A new concept in aircraft propulsion is described in this work. In particular, variable jet engine is investigated for supersonic ASTOVL aircraft. This engine is a Selective Bleed Variable Cycle, twin shaft turbofan. At low flight speeds the engine operates as a medium bypass turbofan. At supersonic cruise it operates as low bypass turbofan without reheat. The performance of the engine and its components is analyzed using a novel matching procedure. Off-design engine performance characteristics are explained, compressor running lines are shown, and variable geometry requirements are described. The performance analysis shows that fuel savings are significant, thus reducing aircraft take-off weight. The major advantage of this engine is that all the components are used continuously for all operating modes, thus incurring low weight penalties. The benefits predicted by this preliminary investigation indicate that further research on this engine should be carried out. The matching procedure developed and described shows itself to be very effective for two-shaft engines with a fixed geometry LP turbine. The method can also be extended to three shaft cases with or without a variable geometry LP turbine. Extensive development of compressor and turbine design and performance software has been undertaken.

No description available.

ABSTRACT Developments in the field of microturbine technology and gas turbine driven aircraft has been progressing without much progress in light aircraft predominantly propelled by piston engines. Because of inhibitive maintenance and overhaul costs of such however, propulsion via a gas turbine engine has been proposed with the potential of eventually replacing current engine configurations. Subsequently, the objective was to conceptually design a replacement gas turbine engine in the 150 kW range. A selection of case studies was used to illustrate the changing technologies to illustrate the technological viability of micro-gas turbines for light aircraft. Advantages and disadvantages of both engine types were discussed and a concise description of gas turbine operations and its components was given. A brief overview of fundamentals as well as the transmission layout was also supplied. Three configurations were isolated, namely the single spool design, a twin spool design featuring a free power turbine and the effect of a fuel conserving recuperator. Calculations were performed using Microsoft Excel, which proved sufficient in effectively calculating complex formulae - even under the necessary iterative feed-back conditions the design process demanded. Eventually, variable-specific design criteria were derived regarding the three engine types. Because fuel consumption still proved inhibitive, the effect of recuperation was investigated which yielded a very competitive engine - should the possibility of recuperator technology exist on time. As a result, one particular recuperated, single spool gas turbine engine was successfully identified. Having met all the design criteria sufficiently, this preliminary prototype design was numerically described and put within context of principal, peripheral working components such as a compatible gearbox layout.

The design of aircraft propulsion configurations must digress from the typical configurations that are utilized on the majority of aircraft in order to consider the effects of environmental issues as well as the noise that is generated from the engines. One unconventional approach under consideration involves rectangular jets near flat surfaces that are parallel to the jet axis. This type of configuration makes an attempt to muffle the noise that propagates to the ground, but previous experimental work showed that the noise generated by this configuration was actually increased due to the effect that the plate trailing edge exerts on the flow. In this thesis, a large eddy simulation study is conducted to determine whether wall deformations at the plate trailing edge could reduce the jet noise. A high aspect ratio rectangular nozzle is placed over a flat surface featuring sinusoidal deformations at the trailing edge. A range of amplitudes and wavenumbers, characterizing the deformations at the trailing edge, is considered to determine the parameter range that corresponds to noise reduction.

No description available.

Thesis (Ph. D.)--Aerospace Engineering, Georgia Institute of Technology, 2007. / Danielle Soban, Committee Member ; Dimitri Mavris, Committee Chair ; Alan Porter, Committee Member ; Gary Seng, Committee Member ; Daniel Schrage, Committee Member.

No description available.

No description available.

