Experimental Investigation of a Small-Scale Orc Turbo-Generator Supported On Gas-Lubricated Bearings

2021 ◽  
Author(s):  
Kévin Rosset ◽  
Olivier Pajot ◽  
Jurg Schiffmann
Keyword(s):  
High Speed ◽  
Waste Heat ◽  
Electrical Power ◽  
Organic Rankine Cycle ◽  
Mechanical Efficiency ◽  
Load Level ◽  
Working Fluid ◽  
Small Scale ◽  
Electrical Machine ◽  
Turbo Generator

Abstract Waste heat recovery is expected to contribute to reducing CO2 emissions from trucks. Organic Rankine cycle (ORC) systems show the highest potential for this application, but still lack efficient small-scale expansion devices, in practice. A novel turbo-generator supported on gas-lubricated bearings is presented in this paper. The device combines a single-stage radial-inflow turbine and a permanent-magnet machine in a single rotating part supported on aerodynamic bearings, lubricated with the working fluid (R245fa). The oil-free expander was tested within a dedicated ORC test setup. It was driven up to its nominal speed of 100 kRPM, generated up to 2.3 kW of electrical power, and reached a peak overall efficiency of 67%. Although the prototype was not actively cooled, the mechanical losses of the rotor shaft and the iron loss of the electrical machine reached their nominal levels. Only the copper loss was at a part-load level. The electro-mechanical efficiency of the turbo-generator reached 91% and is expected to increase while testing the device at higher load. This proof of concept confirms the high-speed and low-loss potential of gas-lubricated bearings for small-scale dynamic expanders.

Dynamic Modelling of Small Scale and High Temperature ORC System Using Simulink and CoolProp

2020 ◽  
Author(s):  
Radheesh Dhanasegaran ◽  
Antti Uusitalo ◽  
Teemu Turunen-Saaresti
Keyword(s):  
High Temperature ◽  
Dynamic Model ◽  
High Speed ◽  
Waste Heat ◽  
Fluid Pressure ◽  
Dynamic Modelling ◽  
Working Fluid ◽  
Small Scale ◽  
Condensation Process ◽  
Feed Pump

Abstract In the present work, a dynamic model has been developed for the small-scale high-temperature ORC experimental test rig at the LUT University that utilizes waste heat from a heavy-duty diesel engine exhaust. The experimental facility consists of a high-speed Turbogenerator, heat exchanger components such as recuperator, condenser, and evaporator with a pre-feed pump to boost the working fluid pressure after the condensation process constituting a cycle. The turbogenerator consists of a supersonic radial-inflow turbine, a barske type main-feed pump, and a permanent magnet type generator components connected on a single shaft. Octamethyltrisiloxane (MDM) is the chosen organic working fluid in this cycle. Matlab-Simulink environment along with the open-source thermodynamic and transport database Cool-Prop has been chosen for calculating the thermodynamic properties of the dynamic model. A functional parameter approach has been followed for modeling each block component by predefined input and output parameters, aimed at modeling the performance characteristics with a limited number of inputs for both design and off-design operations of the cycle. The dynamic model is validated with the experimental data in addition to the investigation of exhaust gas mass flow regulation that establishes a control strategy for the dynamic model.

Experimental Characterization of Losses in Bladeless Turbine Prototype

2021 ◽  
Author(s):  
Avinash Renuke ◽  
Federico Reggio ◽  
Alberto Traverso ◽  
Matteo Pascenti
Keyword(s):  
High Speed ◽  
Electrical Power ◽  
Working Fluid ◽  
Small Scale ◽  
Experimental Characterization ◽  
Scaling Effects ◽  
Low Performance ◽  
Low Sensitivity ◽  
First Time

Abstract Multi-disk bladeless turbines, also known as Tesla turbines, are promising in the field of small-scale power generation and energy harvesting due to their low sensitivity to down-scaling effects, retaining high rotor efficiency. However, low (less than 40%) overall isentropic efficiency has been recorded in the experimental literature. This article aims for the first time to a systematic experimental characterization of loss mechanisms in a 3-kW Tesla expander using compressed air as working fluid and producing electrical power through a high speed generator (40krpm). The sources of losses discussed are: stator losses, stator-rotor peripheral viscous losses, end wall ventilation losses and leakage losses. After description of experimental prototype, methodology and assessment of measurement accuracy, the article discusses such losses aiming at separating the effects that each loss has on the overall performance. Once effects are separated, their individual impact on the overall efficiency curves is presented. This experimental investigation, for the first time, gives the insight into the actual reasons of low performance of Tesla turbines, highlighting critical areas of improvement, and paving the way to next generation Tesla turbines, competitive with state of the art bladed expanders.

