Editing Napier Nomad

{{Short description|British diesel aircraft engine}}
{{Use dmy dates|date=October 2019}}
{{Use British English|date=December 2017}}
{|{{Infobox aircraft begin
 |name = Nomad
 |image= File:Napier Nomad.jpg
 |caption= Napier Nomad II
}}{{Infobox Aircraft Engine
 |type=[[Turbo-compound]]<br> [[aircraft engine|aero-engine]]
 |national origin=United Kingdom
 |manufacturer=[[Napier & Son]]
 |first run=[[1949 in aviation#October|October 1949]]
 |major applications=[[Avro Lincoln]] (test bed only)
 |number built = 
 |program cost = £5.1 million
 |unit cost = 
 |developed from = 
 |developed into = 
 |variants with their own articles = 
}}
|}

The '''Napier Nomad''' is a British [[diesel engine|diesel]] [[aircraft engine]] designed and built by [[Napier & Son]] in 1949. They combined a [[piston engine]] with a [[turbine]] to recover energy from the exhaust and thereby improve [[fuel efficiency|fuel economy]]. Two versions were tested, the complex '''Nomad I''' which used two propellers, each driven by mechanically independent stages, and the '''Nomad II''', using the turbo-compound principle which coupled the two parts to drive a single propeller. The Nomad II had the lowest [[specific fuel consumption (shaft engine)|specific fuel consumption]] figures seen up to that time.<ref name="Gunston, Encyc. Aero Engines, p106" >{{cite book
  |last=Gunston  |first=Bill  |authorlink=Bill Gunston
  |title=World Encyclopaedia of Aero Engines
  |location=Cambridge, England  |publisher=Patrick Stephens 
  |year=1989
  |isbn=1-85260-163-9
  |ref=Gunston, Encyc. Aero Engines
  |page=106
}}</ref> Despite this the Nomad project was cancelled in 1955 having spent £5.1 million on development, as most interest had passed to [[turboprop]] designs.<ref name="Flight, 17 August 1967, Cancelled projects list" >{{cite journal
  |journal=[[Flight (magazine)|Flight]] 
  |title=Cancelled projects: the list up-dated
  |url=http://www.flightglobal.com/pdfarchive/view/1967/1967%20-%201672.html
  |date=17 August 1967
  |page=262
  |ref=Flight, 17 August 1967, Cancelled projects list
  |url-status=dead
  |archive-date=March 5, 2016
  |archive-url=https://web.archive.org/web/20160305152115/https://www.flightglobal.com/pdfarchive/view/1967/1967%20-%201672.html
}}</ref>

== Design and development ==
[[File:Napier Nomad Model E. 145 Diesel Engine.jpg|thumb|At the [[Steven F. Udvar-Hazy Center]]]]
[[File:Napier Nomad I East fortune front.jpg|thumb|Napier Nomad 1]]
In 1945 the [[Air Ministry]] asked for proposals for a new {{cvt|6000|hp|MW}} class engine with good fuel economy. [[Curtiss-Wright]] was designing an engine of this sort of power known as the [[turbo-compound engine]], but Sir [[Harry Ricardo]], one of Britain's great engine designers, suggested that the most economical combination would be a similar design using a diesel two-stroke in place of the Curtiss [[gasoline|petrol]] engine.

Before [[World War II]] Napier had licensed the [[Junkers Jumo 204]] diesel design to set up production in the UK as the [[Napier Culverin]], but the onset of the war made the [[Napier Sabre|Sabre]] all-important and work on the Culverin was stopped. In response to the Air Ministry's 1945 requirements Napier dusted off this work, combining two enlarged Culverins into an [[H engine|H-block]] similar to the Sabre, resulting in a massive 75&nbsp;litre design. Markets for an engine of this size seemed limited, however, so instead they reverted to the original Sabre-like [[Flat engine|horizontally opposed]] 12 [[Cylinder (engine)|cylinder]] design, and the result was the Nomad.

The objective of the design was to produce a civilian power plant with far superior fuel efficiency to the emerging jet engine. [[Thermal efficiency]] is given by <math>1 - T_e/T_p</math>, where ''T''{{sub|e}} is the exhaust temperature in [[kelvin]]s<!-- pluralized – see Kelvin#Usage conventions --> and ''T''{{sub|p}} is the peak combustion temperature. Jet engines have relatively low-temperature combustion systems which produce a ''T''{{sub|p}} of no more than about 1,000&nbsp;K, much less than the typical 5,000&nbsp;K of a reciprocating engine, and so jets have very poor thermal efficiency. The Nomad design focused on replacing the low-temperature combustion chambers of the jet engine with highly efficient Diesel combustion chambers. In practice, it was much too difficult to couple the diesel power output back into the turbine cycle. The maximum practical power of the Nomad was {{cvt|4000|hp|MW}}, and it was much heavier than a pure jet of the same power. By this time civilian jets such as the [[Boeing 707]] were nearing completion, and the Nomad was never seriously considered by any aircraft manufacturer.

