scholarly journals Sensitivity of Supersonic ORC Turbine Injector Designs to Fluctuating Operating Conditions

2015 ◽  
Author(s):  
Elio A. Bufi ◽  
Paola Cinnella ◽  
Xavier Merle
Keyword(s):  
Method Of Characteristics ◽  
Organic Rankine Cycle ◽  
Design Procedure ◽  
Rankine Cycle ◽  
Operating Conditions ◽  
Real Gas ◽  
Real Gas Effects ◽  
Nozzle Shape ◽  
Turbine Design ◽  
The Impact

The design of an efficient organic rankine cycle (ORC) expander needs to take properly into account strong real gas effects that may occur in given ranges of operating conditions, which can also be highly variable. In this work, we first design ORC turbine geometries by means of a fast 2-D design procedure based on the method of characteristics (MOC) for supersonic nozzles characterized by strong real gas effects. Thanks to a geometric post-processing procedure, the resulting nozzle shape is then adapted to generate an axial ORC blade vane geometry. Subsequently, the impact of uncertain operating conditions on turbine design is investigated by coupling the MOC algorithm with a Probabilistic Collocation Method (PCM) algorithm. Besides, the injector geometry generated at nominal operating conditions is simulated by means of an in-house CFD solver. The code is coupled to the PCM algorithm and a performance sensitivity analysis, in terms of adiabatic efficiency and power output, to variations of the operating conditions is carried out.

A Study of the Three-Dimensional Unsteady Real-Gas Flows Within a Transonic ORC Turbine

2014 ◽  
Author(s):  
Andrew P. S. Wheeler ◽  
Jonathan Ong
Keyword(s):  
Three Dimensional ◽  
Organic Rankine Cycle ◽  
Leading Edge ◽  
Rankine Cycle ◽  
Gas Flows ◽  
Cfd Simulations ◽  
Significant Drop ◽  
Real Gas ◽  
Turbine Efficiency ◽  
Real Gas Effects

In this paper we investigate the three-dimensional unsteady real-gas flows which occur within Organic Rankine Cycle (ORC) turbines. A radial-inflow turbine stage operating with supersonic vane exit flows (M ≈ 1.4) is simulated using a RANS solver which includes real-gas effects. Steady CFD simulations show that small changes in the inducer shape can have a significant effect on turbine efficiency due to the development of supersonic flows in the rotor. Unsteady predictions show the same trends as the steady CFD, however a strong interaction between the vane trailing-edge shocks and rotor leading-edge leads to a significant drop in efficiency.

Assessment of Tesla Turbine Performance for Small Scale Rankine Combined Heat and Power Systems

2010 ◽  
Vol 132 (12) ◽  
Author(s):  
Van P. Carey
Keyword(s):  
Power Systems ◽  
Residential Buildings ◽  
Rankine Cycle ◽  
Combined Heat And Power ◽  
Operating Conditions ◽  
Working Fluid ◽  
Small Scale ◽  
Manufacturing Cost ◽  
Turbine Design ◽  
The Impact

For solar Rankine cycle combined heat and power systems for residential buildings and other small-scale applications (producing 1–10 kWe), a low manufacturing cost, robust, and durable expander is especially attractive. The Tesla-type turbine design has these desired features. This paper summarizes a theoretical exploration of the performance of a Tesla turbine as the expander in a small-scale Rankine cycle combined heat and power system. A one-dimensional idealized model of momentum transfer in the turbine rotor is presented, which can be used to predict the efficiency of the turbine for typical conditions in these systems. The model adopts a nondimensional formulation that identifies the dimensionless parameters that dictate performance features of the turbine. The model is shown to agree well with experimental performance data obtained in earlier tests of prototype Tesla turbine units. The model is used to explore the performance of this type of turbine for Rankine cycle applications using water as a working fluid. The model indicates that isentropic efficiencies above 0.75 can be achieved if the operating conditions are tailored in an optimal way. The scalability of the turbine design, and the impact of the theoretical model predictions on the development of solar combined heat and power systems are also discussed.

