Analysis Of Gas Turbine Cycle Research Articles

Comparative study of numerical approaches to adaptive gas turbine cycle analysis

Abstract Significant increase in task complexity for modern gas-turbine propulsion systems drives the need for future advanced cycles’ development. Further performance improvement can be achieved by increasing the number of engine controls. However, there is a lack of cycle analysis tools, suitable for the increased complexity of such engines. Towards bridging this gap, this work focuses on the computation time optimization of various mathematical approaches that could be implemented in future cycle-solving algorithms. At first, engine model is described as a set of engine variables and error functions, and is solved as an optimization problem. Then, the framework is updated to use advanced root-finding paradigms. Starting with Newton-Raphson, the model is improved by applying Broyden’s and Miller’s schemes and implementing solution existence validation. Finally, algorithms are compared in representative condition using increasingly complex turbojet and adaptive cycle turbofan configurations. As evaluation cases become more time consuming, associated time benefits also improve.

Comparative study of numerical approaches to adaptive gas turbine cycle analysis

Abstract Significant increase in task complexity for modern gas-turbine propulsion systems drives the need for future advanced cycles’ development. Further performance improvement can be achieved by increasing the number of engine controls. However, there is a lack of cycle analysis tools, suitable for the increased complexity of such engines. Towards bridging this gap, this work focuses on the computation time optimization of various mathematical approaches that could be implemented in future cycle-solving algorithms. At first, engine model is described as a set of engine variables and error functions, and is solved as an optimization problem. Then, the framework is updated to use advanced root-finding paradigms. Starting with Newton-Raphson, the model is improved by applying Broyden’s and Miller’s schemes and implementing solution existence validation. Finally, algorithms are compared in representative condition using increasingly complex turbojet and adaptive cycle turbofan configurations. As evaluation cases become more time consuming, associated time benefits also improve.

On The Thermodynamics of Dual Purpose Power Desalting Plants with Gas Turbine.(Dept.M)

Recent advances in gas turbine cycles and combined gas/steam turbine cycles are presented. First and second law analysis of gas turbine cycles is presented and shows that substantial available energy (up to 30% of fuel availability) is carried out by gas turbine exhaust gases. This available energy can be utilized for further heat to work conversion or for direct process heating. Heat recoverd from gas turbine exhaust gases in heat recovery steam generator (HRSG) can generate relatively high pressure steam to be supplied to Rankine steam power cycle to form gas/steam power cycle of high efficiency (40-45%). Steam can be generated at low pressure in the HRSG for direct supply to the brine heater of a multistage flash (MSF) desalting system. Possible combination of simple gas turbine cycle or combined gas/steam cycle with reverse osmosis or MSF sea water desalting systems are presented and evaluated. The evaluation indicates that most of these combination are more superior than combination with steam power plants from energy view points.

Pulsed Impingement Turbine Cooling and Its Effect on the Efficiency of Gas Turbines With Pressure Gain Combustion

Abstract Performance improvements of conventional gas turbines are becoming increasingly difficult and costly to achieve. Pressure gain combustion (PGC) has emerged as a promising technology in this respect, due to the higher thermal efficiency of the respective ideal gas turbine cycle. Previous cycle analyses considering turbine cooling methods have shown that the application of pressure gain combustion may require more turbine cooling air. This has a direct impact on the cycle efficiency and reduces the possible efficiency gain that can potentially be harvested from the new combustion technology. Novel cooling techniques could unlock an existing potential for a further increase in efficiency. Such a novel turbine cooling approach is the application of pulsed impingement jets inside the turbine blades. In the first part of this paper, results of pulsed impingement cooling experiments on a curved plate are presented. The potential of this novel cooling approach to increase the convective heat transfer in the inner side of turbine blades is quantified. The second part of this paper presents a gas turbine cycle analysis where the improved cooling approach is incorporated in the cooling air calculation. The effect of pulsed impingement cooling on the overall cycle efficiency is shown for both Joule and PGC cycles. In contrast to the authors’ anticipation, the results suggest that for relevant thermodynamic cycles pulsed impingement cooling increases the thermal efficiency of Joule cycles more significantly than it does in the case of PGC cycles. Thermal efficiency improvements of 1.0 p.p. for pure convective cooling and 0.5 p.p. for combined convective and film with TBC are observed for Joule cycles. But just up to 0.5 p.p. for pure convective cooling and 0.3 p.p. for combined convective and film cooling with TBC are recorded for PGC cycles.

