|Fuel flows through two metallic meshes before it reaches the fuel injector. A voltage is applied on the two meshes to produce an electric field of about 1 kV/mm between them. Click to enlarge. Credit: ACS.|
Researchers at Temple University in Pennsylvania have developed a small electrorheological device that, when inserted into the fuel line near the fuel injector, can improve fuel economy. In tests results reported in a study scheduled for the 19 November issue of the journal Energy & Fuels, they show an 18.8% increase in fuel mileage in a Mercedes-Benz diesel sedan in highway driving.
The device developed by Rongjia Tao and colleagues creates an electric field that reduces fuel viscosity, enabling the injection of smaller droplets into the engine, which, in turn, leads to more efficient and cleaner combustion than a standard fuel injector. Six months of road testing in a diesel car showed that the device increased highway fuel from 32 mpg to 38 mpg.
Because combustion starts at the interface between fuel and air and most harmful emissions are coming from incomplete burning, reducing the size of fuel droplets would increase the total surface area to start burning, leading to a cleaner and more efficient engine. This concept has been widely accepted because the discussions about the future engine for efficient and clean combustion are focused on ultra-dilute mixtures at extremely high pressure to produce much finer mist of fuel for combustion.
Here, we present our technology for efficient combustion based on the new physics principle that proper application of electrorheology can reduce the viscosity of petroleum fuels. A small device is thus introduced, producing a strong electric field to reduce the viscosity of petroleum fuels just before the fuel atomization. This viscosity reduction leads to much smaller fuel droplets and cleaner and more efficient combustion. Our device could be easily applied on current engines to improve their efficiency.—Tao et al. (2008)
With the device, fuel flows through two metallic meshes before it reaches the fuel injector. A voltage is applied on the two meshes to produce an electric field of around 1.0 kV/mm between the two meshes. The device consumes very low electric power, lower than 0.1 W. Proper application of electrorheology or magnetorheology can reduce the viscosity of liquid suspensions.
Using the mismatch in the dielectric constant or magnetic permeability between the suspended particles and the base liquid, we can apply an electric or magnetic field to aggregate the small particles into large ones. Normally, we aggregate nanoscale or submicrometer particles into micrometer particles...The experiment with crude oil has found that this reduction can be quite significant.
...we extend the above physics principle to refinery fuels. In fact, refinery fuels, such as diesel fuel and gasoline, are made of many different molecules. They can be regarded as liquid suspensions if we take the large molecules as suspended particles, and the base liquid is made of small molecules. Under a strong electric field, the induced dipolar interaction makes the large molecules aggregate into small clusters. Similarly, this change reduces the effective viscosity of refinery fuels.—Tao et al. (2008)
|Size distribution of diesel fuel following atomization with or without an applied electric field. Click to enlarge. Credit: ACS|
Applying this principle to diesel fuel, the researchers found that after application of an electric field of 1 kV/mm, the viscosity of the diesel oil was reduced by about 9%, from 4.6 to 4.18 cP. They then simulated the injection of both diesel and an E20 gasoline blend fuel into cylinders using an Accel injector and collecting the droplets on a plate. While both fuels showed good repeatable results, the results with diesel were particularly strong.
Applied to a Mercedes-Benz 300D sedan for 6 months of road testing, the device improved highway mileage by 18.8%; in city driving, the improvement was 12-15%. For the Mercedes application, the two mesh electrodes were separated by 1 cm. The diesel fuel took 5 s to pass through the 1 kV/mm electric field.
Because our technology, developed on the new physics principle, consumes very small power and improves fuel efficiency significantly, we expect it will have wide applications on all types of internal combustion engines, present ones and future ones. By adjusting the values for the electric field and time duration, we could make this technology work effectively for other fuels, such as biodiesel, kerosene, and gasoline.—Tao et al. (2008)
R. Tao, K. Huang, H. Tang, and D. Bell (2008) Electrorheology Leads to Efficient Combustion. ASAP Energy Fuels, doi: 10.1021/ef8004898