Economic Feasibility Study of a Small Scale Organic Rankine Cycle System in Waste Heat Recovery Application

2010 ◽  
Author(s):  
Bertrand F. Tchanche ◽  
Sylvain Quoilin ◽  
Sebastien Declaye ◽  
Georges Papadakis ◽  
Vincent Lemort
Keyword(s):  
Thermodynamic Model ◽  
Heat Recovery ◽  
Waste Heat Recovery ◽  
Waste Heat ◽  
Organic Rankine Cycle ◽  
Rankine Cycle ◽  
Payback Period ◽  
Working Fluid ◽  
Small Scale ◽  
Electricity Cost

The Organic Rankine Cycle (ORC) appears progressively as a promising solution to recover waste heat energy from thermal processes for electricity generation. A prototype of small-scale ORC has been built and successfully tested at the University of Lie`ge. It uses R-245fa and R-123 as working fluid, and an oil-free scroll compressor adapted to run in expander mode. Thermodynamic model of the system was derived and validated for performance prediction. The validated thermodynamic model is used to optimize the operation of the small ORC in waste heat recovery application (ORC-WHR). For exhaust gases at 180 °C and a mass flow rate of 0.21 kg/s, a maximum net power output of 2 kWe is obtained for an evaporator pressure of 11.84 bar. The cycle thermal efficiency is 8.23 and the recuperation efficiency, 66.32%. Based on the aforementioned conditions, the economic assessment of small scale ORC-WHR was carried out using economic criteria such as levelized electricity cost (LEC), Net present value (NPV) and depreciated payback period (DPP). For a 2kWe ORC-WHR, the specific installed cost is 5775 €/kW with a LEC of 13.27 c€/kWh while for a 50 kWe, the specific installed cost is about 3034 €/kW and the LEC, 7c€/kWh. For an electricity unit price of 20 c€/kWh, the payback period of a 2 kWe system is 6 years while it is 2.5 years for a 50 kWe system. It is concluded from the study that recovering the waste heat by way of ORCs is technically and economically feasible. As recycled energy, waste heat has the same advantages as renewable energy and should benefit from the same legislative conditions (Feed-in-Laws).

Design and Flow Analysis of a Supersonic Small Scale ORC Turbine Stator With High Molecular Complexity Working Fluid

2014 ◽  
Author(s):  
Antti Uusitalo ◽  
Teemu Turunen-Saaresti ◽  
Alberto Guardone ◽  
Aki Grönman
Keyword(s):  
High Efficiency ◽  
Waste Heat ◽  
Flow Analysis ◽  
Organic Rankine Cycle ◽  
Working Fluid ◽  
Small Scale ◽  
Low Grade ◽  
Real Gas ◽  
Turbine Stator ◽  
Molecular Complexity

In small scale and low temperature waste heat recovery systems, Organic Rankine Cycle (ORC) technology can be identified as a promising solution in converting low-grade heat into electricity. The principle of ORC is based on a conventional Rankine process but an organic working fluid is adopted instead of steam. The use of high molecular complexity working fluids enables the design of high efficiency ORCs and are characterized by dry expansion and high pressure ratios over the turbine, as well as low speed of sound, which typically leads to highly supersonic flows in the ORC turbine stator. In order to design supersonic ORC turbines, the geometry of the turbine stator has to be based on design methods that accurately take into account the real gas effects of the working fluid during the expansion. In this study, a highly supersonic small scale ORC turbine stator using siloxane MDM as working fluid, is studied. The accurate real gas model was implemented in a CFD-flow solver in order to predict the flow field in the stator in design and in off-design conditions. The results of this study gives valuable information on realising small capacity ORC turbomachinery, characterized by highly supersonic stators, and on the off-design performance of supersonic radial turbine stator that has not been documented or discussed in the previous studies.

scholarly journals Analysis of the Issue of Recovery of Low-Potential Energy at Small-Scale Energy Facilities

