The development of Supercritical CO2 (S-CO2) power cycles is currently a major focus of the engineering and scientific community. The reason for such a growing interest in this type of power can be explained by the significant benefits in size and efficiency of power cycles, which use S-CO2 as a working fluid, as compared to conventional steam power generation. Many areas of application such as nuclear, solar, waste heat, energy storage, and clean coal combustion, are being studied for S-CO2 power production. Most of the publications discussing S-CO2 are concentrated on optimization of the cycle’s thermodynamic characteristics, topping and bottoming and have been conceptualized based on the heat source. At the same time, numerous aspects of turbomachinery design are often overlooked or are not well understood. This article discusses some specific engineering aspects of the design of turbine flow path which uses S-CO2 as a working fluid. The following design options have been studied to determine the best turbine configuration: number of stages, rotational speed, impulse versus reaction, types of stages, and radial clearance influence. The effect of larger bending loads, resulting from high power density on nozzles and blade chords size and, consequently, turbine length, has also been studied. The authors hope that the results presented in the article will help the engineering community design better S-CO2 turbomachinery.
An effective methodology for optimal design of axial turbine blades is presented. It has been used for achieving stage maximal efficiency meeting both stress-strain and vibration reliability requirements and taking into account technological limitations.
Bottoming cycles are drawing a real interest in a world where resources are becoming scarcer and the environmental footprint of power plants is becoming more controlled. Reduction of flue gas temperature, power generation boost without burning more fuel and even production of heat for cogeneration applications are very attractive and it becomes necessary to quantify how much can really be extracted from a simple cycle to be converted to a combined configuration. As supercritical CO2 is becoming an emerging working fluid [2, 3, 5, 7 and 8] due not only to the fact that turbomachines are being designed significantly more compact, but also because of the fluid’s high thermal efficiency in cycles, it raises an increased interest in its various applications. Evaluating the option of combined gas and supercritical CO2 cycles for different gas turbine sizes, gas turbine exhaust gas temperatures and configurations of bottoming cycle type becomes an essential step toward creating guidelines for the question, “how much more can I get with what I have?”. Using conceptual design tools for the cycle system generates fast and reliable results to draw this type of conclusion. This paper presents both the qualitative and quantitative advantages of combined cycles for scalability using machines ranging from small to several hundred MW gas turbines to determine which configurations of S-CO2 bottoming cycles are best for pure electricity production.
Raising requirements for aircraft engine efficiency and fuel consumption level combined with strong restrictions to engine weight and geometrical dimension pose serious challenges for engineers who are working under the new generation of engine development. These tasks require brand new flow path design approaches. The usage of a counter-rotating turbine is one of the possible ways to successfully match all these requirements. Modern aerodynamic design computational and optimization methodologies allow to fulfil this task in the shortest period of time with the highest gain in turbine performances. A counter-rotating turbine means that blade rows are joined to two shafts with opposite rotation direction and different rotation speeds. Vanes elimination in a counter-rotating turbine helps to solve three important tasks of turbine improvement: • Increasing turbine efficiency by eliminating vanes and correspondingly losses in vanes; • Decreasing turbine blading weight; • Decreasing turbine axial length; These improvements are impossible without such fundamental design changes. In the current paper the steps of counter-rotating turbine aerodynamic design, optimization, and offdesign performances estimation are described. The comparison of traditional and counter rotating turbines integral and detailed thermodynamic performances are presented.
A new method for centrifugal and mixed-type compressors flow paths design based on a unique integrated conceptual design environment is presented in this article. At the heart of this new method is the translation of proven, integrated design environments that have been successfully used for axial turbomachinery for many years. This integrated environment is a seamless and swift processing scheme that incorporates stages aerodynamic analysis and preliminary design/sizing based on the one-dimensional method interactive spatial blade profiling, export of blade geometry to CAD and CFD tools, 3D stress and vibration analysis, and finally, flow modeling. The design process is demonstrated for a centrifugal compressor design utilizing AxSTREAM software.
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