farzad shirazi | University of Houston (original) (raw)
Papers by farzad shirazi
... As explained before, the vibration signature over the test period is saved along with the cor... more ... As explained before, the vibration signature over the test period is saved along with the corresponding tacho signal. Using the tacho pulses, the engine vibration signal is split into the pieces corresponding to pairs of crankshaft revolutions. ... [6] Antonino-Daviu J., Riera-Guasp M ...
2014 American Control Conference, 2014
ABSTRACT
Asian Journal of Research in Banking and Finance, 2014
Volume 2: Heat Transfer Enhancement for Practical Applications; Heat and Mass Transfer in Fire and Combustion; Heat Transfer in Multiphase Systems; Heat and Mass Transfer in Biotechnology, 2013
An efficient and sufficiently power dense air compressor/expander is the key element in a Compres... more An efficient and sufficiently power dense air compressor/expander is the key element in a Compressed Air Energy Storage (CAES) approach. Efficiency can be increased by improving the heat transfer between air and its surrounding materials. One effective and practical method to achieve this goal is to use water droplets spray inside the chamber when air is compressing or expanding. In this paper, the air compression cycle is modeled by considering one-dimensional droplet properties in a lumped air model. While it is possible to inject water droplets into the compressing air at any time, optimal spray profile can result in maximum efficiency improvement for a given water to air mass ratio. The corresponding optimization problem is then defined based on the stored energy in the compressed air and the required input works. Finally, optimal spray profile has been determined for various water to air mass ratio using a general numerical approach to solve the optimization problem. Results show the potential improvement by acquiring the optimal spray profile instead of conventional constant spray flow rate. For the specific compression chamber geometry and desired pressure ratio and final time used in this work, the efficiency can be improved up to 4%.
Proceedings of the 2011 American Control Conference, 2011
ABSTRACT
Volume 2: Heat Transfer Enhancement for Practical Applications; Heat and Mass Transfer in Fire and Combustion; Heat Transfer in Multiphase Systems; Heat and Mass Transfer in Biotechnology, 2013
In the Compressed Air Energy Storage (CAES) approach, air is compressed to high pressure, stored,... more In the Compressed Air Energy Storage (CAES) approach, air is compressed to high pressure, stored, and expanded to output work when needed. The temperature of air tends to rise during compression, and the rise in the air internal energy is wasted during the later storage period as the compressed air cools back to ambient temperature. The present study focuses on designing an interrupted-plate heat exchanger used in a liquid-piston compression chamber for CAES. The exchanger features layers of thin plates stacked in an interrupted pattern. Twenty-seven exchangers featuring different combinations of shape parameters are analyzed. The exchangers are modeled as porous media. As such, for each exchanger shape, a Representative Elementary Volume (REV), which represents a unit cell of the exchanger, is developed. The flow through the REV is simulated with periodic velocity and thermal boundary conditions, using the commercial CFD software ANSYS FLUENT. Simulations of the REVs for the various exchangers characterize the various shape parameter effects on values of pressure drop and heat transfer coefficient between solid surfaces and fluid. For an experimental validation of the numerical solution, two different exchanger models made by rapid prototyping, are tested for pressure drop and heat transfer. Good agreement is found between numerical and experimental results. Nusselt number vs. Reynolds number relations are developed on the basis of pore size and on hydraulic diameter. To analyze performance of exchangers with different shapes, a simplified zero-dimensional thermodynamic model for the compression chamber with the inserted heat exchange elements is developed. This model, valuable for system optimization and control simulations, is a set of ordinary differential equations. They are solved numerically for each exchanger insert shape to determine the geometries of best compression efficiency.
