Patent Description:
The United States Energy Information Administration has released data showing that the transportation of people and goods accounts for about <NUM> percent of all energy consumption in the world and that passenger transportation, in particular light-duty vehicles, account for the most transportation energy consumption. The share of transport in world energy consumption is expected to increase to <NUM> percent by <NUM>.

Self-generation of energy by transport vehicles using solar energy will reduce transport's foot print in the consumption of world energy. Another major drain on energy utilization in transport vehicles is aerodynamic drag. Depending on the geometry of a vehicle, aerodynamic drag may account for as high as <NUM>% of its energy consumption. Reduction in aerodynamic drag would significantly reduce the environmental footprint of transport vehicles and result in major cost and environmental benefits due to reduced fuel consumption.

Prior art arrangements have been provided for reducing drag for an object comprising a vehicle of a given shape. A few of such type of arrangements include creating a plasma between a surface on the object and an area of laminar flow above the object.

Historically, plasma actuators have had very limited success in flow control due to a number of factors. The structure for any given drag-reducing unit based on traditional plasma actuators does not allow for seamless integration in a number of vehicle geometries. None of the prior art uses sensors to judge flow separation in a transport vehicle in real time. Neither do these take into account the most fundamental contributing factors to aerodynamic drag including vehicle speed, atmospheric temperature, coefficient of drag, Reynolds number, relative humidity, surface area of the transport vehicle, air pressure, and its reduction based on any one or more of these parameters. For example, it was determined that the creation of plasma on the surface of transport vehicles at low speeds, e.g., less than <NUM> mph, increased drag for most transport vehicle geometries. However, almost all prior art supports the activation of plasma actuators as soon as the vehicle starts moving.

DBD plasma actuators have a high electrical energy consumption that overrides the saved power from the skin-friction drag reduction. However, if an efficient design of DBD plasma actuators is used, then substantial power saving is achievable. Prior art has not been able to specify that efficient design as yet.

Active flow control technologies have not yet been adopted in controlling aerodynamic drag essentially due to the disorderly nonlinear nature of the key physical processes and because of the difficulty in monitoring or estimating the chaotic flow status and parameters accurately, resulting in a very challenging optimal control problem. Many other factors regarding deployment of actuators for drag reduction have not been considered by the prior art.

The ability of traditional plasma actuators in flow control at highway speeds is practically non-existent. Successful demonstration of vehicular drag reduction using plasma actuators at highway speeds has as yet not been reported.

<CIT> discloses a surface plasma actuator having a conducting wire attached to a surface of a target object and electrically insulated from the target object. Surface plasma is generated adjacent to the conducting wire by applying a pulse voltage to the conducting wire. This arrangement is particularly suited to the vanes in gas turbines. The wire structure is not suited for incorporation in transport vehicles.

<CIT> discloses a system, for controlling aerodynamics of a vehicle comprising multiple pairs of opposing plasma actuators positioned at lateral positions on an underside of the vehicle, wherein each pair of opposing plasma actuators comprises two electrodes. The plasma actuator may be configured as a small strip, similar in thickness to a strip of aluminum foil, having or connected to a glue layer for easy attachment to a transport vehicle body, and then connected to a power source. The plasma actuator is not interacting with another body component integral with the shape of a vehicle.

<CIT> discloses a plasma actuator including a first electrode disposed on a substrate, covered by a dielectric layer, and a second electrode disposed on the dielectric layer. The plasma actuator creates a plasma region, altering air flowing over the actuator. A particular structure for reducing drag is not shown.

Prior art arrangements have also been provided for directing electric current generated by photovoltaic cells to the transport vehicle. Most of these are restricted to the roof or part of the roof of the vehicle while some other structures do not blend seamlessly into the shape of the vehicle and increase aerodynamic drag. Also, the photovoltaic cells in most of these structures are single cell with a maximum theoretical efficiency of about only <NUM>%. The solar arrays in prior art are not concealed and do not blend-in with the rest of the surface of the vehicle and early adoption was inhibited because of aesthetic reasons.

<CIT> discloses a solar cover for a motor vehicle for the roof only with a transparent cover.

<CIT> discloses a solar cover for a motor vehicle for the roof only with a carrier plate with a plurality of photovoltaic cells and a cover plate.