2021 ◽  
Vol 19 (2) ◽  
pp. 100-106
Author(s):  
A. V. Dmitrenko ◽  
M. I. Kolpakov
Keyword(s):  
Heat Exchange ◽  
Potential Energy ◽  
Power Plants ◽  
Waste Heat ◽  
Organic Rankine Cycle ◽  
Hot Water ◽  
Working Fluid ◽  
Small Scale ◽  
Working Fluids ◽  
Heat Exchange Equipment

Studying the issues of recovery of low-potential energy at smallscale energy facilities allowed to show the promising character of the organic Rankine cycle (ORC) technology as a technology for recovery or conversion of low-potential energy.The most promising developments in the field of the use and recovery of waste heat are described regarding application of ORC, which is widely used in geothermal sources, hot water boilers, gas turbine plants. Due to the constantly growing diversity of working fluids, ORC can be used within a wide temperature range from 100°C to over 350°C. Also, developments are underway in the design of ORC generators to increase reliability of its individual system units, such as turbines and expanders. Based on the above factors, it can be concluded that with a deeper study of the problems of adopting ORC technologies, they can become a very promising direction in development of heat power engineering.It has been determined that the main factor hindering the widespread adoption of the ORC technology is associated with high cost of heat exchange equipment due to increased heat exchange surfaces. It is shown that design of mini power plants and energy centres based on the use of low-potential energy requires improvement of mathematical modelling methods to reliably determine operating modes and characteristics of each of the units. Methods for modelling evaporation and condensation systems, including turbines and expanders using organic low-boiling working fluids, should be considered among the methods that are highly sought after. The methods for selecting a working fluid for ORC devices also have a significant impact on characteristics of the installation determining the range of cycle operating temperatures and pressures. The solution of the above problems can lead to a reduction in the cost of heat exchange equipment, and, consequently, to a decrease in costs for design of ORC generators. 

scholarly journals A world overview of organic Rankine cycle as waste heat recovery alternative

Respuestas ◽  
2019 ◽  
Vol 24 (3) ◽  
pp. 6-13
Author(s):  
Guillermo Eliecer Valencia Ochoa ◽  
Aldair Enrique Benavides Gamero ◽  
Josué Miguel Camargo Vanegas
Keyword(s):  
Heat Recovery ◽  
Waste Heat Recovery ◽  
Waste Heat ◽  
Electrical Power ◽  
Organic Rankine Cycle ◽  
Rankine Cycle ◽  
Working Fluid ◽  
Gas Engine ◽  
Natural Gas Engine ◽  
Organic Fluids

In this work the advantage of the use and implementation of ORC heat recovery systems for low temperature (<230°C) exhaust gases from a natural gas engine was studied. Different organic fluids and working conditions were analyzed in order to determine the best decision in terms of energy efficiency and exergética refers to criteria such as cost, environmental impact, flammability toxicity among others. It was found that the performance for the different configurations is closely linked to the evaporation pressure, reaching an electrical power of 120kWe (10%) for the simple configuration. The working fluid with the highest performance was acetone regardless of the configuration analyzed. Simultaneously, an international and national context was created in different fields for heat recovery systems.

scholarly journals Design and CFD Analysis of a Radial-Inflow Turbine for Small Scale ORC Applications

2020 ◽  
Vol 197 ◽  
pp. 11005
Author(s):  
Alessandro Cappiello ◽  
Raffaele Tuccillo
Keyword(s):  
Waste Heat ◽  
Three Dimensional ◽  
Organic Rankine Cycle ◽  
Industrial Process ◽  
Rankine Cycle ◽  
Energy Conversion Efficiency ◽  
Working Fluid ◽  
Energy Sources ◽  
Small Scale ◽  
Line Design

