations were carried out for: gas from biomass gasification (LHV = 4.4 MJ/kg), biogas (LHV = 17.5 MJ/kg) and methane (LHV = 50 MJ/kg). It is demonstrated that analyzed solution enables construction of several kW power microturbines that might be used on a local scale. Careful design of such devices allows for achieving high efficiency with appropriate choice of the turbine construction for specific fuel locally available. Such individually created generation systems might be applied in distributed generation systems assuring environmental profits.

Simulation Analysis of Performance of Nuclear-Gas Combined Cycle Power Generation Systems

For the low cycle thermal efficiency of Pressurized Water Reactor(PWR) nuclear power units and the growing demand on the nuclear power peaking capacity of the power grid, using Ebsilon software, based on the thermodynamic system model of the secondary loop of Daya Bay Nuclear Power Station, the nuclear-gas combined cycle power generation thermodynamic system is established. Taking the gas turbine cycle efficiency and the combined cycle efficiency as the index of the heat economy, the performance of the combined cycle system is evaluated. At the same time, the effect of ambient temperature, pressure and gas turbine load on the system performance is analyzed. The results show that, the thermal efficiency of the nuclear-gas combined cycle system increased by 13.15% compared with the original nuclear power unit, the output power of the steam turbine increased by 75.49%, and the working environment of the steam turbine is improved obviously; The fall of ambient temperature will increase the efficiency and the power of the gas turbine, and the drop in ambient pressure will decrease the efficiency of the gas turbine and the combined cycle efficiency. When reducing the load of the gas turbine, the inlet temperature of nuclear reactor remains unchanged by afterburning the natural gas, and the steam turbine can still have high output power. The adjustable range of the load is from 56.57 % to 100%.

Investigation on humidified gas turbine cycles with Maisotsenko-cycle-based air saturator

The urge for more energy-efficient power plant systems triggered the design for more advanced power cycle designs. The current simple cycle gas turbine shows its advantage on cost but does not fully exploit the energy available in the flue gas. In this paper, two more efficient humidified gas turbine cycles were investigated. Type 1 was a hybrid design which combined an indirect evaporative cooler with a Maisotsenko cycle and Type 2 a conventional indirect evaporative cooler as air saturator. The simulation results indicated how the operating conditions such as pressure ratio and air flow changed with the designs. Both humidified gas turbine cycle systems offered better system efficiencies than a conventional gas turbine system with recuperator and the application of Maisotsenko cycle based air saturator could further improve the gas turbine cycle efficiency. Parametric studies were also conducted which highlighted the effects of water injection rate and part-load ratio on the comparative performances of the different humidified gas turbine cycle designs.

Energetical, exergetical and economical optimization analysis of combined power generation system of gas turbine and Stirling engine

One of the promising methods to increase exergoeconomic performance and decrease effects of environmental adverse of energy systems is integration of energy systems. Gas turbine power plant is one of the favorable power generation systems because of its acceleration in start-up and low investment cost. However, the thermal efficiency of gas turbine cycle is low because of the significant heat loss due to high-temperature effluent gas exhausted from the stack. Therefore, if this huge heat loss is recovered by another heat engine coupled with gas turbine cycle the total efficiency will increase, considerably. Stirling engine owing to its high efficiency is one of the promising candidates which can be used as a part of the combined system. Hence, an optimization analysis on standalone gas turbine cycle, as well as combined cycle of gas turbine and Stirling engine are considered in this paper to find out the optimal operational point, thermodynamically and economically. Both single-objective and multi-objective genetic algorithm is performed to optimize the overall plant parameters, subjecting three optimization scenarios of maximizing exegetic efficiency, minimizing levelized cost of electricity and exergo-economic optimization. A comprehensive comparison of gas turbine and Stirling engine combined cycle and standalone gas turbine cycle was performed for these optimization scenarios. Results show a significant improvement in power output and reduction of levelized cost of electricity in combined cycle of gas turbine and Stirling engine. In the optimal point of this hybrid system, levelized cost of electricity reduces by 10.3% and exergetic efficiency improves by 16.1% compared with the optimal point of standalone gas turbine cycle.

