The Environmental Protection Agency (EPA) has announced the establishment of tests of a hydraulic transmission system associated with an internal combustion engine, supposed to be more economical and less polluting.
Based on EPA technology, the Eaton Group (Ohio) will replace the mechanical transmission of a UPS carrier vehicle with a device to transfer the
power through a pressurized hydraulic tank. In practice, the pressure of around 3500 tonnes per square meter, created by the diesel engine rotating at constant speed, makes it possible to drive the rotation of a turbine and therefore that of the wheels - the speed of the vehicle being controlled by the released pressure. in the turbine. This pressure can be built up, which amounts to storing energy. The principle also benefits from the recovery of power during braking. This phenomenon, called "regenerative braking", exists for electric hybrid cars but with an efficiency of 35 to 40% against nearly 75% announced for the hydraulic system.
Preliminary laboratory tests would have, according to the EPA, highlighted a potential fuel saving of 60 to 70% for non-regular operation (at unstable speed). The field trials are therefore eagerly awaited by the project sponsors, among
which the US Army. But the approach does not seem to be unanimous. Ford, for its part, has abandoned this direction to focus on hybrid vehicles.
NYT 10 / 02 / 05 (Test set on transmission that could save fuel)