Academic literature on the topic 'Jet Vehicle'

Dynamic positioning systems have been under development since the first implementation in the early 1960s. The purpose of a dynamic position system is to allow for automatic positioning of a vessel when circumstances do not allow for mooring or anchoring. Historically the development has been driven forward by the offshore industry, while in recent years such systems have been found useful in other parts of the maritime industry as well. However, very few options exist today for jet driven vessels. One of the main parts of a dynamic positioning system is the control allocation. The purpose of this part is to allocate desired actuation to available actuators. It is often desirable to do this while considering a secondary objective, often energy consumption. One allocation algorithm option is direct allocation, which is considered to be quite a basic solution. More advanced options exist in the literature but implementations of them are still uncommon. An example of a more advanced option, allowing for better tuning, is using model-based allocators. Formulating the allocation problem as a linear quadratic problem and using a linear quadratic regulator is one viable option that has been proven to work well for non-jet driven vessels. A general vessel model is developed and used for simulating and testing different allocators. Furthermore, a method for transforming the allocated actuation into parameters that can control the jet engine is also proposed. This is a necessary step in order to be able to implement the allocation onto a vessel. Comparing the allocation options based on step responses with and without disturbances shows that the linear quadratic regulator preforms better than the direct allocator in almost every way. However, the main drawback of model-based controllers is the needed knowledge about the system. This is something that is not required for the direct allocator and is worth taking into account.<br>Dynamiska positioneringssystem har vart under utveckling sedan den första implementeringen i början av 1960-talet. Syftet med ett dynamiskt positioneringssystem är att möjliggöra automatisk positionering av ett fartyg när omständigheterna inte tillåter förtöjning eller förankring. Historiskt har utvecklingen drivits framåt av behovet inom offshoreindustrin, men under senare år har systemen visat sig vara användbara även i andra delar av den marina industrin. Idag finns dock få alternativ anpassade för jetdrivna fartyg. En av huvuddelarna i ett dynamiskt positioneringssystem är kraftallokering. Syftet med denna del är att fördela önskad styrkraft till tillgängliga ställdon. Ofta är det önskvärt att göra detta samtidigt som ett sekundärt mål tas hänsyn till, vanligtvis energiförbrukning. Ett alternativ för kraftallokering är en direkt allokeringsalgoritm, detta är en ganska enkel algoritm. Mer avancerade alternativ finns i litteraturen, men implementerade exempel är fortfarande ovanliga. Ett exempel på ett mer avancerat alternativ, som möjliggör bättre anpassning, är att använda modellbaserade algoritmer. Att formulera allokeringsproblemet som ett linjärt kvadratiskt problem och använda en linjär kvadratisk regulator är ett alternativ som har visat sig fungera bra för icke jetdrivna fartyg. En generell fartygsmodell utvecklas och anvnnds för att simulera och testa de olika allokeringsalgoritmerna. Vidare föreslås en metod för att omvandla den allokerade styrkraften till parametrar som kan styra jetmotorerna. Detta är ett nödvändigt steg för att, i slutändan, kunna implementera styrkrafterna på ett riktigt fartyg. En jämförelse av allokeringsalgoritmer baserade på stegsvar med och utan störningar visar att den linjära kvadratiska regulatorn hanterar de uppsatta testfallen bättre än den direkta allokeraren. Däremot dras den modellbaserade algoritmen med det problemet att omfattande kunskapen krävs angående systemets dynamik. Detta är något som inte krävs för direktallokeraren och är värt att ta hänsyn till.

<p>This thesis work was executed at Swift Engineering Incorporated located in San Clemente, California during spring in 2009. Placement supervisor from Swift was Mark Page and advisor and examiner from the Division of future products at Mälardalen University, Sweden was Gustaf Enebog.</p><p>The objective with this thesis work was to examine the effects of fitness ratio, lift over drag, lift coefficient at cruise, winglet span, wing sweep angle, wing aspect ratio, wing area and weights with respect to Mach number for a conventional business jet capable of 18 passengers. The cruise speed study range from Mach 0.88 to 0.99.</p><p>The Excel based conceptual design tool Jetsizer 2008c was used to make four models with similar configuration and mission but with different cruise Mach numbers.</p><p>A new Jetsizer module was then created to handle a modification process where the models are optimized for their speed and configuration. The result in this report gives guidelines for the needed values when creating an initial CFD model for this type of airplane.</p>

