Higher turbine inlet temperatures (TIT) are required for higher overall efficiency of gas turbine engines. Due to the constant push towards achieving high TIT, the heat load on high pressure turbine components has been increasing with time. Gas turbine airfoils are equipped with several sophisticated cooling technologies which protect them from harsh external environment and increase their operating life and reduce the maintenance cost. The turbine airfoils are coated with thermal barrier coatings (TBCs) and the external surface is protected by film cooling. The internals of gas turbine blades are cooled by relatively colder air bled off from the compressor discharge. Gas turbine internals can be divided into three broad segments – Leading edge section, (2) mid-chord section and (3) trailing edge section. The leading edge of the airfoil is subjected to extreme heat loads due to hot main gas stagnation and high turbulence intensity of the combustor exit gases. The leading edge is typically cooled by jet impingement which cross-over the rib turbulators in the feed chamber. The mid-chord section of the turbine airfoils have serpentine passages connected via. 180° bends, and they feature turbulence promotors which enhance the heat exchange rates between the coolant and the internal walls of the airfoil. The trailing edge section is typically cooled by array of pin fins. On one hand, the coolant routed through the internal passages of turbine airfoil help maintain the airfoil temperatures within safe limits of operation, the cooled air comes at a cost of loss of high pressure air from the compressor section. The aim of this study is to develop internal cooling concepts which have high thermal hydraulic performance, i.e. to gain high levels heat transfer enhancement due to cooling concepts at lower pumping power requirements. Experimental and numerical studies have been carried out and new rib turbulator designs such as Criss-Cross pattern, compound channels featuring uniquely organized ribs and dimples, novel jet impingement hole shapes have been developed which have high thermal-hydraulic performance. Further, gas turbine blades rotate at high rotational speeds. The internal flow routed thought the serpentine passages are subjected to Coriolis and centrifugal buoyancy forces. The combined effects of these forces results in enhancement and reduction in heat transfer on the pressure side and suction side internal walls. This leads to non-uniformity in the heat transfer enhancement which leads to non-uniform cooling and increase in the sites of high and low internal wall temperatures. Development of cooling concepts which have high thermal hydraulic performance under non-rotating conditions is important, however, under rotation, the heat transfer characteristics of the internal passages is significantly different in an unfavorable way. So the aim of the turbine cooling research is to have concepts which provide highly efficient and uniform cooling. The negative effects of rotation has been addressed in this study and new orientation of two-pass cooling channels has been presented which utilizes the rotational energy in favor of heat transfer enhancement on both pressure and suction side internal walls. Present study has led to several new cooling concepts which are efficient under both stationary and rotating conditions. / Ph. D. / Higher turbine inlet temperatures lead to higher overall efficiency of gas turbines. Hence, the high pressure stages of turbine sections, which are downstream of the combustor section, have significant thermal load. The turbine inlet temperatures can be as high as 1700°C and turbine airfoil material melting point temperature is around 1000°C. In order to protect the blade for the harsh environment, relatively colder air (~700°C) bled off from the compressor discharge is routed through the internal cooling passages of turbine airfoils. The coolant bled from the compressor section contributes the reduction in the performance of the engine. Hence, the aim of the turbine cooling research is to achieve high rates of heat transfer at relatively lower pumping power requirements. In order to enhance the heat transfer rates from between the hot internal walls of airfoil and the coolant, turbulence promotors are typically installed in the mid-section of the airfoil which features serpentine passages interconnected by 180° bends. Present study is focused on development of highly efficient concepts for internal flows in turbine airfoils. The other aspect of internal cooling research is focused on characterization of heat transfer under rotating conditions. Coriolis force and centrifugal buoyancy forces lead to non-uniform cooling and the heat transfer rates are significantly different under rotating conditions compared to non-rotating conditions. Present study utilizes detailed measurements of heat transfer coefficients under rotating conditions for the development of cooling designs for two-pass ribbed channels where rotational effects can be used in favor of heat transfer enhancement, leading to enhanced and more uniform cooling of internal walls.

