Combined diesel–electric and gas
modification of the combined diesel and gas propulsion system for ships
Combined diesel–electric and gas (CODLAG) is a modification of the combined diesel and gas propulsion system for ships. A variant, called the combined diesel–electric or gas (CODLOG) system, contains the same basic elements but will not allow simultaneous use of the alternative drive sources.
System
A CODLAG system employs electric motors which are connected to the propeller shafts (usually two). The motors are powered by diesel generators. For higher speeds, a gas turbine powers the shafts via a cross-connecting gearbox; for cruise speed, the drive train of the turbine is disengaged with clutches.
This arrangement combines the diesel engines used for propulsion and for electric power generation, greatly reducing service cost, since it reduces the number of different diesel engines and electric motors, requiring considerably less maintenance. Also, electric motors work efficiently over a wide speed range, and can be connected directly to the propeller shaft so that simpler gearboxes can be used to combine the mechanical output of turbine and diesel–electric systems.
Another advantage of the diesel–electric transmission is that without the need of a mechanical connection, the diesel generators can be decoupled acoustically from the hull of the ship, making it less noisy. This has been used extensively by military submarines but surface naval vessels like anti-submarine vessels will benefit as well.
Integrated electric propulsion (IEP)
A system which uses both diesel engines and gas turbines to generate electricity for electric motors, where there is no mechanical transmission from either to the propellers, is not classified as CODLAG, but as integrated electric propulsion (IEP) or integrated full electric propulsion (IFEP).
The public source identifies “Combined diesel–electric and gas” as modification of the combined diesel and gas propulsion system for ships. This brief keeps that definition visible, then builds a research path around Combined, diesel and electric.
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