Environmental impact and cost analysis of gas turbine cycles with steam injection and inter-stage turbine reheat

Inter-stage turbine reheat is an effective gas turbine retrofit which can easily be used with simple and steam injected gas turbines as well. Owing to the uncertainties relating to an efficiency comparison of steam injected and no-injection cycle designs, thermoeconomics and environmental impacts have been considered to evaluate reheat and steam injection which regards pollutant emissions and environmental costs together. Being the complemental of the authors previous studies on steam injected gas turbines, simple, reheat, steam injected (STIG) and reheat steam injected (RHSTIG) gas turbine cycles are compared. Economic feasibility of steam injection as well as inter-stage turbine reheat are discussed according to 2018 plant cost data. Optimal cycle parameters are determined using a new comprehensive cycle model which permits to work with realistic working fluids, simulates the combustion process regarding 14 exhaust species and determines NOx and CO emissions.

Environmental impact and cost analysis of gas turbine cycles with steam injection and inter-stage turbine reheat

Inter-stage turbine reheat is an effective gas turbine retrofit which can easily be used with simple and steam injected gas turbines as well. Owing to the uncertainties relating to an efficiency comparison of steam injected and no-injection cycle designs, thermoeconomics and environmental impacts have been considered to evaluate reheat and steam injection which regards pollutant emissions and environmental costs together. Being the complemental of the authors previous studies on steam injected gas turbines, simple, reheat, steam injected (STIG) and reheat steam injected (RHSTIG) gas turbine cycles are compared. Economic feasibility of steam injection as well as inter-stage turbine reheat are discussed according to 2018 plant cost data. Optimal cycle parameters are determined using a new comprehensive cycle model which permits to work with realistic working fluids, simulates the combustion process regarding 14 exhaust species and determines NOx and CO emissions.

Sir William Rede Hawthorne. 22 May 1913—16 September 2011

William Rede Hawthorne was a pioneer in gas turbine aerodynamics and thermodynamics, a sought-after technology advisor to industry and government, and a generous and enthusiastic teacher who encouraged students to excel. His outstanding contributions included resolution of combustion problems that limited the operation of the original Whittle jet engine, early in-depth descriptions of compressible channel flow that still inform engineers today, innovative and wide-ranging analyses of secondary flows in turbomachinery that defined the field, and creation of some of the first notes on gas turbine cycle analysis. A theme in the many areas of engineering in which he had impact was the satisfaction from the growth of understanding that can accompany making things work—in his words, ‘machines produce ideas just as surely as ideas produce machines’. A Cambridge graduate, he was a professor at MIT when, in 1951, he was recruited to a newly established chair at Cambridge, where he later had leadership roles as head of the engineering department (1968–73) and Master of Churchill College (1968–83). He retained strong ties to MIT, however, and fostered lasting collaborations between the two universities. Among his numerous awards and honours were the US Medal of Freedom (1947), a Royal Society Medal (1982) and a knighthood (1970) for ‘services to thermodynamics’, a citation that pleased him greatly.

Performance Improvement of Simple Gas Turbine Cycle with Vapor Compression Inlet Air Cooling

Gas turbine cycle power plants are being broadly utilized for power generation around the world. The change in temperature and humidity of ambient air substantially influences the plant performance due to naturally suctioned compressors in gas turbine installations. There appears the change in temperature from under 5 °C to more than 45 °C and humidity deviation from under 25% to over 85% in countries belonging to the hot and humid environment. Performance of GT cycle is a strong function of the ambient air temperature with its specific work output dropping by 0.5-0.9% for every 1°C increase in the temperature of air. Due to this reason, the power output falls off on hot days due to air density becoming smaller. Vapor compression cooling is one of the possibilities for sustaining the temperature of admitting air in the required limits. Present paper deals with thermodynamic analysis of gas turbine cycle and investigate the impact inlet air cooling on the GT cycle performance using vapor compression inlet air cooling.

