The Experts below are selected from a list of 45288 Experts worldwide ranked by ideXlab platform
Mohsen Saadat - One of the best experts on this subject based on the ideXlab platform.
-
an approach to reduce the flow requirement for a liquid piston near isothermal air compressor expander in a compressed air energy storage system
Iet Renewable Power Generation, 2016Co-Authors: Mohsen SaadatAbstract:A compressed air energy storage system that uses a high pressure, isothermal air compressor/expander (C/E) has no carbon emission and is more efficient than a conventional system that uses fossil fuels. To be successful, the compressor/expander must be efficient and has high power density. However, there is a trade-off between efficiency and power density due to heat transfer. The authors’ previous work has shown that by optimising the compression/expansion trajectories in a liquid piston C/E, the power density can be improved by many times without sacrificing efficiency. Yet, to achieve the optimised trajectory, this requires a large liquid piston pump/motor that often operates at low displacement, low efficiency regime. This study proposes that by combining the liquid piston with a solid piston actuated via a hydraulic intensifier, the pump/motor size can be reduced significantly. A case study shows that with an optimal intensifier ratio, the pump/motor size is reduced by 85%, the ratio between maximum and minimum displacements is reduced by 7 times, and the mean efficiency is increased by 2.4 times. A full cycle dynamic simulation shows that the intensifier decreases, for the same pump/motor size, the total cycle time for over 50%, thus doubling the power density of the compressor/expander.
-
combined optimal design and control of a near isothermal liquid piston air compressor expander for a compressed air energy storage caes system for wind turbines
Human-Robot Interaction, 2015Co-Authors: Mohsen Saadat, Perry Y LiAbstract:The key component of Compressed Air Energy Storage (CAES) system is an air compressor/expander. The roundtrip efficiency of this energy storage technology depends greatly on the efficiency of the air compressor/expander. There is a trade off between the thermal efficiency and power density of this component. Different ideas and approaches were introduced and studied in the previous works to improve this trade off by enhancing the heat transfer between air and its environment. In the present work, a combination of optimal compression/expansion rate, optimal chamber shape and optimal heat exchanger material distribution in the chamber is considered to maximize the power density of a compression/expansion chamber for a given desired efficiency. Results show that the power density can be improved by more than 20 folds if the optimal combination of flow rate, shape and porosity are used together.Copyright © 2015 by ASME
-
DRAFT: NONLINEAR CONTROLLER DESIGN WITH BANDWIDTH CONSIDERATION FOR A NOVEL COMPRESSED AIR ENERGY STORAGE SYSTEM
2015Co-Authors: Mohsen Saadat, Farzad A ShiraziAbstract:To achieve both accumulator pressure regulation and gen-erator power tracking for a Compressed Air Energy Storage (CAES) system, a nonlinear controller designed base on an en-ergy based Lyapunov function. The control inputs for the storage system are the pump/motor displacements inside the hydraulic transformer and the liquid piston air compressor/expander. While the pump/motor inside the liquid piston has a low band-width, the other pump/motor inside the hydraulic transformer has a relatively higher bandwidth. On the other hand, the pneu-matic energy storage path of open accumulator has high en-ergy density, whereas the hydraulic path is more power dense. The nonlinear controller is then modified based on these proper-ties. In the proposed approach, the control effort is distributed between the two pump/motors based on their bandwidths: Hy-draulic transformer reacts to high frequency events, while the liquid piston air compressor/expander perform a steady stor-age/regeneration task. As the result, liquid piston air compres-sor/expander will loosely maintain the accumulator pressure ra-tio, while the pump/motor in hydraulic transformer precisely tracks the desired generator power. This control scheme also allows the accumulator to function as a damper for the storage system by absorbing power disturbances from the hydraulic path generated due to wind gusts
-
optimal trajectories for a liquid piston compressor expander in a compressed air energy storage system with consideration of heat transfer and friction
Advances in Computing and Communications, 2012Co-Authors: Mohsen Saadat, Terry SimonAbstract:For a Compressed Air Energy Storage (CAES) approach to be viable, the air compressor/expander must be sufficiently powerful and efficient. Since efficiency is governed by heat transfer, there is a generally a tradeoff between efficiency and compression/expansion time (or power). In this paper, we determine Pareto optimal compression/expansion profiles for a liquid piston air compressor/expander that maximizes efficiency (power) for a given power (efficiency). Compared to previous works, a numerical optimization approach is proposed that allows for more general heat transfer model, the consideration of the viscous friction, and system limitations in the optimization. The resulting optimal profiles are compared to other trajectories. At compression ratio of 10, the optimal profile results in 10%–40% increase in power density relative to other methods. Optimal geometries that trades off friction and heat transfer improvement can also be determined using this method.
