Rolls-Royce's XG-20

[stealth-uk]

http://www.flightglobal.com/pdfarchive/view/1985/1985%20-%201542.html

I have used the search function for the forum and I can`t find a topic, so I was hoping someone might have more information on this engine and whether it was seriously proposed for the RAF?

XG-20/Demo 20 Major improvements to the RB.199 are being tested in two demonstrator engines which produce 20 per cent higher reheat thrust and 15 per cent more dry thrust than the baseline engine. Rolls-Royce's XG-20 ran for the first time at the end of 1984. The engine could form the basis of a Tornado update engine. It could also be tested on EAP later in the programme.

 

[overscan (PaulMM)]

http://www.flightglobal.com/pdfarchive/view/1986/1986%20-%200865.html

Since 1982, three RB.199 demonstrator
programmes, fully funded by the
participating governments, have been
under way in the UK and West Germany.
Each gives the engine around 20 per cent
more thrust, and reduces reheat fuel burn.
Demo 1A is a Rolls-Royce-only
programme which enables testing of
features such as brush seals, powder
metallurgy discs, and single crystal high pressure
turbine blades. The engine also
incorporates the extended jet pipe of the
Mk 104. This led to the XG-20, also a
UK Ministry of Defence Rolls-Royce
programme, under Turbo-Union management,
which aims to demonstrate
performance improvements through
changes to the low-pressure compressor
and high-pressure turbine. XG-20 is also
fitted with the extended jet pipe, and
features digital engine control. The engine
ran for the first time at Rolls-Royce in
November 1984. The third demonstrator
engine, called Demo 20, ran at MTU in
April 1985. This has the short Mk 103-type
jet pipe and a West German Fadec developed
by MTU and BGT.
The improvements resulting from these
programmes will be fed into the national
engines to give higher thrust or longer life.
They will also result in an "Enhanced
RB.199", which could be available in
January 1989. This might become part of
a Tornado mid-life update programme,
and would also be appropriate as the
interim engine for the European Fighter
Aircraft. The RB.199 is currently in
competition with the General Electric
F404 to power India's light combat
aircraft and Japan's FSX.

 

[stealth-uk]

Thanks for the info.

 

[tartle]

This RB 199 XG-20 project did prime the XG-40 experiments that led to the EJ200

 

[JFC Fuller]

I don't know if the XG-20 configuration itself was proposed for the Tornado but many of the technologies tested in the programme were phased into the RB.199, such as the single crystal turbine blades, and as a consequence saved the RAF (and I assume other Tornado operators) considerable sums in maintenance costs; according to a 1998 Jane's article the savings were £38 million a year.

This RB 199 XG-20 project did prime the XG-40 experiments that led to the EJ200

I always thought the two programmes ran parallel, both being started in 1982? Talking of the RR XG-40; courtesy of the Indian DRDO: http://publications.drdo.gov.in/gsdl/collect/defences/index/assoc/HASH01af/2e9007ab.dir/doc.pdf

 

[Mike Pryce]

Rolls Royce had four demo programes prefixed XG in the 1980s.

XG.20 and XG.40 were for engines with 20% and 40% more thrust than the 'basic' RB.199 (Mk 103 IIRC)

XG.15 and XG.30 were for engines with 15% and 30% more thrust than the 'basic' Pegasus 11 (-21 IIRC).

XG.15 and XG.20 were uprated versions of the Pegasus and RB.199. Both were run, with XG.15 leading to the Pegasus 11-61.

XG.40 was run as per JFC's link. XG.30 was not run, but was a design based on a scaled XG.40 core with Pegasus-like fan (but using XG.40 technology levels) and optional PCB. It was to be the demo for the RB.532 for use on P.1216-41, and other designs to NST.6464 (more info in my P.1216 book).

The XG.40 and XG.30 were intended to lead to engines that could be used for Tornado and Harrier updates, and were therefore dimensionally similar in fan diameter to their predecessors, although wholly new.

Note that the RB.199 used a scaled Pegasus 11 fan, so all the designs had some links from the 1970s.

 

[tartle]

To clarify.. I was talking about the technologies not the demonstrators.. so single crystal started stimulated on the Rb211, moved across then up in power, which required the latest RB211 thinking on transonic turbines, etc.

 

[Mike Pryce]

Tartle is tight. The demo programmes were based on technology programmes such as Advanced Core Military Engine (ACME) and Hitech (IIRC high temperature core for RB.211) which ran from the 1970s.

RR had evolved a sensible approach to new technology by the mid 1980s, building demonstrators (both performance and durability) on the back of broad technology programmes, which then led to new engines. This both reduced (but did not eliminate) risk, and speeded things up in development.

It largely stemmed from problems on the RB.199 which led to Tornado flying with very immature engines, lots of development problems and constant change in the 'standard' of the production design, which was never the same as that being flight tested.

 

[tartle]

I believe the model adopted was based on the experiences of the High Temperature Demonstrator Unit (HTDU) at Derby in the 1970s. Intended to demonstrate the technology needed to REDUCE RISKS as the Turbine Entry Temperature (TET) was ramped up on the civil and military Spey, RB211 etc. The 'challenges' of the RB211 development programme meant that up until then most resources were concentrated on fixing the engine and not on extending it. As the Ministry was putting millions into the HTDU they were asking for results.
As a young designer on RB211 I looked to widening my experiences and had the opportunity to spend a year in the Stress Office. As most competent stress engineers (95 0f them) were involved in RB211 integrity I was given the job of supporting the HTDU integrity as the TET was ramped up from 1500 deg K to 1750 deg K and new (cast) blade materials were introduced. In the winter we could only run the HTDU on the Altitude Test Facility at night .... either that of Derby blacked out! By having a multidisciplinary team with a clear objectives (e.g. run 10 hours at 1650 deg K by August 1st) we got to 1750 deg K in 18 months, as wellas doing the day job.
I remember in the late 70s we were talking to a lot of people about how it was done so other programmes could take relevant experiences on board.