Analytical calculation of adiabatic processes in real gases

The impact of gases nonideality in the compression and expansion processes on the specific heat ratio and the heat capacity is analyzed. The specific heat ratio variation leads to temperature variation during compression in the compressor and expansion in the turbine and, consequently, the gas turbine cycle efficiency factor variation. It is also essential to consider the gases nonideality in the compression and expansion processes in the compression processes in compressor. Generally it is assumed during calculations that the heat capacities depend only on temperature, in this case the reference data presented by various authors differs markedly. In the real processes the heat capacity and the specific heat ratio depend on temperature and within the particular temperatures and pressures range depend on pressure. Consequently, the operating fluid nonideality in the gas turbine cycle should be considered.

Thermodynamic assessment of impact of inlet air cooling techniques on gas turbine and combined cycle performance

The article is focused on the comparison of impact of two different methods of inlet air cooling (vapor compression and vapor absorption cooling) integrated to a cooled gas turbine based combined cycle plant. Air-film cooling has been adopted as the cooling technique for gas turbine blades. A parametric study of the effect of compressor pressure ratio, compressor inlet temperature (Ti,C), turbine inlet temperature (Ti,T), ambient relative humidity and ambient temperature on performance parameters of plant has been carried out. Optimum Ti,T corresponding to maximum plant efficiency of combined cycle increases by 100 °C due to the integration of inlet air cooling. It has been observed that vapor compression cooling improves the efficiency of gas turbine cycle by 4.88% and work output by 14.77%. In case of vapor absorption cooling an improvement of 17.2% in gas cycle work output and 9.47% in gas cycle efficiency has been observed. For combined cycle configuration, however, vapor compression cooling should be preferred over absorption cooling in terms of higher plant performance. The optimum value of compressor inlet temperature has been observed to be 20 °C for the chosen set of conditions for both the inlet air cooling schemes.

Thermodynamic Evaluation of Gas/Steam Combined Cycle Performance With Active Controlled Film Cooling

Efficiency of gas turbine cycles can be improved by increasing the turbine inlet temperature. Advanced gas turbines operate at temperatures far above their material limitations to increase thermal efficiency. So, film cooling technique is mostly used to protect the gas turbine blades from high temperature gases. The film cooling jets penetrate into the mainstream gas and form a thin film for protecting the blade surfaces from hot gas. However, due to lift-off effect the attachment of the coolant jet to the blade wall, downstream, becomes crucial. Plasma actuator strategy proposed by some of the researchers may be considered to be utilized, to maintain the attachment of jet with the blade-wall and improve the film cooling effectiveness. In this article the effect of a proposed active controlled film cooling technique using plasma actuator strategy on thermodynamic performance of gas/steam combined cycle has been evaluated and compared with the combined cycle employing simple film cooling technique as well as with advanced transpiration cooling technique of gas turbine blades. Reduced coolant requirement and hence reduced dilution losses with active controlled film cooling as compared to simple film cooling, results in improved topping as well as bottoming cycle performance. It is seen that the combined cycle efficiency with active film cooling is comparable to the transpiration cooled combined cycle efficiency. At a turbine inlet temperature (TIT) of 1900 K, the combined cycle efficiency with active film cooling strategy is higher by 0.5% than that with simple film cooling.

EFFECT OF AMBIENT TEMPERATURE ON THE PERFORMANCE OF A COMBINED CYCLE POWER PLANT

The aim of the present paper is to examine the effect of ambient temperature on the performance of a combined cycle power plant. For this work, the combined cycle plant chosen is NTPC (National Thermal Power Corporation) Dadri, India where a gas unit of 817 MW is installed. The effect of ambient temperature on combined cycle efficiency, gas turbine cycle efficiency, exergy destruction in different components, exergy loss via exhaust and air fuel ratio at lower and higher turbine inlet temperature are reported. The results show that the net decrease in combined cycle efficiency is 0.04% and the variation in exergy destruction of different plant components is up to 0.35% for every °C rise in ambient temperature.