<CIT> discloses a solar module for mounting on motor vehicles, which is provided with a top cover layer and a bottom cover layer, between which a solar generator is embedded which has plurality of electrically interconnected photovoltaic cells.

<CIT> discloses solar roof for motor vehicles with a solar generator having photovoltaic cells for supplying power to a power consumer and/or a battery and with a DC converter for impedance matching between the solar generator and the consumer and/or battery.

<CIT> discloses a vehicle roof with at least one cover that, alternatively, closes or at least partially opens an opening in a fixed roof surface of the vehicle, carries a solar power source for supplying power to at least one power consuming device.

<CIT> discloses a solar roof for motor vehicles having a cover with photovoltaic cells which are located between an outside cover plate and inside covering, at least one power consumer which is separate from the solar cover.

<CIT> discloses a plasma spoiler mounted in a rear portion of a vehicle for exerting a force on a passing air flow. A controller in communication with a speed sensor is provided to control a switch to activate the plasma spoiler only when the vehicle exceeds a trigger speed.

An apparatus for reducing drag in a transport vehicle is set out in independent claim <NUM>. Preferred/optional features are set out in dependent claims <NUM> to <NUM>.

A method for reducing drag and increasing energy efficiency of a transport vehicle is set out in independent claim <NUM>. Preferred/optional features are set out in dependent claims <NUM> to <NUM>.

The apparatus and method are provided in a transport vehicle cover which reduces energy consumption through significant reduction in aerodynamic drag. The vehicle cover also generates solar energy to augment other sources of energy as fuel for the vehicle. The vehicle cover has the shape that conforms to the exterior surface sections of the vehicle. It either completely replaces the respective part or mates with and overlaps it thereby retaining the original form, shape, and contour of the vehicle. For aesthetic reasons, the vehicle cover conceals every element embedded in it so that it does not stand out from the rest of the vehicle. More than one drag-reducing panel may be integrated into various sections of a transport vehicle body. Single or combinations of drag-reducing panels may be activated to provide various drag reduction results. Fiber Bragg grating (FBG) sensors, surface dielectric barrier discharge (DBD) plasma actuators, and solar arrays based on multi-junction photo-voltaic cells, are embedded in the vehicle cover at pre-determined locations based on the geometry of the transport vehicle. The operation of the drag-reducing panel is based on an adaptive, predictive, real time closed loop feedback control system. Data from the fiber Bragg grating (FBG) sensors is used to judge flow separation in real time. This information is used to activate the DBD plasma actuators to induce tangential jets to delay flow separation, thereby reducing pressure drag. The plasma actuator is activated at an unsteady actuator frequency that is determined based on the speed of the transport vehicle and the distance of the actuator electrode from the trailing edge of the vehicle. Output from the fiber Bragg grating (FBG) sensors is used in the selection of a DBD plasma actuator or a group of DBD actuators that are to be activated for optimizing drag reduction.

Another group of DBD actuators is embedded in the vehicle cover and is configured to generate span-wise travelling waves to reduce skin-friction drag whenever the vehicle speed exceeds a pre-determined threshold.

The embedded solar arrays in the vehicle cover charges the vehicle whenever these are exposed to natural sunlight or incandescent light. The solar arrays, the DBD plasma actuators and the fiber Bragg grating (FBG) sensors do not share the same space on the vehicle cover.

It has been determined that activation of DBD plasma actuators at speeds less than <NUM> mph increases drag for most transport vehicle geometries. The system is, thus, preferably programmed to function only when the vehicle speed exceeds a predetermined threshold.

It is noted, the use of the DBD plasma actuators is not essential with respect to reducing drag under all conditions.

The world is currently not on track to meet the main energy-related components of the Sustainable Development Goals (SDGs), agreed by <NUM> countries in <NUM>. The International Energy Agency's (IEA) Sustainable Development Scenario (SDS) outlines a major transformation of the global energy system, showing how the world can change course to deliver on the three main energy-related SDGs simultaneously.

These include a growing electrification of energy systems fueled by rapidly decreasing costs, deployment of clean energy technologies, and the halving of energy-related CO2 emissions by <NUM>.

