scholarly journals Design Methodology for Supersonic Radial Vanes Operating in Nonideal Flow Conditions

2018 ◽  
Vol 141 (2) ◽  
Author(s):  
Nitish Anand ◽  
Salvatore Vitale ◽  
Matteo Pini ◽  
Gustavo J. Otero ◽  
Rene Pecnik
Keyword(s):  
Shock Wave ◽  
Fluid Dynamic ◽  
Dynamic Performance ◽  
Computational Cost ◽  
Organic Rankine Cycle ◽  
Suction Side ◽  
Rankine Cycle ◽  
Computational Effort ◽  
Design Guidelines ◽  
Boundary Layer Interaction

The stator vanes of high-temperature organic Rankine cycle (ORC) radial-inflow turbines (RIT) operate under severe expansion ratios and the associated fluid-dynamic losses account for nearly two-thirds of the total losses generated within the blading passages. The efficiency of the machine can strongly benefit from specialized high-fidelity design methods able to provide shapes attenuating shock wave formation, consequently reducing entropy generation across the shock-wave and mitigating shock-wave boundary layer interaction. Shape optimization is certainly a viable option to deal with supersonic ORC stator design, but it is computationally expensive. In this work, a robust method to approach the problem at reduced computational cost is documented. The method consists of a procedure encompassing the method of characteristics (MoC), extended to nonideal fluid flow, for profiling the diverging part of the nozzle. The subsonic section and semibladed suction side are retrieved using a simple conformal geometrical transformation. The method is applied to design a supersonic ORC stator working with Toluene vapor, for which two blade shapes were already available. The comparison of fluid-dynamic performance clearly indicates that the MoC-Based method is able to provide the best results with the lowest computational effort, and is therefore suitable to be used in a systematic manner for drawing general design guidelines.

Novel Shape Parametrization Technique Applied to the Optimization of a Supersonic ORC Turbine Cascade

2018 ◽  
Author(s):  
Alessandro Romei ◽  
Giacomo Persico
Keyword(s):  
High Performance ◽  
Computational Cost ◽  
Organic Rankine Cycle ◽  
Suction Side ◽  
Rankine Cycle ◽  
Optimization Techniques ◽  
Evolutionary Strategies ◽  
Control Points ◽  
Turbine Cascade ◽  
Performance Targets

Shape-optimization techniques are nowadays an essential tool in the design chain of turbomachinery to strike the high-performance targets demanded by modern applications. Although the geometric parametrization may affect significantly the optimization cost and ultimately the optimization outcome, the selection of control points and of the subsequent design space is usually based on heuristic considerations. This paper proposes a cost-efficient parametrization procedure based on the ANOVA analysis of B-Spline control points. To tackle the extremely large computational burden arisen from the use of several control points, a surrogate strategy is implemented, testing four different methods. The optimization relies on surrogate-assisted evolutionary strategies coupled with an experimentally validated CFD solver. The technique is applied to a supersonic Organic Rankine Cycle turbine cascade, which features a converging-diverging bladed channel. It is shown that only the diverging section of the suction side as well as the adjacent region of unguided turning have the major impact on the aerodynamic performance. These findings enable to select an optimal distribution of mobile control points in the optimization block, leading to significant savings in computational cost. Finally, three optimizations are carried out, varying locally the number of control points; results are widely discussed in terms of both optimization outcomes and optimizer robustness.

Unsteady Operation of a Highly Supersonic Organic Rankine Cycle Turbine

2016 ◽  
Vol 138 (12) ◽  
Author(s):  
Enrico Rinaldi ◽  
Rene Pecnik ◽  
Piero Colonna
Keyword(s):  
Boundary Layer ◽  
Organic Rankine Cycle ◽  
Suction Side ◽  
Rankine Cycle ◽  
Boundary Layer Separation ◽  
Expansion Ratio ◽  
Ideal Gas ◽  
Rotor Blades ◽  
Navier Stokes ◽  
Shock Interactions

Organic Rankine cycle (ORC) turbogenerators are the most viable option to convert sustainable energy sources in the low-to-medium power output range (from tens of kWe to several MWe). The design of efficient ORC turbines is particularly challenging due to their inherent unsteady nature (high expansion ratios and low speed of sound of organic compounds) and to the fact that the expansion encompasses thermodynamic states in the dense vapor region, where the ideal gas assumption does not hold. This work investigates the unsteady nonideal fluid dynamics and performance of a high expansion ratio ORC turbine by means of detailed Reynolds-averaged Navier–Stokes (RANS) simulations. The complex shock interactions resulting from the supersonic flow (M ≈ 2.8 at the vanes exit) are related to the blade loading, which can fluctuate up to 60% of the time-averaged value. A detailed loss analysis shows that shock-induced boundary layer separation on the suction side of the rotor blades is responsible for most of the losses in the rotor, and that further significant contributions are given by the boundary layer in the diverging part of the stator and by trailing edge losses. Efficiency loss due to unsteady interactions is quantified in 1.4% in absolute percentage points at design rotational speed. Thermophysical properties are found to feature large variations due to temperature even after the strong expansion in the nozzle vanes, thus supporting the use of accurate fluid models in the whole turbine stage.

