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Key points

  • The difference in pressure created by a truck opposes the direction of travel
  • This creates drag that increases fuel consumption
  • Drag reduction requires a system that can adapt to changing road conditions
  • Eric Sandgren’s system uses computer-controlled flaps to reduce drag

The difference between the high pressure generated at the front of a truck travelling along the motorway and the low-pressure region created by the wake behind it has the net effect of producing a force that opposes the direction of motion of the vehicle, writes Dave Wilson.

Due to the fact that the energy required to form and sustain the wake must come from the vehicle’s power source, the complex, time-dependent fluid-flow phenomenon has a significant detrimental impact on the fuel that such trucks consume.

It’s no wonder then that considerable work has been done to create and evaluate technologies that might be able to reduce the drag caused by the wake on such vehicles to improve their fuel consumption and reduce the greenhouse gases they emit.

However, according to Dr Eric Sandgren, who has just finished an assignment at the University of Nevada where he was the dean of the Mechanical Engineering School, many of the present aerodynamic methods that have been proposed to reduce the drag on trucks have significant limitations.

That, he said, is because the majority of them are fixed solutions that interfere with the normal operation of the trailer particularly loading and unloading operations. Because of that, they tend to function adequately only under optimal conditions and their effectiveness is negated by changing environmental conditions.

According to Sandgren, to have any significant impact on reducing the highly turbulent dynamic-flow wake region directly behind such vehicles and the aerodynamic drag associated with it requires the deployment of a system that has the ability to dynamically adapt to changing road and environmental conditions.

To prove his point, he has developed an adaptive drag-reduction system that integrates computer-controlled, hinged, motor-driven vertical or horizontal flaps that can actively reduce the wake size and maximise the pressure at the rear of a trailer. To do so, the closed-loop control system is fed physical data, including vehicle speed and pressure at one or more locations directly behind the trailer, which it then uses to control the orientation of the flaps.

A small-scale version of the system has already been successfully built and tested on a small scale in the wind-tunnel facility at the University of Nevada in Las Vegas. The proof-of-concept system comprised several motor-controlled flaps that were attached to the rear vertical edge of a hollow box. While the setup simulated the geometry of a trailer, it allowed the design to fit within the working region of the university’s wind tunnel.

Tests have shown efficiency gains that represent a transformational technology for road vehicles

’The system is self-adapting to changing operating conditions, so it will yield the maximum gain in performance under all road conditions. Initial testing of the system has demonstrated significant efficiency gains that, if scalable to a full-sized tractor trailer, would represent a transformational technology for road-going vehicles,’ said Sandgren.

The results of Sandgren’s preliminary investigations showed that the system could reduce drag by more than 40 per cent a figure that, if realisable on a full-scale truck, could potentially make it at least 20 per cent more economical in terms of the fuel it uses.

To progress the idea further, Sandgren would like to scale the wind-tunnel experiments to full size to demonstrate that the active-airflow device can reduce the aerodynamic drag and fuel consumption of large trucks. He would also like to carry out further tests with a typical truck fitted out with a prototype device to validate the results.

Since both of these tasks are likely to prove expensive, Sandgren has formed an alliance with UK industry veteran Tim Blee to seek an industrial partner who might fund further research into the concept through their jointly owned company Polygon Systems.

If all goes according to plan, Blee hopes to make an exclusive offer regarding the grant of marketing, selling and leasing rights for the patented control technology to a specific company who might exploit the idea in the US.

New concept system could reduce wake generated by trucks on the motorway

Key points

  • The difference in pressure created by a truck opposes the direction of travel
  • This creates drag that increases fuel consumption
  • Drag reduction requires a system that can adapt to changing road conditions
  • Eric Sandgren’s system uses computer-controlled flaps to reduce drag

The difference between the high pressure generated at the front of a truck travelling along the motorway and the low-pressure region created by the wake behind it has the net effect of producing a force that opposes the direction of motion of the vehicle, writes Dave Wilson.

Due to the fact that the energy required to form and sustain the wake must come from the vehicle’s power source, the complex, time-dependent fluid-flow phenomenon has a significant detrimental impact on the fuel that such trucks consume.

It’s no wonder then that considerable work has been done to create and evaluate technologies that might be able to reduce the drag caused by the wake on such vehicles to improve their fuel consumption and reduce the greenhouse gases they emit.

However, according to Dr Eric Sandgren, who has just finished an assignment at the University of Nevada where he was the dean of the Mechanical Engineering School, many of the present aerodynamic methods that have been proposed to reduce the drag on trucks have significant limitations.

That, he said, is because the majority of them are fixed solutions that interfere with the normal operation of the trailer particularly loading and unloading operations. Because of that, they tend to function adequately only under optimal conditions and their effectiveness is negated by changing environmental conditions.

According to Sandgren, to have any significant impact on reducing the highly turbulent dynamic-flow wake region directly behind such vehicles and the aerodynamic drag associated with it requires the deployment of a system that has the ability to dynamically adapt to changing road and environmental conditions.

To prove his point, he has developed an adaptive drag-reduction system that integrates computer-controlled, hinged, motor-driven vertical or horizontal flaps that can actively reduce the wake size and maximise the pressure at the rear of a trailer. To do so, the closed-loop control system is fed physical data, including vehicle speed and pressure at one or more locations directly behind the trailer, which it then uses to control the orientation of the flaps.

A small-scale version of the system has already been successfully built and tested on a small scale in the wind-tunnel facility at the University of Nevada in Las Vegas. The proof-of-concept system comprised several motor-controlled flaps that were attached to the rear vertical edge of a hollow box. While the setup simulated the geometry of a trailer, it allowed the design to fit within the working region of the university’s wind tunnel.

Tests have shown efficiency gains that represent a transformational technology for road vehicles

’The system is self-adapting to changing operating conditions, so it will yield the maximum gain in performance under all road conditions. Initial testing of the system has demonstrated significant efficiency gains that, if scalable to a full-sized tractor trailer, would represent a transformational technology for road-going vehicles,’ said Sandgren.

The results of Sandgren’s preliminary investigations showed that the system could reduce drag by more than 40 per cent a figure that, if realisable on a full-scale truck, could potentially make it at least 20 per cent more economical in terms of the fuel it uses.

To progress the idea further, Sandgren would like to scale the wind-tunnel experiments to full size to demonstrate that the active-airflow device can reduce the aerodynamic drag and fuel consumption of large trucks. He would also like to carry out further tests with a typical truck fitted out with a prototype device to validate the results.

Since both of these tasks are likely to prove expensive, Sandgren has formed an alliance with UK industry veteran Tim Blee to seek an industrial partner who might fund further research into the concept through their jointly owned company Polygon Systems.

If all goes according to plan, Blee hopes to make an exclusive offer regarding the grant of marketing, selling and leasing rights for the patented control technology to a specific company who might exploit the idea in the US.

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