Transport vehicles which reduce energy consumption through drag reduction and generate solar energy to augment other sources of energy for fuel at the same time hold the key in the achievement of IEA's Sustainable Development Goals (SDGs).

A general description of the phenomenon of drag is presented first. Drag refers to forces that oppose the relative motion of an object through a fluid, for example air.

Drag depends on the transport vehicle speed, air density, size, shape, and geometry of the body, and its surface area. One way to deal with such complex interrelated dependencies is by distinguishing the dependence by a single variable called the drag coefficient, represented as "Cd. " This allows expression of all the factors into a single equation. <MAT> where:.

Drag coefficient is mostly determined experimentally using a wind tunnel. The average modern transport vehicle achieves a drag coefficient of between <NUM> and <NUM>. For a given shape, drag coefficient is substantially fixed. Air density is a function of air pressure, temperature, and relative humidity. Reynolds number is a dimensionless quantity that can help predict flow patterns in different fluid flow situations. At low Reynolds numbers, flows tend to be dominated by laminar sheet-like flow, while at high Reynolds numbers turbulence results from differences in the fluid's speed and direction, which may move against the overall direction of the flow. These are called eddy currents and use up energy in the process.

A key component of the present subject matter is the string-type surface DBD plasma actuator. It can be used very effectively in manipulating the air flow over any surface. The string-type DBD plasma actuator is used in the present embodiments and can be designed to follow the shape of any thermodynamic body. It is mounted in a recess in the surface of the vehicle cover to which it is applied; essentially flush to the surface. It uses very low energy and generates nonthermal plasma which may be used over temperature sensitive surfaces to enable significant boundary layer modifications. Boundary layer modifications can effectively prevent flow separation reducing aerodynamic drag. It can also reduce skin-friction drag by oscillating the flow in a span-wise direction. DBD plasma actuators exhibit low weight, non-moving parts, and when switched off have a non-existent aerodynamic signature. DBD actuators may be positioned over aerodynamic surfaces in span-wise and stream-wise directions. In the former, the induced body force is in the same direction as the incoming flow. Span-wise oscillation is one of the most effective techniques in wall turbulence control, with as much as <NUM>% reduction in skin-friction drag. In the latter, induced thrust is perpendicular to the free stream direction. In this case, the composition of these two flows produces vorticities propagating in the downstream direction.

The plasma actuators in the specific embodiments within this application preferably use ±<NUM> volts DC. <NUM> volts DC which is available in most transport vehicles is converted to ±<NUM> volts DC by using a standard DC 12V to DC 24V step-up converter. From a health and safety perspective, voltage is applied to an encapsulated electrode and the exposed electrode is grounded. Additional insulation is inserted to enable use of the actuators on metallic structures. Another key component of the present embodiment is the fiber Bragg grating (FBG) sensor. FBG sensors are preferred for this application due to their miniature size, high sensitivity, higher accuracy, longer stability, corrosion resistance, wide operational range, multiplexing capabilities, immunity to electrical and magnetic fields, and the ability to measure ultra-highspeed events. It is a type of distributed Bragg reflector constructed in a short segment of optical fiber that reflects particular wavelengths of light and transmits all others. This is achieved by creating a periodic variation in the refractive index of the fiber core, which generates a wavelength-specific dielectric mirror. It reflects a wavelength of light that shifts in response to variations in temperature and/or strain.

In the present example the FBG sensor is attached to the interior surface near the base of a cantilever beam on the pressure surface of a symmetrical airfoil installed at a trailing edge of the transport vehicle to judge flow separation in real time. When a cantilever tip is vibrated by the flow near the trailing edge of the symmetrical airfoil, the strain at a cantilever base is reflected in the form of Bragg wavelengths detected by the FBG sensor. The sensor calculates flow separation in real time by calculating running standard deviations in the Bragg wavelength detected by it.

Two of the design objectives of the present subject matter are:.

In one embodiment an apparatus and a method are provided. The present embodiment comprises a transport vehicle cover that reduces aerodynamic drag by utilizing an adaptive, predictive, real time closed loop feedback control system for inhibiting flow separation based on fiber Bragg grating (FBG) sensors and dielectric barrier discharge (DBD) plasma actuators. The vehicle cover also generates electricity using solar energy to charge the onboard battery racks utilizing concealed solar arrays embedded with multi-junction photovoltaic cells to augment its primary source of energy. The vehicle cover has a shape that conforms to the exterior surface sections of the transport vehicle, so that it either completely replaces the respective part or mates with and overlaps it, thereby retaining the original form, shape, and contour of the vehicle.

