Progress in Gas Turbine Performance Edited by Ernesto Benini PROGRESS IN GAS TURBINE PERFORMANCE Edited by Ernesto Benini Progress in Gas Turbine Performance http://dx.doi.org/10.5772/2797 Edited by Ernesto Benini Contributors Abdullah Cahit Karaoglanli, Ismail Ozdemir, Kazuhiro Ogawa, Ahmet Türk, Konstantinos G. Kyprianidis, Andrew Rolt, Vishal Sethi, Mostafa Khosravyelhossani, Ene C. Barbu, Romulus Petcu, Valeriu Vilag, Valentin Silivestru, Tudor Prisecaru, Jeni Alina Popescu, Cleopatra Cuciumita, Sorin Tomescu, Marco Antonio Rosa Nascimento, Eraldo Cruz Dos Santos, Lucilene De Oliveira Rodrigues, Fagner Luis Goulart Dias, Elkin Iván Gutiérrez Velásquez, Rubén Alexis Miranda Carrillo, Gennady Kulikov, Valentin Arkov, Ansaf Abdulnagimov, Jan Zanger, Thomas Monz, Manfred Aigner, Takeharu Hasegawa, Anastassios Stamatis, Ioannis K Templalexis © The Editor(s) and the Author(s) 2013 The moral rights of the and the author(s) have been asserted. 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More details and guidelines concerning content reuse and adaptation can be foundat http://www.intechopen.com/copyright-policy.html. Notice Statements and opinions expressed in the chapters are these of the individual contributors and not necessarily those of the editors or publisher. No responsibility is accepted for the accuracy of information contained in the published chapters. The publisher assumes no responsibility for any damage or injury to persons or property arising out of the use of any materials, instructions, methods or ideas contained in the book. First published in Croatia, 2013 by INTECH d.o.o. eBook (PDF) Published by IN TECH d.o.o. Place and year of publication of eBook (PDF): Rijeka, 2019. IntechOpen is the global imprint of IN TECH d.o.o. Printed in Croatia Legal deposit, Croatia: National and University Library in Zagreb Additional hard and PDF copies can be obtained from orders@intechopen.com Progress in Gas Turbine Performance Edited by Ernesto Benini p. cm. ISBN 978-953-51-1166-5 eBook (PDF) ISBN 978-953-51-6353-4 Selection of our books indexed in the Book Citation Index in Web of Science™ Core Collection (BKCI) Interested in publishing with us? Contact book.department@intechopen.com Numbers displayed above are based on latest data collected. For more information visit www.intechopen.com 4,100+ Open access books available 151 Countries delivered to 12.2% Contributors from top 500 universities Our authors are among the Top 1% most cited scientists 116,000+ International authors and editors 120M+ Downloads We are IntechOpen, the world’s leading publisher of Open Access books Built by scientists, for scientists Meet the editor Dr. Ernesto Benini is currently Associate Professor of Flu- id Machinery at the Department of Industrial Engineer- ing, University of Padova, Italy, where he first obtained the MSc in Mechanical Engineering and then the PhD in Energy Technology. His research experience is mainly focused on gas turbine engine design and optimization, with particular emphasis on aero-thermodynamics of tur- bomachinery. He authored more than 200 research articles on these topics, the largest part on international refereed journals and congresses. Contents Preface X I Section 1 Gas Turbine and Component Performance 1 Chapter 1 On Intercooled Turbofan Engines 3 Konstantinos G. Kyprianidis, Andrew M. Rolt and Vishal Sethi Chapter 2 Development of Semiclosed Cycle Gas Turbine for Oxy-Fuel IGCC Power Generation with CO2 Capture 25 Takeharu Hasegawa Chapter 3 Synthesis of Flow Simulation Methods for Fast and Accurate Gas Turbine Engine Performance Estimation 51 Ioannis Templalexis Chapter 4 Gas Turbine Cogeneration Groups Flexibility to Classical and Alternative Gaseous Fuels Combustion 79 Ene Barbu, Romulus Petcu, Valeriu Vilag, Valentin Silivestru, Tudor Prisecaru, Jeni Popescu, Cleopatra Cuciumita and Sorin Tomescu Chapter 5 Micro Gas Turbine Engine: A Review 107 Marco Antônio Rosa do Nascimento, Lucilene de Oliveira Rodrigues, Eraldo Cruz dos Santos, Eli Eber Batista Gomes, Fagner Luis Goulart Dias, Elkin Iván Gutiérrez Velásques and Rubén Alexis Miranda Carrillo Section 2 Gas Turbine Combustion 143 Chapter 6 Review of the New Combustion Technologies in Modern Gas Turbines 145 M. Khosravy el_Hossaini Chapter 7 Experimental Investigation of the Influence of Combustor Cooling on the Characteristics of a FLOX©-Based Micro Gas Turbine Combustor 165 Jan Zanger, Monz Thomas and Aigner Manfred Section 3 Fault Detection in Systems and Materials 185 Chapter 8 Engine Condition Monitoring and Diagnostics 187 Anastassios G. Stamatis Chapter 9 System Safety of Gas Turbines: Hierarchical Fuzzy Markov Modelling 213 G. G. Kulikov, V. Yu. Arkov and A.I. Abdulnagimov Chapter 10 Thermal Shock and Cycling Behavior of Thermal Barrier Coatings (TBCs) Used in Gas Turbines 237 Abdullah Cahit Karaoglanli, Kazuhiro Ogawa, Ahmet Türk and Ismail Ozdemir X Contents Preface Recently, a remarkable difference in the research and development regarding gas turbine technology for transportation (mainly aeronautics) and power generation (essentially elec‐ tricity production) has been