摘要 :
This paper presents a MATLAB suite of codes entitled getPROP for designing, analyzing, and optimizing low-noise signature propellers. The getPROP package has been developed to perform end-to-end analysis, from an initial propeller...
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This paper presents a MATLAB suite of codes entitled getPROP for designing, analyzing, and optimizing low-noise signature propellers. The getPROP package has been developed to perform end-to-end analysis, from an initial propeller design to a low-signature optimized configuration that meets the operational requirements. The presented getPROP code framework covers various modules: propeller design, aerodynamic database, performance, noise prediction, atmospheric attenuation, psychoacoustic, and optimization. A complete analysis with the getPROP suite is presented through the optimization of a commercial off-the-shelf APC 14" x 5.5" propeller into a low-noise signature design, thus demonstrating the software applicability for improving multi-copters propellers.
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摘要 :
The most common rocket nozzle has an axisymmetric, convergent-divergent shape. Advanced rocket motor nozzles aspire to improve the rocket motor performance by various means or nozzles of non-conventional geometries. An experimenta...
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The most common rocket nozzle has an axisymmetric, convergent-divergent shape. Advanced rocket motor nozzles aspire to improve the rocket motor performance by various means or nozzles of non-conventional geometries. An experimental investigation was conducted along with CFD analysis to study the effect of changing the rocket motor nozzle cross section from round to rectangular on its ballistics performance.
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摘要 :
The most common rocket nozzle has an axisymmetric, convergent-divergent shape. Advanced rocket motor nozzles aspire to improve the rocket motor performance by various means or nozzles of non-conventional geometries. An experimenta...
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The most common rocket nozzle has an axisymmetric, convergent-divergent shape. Advanced rocket motor nozzles aspire to improve the rocket motor performance by various means or nozzles of non-conventional geometries. An experimental investigation was conducted along with CFD analysis to study the effect of changing the rocket motor nozzle cross section from round to rectangular on its ballistics performance.
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摘要 :
The present paper is focused on the complex task
of design and optimizing a compound helicopter
configuration. The analysis is founded on the
“Drag vs. Power Chart” methodology that enable
the separation of the rotors, thrus...
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The present paper is focused on the complex task
of design and optimizing a compound helicopter
configuration. The analysis is founded on the
“Drag vs. Power Chart” methodology that enable
the separation of the rotors, thrusters, wings and
fuselage contributions and understanding their
optimal combination in a generic compound con-
figuration. The paper also supplies an optimiza-
tion process which is based on a comprehensive
and detailed nonlinear free-wake analysis of a
compound configuration that includes a thruster
and fixed wings. The configurations on the re-
sulting Pareto frontier show design trends and
trade-offs between configurations that are more
efficient in hover and those that are more efficient
in high speed forward flight. The paper also in-
troduces analytical insight into the effect known
as lift offset which is an important design feature
in coaxial configurations. This effect may be of
advantage in terms of power consumption when
configurations that consists of two main rotors
(coaxial, tandem etc.) are operated at high speed
forward flight.
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摘要 :
The present paper is focused on the complex task of design and optimizing a compound helicopter configuration. The analysis is founded on the “Drag vs. Power Chart” methodology that enable the separation of the rotors, thrusters...
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The present paper is focused on the complex task of design and optimizing a compound helicopter configuration. The analysis is founded on the “Drag vs. Power Chart” methodology that enable the separation of the rotors, thrusters, wings and fuselage contributions and understanding their optimal combination in a generic compound con- figuration. The paper also supplies an optimiza- tion process which is based on a comprehensive and detailed nonlinear free-wake analysis of a compound configuration that includes a thruster and fixed wings. The configurations on the re- sulting Pareto frontier show design trends and trade-offs between configurations that are more efficient in hover and those that are more efficient in high speed forward flight. The paper also in- troduces analytical insight into the effect known as lift offset which is an important design feature in coaxial configurations. This effect may be of advantage in terms of power consumption when configurations that consists of two main rotors (coaxial, tandem etc.) are operated at high speed forward flight.
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摘要 :
Nanosecond Pulsed High Frequency Discharges (NPHFD) are gaining popularity over conventional spark and arc discharges as they have been shown to increase energy efficiency, enhance ignition probability and sustained kernel growth,...
