People in modern industrialized societies live a blessed life relative to those who do not when it comes to some modern conveniences. While many think nothing of flipping on a light switch or running electric appliances, there are people in third world countries could not imagine such things. As service projects are being undertaken to bring such conveniences to those less fortunate, there often is the harsh reality of a strict budget. An item that commands a large portion of said budget is often the diesel generator used to provide the facility with electricity. Generators serving motor loads are typically oversized due to a large kVA starting requirement. This paper addresses an approach to this problem by temporarily restricting the generator fuel supply by pulling back the rack of the mechanical governor reducing the frequency and voltage output as a motor load is switched onto the system. By reducing the voltage and frequency output of the generator, the motor is switched on at a time when its typically poor power factor and resulting kVA requirement is mitigated by the lower voltage and frequency allowing for a smaller generator to be used.

Fluid-structure interactions appear in many industrial applications in the field of energy technology. As the components are more and more pushed to higher performance, taking fluid-structure interaction phenomena into account has a great impact on the design as well as in the cost and safety. Internal flows related to propulsion systems in aerodynamics area are of our interest; and particularly aeroelasticity and flutter phenomena. A new 2D flexible generic model, so called bump, based on previous studies at the division of Heat and Power Technology about fluid-structure interactions is here presented. The overall goal is to enhance comprehension of flutter phenomenon. The current study exposes a preliminary experimental campaign regarding mechanical behaviour on two different test objects: an existing one made of polyurethane and a new one of aluminium. The setup is built in such a way that it allows the bumps to oscillate until 500Hz. The objective is to reach this frequency range by remaining in the first bending mode shape which is indeed considered as fundamental for flutter study. In this manner being as close as possible to the bending flutter configuration in high-subsonic and transonic flows will provide a deeper understanding of the shock wave boundary layer interaction and the force phase angle related to it. The results have pointed out that the bumps can reach a frequency of 250Hz by remaining in the first bending mode shape. The one in polyurethane can even reach frequency up to 350Hz; however, amplitude is higher than the theoretical one fixed to 0.5mm. Then unsteady pressure measurements for one operating point have been performed based on using recessed-mounted pressure transducers with Kulite fast response sensors. Variation amplitudes and phases of the unsteady pressure are thus correlated with the vibrations of the model. The operating point has been defined with respect to previous studies on the same static geometric model in order to use steady state base line; the steady flows appear consistent with each other. The results have pointed out that the shock wave induces strong amplification of the steady static pressure; however, this rise decreases when the reduced frequency increases. Finally some elements regarding propagating waves are suggested in the analysis for deeper investigations on such complex phenomena.

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The work presented in this thesis attempts to provide an understanding of the physics behind the dynamic stall process by simulating the flow past pitching NACA-0012 airfoil at 100,000 and 1 million Reynolds number based on the chord length of the airfoil and at different reduced frequencies of 0.188 and 0.25 respectively in a three dimensional flow field. The mean angles of attack are 12 deg. and 15 deg. and the amplitudes of pitching are 6 deg. and 10 deg. respectively. The turbulence in the flow field is resolved using large eddy simulations with dynamic Smagorinsky model at the sub grid scale. The lift hysteresis plots of this simulation for both the configurations are compared with the corresponding experiments. The development of dynamic stall vortex, vortex shedding and reattachment as predicted by the present study are discussed in detail. There is a fairly good match between the predicted and experimentally measured lift coefficient during the upstroke for both cases. The net lift coefficient for the Re = 100,000 case during downstroke matches with the corresponding experimental data, the present study under-predicts the lift coefficient as compared to the experimental values at the start of downstroke and over-estimates for the remaining part of the downstroke. The trend of the lift coefficient hysteresis plot with the experimental data for the Re = 1 million case is also similar. This present simulations have shown that the downstroke phase of the pitching motion is strongly three dimensional and is highly complex, whereas the flow is practically two dimensional during the upstroke. / Master of Science

In this thesis the characteristics of pitch and roll damping coefficients of missile models are investigated by using Computational Fluid Dynamics (CFD) techniques. Experimental data of NACA0012 airfoil, Basic Finner (BF) and Modified Basic Finner (MBF) models are used for validation and verification studies. Numerical computations are performed from subsonic to supersonic flow regimes. Grid refinement and turbulence model selection studies are conducted before starting the dynamic motion simulations. Numerical method of dynamic motion simulation is validated with a 2D NACA0012 airfoil. After the validation of numerical method, forced-oscillation motion is given to the BF and MBF models. In order to get deeper understandings about the characteristics of dynamic pitching and rolling motions, parametric studies are performed. The amplitude and frequency of forced-oscillation motions are investigated one by one. The effects of angle of attacks are also investigated for both pitching and rolling motions. The results of CFD simulations are compared with experimental data obtained from different wind tunnel and free flight tests. It is seen from these comparisons that experimental and numerical results are in good agreement throughout the whole flow regime. In conclusion, the numerical method presented in this study is validated and can be used for the prediction of pitch and roll damping coefficient of any missile configurations.