In recent years, Organic Rankine Cycle (ORC) technology has received growing interests, thanks to its high flexibility and to the capability to exploit energy sources at temperature levels difficult to be approached with conventional power cycles. These features allow exploiting renewable and renewable-equivalent energy sources, by either improving the energy conversion efficiency of existing plants or using waste heat from industrial process. As far as the expander is concerned, a high potential solution is represented by turbo-expanders, which allow reduction of plant clutter and complexity, so enhancing the potential impact on the diffusion of small power ORC-based plants. The present work concerns the design of a RadialInflow Turbine for a bottoming Organic Rankine Cycle in the tens of kW scale. Design boundary conditions are retrieved by a zero-dimensional model of a solar-assisted micro gas turbine in cogenerating mode. The design process is started by means of an in-house mean-line design code accounting for real gas properties. The code is used to carry out parametric analyses to investigate the design space for several working fluids encompassing different classes, namely refrigerants and siloxanes. The program is used to assess the effect of design variables and working fluid on the turbine performance and turbine design characteristics. Subsequently, the most promising design candidates are selected and three-dimensional first guess stator and rotor geometries are built on these preliminary designs. Stationary and rotating passages are then meshed and analyzed by means of RANS CFD based solution of the stator – rotor interaction.

scholarly journals 3D CFD Analysis of an Oil Injected Twin Screw Expander

2013 ◽  
Author(s):  
I. Papes ◽  
J. Degroote ◽  
J. Vierendeels
Keyword(s):  
Waste Heat ◽  
Organic Rankine Cycle ◽  
Simulation Models ◽  
Rankine Cycle ◽  
Working Fluid ◽  
Small Scale ◽  
Multiphase Model ◽  
Flow Process ◽  
Twin Screw ◽  
Oil Injection

Small scale Organic Rankine Cycle (ORC) systems have a big potential for waste heat recovery in the market. Due to the smaller volume flows inside these systems, non-conventional expansion technologies such as screw expanders become more interesting. Recent economic studies have shown the important role of screw machines in such cycles. However, in order to get a better understanding of the expansion behaviour in an ORC, appropriate simulation models of screw expanders are necessary. The flow inside an oil-injected twin screw expander is modeled in detail with 3D CFD (Computational Fluid Dynamics) calculations. These simulations are challenging because of the deforming domain and the narrow gaps between the screws or between a screw and the casing. The deforming mesh motion is handled by an in-house code which generates a block-structured grid with the help of the solutions of the Laplace problem. The oil-phase was modeled with an Eulerian multiphase model and the working fluid is treated compressible. The performance of the screw expander is strongly affected by the oil-injection which provides lubrication and a better sealing of the gaps. Therefore, the different types of leakages inside the screw expander are studied and monitored. As the result of the simulations, knowledge about the flow process and the losses inside the oil-injected screw expander is built up.

scholarly journals Working fluid selection for a small-scale organic Rankine cycle recovering engine waste heat

2017 ◽  
Vol 123 ◽  
pp. 346-352 ◽  
Author(s):  
Yiji Lu ◽  
Anthony Paul Roskilly ◽  
Long Jiang ◽  
Xiaoli Yu
Keyword(s):  
Waste Heat ◽  
Organic Rankine Cycle ◽  
Rankine Cycle ◽  
Working Fluid ◽  
Small Scale ◽  
Working Fluid Selection ◽  
Selection For

Experimental Characterization of Losses in Bladeless Turbine Prototype

2021 ◽  
Author(s):  
Avinash Renuke ◽  
Federico Reggio ◽  
Alberto Traverso ◽  
Matteo Pascenti
Keyword(s):  
High Speed ◽  
Electrical Power ◽  
Working Fluid ◽  
Small Scale ◽  
Experimental Characterization ◽  
Scaling Effects ◽  
Low Performance ◽  
Low Sensitivity ◽  
First Time

Abstract Multi-disk bladeless turbines, also known as Tesla turbines, are promising in the field of small-scale power generation and energy harvesting due to their low sensitivity to down-scaling effects, retaining high rotor efficiency. However, low (less than 40%) overall isentropic efficiency has been recorded in the experimental literature. This article aims for the first time to a systematic experimental characterization of loss mechanisms in a 3-kW Tesla expander using compressed air as working fluid and producing electrical power through a high speed generator (40krpm). The sources of losses discussed are: stator losses, stator-rotor peripheral viscous losses, end wall ventilation losses and leakage losses. After description of experimental prototype, methodology and assessment of measurement accuracy, the article discusses such losses aiming at separating the effects that each loss has on the overall performance. Once effects are separated, their individual impact on the overall efficiency curves is presented. This experimental investigation, for the first time, gives the insight into the actual reasons of low performance of Tesla turbines, highlighting critical areas of improvement, and paving the way to next generation Tesla turbines, competitive with state of the art bladed expanders.

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