More Distance for your Diesel...

28 September 2008
Posted by Chris Smith.

Subjecting your diesel engine to a high voltage could improve the efficiency by 20% - which could save a lot of money on the forecourt!

Diesel smoke from a big truckInternal combustion engines are becoming more efficient with each generation of cars, but we're still a long way off perfection.  Now, researchers at Temple University, Philadelphia, have found a way to make diesel engines more efficient by making the droplets of fuel injected into the engine much smaller.

A diesel engine works by spraying a fine mist of fuel into a chamber, where the pressure of a rising piston causes it to burn.  In the process of burning, the fuel and its products turn into gases and expand and this expansion pushes the piston back down, powering the vehicle.  The smaller the fuel droplets when they are sprayed into the chamber, the more efficiently the fuel can be burned, and the more miles you get from a tank of fuel.

Writing in the journal Energy and Fuels, Rongjia Tao and colleagues report on an electrostatic device which could be fitted to a standard engine and subjects the fuel to a strong electric field shortly before it passes into the fuel injector.  This gives each droplet of fuel a negative charge and, as like charges repel, the droplets then repel one another, and form a finer mist as they are sprayed into the combustion chamber.  This makes the engine much more efficient, and improves fuel mileage significantly. 

In lab tests, the team achieved 20% greater power than a traditional engine for the same fuel consumption rate and in real highway driving conditions, the device increased the fuel mileage from 32 to 38 miles per gallon, an increase of 18%.  Even in more demanding conditions of driving in a city, the improvement of fuel mileage averaged at 12-15%.  Also, as the device consumes only 0.1w of electrical power, the improvements in efficiency are not cancelled out by a large increase in electrical consumption.

The team have shown it works well on two engines so far, and are confident that it can be adjusted to work with existing engines as well as new ones, running on diesel and petrol and even things like biodiesel, petrol mixed with ethanol or even kerosene.

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