More than one drag-reducing panel may be integrated into various sections of a transport vehicle body. Single or combinations of drag-reducing panels may be activated to provide various drag reduction results.

Fiber Bragg grating (FBG) sensors were selected for the current embodiments for judging flow separation in real time. The rationale for the selection of the FBG sensors for the present embodiments was that these are completely immune against electromagnetic interference and run without electric power at the measurement site. The FBG sensors exhibit high corrosion and humidity resistance, show good long-term signal stability, have the fastest response times, and are very sensitive to strain.

Fiber Bragg grating (FBG) sensor is a microstructure that is photo-inscribed in the core of a single-mode optical fiber (SMF). This is done by crosswise illumination of the fiber with a UV laser beam and using a phase mask to generate an interference pattern in its core. This brings about a permanent change in physical characteristics of a silica matrix. This change comprises a spatial periodic modulation of the core index of refraction that creates a resonant structure.

An FBG has unique characteristics to perform as a strain sensor. For example, when the fiber is stretched or compressed, the FBG will measure strain. This happens because the deformation of the optical fiber leads to a change in the period of the microstructure and of the Bragg wavelength.

Fiber Bragg grating (FBG) sensors, surface dielectric barrier discharge (DBD) plasma actuators and solar arrays based on multi-junction photovoltaic cells, are embedded in the vehicle cover at pre-determined locations based on the geometry of the transport vehicle. The operation of the drag-reducing panel is based on a real time closed loop feedback control system. Data from the fiber Bragg grating (FBG) sensors embedded in the symmetrical airfoil installed at the trailing edge of the transport vehicle is used to sense flow separation in real time. This information is used to activate the DBD plasma actuators to induce tangential jets to delay flow separation, thereby reducing drag. Output from the fiber Bragg grating (FBG) sensors is used in the selection of a DBD plasma actuator or a group of DBD actuators that are to be activated for optimizing drag reduction.

The embedded, concealed solar arrays in the vehicle cover charge the vehicle when exposed to natural sunlight or incandescent light. The solar arrays, the DBD plasma actuators, and the fiber Bragg grating (FBG) sensors do not share the same space on the vehicle cover.

It has been determined in accordance with the current subject matter that activation of DBD plasma actuators at speeds less than <NUM> mph increases drag for most transport vehicle geometries. The system may be programmed to function only when the vehicle speed exceeds a predetermined threshold, for example <NUM> mph.

The present subject matter is described in sufficient detail below with reference to the diagrams so that any person of ordinary skill in the pertinent art could make and use the invention without extensive experimentation. The best mode contemplated of carrying out the invention has also been set forth. Each element in the drawings has been mentioned in the description below.

Aerodynamic drag refers to forces that oppose relative motion of an object through a fluid, for example air. Drag depends on air density; velocity of the object, air's compressibility and viscosity, size, shape, and geometry of the object and roughness of the object's surface. For transport vehicles aerodynamic drag has two major components, pressure drag and skin friction drag.

<FIG> is a diagram illustrating an example of the phenomenon of aerodynamic drag. Pressure drag is caused by the air particles being more compressed on the front-facing surface <NUM> of a moving object <NUM>, moving in a "forward" direction <NUM>. Laminar air flow layers <NUM> pass over the moving object <NUM>. The laminar airflow layers <NUM> collectively comprise fluid flow. An air flow layer <NUM> adjacent to an upper surface of the moving object <NUM> is a boundary layer <NUM>. The layers <NUM> are more widely spaced behind a back surface <NUM> of the moving object <NUM>. Flow separation layer <NUM> which is behind the back surface <NUM> creates a low-pressure area <NUM> in a wake <NUM> with eddy currents <NUM> having a high kinetic energy. This low-pressure area <NUM> and the eddy currents <NUM> create a suction effect that tends to pull the moving object <NUM> backwards. The force produced by the suction effect is called pressure drag and is a key component of aerodynamic drag. If formation of the flow separation layer <NUM> is inhibited by any means it reduces the area of low pressure in the wake <NUM> and inhibits the creation of pressure drag. Skin friction drag is caused by the friction of a fluid against a surface of an object that is moving through it. It is directly proportional to an area of the surface in contact with the fluid and increases with the square of the velocity. The present subject matter inhibits formation of the separation layer at highway speeds and disables the actuator when the actuator could increase drag at slow speeds below a particular threshold level.

