Rolls-Royce: Trent engines
At the heart of the Rolls-Royce civil aerospace business sits the Trent family of engines. The first Trent 700 engine entered service with Cathay Pacific in 1995 and there are now more than 1,800 Trent engines in operation giving the company a 50% market share of modern wide bodied jets...and there are a further 2,400 on order.
This position has been reached by a consistent investment in technology and making innovation “business as usual.”
Typically, six years ahead of time, Rolls-Royce will commit to an aircraft manufacturer the exact day on which the newly developed and certified engine will enter service. It will include technologies which have never before been proven in commercial service and will guarantee among other things, how much the engine will weigh, how much noise it will make and how much fuel it will consume – but only to the nearest percent. And of course it will be completely safe to carry 300 plus passengers for many years.
The company then project manages hundreds of millions of dollars of research and development expenditure, 2000 scientists and engineers, 300 test rigs, and a development programme which will run, test, examine and, in some cases, destroy 9 full engines over 18 months of frenetic activity.
The team involved is no less complex or accomplished – linked with research institutions and universities it requires the skills of material scientists, physicists, chemists, metallurgists, mathematicians, aerodynamicists, aerospace engineers, manufacturing & process engineers, procurement specialists and logisticians to name but a few.
All of which means the Trent family has a new product Entry Into Service each year out to 2015.
There are 18,000 components in the company’s latest engine – the Trent 1000. Each one is manufactured to withstand the extraordinary performance demands placed on them.
An example is the high pressure turbine blade. This blade is grown as a single crystal of a Rolls-Royce alloy in a vacuum furnace. As it grows, it incorporates a complex series of air passages to cool the blade. Then it needs external cooling holes created by incredibly accurate laser drilling. And on top of all that is a thermal barrier coating that surpasses that used to make the tiles on the space shuttle.
The blade lives in the high-pressure turbine, where the gas temperature is at least 400 degrees above the melting point of the blade’s alloy. It sits in a disc that rotates at more than 10,000 rpm. This means that the force on the blade root is the same as hanging a London double-decker bus from its tip. Every time the plane takes-off this single blade develops the same horsepower as a Formula 1 racing car, and yet it can travel 10 million miles before it needs replacing.
That sort of performance, achieved under such extremes of heat and pressure requires a precision of design and manufacture that is measured in microns – to the thickness of a human hair, and it has to be exactly right every time.
At the opposite end of the spectrum is the hollow titanium fan blade. The hollow titanium fan blade is crucial to the performance and efficiency of Rolls-Royce large aero engines and to an engineer; it’s a work of art. Moving a tonne of air per second, the fan produces over 85% of the engine’s thrust.
Back in the 1980s, Rolls-Royce took the view that the fan diameter of aero engines would continue to grow and that the key to future success would be the ability to produce a fan blade that was lighter and stronger than previous blades. Titanium is the material that has the right combination of low density and high strength. But to deliver the large improvements required in the strength and performance of future blades Rolls-Royce still needed to develop two novel manufacturing techniques.
First, at an atomic level, three sheets of titanium material, are fused. It has to be done in an ultra-clean production facility through a process of diffusion bonding, for which the company has more than 60 patents registered worldwide.
Then the process of superplastic forming creates a hollow within the blade. Argon gas is used to inflate the titanium in a furnace operating at almost 1000°C. The two outer titanium panels are expanded, while the middle sheet is stretched into a zig-zag shape, creating the final hollow 3D aerodynamic shape of the blade and giving extraordinary rigidity to the structure.
It took over ten years of development to get to the stage where a stable production process at the precision demanded could be assured. All in all, about 80 processes are involved in producing the hollow titanium fan blade that results in the very lightweight but exceptionally strong design. By securing some critical patents the company has been able to protect the major performance benefits that gives it an edge over competitors’ designs.
While the raw materials are critical, the added value comes from developing the innovative technologies and processes that deliver a final product with the capability to do some amazing things which couldn’t be dreamt of before. It’s a “crown-jewel” technology for Rolls-Royce and has been at the core of the development of the large civil aerospace engines the company manufactures.
The story of innovation continues. The hollow titanium fan blade coupled with linear friction welding – another Rolls-Royce patented technology – made it possible to join the blade to the disk creating a single integrated structure, called a blisk or ‘bladed disk’.
That innovation has enabled weight reductions of 30% and with that comes greater performance and fuel efficiency. The blisk played a key role in enabling Rolls-Royce to act as a primary contributor to the Joint Strike Fighter programme. In time, the company expects the blisk to be integrated into future civil aerospace products and become as core to the business as the hollow titanium fan blade has been. The greatest challenge if all is to integrate them into a complete engine optimised for the airframe it powers.
However, Rolls-Royce does not just sell engines. These days customers want the services to look after engines on the wing; 24 hours a day, 365 days a year, anywhere in the world.
The company’s services business is built on the intelligent use of a phenomenal amount of data. Rolls-Royce typically measures around 20 performance parameters on a Trent engine such as vibration levels, oil pressure and temperature. The company has about nine gigabytes of data per day streaming into their data centres, which equates to half a billion data reports a year. The data is analysed as it flows in, with trends extrapolated and anomalies detected. It not only gives the company early warning on fault diagnosis, but equips it to help its airline customers to schedule maintenance more cost efficiently.
The Rolls-Royce Engine Health Monitoring Unit is an extremely complex software set that takes signals from dozens of sensors around the engine and transmits the data via satellite while the aircraft is in flight. The company’s service engineers are therefore alerted to potential issues early, in advance of them causing an operational problem to the airline. If repairs are necessary, the company can have a field team standing by on the ground by the time the plane lands. In this way Rolls-Royce is saving the customer down time, minimising disruption, keeping the engine in service, and keeping the passengers flying.
