Search Results

Aerodynamic drag is the major component of Heavy Vehicle (HV) resistance at typical highway speeds, and thus strongly impacts related fuel economy because horsepower required to overcome this drag increases as the cube of vehicle speed. In an ongoing drag-reduction program for HVs conducted for the US Department of Energy (DOE), Georgia Tech Research Institute (GTRI) has been applying advanced new aerodynamic technology previously developed for aircraft. This technology uses tangential blowing to reduce the drag generated by these bluff-based high-drag vehicles, particularly the trailer. Drag reduction can be accomplished by this blown concept without moving surfaces, and it also offers the potential to increase drag for braking if needed and to overcome both increasing drag and destabilizing side forces due to large side winds and gusts.

The current interest in Extreme STOL technology is intended to develop technology to provide future fixed-wing transport aircraft with very high lift capability for very short (<2000′) balanced-field-length operations plus efficient transonic cruise (M ∼ 0.8). However, this carries with it the need for a number of additional capabilities that could be simultaneously unobtainable if only conventional aerodynamic and control technologies are employed. These requirements include: high powered-lift values (CL∼10) with the associated low-speed moment-trim requirement; low-speed control including one-engine out; interchangeable lower drag (for cruise and climb) and increased drag (for equilibrium approach); cruise efficiency; quiet operation; leading-edge stall prevention; reduced mechanical complexity and weight; and system simplicity, reliability, and maintainability.

Blown aircraft aerodynamic technology has been developed and applied to entrain separated flow fields, significantly reduce drag, and increase the fuel economy of Heavy Vehicles and SUVs. These aerodynamic improvements also lead to increases in stability, control, braking, and traction, thus enhancing safety of operation. Wind-tunnel results demonstrating model Heavy Vehicle drag coefficient reductions of up to 84% due to blowing and related configuration improvement are reviewed herein. Data confirming the elimination of directional instability due to side-winds plus generation of aerodynamic forces which are not currently used for control of large vehicles are also shown. These data have guided the design and modification of a full-scale road-test vehicle. Initial confirmation road test results of this patented concept on the modified blown HV rig are presented. An SAE Type-II Fuel Economy test was also conducted.

Research is being conducted at the Georgia Tech Research Institute (GTRI) to develop advanced aerodynamic devices to improve the performance, economics, stability, handling and safety of operation of Heavy Vehicles by using previously-developed and flight-tested pneumatic (blown) aircraft technology. Recent wind-tunnel investigations of a generic Heavy Vehicle model with blowing slots on both the leading and trailing edges of the trailer have been conducted under contract to the DOE Office of Heavy Vehicle Technologies. These experimental results show overall aerodynamic drag reductions on the Pneumatic Heavy Vehicle of 50% using only 1 psig blowing pressure in the plenums, and over 80% drag reductions if additional blowing air were available. Additionally, an increase in drag force for braking was confirmed by blowing different slots.

Under contract to the DOE Office of Heavy Vehicle Technologies, the Georgia Tech Research Institute (GTRI) is developing and evaluating pneumatic (blown) aerodynamic devices to improve the performance, economics, stability and safety of operation of Heavy Vehicles. The objective of this program is to apply the pneumatic aerodynamic aircraft technology previously developed and flight-tested by GTRI personnel to the design of an efficient blown tractor-trailer configuration. Recent experimental results obtained by GTRI using blowing have shown drag reductions of 35% on a streamlined automobile wind-tunnel model. Also measured were lift or download increases of 100-150% and the ability to control aerodynamic moments about all 3 axes without any moving control surfaces.

An experimental/computational research program has been conducted to evaluate and confirm a patent-pending pneumatic concept intended to improve aerodynamic problem areas of automobiles. These areas of concern include: separated flow and drag reduction; lift, side force and moment control; and lateral/directional stability. The pneumatic concept applied uses a form of blowing which has proven quite effective in aircraft applications because of its very large aerodynamic returns from minimal blowing input. During this research program, this blowing system was installed in models of generic streamlined automobiles and its effect on aerodynamic and control improvements was investigated. Initial wind-tunnel evaluations revealed that the unblown streamlined model exhibited all of the above areas of concern. Pressure distributions on the vehicle were used to design an effective blowing concept which improved vehicle aerodynamics by enhancing the local flowfields.

Experimental investigations have been conducted to evaluate the aerodynamic performance and control of Unlimited-class hydroplanes racing at speeds exceeding 200 mph. These vehicles operate in very strong ground effect and may encounter unexpected disturbances such as wind gusts or waves, which can cause uncontrolled pitch-up and destruction. Specific test techniques have been developed in a modified subsonic wind tunnel to simulate these conditions, allow evaluation of the vehicle's aerodynamics and develop novel control surfaces. The paper presents details of these facilities and test techniques, associated wing-in-ground-effect tests, and characteristics of the pitching hydroplane as it transitions between in- and out-of-ground effect.

The flow-entraining capability of the Circulation Control Wing blown high-lift system has been synergistically combined with upper-surface-mounted engines to provide an even stronger STOL potential. The resulting configurations generate very high supercirculation lift plus a vertical component of pneumatically-deflected engine thrust. Small-scale wind-tunnel and full-scale static thrust-deflection tests have verified these concepts by confirming thrust deflections of greater than 90° produced pneumatically by non-moving aerodynamic surfaces. High lift can be maintained while interchanging thrust recovery and thrust offset for optimum STOL performance, as well as for simplified heavy-lift or overload capability.

Technology developed for the Circulation Control Wing high-lift system has been extended to augment lift by entraining and redirecting engine thrust. Ejecting a thin jet sheet tangentially over a small curved deflecting surface adjacent to the slipstream of a turbofan engine causes the slipstream to flow around that deflecting surface. The angle of deflection is controlled pneumatically by varying the momentum of the thin jet sheet. The downward momentum of the slipstream enhances wing lift. This concept of pneumatically deflecting the slipstream has been applied to an upper surface blowing high-lift system and to a thrust deflecting system. The capability of the pneumatic upper surface blowing system was demonstrated in a series of investigations using a wind tunnel model and the NASA Quiet Short-haul Research Aircraft (QSRA). Full-scale thrust deflections greater than 90 deg were achieved.