This thesis investigates novel methodologies for modelling, simulation and control of gas turbines using ANNs. In the field of modelling and simulation, two different types of gas turbines are modelled and simulated using both Simulink and neural network based models. Simulated and operational data sets are employed to demonstrate the capability of neural networks in capturing complex nonlinear dynamics of gas turbines. For ANN-based modelling, the application of both static (MLP) and dynamic (NARX) networks are explored. Simulink and NARX models are set up to explore both steady-state and transient behaviours. To develop an offline ANN-based system identification methodology for a low-power gas turbine, comprehensive computer program code including 18720 different ANN structures is generated and run in MATLAB to create and train different ANN models with feedforward multi-layer perceptron (MLP) structure. The results demonstrate that the ANN-based method can be applied accurately and reliably for the system identification of gas turbines. In this study, Simulink and NARX models are created and validated using experimental data sets to explore transient behaviour of a heavy-duty industrial power plant gas turbine (IPGT). The results show that both Simulink and NARX models successfully capture dynamics of the system. However, NARX approach can model gas turbine behaviour with a higher accuracy compared to Simulink approach. Besides, a separate complex model of the start-up operation of the same IPGT is built and verified by using NARX models. The models are set up and verified on the basis of measured time-series data sets. It is observed that NARX models have the potential to simulate start-up operation and to predict dynamic behaviour of gas turbines. In the area of control system design, a conventional proportional-integral-derivative (PID) controller and neural network based controllers consisting of ANN-based model predictive (MPC) and feedback linearization (NARMA-L2) controllers are designed and employed to control rotational speed of a gas turbine. The related parameters for all controllers are tuned and set up according to the requirements of the controllers design. It is demonstrated that neural network based controllers (in this case NARMA-L2) can perform even better than conventional controllers. The settling time, rise time and maximum overshoot for the response of NARMA-L2 is less than the corresponding factors for the conventional PID controller. It also follows the input changes more accurately than the PID. Overall, it is concluded from this thesis that in spite of all the controversial issues regarding using artificial neural networks for industrial applications, they have a high and strong potential to be considered as a reliable alternative to the conventional modelling, simulation and control methodologies. The models developed in this thesis can be used offline for design and manufacturing purposes or online on sites for condition monitoring, fault detection and trouble shooting of gas turbines.

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<p>The world we are living in today is pushing the technology harder and harder. The products need to get better and today they also need to be friendlier to the environment. To get better products we need better analysis tools to optimize them and to get closer to the limit what the material can withstand. Siemens industrial Turbomachinery AB, at which thesis work is made, is constructing gas and steam turbines. Gas and steam turbines are important in producing power and electricity. Electricity is our most important invention we have and most of the people are just taking electricity for granted. One way to produce electricity is to use a gas turbine which is connected to a generator and by combing the turbine with a steam turbine the efficiency can be up to 60 %. That is not good enough and everybody want to get better efficiency for the turbines, meaning less fuel consumption and less impact on the environment.</p><p>The purpose of this thesis work is to analyze a tool for rotor dynamics calculations. Rotor dynamics is important in designing a gas turbine rotor because bad dynamics can easily lead to disaster. Ansys Classic version 11 is the analyze program that is going to be evaluated for the rotor dynamic applications. Nowadays rotor dynamics is done with beam elements i.e. 1D models, but in this thesis work the beam elementsare going to be changed to solid elements. With solid elements a 3D model can be built and thanks to that more complex calculations and simulations can be made. For example, with a 3D model 3D effects can be shown and e.g. simulations with blade loss can be done. 3D effects are not any problem today but in the future the gas turbines have to get better and maybe also the rotational speed will increase.