Browse Topic: Containers
ABSTRACT This paper addresses the problem of active stabilization of slung loads at high speed flight. To demonstrate the method, simulations of a utility helicopter with a dynamic inversion controller (as its automatic flight control system) and a CONEX cargo container were used. An airspeed scheduled controller utilizing cable angle feedback was designed for the nonlinear coupled system by the classic root locus technique. Nonlinear simulations of straight and level flight at different airspeeds were used to validate the controller performance in stabilizing the load pendulum motions. Controller performance was also evaluated in complex maneuvers with different levels of turbulence. The results show that the use of cable angle feedback provides or improves system stability when turbulence is not included in the simulation. When light/moderate turbulence is present sustained limit cycle oscillations are avoided by the use of the controller. For severe turbulence levels, the controller did not provide any significant improvement.
ABSTRACT Helicopter Sling Load is the most accurate form of aerial delivery in the military due to the ability to air land materiel in an exact location; however, some missions have a tendency for the payloads to become unstable due to both pilot-in-the-loop and aerodynamic effects. Past research demonstrated that allowing the container to rotate freely in yaw stabilizes pendulum motions. Other research utilized rigid fins affixed to the rear of the container. These methods work during tests; however, they become difficult to use in an operational environment. This paper discusses tests using a flexible fabric stabilizer that can be temporarily added to any payload. The flight tests were conducted Moffett Field, CA using the same payload as the previously mentioned research. Tests showed the flexible stabilizer provided an intermediate level of performance eliminating sling wind up and stabilizing pendulum motions out to the aircrafts’ power limit in exchange for very little operational overhead.
Disasters, both natural and man-made, occur every year and can significantly impact a population near the disaster site. In some disasters, ground lines of communication and transportation may be damaged or destroyed making it impossible to quickly deliver aid via traditional methods. Aerial delivery provides humanitarian aid response within hours following a disaster. The currently utilized solutions present significant risk of injury to the underlying population from the descending items. Delivering a substantial volume of aid in a single container also raises concerns that the strong or weapon-wielding population will take control of the container and ration out the aid as they see fit. The goal of this paper is to document the design, development and testing of a helicopter delivery system that will deliver food and water over a population and significantly reduce the risk of injury from dispersed aid items over the population.
The general problem of measuring bluff-body aerodynamic load maps is considered, and simplified using a Fourier series representation Six-component aerodynamic load coefficients have been measured in a low-speed wind tunnel with 1 degree azimuthal resolution, about the needed axes for over 30 models using the Continuous Rotation method. Test cases include both explorations on practical vehicle shapes, and systematic parameter variations on canonical shapes, including open and closed cylinders, flat and long rectangular containers. From the load maps for different aspect ratios, different approaches to interpolation and generalization are considered. Interpolating Fourier coefficients proves to be efficient and accurate. The efficacy of such interpolation is shown where the aerodynamics on an empty engine canister are quickly estimated by reference to the interpolated data for a circular cylinder of aspect ratio 1.9. The possibility of using combinations of canonical shapes to approximate the load map for a complex object such as a road vehicle, is also seen from the success of a combination of airloads for a cylinder and rectangular box, in approximating several of the aerodynamic load coefficient variations for a road vehicle model.
This invention accommodates the volume expansion and contraction of water ice as it freezes and thaws, thus enabling the use of water as a phase change material (PCM) for thermal energy storage. Due to the relatively large volume expansion of water upon freezing, and the relatively large bulk modulus of elasticity of ice, it is imperative to accommodate the volume expansion in order to prevent rupture of the containment vessel. In addition to accommodating the volume expansion associated with the phase change from liquid water to solid ice, this invention is usable at temperatures as low as –150 °C, thus enabling the ice to be super-cooled for additional sensible thermal storage capacity. Finally, this invention operates independent of gravity, enabling its use in space applications.
Items per page:
50
1 – 50 of 266