Emily D. Pertl

Circulation Control Applied to Wind Turbines

The recent rise in fuel costs and global warming concerns have re-invigorated the search for alternative energy sources. Harnessing energy from the wind is a logical alternative; however the cost and efficiency of current wind turbines is a limiting factor. The use of an augmented Vertical Axis Wind Turbines (VAWTs) may become the superior choice to the more common Horizontal Axis Wind Turbines (HAWTs) that are usually associated with the harvesting of wind energy. HAWTs operate on the same principles as large airplane propellers, while VAWTs operate on lift and/or drag principles like an airplane wing or a sail on a boat. VAWTs are currently being investigated for use with circulation control to increase their potential power output. In this paper, two topics will be presented, a comparison between VAWTs and HAWTs for rotor diameter versus key turbine aspects and the impact of VAWTs on environmental concerns, such as bat and bird populations. The Center for Industrial Research Applications (CIRA) at West Virginia University (WVU) is currently developing a concept utilizing circulation control to increase the lift to drag ratio, maximizing the beneficial forces on the VAWT blade, allowing for improved wind energy production. For the comparison between VAWTs and HAWTs, there are currently 14 companies with a total of 34 wind turbines variations representing VAWTs and 11 companies with a total of 40 wind turbines representing HAWTs. Trend studies of VAWT and HAWT diameters to cut-in-speed, rated velocity, max velocity, power output (<100 kW), and power output (≥100 kW) were created to show the potential of VAWTs. A growing concern with wind energy is the impact on bat and bird populations. It is currently believed that VAWTs reduce the impact of wind energy by altering the interaction with the wind. If these benefits can be proven, then not only are VAWTs potentially more economical, but even more eco-friendly.Copyright

Delay in Flow Separation for Circulation Controlled Cylinders

Recent circulation control testing at West Virginia University, in a closed loop wind tunnel, has been conducted on models where the trailing edge radius was selected to be smaller than that used in literature, such as Loth and Boasson [1], 1.5 inches and Englar [2], 0.4375 inches. The reduced size was chosen in an attempt to minimize the drag experienced during periods of non-activation of the circulation control, and the smaller size was more compatible to the wind tunnel test section size. However, while the drag is lessened by a smaller trailing edge, the performance of circulation control also appears to be dependent upon a multitude of variables including, but not limited to, the trailing edge radius and jet velocity. Through a modeled experiment, the two attributes that influence the circulation control performance were concurrently manipulated by varying the radius of curvature and the velocity of the blown jet. The combination of these characteristics were experimentally explored to determine the location where the jet leaves the surface of the cylinder, also known as the separation point. The optimum separation point is defined as the farthest angular displacement from the plane of the blown jet exit slot, which corresponds to the greatest increase in the circulation around the cylinder, representing the trailing edge of a circulation control airfoil. From the known radius and jet velocity, an expression that relates the separation point and the mass flow rate velocity quantity are compared. Understanding the blowing coefficient and its impact on the separation point, results in a predictive relationship between these two attributes of circulation control. The results of this two-dimensional cylinder study found that an increase in trailing edge radius decreased the location of the separation point. In addition, an increase in the jet velocity resulted in an increase in the separation point location. The combination of these two quantities produced a relationship similar to each individually, illustrated by the mass flow rate velocity value, which is the blowing coefficient excluding free stream conditions, versus the angle of separation. Data is therein compared to the theory by Newman [3], which predicts a maximum separation point location at 245 degrees beyond the jet exit plane and an increase in the separation point as the radius of curvature increases. The results of this study found a separation point maximized at 231 degrees, and, contrary to Newman [3], a decrease in the separation point was found as the radius of the cylinders increased.Copyright

Performance Predictions of a Circulation Controlled-Vertical Axis Wind Turbine With Solidity Control

Conventional straight bladed vertical axis wind turbines are typically designed to produce maximum power at tip speed ratio, but power production can suffer when operating outside of the design range. These turbines, unless designed specifically for low speed operation, may require rotational startup assistance. Circulation control methods, such as using blowing slots on the trailing edge could be applied to a Vertical Axis Wind Turbine (VAWT) blade. Improvements to the amount of power developed at lower speeds and elimination or reduction of startup assistance could be possible with this lift augmentation. Selection of a beneficial rotor solidity and control over when to utilize the blowing slots for the CC-VAWT (Circulation Controlled-Vertical Axis Wind Turbine) appears to have a profound impact on overall performance. Preliminary performance predictions indicate that at a greater range of rotor solidities, the CC-VAWT can have overall performance levels that exceed a conventional VAWT. This paper describes the performance predictions and solidity selection of a circulation controlled vertical axis wind turbine that can operate at higher overall capture efficiencies than a conventional VAWT.Copyright

Drag Reduction Methodologies for Circulation Control Applications

Circulation control technology has proven aerodynamic benefits, however, along with an increase in the coefficient of lift, parasitic drag also increases. This paper explores two drag reduction techniques investigated in order to decrease the negative effects caused by the geometric requirements of a circulation control airfoil. The first method tests the viability of inducing a constant, low exit velocity jet, similar to a “leak” from the upper and lower plenums of the blowing jets, in an attempt to find a threshold where a specific rate of leak can alleviate the adverse effects of the circular trailing edge. A second drag mitigation technique included altering the shape of the trailing edge; attached to the trailing edge of a conventional circulation control surface is a sharp trailing edge, with an inner curved channel offset. By modifying the distance between the two geometries, an ideal separation distance is identified. The aerodynamic qualities of the two test models are therein compared to conventionally shaped airfoils. The results indicate that two techniques wherein have the ability to reduce the drag, proven by empirical experimentation.