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Nanosecond Pulsed High Frequency Discharges (NPHFD) are gaining popularity over conventional spark and arc discharges as they have been shown to increase energy efficiency, enhance ignition probability and sustained kernel growth, and offer more flexibility and control for ignition applications under various conditions. Hence, it is important to determine the impact of different factors such as the optimal pulse energy, background flow conditions, inter-pulse time, mixture equivalence ratio, etc. on the success of ignition of premixed mixtures with NPHFD. This work presents a numerical investigation of the morphology of ignition kernel development with both single-pulse and multiple-pulse discharges. Nanosecond non-equilibrium plasma discharges are modeled between pin-pin electrodes in a subsonic ignition tunnel with quiescent and flowing premixed mixtures of methane and air. Large eddy simulations (LES) are conducted to investigate the reasons for successful and failed ignition in different scenarios. A single pulse discharge in the presence of electrodes, in a quiescent medium, elucidates the gas recirculation pattern caused by the plasma pulse which results in a separated toroidal kernel from the primary ignition kernel between the electrodes. Convection heat loss to the mean flow results in quenching of the high temperature, radical-rich hot-spots creeping on the electrode walls, and leaving only the semi-toroidal kernel to propagate downstream. Finally, simulations with multiple pulses with different inter-pulse times have been conducted to analyze the synergistic effect of overlapping kernels with high temperature and OH concentration, which has been attributed as the primary reason for higher ignition probabilities in the "fully coupled" regime reported in the experiments. Successful ignition kernel formation is reported with 3 pulses at a pulse repetition frequency of 300 kHz in the fully coupled regime. This kernel volume was almost 4 times, and develops in two-thirds the time, compared to the ignition kernel volume formed by the single pulse discharge with the same total energy. Ten pulses with twice as much total energy were deposited at a much lower frequency of 2 kHz, which resulted in disjoint hot-spots that fail to form an ignition kernel in the decoupled regime.
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摘要 :
Nanosecond Pulsed High Frequency Discharges (NPHFD) are gaining popularity over conventional spark and arc discharges as they have been shown to increase energy efficiency, enhance ignition probability and sustained kernel growth,...
展开
Nanosecond Pulsed High Frequency Discharges (NPHFD) are gaining popularity over conventional spark and arc discharges as they have been shown to increase energy efficiency, enhance ignition probability and sustained kernel growth, and offer more flexibility and control for ignition applications under various conditions. Hence, it is important to determine the impact of different factors such as the optimal pulse energy, background flow conditions, inter-pulse time, mixture equivalence ratio, etc. on the success of ignition of premixed mixtures with NPHFD. This work presents a numerical investigation of the morphology of ignition kernel development with both single-pulse and multiple-pulse discharges. Nanosecond non-equilibrium plasma discharges are modeled between pin-pin electrodes in a subsonic ignition tunnel with quiescent and flowing premixed mixtures of methane and air. Large eddy simulations (LES) are conducted to investigate the reasons for successful and failed ignition in different scenarios. A single pulse discharge in the presence of electrodes, in a quiescent medium, elucidates the gas recirculation pattern caused by the plasma pulse which results in a separated toroidal kernel from the primary ignition kernel between the electrodes. Convection heat loss to the mean flow results in quenching of the high temperature, radical-rich hot-spots creeping on the electrode walls, and leaving only the semi-toroidal kernel to propagate downstream. Finally, simulations with multiple pulses with different inter-pulse times have been conducted to analyze the synergistic effect of overlapping kernels with high temperature and OH concentration, which has been attributed as the primary reason for higher ignition probabilities in the "fully coupled" regime reported in the experiments. Successful ignition kernel formation is reported with 3 pulses at a pulse repetition frequency of 300 kHz in the fully coupled regime. This kernel volume was almost 4 times, and develops in two-thirds the time, compared to the ignition kernel volume formed by the single pulse discharge with the same total energy. Ten pulses with twice as much total energy were deposited at a much lower frequency of 2 kHz, which resulted in disjoint hot-spots that fail to form an ignition kernel in the decoupled regime.
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