A Lumped Thermodynamic Model of Gas Turbine Blade Cooling: Prediction of First-Stage Blades Temperature and Cooling Flow Rates

Turbine inlet temperatures (TIT) of 1500–2000 K have become a sort of standard for most modern advanced applications. First-stage blades are obviously the most exposed components to such hot gases, and thus they need proper cooling. In the preliminary design of the blades and their cooling system, designers must rely on simple models that can be further refined at a later stage, in order to have an approximate but valuable set of guidelines and to reach a feasible first-order configuration. In this paper, a simple lumped thermodynamic model of blade cooling is proposed. It is based on mass/energy balances and heat transfer correlations, and it predicts a one-dimensional temperature profile on the blade external surface along the chord for a given gas temperature profile, as well as the required cooling air flow rates to prevent blade material from creep. The greatest advantage of the model is that it can be easily adapted to any operating condition, process parameter, and blade geometry, which makes it well suited to the last technological trends, namely, the investigation of new cooling methods and alternative coolants instead of air. Therefore, the proposed model is expected to be a useful tool in the field of innovative gas turbine cycle analysis, replacing more computationally intensive and very time-consuming models.

Energy and exergy analysis of air-film cooled gas turbine cycle: Effect of radiative heat transfer on blade coolant requirement

Gas turbine blade cooling is critical to continuous reliable operation of gas turbines. Literature suggests that air-film cooling is one of the most widely used blade cooling techniques. This paper compares previously developed blade cooling models which are relevant to film cooling technique and it also proposes a gas turbine blade cooling model for the estimation of blade coolant mass fraction, considering radiative heat transfer from hot combustion gases to gas turbine blade surface. The proposed model gives an enhanced coolant mass fraction (≈5–6% over a wide range of TIT) as compared to previously developed models while analyzing gas turbine cycle. Gas turbine cycle performance has been evaluated based on two blade cooling models to compare blade coolant flow mass fraction, gas turbine plant specific work which are function of both compressor-pressure ratio and turbine inlet temperature. Both the blade cooling models closely follow each other with radiative cooling model. For the proposed blade cooling model, gas turbine specific work is around 417.39 kJ/kg (rpc = 22 and TIT = 1650 K) and gas turbine thermal cycle efficiency has been found to be 41.25% at (rpc = 22 and TIT = 1550 K). Exergy analysis of gas turbine cycle has also been done which shows combustor to be main source of exergy destruction (≈29%).

Thermodynamic modeling and Exergy Analysis of Gas Turbine Cycle for Different Boundary conditions

In this study an exergy analysis of 88.71 MW 13D2 gas turbine (GT) topping cycle is carried out. Exergy analysis based on second law was applied to the gas cycle and individual components through a modeling approach. The analysis shows that the highest exergy destruction occurs in the combustion chamber (CC). In addition, the effects of the gas turbine load and performance variations with ambient temperature, compression ratio and turbine inlet temperature (TIT) are investigated to analyse the change in system behavior. The analysis shows that the gas turbine is significantly affected by the ambient temperature which leads to a decrease in power output. The results of the load variation of the gas turbine show that a reduction in gas turbine load results in a decrease in the exergy efficiency of the cycle as well as all the components. The compressor has the largest exergy efficiency of 92.84% compared to the other component of the GT and combustion chamber is the highest source of exergy destruction of 109.89 MW at 100 % load condition. With increase in ambient temperature both exergy destruction rate and exergy efficiency decreases.

Performance evaluation of reheat gas turbine cycles

The role of gas turbine power plants in electrical energy production has been considerably increased in the last two to three decades. Various methods have been proposed to improve the performance of gas turbine cycles. In this research, two methods, a reheat cycle (RC) and a cycle with a reheat and a heat exchanger (RHC), were investigated and compared with a simple cycle (SC). Today, to achieve a higher efficiency and capacity in gas turbines, higher turbine inlet temperatures (1300 °C and more) are used. Basically, application of such temperatures without turbine blade cooling is impossible. Therefore, analysis of gas turbine cycles without considering blade cooling in modelling will certainly not lead to a valid and correct result. The main objective of this paper is to study the performance of an RC and RHC under actual conditions. In this regard, all processes are treated as actual, and in particular a relatively simple and reliable approach is used to predict the amount of cooling air. It should be noted that there are many attempts being made to produce ceramic turbines, for which a much-reduced cooling requirement will be necessary. The results obtained on the basis of a model developed for this research show that reheating in the context of a realistic study may lead to an improvement both in efficiency and in specific net work.

