scholarly journals CFD analysis of fluid flow in an axial multi-stage partial-admission ORC turbine

2015 ◽  
Vol 5 (1) ◽  
Author(s):  
Jan Surwilo ◽  
Piotr Lampart ◽  
Mariusz Szymaniak
Keyword(s):  
Working Conditions ◽  
Cfd Simulation ◽  
Organic Rankine Cycle ◽  
Rankine Cycle ◽  
Subsequent Stage ◽  
Cfd Analysis ◽  
3D Cad ◽  
Multi Stage ◽  
Partial Admission ◽  
Flow Domain

AbstractBasic operational advantages of the Organic Rankine Cycle (ORC) systems and specific issues of turbines working in these systems are discussed. The strategy for CFD simulation of the considered ORC turbine and the main issues of the numerical model are presented. The method of constructing the 3D CAD geometry as well as discretisation of the flow domain are also shown. Main features of partial admission flow in the multi-stage axial turbine are discussed. The influence of partial admission on the working conditions of the subsequent stage supplied at the full circumference is also described.

Numerical Investigation of a Partially Loaded Supersonic ORC Turbine Stage

2020 ◽  
Author(s):  
Karl Ziaja ◽  
Pascal Post ◽  
Marwick Sembritzky ◽  
Andreas Schramm ◽  
Ole Willers ◽  
...  
Keyword(s):  
Waste Heat ◽  
Organic Rankine Cycle ◽  
Rankine Cycle ◽  
Water Mixture ◽  
Loss Model ◽  
Sector Model ◽  
Exhaust Heat ◽  
Partial Admission ◽  
Loss Models ◽  
Lower Temperature

Abstract The Organic Rankine Cycle (ORC) represents an emerging technology aimed at exploiting lower temperature heat sources, like waste heat in industrial processes or exhaust heat in combustion engines. One key aspect of this technology is an efficient and economical operation at part load, typically realized by a partial admission control, which is challenging to predict numerically. Full annulus computation can only be avoided applying empirical partial admission loss models to conventional full-admission computations. This article aims at assessing the reliability of such a loss model under real-gas and supersonic conditions as a first step towards knowledge-based improved loss models. Three different operating points of an 18.3 kW ORC turbine working with an ethanol-water mixture with two open stator passages (2 × 36°) are considered. Full annulus CFD computations are compared to experimental data and results of simulations in a conventional, full admission, periodic 72°-sector model with application of a 1D partial admission loss model. The experimentally obtained mass flow rate and efficiency are matched overall within their measurements accuracy. By highest inlet total pressure, the computed efficiency deviates about 4 % from the experiments. Predictions of efficiency based on the full admission and loss model correction deviate from full annulus computations less than 1 %. These findings suggest that the used empirical correlations for partial admission losses can provide acceptable results in the configuration under investigation.

Numerical Investigation on the Performance of a Regenerative Flow Turbine for Small-Scale Organic Rankine Cycle Systems

2019 ◽  
Vol 141 (9) ◽  
Author(s):  
Ramin Moradi ◽  
Luca Cioccolanti ◽  
Enrico Bocci ◽  
Mauro Villarini ◽  
Massimiliano Renzi
Keyword(s):  
Organic Rankine Cycle ◽  
Rankine Cycle ◽  
Operating Conditions ◽  
Small Scale ◽  
Cfd Analysis ◽  
Cycle Systems ◽  
Mass Flow Rates ◽  
Computational Fluid Dynamics Cfd ◽  
Regenerative Flow ◽  
Operating Points

In this study, the performance characteristics of a regenerative flow turbine (RFT) prototype have been investigated by means of a computational fluid dynamics (CFD) study. The prototype has been initially designed to be used in gas pipelines replacing expansion valves but, because of the intrinsic characteristics of this kind of expander, its use can be extended to other applications like the expansion process in small-scale organic Rankine cycle (ORC) plants. In the first part of this work, the numerical results of the CFD analysis have been validated with the experimental data reported in literature for the same turbine prototype. After the validation of the model, a detailed study has been carried out in order to evaluate specific features of the turbine, focusing the attention on the typical operating conditions of small-scale low-temperature ORC systems. Results have shown that the considered RFT prototype operates with higher isentropic efficiencies (about 32% at 6000 rpm) at lower mass flow rates, while the power output is penalized compared to other operating points. The numerical analysis has also pointed out the high impact of the losses in the leakage flow in the gap between the blade tips and the stripper walls. Therefore, the CFD analysis carried out has provided a thoughtful understanding of the performance of the expander at varying operating conditions and useful insights for the future redesign of this kind of machine for the application in small-scale ORCs.

