T. Chmielniak

Parametric analysis of a dual fuel parallel coupled combined cycle

In this paper an optimal interconnection of a coal steam plant with a gas combined cycle is analyzed. In the first part the model of such a connection is introduced in order to calculate the integral and marginal cycle efficiency. A parametric analysis is then performed on the hypothetical plant structure. The main goal of the analysis was to estimate the influence of some parameters on the considered cycle efficiency.

Technical and Economic Analysis of the Gas Turbine Air Bottoming Cycle

The gas turbine engine has many advantages such as low investment costs, low emissions and a low water consumption. This fact allows its application in many power engineering systems, for example as parts of gas and oil transport systems. It is possible to increase the efficiency of gas turbines through the use of combined cycles. For this purpose, the steam cycle is used most frequently. These systems are highly efficient in terms of energy, but they are very complex and have a high water consumption. An alternative to steam cycles are gas-air systems, referred to as the ABC’s (Air Bottoming Cycles), which use hot combustion gases as a heat source for the air cycle. ABC’s are composed of a gas turbine powered by natural gas, an air compressor and an air turbine coupled to the system by means of a heat exchanger, referred to as the AHX (Air Heat Exchanger).The paper presents an application of gas-air systems with example configurations, together with thermodynamic characteristics. Two technological structures are taken into consideration — a simple system of the ABC and an ABC with air intercooling. A parametric analysis of these systems is performed using a special computer program with real gas properties for enthalpy and entropy calculations. A basic comparative analysis of gas turbine air bottoming cycle and combined gas-steam cycle has been also done. Other important calculations are related to the heat exchanger, which is one of the most important components in this system because it couples the gas and air parts. The efficiency of the whole cycle depends on a rationally designed heat exchanger. The calculations are performed for a shell-and-tube exchanger, as well as for a plate heat exchanger. For all investigations an purchase cost of machines and devices is also determined.Copyright

Analysis of cycle configurations for the modernization of combined heat and power plant by fitting a gas turbine system

The application of a gas turbine generally allows to increase the number of possible configurations of cogenerated heat and electrical power systems, which became a significant substitute for classic, coal-fired power plants. They are characterized by better thermodynamical, economical, ecological, and operating indexes. Gas turbine units are also the best option for the modernization of existing power plants. This paper discusses the effectiveness of various technological configurations with gas turbines, which are to be applied during modernization projects of already existing conventional combined heat and power plants. In the analysis enthalpy and entropy methods were applied. Algorithms of the entropy method allow to determine the entropy generation in each section of a combined heat and power (CHP) plant. Several criteria were taken into consideration while analyzing the effectiveness of technological cycle configurations with gas turbines. These include the energy effectiveness, the efficiency of the HRSG and the steam cycle, the efficiency of the whole thermal electric power station, the exergetic efficiency of the HRSG and the steam cycle, and the fuel efficiency index. It was assumed that gas turbines operate under their nominal conditions. The composite curves were also taken into consideration while choosing the type of the turbine. The modernization project tends not to eliminate those existing power plant sections (machines and equipment), which are able to operate further. The project suggests that those units should remain in the system, which satisfy the applied durability criterion. The last phase of the optimization project focuses on the sensibility verification of several steam-gas CHP plant parameters and their influence on the whole system.

Optimization of Cooling Passages Within a Turbine Vane

The trends in gas turbine technology aim to build more and more efficient cycles, which is usually achieved by the temperature increase at the inlet of the turbine. To prevent the negative effects of elevated temperature some actions are taken concerning, among others cooling of the high temperature components. Since the structure of the cooling system affects the turbine performance, it is essential to carry out the optimization to make it as efficient as possible. In this paper we show some aspects of passage optimization for internally cooled gas turbine vanes. In the present study the vane profile is taken as aerodynamically optimal. The analysis involves the optimization of the location and size of circular cooling passages within the vane. The analysis is performed by means of the genetic algorithm for the optimization task and FEM for the heat transfer predictions within the blade.Copyright

Expansion Line Modeling and Strength Diagnostics of Internally Cooled Gas Turbines

This paper regards control and optimization of a gas turbine operation with a respect to effectiveness and reliability criteria. The development of diagnostics procedures begins with modeling of the gas expansion line for various loads with regard to an internal blade cooling. Analyzing an expansion line allows to assess the influence of cooling parameters on gas path and turbine operation. Computational models are described here, which respect various cooling aspects, mainly convection and film cooling. Several examples of gas path, blade temperature and thermal barrier coating (TBC) temperature dependencies on cooling parameters are presented. The determination of gas and metal temperatures is utilized to evaluate creep wear rate. The dependency between the strength and durability of turbine components and their temperature might be regarded in several aspects. Firstly: lower temperature decreases the creep rate. Even small temperature drop leads to a significant deceleration of creep processes. Secondly: the change of the temperatures modifies also the distribution of thermal stresses. This change of thermal stresses is usually very small and might be neglected. Presented analysis omits the influence of temperatures alteration of stresses distribution, it regards however the change of the creep characteristics.Copyright

Analysis of the Biomass Integrated Combined Cycles With Two Different Structures of Gas Turbines

