Ship propulsion is the mechanism used to move a ship through water. It typically involves converting energy from a power source, such as an engine, into motion that propels the ship forward. Various propulsion systems are used in the shipping industry, depending on the ship’s size, speed, and intended use.
Some of them include:
- Marine diesel engines
- Steam turbine ship installations
- Gas turbine power plants
- Azimuthal installations
Marine diesel engines
A marine diesel engine is an internal combustion engine used to power boats and ships. It compresses air, which is mixed with fuel to create a controlled explosion that drives the engine’s pistons. This mechanical energy is then used to turn the propeller and move the vessel through the water.
- High fuel efficiency and economy compared to gasoline engines
- Long-lasting, with many diesel engines having a lifespan of up to 20,000 hours or more
- High durability to withstand harsh marine environments, such as saltwater, without corrosion
- Diesel fuel is less flammable than gasoline, making it a safer option for marine engines
- Relatively low-temperature level generated in the engine room
- A wide range of capacities and rotational speeds facilitates highly efficient installations for vessels of various classes
- The complexity of the design demands more specialized knowledge and tools for repairs and maintenance
- Heavy weight can affect the performance and fuel efficiency of the vessel
- Loud noise and vibration can be a nuisance for the passenger
- Heavy weight and larger size can make them difficult to install and maneuver
Steam turbine engines
A steam turbine engine is a machine that generates electricity by using steam to rotate a turbine. The steam is created by heating water, which is then directed through a series of blades in the turbine. As the steam flows over the blades, it causes them to rotate, which drives a generator to produce electricity. The steam is then condensed back into water and recirculated through the system. The turbine’s efficiency depends on the steam quality and the turbine blades’ design.
- Higher fuel efficiency
- Extreme durability to withstand harsh marine environments
- High power output suited for large ships and power plants
- Longer service intervals
- Highly versatile as it can run on a variety of fuels, including oil, coal, and natural gas
- Slow start-up time
- More expensive than internal combustion engines
- Complexity of design and difficulty in installation
- Regular cleaning and inspection required
Gas Turbine Engines
Marine gas turbine engines use compressed air and fuel to produce high-temperature and high-pressure gas, which is then directed through a turbine to produce mechanical energy. The mechanical energy is then used to drive a generator, which produces electricity on board the ship. The gas turbine installation typically includes a combustion chamber, a compressor, and a turbine, as well as an air intake system, fuel delivery system, and exhaust system. It provides high power-to-weight ratios, operates at high speeds, and can be configured to operate on various fuels for increased efficiency.
- High fuel efficiency
- Fast start-up time
- Fewer moving parts
- Highly reliable
- Reduced maintenance and repair costs
- Low efficiency at low power output
- High initial cost
- Loud noise levels at the time of operation
- Limited operating temperature range
A marine propeller is a rotating device that propels a ship through water by converting power from an engine or motor into thrust. The propeller consists of blades attached to a hub that spins as the engine or motor rotates the propeller shaft. The shape and size of the propeller blades determine the amount of thrust generated, with larger blades producing more thrust but requiring more power to turn. Marine propellers are essential components of most modern ships and boats, and their design and operation are critical to the vessel’s performance and efficiency.
A controllable pitch propeller has significant advantages over a fixed pitch propeller, which include:
- Selection of the most effective blade angle for any given speed
- The ability to use the ship’s non-reversible power plants, since such a propeller allows for backward movement
- The ability to lower the blades to provide the least resistance when not in use
Ships can have active rudders, which are propellers on the steering wheel. They move at angles up to 80 ° and are used at low speeds up to 5 knots. At high speeds, they turn off, and the rudder moves within the usual limits of up to 35° on each side. More information about the propeller-steering system is available in our article.
Azipod is an electromotive propulsion system used on ships that consist of a motor, a propeller, and a steering mechanism housed in a pod that can rotate 360 degrees, providing full maneuverability. The pod can be installed either at the ship’s stern or under the hull, depending on the vessel’s design. Azipod offers several advantages over traditional shaft propulsion systems, including better fuel efficiency, reduced noise and vibration levels, and increased maneuverability. It is commonly used on large passenger ships, icebreakers, and offshore vessels.
The only downsides with this type of installation are the high cost and complexity of maintenance.
Breezemarine Group specializes in maintenance services for marine power plants and propeller-steering systems. With over a decade of experience in the marine industry, we have earned customers’ trust worldwide. Our team remains at the forefront of the latest trends and advancements in the marine industry, ensuring that we promptly implement cutting-edge solutions. With offices across several countries, we are well-positioned to swiftly address any issues faced by our clients’ fleets, providing them with comprehensive support and peace of mind.