2013 American Control Conference, 2013
The power density and efficiency of high compression ratio (∼200:1) air compressors/expanders are... more The power density and efficiency of high compression ratio (∼200:1) air compressors/expanders are crucial for the economical viability of a Compressed Air Energy Storage (CAES) system such as the one proposed in [1]. There is a trade-off between power density and efficiency that is strongly dependent on the heat transfer capability within compressor/expander. In previous papers, we have shown that the compression or expansion trajectory can be optimized so that for a given power, the efficiency can be optimized and vice versa. Theoretically, for high compression ratios, the improvement over ad-hoc trajectories can be significant-for example, at the same efficiency of 90%, the power can be increased by 3-5 folds [2], [3], [4], [5]. Yet, the optimal trajectories depend on the heat transfer coefficient profile that is often unknown. In this paper, we focus on the experimental study of an iterative control algorithm to track a compression trajectory that optimizes the efficiency-power trade-off in a liquid piston air compressor. First, an adaptive controller is developed to track any desired compression trajectory characterized by the temperature-volume profile. The controller adaptively estimates the unknown heat transfer coefficient. Second, the estimated heat transfer coefficient from one iteration is then used to estimate the optimal compression trajectory for the next iteration. As the estimate of the heat transfer coefficient improves from one iteration to the next, the quality of the estimated optimal trajectory also improves. This leads to successively improved efficiency. The experimental results of optimal trajectories show up to 2% improvement in compression efficiency compared to linear trajectories in a same power density.
ASME 2009 Dynamic Systems and Control Conference, Volume 2, 2009
The present paper employs a linear parameter-varying (LPV) control design approach with H perform... more The present paper employs a linear parameter-varying (LPV) control design approach with H performance specification for set-point tracking of deflection in an electrostatic MEMS actuator. First, we model the system dynamics in an LPV framework, considering the ...
Volume 8B: Heat Transfer and Thermal Engineering, 2013
The present study presents CFD simulations of a liquid-piston compressor with metal foam inserts.... more The present study presents CFD simulations of a liquid-piston compressor with metal foam inserts. The term "liquid-piston" implies that the compression of the gas is done with a rising liquid-gas interface created by pumping liquid into the lower section of the compression chamber. The liquid-piston compressor is an essential part of a Compressed Air Energy Storage (CAES) system. The reason for inserting metal foam in the compressor is to reduce the temperature rise of the gas during compression, since a higher temperature rise leads to more input work being converted into internal energy, which is wasted during the storage period as the compressed gas cools. Liquid, gas, and solid coexist in the compression chamber. The two-energy equation model is used; the energy equations of the fluid mixture and the solid are coupled through an interfacial heat transfer term. The fluid mixture, which includes both the gas phase and the liquid phase, is modeled using the Volume of Fluid (VOF) method. Commercial CFD software, ANSYS FLUENT, is used, by applying its default VOF code, with user-defined functions to incorporate the two-energy equation formulation for porous media. The CFD simulation requires modeling of a negative momentum source term (drag), and an interfacial heat transfer term. The first one is the pressure drop due to the metal foam, which is obtained from experimental measurements. To obtain the interfacial heat transfer term, a compression experiment is done, which provides instantaneous pressure and volume data. These data are compared to solutions of a zero-dimensional compression model based on different heat transfer correlations from published references. By this comparison, a heat transfer correlation which is most suitable for the present study is chosen for use in the CFD simulation. The CFD simulations investigate two types of metal foam inserts, two different layouts of the insert (partial vs. full), and two different liquid piston speeds. The results show the influence of the metal foam inserts on secondary flows and temperature distributions.
2007 International Conference on Mechatronics and Automation, 2007
Abstract-In this paper a modified discrete-time linear quadratic Gaussian (LQG) controller is pre... more Abstract-In this paper a modified discrete-time linear quadratic Gaussian (LQG) controller is presented in which the optimal control law is computed based on the dynamic programming (DP) algorithm. In derivation of the governing equations, it is assumed that the noise is ...