Computational analysis of mist/air cooling in a two-pass rectangular rotating channel with 45-deg angled rib turbulators

Increasing the turbine inlet temperature can increase the gas turbine cycle efficiency. In order to increase the turbine inlet temperature significantly, an advanced cooling system has to be essentially developed. Injection of mist to the coolant fluid is considered a promising technique to protect the hot components such as combustor liners, combustor transition pieces, and turbine vanes and blades. A series of experiments conducted in the past proved the success of mist cooling technology in the laboratory environment. Favorable results from the numerical simulation further encourage continuous exploration of employing mist-cooling technology in the actual gas turbine working environment in various applications. The present study focuses on applying mist cooling to the rotating mist/air internal cooling passage with rib turbulators using numerical simulation.In the first part, the computational fluid dynamics (CFD) models of smooth and ribbed channels without mist and rotation are validated with the experimental results available in literature. The agreement between the predicted and experimental values in the lower Reynolds number (Re) range is within 3% deviation, and, at higher Re range, the deviation is about 10%. For the smooth channel, the agreement with experimental result is good for the entire range of Re values. In the second part, the rotational effect on the smooth and ribbed channels is predicted and analyzed. In the last part, the mist cooling enhancement on the ribbed channel with rotation is simulated. The secondary flows created due to channel bend and rotation are specifically analyzed. The results show that the mist cooling enhancement is about 30% at the trailing surface and about 20% at the leading surface of the first passage with 2% mist injection. In the second passage, 20% enhancement is predicted for both the surfaces.

Low NOx Advanced Vortex Combustor

A lean-premixed advanced vortex combustor (AVC) has been developed and tested. The natural gas fueled AVC was tested at the U.S. Department of Energy’s National Energy Technology Laboratory in Morgantown, WV. All testing was performed at elevated pressures and inlet temperatures and at lean fuel-air ratios representative of industrial gas turbines. The improved AVC design exhibited simultaneous NOx∕CO∕unburned hydrocarbon (UHC) emissions of 4∕4∕0ppmv (all emissions corrected to 15% O2 dry). The design also achieved less than 3ppmvNOx with combustion efficiencies in excess of 99.5%. The design demonstrated marked acoustic dynamic stability over a wide range of operating conditions, which potentially makes this approach significantly more attractive than other lean-premixed combustion approaches. In addition, the measured 1.75% pressure drop is significantly lower than conventional gas turbine combustors, which could translate into an overall gas turbine cycle efficiency improvement. The relatively high velocities and low pressure drop achievable with this technology make the AVC approach an attractive alternative for syngas fuel applications.

Raising cycle efficiency by intercooling in air-cooled gas turbines

The working temperature of a gas turbine, necessary to achieve high efficiency, makes cooling of the first turbine stages unavoidable. Air and steam can be used for cooling. A model for an air-cooled gas turbine based on the work of Young and Wilcock [J.B. Young, R.C. Wilcock, ASME J. Turbomachinery 124 (2002) 207–221] is implemented in Aspen™. Simple cycle calculations with realistic parameters of current machines are made and confirm the results of Wilcock et al. [R.C. Wilcock, J.B. Young, J.H. Horlock, ASME J. Eng. Gas Turb. Power 127 (2005) 109–120] that increasing the turbine inlet temperature no longer means an increase in gas turbine cycle efficiency. This conclusion has important consequences for gas turbines because it breaks with the general accepted trend of increasing the TIT. An intercooled gas turbine cycle is intensively investigated, taking the turbine cooling into account. Intercooling not only lowers the work of compression, but also lowers cooling air temperatures. The major influences of the intercooling on the gas turbine cycle are mapped and explained. Optimum intercooling pressure for maximum gas turbine cycle efficiency is much lower than halfway compression. A simulation of the LMS100, the most recent gas turbine on the market from GE Energy, is made to verify the simulation methodology. The claimed intercooled cycle efficiency of 46% is confirmed. Further increasing the pressure ratio and TIT can still improve the performance of the intercooled gas turbine cycle.