This work utilizes the small-signal impedance-based stability analysis method to develop stability assessment criteria for a single-aisle turboelectric aircraft with aft boundary-layer propulsion (STARC-ABL) system. The impedance-based stability analysis method outperforms other stability analysis methods because it does not require detailed information of individual components for system integration, therefore, a system integrator can just require the vendors to make the individual components meet the impedance specifications to ensure whole system stability. This thesis presents models of a generator, motor, housekeeping loads, and battery all with power electronics interface which form an onboard electrical system and analyzes the relationship between the impedance shape of each component and their physical design and control loop design. Based on the developed small-signal model of the turbine-generator-rectifier subsystem and load subsystem, this thesis analyzes the impact of electromechanical dynamics of the turbofan passed through the generator on the dc distribution system, concluding that the rectifier can mitigate the impact. Finally, to ensure the studied system stable operation during the whole flying profile, the thesis provides impedance specifications of the dc distribution system and verifies the specifications with several cases in time-domain simulations. / M.S. / Electric aircraft propulsion (EAP) technologies have been a trend in the aviation industry for their potential to reduce environmental emissions, increase fuel efficiency and reduce noise for commercial airplanes. Achieving these benefits would be a vital step towards environmental sustainability. However, the development of all-electric aircraft is still limited by the current battery technologies and maintenance systems. The single-aisle turboelectric aircraft with aft boundary-layer (STARC-ABL) propulsion concept is therefore developed by NASA aiming to bridge the gap between the current jet fuel-powered aircraft and future all-electric vehicles. The plane uses electric motors powered by onboard gas turbines and transfers the generated power to other locations of the airplane like the tail fan motor to provide distributed propulsion. Power electronics-based converter converts electricity in one form of electricity to another form, for example, from ac voltage to dc voltage. This conversion of power is very important in the whole society, from small onboard chips to Mega Watts level electrical power system. In the aircraft electrical power system context, power electronics converter plays an important role in the power transfer process especially with the recent trend of using high voltage dc (HVDC) distribution instead of conventional ac distribution for the advantage of increased efficiency and better voltage regulation. The power generated by the electric motors is in ac form. Power electronics converter is used to convert the ac power into dc power and transfer it to the dc bus. Because the power to drive the electric motor to provide distributed propulsion is also in ac form, the dc power needs to be converted back into ac power still through a power electronics converter. With a high penetration of power electronics into the onboard electrical power system and the increase of electrical power level, potential stability issues resulted from the interactions of each subsystem need to be paid attention to. There are mainly two stability-related studies conducted in this work. One is the potential cross-domain dynamic interaction between the mechanical system and the electrical system. The other is a design-oriented study to provide sufficient stability margin in the design process to ensure the electrical system’s stable operation during the whole flying profile. The methodology used in this thesis is the impedance-based stability analysis. The main analyzing process is to find an interface of interest first, then grouped each subsystem into a source subsystem and load subsystem, then extract the source impedance and load impedance respectively, and eventually using the Nyquist Criterion (or in bode plot form) to assess the stability with the impedance modeling results. The two stability-related issues mentioned above are then studied by performing impedance analysis of the system. For the electromechanical dynamics interaction study, this thesis mainly studies the rotor dynamics’ impact on the output impedance of the turbine-generator-rectifier system to assess the mechanical dynamics’ impact on the stability condition of the electrical system. It is found that the rotor dynamics of the turbine is masked by the rectifier; therefore, it does not cause stability problem to the pre-tuned system. For the design-oriented study, this thesis mainly explores and provides the impedance shaping guidelines of each subsystem to ensure the whole system's stable operation. It is found that the stability boundary case is at rated power level, the generator voltage loop bandwidth is expected to be higher than 300Hz, 60˚ to achieve a 6dB, 45˚ stability margin, and load impedance mainly depends on the motor-converter impedance.

Företaget BlackWing Sweden AB tillverkar ultralätta flygplan av kolfiberkomposit. Företaget vision är att tillverka ett flygplan som helt kan drivas av elektricitet med samma prestanda som flygplan drivet av fossila bränslen. För att kunna driva BlackWing flygplanet med hjälp av elektricitet behövs ett batteripaket, elektronikstyrning samt en elmotor. Därför har detta examensarbete ägnats åt att främst undersöka vilka elmotorer och battericeller som är mest lämpade för BlackWing flygplanet. Därefter togs resultatet fram genom beräkningar på battericeller och motorpaket med hjälp av insamlad information om motor-och batteriprestanda. För att få ett mer objektivt och systematiskt resultat här även en Pugh-matris används för att på ett enkelt sätt avgöra den mest lämpliga battericellen. Resultatet av detta arbete visade sig att i dagsläget är batteriet Envia, High Energi Pouch cell (ENV35011-CRC) och Siemens motor DYNADYN® 85 är mest lämpliga för BlackWing flygplanet. / BlackWing Sweden AB manufactures ultralight aircraft made from carbon fibre composite. The company's vision is to produce an aircraft that can be completely powered by electricity with the same performance as the aircraft powered by fossil fuels. To operate the BlackWing aircraft using electricity it will need a battery pack, electronic controls and an electric driveline. Therefore, this thesis has been devoted primarily to study which electric engine and battery cells that would be most suitable for the BlackWing aircraft. The result was produced by calculations of the battery cells and electric driveline by using collected information about driveline and battery performance. To get a more objective and systematic results, a Pugh matrix was used to easily determine the most suitable battery cell. The results of this work showed that in the current situation, the battery Envia High Energy Drone Cell Pouch (ENV35011-CRC) and Siemens engine DYNADYN® 85 are the most suitable for the BlackWing aircraft.