IEEE Transactions on Control Systems Technology, 2000
Journal of Microelectromechanical Systems, 2000
This paper examines the stabilization and deflec- tion control of an electrostatic microelectrome... more This paper examines the stabilization and deflec- tion control of an electrostatic microelectromechanical-system (MEMS) actuator using linear parameter-varying (LPV) control methodology. As a case study, a 1-DOF model of an electrosta- tic MEMS actuator is considered, and its static and dynamic characteristics are discussed. The presented model captures the significant characteristics of the actuator such as the pull-in ef- fect
Journal of Mechanical Engineering, 2010
Mechanical and thermodynamical performance of internal combustion engines is significantly affect... more Mechanical and thermodynamical performance of internal combustion engines is significantly affected by the engine working temperature. In an engine test bed, the internal combustion engines are tested in different operating conditions using a dynamometer. It is required that the engine temperature be controlled precisely, particularly in transient states. This precise control can be achieved by an engine coolant conditioning system mainly consisting of a heat exchanger, a control valve, and a controller. In this study, constitutive equations of the system are derived first. These differential equations show the second-order nonlinear time-varying dynamics of the system. The model is validated with the experimental data providing satisfactory results. After presenting the dynamic equations of the system, a fuzzy controller is designed based on our prior knowledge of the system. The fuzzy rules and the membership functions are derived by a trial and error and heuristic method. Because of the nonlinear nature of the system the fuzzy rules are set to satisfy the requirements of the temperature control for different operating conditions of the engine. The performance of the fuzzy controller is compared with a PI one for different transient conditions. The results of the simulation show the better performance of the fuzzy controller. The main advantages of the fuzzy controller are the shorter settling time, smaller overshoot, and improved performance especially in the transient states of the system.
A Compressed Air Energy Storage (CAES) test-bed has been developed to experimentally demonstrate ... more A Compressed Air Energy Storage (CAES) test-bed has been developed to experimentally demonstrate the energy storage concept proposed in [1] for offshore wind turbines. The design of the testbed has been adapted to the available air compression/expansion technology. The main components of the system consist of an open accumulator, a hydraulic pumpmotor, air compressor/expander, an electrical generator and load, a differential gearbox and a hydraulic control valve. These components are first characterized and then a dynamic model of the system has been developed. The objective is to regulate the output current/voltage of the generator while maintaining a constant accumulator pressure in the presence of input and demand power variations in the system. This is achieved by Proportional-Integrator (PI) control of pumpmotor displacement and field current of the generator. The stability of these controllers has been proved using an energybased Lyapunov function. Experimental results for storage and regeneration modes have been presented showing excellent performance of the system in response to power disturbances. NOMENCLATURE B c/e Compressor/expander damping (N.m/rad/s) D c/e Compressor/expander displacement (cc/rev) D pm Pump-motor displacement (cc/rev) G g Gear ratio between generator and differential J g Generator inertia (kg.m 2) J pm Pump-motor inertia (kg.m 2) J c Compressor inertia (kg.m 2) I F Generator field current (A)
... As explained before, the vibration signature over the test period is saved along with the cor... more ... As explained before, the vibration signature over the test period is saved along with the corresponding tacho signal. Using the tacho pulses, the engine vibration signal is split into the pieces corresponding to pairs of crankshaft revolutions. ... [6] Antonino-Daviu J., Riera-Guasp M ...
2014 American Control Conference, 2014
ABSTRACT
Asian Journal of Research in Banking and Finance, 2014
Volume 2: Heat Transfer Enhancement for Practical Applications; Heat and Mass Transfer in Fire and Combustion; Heat Transfer in Multiphase Systems; Heat and Mass Transfer in Biotechnology, 2013
An efficient and sufficiently power dense air compressor/expander is the key element in a Compres... more An efficient and sufficiently power dense air compressor/expander is the key element in a Compressed Air Energy Storage (CAES) approach. Efficiency can be increased by improving the heat transfer between air and its surrounding materials. One effective and practical method to achieve this goal is to use water droplets spray inside the chamber when air is compressing or expanding. In this paper, the air compression cycle is modeled by considering one-dimensional droplet properties in a lumped air model. While it is possible to inject water droplets into the compressing air at any time, optimal spray profile can result in maximum efficiency improvement for a given water to air mass ratio. The corresponding optimization problem is then defined based on the stored energy in the compressed air and the required input works. Finally, optimal spray profile has been determined for various water to air mass ratio using a general numerical approach to solve the optimization problem. Results show the potential improvement by acquiring the optimal spray profile instead of conventional constant spray flow rate. For the specific compression chamber geometry and desired pressure ratio and final time used in this work, the efficiency can be improved up to 4%.