Vincent Lemort - One of the best experts on this subject based on the ideXlab platform.
-
PDSim: A general quasi-steady modeling approach for positive displacement compressors and expanders
International Journal of Refrigeration, 2020Co-Authors: Ian H. Bell, Davide Ziviani, Vincent Lemort, Craig R. Bradshaw, Margaret Mathison, W. Travis Horton, James E. Braun, Eckhard A. GrollAbstract:Abstract A novel generalized framework is presented that can be used to simulate the quasi-steady-state performance of a wide range of positive displacement compressors and expanders (scroll, piston, screw, rotary, spool, etc.). The complete simulation algorithm is described, and an emphasis is placed on the numerical methods required to obtain robust behavior of the simulation. This formulation has been implemented into an open-source software package entitled PDSim written in the Python language. PDSim is the first open-source generalized compressor and expander simulation package and the complete source code is included in the Supplemental material. A piston expander is used as an example of the utilization of this framework. The framework has been applied to several positive displacement machines in the companion paper in order to demonstrate the flexibility of the approach (Ziviani et al., 2019).
-
Experimental and Numerical Investigation of a Roots Expander Integrated into an ORC Power System
'Purdue University (bepress)', 2018Co-Authors: Parthoens Antoine, Guillaume Ludovic, Dumont Olivier, Vincent LemortAbstract:The performance of internal combustion engines can be improved by valorising the waste heat by means of organic Rankine Cycle power systems (ORC). This paper focuses on an expander of a truck-embedded ORC system. The considered expander is a roots machine. The roots machine is a volumetric machine characterized by a theoretical internal volume ratio of 1. It is typically used as compressor under low pressure ratios (for instance, engine supercharging or air “blowers”). First, a test rig has been built to perform several tests on the volumetric machine. It is an ORC power system with a typical architecture using R245fa as working fluid (and 5% in mass oil fraction), heated oil as heat source and tap water as heat sink. Maps presenting produced powers, filling factors and isentropic efficiencies versus on one side the pressure ratio (from 1.2 to 4.5) and on the other side the shaft rotational speed (from 1000 to 11000 RPM) are investigated. The maximal delivered power is slightly above 3 kW. Concerning the filling factor the range is between 0.85 and 2.75 and the isentropic efficiency reaches a maximum about 50%. Wet expansions are envisaged leading to a deterioration of the performance. From the experimental data, a semi-empirical model is calibrated. This model is able to extrapolate the performance outside the experimental operating conditions and identify the different loss sources. Moreover, effects of overheat level and lubricating oil are also envisaged. The actual tested machine does not have an internal volumetric ratio strictly equal to 1 but is slightly larger. Such volumetric ratio implies that best efficiencies are achieved under small pressure ratios. However, these limited pressure ratios do not lead to large produced powers. To tackle this issue, simulations based on the calibrated model are driven for two expanders in series. This allows to increase the global internal volumetric ratio and shift the best performance towards higher pressure ratios. To enhance either the efficiency or the output power, the intermediate pressure (i.e. the pressure between the two expanders in series) is numerically optimized
-
experimental study on an open drive scroll expander integrated into an orc organic rankine cycle system with r245fa as working fluid
Energy, 2013Co-Authors: Sebastien Declaye, Sylvain Quoilin, Ludovic Guillaume, Vincent LemortAbstract:Abstract The present paper focuses on the experimental characterization of an open-drive scroll expander integrated into an Organic Rankine cycle using R245fa as working fluid. The expander is a commercially available air compressor that was modified to operate in expander mode. The ORC (Organic Rankine Cycle) system is designed for a nominal heat input of 20 kW and a nominal net power output of 1.8 kW. A total of 74 steady-state operating points are measured to evaluate the expander performance over a wide range of conditions. The operating parameters that are varied include the inlet pressure (from 9 to 12 bar), outlet pressure (from 1.5 to 4 bar) and rotational speed (from 2000 to 3500 rpm). The maximum isentropic efficiency and shaft power are, respectively, 75.7% and 2.1 kW. A maximum cycle efficiency of 8.5% is reached for evaporating and condensing temperatures of 97.5 °C and 26.6 °C respectively. For most of the tests, hot water is produced in the condenser and the system therefore behaves as a CHP (combined heat and power). Depending on the water temperature requirement, a power to heat ratio varying between 1.9% and 11.8% is obtained. Water over 50 °C can be produced with a power to heat ratio higher than 8%. The experimental data points are then used to generate a performance map of the expander. This performance map allows for simulation of the use of such an expander in other ORC system.
