View source for Rolls-Royce WR-21

[[File:HMS Daring-1.jpg|thumb|The WR-21 powers Royal Navy [[Type 45 destroyer]]s.]]

The '''Rolls-Royce WR-21''' is a  [[gas turbine]] [[marine engine]], designed with a view to powering the latest naval [[surface combatant]]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]] as prime contractor.<ref name=grumman-2000>{{cite news |url=http://www.defense-aerospace.com/articles-view/release/3/3473/rolls%C2%A7grumman-to-power-type-45-destroyer-%28nov.-2%29.html |title=Northrop Grumman/Rolls-Royce Team Selected as Preferred Supplier |newspaper=defense-aerospace.com |date=1 November 2000 |accessdate=30 January 2016}}</ref> The turbine itself was designed primarily by [[Rolls-Royce Holdings|Rolls-Royce]] with significant marine engineering and test facility input from [[DCNS (company)|DCN]], with Northrop Grumman responsible for the [[intercooler]], the [[recuperator]] and [[system integration]].<ref name=grumman-2000/><ref name=Janes>{{cite web|url=http://www.faqs.org/abstracts/Military-and-naval-science/WR-21-gamble-pays-off-Rand-to-study-UK-naval-programme.html|title=WR-21 gamble pays off|publisher=Jane's Navy International|year=2000|accessdate=2009-11-16}}</ref>

WR-21 development draws heavily on the technology of the successful [[Rolls-Royce RB211]] and [[Rolls-Royce Trent|Trent]] families of gas turbines.<ref name=RR/>

The original design and development of the WR-21 was carried out by [[Westinghouse Electric Corporation]] (later Northrop Grumman Marine Systems) under a [[US Navy]] contract placed in December 1991. Later the [[Royal Navy]] and the [[French Navy]] became interested in the WR-21, leading to Rolls-Royce and DCN involvement.<ref name=asme-1997>{{cite conference |url=http://proceedings.asmedigitalcollection.asme.org/proceeding.aspx?articleid=2088684 |title=WR-21 Intercooled Recuperated Gas Turbine System Overview and Update |author=Carl L. Weiler, John Chiprich |publisher=American Society of Mechanical Engineers |conference=ASME 1997 Turbo Asia Conference |date=October 1997 |isbn=978-0-7918-7867-5 |accessdate=30 January 2016}}</ref>

The WR-21 is the propulsion system of Royal Navy [[Type 45 destroyers]].

==Design==
The WR-21 is the first aeroderivative [[gas turbine]] to incorporate [[gas compressor]] [[intercooler]] and [[exhaust heat recovery system]] technologies that deliver low specific fuel consumption across the engine's operating range.<ref name=RR>{{cite web|url=http://www.rolls-royce.com/marine/products/diesels_gas_turbines/gas_turbines/wr21.jsp|title=WR-21 Marine gas turbine|publisher=[[Rolls-Royce plc]]|date=|accessdate=2009-11-16}}</ref> It offers a reduction in fuel burn of 30% across the typical ship operating profile.<ref name=PR>{{cite web|url=http://www.prnewswire.co.uk/cgi/news/release?id=48558|title=WR-21 engine selected for Royal Navy type 45 destroyers|accessdate=2009-11-16}}</ref>

*The [[intercooler]] cools air entering the high-pressure compressor, reducing the amount of energy required to compress the air.<ref name=RR/>
*The [[recuperator]] preheats the combustion air by recovering [[waste heat]] from the exhaust, improving [[cycle efficiency]] and reducing fuel consumption.<ref name=RR/>

==Specifications==

* Rated power: 25.2&nbsp;[[megawatt|MW]]
* [[Specific fuel consumption (shaft engine)|Specific fuel consumption]]: approximately {{cvt|190|g/kWh|g/MJ}}
* Main module wet weight: {{val|45974|u=kg|fmt=commas}}
* Twin-spool gas generator and free-rotating [[free-turbine turboshaft|power turbine]]
** Low-pressure (LP) spool with six-stage [[compressor]] and single-stage [[turbine]] 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&nbsp;rpm (60&nbsp;Hz)
* [[Intercooler]] between LP and HP compressors
* Nine [[can combustor|radial combustors]]
* [[Recuperator|Exhaust heat recuperator]] to combustor inlet air

==Operational issues==
In 2009 it was discovered that the [[Northrop Grumman]] intercooler as fitted in the WR-21, on Type 45 destroyers, had a major design flaw,<ref>{{cite news|last=Trevithick |first=Trevor|title=''Royal Navy Will Retrofit Type 45 Destroyers To Prevent Them Breaking Down''|url=http://www.thedrive.com/the-war-zone/19509/royal-navy-will-retrofit-type-45-destroyers-to-keep-them-from-breaking-down|date=22 March 2018|publisher=Time Inc|accessdate=22 April 2018}}</ref> failing to operate in water temperatures beyond 30C. The intercooler of the first Type 45 destroyer, {{HMS|Daring|D32|6}}, 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 (United Kingdom)|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."<ref>{{cite web |url=https://www.theguardian.com/uk-news/2016/jun/07/destroyers-will-break-down-if-sent-to-middle-east-admits-royal-navy |title=Destroyers will break down if sent to Middle East, admits Royal Navy |newspaper=The Guardian |date=7 June 2016  |author=Richard Norton-Taylor |accessdate= 8 June 2016}}</ref>

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.<ref name="auto">{{cite news|title=Oral evidence: Naval Procurement: Type 26 and Type 45 HC 221|url=http://data.parliament.uk/writtenevidence/committeeevidence.svc/evidencedocument/defence-committee/naval-procurement-type-26-and-type-45/oral/35261.html|accessdate=21 July 2016|publisher=UK House of Commons Defence Select Committee|date=21 July 2016}}</ref>

==References==
{{reflist}}

==External links==
* [https://web.archive.org/web/20131108062512/http://www.rolls-royce.com/marine/products/diesels_gas_turbines/gas_turbines/wr21.jsp Rolls-Royce WR-21 Marine gas turbine page] (archived 2013-11-08)
* {{Cite conference |url=http://nippon.zaidan.info/seikabutsu/2003/00916/pdf/igtc2003tokyo_os203.pdf |title=The WR-21 Intercooled Recuperated Gas Turbine Engine - Integration Into Future Warships |author=Commander Colin R English |conference=Proceedings of the International Gas Turbine Congress 2003 Tokyo |date=November 2003}}

{{Rolls-Royce plc aeroengines}}

{{DEFAULTSORT:WR-21}}
[[Category:Aero-derivative engines]]
[[Category:Marine gas turbines]]