Biomass integrated gasification combined cycles (BIGCC) are an interesting solution for electricity production. In relation to other biomass conversion technologies, BIGCC is characterized by relative high energy efficiency. For the sake of high complexity of such systems, one of crucial tasks is evaluation and comparison of the different technological structures of BIGCC. The article shows models and results of simulations of gas steam cycles integrated with biomass gasification. All models and simulations are preformed with Aspen Plus computer program. In the paper the main comparison is made between systems with simple gas turbine and gas turbine with regeneration. Simple gas turbine model based on LM2500 gas turbine parameters, Mercury 50 gas turbine parameters are used for model of gas turbine with regeneration. The model of gas generator consists of two equilibrium reactors. The use of two reactors led to more precise simulations of the flue gas composition, than the model with one reactor. Systems used for study include low-temperature gas cleaning system. Steam cycle consists of 1-pressure heat recovery steam generator (HRSG) and a condensing steam turbine. The main results of the work are: comparison of energy efficiency between system with gas turbine with regeneration and simple gas turbine, sensitive analysis of the impact of pressure in HRSG on energy efficiency, comparison of energy efficiency and heat and mass streams for different configurations of heat exchangers.Copyright

Technical and Economic Analysis of Biomass Integrated Gasification Combined Cycle

Biomass integrated gasification combined cycles (BIGCC) are an interesting solution for electricity production. In relation to other biomass conversion technologies, BIGCC is characterized by relatively high energy efficiency. This article presents models and results of simulations of the gas steam cycles integrated with pressurized gasification using biomass as a feedstock. The model and simulations are preformed with Aspen Plus® computer program. The gas generator model consists of two equilibrium reactors. The use of two reactors led to more precise simulations of the flue gas composition, than the model with one reactor. The systems used for study include high-temperature gas cleaning system and a simple gas turbine. The steam cycle consists of 1-pressure heat recovery steam generator (HRSG) and a condensing steam turbine. The main results of the work are: comparison of energy efficiency for a system with different pressure ratio in a gas turbine, sensitive analysis of the impact of steam temperature and pressure in HRSG on energy efficiency. The economic analysis includes determination of the electricity price in Polish economic conditions.Copyright

Coupled Analysis of Cooled Gas Turbine Blades

The paper presents solution aspects of the heat transfer modeling and fluid flow prediction of the convective cooled gas turbine blade. The heat transfer problem within the blade material is solved using finite element method whereas the flow problem employs the finite volume method. The flow field is calculated by solving the Navier-Stokes (NS) equations. The problem can be faced in two ways which are presented in this work. The first one is the uncoupled field method which does not take into consideration the interaction between the flowing medium and the blade. This way of solution is simpler and computationally cheap but has limited accuracy. The other one is the coupled field method (conjugate heat transfer CHT), which resolves iteratively the thermal interaction between the fluid and the blade material. The coupled method is much more accurate but one has to pay for it with longer computations as well as the algorithm stability control. As the fluid flow schemes are very sensitive to boundary condition changes, a fine time stepping with relaxation as well as an adequate mesh were required. The calculations showed another very important problem occurring in the analyses carried out. This is the laminar-turbulent transition which can significantly affect the accuracy of the results. The change of the flow character influences the heat exchange intensity and consequently the temperature distribution within the blade. Nevertheless, the problem is not yet satisfactorily worked out and the criteria of the laminar-turbulent transition are very difficult to build. The problem becomes simpler if the location of the transition point is known (i.e. from experimental data). On the basis of experimental data authors solved the problem of a blade cooling for both uncoupled and coupled method and different flow characters in order to obtain numerical results best matching the real phenomena.Copyright

Analysis of Thermal and Stress States in Transient Operation of a Turbine Co-operating with Twinboiler

ABSTRACT The operating conditions of coal-fired power units are changing because of the current shift in the approach to technologies based on fossil fuels. Due to decarbonization issues, their function is now more often to balance shortages of electricity generated from renewable sources. A substantial rise can be observed nowadays in the significance of the capability of all the installation modules to operate under variable loads. One of the solutions improving the coal-fired power unit flexibility is the twin-boiler concept based on using a system with twin-boilers co-operating with one steam turbine. Such a solution makes it possible to obtain characteristics similar to gas-steam systems and achieve low values of the minimum load on the basic fuel. The solution operating characteristics cannot be determined fully unless issues related to the thermal and stress states of individual elements are discussed first. The subject of the numerical analyses presented in this paper are thermal and stress states arising in the elements of a turbine co-operating with 2 boilers during steady- and unsteady-state operation. Results of numerical simulation of the turbine steady operation, the start-up process and power change are presented. An analysis is conducted of the impact of the rate of changes in power on the level of stresses in the turbine elements and in consequence on the fatigue of the turbine rotors.

Comparative analysis of energy potential of three ways of configuration of a condenser power plant thermal cycle

Comparative analysis of energy potential of three ways of configuration of a condenser power plant thermal cycle A theoretical, comparative analysis of three configuration ways of a condenser power plant thermal cycle is shown in the work. A new regeneration & separation preheater and its application in a thermal cycle is presented. Results obtained allow to compare all three analysed configurations efficiencies.