<p>Sensorineural hearing loss imparts two serious hearing deficits in hearing-impaired people: reduced dynamic range of hearing and reduced frequency selectivity. Psychophysically, these deficits render loss of speech audibility and speech intelligibility to a hearing-impaired person. Studies of an impaired cochlea in cats have shown that the hearing loss originates from damage to or complete loss of inner and outer hair cells. Neurophysiology of an impaired cochlea in cats shows that the tuning curves of the auditory nerve fibers become elevated and broadened. Amplification in hearing aids has been used to restore audibility in hearing-impaired people. Multiband compression has been commercially available in conventional hearing aids to compensate for the reduced dynamic range of hearing. However, little has been achieved to improve the intelligibility of speech in the hearing-impaired people. The aim of this thesis is to restore not only the speech audibility in a hearing-impaired person, but also to improve their speech intelligibility through some hearing-aid signal processing. The compensation technique used in this thesis for speech intelligibility is based on the hypothesis that a narrowband response of the auditory nerve fibers to speech signals ensure phonemic discriminability in the central nervous system.</p><p>Miller et al. [1999] have proposed contrast-enhancing frequency shaping ( CEFS) to compensate for the broadband responses of the fibers to first and second formants (Fl and F2) of a speech stimulus. Bruce [2004] has shown that the multiband compression can be combined with CEFS without counteracting each other. In Bruce's algorithm, a multiband compressor is serially combined with a time-domain CEFS filter. The MICEFS algorithm, herein presented, is a combination of multiband compression and an improved version of CEFS implemented in the frequency domain. The frequency domain implementation of MICEFS has improved the time delay response of the algorithm by 10 ms as compared to series implementation proposed by Bruce. The total time delay of the MICEFS algorithm is 16 ms, which is still longer than the standard time delay of 10 ms in hearing aids. The MICEFS algorithm was tested on a computational model of auditory periphery [Bruce et al., 2003] using a synthetic vowel and a synthetic sentence. The testing paradigm consisted of five conditions: 1) unmodified speech presented to a normal cochlea; 2) speech modified with halfgain rule presented to an impaired cochlea; 3) CEFS modified speech presented to the impaired cochlea; 4) speech modified with MICEFS presented to the impaired cochlea, and; 5) MICEFS-modified speech with some added noise in the formant estimation presented to an impaired cochlea. The spectral enhancement filter used in MICEFS has improved the synchrony capture of the fibers to the first three formants of a speech stimulus. MICEFS has also restored the correct tonotopic representation in the average discharge rate of the fibers at the first three formants of the speech.</p> / Thesis / Master of Applied Science (MASc)

Forced response which is blade vibration due to an external excitation can lead to blade failure. The estimation of the level of vibration is dependent on the determination of aerodynamic damping. This thesisinvestigates the determination of aerodynamic damping at high reduced frequencies in turbomachines. The aerodynamic damping was calculated by a linearized Navier-Stokes flow solver with exact 3D non-reflecting boundary conditions. The method was validated using the two-dimensional test cases (Standard Configuration 5 and 8). Thereafter, two 3D profiles were also investigated: an aeroelastic turbine rig (AETR) which is a subsonic turbine case, and a virtual integrated compressor (VINK) which is a transonic compressor case. In AETR case, the first bending mode with reduced frequency 2.0 was studied. The 3D acoustic modes were calculated and the rate of decay was plotted as a function of nodal diameter and radial order. This plot identified six acoustic resonant points which included two points corresponding to the first radial order. The six resonance points correspond to six peaks in the damping curve. In VINK case, the fifth mode (1854 Hz, reduced frequency 3.1) was investigated. Acoustic resonance was predicted to occur for the first and second radial orders at the inlet. It was concluded that the higher order resonance points are influencing the damping curve. There were some inconsistencies in the results and grid convergence was not achieved. These inconsistencies were due to the difficulty in calculating the acoustic modes at the transonic inlet with an impinging shock. / Aerodynamiskt påtvingade vibrationer, som är bladvibrationer på grund av en extern excitation kan leda till haveri. Prediktering av vibrationen är beroende av bestämning av aerodynamisk dämpning. I detta arbete undersöks bestämningen av aerodynamisk dämpning vid höga reducerade frekvenser i turbomaskiner. Den aerodynamiska dämpningen beräknades genom en linjäriserad Navier-Stokeslösare med exakta 3D icke-reflekterande gränsvillkor. Metoden validerades med hjälp av de tvådimensionella testfallen (Standardkonfiguration 5 och 8). Därefter undersöktes två 3D-profiler: en aeroelastisk turbinrigg (AETR), som är en subsonisk turbinenhet och en virtuell integrerad kompressor (VINK) som är ett transoniskt kompressorfall. I AETRfallet undersöktes det första böjningsformen med reducerad frekvens 2.0. 3D akustiska lägen beräknades och graden av förfall visades som en funktion av noddiameter och radiell grad. Denna metod identifierade sex akustiska resonanspunkter som innehöll två punkter som motsvarade den första radiella graden. De sex resonanspunkterna motsvarar sex toppar i dämpningskurvan. I VINK-fallet undersöktes den femte svängningsformen (1854 Hz, reducerad frekvens 3.1). Akustisk resonans förutspåddes inträffa för första och andra radiella graden vid inloppet. Slutsatsen drogs att de högre ordningens resonanspunkter påverkar dämpningskurvan. Det fanns vissa inkonsekvenser i resultaten och gridkonvergens uppnåddes inte. Dessa inkonsekvenser berodde på svårigheten att beräkna de akustiska svängningsformerna vid det transoniska inloppet med en stötvåg.