Redesign of an Adjustable Slope Moving Ground Plane Wind Tunnel

Ground effect is an aerodynamic phenomenon that occurs when moving bodies come in close proximity to the ground. A “cushion” of air is created underneath the moving body which provides additional lift by increasing the local pressure under the body surface. To experimentally test ground effect vehicles, a unique wind tunnel is currently being redesigned and constructed at West Virginia University. This wind tunnel incorporates a rotating belt as the ground plane and a centrifugal fan that generates the air flow through the test section in the same direction as the belt’s rotation. The combination of a rotating belt and airflow is used to mimic ground effect in that it is representative of a body moving through still air in close proximity to the ground. The test section and fan assembly sit on a platform that is connected to a movable base frame. The base and testing platform connect through a pivot point that is capable of being raised upward to a maximum angle of fifty degrees to account for gravitational vector alignment between modeled and real world conditions. When the platform is raised and the belt is spinning, the structure is less stable and has the potential to create errors in force readings due to these oscillations, as well as the potential to tip in extreme wind conditions. Thus, the evaluation of the original design and the subsequent redesign are addressed in this research effort. To stabilize the wind tunnel, additional structural elements have been added downstream of the test section. Two telescoping poles were added to the end of the platform that will connect onto outriggers attached to the base structure. These poles and outriggers will form an A-shape support system when the platform is raised to any degree between zero and fifty. The width of the outriggers was calculated and then modeled in conjunction with the existing base structure. The final design is presented in this paper.Copyright

Complete Command, Control, Communications, Intelligence, Surveillance, and Reconaissance System for C-130 Aircraft

Utilization of existing airframes for multi-mission capabilities has become a driving factor for defense agency sponsored research and development work. This concept stems from the obvious cost and versatility discrepancy between development of specialized aircraft for specific mission use and development of nonpermanent add-on componentry for existing aircraft. A well established and used aircraft that can benefit from nonpermanent add-on components is the C-130. With over 50 years of military theater use and well over 2000 units produced, the C-130 aircraft has both multi-agency availability and multi-mission capability to benefit from this concept. The proposed dual agency system concentrates on mission use relating to both high and low altitude surveillance and reconnaissance. The base structure of the system is a sensor deployment platform (Oculus) developed at West Virginia University and the data generation/collection/interpretation component of the system which was developed at the Air Force Research Laboratory. Each system is described individually in depth along with their role in association together. In collaboration the dual organization system provides military defense agency’s with the first nonpermanent, mobile Command, Control, Communications, Computers, Intelligence, Surveillance and Reconnaissance aircraft system.

Feasibility Analysis of an Add-On Roof System for Standard Shipping Containers

In today’s economy, rising energy costs are constantly forcing exploration into more cost effective energy solutions. With the high heat index of locations, such as Iraq and Afghanistan, the cost of cooling the working space of armed service personnel is extremely high. The Center for Industrial Research Applications (CIRA) at West Virginia University (WVU) is focused on finding a solution to this problem. The Modular Heat Roof (MHR) project is focused on supplying the military shelters with a cost-effective way to reduce the moderate to high heat loads. Research on military shelters and their energy aspects will be conducted to establish a baseline model. This study indicates that a potential 40% reduction in heat load can be realized providing as much as

Design of a Portable Micro-Dilution Tunnel Particulate Matter Emissions Measurement System

5m in energy savings for those military containers currently in use in the Middle East.

Development of a Remote Sensor Deployment System for Expanded C4ISR Use of the C-130 Aircraft

The Federal Test Procedure (FTP) for heavy-duty engines requires the use of a full-flow tunnel based constant volume sampler (CVS). These are costly to build and maintain, and require a large workspace. A small portable micro-dilution system that could be used on-board, for measuring emissions of in-use, heavy-duty vehicles would be an inexpensive alternative. This paper presents the rationale behind the design of such a portable particulate matter measuring system. The presented micro-dilution tunnel operates on the same principle as a full-flow tunnel, however given the reduced size dilution ratios can be more easily controlled with the micro dilution system. The design targets dilution ratios of at least four to one, in accordance with the ISO 8178 requirements. The unique features of the micro-dilution system are the use of only a single pump and a porous sintered stainless steel tube for mixing dilution air and raw exhaust sample. This paper contains the results of that design process.