New Ship Engines Are Bigger and Better

Ship engines are being forced to deliver ever increasing amounts of power as the cargo capacity of vessels continues to increase. There are now ships that carry ten thousand containers, and even larger vessels are in the works. Rising costs for fuel have prompted firms to explore new methods for engine design including gas turbines and a variety of hybrids. For now though, diesel power remains the workhouse of modern maritime engine technology. Other technologies are relegated mainly to combat vessels, where speed is more the issue than cost efficiency. Currently the most powerful diesel is made by the Swiss firm Wartsila Sutzer, which may seem strange given that country’s landlocked geography. Their RTA 96-C motor is a two stroke, turbocharged engine that comes in a variety of configurations ranging from 6 to 14 cylinders. The 14 cylinder model is 88 feet in length and 44 feet tall. The behemoth weighs in at 2300 tons and can produce about 109,000 horsepower operating at 102 rpm’s. Each cylinder head measures 38 inches across with a stroke of 98 inches giving a total displacement of just over 111,000 cubic inches. Each cylinder can produce 7780 horsepower. The thermal efficiency of this monster motor is rated at over 50 %, the first such engine to achieve such a high level. This means more than half the energy in the diesel fuel used is being converted to motive power. Single engine ships are the preferred method for propulsion of even the largest vessels, and the 14 cylinder format can easily propel the latest Post Panamax ship. That title refers to the fact that these ships are too large to enter the Panama Canal even after the enlargement of that venerable transit system between oceans. The new lock system of the Panama Canal will allow vessels carrying over 7,000 containers to pass between the Atlantic and Pacific oceans. The low rpm rate of large ship engines makes them extremely durable since there is less wear due to the slow engine speed. They are also quite fuel efficient. The RTA 96-C for instance consumes about a quarter pound of fuel per hour for each unit of horsepower produced. Automobile engines swallow up fuel at twice that rate at minimum because their thermal efficiency is only rated at 25% or less. Hybrid designs promise even greater efficiencies and fuel savings, but for now their complexity and higher prices have limited their use to cruise ships and some naval vessels where costs are less of a concern.