2,814 research outputs found
Impact of electrically assisted turbocharging on the transient response of an off-highway diesel engine
Engine boosting via turbocharging is a method to increase the engine power output with minimal or no increase in engine parasitic, frictional and pumping losses. Turbocharging in conjunction with engine down-sizing and down-speeding allows a reduction of engine fuel consumption, while maintaining a high engine power output. However, turbocharging introduces a lag in engine transient response, caused by the finite amount of time required by the turbocharger to accelerate, which has to be minimized.
Electric turbocharger assistance consists of coupling an electric motor/generator to a standard turbocharger. The scope of the motor/generator is to increase the power available to accelerate the rotor assembly, so that the time to boost is reduced. The motor/generator could also be utilized to brake the turbocharger to control boost and avoid over-speeds, thus replacing the conventional waste-gate. Furthermore, electric assistance allows turbocompounding to be implemented. Turbocompounding improves the engine efficiency by utilizing the turbine and motor/generator to recuperate additional exhaust flow energy.
In this thesis, the electric turbocharger assistance impact on the turbocharger and engine performance is studied. An electrically assisted turbocharger prototype has been developed by industrial partners and it has been tested by the author of this thesis. The performance of the turbocharger turbine and motor/generator has been characterized over the full speed range and the impact of the electric assistance on the turbine flow has been investigated experimentally. It has not been possible to characterize the turbine up to choking conditions, so the data has been extrapolated via a mean-line model. The performance data obtained has been utilized to generate a model of the assisted turbocharger, which has been coupled to a one-dimensional model of a non-highway 7-litre diesel engine. This model has been utilized to study the impact of electric turbocharger assistance on the engine transient performance.
The electrical machine characterization revealed that the switched reluctance motor/generator operates efficiently up to a speed of 135,000 rev/min, making it one of the fastest running switched reluctance machines of this size. The peak machine efficiency is 93% (excluding the turbocharger bearing losses) and the maximum power output measured is 5.3 kW in generating mode and 4.3 kW in motoring mode. The motor/generator rotor aerodynamic drag loss has been calculated via computational fluid dynamics software and has been found to be 63 W at 140,000 rev/min.
Via a novel experimental technique, it has been possible to characterize the turbocharger turbine down to an expansion ratio of 1.00. This experiment revealed that the mass flow rate drops to zero at an expansion ratio higher than unity and that below this critical pressure ratio the turbine flow is reversed. The characterization of the turbine during speed transients showed that the operating point on the performance map deviates from the quasi-steady line. This indicates that minor unsteady effects occur in the turbine and exhaust manifold flow. A further experiment revealed that the motor/generator torque oscillations have a negligible impact on the turbine performance.
The engine simulations showed that the ideal electric assistance motoring power for this application is in the 5 to 10 kW range. A 5 kW machine reduces the engine speed drop, which occurs when the engine load is suddenly increased, by up to 83%, depending on the initial load and load step size, and reduces the time to recover the original speed by up to 86%. The simulations also revealed that electric assistance is more effective than the turbine variable geometry system in improving the engine transient response, but the variable geometry system is useful to optimize boost for engine specific fuel consumption over different engine loading conditions.Open Acces
Magnetic Bearing for Bently Nevada RK4 Rotor Kits
Active Magnetic Bearings (AMB) are contact free bearings that support loads by magnetic levitation. This is accomplished by generating magnetic forces with electric current through a series of electromagnets surrounding a suspended rotor mass. Along with a set of electromagnets, an AMB assembly also consists of power amplifiers for each electromagnet, a controller, and proximity sensors. The proximity sensors provide rotor position feedback to the control system, which modulates power to the amplifiers [4]. Magnetic bearings are used in several industrial applications today, including but not limited to compressors, turbines, pumps, motors, and generators. Advantages of their utility include very low to no friction, longer life than bearings with lubrication (no wear), high operation speeds, environmental friendliness (oil and contamination free), and the ability to accommodate irregularities in the mass distribution automatically. Disadvantages include complexity, little to no damping, difficulty to control, and high cost. Magnetic bearings are finding increasing use as the technology progresses and components becomes less expensive
Solar photovoltaic water pumping system using a new linear actuator
In this paper a photovoltaic solar pumping system using a new linear actuator is presented. This linear actuator is a
double-sided flat two-phase variable-reluctance linear stepper motor that moves a piston-type water pump with the help of a
rope, a pulley and a counterweight. The entire actuator pump ensemble is controlled by a simple electronic unit that manages
the electric power generated by a photovoltaic array. The proposed system is suitable for rural communities in developing
countries because it is reliable, affordable and easy to maintain.Postprint (published version
Design definition of a mechanical capacitor
A design study and analyses of a 10 kW-hr, 15 kW mechanical capacitor system was studied. It was determined that magnetically supported wheels constructed of advanced composites have the potential for high energy density and high power density. Structural concepts are analyzed that yield the highest energy density of any structural design yet reported. Particular attention was paid to the problem of 'friction' caused by magnetic and I to the second power R losses in the suspension and motor-generator subsystems, and low design friction levels have been achieved. The potentially long shelf life of this system, and the absence of wearing parts, provide superior performance over conventional flywheels supported with mechanical bearings. Costs and economies of energy storage wheels were reviewed briefly
Magnetic Bearings
The term magnetic bearings refers to devices that provide stable suspension of a rotor. Because of the contact-less motion of the rotor, magnetic bearings offer many advantages for various applications. Commercial applications include compressors, centrifuges, high-speed turbines, energy-storage flywheels, high-precision machine tools, etc. Magnetic bearings are a typical mechatronic product. Thus, a great deal of knowledge is necessary for its design, construction and operation. This book is a collection of writings on magnetic bearings, presented in fragments and divided into six chapters. Hopefully, this book will provide not only an introduction but also a number of key aspects of magnetic bearings theory and applications. Last but not least, the presented content is free, which is of great importance, especially for young researcher and engineers in the field
Modeling and analysis of a class of linear reluctance actuators for advanced precision motion systems
Reluctance actuators (RA) are a type of electromagnetic actuator that offer high
forces for short range motions. The RA takes advantage of the electromagnetic reluctance
force property in air gaps between the stator core and mover parts. The
mover accelerates because the stator generates the magnetic flux that produces an
attractive magnetic attraction between the stator and mover. Hysteresis and other
non-linearities in the magnetic flux have an impact on the force and have a nonlinear
gap dependency. It is demonstrated that the RA has the capacity to produce a
force that is effective and suitable for millimeter-range high-acceleration applications.
One application for the RA is the short-stroke stage of photolithography machines
for example. The RA is available in a wide variety of configurations, such as CCore,
E-Core, Maxwell, and Plunger-type designs. The RA requires precise dynamic
models and control algorithms to help linearize the RA for better control and optimization.
Some nonlinear dynamics include magnetic hysteresis, flux fringing, and
eddy currents. The RA is shown to have a much higher force density than any other
traditional actuator, with the main disadvantage being the nonlinear and hysteretic
behaviour which makes it hard to control without proper dynamic and control models
in place. It is important to model the RA accurately for better control. The output
force can be significantly impacted by unequal offsets or asymmetries between the
mover and stator. In the thesis that follows, a review of RA systems is performed, an
investigation that shows the importance of including the mean path length (MPL)
term for higher accuracy, a technique for calculating the force of various asymmetrical
instances for the C-core RA is demonstrated. This thesis documents currently available
knowledge of the RA such as available applications, configurations, dynamic
models, measurement systems, and control systems for the RA. The findings presented
can allow for future control systems to be designed to counteract multi-axial
asymmetric issues of the RA
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