Control of an open-loop hydraulic offshore wind turbine using a variable-area orifice

The research work disclosed in this publication is partly funded by the Malta Government Scholarship Scheme.The viability of offshore wind turbines is presently affected by a number of technical issues pertaining to the gearbox and power electronic components. Current work is considering the possibility of replacing the generator, gearbox and electrical transmission with a hydraulic system. Efficiency of the hydraulic transmission is around 90% for the selected geometries, which is comparable to the 94% expected for conventional wind turbines. A rotor-driven pump pressurises seawater that is transmitted across a large pipeline to a centralised generator platform. Hydroelectric energy conversion takes place in Pelton turbine. However, unlike conventional hydro-energy plants, the head available at the nozzle entry is highly unsteady. Adequate active control at the nozzle is therefore crucial in maintaining a fixed line pressure and an optimum Pelton turbine operation at synchronous speed. This paper presents a novel control scheme that is based on the combination of proportional feedback control and feed forward compensation on a variable area nozzle. Transient domain simulation results are presented for a Pelton wheel supplied by sea water from an offshore wind turbine-driven pump across a 10 km pipeline.peer-reviewe

Aeronautical Engineering: A continuing bibliography, supplement 120

This bibliography contains abstracts for 297 reports, articles, and other documents introduced into the NASA scientific and technical information system in February 1980

Aeronautical Engineering. A continuing bibliography, supplement 115

This bibliography lists 273 reports, articles, and other documents introduced into the NASA scientific and technical information system in October 1979

Plant-pollinator aerodynamics

Interactions between plants and pollinators have adapted over long evolutionary timescales and fill a vital ecological role. For flying pollinators, the same coherent aerodynamic mechanisms are employed across the broad Reynolds number range of 100-10,000. This thesis aims to understand some of the physics involved in plant-pollinator aerodynamics. First, studying the impact of an artificial flower wake on maneuverability revealed emergent simplicity in hawkmoth flower tracking dynamics with increased tracking error at the vortex shedding frequencies of the 3D-printed flower. These results establish that unsteady flow affects complex behaviors as well as steady flight performance. Next, the interplay between steady airflow and wing flexibility was explored in two flow regimes: (1) matching airflow conditions for Manduca sexta flight and (2) matching flow conditions known to produce decoherent leading-edge vortices (LEVs) on rigid wings. Although LEVs still burst on flexible hawkmoth wings, the LEV is decoherent over more of the wingspan as flexibility decreases. Enhanced LEV stability in the hawkmoth flight regime revealed that trade-offs between Coriolis forces (from wing rotation) and inertial forces (from both wing translation and the incoming airflow) influence LEV structure and lift force. Last, the wakes of hawkmoth-pollinated flowers were found to be turbulent but some irregular periodic structures were present downstream of small flowers (diameter less than 40 mm). Like many bluff body flow interactions, flower wakes are dominated by a re-circulation zone downstream and hawkmoths hover-feed within the re-circulation bubble. In addition to characterizing the local flow environment for a hovering hawkmoth, this work showed how flow in the flower wake impacts aerodynamic force (with a blade-element model). Despite the broad diversity in floral environments for pollinators, flapping flight (and the LEV in particular) remains a highly effective strategy. Future work can investigate how insects achieve consistent performance across variable environments from behavioral, neurological, and aerodynamic perspectives.Ph.D

6th International congress of the Serbian society of mechanics: Review

Ovaj rad prikazuje najvažnije informacije o 6. kongresu Srpskog društva za mehaniku, koji je održan na Tari od 19. do 21. juna 2017. Kongres je organizovan od strane Srpskog društva za mehaniku. Dat je kratak prikaz najznačajnijih radova predstavljenih na ovom kongresu, a koji se bave teorijskom i primenjenom mehanikom.This paper presents the most important information and describes the activities of the 6th Congress of the Serbian Society of Mechanics which was held on mountain Tara, on 19- 21 June, 2017. The Congress was organized by the Serbian Society of Mechanics. Brief summaries of the plenary lectures and some of 99 accepted papers, which admittedly attracted the most interest were shown as well

