Eurojet, the consortium developing the Eurofighter's EJ200 engine, reaches a critical threshold this year, 10 years after its formation. In November it aims to achieve CICT - completion of initial certification testing - marking the transition from development to production.
"That really will be the end of our engineering programme and the start of real production," says Eurojet managing director Ken Greenall. "We are on track for that and we will have a production standard established in November." CICT "freezes the design for the production standard engine", he says.
Eurojet is slightly ahead of the game for CICT. Engines built to the final production standard, 03Z, are expected to be cleared for flight at the end of June. "We will fit three aircraft with these engines, although each one will also have an 03B standard engine," says Greenall. The earlier 03Bs are equal in performance, but do not have the weight and life improvements of production standard engines.
The first production engines are entering manufacturing and will be delivered in the middle of next year. Production is expected to reach 10 engines a month from 2001 onwards. Delivery of the first instrumented production aircraft in April 2001 is an important milestone, as it will be used to validate the production standard aircraft/engine combination.
Production contracts signed with the four Eurojet partners early last year finalised the workshare arrangements. Rolls-Royce has 36%, being responsible for the combustion system, high pressure (HP) turbine and intermediate casing, as well as participating in the low pressure (LP) and HP compressors, LP turbine, interstage support and afterburner.
MTU, with 30%, is responsible for the LP and HP compressors, as well as having part of the HP turbine and system design responsibility for the full-authority digital engine control unit (DECU). FiatAvio, with 20%, has the LP turbine, LP shaft, interstage support, gearbox, air/oil system and part of the afterburner. ITP, with the remaining 14%, concentrates on the convergent/divergent nozzle, jet pipe, exhaust diffuser and bypass duct.
Greenall says tests on 26 prototype engines have generated good results in 10,000h of bench running, including more than 2,500h at altitude test sites around Europe. "In addition, we have completed more than 3,000h of engine running in the aircraft," he adds.
"The flight programme has been very satisfactory, without any significant engine problems," he says. "We have enjoyed excellent reliability and have more than fully demonstrated the required handling characteristics." One achievement of the initial test phase was attainment of "supercruise" (supersonic cruise without afterburner). "We are talking more than Mach 1.1 in deceleration and acceleration," says Eurojet weapon systems integration manager Paul Herrmann.
The EJ200 is a two-spool turbofan with a thrust-to-weight ratio of 9:1, an overall pressure ratio of 26:1, and a bypass ratio of 0.4:1. Maximum dry thrust is 13,500lb (60kN), increasing to 20,000lb with afterburner.
The LP spool is made up of a three-stage fan driven by a single-stage turbine, while the HP system has a five-stage compressor driven by a single air-cooled turbine. Eurojet is keen to emphasise that the three stages in the fan module do not have variable inlet guide vanes. The fan unit consists of an overhung rotor with an all-blisk (integrally bladed disk) design. Each blisk uses three-dimensional aerodynamic design. The resulting wide chord blade means that snubbers, or clappers, are absent.
The HP compressor has only one stage of variable inlet guide vanes, with the actuating mechanism enclosed to prevent contamination. Shrouded vanes in the compressor have metallic-sprayed rotor seal fins and honeycomb static seals. The compressor is enclosed by an abradable casing coating, although contact is minimised by use of a tip clearance control system. The HP turbine also features tip clearance control as well as shroudless, cooled, single-crystal blades. The stator vanes in the turbine module are directionally solidified and protected with thermal barrier coatings on the inner and outer platforms. The LP turbines also have shrouded, cooled, single-crystal blades and stator vanes, which are similarly protected with thermal barrier coatings. The hollow stators accommodate the bearing support struts.
A single annular combustor lies at the core of the engine, which is surrounded by an annular bypass duct. The original combustor vapouriser design was changed to an air-spray can after improvements in technology led Eurojet to adopt the later innovation.
The afterburner consists of 15 primary burners with fuel vapourisers, 15 radial fuel manifolds and 15 air-cooled radial gutters. It also has a set of 15 cold-stream fuel sprayers, each with four fuel injectors. To reduce acoustic shock, the afterburner assembly is fitted with an air-cooled, "screech damper" heat shield.
The cam-roller-actuated convergent/divergent nozzle is made up of 24 pairs of master-slave petals. Each petal is film cooled with bypass air. Further protection is provided by a heat shield which separates the hot and cold exhaust streams.
Mounted on the engine, the DECU is fuel cooled, which improves overall performance, says Eurojet. "From the first flight onwards we were going ahead with 'carefree handling'. With the DECU it is simply 'turn and burn'. The pilots forget the engine, which is exactly what we want them to do," says Herrmann. "Our job is to deliver the weapon platform to the battle and back again, and ensure that the engine is not an issue," adds Greenall.
The EJ200's health is closely watched by an engine monitoring unit and oil debris monitoring system as part of rigorous efforts to extend installed life, improve maintainability and reduce recurring support costs. The engine specification calls for an overall life of 6,000h with a 4,500h limitation for some control parts. This is expected to translate into an average 25-year service life. The maintainability target is set at less than 0.5 maintenance hours per engine flight hour, while the scheduled maintenance interval is above 400h.
With the basic development virtually completed, Eurojet is increasingly looking towards further growth. The baseline engine is capable of producing up to 15% more dry thrust and 5% more afterburning power at a "war" rating with reduced life.
Looking further ahead, Eurojet has sketched out a roadmap with at least two major growth phases. Using improved three-dimensional aerodynamic design and enhanced core technology, it sees phase one providing up to 20% more dry thrust and 15% more afterburning thrust. This would be achieved by increasing the fan pressure ratio to 4.6:1 and mass flow by 10%. Diameter would remain unchanged.
A second phase would grow thrust, both dry and reheat, by 30%. This would involve more substantial HP spool improvements as well as further increases to both fan pressure ratio and flow. The outline timescale could see phase one development running from 2000 to 2005, with phase two following from 2005 to 2010.
A Spanish-designed thrust-vectoring nozzle was ground tested in mid-1998, but there are as yet no plans to install the nozzles on the Typhoon. "Eurofighter says the aircraft is agile enough, but we have to be ready," says Greenall. "If the UK wants to put the Eurofighter on an aircraft carrier, then that's when they will probably start to talk about it. So we are ready."
Source: Flight International