Proceedings of the 2011 American Control Conference, 2011
ABSTRACT
Volume 2: Heat Transfer Enhancement for Practical Applications; Heat and Mass Transfer in Fire and Combustion; Heat Transfer in Multiphase Systems; Heat and Mass Transfer in Biotechnology, 2013
In the Compressed Air Energy Storage (CAES) approach, air is compressed to high pressure, stored,... more In the Compressed Air Energy Storage (CAES) approach, air is compressed to high pressure, stored, and expanded to output work when needed. The temperature of air tends to rise during compression, and the rise in the air internal energy is wasted during the later storage period as the compressed air cools back to ambient temperature. The present study focuses on designing an interrupted-plate heat exchanger used in a liquid-piston compression chamber for CAES. The exchanger features layers of thin plates stacked in an interrupted pattern. Twenty-seven exchangers featuring different combinations of shape parameters are analyzed. The exchangers are modeled as porous media. As such, for each exchanger shape, a Representative Elementary Volume (REV), which represents a unit cell of the exchanger, is developed. The flow through the REV is simulated with periodic velocity and thermal boundary conditions, using the commercial CFD software ANSYS FLUENT. Simulations of the REVs for the various exchangers characterize the various shape parameter effects on values of pressure drop and heat transfer coefficient between solid surfaces and fluid. For an experimental validation of the numerical solution, two different exchanger models made by rapid prototyping, are tested for pressure drop and heat transfer. Good agreement is found between numerical and experimental results. Nusselt number vs. Reynolds number relations are developed on the basis of pore size and on hydraulic diameter. To analyze performance of exchangers with different shapes, a simplified zero-dimensional thermodynamic model for the compression chamber with the inserted heat exchange elements is developed. This model, valuable for system optimization and control simulations, is a set of ordinary differential equations. They are solved numerically for each exchanger insert shape to determine the geometries of best compression efficiency.
2013 American Control Conference, 2013
The power density and efficiency of high compression ratio (∼200:1) air compressors/expanders are... more The power density and efficiency of high compression ratio (∼200:1) air compressors/expanders are crucial for the economical viability of a Compressed Air Energy Storage (CAES) system such as the one proposed in [1]. There is a trade-off between power density and efficiency that is strongly dependent on the heat transfer capability within compressor/expander. In previous papers, we have shown that the compression or expansion trajectory can be optimized so that for a given power, the efficiency can be optimized and vice versa. Theoretically, for high compression ratios, the improvement over ad-hoc trajectories can be significant-for example, at the same efficiency of 90%, the power can be increased by 3-5 folds [2], [3], [4], [5]. Yet, the optimal trajectories depend on the heat transfer coefficient profile that is often unknown. In this paper, we focus on the experimental study of an iterative control algorithm to track a compression trajectory that optimizes the efficiency-power trade-off in a liquid piston air compressor. First, an adaptive controller is developed to track any desired compression trajectory characterized by the temperature-volume profile. The controller adaptively estimates the unknown heat transfer coefficient. Second, the estimated heat transfer coefficient from one iteration is then used to estimate the optimal compression trajectory for the next iteration. As the estimate of the heat transfer coefficient improves from one iteration to the next, the quality of the estimated optimal trajectory also improves. This leads to successively improved efficiency. The experimental results of optimal trajectories show up to 2% improvement in compression efficiency compared to linear trajectories in a same power density.
ASME 2009 Dynamic Systems and Control Conference, Volume 2, 2009
The present paper employs a linear parameter-varying (LPV) control design approach with H perform... more The present paper employs a linear parameter-varying (LPV) control design approach with H performance specification for set-point tracking of deflection in an electrostatic MEMS actuator. First, we model the system dynamics in an LPV framework, considering the ...
Volume 8B: Heat Transfer and Thermal Engineering, 2013
The present study presents CFD simulations of a liquid-piston compressor with metal foam inserts.... more The present study presents CFD simulations of a liquid-piston compressor with metal foam inserts. The term "liquid-piston" implies that the compression of the gas is done with a rising liquid-gas interface created by pumping liquid into the lower section of the compression chamber. The liquid-piston compressor is an essential part of a Compressed Air Energy Storage (CAES) system. The reason for inserting metal foam in the compressor is to reduce the temperature rise of the gas during compression, since a higher temperature rise leads to more input work being converted into internal energy, which is wasted during the storage period as the compressed gas cools. Liquid, gas, and solid coexist in the compression chamber. The two-energy equation model is used; the energy equations of the fluid mixture and the solid are coupled through an interfacial heat transfer term. The fluid mixture, which includes both the gas phase and the liquid phase, is modeled using the Volume of Fluid (VOF) method. Commercial CFD software, ANSYS FLUENT, is used, by applying its default VOF code, with user-defined functions to incorporate the two-energy equation formulation for porous media. The CFD simulation requires modeling of a negative momentum source term (drag), and an interfacial heat transfer term. The first one is the pressure drop due to the metal foam, which is obtained from experimental measurements. To obtain the interfacial heat transfer term, a compression experiment is done, which provides instantaneous pressure and volume data. These data are compared to solutions of a zero-dimensional compression model based on different heat transfer correlations from published references. By this comparison, a heat transfer correlation which is most suitable for the present study is chosen for use in the CFD simulation. The CFD simulations investigate two types of metal foam inserts, two different layouts of the insert (partial vs. full), and two different liquid piston speeds. The results show the influence of the metal foam inserts on secondary flows and temperature distributions.