<FIG> is an exploded view of an exemplary transport vehicle <NUM> illustrating vehicle cover components. Aerodynamic drag is reduced by placement of drag-reducing solar arrays <NUM> (<FIG>) in body components. An exemplary set of drag reducing solar panels is articulated below. The drag reducing solar panel conceals the solar array <NUM> embedded in it through a reinforced colored glass top, the photovoltaic cell array of matching color, and a light absorbing back sheet of matching color. The drag reducing solar panel may either completely replace the respective original exterior surfaces <NUM> of the vehicle or the respective body component is formed with a recess to receive a drag-reducing solar panel. One or more drag-reducing solar panels will comprise a plasma actuator array located adjacent a position at which an undesired separation layer may be formed.

For example, a hood <NUM> receives a panel <NUM>. A driver's side front quarter panel <NUM> receives a panel <NUM>. Driver's side front and rear doors <NUM> and <NUM> receive panels <NUM> and <NUM> respectively. Passenger side front and rear doors <NUM> and <NUM> have corresponding recesses to those on the driver's side doors. Therefore, the panels <NUM> and <NUM> are illustrative of the panels in the doors <NUM> and <NUM>. Similarly, a driver side rear quarter panel <NUM> receives a panel <NUM>. The panel <NUM> is also illustrative of a panel received in a passenger side rear quarter panel. The roof <NUM> receives a panel <NUM>. Panel <NUM> is received in a trunk lid <NUM>. A front passenger side quarter panel has a recess which receives a panel represented by the panel <NUM>.

As further described with respect to <FIG>, Fiber Bragg grating (FBG) sensors, surface dielectric barrier discharge (DBD) plasma actuators, and solar arrays based on multi-junction photovoltaic cells, are embedded in the vehicle cover at predetermined locations based on the geometry of the transport vehicle. The operation of the drag-reducing panel is based on an adaptive, predictive, real time closed loop feedback control system. Data from the fiber Bragg grating (FBG) sensors is used to judge flow separation in real time. This information is used to activate the DBD plasma actuators to induce tangential jets to delay flow separation, thereby reducing pressure drag. The plasma actuator is activated at an unsteady actuator frequency that is determined based on the speed of the transport vehicle and the distance of the actuator electrode from the trailing edge of the vehicle. Output from the fiber Bragg grating (FBG) sensors is used in the selection of a DBD plasma actuator or a group of DBD actuators that are to be activated for optimizing drag reduction.

Another group of DBD actuators are embedded in the vehicle cover and are configured to generate span-wise travelling waves to reduce skin-friction drag whenever the vehicle speed exceeds a predetermined threshold.

The embedded solar arrays in the vehicle cover charges the vehicle whenever these are exposed to natural sunlight or incandescent light. The solar arrays, the DBD plasma actuators, and the fiber Bragg grating (FBG) sensors do not share the same space on the vehicle cover.

<FIG> is a schematic diagram of a string-type surface dielectric barrier discharge (DBD) plasma actuator <NUM>. It is mounted in a recess in a surface of one of the vehicle cover components illustrated in <FIG>, essentially flush to the surface. Each actuator <NUM> can be effectively used in the manipulation of a boundary layer, e.g., boundary layer <NUM> of <FIG>. A boundary layer is a thin layer located close to a wall of an object traveling through a fluid. Successful control of this region allows for significant drag reduction.