-
Development of a generalized steady-state simulation framework for positive displacement compressors and expanders
8th International Conference on Compressors and their Systems, 2013Co-Authors: Ian H. Bell, Vincent Lemort, James E. Braun, Eckhard A. Groll, W. Travis HortonAbstract:In this paper, a generalized framework is presented that can be used to simulate the steady-state performance of a wide range of positive displacement compressors and expanders (scroll, piston, screw, rotary, spool, etc.). The complete simulation algorithm is described, and an emphasis is placed on the numerical methods required to obtain robust behavior of the simulation. This formulation has been implemented into an open-source software package entitled PDSim written in the Python language. PDSim is the first open-source generalized compressor and expander simulation package. The source code can be freely obtained on the internet.
-
liquid flooded compression and expansion in scroll machines part ii experimental testing and model validation
International Journal of Refrigeration-revue Internationale Du Froid, 2012Co-Authors: Ian H. Bell, Vincent Lemort, James E. Braun, Eckhard A. Groll, Galen B King, Travis W HortonAbstract:Abstract The use of liquid-flooding in the compression and expansion of non-condensable gas in scroll compressors and expanders enables the possibility of quasi-isothermal working processes. Liquid-flooded scroll machines were installed in a fully-instrumented Liquid-Flooded Ericsson Cycle test rig to conduct entire cycle performance tests. In addition, detailed compressor and expander performance data was obtained. Oil mass fractions of up to 92% and 76% were added to the gas entering the scroll compressor and expander respectively. The overall isentropic efficiency of the scroll compressor based on the shaft power with flooding was up to 73% and the volumetric efficiency was above 92%. For the expander, the best overall isentropic and volumetric efficiencies achieved were 66% and 105% respectively. The mechanistic model presented in the companion paper was validated against the experimental data for both the compressor and the scroll expander with good agreement, though the agreement is better for the scroll compressor.
Ian H. Bell - One of the best experts on this subject based on the ideXlab platform.
-
PDSim: A general quasi-steady modeling approach for positive displacement compressors and expanders
International Journal of Refrigeration, 2020Co-Authors: Ian H. Bell, Davide Ziviani, Vincent Lemort, Craig R. Bradshaw, Margaret Mathison, W. Travis Horton, James E. Braun, Eckhard A. GrollAbstract:Abstract A novel generalized framework is presented that can be used to simulate the quasi-steady-state performance of a wide range of positive displacement compressors and expanders (scroll, piston, screw, rotary, spool, etc.). The complete simulation algorithm is described, and an emphasis is placed on the numerical methods required to obtain robust behavior of the simulation. This formulation has been implemented into an open-source software package entitled PDSim written in the Python language. PDSim is the first open-source generalized compressor and expander simulation package and the complete source code is included in the Supplemental material. A piston expander is used as an example of the utilization of this framework. The framework has been applied to several positive displacement machines in the companion paper in order to demonstrate the flexibility of the approach (Ziviani et al., 2019).
-
a computationally efficient hybrid leakage model for positive displacement compressors and expanders
International Journal of Refrigeration-revue Internationale Du Froid, 2013Co-Authors: Ian H. Bell, James E. Braun, Eckhard A. Groll, Travis W HortonAbstract:An empirical frictional correction factor to the isentropic nozzle model has been developed for application to refrigerant leakage modeling in scroll, rotary and other similar compressors and expanders. This correction factor is derived by calculating the leakage mass flow rate with a compressible, variable area, real gas properties model and referencing the results to an isentropic nozzle model. The ratio of flows is correlated to the Reynolds number, a characteristic length and the leakage gap width. A representative selection of fluids and geometries are employed. For all the correlations, at least 93% of the points are predicted within an absolute error band of 20%.
