Gas Turbine Engineering Handbook discusses the design, manufacture, installation, operation and maintenance of gas turbines. The third edition is an upgrade in the design and maintenance of advanced gas turbines and covers most applicable codes, both in terms of performance and mechanical standards. The use of gas turbines in the petrochemical, power generation and offshore industries has exploded in recent years.
The electric power industry has in the last ten years embraced combined cycle power plants, and new high-efficiency gas turbines are at the heart of this growing segment of the industry. I have been involved in the research, design, operation and maintenance of gas turbines since the early 1960s. In this publication I have attempted to assimilate the subject matter of various works (and sometimes differing views) into a comprehensive and unified treatment. of gas turbines.
Preface to the Second Edition
The Texas A&M University Turbomachinery Symposium, which I had the privilege of organizing and chairing for over eight years and serving on the advisory committee for 30 years, is a major contributor to the operation and maintenance sections of this book. It is hoped that this book will serve as a reference text after it has fulfilled its primary objective of introducing the reader to the broad subject of gas turbines. Special thanks go to the Texas A&M University Turbomachinery Symposium Advisory Committee and Dr.
Simmang, chairman of the Texas A&M University Department of Mechanical Engineering, who were instrumental in introducing the manuscript. I sincerely hope that this new edition will be as interesting to read as it was for me to write, and that it will be a useful reference to the rapidly growing field of turbomachinery. Simmang, who wrote the foreword to the first edition of this book, is a great loss not only to me, but also to the engineering education community and to many of his students at Texas A&M University.
Preface to the First Edition
Simmango, chairman of the mechanical engineering department at Texas A&M University, who was instrumental in the creation of the manuscript, and Janet Broussard for first typing the manuscript. We are also grateful for the competent guidance of William Lowe and Scott Becken of Gulf Publishing Company. Their cooperation and patience made it easy to turn a rough manuscript into a finished book.
I sincerely hope that this book will be as interesting to read as it was for me to write, and that it will be a useful reference for the rapidly growing field of turbomachinery. In the following centuries, the principle of the aeolipile appeared in the windmill (AD and again in the motorized spit (17th century). The establishment of the annual Texas A&M University Turbomachinery Symposium can be counted among his major contributions to the field of turbomachinery.
Design: Theory and Practice
An Overview of Gas Turbines
Aerospace engines have been the leaders in most gas turbine technology. All this has changed in the last 10 years; driven by the introduction of the "Aero-Derivative Gas Turbine", the industrial gas turbine has dramatically improved its performance in all operational aspects. The adiabatic efficiency of compressors has also increased and efficiencies in the high 80s have been achieved.
Most of the velocity leaving the impeller is converted into pressure energy in the diffuser. Preheated combustion air is obtained by diverting part of the exhaust gases from the gas turbine. The high pressure ratio in the compressor also ensures that the cooling air used in the first stages of the turbine is very hot.
Steam cooling is possible in the new combined cycle power plants, which are the basis of most of the new high performance gas turbines. The use of pyrometers in the control of the advanced gas turbines is investigated.
Theoretical and
Actual Cycle Analysis
With these assumptions the effect on the ideal cycle efficiency as a function of pressure ratio for the ideal Brayton cycle is between. the ambient temperature and the fire temperature are given by the following relationship:. Variation of a gas turbine cycle efficiency with heat exchanger performance. the honeycomb passages that the air would encounter, then the cooler air would pass through these same passages as the drum was rotated and would be heated. The advantage of the split-shaft gas turbine is its high torque at low speeds.
From Figure 2-4 and the definition of a regenerator, the regenerator outlet temperature. The steam is injected after the compressor but far upstream of the combustor to create a proper. Gas turbine calculations are the same as shown for the simple cycle.
The combined cycle work is equal to the sum of the net gas turbine work and steam turbine work. In the typical combination, the gas turbine produces approx. 60% of the effect and the steam turbine approx. 40%. The steam turbine utilizes the energy in the gas turbine's exhaust gas as its input energy.
