Ever since Ulysses plunged his oar in the wine-dark Aegean Sea, mariners have been looking for an efficient way to move a ship. Greek galleys anticipated Robert Fulton’s paddle wheel, which was put out of business by the screw propeller. But GE engineers now built and patented a new machine that attaches to the bottom of a ship like a jet engine to an aircraft wing, and looks like one too. The device, called the Inovelis pump jet, can swivel 360 degrees around its axis and push the ship in any direction without a rudder.
That’s Epic: Ships using GE pump jets will supply Petrobras oil and gas platforms located 180 miles off the coast of Brazil.
“We took the motor and put it in an external pod so it’s now in the water,” says Paul English, marine leader at GE Power Conversion. “Like a jet engine, it has fixed stator vanes inside a nozzle. The vanes straighten the water flow and guide it across the impeller blades. The blades get good water to attack and throw out the back. The result is a more efficient engine with better thrust.”
English says traditional screw propellers produce drag by “spilling” water around the screw tips to the front of the propeller. “When you look over the aft end of a ferry, you see a lot of churning water,” English says. “That’s basically wasted energy. Instead of pushing the water backwards, which is ideal, you are wasting energy on making it roll.” The stator and impeller, a fancy propeller enclosed in a nozzle, greatly reduce the churn.
The pod design also eliminates complicated transmission gears, cuts maintenance, and improves efficiency. “The shaft comes out the back end of the pod and straight into the impeller,” English says. “There are no gearbox [energy] losses at all. We’ve got rid of it.”
The pump jet was originally used in submarines, jet skis and high-speed surface vessels. But GE adapted the technology so that it can now power large supply ships.
GE workers are already making 17 pump jets for eight offshore platform supply vessels, including four ships that will supply deep sea oil and gas platforms operated by Petrobras and located some 180 miles of the coast of Brazil.
The new pods were designed for maximum speed of 16 knots, the oil and gas industry standard. They will work in combination with GE’s data-driven dynamic positioning system, which can keep ships virtually stationary on high seas without an anchor. “The ship algorithms gather location, water current speed and other data, and the computer calculates what thrusts it needs and its direction,” English says. “The pods can turn around the vertical axis and hold the ship at a particular angle. You don’t need a rudder.”
If only Ulysses had a pump jet. He could set his ship on autopilot, his crew could skip the wax earplugs, and they could all enjoy the Siren song together.