registered. The former remains substantially florid and unaltered with respect to the past years, as the superiority of air-breathing engines compared to other technologies is by far immense. In this context, research is directed toward all aspects of the engine, from aero thermal design to intelligent operation, from combustion to materials technology. On the other hand, the world of gas turbines (GTs) for power generation is indeed character‐ ized by completely different scenarios in so far as new challenges are coming up within the latest energy trends, where both a reduction in the use of carbon fuels and the raising up of renewables are becoming more and more important factors. While being considered a key technology for base-load operations for many years, modern stationary gas turbines are in fact facing the challenge to balance electricity from variable renewables with the one from flexible conventional power plants. This means that, in the near-future energy mix, station‐ ary GTs are expected to maintain a key role, however from a different perspective due to the fast growing technology of renewables, which are inherently fluctuating and uncertain. This will most probably imply that GTs will be operated as load-following machines backing up renewable energy technologies, with the aim of maintaining a stable and efficient grid. It is likely that GTs will support the growth of renewable energy and will gradually enable a higher integration of electricity from variable renewables into the grid. Stationary gas turbines currently in use have been designed for full-load operations. In the next future, they will likely run at part-load. As in this mode GTs are less efficient and expe‐ rience an increased environmental impact due to increased emissions, research is needed to optimize the flexibility and efficiency of conventional gas turbine when operated at off-de‐ sign, thus ensuring that flexible and efficient backup will be available. The book intends in fact to provide an updated picture as well as a perspective view of some of the above mentioned issues that characterize GT technology in the two different applica‐ tions: aircraft propulsion and stationary power generation. Therefore, the target audience for it involves design, analyst, materials and maintenance engineers. Also manufacturers, researchers and scientists will benefit from the timely and accurate information provided in this volume. The book is organized into three main sections including 10 chapters overall: (i) Gas Turbine and Component Performance, (ii) Gas Turbine Combustion and (iii) Fault Detection in Sys‐ tems and Materials. The editor is indebted to all the valuable contributions included in this book from the vari‐ ous GT experts spread worldwide, as well as to InTech Open Access Publisher for giving me the opportunity to edit this volume and to support me constantly during its preparation. Prof. Ernesto Benini Department of Industrial Engineering University of Padova, Italy Preface VIII Section 1 Gas Turbine and Component Performance Chapter 1 On Intercooled Turbofan Engines Konstantinos G. Kyprianidis, Andrew M. Rolt and Vishal Sethi Additional information is available at the end of the chapter http://dx.doi.org/10.5772/54402 Provisional chapter On Intercooled Turbofan Engines Konstantinos G. Kyprianidis, Andrew M. Rolt and Vishal Sethi Additional information is available at the end of the chapter 10.5772/54402 1. Introduction Public awareness and political concern over the environmental impact of the growth in civil aviation over the past 30 years have intensified industry efforts to address CO 2 emissions [5]. CO 2 emissions are directly proportional to aircraft fuel burn and one way to minimise the latter is by having engines with reduced Specific Fuel Consumption (SFC) and installations that minimise nacelle drag and weight. Significant factors affecting SFC are propulsive efficiency and thermal efficiency. Propulsive efficiency has been improved by designing turbofan engines with bigger fans to give lower specific thrust (net thrust divided by fan inlet mass flow) until increased engine weight and nacelle drag have started to outweigh the benefits. Thermal efficiency has been improved mainly by increasing the Overall Pressure Ratio (OPR) and Turbine Entry Temperature (TET) to the extent possible with new materials and design technologies. Mission fuel burn benefits from reducing specific thrust are illustrated in Fig. 1 (for a year 2020 entry into service, but otherwise conventional, direct drive fan engine for long range applications). The engine Take-Off (TO) thrust at Sea Level Static International Standard Atmosphere (SLS ISA) conditions is 293.6kN (66000lbf) and all Fan Pressure Ratio (FPR) and ByPass Ratio (BPR) values quoted are at mid-cruise conditions. The figure shows that only a modest reduction in block fuel is obtained by increasing the already large fan diameter. Reduced powerplant weight and/or nacelle drag would be needed before lower specific thrust would be justified, and one way of doing this would be to discard the nacelle and fit an open rotor in place of the fan. An