A Preliminary Turbine Design for an Organic Rankine Cycle

2013 ◽  
Author(s):  
T. Efstathiadis ◽  
M. Rivarolo ◽  
A. I. Kalfas ◽  
A. Traverso ◽  
P. Seferlis
Keyword(s):  
Organic Rankine Cycle ◽  
Rankine Cycle ◽  
Operating Conditions ◽  
Design Parameters ◽  
Working Fluid ◽  
Energy Sources ◽  
Small Scale ◽  
Choked Flow ◽  
Turbine Speed ◽  
Turbine Design

An increasing trend in exploiting low enthalpy content energy sources, has led to a renewed interest in small-scale turbines for Organic Rankine Cycle applications. The design concept for such turbines can be quite different from either standard gas or steam turbine designs. The limited enthalpic content of many energy sources enforces the use of organic working media, with unusual properties for the turbine. A versatile cycle design and optimization requires the parameterization of the prime turbine design. In order to address the major challenges involved in this process, the present study discusses the preliminary design of an electricity-producing turbine, in the range of 100 kWel, for a low enthalpy organic Rankine cycle. There are many potential applications of this power generating turbine including geothermal and solar thermal fields or waste heat of PEM type fuel cells. An integrated model of equations has been developed, accordingly. The model aims to assess the performance of an organic cycle for various working fluids, including NH3, R600a and R-134a. The most appropriate working fluid has been chosen, taking into consideration its influence on both cycle efficiency and the specific volume ratio. The influence of this choice is of particular importance at turbine extreme operating conditions, which are strongly related to the turbine size. In order to assess the influence of various design parameters, a turbine design tool has been developed and applied to preliminarily define the blading geometry. Finally, a couple of competitive turbine designs have been developed. In one approach, the turbine speed is restricted to subsonic domain, while in the other approach the turbine speed is transonic, resulting to choked flow at the turbine throat. The two approaches have been evaluated in terms of turbine compactness and machine modularity. Results show that keeping the crucial parameters of the geometrical formation of the blade constant, turbine size could become significantly smaller decreasing up to 90% compared its original value.

scholarly journals Dynamic Modeling and Control System Definition for a Micro-CSP Plant Coupled With Thermal Storage Unit

2014 ◽  
Author(s):  
Melissa K. Ireland ◽  
Matthew S. Orosz ◽  
J. G. Brisson ◽  
Adriano Desideri ◽  
Sylvain Quoilin
Keyword(s):  
Rural Communities ◽  
Organic Rankine Cycle ◽  
Rankine Cycle ◽  
Thermal Storage ◽  
Energy Coupling ◽  
Operating Conditions ◽  
Small Scale ◽  
Storage Unit ◽  
Modeling And Control ◽  
The Impact

Organic Rankine cycle (ORC) systems are gaining ground as a means of effectively providing sustainable energy. Coupling small-scale ORCs powered by scroll expander-generators with solar thermal collectors and storage can provide combined heat and power to underserved rural communities. Simulation of such systems is instrumental in optimizing their control strategy. However, most models developed so far operate at steady-state or focus either on ORC or on storage dynamics. In this work, a model for the dynamics of the solar ORC system is developed to evaluate the impact of variable heat sources and sinks, thermal storage, and the variable loads associated with distributed generation. This model is then used to assess control schemes that adjust operating conditions for daily environmental variation.

Real-Gas Effects in Organic Rankine Cycle Turbine Nozzles

2008 ◽  
Vol 24 (2) ◽  
pp. 282-294 ◽  
Author(s):  
P. Colonna ◽  
J. Harinck ◽  
S. Rebay ◽  
A. Guardone
Keyword(s):  
Organic Rankine Cycle ◽  
Rankine Cycle ◽  
Real Gas ◽  
Real Gas Effects

scholarly journals Numerical Study of Multistage Transcritical Organic Rankine Cycle Axial Turbines