</p><p>Ansys isn’t working perfectly yet, there are some problems. However Ansys have a good potential to be an additional tool for calculations of rotor dynamics, because more complex calculations and simulations can be done. More knowledge and time needs to form the rules to modeled a rotor and developing the analysis methods. Today the calculated lateral critical speeds are lower than the ones obtained from the in-house program Ardas version 2.9.3 which is used in Siemens Industrial Turbomachinery AB today. The difference between the programs are not so big for the four first lateral modes, only 3-8 %, but the next three lateral modes have a difference of 10-20 %. The torsion frequencies from Ansys are the same as the ones from Ardas, when the Solid186 elements are used to model the blades.</p>

It takes 3~5 years to finish a power plaint project including location, reliability, environment evaluating, investigation, etc. In addition, it is difficulty to get a right place and hinder by the environment protection. So, it is an important class on boosting the existing power generation capacity. It was used to enhance power generation capacity by increasing the combustion chamber temperature in traditional way. However, it not only increases the exhaust temperature of gas turbine, but also increase the compressor ration. However, it is more difficulty on the design of gas turbine. And then we consider the other way in this thesis by reducing inlet air temperature of compressor to increase the density and flow of air and the power generation capacity. The result is magic that the power generation capacity enhance 10% ~20%. The analysis of Combustion Turbine Inlet Air Cooling System by Absorption refrigerant system(CTIAC-ABS) describe in chapter 2 including fundamental of a gas turbine, the absorption refrigerant chiller, the inlet cooling coil and cogeneration system. It lets us know how to select the style of cogeneration and specification of an absorption refrigerant chiller. It is important to consider the mass condensate water in the air side of inlet cooling coil. The author suggest to use the analysis method of wet-coil developed by Threlkeld(1970). The CTIAC system could be used to the Gas Turbine System, Gas Turbine with HRSG System and Combined System. Because of there is not high pressure steam, we can use the fired-gas absorption refrigerant system as the source of chiller on the CTIAC-ABS system. There is the high pressure steam of Gas Turbine with HRSG System and Combined System. So we can divided the high pressure steam into two part, one to process and the other could be used as the heat source of absorption refrigerant chiller There are two advantages of using CTIAC-ABS on cogeneration power plaint. 1.The new purpose of mass high pressure steam could be used in cogeneration power plaint in Taiwan. 2.Reduction operational cost of CTIAC-ABS The author finished the sensibility of power generation capacity with the analysis of practical operative data, classification of gas turbine and the power plaint Simulation program (GateCycle). When the compressor inlet temperature decrease from 30OC to 10OC, the results are : air flow rate increase 6.3%, fuel flow rate increase 5.95%, exhaust air temperature decrease 1.7% and exhaust air flow rate increase 6.3%, net power output increase 12.2%, heat rat decrease 3.7% and thermal efficiency upward 1.32%.Then, the author got a simulative equation of power capacity. The typical gas turbines operate at full-load condition, 52.25% of annual hours, in 1998 in Taiwan. Gas turbines were almost full load on daytime and half-load or closed at night. If we apply the CTIAC-ABS system on TPC's combined power plant, it can operate at 8:00~18:00 on daytime and shutdown at night. If there is high pressure steam in the cogeneration with HRSG, the CTIAC-ABS system can operate at the time that the cogeneration power plant is operative. How to decide the capacity of absorption refrigerant chiller? The author decided the maximum capacity of absorption refrigerant chiller operating at 31OC , 80%RH of weather condition that limit by 2.5% ***. The author forecasts the lowest compressor inlet air temperature will be 10OC. The steam double-effect CTIAC-ABS system could make the compressor inlet air temperature decrease from 30OC to 10 OC and enhances the heat rate 3.8%, the thermal efficiency 1.2%. The fired-direct CTIAC-ABS system also enhances the heat rate 5% and the thermal efficiency 1.5%. The results are close to the simulation of GateCycle program. So, the author compared the result of simulation with real data that the optimumal operative point of the CTIAC-ABS system is 10OC.

