Leonid Moroz

Methods and Tools for Multidisciplinary Optimization of Axial Turbine Stages With Relatively Long Blades

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.

Integrated Conceptual Design Environment for Centrifugal Compressors Flow Path Design

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 onedimensional 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.

Axial Turbine Stage Design: 1D/2D/3D Simulation, Experiment, Optimization — Design of Single Stage Test Air Turbine Models and Validation of 1D/2D/3D Aerodynamic Computation Results Against Test Data

In recent decade, industry had started to use intensively 3D simulation in turbine flow path and its components design. At the same time, this remains a very labor- and time-consumable process that sufficiently hampers its usage, whereas unidimensional and axisymmetric analyses are still widely used in the industry practice. A comparison of the data obtained from experiments conducted on a single stage air turbine test model with the results of 1D and 2D modeling and 3D simulation using a CFD solver was performed. The results were analyzed to validate a judgement of the authors that along with 3D CFD methods the low-fidelity models can be successfully used for turbine flow path optimization with the help of DoE methods. The forthcomings and advantages of different models are also discussed.Copyright

DESIGNING SUPERCRITICAL CO2 POWER PLANTS USING AN INTEGRATED DESIGN SYSTEM

The use of S-CO2 as working fluid in a power cycle has been growing in recent years due to associated benefits such as highly compact power plant and high cycle thermal efficiencies for application including waste heat, solar thermal and nuclear power plants. Many authors have presented studies on S-CO2 cycle and its modifications and there also exists many patents which claim different embodiments of the S-CO2 cycle for different heat sources. Each author of the S-CO2 cycle embodiment uses some specific tool to analyze the cycle performance with assumed values of component efficiencies. In the S-CO2 cycle the ratio of turbine work to compressor work is relatively small and its variation may cause a significant influence on cycle performance estimation accuracy. Exact prediction of the S-CO2 cycle performance requires defining exact turbomachinery efficiency magnitudes. However, S-CO2 turbines and compressors are in development stage except for several low power scale prototypes and hence it is very difficult to make assumptions on efficiency and they need to be designed.To enable design of cycle from concept to detailed design of the turbomachinery, the authors in this work have developed a flexible design system which is starting from heat balance calculation, continues with sizing of turbomachinery flow path, through 1D/2D/3D aero and structural multidisciplinary optimization. Such a design process is iterative because a refinement of the turbomachinery efficiencies lead to change in cycle boundary conditions for turbomachinery design and the design needs to be refined by recalculation of the cycle. In the present work, four different embodiments of S-CO2 thermodynamic cycles were analyzed using assumed component efficiencies and based on the actual design of the turbomachinery components the cycle was recalculated and accurate performance of the cycle was predicted. It is observed that the turbine efficiency has significant influence on the overall cycle performance compared to the compressor efficiency.Copyright

Improved Model for Meanline Analysis of Centrifugal Compressors with a Large Tip Clearance

For small fast centrifugal wheels, the relative tip clearance can be large even for tenths of millimeters absolute clearance. Some of these impellers inherently have large relative clearance due to boundary conditions, geometry limitations, and mechanical design of the compressor. In the presented work, a centrifugal impeller large tip clearance model (LTCM) is developed. LTCM improves existing state-of-the-art compressor loss models by effecting flow kinematics and introducing impeller discharge recirculation. LTCM model is validated against experimental results and has good agreement with 3D CFD results.

Design and Analysis of a High Pressure Ratio Mixed Flow Compressor Stage

Due to higher specific speed compared to conventional centrifugal compressors, mixed flow compressors results in lower frontal area and are hence preferred for small gas turbine engines. With the requirements of higher pressure ratio in mixed flow compressors, the flow at the exit of an impeller is transonic resulting in a complex interaction between the exit flow of impeller and diffuser inlet. Transonic flow in the diffuser, in turn, results in higher diffuser total pressure losses. The design of diffuser for minimizing the pressure loss requires deeper understanding of the flow in the impeller and its interaction with the diffuser. In the present work, a mixed flow compressor stage for a pressure ratio of 5:1 has been designed with isentropic efficiency around 80%. The introduction of diffuser resulted in efficiency degradation. Detailed studies of the flow field give an understanding of the diffuser design. Diffuser geometry has been optimized to improve the overall efficiency of the compressor stage.

Evaluation for Scalability of a Combined Cycle Using Gas and Bottoming SCO2 Turbines

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.Copyright