2007 International Conference on Mechatronics and Automation, 2007
Abstract-In this paper a modified discrete-time linear quadratic Gaussian (LQG) controller is pre... more Abstract-In this paper a modified discrete-time linear quadratic Gaussian (LQG) controller is presented in which the optimal control law is computed based on the dynamic programming (DP) algorithm. In derivation of the governing equations, it is assumed that the noise is ...
IEEE Transactions on Control Systems Technology, 2000
Journal of Microelectromechanical Systems, 2000
This paper examines the stabilization and deflec- tion control of an electrostatic microelectrome... more This paper examines the stabilization and deflec- tion control of an electrostatic microelectromechanical-system (MEMS) actuator using linear parameter-varying (LPV) control methodology. As a case study, a 1-DOF model of an electrosta- tic MEMS actuator is considered, and its static and dynamic characteristics are discussed. The presented model captures the significant characteristics of the actuator such as the pull-in ef- fect
Journal of Mechanical Engineering, 2010
Mechanical and thermodynamical performance of internal combustion engines is significantly affect... more Mechanical and thermodynamical performance of internal combustion engines is significantly affected by the engine working temperature. In an engine test bed, the internal combustion engines are tested in different operating conditions using a dynamometer. It is required that the engine temperature be controlled precisely, particularly in transient states. This precise control can be achieved by an engine coolant conditioning system mainly consisting of a heat exchanger, a control valve, and a controller. In this study, constitutive equations of the system are derived first. These differential equations show the second-order nonlinear time-varying dynamics of the system. The model is validated with the experimental data providing satisfactory results. After presenting the dynamic equations of the system, a fuzzy controller is designed based on our prior knowledge of the system. The fuzzy rules and the membership functions are derived by a trial and error and heuristic method. Because of the nonlinear nature of the system the fuzzy rules are set to satisfy the requirements of the temperature control for different operating conditions of the engine. The performance of the fuzzy controller is compared with a PI one for different transient conditions. The results of the simulation show the better performance of the fuzzy controller. The main advantages of the fuzzy controller are the shorter settling time, smaller overshoot, and improved performance especially in the transient states of the system.
A Compressed Air Energy Storage (CAES) test-bed has been developed to experimentally demonstrate ... more A Compressed Air Energy Storage (CAES) test-bed has been developed to experimentally demonstrate the energy storage concept proposed in [1] for offshore wind turbines. The design of the testbed has been adapted to the available air compression/expansion technology. The main components of the system consist of an open accumulator, a hydraulic pumpmotor, air compressor/expander, an electrical generator and load, a differential gearbox and a hydraulic control valve. These components are first characterized and then a dynamic model of the system has been developed. The objective is to regulate the output current/voltage of the generator while maintaining a constant accumulator pressure in the presence of input and demand power variations in the system. This is achieved by Proportional-Integrator (PI) control of pumpmotor displacement and field current of the generator. The stability of these controllers has been proved using an energybased Lyapunov function. Experimental results for storage and regeneration modes have been presented showing excellent performance of the system in response to power disturbances. NOMENCLATURE B c/e Compressor/expander damping (N.m/rad/s) D c/e Compressor/expander displacement (cc/rev) D pm Pump-motor displacement (cc/rev) G g Gear ratio between generator and differential J g Generator inertia (kg.m 2) J pm Pump-motor inertia (kg.m 2) J c Compressor inertia (kg.m 2) I F Generator field current (A)