-
Development of a generalized steady-state simulation framework for positive displacement compressors and expanders
8th International Conference on Compressors and their Systems, 2013Co-Authors: Ian H. Bell, Vincent Lemort, James E. Braun, Eckhard A. Groll, W. Travis HortonAbstract:In this paper, a generalized framework is presented that can be used to simulate the steady-state performance of a wide range of positive displacement compressors and expanders (scroll, piston, screw, rotary, spool, etc.). The complete simulation algorithm is described, and an emphasis is placed on the numerical methods required to obtain robust behavior of the simulation. This formulation has been implemented into an open-source software package entitled PDSim written in the Python language. PDSim is the first open-source generalized compressor and expander simulation package. The source code can be freely obtained on the internet.
-
liquid flooded compression and expansion in scroll machines part ii experimental testing and model validation
International Journal of Refrigeration-revue Internationale Du Froid, 2012Co-Authors: Ian H. Bell, Vincent Lemort, James E. Braun, Eckhard A. Groll, Galen B King, Travis W HortonAbstract:Abstract The use of liquid-flooding in the compression and expansion of non-condensable gas in scroll compressors and expanders enables the possibility of quasi-isothermal working processes. Liquid-flooded scroll machines were installed in a fully-instrumented Liquid-Flooded Ericsson Cycle test rig to conduct entire cycle performance tests. In addition, detailed compressor and expander performance data was obtained. Oil mass fractions of up to 92% and 76% were added to the gas entering the scroll compressor and expander respectively. The overall isentropic efficiency of the scroll compressor based on the shaft power with flooding was up to 73% and the volumetric efficiency was above 92%. For the expander, the best overall isentropic and volumetric efficiencies achieved were 66% and 105% respectively. The mechanistic model presented in the companion paper was validated against the experimental data for both the compressor and the scroll expander with good agreement, though the agreement is better for the scroll compressor.
Rodolfo Taccani - One of the best experts on this subject based on the ideXlab platform.
-
bottoming organic rankine cycle for a small scale gas turbine a comparison of different solutions
Applied Energy, 2013Co-Authors: Stefano Clemente, Diego Micheli, Mauro Reini, Rodolfo TaccaniAbstract:Recently, several efforts have been devoted to the improvement of the thermal efficiency of small gas turbines, in order to approach the typical values of the internal combustion engines in the same range of power. One possibility is represented by a combined cycle, obtained coupling the gas turbine to a bottoming organic Rankine cycle (ORC). This paper deals with the definition of the main features of an ORC system aimed to recover heat from a 100kWe commercial gas turbine with internal recuperator. After the optimization of the thermodynamic cycles, involving a comparison between six working fluids, different expanders are analyzed, with the aim of detecting, if possible, the best suited machine. First, single stage turbines, in both radial and axial flow configuration, are designed specifically for each considered fluid, in particular investigating the opportunity of mounting the ORC expander directly on the high-speed shaft of the gas turbine. Then, the performances of these dynamic machines are compared with those of positive displacement expanders, such as scroll devices, obtainable from commercial HVAC compressor with minor revisions, and reciprocating ones, here newly designed.
-
energy efficiency analysis of organic rankine cycles with scroll expanders for cogenerative applications
Applied Energy, 2012Co-Authors: Stefano Clemente, Diego Micheli, Mauro Reini, Rodolfo TaccaniAbstract:Abstract Small scale Organic Rankine Cycle (ORC) systems has been the object of a large number of studies in the last decade, because of their suitability for energy recovery and cogenerative applications. The paper presents an ORC numerical model and its applications to two different case studies; the code has been obtained by combining a one-dimensional model of a scroll machine and a thermodynamic model of a whole ORC system. Series production components, such as scroll compressors, from HVAC field, have been first considered in order to reduce costs, because this is a critical issue for small scale energy recovery and cogeneration systems. The detailed model of the scroll machine is capable to calculate the performances of both a compressor and an expander, as function of the geometry of the device and of the working fluid. The model has been first tested and validated by comparing its outputs with experimental tests on a commercial scroll compressor, then used to calculate the working curves of commercial scroll machines originally designed as compressors in the HVAC field, but operating as expanders. The model of the expander has been then integrated in the thermodynamic model of the ORC system. A series of comparisons have been carried out in order to evaluate how the performances are influenced by cycle parameters, scroll geometry and working fluid for different applications. The results confirm the feasibility of small scale CHP systems with acceptable electrical efficiency, taking into account the low-temperature thermal source, the small power output and the low-cost series production components employed.