2014 ◽  
Vol 136 (8) ◽  
Author(s):  
L. Sciacovelli ◽  
P. Cinnella
Keyword(s):  
Numerical Study ◽  
Pressure Ratio ◽  
Organic Rankine Cycle ◽  
Rankine Cycle ◽  
Operating Conditions ◽  
Working Fluid ◽  
Dense Gas ◽  
Working Fluids ◽  
Inlet Conditions ◽  
The Impact

Transonic flows through axial, multistage, transcritical organic rankine cycle (ORC) turbines are investigated by using a numerical solver including advanced multiparameter equations of state and a high-order discretization scheme. The working fluids in use are the refrigerants R134a and R245fa, classified as dense gases due to their complex molecules and relatively high molecular weight. Both inviscid and viscous numerical simulations are carried out to quantify the impact of dense gas effects and viscous effects on turbine performance. Both supercritical and subcritical inlet conditions are studied for the considered working fluids. In the former case, flow across the turbine is transcritical, since turbine output pressure is subcritical. Numerical results show that, due to dense gas effects characterizing the flow at supercritical inlet conditions, supercritical ORC turbines enable, for a given pressure ratio, a higher isentropic efficiency than subcritical turbines using the same working fluid. Moreover, for the selected operating conditions, R134a provides a better performance than R245fa.

Investigating the Effect of Changing the Working Fluid on the Three-Dimensional Flow Within Organic Rankine Cycle Turbines

2016 ◽  
Author(s):  
M. White ◽  
A. I. Sayma
Keyword(s):  
Low Cost ◽  
Organic Rankine Cycle ◽  
Rankine Cycle ◽  
High Volume ◽  
Detailed Comparison ◽  
Operating Conditions ◽  
Working Fluid ◽  
Working Fluids ◽  
Turbine Design ◽  
Similitude Theory

For small and micro scale (< 50 kWe) organic Rankine cycle (ORC) systems to be commercially viable, systems are required that can operate efficiently over a range of operating conditions. This will lead to the high volume, low cost production that is critical to improve the current economy of scale, and reduce system costs. This requirement will inevitably mean utilising the same system within a range of different applications and may also require the same turbine to operate in different systems where the working fluid may change. Under these circumstances it is therefore important to develop suitable models that can determine the off design performance of these turbines. This will help to understand how the performance of existing ORC turbines responds to such changes. This topic is also of interest when considering retrofitting existing systems with more modern working fluids, which meet current environmental regulations. Recent work by the authors has developed a turbine design model and produced a candidate radial turbine design. Furthermore a modified similitude theory has been developed and validated, which can be used to predict turbine performance following a change in working fluid. This paper extends this analysis to a wider array of working fluids, and in addition to comparing the important performance parameters such as mass flow rate and turbine efficiency, a detailed comparison of the resulting flow field, blade loading distributions and velocity triangles is also presented. Predictions made using the modified similitude theory are compared to steady and unsteady 3D RANS CFD simulations completed using the commercial solver ANSYS CFX. Real fluid properties are accounted for by generating property tables using REFPROP. By comparing these important flow features the validity of the modified similitude model can be examined to a much greater extent.

Toward the Integrated Design of Organic Rankine Cycle Power Plants: A Method for the Simultaneous Optimization of Working Fluid, Thermodynamic Cycle, and Turbine

2019 ◽  
Vol 141 (11) ◽  
Author(s):  
Matthias Lampe ◽  
Carlo De Servi ◽  
Johannes Schilling ◽  
André Bardow ◽  
Piero Colonna
Keyword(s):  
Integrated Design ◽  
Organic Rankine Cycle ◽  
Design Procedure ◽  
Thermodynamic Cycle ◽  
Rankine Cycle ◽  
Operating Conditions ◽  
Working Fluid ◽  
Small Scale ◽  
Iterative Design ◽  
Selection Of

