Search Results

Unmanned Aerial Vehicles (UAV) require simple and reliable engines of high power to weight ratio. Wankel and two stroke engines offer many advantages over four stroke engines. A two stroke engines featuring crank case scavenging, precise oiling, direct injection and jet ignition is analyzed here by using CAD, CFD and CAE tools. Results of simulations of engine performances are shown in details. The CFD analysis is used to study fuel injection, mixing and combustion. The CAE model then returns the engine performances over the full range of loads and speeds with the combustion parameters given as an input. The use of asymmetric rather than symmetric port timing and supercharging scavenging is finally suggested as the best avenue to further improve power density and fuel conversion efficiency.

Scale-resolving turbulence modeling for engine flow simulation has constantly increased its popularity in the last decade. In contrast to classical RANS modeling, LES-like approaches are able to resolve a larger number of unsteady flow features. In principle, this capability allows to accurately predict some of the key parameters involved in the development and optimization of modern engines such as cycle-to-cycle variations in a DI engine. However, since multiple simulated engine cycles are required to extract reliable flow statistics, the spatial and temporal resolution requirements of pure LES still represent a severe limit for its wider application on realistic engine geometries. In this context, Hybrid URANS-LES methodologies can therefore become a potentially attractive option. In fact, their task is to preserve the turbulence scale-resolving in the flow core regions but at a significantly lower computational cost compared to standard LES.

The high demand for traditional air traffic as well as increased use of unmanned aerial systems (UAS) has resulted in researchers examining alternative technologies which would result in safer, more reliable, and better performing aircraft. Active methods of aerodynamic flow control may be the most promising approach to this problem. Research in the area of aerodynamic control is transitioning from traditional mechanical flow control devices to, among other methods, plasma actuators. Plasma actuators offer an inexpensive and energy efficient method of flow control. Dielectric Barrier Discharge (DBD), one of the most widely studied forms of plasma actuation, employs an electrohydrodynamic (EHD) device which uses dominant electric fields for actuation. Unlike traditional flow control methods, a DBD device operates without moving components or mass injection methods.

As unmanned aerial vehicle applications continue their rise in popularity in the public and private sectors, there is an increasing demand in many cases for smaller, more efficient low speed unmanned aerial vehicles (UAVs). Although the primary drivers for the continued performance improvement of smaller UAV platforms tend to be in the areas of electronics miniaturization and improved energy storage, aerodynamics, particularly in the low Reynolds number regime, still have a significant role in the overall performance enhancement of small UAVs. This paper focuses on the study of the nearfield aerodynamic effects of a low-power active flow enhancement technique known as dielectric barrier discharge (DBD) in very low speed/low Reynolds number flows most closely associated with small and micro unmanned aerial vehicles.

In this research, the magnetoplasmadynamic (MPD) effects of applying a toroidal magnetic field around an ionized exhaust plume were investigated to manipulate the exhaust profile of the plasma jet under near vacuum conditions. Tests for this experiment were conducted using the West Virginia University (WVU) Hypersonic Arc Jet Wind Tunnel. A series of twelve N52 grade neodymium magnets were placed in different orientations around a steel toroid mounted around the arc jet’s exhaust plume. Four different magnet orientations were tested in this experiment. Two additional configurations were run as control tests without any imposed magnetic fields surrounding the plume. Each test was documented using a set of 12 photographs taken from a fixed position with respect to the flow. The photographic data was analyzed by comparing images of the exhaust plume taken 10, 20, and 30 seconds after the plasma jet was activated.

A Hybrid Projectile (HP) is a tube launched munition that transforms into a gliding UAV, and is currently being researched at West Virginia University. In order to properly transform, the moment of transformation needs to be controlled. A simple timer was first envisioned to control transformation point for maximum distance. The distance travelled or range of an HP can directly be modified by varying the launch angle. In addition, an internal timer would need to be reprogrammed for any distance less than maximum range due to the nominal time to deployment varying with launch angle. A method was sought for automatic wing deployment that would not require reprogramming the round. A body angle estimation system was used to estimate the pitch of the HP relative to the Earth to determine when the HP is properly oriented for the designed glide slope angle. It also filters out noise from an inertial measurement unit (IMU).

Initial results are reported for the effects of electrical body forces on heat transfer performance of an instrumented spray cooling experiment. Heat transfer performance is documented for ranges of electrode voltage, spray volume flow rate, and heater power level using a Thick Film Resistor heater. The heat transfer coefficient increases with increased spray flow rate, and also increases somewhat versus heat flux. Without the electrical body forces, different brass and PVC spray nozzles show significant variation in spray cooling performance (order of ±5-15%) whenever the nozzle is realigned. Changing the nozzle-to-heater spacing results in similar performance variations. Initial Kelvin force electrode designs show no improvement in heat transfer performance using FC-72, while a Coulomb force electrode geometry and a second-generation Kelvin force electrode design both show modest but consistent improvements (order of 10% in heat flux; order of 5% for Nusselt number) using HFE-7000.

Unmanned aerial vehicle (UAV) design aspects are as broad as the missions they are used to support. In some cases, the UAV mission scope can impose design constraints that can be difficult to achieve. This paper describes recent work performed at West Virginia University (WVU) to support repeated flight testing of a single-use UAV platform with emphasis on the highly specialized wings required to help meet the overall airframe mass properties constrained by the project sponsor. The wings were fabricated using a molded polyurethane (PU) foam as the base material which was supported by several different types of rigid and flexible substructures, skins, and matrix-infused fiber elements. Different ratios of infused fiber mass to PU foam were tested and additional tungsten masses were added to the wings to achieve the correct total mass and mass distribution of the wings.

Optical motion capture (OMC) is a relatively new experimental tool used in many branches of science and engineering. Despite OMC’s widespread use, literature and practical procedures on the quantification of error and uncertainty in OMC systems for rigid bodies are currently underdeveloped. However, in most studies involving error and uncertainty quantification, the OMC volumes are relatively small (maximum length of 2m in any dimension) and involve expensive experimental apparatuses. Therefore, a cost-effective procedure to quantify the positional errors and uncertainties present in a large volume OMC system is presented. The procedure utilizes the kinematics of a wooden block traveling through air to predict errors and uncertainties in the OMC system by only collecting trajectory data.

The Wankel engine for Unmanned Aerial Vehicle (UAV) applications delivers advantages vs. piston engines of simplicity, smoothness, compactness and high power-to-weight ratio. The use of computational fluid dynamic (CFD) and computer aided engineering (CAE) tools may permit to address the major downfalls of these engines, namely the slow and incomplete combustion due to the low temperatures and the rotating combustion chambers. The paper proposes the results of CAD/CFD/CAE modelling of a Wankel engine featuring tangential jet ignition to produce faster and more complete combustion.

A Hybrid Projectile (HP) is a round that transforms into a UAV after being launched. Some HP's are fired from a rifled barrel and must be de-spun and wings-level for lifting surfaces to be deployed. Control surfaces and controllers for de-spinning and wings-leveling were required for initial design of an HP 40 mm. Wings, used as lifting surfaces after transformation, need to be very close to level with the ground when deployed. First, the tail surface area needed to de-spin a 40 mm HP was examined analytically and simulated. Next, a controller was developed to maintain a steady de-spin rate and to roll-level the projectile in preparation of wing deployment. The controller was split into two pieces, one to control de-spin, and the other for roll-leveling the projectile. An adaptable transition point for switching controllers was identified analytically and then adjusted by using simulations.