Main steps to be taken remain the same for almost every vessel
Although ships come in a whole range of types and sizes, when approaching the design of an Engine Room the main steps to be taken remain the same for almost every vessel.
- Ship specification
- Propulsion system design
- Electric system design
- Location of the engine room
- Location of large equipment (engines and electric generators)
- Ship systems design
- Ship accommodation systems design
- Auxiliary Machinery Systems
- Water Intake box
- Ventilation System
- Exhaust System
Only going through these steps, one can appreciate the amount of time and detail that is required to carry out this kind of task, performed by Naval Architects and Marine Engineers. Although it would be impossible to describe in-depth the whole process in this article, we can have a look at the most interesting challenges faced by those professionals when approaching the design of a Yacht’s Engine Room.
Luxury, comfort, and pleasure mark the design of these types of ships, meaning that sailing must be as smooth as possible which translates into very demanding requirements in terms of vibrations and noise onboard. Besides comfort and luxury, the buyer also seeks to optimize fuel consumption (to reduce operational costs) and minimize emissions (considering that they mostly sail in Emission Controlled Areas (ECA’s), the latter two have become essential requirements in modern yacht design.
Ship dimensions must be specified according to (among others) regular sailing areas, and the budget must be agreed upon in order to make the appropriate design decisions.
Ship Specifications include:
- Overall Length
- Waterline Length
- Block Coefficient
Once the Ship Specifications have been agreed by the owner and shipyard, the design process starts by evaluating the best and most suitable propulsion system for the Yacht, followed by the estimation of propulsion power required.
Depending on her dimensions, budget and other parameters, the yacht can use a conventional propulsion system with a marine diesel engine coupled to a shaft and propeller, or a more complex and state-of-the-art system such as a diesel-electric propulsion, which is formed by generator sets that produce the electrical power to either action a shaft directly coupled to an electric motor, or they can be used with azimuth thrusters (see image below).
Figure 1. Diesel-Electric Propulsion System with Azimuth Thrusters (*same system layout idea but in a smaller scale in the case of yachts)
When used with azimuth propulsion, the diesel-electric propulsion system provides further benefits that align to yacht design requirements, such as flexible disposition of diesel-electric generators (there is no shaft coupled to a diesel engine and propeller), reduction of noise and vibrations (we eliminate the interaction hull-shaft) and optimization of fuel consumption since the diesel engines are usually running at a constant speed.
If a conventional propulsion (see image below) is selected, a further electrical generation system will be required, meaning more equipment onboard and more space to be used by the generator sets in addition to the main engine, which leads us to one of the main challenges faced by yacht designers; space requirement and the location of the engine room.
Figure 2. Conventional Propulsion System
The designers seek to minimize the space used for machinery and maximize that which is used for the accommodation and comfort of the passengers onboard. Therefore, when evaluating propulsion systems, besides the cost of the system itself (higher for diesel-electric systems) the space required by the machinery is a major concern.
The conventional propulsion systems are logically located at the aft of the yacht, since the shaft actioning the propeller is directly coupled to the engine and the shorter it is the better in order to optimize, among others, vibrations generated by this system. However, diesel-electric propulsion systems have become more popular, as an example of a state-of-the-art yacht, the Wider 150, launched in 2015, instead of having a unique engine room in the aft, she has two engine rooms; one in the bow with the generator sets and one in the aft with the electrically-powered azimuth propellers.
Figure 3. Wider 150
Once the big machinery has been located and dimensions of the Engine Room(s) fixed, the design of the remaining systems follow in the previously mentioned order. The Ship Systems include Ballast System, Bilges System and Fire Protection System, all based on Ship Specifications. Accommodation Systems include Sanitary Water Systems and Residual Water Systems. Auxiliary Machinery Systems include Fuel systems, Lube Oil Systems, Refrigeration Systems and Compressed Air Systems.
The Water Intake System is used to provide sea water to all the systems that requires it (ballast, fire protection, etc.). It is situated in the engine room and requires water intakes carefully designed and located on the bottom region of the yacht’s sides, close to the engine room where water pumps are located. The ventilation plays a key role in the comfort of the passengers but also in the appropriate functioning of all the machinery, facilitating that the proper temperatures are maintained in the Engine Room(s) all the time.
Finally, the Exhaust System is another challenging system in yacht design. When looking at Yachts we do not normally see a big chimney vertically coming out of the ship. So how are the gases emitted out of the yacht? Once again, a clever design allows gases to be emitted through the sides of the yacht. This system, particular to yachts, avoids the use of deck space to conduct gases out of the ship thanks to the Wet Exhaust System, which is carefully designed to reduce the temperature of the exhaust gas and send it out of the yacht without any water intake, following a similar scheme to the one shown in the picture below.
Figure 4. Wet Exhaust Gas System
To sum up, although the design process of any engine room follows a similar path, there are particularities to every ship according their purpose, their size, their sailing/trading area and most importantly the budget of the buyers. In the case of yachts, one has to keep in mind the following: the requirement of a special exhaust gas system, minimisation of noise and vibrations onboard as well as toxic emissions from the yacht, optimisation of fuel consumption and the use of space and location of the engine room, and always bear in mind the purpose of comfort and luxury when approaching the design of every system onboard.