Cruise ships are big, and they have a lot of engines. They need them for propulsion and to run the ship’s generators that provide electricity for lights, computers, refrigeration systems, etc. The air conditioning system keeps everyone cool in the hot cabins.
This means there is always an engine onboard running somewhere or other. This article will explain how many different internal combustion marine diesel engines you can find on larger cruise liners.
Modern cruise ships have up to six engines, so even though one may fail, another can take over its duties without any problems being noticed by passengers on board. The use of smart technology built into these vessels generates an automatic backup plan if something goes wrong.
The large passenger liner was born at sea with the advent of steam power. As technology advanced, so did the size of these vessels. With each new revolution came more complex machinery to propel them.
Engineers devised ways to make progress while keeping costs down, from wood-burning paddle wheels to oil-powered propellers, from sails to electric motors, and finally, gas turbines and nuclear reactors.
Eventually, when fuel became scarce due to rationing during wartime, the age of the luxury oceanic vessel ended. The last remaining “superliners” were converted into cargo carriers called containerships.
These substantial floating warehouses could be filled anywhere along their long length by just sliding them out through doors like garage doors. The giant container units then traveled back upriver to unload their cargo directly onto railcars.
Today we take our vacations on cruises because it’s fun! We want to see exotic places and experience things unlike anything else, especially if the trip includes swimming, snorkeling, surfing, parasailing, jet-skiing, windsurfing, wakeboarding, kiteboarding, canoeing, river cruising, and all-you-can-eat dining, and dancing. But what do we bring along to enjoy all those activities? Boats and boats require propulsion.
This article will discuss several forms of propulsive energy used by modern cruise ships. At first glance, each may look quite similar: they’re all internal combustion (IC) diesel engines fueled by high molecular weight hydrocarbon fuels, collectively called bunker/biofuel blends.
However, even though the actual mechanism inside each IC diesel engine type is identical, its application varies greatly depending on the machine’s intended purpose. For example, not every cruise boat needs engines capable of propelling her across oceans at 50 knots per hour (kph).
Nor does she necessarily need powerful engines to quickly turn around to dock alongside another ship. So let’s start off discussing smaller versions of these IC engines found aboard small pleasure craft.
But before we get started, let’s consider the essential components required to understand why you’d ever want to put multiple engines onboard your yacht or sailboat.
Let’s say you’ve decided to charter a private island with no roads except two dirt paths leading straight to either end of the island. You won’t need any vehicles to travel between your villa and your favorite beach bar – you rent a moped, scooter, golf cart, or maybe even a bicycle.
You don’t need to carry food, supplies, or luggage since everything you might need is on the island. All you need to do is go outside, hop on your rented vehicle, drive wherever you desire, and stop whenever you decide. No parking problems were encountered.
Now imagine yourself living in yet another tiny tropical paradise. What would happen if someone tried to block access to your home via one of the only two roadways available? You wouldn’t have time to react. Your car would probably become trapped behind that obstacle, preventing you from leaving until the issue had been resolved.
That’s precisely how most cruise ships function. Their main engines are designed primarily to move the entire structure forward, enabling the ship to reach port safely without being held up by dockside traffic jams caused by slower-moving smaller yachts trying to dock alongside them. Auxiliary engines must be employed to perform those tasks if additional functions are needed.
Therefore, having multiple engines provides redundancy. Each additional engine becomes a backup that can operate independently of the others should something go wrong. It also allows one engine to act as an emergency generator in electrical failure.
Finally, extra capacity enables the ship to burn less expensive biofuels than regular petroleum-based ones to reduce operating costs and taxes associated with importing foreign crude oils.
When you think about it, burning fossilized plant matter to produce mechanical work doesn’t seem very efficient. After all, coal isn’t made of diamonds, nor does natural gas come from helium. Yet, even though alternative fuels aren’t particularly abundant or cheap, diesel remains popular among commercial users worldwide.
Why? Because it works. More specifically, it works pretty darn well. Depending on the application involved, diesel engines’ power output ranges from 200 watts to 100 megawatts! Of course, the number of engine horsepower depends on the displacement of the overall hull (which affects maximum speed), the amount of fuel injected into the cylinders, and the average ambient temperature within the engine compartment.
Also, since diesel engines rely solely on compression pressure to ignite fuel injection rather than spark plugs or electronic igniters, they require fewer parts and thus lower maintenance expenses. Another great thing about diesel is that they typically offer higher efficiency than comparable IC engines. Hence, less fuel equals less pollution released into the atmosphere.
Most gasoline-powered engines powering boats fall under the category known as outboard motors. These devices consist mainly of three primary parts: the motor, which generates power; a transmission that converts rotary motion produced by the engine into linear movement suitable for driving propellers or rudders; and the mounting bracket assembly, which connects the motor unit to the transom of the boat.
Numerous makes and models of outboards are available today, ranging from small 1HP units mounted atop short skiffs to massive 500+ HP supercharged V8s weighing hundreds of pounds apiece installed on 40-foot plus catamarans.
Most importantly, however, whether you choose a manual push-button starter model or a fully automatic choke-less design, you’ll still need to keep close tabs on the intake manifold pressure (IMP) gauge. It is vital to ensure fresh gas is appropriately mixed with the air before ignition. Otherwise, you risk damaging your engine or suffering premature wear and tear.
Smaller Diesel Engines On Small Ships
While diesel engines dominate the market for heavy-duty industrial use, IC engines remain popular among boaters who prefer lightweight performance combined with reliable dependability. Although slow compared to diesel, IC engines are often preferred for recreational applications because they feature low noise emissions, better thermal efficiencies, and far greater torque outputs than gasoline cousins.
Consequently, these relatively inexpensive machines generate sufficient thrust to allow smaller-scale boats to accomplish feats otherwise impossible. These engines are commonly seen powering pontoon boats, canal boats, houseboats, dinghies, trawlers, personal watercraft, and various inflatable toys.
One major drawback of IC engines is their limited range of operation compared to diesel alternatives. While decent-quality models can quickly achieve 12 knots under ideal conditions, these engines generally cannot exceed 10 knots unless modified considerably.
This deficiency prevents these units from replacing conventional outboard designs for faster applications. However, they serve perfectly well for specific purposes, such as leisurely excursions involving little or no maneuvering.
Propane Gas Powered Engines
Although sometimes confused with LPG or liquefied petroleum gases, propane is stored in liquid form at room temperature. Its chemical formula consists of four hydrogen atoms attached to carbon molecules, resulting in two hydrogens sitting next to each other and two dangling away.
Propane boils near room temperature when placed under atmospheric pressure like lighter hydrocarbons. Unlike liquids, however, propane exhibits extremely rapid evaporation rates, meaning it begins to boil almost instantaneously once exposed to open air.
Since refineries refine crude oil to extract valuable products like gasoline, heating value, and lubricating qualities, they seldom remove the lightest elements present in petroleum, such as methane and ethane. Instead, they focus exclusively on refining heavier hydrocarbons containing 3 to 5 carbon atoms per molecule.
Unfortunately, although technically classified as gaseous hydrocarbons, pure propane lacks the adequate density to float freely above ground level, rendering it useless as a transportation medium. Thus, the final product is blended with varying amounts of oxygenated compounds containing 2 to 6 carbons per molecule to create what’s known as biogases.
For decades, this mixture served as the sole source of portable cooking and lighting facilities aboard military submarines and naval warships. Propane tanks are increasingly used instead of batteries or solar panels to supply electrical power to remote locations lacking utility service infrastructure.
Some people install special appliances equipped with integrated heat exchangers to capture waste heat generated by engines to warm homes during cold weather months.