Hydraulic Transmission Gains Traction with Diesel Rail Routes
S. Himmelstein | March 20, 2017British train operator Chiltern Railways is helping to test a new type of hydraulic transmission for diesel-powered rail vehicles. Project partner JCB will supply a diesel engine to power an E-dyn 96 Digital Displacement hydraulic pump provided by Artemis Intelligent Power, Scotland. The pump will supply flow to axle-mounted Digital Displacement motors and the transmission will be installed in a Chiltern Trains Driving Van Trailer.
Digital Displacement Power Bogie (Source: RSSB)
The project seeks to reduce fuel consumption and improve engine performance by combining hydrostatic transmission with on-board energy storage in the form of hydraulic accumulators, which store energy during braking for reuse during acceleration.
Stored energy can be reused to supplement engine power and to reduce journey times through faster acceleration, allowing trains to leave stations without producing emissions.
The technology could be applied to non-electrified rail routes where electrification is difficult to justify on an economic basis.
The Digital Displacement® Hybrid Rail Transmission project is funded by Artemis Intelligent Power and the Rail Safety and Standards Board Ltd. (RSSB).
Going back to 1955 and adding accumulators to answer a problem the 'winning' diesel electric loco's from the initial competition between diesel hydraulic and diesel electric cannot address, brilliant.
This is broadly equivalent to the more recent advent of hydraulic hybrids, like the kind being used on UPS delivery trucks of late - but hydrostatic transmission locomotives are not new, the old Class 35 hymeks served well on british rail since the '60s, and now the bombardier class 170 is still in use with the Voith hydrostatic transmission, that looks like it's who they're trying to compete with.
Hymech transmissions are good, power dense, and low maintenance, but they are noisy. What they are trying to do with adding of accumulators could also be done with a diesel-electric with supercapacitors, but these are heavier and less efficient.
Most efficient would be a KERS flywheel, but the RPM and weight would require very fine balance, be very expensive.