Analytical Blade Row Cooling Model for Innovative Gas Turbine Cycle Evaluations Supported by Semi-Empirical Air-Cooled Blade Data

With the objective of performing reliable innovative gas turbine cycle calculations, a new procedure aimed at evaluating blade cooling performance is presented. This complete analytical (convective and film) blade cooling modeling provides the coolant mass flow and pressure loss estimation, and is a useful tool in the field of innovative gas turbine cycle analysis, mainly when alternative fluids are considered. In this case, in fact, the conventional semi-empirical data based on the use of air as traditional coolant and working media are no longer suitable. So the analytical approach represents a way of properly investigating alternative cooling methods and fluids. In the presented analysis the effects of internal blade geometry on cooling performance are summarized by the Z parameter, which also highly affects the coolant flow pressure losses. Since existing technology represents a natural starting point for the assessment of Z, the model is able to automatically estimate a proper value relying only on available semi-empirical data which were established for air-cooled gas turbine blades. When alternative fluids are considered, the same estimated value of Z is still maintained for the calculation, with the result of investigating the performance of existing blade technology for novel operational conditions. This represents an example of how the analytical approach, supported by conventional air-cooled blade semi-empirical data, appears as an innovative tool in the analysis of novel gas turbine cycles. In fact, the simulation results for the cooled blade were easily employed on the whole system level (gas turbine).

97/02192 Analysis of gas-turbine cycles with thermo-chemical conversion of the working medium. 2. External recovery of removed heat (combined cycles)

97/02192 Analysis of gas-turbine cycles with thermo-chemical conversion of the working medium. 2. External recovery of removed heat (combined cycles)

97/01389 Analysis of gas-turbine cycles with thermochemical conversion of the working medium. 2. External recovery of removed heat (combined cycles)

97/01389 Analysis of gas-turbine cycles with thermochemical conversion of the working medium. 2. External recovery of removed heat (combined cycles)

Computer-Aided Analysis of Gas Turbine Cycles

This paper describes a microcomputer-based, interactive, and menu-driven software package designed to help mechanical engineering students to understand gas turbines and to allow them to conduct more analysis of gas turbine cycles than they would normally be able to do by hand-calculation. The program deals with gas turbine cycle analysis so the acronym GTCA is used. GTCA is written in the Pascal computer language and runs on IBM PC, or compatible, computers. Improvements to the basic Brayton cycle, including three compressor and turbine stages, reheater, heat exchanger, intercooler, and precooler are incorporated into the program. The package is highly flexible and allows the user to model cycle schemes formed of any combination of these elements and to handle both shaft power turbines and aircraft turbojet and turbofan turbines. An important feature of the program is its ability to solve for any unknown variables. In addition to this, the program provides a schematic of the turbine plant layout and a temperature-entropy diagram of the cycle, and permits the plotting of the variation of any quantity versus any other quantity. This option enables the student to easily study and understand the effects of changing design variables on the overall performance of the cycle and permits its optimization. The statistical survey conducted along with the examples presented demonstrate the capabilities of the package as a teaching tool.

On the thermodynamics of dual purpose power desalting plants Part II. Using gas turbines

Recent advances in gas turbine cycles and combined gas/steam combined cycles are presented. First and second law analysis of gas turbine cycles is presented and shows that substantial available energy (up to 30% of fuel availability) is carried out by gas turbine exhaust gases. This available energy can be utilized for further heat to work conversion or for direct process heating. Heat recovered from gas turbine exhaust gases in heat recovery steam generator (HRSG) can generate relatively high pressure steam to be supplied to Rankine steam power cycle to form gas/steam power cycle of high efficiency (40–45%). Steam can be generated at low pressure in the HRSG for direct supply to the brine heater of a multistage flash MSF desalting system. Possible combination of simple gas turbine cycle or combined gas/steam cycle with reverse osmosis or MSF sea water desalting systems are presented and evaluated. The evaluation indicates that most of these combination are more superior than combination with steam power plants from energy view points.

Paper 5: A Cycle Analysis Technique for Small Gas Turbines

Aerothermodynamic analysis studies for open Brayton cycles are often conducted treating the component efficiencies as independent variables. However, as maximum output power is decreased and maximum cycle temperature increased, turbomachinery component sizes diminish resulting in lower component efficiencies. A meaningful small gas turbine cycle analysis should, therefore, treat the component efficiencies as dependent variables. A discussion of such a treatment, as employed during the cycle analysis phase of a small gas turbine, is presented. The particular aerodynamic configuration examined is one comprising a single-stage radial compressor and a single-stage radial turbine. Additionally, cycle performance charts for the selected configuration are presented indicating optimum cycle parameter combinations, attainable performance levels, and typical small gas turbine engine weights.