Innovative new propulsion system from Caterpillar
‘Just proven components combined in a different but screaming simple way’ is how Caterpillar Marine describe its new propulsion system aimed at improving efficiency including for applications in the towage industry.
Caterpillar is mentioned regularly in Tugs & Towing as being suppliers of machinery to new or refurbished tugs. Just as with other engine manufacturers however it is of course under constant pressure to meet demands from customers to improve the efficiency of their assets.
In association with Caterpillar Innovation & Technology Development Division (ITDD) Caterpillar Marine is developing what they describe as ‘a proprietary advanced propulsion system for marine applications’. Called the Cat Marine Advanced Variable Drive (AVD) the patented system calls on Caterpillar’s wider experience with heavy duty variable transmission technology, advanced controls and power system integration.
Caterpillar make the analogy with the automotive industry where solutions to improve the efficiency of vehicles have included designs to overcome air resistance (compare to how tugs hulls are optimised for hydrodynamic forces and provide better flow to propellers) and the introduction of gearboxes to ensure the engine operates at a suitable running speed commensurate with power requirements and acceptable fuel consumption. The marine version of the ‘gearbox’ comes in various forms including variable-pitch propellers.
Caterpillar’s concept is described practically as allowing selection of engine speed independently from propeller shaft speed in turn allowing the engines to operate at ‘significantly lower speeds directly equating to substantial lower fuel consumption’. When full power is required the system mimics a kind of kick-down as in a car’s transmission. It is stated the technical hardware would fit quite well onto a standard reduction gearbox or a thruster’s upper gear, proven components combined in a different but simple way.
The concept involves a fully-integrated propulsion system from bridge interface down to the propellers including AVD technology where the speed of the engines can be modulated and optimised independently from the speed of the fixed-pitch propellers allowing this speed to be varied continuously throughout their full speed range. In addition, the power of main and auxiliary engines can be channelled independently or jointly to propel the vessel.
Igor Strashny, ITDD engineering manager with responsibility for advanced marine propulsion said: ‘Caterpillar AVD technology is a cost effective and fully integrated hybrid propulsion solution that reduces maintenance costs and has conventional service requirements. The system is scalable to meet requirements of a wide range of vessel types, applications, power levels and enables effective downsizing of engines without the loss of performance.’
Caterpillar state further details of the new system will be forthcoming, and it is hoped MJ can report further at that time, including potential uses of the application for the towage industry.
By Peter Barker
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