2-speed Gearboxes

A fuel efficient solution for diesel mechanical systems

The 2-speed reduction gearbox is a fully integrated solution to provide the option for two steps of different propeller speed in a diesel mechanical configuration. The system is ideal for vessels with variations in power requirements, such as Purse Seiners, Trawlers, AHTS, Seismic vessels, Mega Yachts and Rescue vessels.

• Designed for reduced fuel consumption in low rpm conditions
• Ideal for diesel mechanical configurations requiring power generation from the diesel engine to the main swithchboard during operation
• Ideal for hybrid configurations requiring boost, Power Take Home (PTH) and/or diesel electric drive on top of the diesel mechanical configuration

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Reduced propeller rpm - reduced energy consumption

The graphs of Step1 and Step2 in the diagram show the direct effect of reducing the rpm using the 2-speed reduction gearbox.

• The configuration consists of a Main Engine (ME)and a generator in PTO-condition. By designing optimum power distribution to the propeller and utilising the remaining power to the PTO, there will be full utilisation of the available power from the Main Engine. 
• In Step1 the Main Engine run the propeller via the main gear ratio. Simultaneously the Shaft Generator is driven via the PTO gear set. This mode is useful when the power demand for propeller is high and the electric prower production demand is low. In this condition the propeller is highly efficient provided it is optimised for this condition.
• In Step2 the Main Engine run the propeller via the PTO gear that further transmit the mechanical power over the PTI gear set -via the main gear ratio to the propeller. Hence, because of the choosen PTO- and PTI- gear ratios, the propeller run at lower rpm, compared with Step1. The condition is typical when propeller power demand is in lower range, and because of the reduced propeller speed the propulsion efficiency is maintained relatively high. The Main Engine run at its nominal speed that make possible a high electric power production by the Shaft Generator.

Design principles of a 2-speed gearbox

The 2-speed gearbox design and construction is based on the same principles as for all Brunvoll gearboxes, and benefit from a reliable high quality philosophy.

The gear housing is as standard made from high quality grey cast iron, designed with high stiffness and good vibration damping property. However, nodular cast iron is available as option (typical in high Ice class applications).

Gears are designed and manufactured with high precision and optimised for high load, low vibratory excitation and long lasting. Extensive use of sliding bearing (long lasting) for both journal bearings and thrust bearings. Clutches are of high capacity, hydraulically operated, multiple disc, oil lubricated type.

Gearbox fulfil all Class Society requirements.

The gearboxes are designed in 3D and analysed for full load to ensure excellent performance.

The Brunvoll 2-speed gearbox program

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