Marine Propulsion Systems: Components & Power Plants

Ship Systems & Propulsion Components Explained

Understanding the intricate workings of a ship requires knowledge of its fundamental systems and components. This document clarifies these essential elements, focusing on propulsion and power generation.

Understanding Ship Systems & Components

A system is a combination of machinery, equipment, and its connections (piping and cabling) designed to perform a specific task or sub-function. Systems are often grouped by their primary function.

A component is a fundamental building block of a system. For example, a diesel engine is a component of the propulsion system, with its function being to provide mechanical power.

Key Propulsion System Components

Prime Mover: Function & Types

The prime mover's primary function is to deliver mechanical energy. It achieves this by converting the chemical energy contained in fuel into mechanical energy. In a ship's propulsion system, common prime movers include:

• Diesel engines
• Gas turbines
• Steam turbine plants

Propulsion Transmission Systems

The transmission is a critical subsystem within the propulsion system. It is itself built from various components such as shafts, gearboxes, and bearings. The transmission performs two vital functions:

1. To transfer the mechanical energy generated by the prime mover to the propulsor.
2. To transfer the thrust generated by the ship’s propulsor to the ship’s hull.

Transmission systems can be categorized into:

• Mechanical Drives:
  • Direct Drive
  • Geared Drive
• Non-Mechanical Drives:
  • Electrical Drive
  • Other specialized drives

The Ship Propulsor's Role

The propulsor is responsible for converting the rotating mechanical power delivered by the engine into translating mechanical power, which ultimately propels the ship through water.

Essential Propulsion Support Systems

Beyond the main components mentioned above, the propulsion system relies heavily on various propulsion support systems, often referred to as auxiliary systems. These systems are crucial for the proper functioning, and in some cases, the vital operation of the main propulsion system. Key auxiliary systems include:

• Fuel supply and treatment system
• Engine room ventilation system (also supplies combustion air)
• Exhaust gas system
• Lubrication system
• Cooling system
• Compressed air supply system

Ship Power Plant Concepts

Propulsion and electric power supply are two paramount functions that must be effectively performed to fulfill a ship's mission. The combination of the propulsion system and the electric power plant is collectively referred to as a power plant.

Ship power plant concepts are broadly divided into two main types:

Mechanical Power Plant Concepts

These concepts involve the mechanical transmission of energy from the prime mover to the propulsor and to other driven consumers of mechanical energy. Examples include:

• Direct Drive
• Geared Drive
• Diesel Geared Drive
• Steam Turbine Geared Drive
• Multiple Shafts
• Combined Drive systems

Electrical Power Plant Concepts

In these concepts, the propulsor is driven by an electric motor. While the electric power supply is typically separate from other generators, it might be linked to the propulsion system via a shaft generator. Examples include:

• All-Electric Ship concept
• Hybrid Drive systems