The Rolls-Royce WR-21 is a

gas turbine A gas turbine, also called a combustion turbine, is a type of continuous flow internal combustion engine. The main parts common to all gas turbine engines form the power-producing part (known as the gas generator or core) and are, in the directio ...

marine engine An inboard motor is a marine propulsion system for boats. As opposed to an outboard motor where an engine is mounted outside the hull of the craft, an ''inboard motor'' is an engine enclosed within the hull of the boat, usually connected to a pr ...

, designed with a view to powering the latest naval

surface combatant Surface combatants (or surface ships or surface vessels) are a subset of naval warships which are designed for warfare on the surface of the water, with their own weapons and armed forces. They are generally ships built to fight other ships, subma ...

s of the partner nations.

History

Developed with government funding input from the United Kingdom, France and the United States, the WR-21 was designed and manufactured by an international consortium led by

Northrop Grumman Northrop Grumman Corporation is an American multinational aerospace and defense technology company. With 90,000 employees and an annual revenue in excess of $30 billion, it is one of the world's largest weapons manufacturers and military techn ...

as prime contractor. The turbine itself was designed primarily by

Rolls-Royce Rolls-Royce (always hyphenated) may refer to: * Rolls-Royce Limited, a British manufacturer of cars and later aero engines, founded in 1906, now defunct Automobiles * Rolls-Royce Motor Cars, the current car manufacturing company incorporated in ...

with significant marine engineering and test facility input from DCN, with Northrop Grumman responsible for the intercooler, the

recuperator A recuperator is a special purpose counter-flow energy recovery heat exchanger positioned within the supply and exhaust air streams of an air handling system, or in the exhaust gases of an industrial process, in order to recover the waste heat. ...

and system integration. WR-21 development draws heavily on the technology of the successful

Rolls-Royce RB211 The Rolls-Royce RB211 is a British family of high-bypass turbofan engines made by Rolls-Royce. The engines are capable of generating of thrust. The RB211 engine was the first production three-spool engine, and turned Rolls-Royce from a sign ...

and

Trent Trent may refer to: Places Italy * Trento in northern Italy, site of the Council of Trent United Kingdom * Trent, Dorset, England, United Kingdom Germany * Trent, Germany, a municipality on the island of Rügen United States * Trent, California, ...

families of gas turbines. The original design and development of the WR-21 was carried out by

Westinghouse Electric Corporation The Westinghouse Electric Corporation was an American manufacturing company founded in 1886 by George Westinghouse. It was originally named "Westinghouse Electric & Manufacturing Company" and was renamed "Westinghouse Electric Corporation" in ...

(later Northrop Grumman Marine Systems) under a

US Navy The United States Navy (USN) is the maritime service branch of the United States Armed Forces and one of the eight uniformed services of the United States. It is the largest and most powerful navy in the world, with the estimated tonnage ...

contract placed in December 1991. Later the

Royal Navy The Royal Navy (RN) is the United Kingdom's naval warfare force. Although warships were used by English and Scottish kings from the early medieval period, the first major maritime engagements were fought in the Hundred Years' War against ...

and the

French Navy The French Navy (french: Marine nationale, lit=National Navy), informally , is the maritime arm of the French Armed Forces and one of the five military service branches of France. It is among the largest and most powerful naval forces in t ...

became interested in the WR-21, leading to Rolls-Royce and DCN involvement. The WR-21 is the propulsion system of Royal Navy

Type 45 destroyers The Type 45 destroyer, also known as the D or ''Daring'' class, is a class of six guided-missile destroyers built for the United Kingdom's Royal Navy in the early 21st century. The class is primarily designed for anti-aircraft and anti-missil ...

Design

The WR-21 is the first aeroderivative

to incorporate

gas compressor A compressor is a mechanical device that increases the pressure of a gas by reducing its volume. An air compressor is a specific type of gas compressor. Compressors are similar to pumps: both increase the pressure on a fluid and both can tran ...

intercooler and

exhaust heat recovery system An exhaust heat recovery system turns waste heat energy in exhaust gases into electric energy for batteries or mechanical energy reintroduced on the crankshaft. The technology is of increasing interest as car and heavy-duty vehicle manufacturers co ...

technologies that deliver low specific fuel consumption across the engine's operating range. It offers a reduction in fuel burn of 30% across the typical ship operating profile. *The intercooler cools air entering the high-pressure compressor, reducing the amount of energy required to compress the air. *The

preheats the combustion air by recovering

waste heat Waste heat is heat that is produced by a machine, or other process that uses energy, as a byproduct of doing work. All such processes give off some waste heat as a fundamental result of the laws of thermodynamics. Waste heat has lower utility ...

from the exhaust, improving cycle efficiency and reducing fuel consumption.

Specifications

* Rated power: 25.2 MW * Specific fuel consumption: approximately * Main module wet weight: * Twin-spool gas generator and free-rotating power turbine ** Low-pressure (LP) spool with six-stage compressor and single-stage

turbine A turbine ( or ) (from the Greek , ''tyrbē'', or Latin ''turbo'', meaning vortex) is a rotary mechanical device that extracts energy from a fluid flow and converts it into useful work. The work produced by a turbine can be used for generating ...

at 6,200 rpm ** High-pressure (HP) spool with six-stage compressor and single-stage turbine at 8,100 rpm ** Five-stage free power turbine 3,600 rpm (60 Hz) * Intercooler between LP and HP compressors * Nine radial combustors * Exhaust heat recuperator to combustor inlet air

Operational issues

In 2009 it was discovered that the

intercooler as fitted in the WR-21, on Type 45 destroyers, had a major design flaw, failing to operate in water temperatures beyond 30C. The intercooler of the first Type 45 destroyer, , failed in the mid-Atlantic in 2010 and had to be repaired in Canada, with further repairs for intercooler failure in 2012 in Bahrain. The Type 45's pioneering integrated electric propulsion (IEP) system uses two WR-21s and two Wartsila 2-MW diesel generators to power everything on board, including weapons systems in addition to propulsion and other functions, leaving the ships vulnerable to "total electric failure". The Ministry of Defence said: "The Type 45 was designed for world-wide operations, from sub-Arctic to extreme tropical environments, and continues to operate effectively in the Gulf and the South Atlantic all year round." The WR-21 engines will have to be supplemented by one or two additional diesel generators, fitted by cutting open the hull in dry dock. Former First Sea Lord Admiral Philip Jones clarified that "WR-21 gas turbines were designed in extreme hot weather conditions to what we call “gracefully degrade” in their performance, until you get to the point where it goes beyond the temperature at which they would operate... we found that the resilience of the diesel generators and the WR-21 in the ship at the moment was not degrading gracefully; it was degrading catastrophically, so that is what we have had to address." The Admiral still argued that despite the problems, the Royal Navy has been able to deploy Type 45 destroyers in nine-month cycles to the Gulf region where temperatures are high with little fault. The Royal Navy has also been able to maintain at least two Type 45s at operational readiness.

References

External links

Rolls-Royce WR-21 Marine gas turbine page
(archived 2013-11-08) * {{DEFAULTSORT:WR-21 Aero-derivative engines Gas turbines Marine engines