alternative design approach to improving SFC is to consider an increased OPR intercooled core performance cycle. The thermal efficiency benefits from intercooling have been well documented in the literature - see for example [2, 3, 7, 9, 11–13, 15]. Very little information is available however, with respect to design space exploration and optimisation for minimum block fuel at aircraft system level. ©2012 Kyprianidis et al., licensee InTech. This is an open access chapter distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. © 2013 Kyprianidis et al.; licensee InTech. This is an open access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. © 2013 Kyprianidis et al.; licensee InTech. This is a paper distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. 2 Gas Turbine Figure 1. Block fuel benefits from reducing specific thrust for a year 2020 entry into service conventional turbofan engine for long range applications. Previously, a comparative study was presented focusing on a conventional core and an intercooled core turbofan engine for long range applications [5, 7]. Both configurations had the same fan diameter and were designed to meet the same thrust requirements. They were Ultra-High Bypass Ratio (UHBR) designs based on a three-shaft layout with a direct drive front fan. The intercooled core configuration (illustrated in Fig. 2) featured an intercooler mounted inboard of the bypass duct. The installation standard included a flow splitter and an auxiliary variable geometry nozzle. The two concepts were evaluated based on their potential to reduce CO 2 emissions (and hence block fuel) through both thermal and propulsive efficiency improvements, for engine designs to enter service between 2020 and 2025. Although fuel optimal designs were proposed, only limited attention was given to the effect of design constraints, material technology and customer requirements on optimal concept selection. A study is presented here that focuses on the re-optimization of those same powerplants by allowing the specific thrust (and hence the propulsive efficiency) to vary. Rather than setting fixed thrust requirements, a rubberised-wing aircraft model was fully utilised instead. The engine/aircraft combination was optimized to meet a particular set of customer requirements i.e. payload-range, take-off distance, time to height and time between overhaul. It was envisaged that different conclusions would be drawn when comparing the two powerplants at their optimal specific thrust and absolute thrust levels. It is shown through this study that performing a comparison at each concept’s optimal specific thrust level gives a different picture on intercooling. Differences in the optimal specific thrust levels between the two configurations are discussed. The design space around the proposed fuel-optimal designs was explored in detail and significant conclusions are drawn. Progress in Gas Turbine Performance 4 On Intercooled Turbofan Engines 3 10.5772/54402 Figure 2. Artistic impression of the intercooled core turbofan engine [10]. Figure 3. Conceptual design tool algorithm [4]. On Intercooled Turbofan Engines http://dx.doi.org/10.5772/54402 5 4 Gas Turbine Lower bound Upper bound FAR take-off distance - 2.5 [km] Climb to 35000 [ft] - 22.5 [min] IPC design pressure ratio 2.7 - (intercooled core) HPC design pressure ratio - 25.0 (intercooled core) HPC design pressure ratio - 5.5 (conventional core) HPC delivery temperature - 970 [K] HPC last stage blade height 10 [mm] - Combustor outlet temperature - 2050 [K] Turbine blade mean metal temperature - 1350 [K] (external surface) Auxiliary nozzle area variation Ref. +50% Time between overhaul 23000 [hr] - Table 1. Design space constraints. 2. Methodology To effectively explore the design space a tool is required that can consider the main disciplines typically encountered in conceptual design. The prediction of engine performance, aircraft design and performance, direct operating costs and emissions for the concepts analysed in this study was made using the code described in [6]. Another code described in [7], was also used for carrying out the mechanical and aerodynamic design in order to derive engine component weights and dimensions. The two tools have been integrated together within an optimizer environment as illustrated in Fig. 3 with a large amount of information being made available to the user during the design iteration. The integration allows for multi-objective optimization, design studies, parametric studies, and sensitivity analysis. In order to speed up the execution of individual engine designs, the conceptual design tool minimizes internal iterations in the calculation sequence through the use of an explicit algorithm, as described in detail by Kyprianidis [4]. For every engine design there are numerous practical limitations that need to be considered. A comprehensive discussion on design constraints for low specific thrust turbofans featuring conventional and heat exchanged cores can be found in [5]. The design space constraints set for this study are given in Table 1 and are considered applicable to a year 2020 entry into service turbofan engine. The effect on optimal concept selection of design constraints, material technology and customer requirements is discussed in the following sections. 