===Nomad I===
[[File:NomadSchematic 185kBpng360kB.png|thumb|right|Schematic drawing of Napier Nomad I and II.]]
The initial Nomad design (E.125) or Nomad 1 was incredibly complex, almost two engines in one. One was a [[Twincharger|turbo-supercharged]] two-stroke diesel, having some resemblance to half of a [[Napier Sabre|Napier Sabre's]] [[H engine|H-24]]. Mounted below this were the rotating parts of a [[turboprop]] engine, based on the [[Napier Naiad|Naiad]] design, the output of which drove the front propeller of a contra-rotating pair. To achieve higher boost, the crankshaft drove a centrifugal supercharger, which also provided the scavenging needed for starting the engine from rest. During take-off additional fuel was injected into the rear [[turbine]] stage for more power, and turned off once the aircraft was cruising.{{sfnp|Lumsden|2003|page=170}}

The compressor and turbine assemblies of the Nomad were tested during 1948, and the complete unit was run in October 1949. The prototype was installed in the nose of an [[Avro Lincoln]] [[heavy bomber]] for testing: it first flew in 1950 and appeared at the [[Farnborough Air Display]] on 10 September 1951.{{sfnp|Lumsden|2003|page=172}} In total the Nomad I ran for just over 1,000 hours, and proved to be rather temperamental, but when running properly it could produce {{cvt|3000|hp|MW}} and {{convert|320|lbf|kN|abbr=on}} thrust. It had a [[specific fuel consumption (shaft engine)|specific fuel consumption]] (sfc) of {{convert|0.36|lb/hph|g/kWh|abbr=on}}.

The prototype Nomad I is on display at the [[National Museum of Flight]] at [[East Fortune|East Fortune Airfield]] in [[Scotland]].

===Nomad II===
[[File:Napier Nomad ¾ front view.jpg|thumb|Front three-quarter view of a Nomad II]]
[[File:Napier Nomad Plan view.jpg|thumb|Topside view]] 
Even before the Nomad I was running, its successor, the '''Nomad II''' (E.145) Nomad 6, had already been designed. In this version an extra stage was added to the axial compressor/supercharger, eliminating the separate centrifugal part and the intercooler. The turbine (which also received an additional stage) was now only used to drive the compressor, and feed back any excess power to the main shaft using a [[Beier variable-ratio gear]];{{sfnp|''Flight'' (30 April 1954)|page=549}} the separate propeller from the turbine was deleted, just as the whole of the "[[afterburner]]" system with its valves etc. So the system was now like a combination of a mechanical [[supercharger]], and a [[turbocharger]] without any need for bypass. The result was smaller and considerably simpler: a single engine driving a single propeller.{{sfnp|Lumsden|2003|page=171}} Overall weight reduction was {{convert|1000|lb|abbr=on}}. The [[wet liner]]s of the cylinders of the Nomad I were changed for [[dry liner]]s.{{sfnp|''Flight'' (30 April 1954)|page=550}}

While the Nomad II was undergoing testing, a prototype [[Avro Shackleton]] was lent to Napier as a testbed. The engine proved bulky, like the Nomad I before it, and in the meantime several dummy engines were used on the Shackleton for various tests.

On an equivalent power basis, the Nomad II had an SFC of {{cvt|0.327|lb/hph|g/kWh}} at {{cvt|25000|ft}} cruise altitude.<ref name="DP195409">{{cite magazine |issn=1040-8878 |magazine=Diesel Progress |title=What's going on in England: Napier Nomad |url=https://archive.org/details/sim_diesel-progress_1954-09_20/page/56 |pages=56, 58 |publication-date=September 1954 |given=Hamish |surname=Ferguson}}</ref>

A further development, the Nomad Nm.7, of {{cvt|3500|shp|MW}} was announced in 1953.<ref name="FI19531106">{{cite magazine |url=http://www.flightglobal.com/pdfarchive/view/1953/1953%20-%201456.html |magazine=[[Flight International|Flight]] |title=Here and there |publication-date=November 6, 1953 |page=610 |url-status=dead |archive-date=April 13, 2016 |archive-url=https://web.archive.org/web/20160413032333/https://www.flightglobal.com/FlightPDFArchive/1953/1953%20-%201456.PDF}}</ref>

By 1954 interest in the Nomad was waning, and after the only project, the [[Avro Shackleton|Avro Type 719 Shackleton IV]], based on it was cancelled, work on the engine was ended in April 1955, after an expenditure of £5.1 million. The design was also considered for the [[Canadair Argus]], a similar [[maritime patrol aircraft]] being designed for the [[Royal Canadian Air Force]]. This design turned to the [[Wright R-3350 Duplex-Cyclone|Wright R-3350]], the design the Nomad was intending to best.

