How does a submarine engine work?

Answer 1

Most modern submarines today are either Nuclear Powered or Diesel Electric, the same technology used in submarines during WWI and WWII.

Diesel Electric boats use diesel generators to recharge their massive batteries. In WWI and WWII, submarines weren't true submersibles as we define them today - they were low profile surface vessels with limited submerged operational capability. With the advent of teardrop and cigar shaped hulls, and vastly improved battery technology, DE's can now remain submerged on battery operation for weeks. However, they are still limited in speed, and they have no choice but to come to periscope depth and snorkel to recharge their batteries. While they are on battery operation they are extremely quiet, but once snorkeling they are extremely noisy. In the early days of the Nuclear Power program for the Navy, there was heated debate over the cost of Nuclear Power vs. Diesel Electric technology. A test was conceived, where a single Nuclear Powered submarine was pitted against several DE boats. Each time they had to snorkel and recharge, they became sitting ducks. Since that time, the Navy has been almost exclusively Nuclear with submarines, only having 3 DE's in the fleet, and those primarily for training purposes, known as the "B Girls" - USS Barbel (SS-580), USS Blueback (SS-581) and USS Bonefish (SS-582). They have since been decommissioned and the current submarine fleet of the U.S. Navy is all Nuclear.

The primary operation and theory has remained the same for decades - only the technology has improved. Essentially, diesel engines that can generate electricity recharge the boat's batteries, and the DC electricity from the batteries powers an electric motor connected to the main propeller shaft.

Nuclear Powered submarines, true submersibles by all definitions, are only limited by their crews. Without the need for crew resupply, the boat could remain at sea indefinitely for years until the need for refueling her reactor. Nuclear submarines also have a diesel generator, batteries, and a backup electric motor should the main engines fail or have problems. While the speed is pretty slow, it's at least something.

Reactor technology is pretty simple - the reactor generates heat, and the pressurized cooling water (U.S.) metal (Russian) that flows around it is passed into a steam generator, which is nothing more than a large chamber where the coolant flows through in a pipe and water from a secondary water feed is pumped into the chamber and onto the hot coolant pipes, flashing it instantly into steam. The pressurized steam is then used to power Turbine Generators, which in turn are connected to reduction gears connected to the main propeller shaft. After the steam is used, it passes into a condenser, which turns it back into water, and it's pumped again back into the steam chamber to again start the continuous loop.

The U.S. Navy has a perfect record using pressurized water reactors since they were introduced into the fleet by Admiral Hyman G. Rickover in the '50's beginning with the Nautilus. The Russians have typically used different reactor coolant over the years with mixed results, such as liquid nickel or liquid sodium.

If you want to see a basic diagram of how it works for a Nuclear boat, you can see a diagram in one of the old Welcome Aboard pamphlets I have on my own site containing pics and other items from my own submarine days. The link is below, and it's on page 6. Note that even though it's a basic diagram, all ships or submarines around the world that are Nuclear powered use the same basic principle - the only difference is in the machinery and reactor designs.