The string-type DBD plasma actuators <NUM> embedded in the drag reducing solar panel of the present embodiment (<FIG>) comprise two electrodes <NUM> and <NUM> offset in the chordwise direction and separated by a dielectric layer <NUM>. The encapsulated electrode <NUM> is connected to a level of reference potential, namely ground <NUM>. The exposed electrode <NUM> is attached to a voltage supply. The plasma actuators <NUM> in the present embodiment use ±<NUM> volts DC. When activated, plasma originates at the exposed electrode <NUM> and spreads out across a dielectric surface <NUM> that is above the encapsulated electrode <NUM>. This arrangement induces a tangential jet <NUM> with a strong horizontal velocity component that flows away from the exposed electrode <NUM> across the encapsulated electrode <NUM>, without the support of any moving parts.

The system sits atop an insulation layer <NUM> with a metallic blade <NUM> at the bottom. The DBD actuator <NUM> is able to follow the curvature of the surface it is applied to, is lightweight, can be switched on or off by an electronic control unit (ECU), is all-electric, can be activated at a wide range of modulation frequencies, and has a high frequency response. In order to save energy the actuator <NUM> in the current embodiment is operated in unsteady mode. The actuator <NUM> is switched on and off at a particular modulation frequency. The energy consumption in unsteady mode operation is less than <NUM> watts per meter. The frequency can range from <NUM> to <NUM>. The voltage can range from <NUM> kVpp to <NUM> kVpp.

The string-type DBD plasma actuator <NUM> used for the control of pressure drag in the current embodiment is activated at an unsteady actuator frequency that is equal to the vehicle speed in meters per second divided by the distance in meters of the plasma actuator <NUM> electrode from the trailing edge of the transport vehicle.

<FIG> is an isometric view of a multi-junction photovoltaic cell <NUM> showing successive layers partially pulled back. Each multi-junction cell <NUM> is made-up of multiple layers, each layer capturing a portion of the sunlight reaching the cell. This allows the cell to absorb light from a wide range of the solar spectrum, leading to better efficiency. A multi-junction photovoltaic cell is a stack of individual single-junction cells in descending order of bandgap. The top cell layer <NUM> captures light with the shortest wavelengths having the highest energies and passes the rest of the photons on to be absorbed by lower-bandgap cells <NUM> and <NUM>. Multi-junction cells are arranged in a series configuration to form a module <NUM> (<FIG>) and modules <NUM> are then connected in parallel-series configurations to form arrays <NUM> (<FIG>). A layer <NUM> is an n type silicon layer. Layer <NUM> is a p type silicon layer. The layer <NUM> and the layer <NUM> provide a p-n junction. A backing layer <NUM> insulates the cell <NUM>.

<FIG> is a is a plan view of a multi-junction photovoltaic cell <NUM>, the placement of the cell <NUM> in a module <NUM> with multiple multi-junction photovoltaic cells, and the placement of the module <NUM> in a solar array <NUM>.

<FIG> is a diagram illustrating an exploded view of layers of a vehicle cover having the solar array <NUM> embedded in it. The vehicle cover conceals the elements of the solar panel embedded in it through a colored reinforced glass top <NUM>. The photovoltaic layer <NUM> comprises a plurality of multi-junction photovoltaic cells <NUM> (<FIG>). Layer <NUM> is an encapsulant. Layer <NUM> is a substrate. Layer <NUM> is a cover film. Layer <NUM> is the seal. Layer <NUM> is the gasket. Layer <NUM> is the back sheet. Connection to the power system is provided by a DC connector <NUM>. The reinforced glass top sheet <NUM>, the photovoltaic layer comprising plurality of multi-junction photovoltaic cells <NUM>, and the back sheet <NUM> all have the same color as that of the vehicle to ensure that the solar energy generation components within the vehicle cover remain concealed and do not stand out from the rest of the vehicle.

<FIG> is a schematic diagram of the electronic circuit <NUM> including connectivity between elements of a solar energy generation system. First and second solar arrays <NUM> and <NUM> generate DC electricity which is routed to an on-board battery rack <NUM> through the DC combiner box <NUM>. A standard DC 12V to DC 24V step-up converter <NUM> is used to convert <NUM> V DC to ±<NUM> V DC which is routed to a drag-reducing closed loop system <NUM> through an electronic control module (ECM) <NUM>. The drag-reducing closed loop system <NUM> is actuated as soon as it receives input from a speed sensor <NUM> indicating that the vehicle's ground speed has exceeded a predetermined threshold below which drag will be increased, for example <NUM> mph. The speed sensor <NUM> includes but is not limited to a speedometer, pitot static tubes, anemometry, or laser doppler. These sensors give an electronic signal that can be read by the electronic control module (ECM) <NUM>.

