Abstract: In a travelling wave thermoacoustic device, the
regenerator sandwiched between a pair of (hot and cold) heat
exchangers constitutes the so-called thermoacoustic core, where the
thermoacoustic energy conversion from heat to acoustic power takes
place. The temperature gradient along the regenerator caused by the
two heat exchangers excites and maintains the acoustic wave in the
resonator. The devices are called travelling wave thermoacoustic
systems because the phase angle difference between the pressure and
velocity oscillation is close to zero in the regenerator. This paper
presents the construction and testing of a thermoacoustic engine
equipped with a ceramic regenerator, made from a ceramic material
that is usually used as catalyst substrate in vehicles- exhaust systems,
with fine square channels (900 cells per square inch). The testing
includes the onset temperature difference (minimum temperature
difference required to start the acoustic oscillation in an engine), the
acoustic power output, thermal efficiency and the temperature profile
along the regenerator.
Abstract: Nowadays the control of stator voltage at a constant frequency is one of the traditional and low expense methods in order to control the speed of induction motors near its nominal speed. The torque of induction motor is a nonlinear function of the firing angle, phase angle and speed. In this paper the speed control of induction motor regarding various load torque and under different conditions will be investigated based on a fuzzy controller with inverse training.
Abstract: In the LFC problem, the interconnections among some areas are the input of disturbances, and therefore, it is important to suppress the disturbances by the coordination of governor systems. In contrast, tie-line power flow control by TCPS located between two areas makes it possible to stabilize the system frequency oscillations positively through interconnection, which is also expected to provide a new ancillary service for the further power systems. Thus, a control strategy using controlling the phase angle of TCPS is proposed for provide active control facility of system frequency in this paper. Also, the optimum adjustment of PID controller's parameters in a robust way under bilateral contracted scenario following the large step load demands and disturbances with and without TCPS are investigated by Particle Swarm Optimization (PSO), that has a strong ability to find the most optimistic results. This newly developed control strategy combines the advantage of PSO and TCPS and has simple stricture that is easy to implement and tune. To demonstrate the effectiveness of the proposed control strategy a three-area restructured power system is considered as a test system under different operating conditions and system nonlinearities. Analysis reveals that the TCPS is quite capable of suppressing the frequency and tie-line power oscillations effectively as compared to that obtained without TCPS for a wide range of plant parameter changes, area load demands and disturbances even in the presence of system nonlinearities.
Abstract: In this study, rotating flexible shaft-disk system
having flexible beams is considered as a dynamic system. After
neglecting nonlinear terms, torsional vibration of the shaft-disk
system and lateral and longitudinal vibration of the flexible beam are
still coupled through the motor speed. The system has three natural
frequencies; the flexible shaft-disk system torsional natural
frequency, the flexible beam lateral and longitudinal natural
frequencies. Eigenvalue calculations show that while the shaft speed
changes, torsional natural frequency of the shaft-disk system and the
beam longitudinal natural frequency are not changing but the beam
lateral natural frequency changes. Beam lateral natural frequency
stays the same as the nonrotating beam lateral natural frequency ωb
until the motor speed ωm is equal to ωb. After then ωb increases and
remains equal to the motor speed ωm until the motor speed is equal to
the shaft-disk system natural frequency ωT. Then the beam lateral
natural frequency ωb becomes equal to the natural frequency ωT and
stays same while the motor speed ωm is increased. Modal amplitudes
and phase angles of the vibrations are also plotted against the motor
speed ωm.