Eckhard A. Groll - One of the best experts on this subject based on the ideXlab platform.
-
PDSim: A general quasi-steady modeling approach for positive displacement compressors and expanders
International Journal of Refrigeration, 2020Co-Authors: Ian H. Bell, Davide Ziviani, Vincent Lemort, Craig R. Bradshaw, Margaret Mathison, W. Travis Horton, James E. Braun, Eckhard A. GrollAbstract:Abstract A novel generalized framework is presented that can be used to simulate the quasi-steady-state performance of a wide range of positive displacement compressors and expanders (scroll, piston, screw, rotary, spool, etc.). The complete simulation algorithm is described, and an emphasis is placed on the numerical methods required to obtain robust behavior of the simulation. This formulation has been implemented into an open-source software package entitled PDSim written in the Python language. PDSim is the first open-source generalized compressor and expander simulation package and the complete source code is included in the Supplemental material. A piston expander is used as an example of the utilization of this framework. The framework has been applied to several positive displacement machines in the companion paper in order to demonstrate the flexibility of the approach (Ziviani et al., 2019).
-
a computationally efficient hybrid leakage model for positive displacement compressors and expanders
International Journal of Refrigeration-revue Internationale Du Froid, 2013Co-Authors: Ian H. Bell, James E. Braun, Eckhard A. Groll, Travis W HortonAbstract:An empirical frictional correction factor to the isentropic nozzle model has been developed for application to refrigerant leakage modeling in scroll, rotary and other similar compressors and expanders. This correction factor is derived by calculating the leakage mass flow rate with a compressible, variable area, real gas properties model and referencing the results to an isentropic nozzle model. The ratio of flows is correlated to the Reynolds number, a characteristic length and the leakage gap width. A representative selection of fluids and geometries are employed. For all the correlations, at least 93% of the points are predicted within an absolute error band of 20%.
-
Development of a generalized steady-state simulation framework for positive displacement compressors and expanders
8th International Conference on Compressors and their Systems, 2013Co-Authors: Ian H. Bell, Vincent Lemort, James E. Braun, Eckhard A. Groll, W. Travis HortonAbstract:In this paper, a generalized framework is presented that can be used to simulate the steady-state performance of a wide range of positive displacement compressors and expanders (scroll, piston, screw, rotary, spool, etc.). The complete simulation algorithm is described, and an emphasis is placed on the numerical methods required to obtain robust behavior of the simulation. This formulation has been implemented into an open-source software package entitled PDSim written in the Python language. PDSim is the first open-source generalized compressor and expander simulation package. The source code can be freely obtained on the internet.
-
liquid flooded compression and expansion in scroll machines part ii experimental testing and model validation
International Journal of Refrigeration-revue Internationale Du Froid, 2012Co-Authors: Ian H. Bell, Vincent Lemort, James E. Braun, Eckhard A. Groll, Galen B King, Travis W HortonAbstract:Abstract The use of liquid-flooding in the compression and expansion of non-condensable gas in scroll compressors and expanders enables the possibility of quasi-isothermal working processes. Liquid-flooded scroll machines were installed in a fully-instrumented Liquid-Flooded Ericsson Cycle test rig to conduct entire cycle performance tests. In addition, detailed compressor and expander performance data was obtained. Oil mass fractions of up to 92% and 76% were added to the gas entering the scroll compressor and expander respectively. The overall isentropic efficiency of the scroll compressor based on the shaft power with flooding was up to 73% and the volumetric efficiency was above 92%. For the expander, the best overall isentropic and volumetric efficiencies achieved were 66% and 105% respectively. The mechanistic model presented in the companion paper was validated against the experimental data for both the compressor and the scroll expander with good agreement, though the agreement is better for the scroll compressor.