A Nomad II is on display at the [[Steven F. Udvar-Hazy Center]] in [[Virginia]].<ref>[https://airandspace.si.edu/collection-objects/napier-nomad-model-e-145-horizontally-opposed-diesel-engine/nasm_A19640017000 Steven F. Udvar-Hazy Center - Napier Nomad] Retrieved: 7 April 2020</ref>

==Applications==
* [[Airspeed Ambassador]] (planned only)<ref>{{Cite journal
  |journal=[[Flight (magazine)|Flight]] 
  |date=17 April 1953
  |title=Aircraft intelligence: Great Britain
  |url=http://www.flightglobal.com/pdfarchive/view/1953/1953%20-%200489.html
  |page=485
  |url-status=dead
  |archive-date=April 16, 2016
  |archive-url=https://web.archive.org/web/20160416181604/https://www.flightglobal.com/FlightPDFArchive/1953/1953%20-%200489.PDF
}}</ref>
* [[Avro Lincoln]] (test bed only)
* [[Avro Shackleton]] (planned only)
* [[Canadair CP-107 Argus]] (planned only)

== Specifications (Nomad II)==
{{pistonspecs
|type=Twelve-cylinder, two-stroke valveless [[diesel engine]] compounded with three-stage turbine driving both [[crankshaft]] and [[axial compressor]].
|ref=''Flight'' 1954<ref name="Flight, 30 April 1954, Napier Nomad" >{{cite journal
  |journal=[[Flight (magazine)|Flight]] 
  |last=Gunston  |first=Bill  |authorlink=Bill Gunston
  |title=Napier Nomad: An engine of outstanding efficiency
  |url=http://www.flightglobal.com/pdfarchive/view/1954/1954%20-%201215.html
  |date=30 April 1954
  |pages=543–551
  |ref={{harvid|Flight (30 April 1954)}}
  |access-date=18 December 2009
  |url-status=dead
  |archive-date=October 8, 2012
  |archive-url=https://web.archive.org/web/20121008202652/http://www.flightglobal.com/pdfarchive/view/1954/1954%20-%201215.html
}}</ref>
|bore={{convert|6.00|in|mm|abbr=on}}
|stroke={{convert|7.375|in|mm|abbr=on}}
|displacement={{convert|2502|in3|L|1|abbr=on}}
|length={{convert|119|in|mm|abbr=on}}
|diameter=
|width={{convert|56.25|in|mm|abbr=on}}
|height={{convert|40|in|mm|abbr=on}}
|weight={{convert|3580|lb|kg|abbr=on}}
|valvetrain=Piston ported [[Two-stroke engine|two-stroke]]
|supercharger=[[Napier Naiad]] [[turboshaft]] and gas generator, maximum boost pressure 89 psi
|turbocharger=Engine exhaust gases ducted in to Naiad turbine section   
|fuelsystem=
|fueltype|Diesel oil or kerosene or wide-cut petrol or "other fuels"
|oilsystem=
|coolingsystem=[[Radiator (engine cooling)|Liquid-cooled]]
|power={{convert|3150|hp|kW|abbr=on}} max take-off at {{convert|89|psi|kPa|abbr=on}} boost not including 320 lbf residual [[thrust]] from the turbine at 2,050 [[Revolutions per minute|rpm]] (crankshaft) and 18,200 rpm (turbine) 
|specpower={{convert|1.25|hp/in3|kW/L|abbr=on|}}
|compression=8.1 (cylinder ratio), 31.5:1 (overall pressure ratio)
|fuelcon=
|specfuelcon=0.345 lb/(ehp·h) (0.210 kg/(kW·h)) (combined unit) at 11,000 ft and 300 kn
|oilcon=
|power/weight={{convert|0.88|hp/lb|kW/kg|abbr=on}}
}}

===Turbine section===
{{jetspecs
<!-- If you do not understand how to use this template, please ask at [[Wikipedia talk:WikiProject Aircraft]] -->
<!-- Please include units where appropriate (main comes first, alt in parentheses). If data are missing, leave the parameter blank (do not delete it). For additional lines, end your alt units with )</li> and start a new, fully-formatted line with <li> -->
|type=[[Gas generator]] based on [[Napier Naiad]]
|length=
|diameter=
|weight=
|compressor=12-stage [[axial compressor|axial]] flow
|combustion=
|turbine=3-stage [[Axial turbine|axial flow]]
|fueltype=
|oilsystem=
|power=
|thrust=320 lbf residual at 18,200 rpm
|compression=8.25:1
|aircon={{cvt|13.0|lb/s|kg/s}}
|turbinetemp=
|fuelcon=
|specfuelcon=
|power/weight=
|thrust/weight=
}}