A computational study of three-dimensional turbulent flow and heat transfer was performed in four types of rotating channels. The first type is a rotating rectangular channel with V-shaped ribs. The channel aspect ratio (AR) is 4:1, the rib height-to-hydraulic diameter ratio (e/Dh) is 0.078 and the rib pitch-to-height ratio (P/e) is 10. The rotation number and inlet coolant-to-wall density ratio were varied from 0.0 to 0.28 and from 0.122 to 0.40, respectively, while the Reynolds number was varied from 10,000 to 500,000. Three channel orientations (90 degrees, -135 degrees, and 135 degrees from the rotation direction) were also investigated. The second type is a rotating rectangular channel with staggered arrays of pinfins. The channel aspect ratio (AR) is 4:1, the pin length-to-diameter ratio is 2.0, and the pin spacing-to-diameter ratio is 2.0 in both the stream-wise and span-wise directions. The rotation number and inlet coolant-to-wall density ratio varied from 0.0 to 0.28 and from 0.122 to 0.20, respectively, while the Reynolds number varied from 10,000 to 100,000. For the rotating cases, the rectangular channel was oriented at 150 degrees with respect to the plane of rotation. In the rotating two-pass rectangular channel with 45-degree rib turbulators, three channels with different aspect ratios (AR=1:1; AR=1:2; AR=1:4) were investigated. Detailed predictions of mean velocity, mean temperature, and Nusselt number for two Reynolds numbers (Re=10,000 and Re=100,000) were carried out. The rib height is fixed as constant and the rib-pitch-to-height ratio (P/e) is 10, but the rib height-to-hydraulic diameter ratios (e/Dh) are 0.125, 0.094, and 0.078, for AR=1:1, AR=1:2, and AR=1:4 channels, respectively. The channel orientations are set as 90 degrees, the rotation number and inlet coolant-to-wall density ratio varied from 0.0 to 0.28 and from 0.13 to 0.40, respectively. The last type is the rotating two-pass smooth channel with three aspect ratios (AR=1:1; AR=1:2; AR=1:4). Detailed predictions of mean velocity, mean temperature and Nusselt number for two Reynolds numbers (Re=10,000 and Re=100,000) were carried out. The rotation number and inlet coolant-to-wall density ratio varied from 0.0 to 0.28 and from 0.13 to 0.40, respectively. A multi-block Reynolds-averaged Navier-Stokes (RANS) method was employed in conjunction with a near-wall second-moment turbulence closure.

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A two-dimensional numerical model for compressible branching flow through a slot is described for the purpose of predicting the discharge coefficients of film cooling holes in gas turbine blades. The method employs free-streamline theory and the hodograph transformation. It calculates the area ratio of hole to duct and the contraction coefficient from a set of prescribed boundary conditions. An approximate method for calculating the compressible contraction coefficients is also discussed in the thesis. It employs the incompressible theory previously developed by McNown and Hsu (1951) for the free efflux, the 'compressibility factor' and the flow parameter (P_o-P_j)/(P_o-P₁), where P_o, P_j, P₁ represent the stagnation pressure, the static pressure of the jet and the static pressure of the approach flow, respectively. The advantages of using this method are the direct input of the area ratio of hole to duct and its speed of calculation. Experimental tests were performed using a specially designed rig in a supersonic wind tunnel. The investigations included sharp-edged slots with three different widths, a single hole and a row of two holes. The approach velocity in terms of the characteristic Mach number ranged from 0.18 to 0.58 and the pressure ratio P_o/P_j, ranged from 1.10 to 1.97. Agreement between the experimental data and the theoretical values was good to within the experimental accuracy (typically around +/- 5%) for the slots and the 2-hole configuration. For the 1-hole configuration, less bleed flow than predicted was observed, with the discrepancy varying from 7% to 18%. The latter case is a very severe test of a purely two-dimensional theory. The results for the 2-hole plate suggest that the slot theory can in fact be used to predict the flow through a row of holes with small pitch to diameter ratios.