6th International congress of the Serbian society of mechanics: Review

Ovaj rad prikazuje najvažnije informacije o 6. kongresu Srpskog društva za mehaniku, koji je održan na Tari od 19. do 21. juna 2017. Kongres je organizovan od strane Srpskog društva za mehaniku. Dat je kratak prikaz najznačajnijih radova predstavljenih na ovom kongresu, a koji se bave teorijskom i primenjenom mehanikom.This paper presents the most important information and describes the activities of the 6th Congress of the Serbian Society of Mechanics which was held on mountain Tara, on 19- 21 June, 2017. The Congress was organized by the Serbian Society of Mechanics. Brief summaries of the plenary lectures and some of 99 accepted papers, which admittedly attracted the most interest were shown as well

Coupling road vehicle aerodynamics and dynamics in simulation

A fully coupled system in which a vehicle s aerodynamic and handling responses can be simulated has been designed and evaluated using a severe crosswind test. Simulations of this type provide vehicle manufacturers with a useful alternative to on road tests, which are usually performed at a late stage in the development process with a proto- type vehicle. The proposed simulations could be performed much earlier and help to identify and resolve any aerodynamic sensitivities and safety concerns before significant resources are place in the design. It was shown that for the simulation of an artificial, on-track crosswind event, the use of the fully coupled system was unnecessary. A simplified, one-way coupled system, in which there is no feedback from the vehicle s dynamics to the aerodynamic simulation was sufficient in order to capture the vehicle s path deviation. The realistic properties of the vehicle and accurately calibrated driver model prevented any large attitude changes whilst immersed in the gust, from which variations to the aerodynamics could arise. It was suggested that this system may be more suited to other vehicle geometries more sensitive to yaw motions or applications where a high positional accuracy of the vehicle is required

Proceedings of the International Micro Air Vehicles Conference and Flight Competition 2017 (IMAV 2017)

The IMAV 2017 conference has been held at ISAE-SUPAERO, Toulouse, France from Sept. 18 to Sept. 21, 2017. More than 250 participants coming from 30 different countries worldwide have presented their latest research activities in the field of drones. 38 papers have been presented during the conference including various topics such as Aerodynamics, Aeroacoustics, Propulsion, Autopilots, Sensors, Communication systems, Mission planning techniques, Artificial Intelligence, Human-machine cooperation as applied to drones

14th International Conference on Turbochargers and Turbocharging

14th International Conference on Turbochargers and Turbocharging addresses current and novel turbocharging system choices and components with a renewed emphasis to address the challenges posed by emission regulations and market trends. The contributions focus on the development of air management solutions and waste heat recovery ideas to support thermal propulsion systems leading to high thermal efficiency and low exhaust emissions. These can be in the form of internal combustion engines or other propulsion technologies (eg. Fuel cell) in both direct drive and hybridised configuration. 14th International Conference on Turbochargers and Turbocharging also provides a particular focus on turbochargers, superchargers, waste heat recovery turbines and related air managements components in both electrical and mechanical forms

Torque converter turbine noise and cavitation noise over varying speed ratio

These investigations will discuss the operational noise caused by automotive torque converters during speed ratio operation. Two specific cases of torque converter noise will be studied; cavitation, and a monotonic turbine induced noise. Cavitation occurs at or near stall, or zero turbine speed. The bubbles produced due to the extreme torques at low speed ratio operation, upon collapse, may cause a broadband noise that is unwanted by those who are occupying the vehicle as other portions of the vehicle drive train improve acoustically. Turbine induced noise, which occurs at high engine torque at around 0.5 speed ratio, is a narrow-band phenomenon that is audible to vehicle occupants currently. The solution to the turbine induced noise is known, however this study is to gain a better understanding of the mechanics behind this occurrence. The automated torque converter dynamometer test cell was utilized in these experiments to determine the effect of torque converter design parameters on the offset of cavitation and to employ the use a microwave telemetry system to directly measure pressures and structural motion on the turbine. Nearfield acoustics were used as a detection method for all phenomena while using a standardized speed ratio sweep test. Changes in filtered sound pressure levels enabled the ability to detect cavitation desinence. This, in turn, was utilized to determine the effects of various torque converter design parameters, including diameter, torus dimensions, and pump and stator blade designs on cavitation. The on turbine pressures and motion measured with the microwave telemetry were used to understand better the effects of a notched trailing edge turbine blade on the turbine induced noise