<FIG> is a diagram illustrating a symmetrical airfoil <NUM> installed at a trailing edge of a transport vehicle <NUM> and used for inhibiting formation of a separation layer. A vertical distance h of the symmetrical airfoil <NUM> from the surface of the vehicle <NUM> is less than the thickness of a laminar boundary layer <NUM> for the respective vehicle geometry calculated using the Blasius solution for laminar boundary layers over a flat plate. The distance h of the symmetrical airfoil <NUM> from the surface is less than the thickness of the boundary layer <NUM> calculated for the respective vehicle geometry and may vary between <NUM> inches to <NUM> inches for most vehicle geometries. The objective is to keep the symmetrical airfoil <NUM> just within the boundary layer <NUM> for laminar flow.

<FIG> is a diagram illustrating a cross section of the symmetrical airfoil <NUM> installed at the trailing edge of the transport vehicle <NUM>. The arrow <NUM> represents the direction of air flow when the vehicle <NUM> is moving forward. An FBG strain measurement system comprising an FBG sensor <NUM>, which can precisely detect minute elastic deformation of an optical fiber, is attached to the interior surface near the base of a cantilever beam <NUM> modeled on a pressure surface of the symmetrical airfoil <NUM>. In order to realize a fiber Bragg strain sensor, strain from the substrate needs to be fully transferred to the fiber Bragg grating. Therefore, the sensor <NUM> is tightly bonded onto the surface and the substrate strain is completely guided to the fiber. The strain at the cantilever root is reflected in the form of Bragg wavelengths detected by the FBG sensor <NUM> when the cantilever tip <NUM> is vibrated by the flow <NUM> near the trailing edge <NUM> of the symmetrical airfoil <NUM>.

The range of values for the strain reflected in the FBG sensor <NUM> when the symmetrical airfoil <NUM> is moving within the laminar boundary layer <NUM> is derived from the respective vehicle geometry in a wind tunnel simulation. Similarly, when a vehicle is in motion, flow separation is confirmed when the cantilever tip <NUM> stops vibrating by the flow <NUM> near the trailing edge <NUM> of the symmetrical airfoil <NUM>. This range of values of the FBG sensor <NUM> is also determined in a wind tunnel and noted for the respective vehicle geometry.

These values are used in the real time closed loop feedback control system <NUM> (<FIG>) to determine when flow separation occurs and when it is mitigated by the induction of tangential flow by the DBD plasma actuators as illustrated in the flowchart in <FIG>.

<FIG> is a flow chart for the closed loop control of flow separation in response to transport vehicle speed. This operation inhibits actuation of plasma actuator arrays until a vehicle reaches a speed at which drag will be reduced. An on-board electronic control module (ECM) <NUM> (<FIG>) controls the working of the closed loop feed control system <NUM> and executes activities and makes decisions as shown in <FIG>.

Operation begins at block <NUM>. At block <NUM> the output of the FBG sensor <NUM> (<FIG>) is measured to determine strain. An FBG strain measurement comprises precisely detecting minute elastic deformation of an optical fiber attached to the interior surface near the base of the cantilever beam <NUM> (<FIG>) modeled on the pressure surface of the symmetrical airfoil <NUM> installed at the trailing edge of the transport vehicle <NUM>.

At block <NUM> the strain measurement is compared to determine if the strain value falls within a preselected range of values. Being within the preselected range of values indicates that the cantilever tip <NUM> substantially stops vibrating in response to the air flow <NUM>. This condition indicates flow separation from the symmetrical airfoil <NUM>, confirming flow separation. At block <NUM> the determination is made whether flow separation has occurred. If so, operation proceeds to block <NUM>. If not, operation returns to block <NUM>. At block <NUM> activation of the embedded string-type DBD plasma actuators is initiated to induce tangential plasma jets to inhibit flow separation, thereby reducing pressure drag. Operation cycles in order to continuously monitor presence or absence of the separation layer. The operation comprises an adaptive, predictive, real time closed loop method for controlling aerodynamic drag.