Dynamic performance of an organic Rankine cycle system with a dynamic turbine model: A comparison study

2020 ◽  
Vol 181 ◽  
pp. 115940
Author(s):  
Yaxiong Wang ◽  
Jiangfeng Wang ◽  
Ziyang Cheng ◽  
Qingxuan Sun ◽  
Pan Zhao ◽  
...  
Keyword(s):  
Dynamic Performance ◽  
Organic Rankine Cycle ◽  
Rankine Cycle ◽  
Comparison Study ◽  
Cycle System ◽  
Turbine Model

Preliminary Design of the ORCHID: A Facility for Studying Non-Ideal Compressible Fluid Dynamics and Testing ORC Expanders

2016 ◽  
Author(s):  
Adam Joseph Head ◽  
Carlo De Servi ◽  
Emiliano Casati ◽  
Matteo Pini ◽  
Piero Colonna
Keyword(s):  
Power Systems ◽  
Power Output ◽  
Fluid Dynamic ◽  
Supersonic Nozzle ◽  
Organic Rankine Cycle ◽  
Rankine Cycle ◽  
Operating Conditions ◽  
Performance Estimation ◽  
Preliminary Design ◽  
Integrated Device

Organic Rankine Cycle (ORC) power systems are receiving increased recognition for the conversion of thermal energy when the source potential and/or its temperature are comparatively low. Mini-ORC units in the power output range of 3–50 kWe are actively studied for applications involving heat recovery from automotive engines and the exploitation of solar energy. Efficient expanders are the enabling components of such systems, and all the related developments are at the early research stage. Notably, no experimental gasdynamic data are available in the open literature concerning the fluids and flow conditions of interest for mini-ORC expanders. Therefore, all the performance estimation and the fluid dynamic design methodologies adopted in the field rely on non-validated tools. In order to bridge this gap, a new experimental facility capable of continuous operation is being designed and built at Delft University of Technology, the Netherlands. The Organic Rankine Cycle Hybrid Integrated Device (ORCHID) is a research facility resembling a state-of-the-art high-temperature ORC system. It is flexible enough to treat different working fluids and operating conditions with the added benefit of two interchangeable Test Sections (TS’s). The first TS is a supersonic nozzle with optical access whose purpose is to perform gas dynamic experiments on dense organic flows in order to validate numerical codes. The second TS is a test-bench for mini-ORC expanders of any configuration up to a power output of 100 kWe. This paper presents the preliminary design of the ORCHID setup, discussing how the required operational flexibility was attained. The envisaged experiments of the two TS’s are also described.

scholarly journals Development and Experimental Validation of Real Fluid Models for CFD Calculation of ORC and Steam Turbine Flows

Materials ◽  
2021 ◽  
Vol 14 (22) ◽  
pp. 6879
Author(s):  
Andrii Rusanov ◽  
Roman Rusanov ◽  
Piotr Klonowicz ◽  
Piotr Lampart ◽  
Grzegorz Żywica ◽  
...  
Keyword(s):  
Experimental Data ◽  
Equation Of State ◽  
Steam Turbine ◽  
Thermodynamic Parameters ◽  
Equations Of State ◽  
Computational Cost ◽  
Organic Rankine Cycle ◽  
Rankine Cycle ◽  
Large Power ◽  
Wide Range

The article describes an interpolation–analytical method of reconstruction of the IAPWS-95 equations of state and the modified Benedict–Webb–Rubin equations of state with 32 terms (mBWR32). The method enables us to provide the thermodynamic closure in 3D computational fluid dynamics (CFD) calculations of turbomachinery flows with real working media, such as steam and Organic Rankine Cycle (ORC) fluids. The described approach allows for the sufficient accuracy of 3D flow calculations and does not require a significant increase in computational cost over perfect gas calculations. The method is validated against experimental data from measurements and compared with computational results from the model using the Tammann equation of state. Three turbine blading systems are considered—a multi-stage configuration from a low-pressure cylinder of a large-power steam turbine and two ORC microturbines working with organic media HFE7100 and R227ea. The calculation results obtained using the described method of approximation of the IAPWS-95 and mBWR32 equations exhibit satisfactory agreement with the experimental data, considering pressures, temperatures and enthalpies in key sections, as well as turbine power and efficiency in a wide range of changing thermodynamic parameters. In contrast, the Tammann equation of state provides acceptable results only for relatively small changes of thermodynamic parameters.

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