This increases the efficiency of the steam turbine and therefore the efficiency of the combined cycle. Expanding the steam at higher steam pressure causes an increase in the moisture content at the exit of the steam turbine. Combination of evaporative and cooled intake systems - The use of evaporative coolers to help the cooling system achieve lower intake air temperatures.
This mist then provides cooling as it evaporates in the gas turbine air intake duct. Injection of steam into the combustion chamber of gas turbines using existing dual fuel nozzles. In the case of the heated and humidified compressed air injected system, the air must be saturated.
Compressor and Turbine
Performance Characteristics
The total pressure is the pressure of the gas being brought to rest in a reversibly adiabatic manner. -3) where ρV2/2gc is the dynamic pressure head indicating the speed of the moving gas. The acoustic velocity is defined as the ratio change in the pressure of the gas to its density when the entropy is held constant:
Finally, using the definition of the Mach number, the speed of the gas flow can be calculated. The continuity equation is a mathematical formulation of the law of conservation of mass of a gas that is a continuum. The isentropic efficiency of the compressor can be written in terms of the total changes in enthalpy.
The isentropic efficiency of the turbine can be written in terms of the total enthalpy change. The flow coefficient is the capacity of the flow rate, expressed in dimensionless form. The variation of the final results will depend on the scale-up factor and the difference in the liquid medium.
Common practice is to plot velocity lines as a function of given pressure and flow. In this map, constant aerodynamic velocity lines are functions of power and flow velocity. Below is a sample calculation of the techniques used to determine the performance of a gas turbine.
This figure shows that below 50% of the rated load, the combination cycle is not effective.
Performance and
Mechanical Standards
The only task of the turbine part of the gasifier is to drive the gas turbine compressor. For most onshore applications, if the plant size exceeds 100 MW, the frame type is most suitable for a gas turbine. The type of fuel is one of the most important aspects when choosing a gas turbine.
These types of cycles affect the life of many of the hot section components in the gas turbine. This section covers some of the applicable API and ASME standards for the gas turbine and other associated components. In combination with the API specifications, the following ASME codes also provide important data for proper gas turbine selection.
The standard is limited to a consideration of the basic gas turbine including the compressor, combustion system and turbine. The transmission is limited to the protective transmission of the electrical system used to protect the gas turbine station itself. The standards define terms used in the industry and describe the basic design of the unit.
Torque criticals should be at least 10% away from the first or second harmonic of the rotating frequency. Separate lubrication systems for various sections of the turbine and driven equipment can be provided. Purging the fuel system after a failed start is mandatory, even in manual operation mode.
Critical speeds correspond to the natural frequencies of the gears and the rotor bearing support system.
Rotor Dynamics
The number of independent coordinates that describe the system motion are called the degrees of freedom of the system. A single degree of freedom system is one that requires a single independent coordinate to fully describe its vibrational configuration. Systems with two or more degrees of freedom vibrate in a complex manner where frequency and amplitude have no definite relationship.
Among the multitude of disordered motions there are some very special kinds of ordered motion, called principal modes of oscillation. Among these main modes of vibration, each point in the system follows a specific pattern of common frequency. The simplest form of periodic motion is harmonic motion, which can be represented by a sine or cosine function.
It is important to remember that harmonic motion is always periodic; however, periodic motion is not always harmonic. Thus, we can determine the velocity and acceleration of this system by differentiating the equation with respect to t. The angles between the vectors are called phase angles; so we can say that the velocity leads the displacement by 90◦ and the acceleration acts in the opposite direction to the displacement or that it leads the displacement by 180◦.
This system is the simplest of all vibration systems and consists of a mass suspended on a spring of negligible mass. If the mass is displaced from its original equilibrium position and released, the unbalanced force, the recovery (−Kx) of the spring and acceleration are related by Newton's second law. Assuming that a harmonic function will satisfy the equation, let the solution be of the form.
Solid damping, often called structural damping, is due to internal friction within the material itself.