The ferry line company VIKING LINE has put in an order for a new vessel with a planned delivery for the year 2020. The vessel will berth and depart daily from the Stockholm port, Stadsgården. The vessel is equipped with two 10 MW Azipod propeller systems. This new propulsion system has the capability of rotating the direction of the propeller thrust 360° which is different from other vessels currently using the same port. The direction and distance of the propeller from the quay has raised concern at the Ports of Stockholm. The integrity and design of the quay wall at Stadsgården is to be related to the guidelines set in place by the World Association for Waterborne Transport Infrastructure (PIANC) Working Group 180: “Guidelines for Protecting Berthing Structures from Scour Caused by Ships.” The guidelines have been compared to the actuator disc theory in order to validate the initial jet stream velocity from the new propeller system. The propagation of the jet stream was later analyzed and a velocity at the quay wall is calculated. A lack of information from certain parameters in the guidelines has led to implementations of assumptions. Uncertainties in the methods and equations presented by the guidelines are discussed. Overall, the guidelines were applicable in the investigation of the new vessel at Stadsgården. The jet stream velocity from the new vessel is compared to the velocity from a similar vessel currently using the same berthing structure. From the comparison it is seen that the berthing structure will be exposed to velocities four times larger than the current jet stream velocities at Stadsgården. A list with recommended action that can be performed by the Ports of Stockholm is presented.<br>Fartygsföretaget VIKING LINE har beställt ett nytt fartyg med planerad leverans år 2020. Fartyget kommer att trafikera dagligen från Stockholm hamnen, Stadsgården. Fartyget är utrustat med två 10 MW Azipod propeller system. Detta nya framdrivningssystem har förmågan att rotera riktningen för propellern 360° vilket skiljer sig från andra fartyg som för närvarande använder samma hamn. Propeller riktning och avstånd från kajen har uppmärksammats hos Stockholms Hamnar. Stabiliteten av kajväggen på Stadsgården ska relateras till de riktlinjer som fastställs av PIANC Arbetsgrupp 180: "Guidelines for Protecting Berthing Structures from Scour Caused by Ships." Riktlinjerna har jämförts med ’actuator disc theory’ för att validera den ursprungliga jetströmhastigheten från den nya propellern. Spridningen av strålströmmen analyserades senare och en hastighet vid kajväggen beräknas. Brist på information från vissa parametrar i riktlinjerna har lett till implementeringar av antaganden. Osäkerheter i de metoder och ekvationer som presenteras i riktlinjerna diskuteras. Jetströmshastigheten från det nya fartyget jämförs med hastigheten från ett liknande fartyg som för närvarande utnyttjar samma hamn. Från jämförelsen framgår det att kajfronten kommer att exponeras för hastigheter fyra gånger större än de nuvarande jetströmshastigheterna på Stadsgården. En lista med rekommenderad åtgärd som kan utföras av Stockholms Hamnar presenteras.

Ducted fan vehicles possess a superior ability to maximize payload capacity while minimizing vehicle size. Their ability to both hover and fly at high speed is a key advantage for information-gathering missions, particularly when close proximity to a target is essential. However, the ducted fanâ s aerodynamic characteristics pose difficulties for stable vehicle flight and therefore require complex control algorithms. In particular, they exhibit a large nose-up pitching moment during wind gusts and when transitioning from hover to forward flight. Understanding ducted fan aerodynamic behavior and how it can be altered through flow control techniques are the two prime objectives of this work. This dissertation provides a new paradigm for modeling the ducted fanâ s nonlinear behavior and new methods for changing the duct aerodynamics using active flow control. Steady and piezoelectric synthetic jet blowing are employed in the flow control concepts and are compared. The new aerodynamic model captures the nonlinear characteristics of the force, moment, and power data for a ducted fan, while representing these terms in a set of simple equations. The model attains excellent agreement with current and legacy experimental data using twelve non-dimensional constants. Synthetic jet actuators (SJA) have potential for use in flow control applications in UAVs with limited size, weight, and power budgets. Piezoelectric SJAs for a ducted fan vehicle were developed through two rounds of experimental designs. The final SJA design attained peak jet velocities in the range of 225 ft/sec (69 m/s) for a 0.03â x 0.80â rectangular slot. To reduce the magnitude of the nose-up pitching moment in cross-winds, two flow control concepts were explored: flow separation control at the duct lip, and flow turning at the duct trailing edge using a CoandÄ surface. Both concepts were experimentally proven to be successful. Synthetic jets and steady jets were capable of modifying the ducted fan flow to reduce pitching moment, but some cases required high values of steady blowing to create significant responses. Triggering leading edge separation on the duct lip was one application where synthetic jets showed comparable performance to steady jets operating at a blowing coefficient an order of magnitude higher.<br>Ph. D.

Multidisciplinary design optimization (MDO) is a technique that has found use in the field of aerospace engineering for aircraft design. It uses optimization to simultaneously solve design problems with several disciplines involved. In order to predict aircraft performance an engine performance simulation model, also called “rubber engine”, is vital. The goal of this project is to validate and integrate a rubber engine model into an MDO environment. A method for computer simulation of gas turbine aero engine performance was created. GasTurb v11, a commercial gas turbine performance simulation software, was selected for doing the simulation models. The method was validated by applying it to five different jet engines of different size, different type and different age. It was shown that the simulation engine model results are close to the engine manufacturer data in terms of SFC and net thrust during cruise, maximum climb (MCL) and take off (MTO) thrust ratings. The cruise, take off and climb SFC was in general predicted within 2% error when compared to engine manufacturer performance data. The take off and climb net thrust was in general predicted with less than 5% error. The integration of the rubber engine model with the MDO framework was started and it was demonstrated that the model can run within the MDO software. Four different jet engine models have been prepared for use within the optimization software. The main conclusion is that GasTurb v11 can be used to make accurate jet engine performance simulation models and that it is possible to incorporate these models into an MDO environment.

