FlightGlobal.com
Home
Premium
Archive
Video
Images
Forum
Atlas
Blogs
Jobs
Shop
RSS
Email Newsletters
You are in:
Home
Aviation History
1982
1982 - 0026.PDF
propulsion Rolls-Royce announces improved RB.211-535E4 ANOTHER round of improvements to Rolls-Royce's RB.211-535 puts claimed fuel burn of the E4 version in the same class as that of the competing engine for the Boeing 757, Pratt & Whitney's new PW2037. R-R adds that more improvements are in the pipe line to keep their small RB.211 turbo- fan competitive, and to give the en gine growth potential to 40-45,0001b thrust. The principal advance has been in the application of new three-dimen sional flow analysis methods in the design of compressor and turbine blades to operate more efficiently at roots and tips, where boundary layer losses are greatest. High-pressure (HP) compressor blades resulting from the new tech nique are called "end bended", be cause the tips are twisted to improve control of secondary (i.e. tip) losses in the compressor duct. Towards the back of the HP compressor, the boundary layer builds up to around 20 per cent of blade height and sig nificantly reduces blade efficiency. Three-dimensional computer analysis has also resulted in modifica tion of blade surface shape to reduce Mach numbers as air flows through passages and around blades. This "controlled diffusion" (the same term as Pratt & Whitney uses for its own blade contouring technique) will, along with the end bending, improve compressor efficiency to the point where the overall pressure ratio of the engine approaches 30:1—the quoted figure for the PW2037. All RB.211-535E4s will feature the better blades. Belter turbine efficiency In the turbine, work has centred on improving airflow over the wide- chord, low aspect ratio intermediate pressure (IP) turbine nozzle guide vane. The vane is wide because it belongs to an assembly that houses the rear IP shaft bearing, and has therefore, says Rolls-Royce, benefited particularly from new 3D viscous flow analysis to cut losses and smooth the airflow into the rest of the tur bine. The technique has also been applied to learn more about what happens to the turbulent cooling air exhausted from the rows of cooling holes in HP turbine blades. Two further developments have im proved the thermal barrier coating which protects HP turbine blades and vanes from combustor heat. Oxidation resistance of the bonding substance that joins the ceramic coat to the 28 S 111 i ^INL RB.21 l-535Cs ready for despatch to Seattle. The £4 version will be available for service entry in late 1984. Early -S3SC customers will have the option to convert to -535E4 standard later blade substrate is uprated, and a better ceramic has been introduced to withstand higher temperatures and protect the bonding from the tem perature extremes that cause oxida tion—and unsticking. On the -535E4, only the pressure surface of the tur bine blades will be thermal barrier coated, not the leading edge. Leading edges will, however, have to be treated in future, more powerful ver sions of the -535. Rolls-Royce is now talking seriously about single crystal blades on RB.211s. but says that their introduction will not be needed until the -535E4 is de veloped to give 45,00Olb thrust. Single crystal technology, which will enable turbine entry temperatures to be raised by about 40°C, is said to be no problem—the manufacturing method follows from the company's experi ence with directionally solidified blades. Single crystal blades would, says R-R, be applied first in the un- cooled intermediate-pressure turbine. Film cooling of E4 combustor walls will be improved with the introduc tion of machined "Z rings". The rings meter air to the inner surface of the combustor, and the better design frees more air for control of the tempera ture profile across the combustor, which in turn means improved fuel burn and less emissions—although R-R says that E4 emissions perform ance is well below Icao's 1986 level. Different exhaust nozzle configura tions for the -535E4 are still being studied. Significantly, the idea of the common nozzle (in which the fan cowling is elongated so that fan and core air is mixed before exhausting) is to be extended to cater for long- range versions of the engine. A high degree of exhaust mixing helps long- range cruise performance, says R-R, and various forced mixers are being tried. But for the engines fitted to short-range aircraft, the common nozzle as it stands will be preferred, since its principal benefit is at take off, when the effect of the nozzle is to bring the fan closer to its optimum operating point. Another gain with the common nozzle is that reverse thrust is increased by 40 per cent. Full authority digital engine control (Fadec) is on the way for the RB.211. Rolls-Royce is aiming at "around 4 1986" for introduction of Fadec on -535s. but -535 programme manager David Pickerell stresses that Fadec must be absolutely proven for twin- engined reliability. The current super visory system is, he adds, just as accurate in its metering, but is heavier because of its hydromechanical back up. Besides working hard with Douglas on engining DC-10-10s with a 41,0001b -535E4, Rolls-Royce has several other -535 applications in mind, and seems confident that the engine has a healthy future. Hoped- for uses now include the four- engined Airbus TA11 and Boeing's 747SP. Engined with the -535E4, the latter aircraft would burn up to ten per cent less fuel over a 5,000-mile stage than RB.211-524B2 versions, claims R-R. On the Boeing 757, for which the RB.211-535 is the lead engine, R-R has drawn a curve which shows the similarity of early 757 sales to those of the Boeing 727 which it replaces.^ The hope is that sales of the new air craft will exceed 2,000 units by the end of the century. FLIGHT International, 2 January 1982
Sign up to
Flight Digital Magazine
Flight Print Magazine
Airline Business Magazine
E-newsletters
RSS
Events
