Browse Topic: Vehicle performance
Rotors and propellers in edgewise flight typically encounter reverse-flow on the retreating blade, especially when operating at low rotational speeds and high speed flight. This phenomenon is well known and has been observed in rotorcraft and vertical take-off and landing (VTOL) applications, with impacts on vehicle performance and aerodynamic loads. Reverse flow is characterized by flow incident to the trailing edge of an airfoil with an angle of attack (AoA) of around 180°. Aerodynamic coefficients for reverse flow conditions are difficult to find in literature, and wind tunnel measurements often focus on the normal operating range of airfoils. This study investigates the fundamental aerodynamic characteristics of airfoils in reverse flow using high fidelity computational fluid dynamics, and analyzes the impact of using accurate aerodynamic coefficients on comprehensive rotorcraft analysis. Although the effect on flight performance is well understood, for applications on lift rotors
Electrification could improve full-size rotorcraft performance by reducing peak turbine power demand, reducing transmission system weight and complexity, and reducing operating costs. Integrating electric machines with mechanical powertrains requires careful consideration of the system-level weight and efficiency impacts. This paper presents an optimization framework for evaluating parallel hybrid powertrain configurations using Geometric Programming (GP). Both retrofit and clean-sheet vehicle designs are considered. The results show that high-speed electric motors integrated into a parallel hybrid configuration using batteries can reduce the sized gas turbine power, enabling more efficient engine operation at lower power levels. For retrofit designs, with a fixed vehicle gross weight, adding batteries and motors reduces usable fuel, decreasing mission capability. Clean-sheet designs offer additional flexibility to re-size the vehicle and rotor, resulting in energy savings for an
The work performed for the Adaptive Resilient Engineered Structures (ARES) program sponsored by the U.S. Army constitutes a trade study and resulting proposal for a structural demonstrator platform. The trade study was conducted using the Quality Function Deployment (QFD) process and a subsequent Artificial Intelligence (AI) exercise to find clusters of technologies for structural efficiency and resilience from Boeing's internal research activities. From a selection of approximately 150 technologies at different TRLs, Boeing subject matter experts (SMEs) for structural technologies identified several characteristics that could potentially determine the development of ARES structural demonstrator. Through the QFD process, the list of technologies was down selected about 50 unique technologies for consideration. The next stage of the QFD process entailed in identifying 37 different attributes or criteria long which each of these technologies would be assessed. They were grouped under two
The influence of ground, wall, and corner boundaries on multirotor vehicle performance was investigated through a series of controlled flight tests. Changes in rotor inflow profiles were represented by near-field rotor pressure measurements captured by a custom Kiel probe wake rake. Ground effect was characterized by reduced thrust and power requirements, primarily driven by the vehicle fuselage, which induced regions of reduced pressure and increased flow unsteadiness around the airframe. Operating near a wall boundary was found to restrict airflow into the portion of the rotor disk closest to the wall, leading to increased power requirements to maintain hover and a consequent reduction in performance. While vehicle orientation had minimal impact on overall rotor performance, it did influence local rotor inflow behavior near the wall, depending on the relative position of the interaction region formed with adjacent rotors. As the vehicle descends from the isolated wall effect into
An aeromechanics analysis of a Mach-scaled rotor with lift compounding was conducted to understand the impact of various wing configurations on performance and loads. An assessment of the single retreating side wing and dual wing configurations was conducted for advance ratios up to μ = 0.7, two wing incidence angles (4° and 8°), and three rotor shaft angles (-4°, 0°, and 4°). Aircraft performance, control angles, blade structural loads, hub vibratory loads, and aerodynamic interactions between the rotor and wing were evaluated using the University of Maryland Advanced Rotorcraft Code (UMARC). Additionally, UMARC coupled rotor-wing analysis was validated with wind tunnel data of a lift and thrust compounded rotor. The study shows that the single wing configuration is beneficial for peak vehicle performance (L/D), though the dual wing configuration minimizes blade loads. The single wing configuration observed a 7% greater wing L/D than the dual wing configuration for the same 8° wing
Hybrid-electric propulsion could provide numerous benefits for full-size rotorcraft, including reduced peak turbine power demand, reduced transmission system weight and complexity, and reduced operating costs. Variable speed electric motors, furthermore, could be configured to enable continuously variable rotor speed. Achieving these benefits requires accounting for coupling between the hybrid-electric drivetrain and vehicle performance within a large, unexplored design space. This paper presents a framework for simultaneous optimization of vehicle and electrified powertrain conceptual design using Geometric Programming (GP) methods. Four hybrid-electric powertrain architectures are evaluated relative to a baseline non-electrified powertrain for single main rotor, compound coaxial-rotor, and tiltrotor configurations. For designs with an upper limit on turbine power, electrification increases the maximum cruise speed for the compound coaxial-rotor configuration. Variation of the rotor
Aerodynamic interactions impact multirotor vehicle performance throughout its entire flight envelope and change with vehicle orientation, attitude, and forward flight speed. This paper presents efforts in incorporating these interaction effects into a reduced-order numerical quadrotor model informed by experimental flight test data. The interaction model employed system identification tools to compensate for discrepancies between actual rotor performance data and a Blade Element Theory (BET) based baseline model. Incorporation of the interaction model derived from system identification techniques improved the accuracy of model predicted rotor performance. The interaction model also provided insight into interaction effects predominantly influencing rotor performance for multiple flight conditions. The results demonstrate the utility of system identification techniques for accurate multirotor modeling capabilities.
Items per page:
50
1 – 50 of 804