The noise generated by aircraft can be easily heard by those living under the flight path of passenger or cargo carriers. It is considered an environmental pollutant and is treated as such by the International Civil Aviation Organization (ICAO) who monitor and review noise levels. The ICAO imposes substantial fines on those carriers who do not adhere to the decibel limitations. With the new limit or `stage' enforced in 2006, aircraft manufacturers (including jet engine manufacturers) are seeking ways to reduce the noise created by an aircraft. A 1/150th scale model, based on the exit geometry typically found on commercial jet engines, was designed and manufactured at Warwick. The laboratory jet flow conditions operated at 0.7 Mach. The work presented in this thesis looks at the noise generated in a subsonic, co- owing jet, with particular focus given to the distribution sound sources from 5 kHz to 80 kHz (0.375 St to 6.0 St). An acoustic mirror mounted on a motorized 3-way traverse measured radiated sound in the co-flowing jet to produce 2D sound source maps. This is done using combinations of smooth cowl and chevrons for the core and bypass nozzles. For frequencies less than 30 kHz, a reduction of noise was observed using the bypass chevron nozzle compared with the bypass smooth cowl nozzle. Laser Doppler Anemometry (LDA) was used to reveal the 2D flow dynamics of the jet, supporting the acoustic distribution results with velocity profiles of the flow. The change in the flow dynamics with different nozzle combinations is discussed and different regions of the flow were identified.

This dissertation seeks to merge the ideas from robust control theory such as H-Infinity control design and the Small Gain Theorem, L stability theory and Lyapunov stability from nonlinear control, and recent theoretical achievements in adaptive control. The fusion of frequency domain and linear time domain ideas allows the derivation of an H-Infinity Norm Minimization Approach (H-Infinity-NMA) for adaptive control architecture that permits a control designer to simplify the adaptive tuning process and tune the uncertainty compensation characteristics via linear control design techniques, band limit the adaptive control signal, efficiently handle redundant actuators, and handle unmatched uncertainty and matched uncertainty in a single design framework. The two stage design framework is similar to that used in robust control, but without sacrificing performance. The first stage of the design considers an ideal system with the system uncertainty completely known. For this system, a control law is designed using linear H-Infinity theory. Then in the second stage, an adaptive process is implemented that emulates the behavior of the ideal system. If the linear H-Infinity design is applied to control the emulated system, it then guarantees closed loop system stability of the actual system. All of this is accomplished while providing notions of transient performance bounds between the ideal system and the true system. Extensions to the theory include architectures for a class of output feedback systems, limiting the authority of an adaptive control system, and a method for improving the performance of an adaptive system with slow dynamics without any modification terms. Applications focus on using aerodynamic flow control for aircraft flight control and the Crew Launch Vehicle.

A set of plasma based jet actuators were designed for flow control applications. The characteristics of these actuators and their flow control applications were studied experimentally in a low speed wind tunnel. A dielectric barrier discharge (DBD) based jet actuator is designed, which is made of a covered cavity with two spanwise aligned parallel slots. Two-component particle image velocimetry (PIV) measurements were conducted to determine the effect of actuator in quiescent air and on a canonical zero pressure gradient turbulent boundary layer. It was found that the designed plasma jet actuator produced a transverse jet similar to a continuously blowing jet but with no mass addition into the flow field. The device is different from a traditional alternative blowing-and-suction synthetic jet as the current jet is continuously blown. As such, the DBD based jet actuator is different from either a mass injection blowing jet actuator or a traditional diaphragm based synthetic jet actuator. The impact of the actuation with the designed actuator on the boundary layer characteristics was investigated in detail at different Reynolds numbers. Circular cylinder wake flow control using a newly designed five-electrode plasma jet actuator is also presented in this thesis. This plasma actuator configuration mounted on the cylinder model can easily produce either a downward or upward jet into the flow around the circular cylinder by simply adjusting the same five electrodes’ electrical circuits. The experiments were performed at Reynolds numbers from 7,000 to 24,000. Wake profile measurements were made to evaluate the modification to the mean and fluctuation velocities in the cylinder wake. The results shown that the cylinder wake flow and the turbulence levels in the wake were modified under the actuations, sectional drag reduction and drag increment were obtained by different actuator actuation directions. The study suggested that this new designed five-electrode actuator can be applied to practical separation suppression or enhancement control by adjusting the plasma actuator electric circuits conveniently.

The main objective of this thesis is to understand and predict jet noise installation effects for engines mounted below aircraft wings. This is done through a variety of empirical, analytical and computational methods. Aspects of the jet source are examined and a jet source model, suitable for determining installation effects is derived. As part of this research programme a novel and extensive set of model scale jet noise installation effects experiments were undertaken. These results are presented and analyzed in this thesis. A new semi-empirical method, which can readily predict installation effects for heated coaxial jets is presented and validated using experimental data. A new 3D ray theory jet propagation method for sources in a steady inhomogeneous moving medium is presented. This method is benched marked using an analytical solution of the Lilley equation. The 3-D method is further enhanced by combing it with realistic CFD jet velocity profiles, and bench marked using the data from the experimental programme