==See also==
{{aircontent
<!-- other related articles that have not already linked: -->
|see also=

<!-- designs which were developed into or from this aircraft: -->
|related=

<!-- aircraft that are of similar role, era, and capability as this design: -->
|similar aircraft=

<!-- relevant lists that this aircraft appears in: -->
|lists=
*[[List of aircraft engines]]

<!-- For aircraft engine articles.  Engines that are of similar to this design: -->
|similar engines=
*[[Rolls-Royce Crecy]]
*[[Dobrynin VD-4K]]
<!-- See [[WP:Air/PC]] for more explanation of these fields. -->
}}

==References==
{{Reflist}}

*{{cite book
  |last=Lumsden  |first=Alec
  |title=British Piston Engines and their Aircraft
  |publisher=Airlife Publishing  |location=Marlborough, Wiltshire
  |year=2003
  |isbn=1-85310-294-6
  |pages=170–172
}}
*https://www.thegrowler.org.uk/avroshackleton/the-nomad-proposal.htm – ''The Nomad Proposal'', research by Chris Ashworth – it was amongst the original sources of the article according to the history
*{{cite magazine |issn=0005-2175 |magazine=[[Aviation Week]] |title=Compound diesel engine design analyzed |url=https://archive.org/details/sim_aviation-week-space-technology_1954-05-17_60_20/page/30 |department=Aeronautical Engineering |pages=30–32, 34 |publication-date=May 17, 1954 |volume=60 |number=20}}
*{{cite magazine |issn=0005-2175 |magazine=[[Aviation Week]] |title=New Nomad's fuel appetite is small |url=https://archive.org/details/sim_aviation-week-space-technology_1953-04-06_58_14/page/30 |department=Aeronautical Engineering |pages=30–32, 37–38, 41 |publication-date=April 6, 1953 |volume=58 |number=14 |given=David A. |surname=Anderton}}
*{{cite magazine |issn=0005-2175 |magazine=[[Aviation Week]] |title=Weak production handcuffs British air |url=https://archive.org/details/sim_aviation-week-space-technology_1951-10-08_55_15/page/12 |department=Farnborough Verdict |pages=12–15 |publication-date=October 8, 1951 |volume=55 |number=15 |given=David A. |surname=Anderton}}

==External links==
{{Commons category|Napier Nomad}}
*[http://www.enginehistory.org/Piston/Napier/napier.shtml Aircraft Engine Historical Society photo gallery of Napier piston engines]
*{{cite magazine |author=D. Napier and Son Limited |url=http://www.flightglobal.com/pdfarchive/view/1952/1952%20-%201121.html |title=Napier Nomad |publication-date=April 25, 1952 |magazine=[[Flight International|Flight]] |page=35 |url-status=dead |archive-date=March 28, 2015 |archive-url=https://web.archive.org/web/20150328122318/http://www.flightglobal.com/FlightPDFArchive/1952/1952%20-%201121.PDF}}
*{{cite magazine |url=http://www.flightglobal.com/pdfarchive/view/1953/1953%20-%200350.html |title=NOMAD NNm6: Napiers' new compounded engine |page=348 |publication-date=March 20, 1953 |magazine=[[Flight International|Flight]] |url-status=dead |archive-date=May 18, 2014 |archive-url=https://web.archive.org/web/20140518084225/http://www.flightglobal.com/FlightPDFArchive/1953/1953%20-%200350.PDF}}
*{{cite magazine |url=http://www.flightglobal.com/pdfarchive/view/1961/1961%20-%200750.html |title=Napier, Luton... |publication-date=April 1, 1961 |magazine=[[Flight International|Flight]] |pages=760–761 |url-status=dead |archive-date=March 5, 2016 |archive-url=https://web.archive.org/web/20160305171930/https://www.flightglobal.com/pdfarchive/view/1961/1961%20-%200750.html}}

{{Napier aeroengines}}

[[Category:Napier aircraft engines|Nomad]]
[[Category:Turbo-compound engines]]
[[Category:Aircraft diesel engines]]
[[Category:Flat engines]]
[[Category:1940s turboprop engines]]
[[Category:Two-stroke aircraft piston engines]]
[[Category:1940s aircraft piston engines]]
[[Category:Diesel engines by model]]
[[Category:Diesel engines by maker]]
[[Category:Avro Shackleton]]