A Rolls-Royce powered aircraft takes off or lands ever 2.5 seconds. The company’s engines power 5.5 million flights every year travelling 12 billion miles and at any one time 200,000 passengers are flying on Rolls-Royce powered planes.
The company has over 13000 engines in service with more than 500 customers on over 30 different types of aircraft.
These engines have helped power the Civil Aerospace business of Rolls-Royce to revenues of £4.919m in 2010 and a firm and announced order book of £48.5bn.
Civil Aerospace is just one part of a business with overall revenues of £10.8 billion in 2010. The company’s other businesses supply 160 armed forces, more than 2,500 marine customers including 70 navies, plus energy customers in nearly 120 countries, with an installed base of 54,000 gas turbines. All of these businesses contributes to a firm and announced order book of £61.4 billion (at the end of June 2011).
The aviation industry accounts for around 2% of man-made CO2 emissions. Increased demand for aviation around the world means that CO2 emissions are set to increase and Rolls-Royce wants to play a significant part in helping to mitigate this by developing efficient power systems and reducing the environmental impact of the industry.
Improving the efficiency of engines isn’t something that’s new to Rolls-Royce. The company has been doing that steadily for a long time now. For example, the fuel consumption of the Trent XWB, the latest addition to the Trent family, is 16% lower than the Trent 700 which entered service in 1995. And the company is intent on continuing to drive that down further.
For engine designers the most efficient engine design is a question of balance. Higher overall pressure-ratio cycles improve fuel burn, thereby reducing CO2, but the propensity to create NOx increases. Similarly, improvements in noise brought about by increasing the bypass ratio of turbofan engines, may add weight and drag of the increasingly large low-pressure systems resulting in higher overall fuel burn, and hence increased CO2.
To succeed, the whole industry must work together, pooling its innovation and applied research in both products and processes. Increasingly fuel-efficient engines must play a big part but so too must advances in airframe technology and improved air traffic management and operations. Never has collaborative teamwork been so vital.
An example of that collaboration is the Boeing 787, which has as much as 50 percent of the primary structure - including the fuselage and wing - made of composite materials. The aircraft is powered by the Rolls-Royce Trent 1000 engine which when it entered service, with ANA, was the cleanest, quietest lightest and most efficient engine for the aircraft.
If, overnight, we could replace a previous generation of planes, for example the 767, with the 787 we could save over $1.5 billion in fuel costs and 5 million tonnes of CO2 every year.
The Trent 1000, which entered service in 2011, is the fifth engine in the Trent family and the work of hundreds of the 11,000 engineers employed by Rolls-Royce worldwide.
Andy Geer has been the Chief Engineer on theTrent 1000 since 2004, having previously experienced the other end of the civil gas turbine project lifecycle as Chief Engineer for the Boeing fleet engines, as well as having worked on transmissions, controls and functional aspects.
He was supported on the certification and service preparation stages of the Trent 1000 project by Assistant Chief Engineer Stuart Ellis, Chief Design Engineer Jerry Goodwin, Chief Development Engineer Dave Benbow, Chief Performance Engineer, Mike Page and many other technical leaders and skilled staff engineers in Rolls-Royce and partner companies worldwide.
Developed specifically for the world’s largest passenger jet, the Airbus A380, the Trent 900 met challenging time, budget and performance specifications. Its novel swept fan blades produce highly efficient propulsion while minimising noise and advanced analytical techniques improve noise control within the engine ducts.
Consequently the quieter Trent 900 is now the preferred engine for more than 70 percent of all A380 operators, which are able to carry around about three times the number of passengers compared to an aircraft of the 1980s and 90s at similar approach and flyover noise levels. The engine has a type rating up to 80,000lb thrust (around the same amount of thrust as 850 family cars) to meet the expected performance targets and future aircraft developments. It also draws in enough air to inflate 72,000 party balloons in just one second.
Since the Trent 900 entered service with the launch customer, Singapore Airlines, in 2007, it has accumulated over nearly 900,000 hours of operation.
Rolls-Royce engineers were chosen to design the launch engine for Boeing’s 787 Dreamliner project in 2004. The Dreamliner claims to be the quietest, cleanest and most fuel-efficient airframe and engine partnership flying. It has been certified to produce 74,000 lbs of thrust.
The slower fan speed and low jet velocity of the Trent 1000 reduce noise. The continued development of the tiled combuster, first used on the Trent 900, reduces emissions of CO2 and NOx.
The Trent 1000 is a bleedless engine to suit the requirements of the more electric Boeing 787. This offers reductions in fuel burn and weight for the overall aircraft. In addition increased levels of electrical energy are transferred to the aircraft via a new Intermediate Pressure Offtake.
New technology has been used to improve the component life of the Trent 1000. Examples include soluble core High Pressure turbine blades and new materials for discs and shafts. A more advanced Engine Health Monitoring System tracks a lot more parameters to understand engine behaviour more deeply and helping airline customers to schedule maintenance more cost efficiently.
The Rolls-Royce Trent 1000 has been ordered by Air Astana, Air China, Air Europa, Air New Zealand, Air Niugini, Arkia, ANA, Avianca, Aviation Capital Group, British Airways, CIT, Delta, ILFC, LAN, LOT, Norwegian, Royal Brunei, Virgin Atlantic.
Set to enter into service in 2013 and designed for the Airbus A350 XWB, the Trent XWB will set new standards for efficiency, lifecycle cost and environmental impact. The engine, with a thrust of up to 97,000lb, incorporates technology from the previous five members of the Trent family as well as a contra-rotating high pressure system, low hub-tip ratio swept fans and new materials technology with advanced engine health monitoring systems to maximise time on wing.
The Trent XWB has been the fastest-selling Trent family member to date.