<FIG> is a diagram illustrating an exemplary transport vehicle in which arrays of plasma actuators are operated in accordance with the flow chart of <FIG>. An array <NUM> is an array of string-type DBD plasma actuators <NUM> (<FIG>) embedded in the frontside of the hood <NUM> (<FIG>) of the vehicle. Since flow separation is not required to be mitigated on the hood of the car these are designed to generate span-wise travelling waves to reduce skin friction drag.

In a transport vehicle <NUM>, an array <NUM> of string-type DBD plasma actuators <NUM> (<FIG>) is embedded in the frontside of the roof <NUM> of the vehicle. Since flow separation is not required to be mitigated in the frontside of the roof <NUM> of the vehicle, these are configured to generate span-wise travelling waves to reduce skin friction drag.

It is noted that arrays <NUM> and <NUM> are activated when speed of the vehicle exceeds a predetermined threshold, for example <NUM> mph, and deactivated when the speed drops below that threshold. These are not part of the adaptive, predictive, real time closed loop feedback control system <NUM> of the present embodiment.

Array <NUM> and array <NUM> are each an array of string-type DBD plasma actuators <NUM> embedded in rear end of the roof <NUM> and front end of the trunk lid <NUM> of the vehicle, respectively. These two arrays induce tangential plasma jets to inhibit flow separation. These are part of the adaptive, predictive, real time closed loop feedback control system <NUM> for drag reduction and operate in accordance with <FIG>. These arrays are activated when the vehicle speed exceeds a predetermined threshold, for example <NUM> mph. This speed is indicated when the FBG sensor <NUM> embedded in the symmetrical airfoil <NUM> and installed at the trailing edge of the vehicle determines that flow separation has occurred.

Airfoil <NUM> is a symmetrical airfoil installed at a trailing edge of the transport vehicle <NUM> with the FBG sensor <NUM> embedded in it. These arrays are activated at a frequency equal to the speed of the vehicle in meters per second divided by the distance from the actuator <NUM> electrode to the trailing edge of the vehicle in meters. The onboard electronic control module (ECM) <NUM> (<FIG>) controls the working of the closed loop feed control system <NUM> and executes activities and makes decisions in compliance with <FIG>.

All the remaining surface of the vehicle excluding the front windshield, rear windshield, and windows are embedded with concealed solar arrays.

The present embodiment will enable cars, trucks, and trains to generate their own power through solar energy. The product will also enable these vehicles to reduce aerodynamic drag thereby increasing their range and lowering their fuel consumption by as much as <NUM>%. A formula determines the optimum frequency of the actuators based on their distance from the trailing edge of the vehicle as well as the speed of the vehicle to maximize drag reduction.

In the foregoing detailed description, the apparatus of the present invention has been described with reference to specific exemplary embodiments thereof. It will, however, be evident that various modifications and changes may be made thereto without departing from the broader scope of the present invention, which is defined solely by the appended claims.

Claim 1:
Apparatus for reducing drag in a transport vehicle (<NUM>) having an exterior surface (<NUM>) and comprising a first dielectric discharge barrier plasma actuator (<NUM>) for providing a plasma jet (<NUM>), at least one solar array (<NUM>), an electronic control module (<NUM>) and a sensor (<NUM>) for actuating said dielectric discharge barrier plasma actuator (<NUM>) wherein said apparatus further comprises a cover component (<NUM>) formed to be integral with said exterior surface (<NUM>) and disposed in registration with an area of said exterior surface (<NUM>) and wherein said solar array (<NUM>) is included in said cover component (<NUM>); said dielectric discharge barrier plasma actuator (<NUM>) being positioned to provide a plasma jet (<NUM>) over the exterior surface (<NUM>) of said transport vehicle (<NUM>) when actuated; and wherein the electronic control module (<NUM>) and the sensor (<NUM>) are coupled for actuating said dielectric discharge barrier plasma actuator (<NUM>) at an unsteady actuator frequency determined based on the speed of a transport vehicle (<NUM>) and the distance of the said dielectric discharge barrier plasma actuator electrode from the trailing edge of the transport vehicle (<NUM>) in response to a preselected set of conditions including the transport vehicle speed exceeding a predetermined threshold below which drag will increase.