Abstract The conventional design of organic Rankine cycle (ORC) power systems starts with the selection of the working fluid and the subsequent optimization of the corresponding thermodynamic cycle. More recently, systematic methods have been proposed integrating the selection of the working fluid into the optimization of the thermodynamic cycle. However, in both cases, the turbine is designed subsequently. This procedure can lead to a suboptimal design, especially in the case of mini- and small-scale ORC systems, since the preselected combination of working fluid and operating conditions may lead to infeasible turbine designs. The resulting iterative design procedure may end in conservative solutions after multiple trial-and-error attempts due to the strong interdependence of the many design variables and constraints involved. In this work, we therefore present a new design and optimization method integrating working fluid selection, thermodynamic cycle design, and preliminary turbine design. To this purpose, our recent 1-stage continuous-molecular targeting (CoMT)-computer-aided molecular design (CAMD) method for the integrated design of the ORC process and working fluid is expanded by a turbine meanline design procedure. Thereby, the search space of the optimization is bounded to regions where the design of the turbine is feasible. The resulting method has been tested for the design of a small-scale high-temperature ORC unit adopting a radial-inflow turbo-expander. The results confirm the potential of the proposed method over the conventional iterative design practice for the design of small-scale ORC turbogenerators.

Assessment of Tesla Turbine Performance for Small Scale Solar Rankine Combined Heat and Power Systems

2009 ◽  
Author(s):  
Van P. Carey
Keyword(s):  
Power Systems ◽  
Residential Buildings ◽  
Rankine Cycle ◽  
Combined Heat And Power ◽  
Operating Conditions ◽  
Working Fluid ◽  
Small Scale ◽  
Manufacturing Cost ◽  
Turbine Design ◽  
The Impact

For solar Rankine cycle combined heat and power systems for residential buildings and other small-scale applications (producing 1–10 kWe), a low manufacturing cost, robust and durable expander is especially attractive. The Tesla turbine design has these desired features. This paper summarizes a theoretical exploration of the performance of a Tesla Turbine as the expander in a small-scale Rankine cycle combine heat and power system. A one-dimensional idealized model of momentum transfer in the turbine rotor is presented which can be used to predict the efficiency of the turbine for typical conditions in these systems. The model adopts a non-dimensional formulation that identifies the dimensionless parameters that dictate performance features of the turbine. The model is shown to agree well with experimental performance data obtained in earlier tests of prototype Tesla turbine units. The model is used to explore the performance of this type of turbine for Rankine cycle applications using water as a working fluid. The model indicates that isentropic efficiencies above 0.70 can be achieved if the operating conditions are tailored in an optimal way. The scalability of the turbine design, and the impact of the theoretical model predictions on development of solar combined heat and power systems are also discussed.

scholarly journals Component-Oriented Modeling of a Micro-Scale Organic Rankine Cycle System for Waste Heat Recovery Applications

2021 ◽  
Vol 11 (5) ◽  
pp. 1984
Author(s):  
Ramin Moradi ◽  
Emanuele Habib ◽  
Enrico Bocci ◽  
Luca Cioccolanti
Keyword(s):  
Electric Power ◽  
Heat Recovery ◽  
Waste Heat Recovery ◽  
Waste Heat ◽  
Organic Rankine Cycle ◽  
Rankine Cycle ◽  
Operating Conditions ◽  
Working Fluid ◽  
Pump Efficiency ◽  
Micro Scale

Organic Rankine cycle (ORC) systems are some of the most suitable technologies to produce electricity from low-temperature waste heat. In this study, a non-regenerative, micro-scale ORC system was tested in off-design conditions using R134a as the working fluid. The experimental data were then used to tune the semi-empirical models of the main components of the system. Eventually, the models were used in a component-oriented system solver to map the system electric performance at varying operating conditions. The analysis highlighted the non-negligible impact of the plunger pump on the system performance Indeed, the experimental results showed that the low pump efficiency in the investigated operating range can lead to negative net electric power in some working conditions. For most data points, the expander and the pump isentropic efficiencies are found in the approximate ranges of 35% to 55% and 17% to 34%, respectively. Furthermore, the maximum net electric power was about 200 W with a net electric efficiency of about 1.2%, thus also stressing the importance of a proper selection of the pump for waste heat recovery applications.

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