Aerodynamic Design and Analysis of Centrifugal Turbine Cascades

2013 ◽  
Author(s):  
G. Persico ◽  
M. Pini ◽  
V. Dossena ◽  
P. Gaetani
Keyword(s):  
Organic Rankine Cycle ◽  
Rankine Cycle ◽  
Acceleration Process ◽  
Flow Acceleration ◽  
Volumetric Expansion ◽  
Multi Stage ◽  
Aerodynamic Performances ◽  
Turbo Expander ◽  
Diverging Channel ◽  
Turbine Cascades

The centrifugal turbine architecture represents a promising solution for Organic Rankine Cycle (ORC) Systems, in the small-to-medium power range. The large volumetric expansion ratios occurring in ORC turbines complicate the design of the turbo-expander, making the centrifugal arrangement worth of interest with respect to conventional architectures. A new-concept centrifugal turbine has been recently proposed by the authors, based on the design of Ljungström but implementing a stator-rotor arrangement, which allows for multi-stage assembly without compromising compactness. To properly evaluate the potential of the centrifugal turbine solution, reliable data on cascade aerodynamic performances are required, but they are still lacking in the open literature. In this paper the aerodynamics of radial-outward turbine cascades is discussed, on the basis of Computational Fluid-Dynamics (CFD) simulations. A weakly transonic operating condition is selected and for that different classes of profiles are tested. Results show that the intrinsic diverging shape of the radial-outward configuration complicates the blade design; if the flow deflection is not properly controlled along the streamwise direction, the bladed duct can result in a converging-diverging channel, leading to unexpected chocked flows and shocks even in weakly transonic configurations. The indications achieved by the comparison between different blade profiles are gathered to define guidelines for the design of novel elliptic profiles, which allow to control the flow acceleration process, providing high aerodynamic efficiency. Off-design performances of the elliptic profiles are finally addressed by studying the response of the cascade to different expansion ratios and high incidence angles.

Numerical Investigation of a Partially Loaded Supersonic ORC Turbine Stage

2020 ◽  
Author(s):  
Karl Ziaja ◽  
Pascal Post ◽  
Marwick Sembritzky ◽  
Andreas Schramm ◽  
Ole Willers ◽  
...  
Keyword(s):  
Waste Heat ◽  
Organic Rankine Cycle ◽  
Rankine Cycle ◽  
Water Mixture ◽  
Loss Model ◽  
Sector Model ◽  
Exhaust Heat ◽  
Partial Admission ◽  
Loss Models ◽  
Lower Temperature

Abstract The Organic Rankine Cycle (ORC) represents an emerging technology aimed at exploiting lower temperature heat sources, like waste heat in industrial processes or exhaust heat in combustion engines. One key aspect of this technology is an efficient and economical operation at part load, typically realized by a partial admission control, which is challenging to predict numerically. Full annulus computation can only be avoided applying empirical partial admission loss models to conventional full-admission computations. This article aims at assessing the reliability of such a loss model under real-gas and supersonic conditions as a first step towards knowledge-based improved loss models. Three different operating points of an 18.3 kW ORC turbine working with an ethanol-water mixture with two open stator passages (2 x 36°) are considered. Full annulus CFD computations are compared to experimental data and results of simulations in a conventional, full admission, periodic 72°-sector model with application of a 1D partial admission loss model. The experimentally obtained mass flow rate and efficiency are matched overall within their measurements accuracy. By highest inlet total pressure, the computed efficiency deviates about 4 % from the experiments. Predictions of efficiency based on the full admission and loss model correction deviate from full annulus computations less than 1 %. These findings suggest that the used empirical correlations for partial admission losses can provide acceptable results in the configuration under investigation.

scholarly journals Design and Analysis of the Scroll Expander with Next Generation Refrigerant in an ORC

2019 ◽  
Vol 8 (2) ◽  
pp. 5687-5693
Keyword(s):  
Power Output ◽  
Waste Heat ◽  
Research Work ◽  
Organic Rankine Cycle ◽  
Rankine Cycle ◽  
Working Fluid ◽  
Slight Variation ◽  
Cfd Analysis ◽  
Medium Temperature ◽  
Scroll Expander

Organic Rankine Cycle (ORC) system is used to extract the waste heat from low to medium temperature heat source. The ORC system works as a reverse process of refrigeration. It has the four basic components of Condenser, Refrigerant pump, Evaporator and the Expander. The waste heat is absorbed in the Evaporator and the energy gained is used to rotate the expander which generate the power. The Expander used in the ORC are of different types like the scroll, Screw, Rotary, Turbo. Various refrigerants are used as the working fluid in the ORC system depending upon its physical and thermodynamic properties like R134a, R245fa etc. R245fa is currently used refrigerant in the ORC system. In recent research and development of the refrigerants, R1233zd(E) is also having suitable properties to be used in the ORC system. This refrigerant has zero ODP and very low GWP. This research work includes the analytical and the CFD analysis over the working fluid in the Scroll Expander of the ORC system. The working fluids considered for the analysis is R245fa which currently has a wide usage, and another is R1233zd(E) which has the suitable properties for ORC and is a green refrigerant. A specification for ORC system is considered and the p-h chart is plotted on the refrigerant charts for R245fa & R1233zd(E). The Scroll Fluid Geometry is drafted using ANSYS Design Modeller & Mesh. The Analytical & CFD analysis method is used to find the Force, Torque & Power output parameters for both the refrigerants under consideration at different operating angular positions. The results projected using the Analytical & the CFD method is almost similar with slight variation. The efficiency and the power output using the refrigerant R1233zd(E) is slightly less in comparison with the refrigerant R245fa. Considering the power output results from the scroll expander with both the working fluid under analysis, the refrigerant R1233zd(E) is a good alternate working fluid over the refrigerant R245fa in the ORC system with its Zero ODP and low GWP with a slight compromise over the power output from the ORC system.

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