3. Optimising a turbofan engine 3.1. Fuel-optimal designs Optimizing a turbofan engine design for minimum block fuel essentially has to consider the trade-off between better thermal and propulsive efficiency and reduced engine weight and nacelle drag. The cycle optimization results for the two powerplants are given in Table 2. Progress in Gas Turbine Performance 6 On Intercooled Turbofan Engines 5 10.5772/54402 Conventional core Intercooled core EIS 2020 EIS 2020 Fan diameter [in] 127 121 ISA SLS take-off thrust [lbf] 66000 64500 Overall pressure ratio 62.3 80.2 IPC pressure ratio 8.0 3.8 HPC pressure ratio 5.5 15.5 Fan mass flow [kg/s] 588 525 Core mass flow [kg/s] 36.3 34.6 Mid-cruise fan tip pressure ratio 1.30 1.39 Mid-cruise bypass ratio 17.7 17.3 Mid-cruise SFC Ref. -1.5% Mid-cruise thermal efficiency Ref. +0.019 (core + transmission efficiency) Mid-cruise propulsive efficiency Ref. -0.021 Engine installed weight Ref. -11.0% Fan weight Ref. -21.3% LPT weight Ref. -25.6% Core weight Ref. -20.9% Added components weight - 10.5% (as % of engine dry weight) Nacelle weight Ref. -14.7% MTOW [1000 kg] 208.5 203.4 OEW [1000 kg] 116.2 113.1 Block fuel weight Ref. -3.0% ∗ Performance parameters at top of climb conditions unless stated otherwise Table 2. Comparison of the fuel optimal intercooled and conventional core turbofan engine designs. Significant block fuel benefits are projected for the intercooled core engine, but they are smaller than those predicted in previous efforts [7]. This is mainly attributed to a minimum blade height requirement setting a practical lower limit on the intercooled core size for a given OPR. Increasing the fan diameter at a fixed tip speed inevitably reduces rotational speed, increases torque and hence increases the Low Pressure (LP) shaft diameter; this further aggravates the problem since the High Pressure Compressor (HPC) hub to tip ratio needs to increase. As a result, the optimal specific thrust for the intercooled core is higher compared to the conventional core turbofan engine. Although the high OPR intercooled core benefits from a higher core and transmission efficiency, and hence a better thermal efficiency, the conventional core benefits from a higher propulsive efficiency. The design space around the proposed fuel optimal designs was explored and in the next sections important observations are presented. 3.2. Approximating the design space In order to graphically illustrate the design space, a large number of simulations had to be carried out; these simulations were focused around the fuel-optimal designs presented in Section 3.1. Polynomial response surface models were derived that interpolate between On Intercooled Turbofan Engines http://dx.doi.org/10.5772/54402 7 6 Gas Turbine Figure 4. Variation of low pressure turbine stage count with fan inlet mass flow and fan tip pressure ratio for a fixed size conventional core. a given number of known designs. Typical design space discontinuities encountered as a result of turbomachinery stage count changes are inevitably distorted in polynomial approximations. For this reason, an error analysis was carried out to determine the discrepancy levels between the surrogate models and the actual design spaces; the approximation errors for engine weight and aircraft block fuel were found to be less than 1% and 0.2%, respectively. 3.3. Fan and core sizing Propulsive efficiency benefits from reducing specific thrust by increasing fan diameter can very well be negated by the resulting combination of: i) increased engine and nacelle weight, ii) increased nacelle (and interference) drag, and iii) reduced transmission efficiency. This section discusses various aspects of fan and core sizing for the conventional core and intercooled core configurations. When sizing the engine fan, assuming a fixed size core (i.e., fixed core inlet mass flow), large design space discontinuities are encountered due to Low Pressure Turbine (LPT) stage count changes, as illustrated in Fig.4. As discussed earlier, the use of smooth surrogate models for approximating discontinuous spaces inevitably results in approximation errors, and it is worth noting that the addition of an extra LPT stage results in approximately 150kg of additional weight. Nevertheless, with the fan and nacelle weight (including the thrust reverser) each being roughly double the LPT weight and directly proportional to the fan diameter, the weight trends illustrated in Fig. 5 can be considered reasonable. The improvement in mid-cruise uninstalled SFC from reducing specific thrust is illustrated in Fig. 6. If installation effects are ignored, then selecting a higher fan diameter (and hence a higher bypass ratio at a fixed size core) will result in better SFC. Nevertheless, the increased nacelle drag and engine weight move the optimal level of specific thrust for minimum block fuel to smaller fan diameters, as illustrated in Fig. 7. Progress in Gas Turbine Performance 8