Composites make for greener aircraft engines

Although the contribution of air transport to man-made greenhouse gases is only 2%, this figure is expected to increase to 3% by 2050. (Picture © egd.)
Although the contribution of air transport to man-made greenhouse gases is only 2%, this figure is expected to increase to 3% by 2050. (Picture © egd.)

As part of its strategy to become a leader in lightweight structures, Volvo Aero, Sweden,  recently acquired Swedish company Applied Composites AB (ACAB)  in Linköping. Volvo Aero aims to use ACAB's technology to develop and manufacture lightweight aircraft engine components in composite materials. It says it will invest approximately SEK50 million in composites research and development during the next 18 months.

“The acquisition is part of our investment in lightweight technologies, which will result in reduce fuel consumption and, consequently, lower emissions from aircraft,” says Olof Persson, President of Volvo Aero.

Volvo Aero, part of the Volvo group, intends to establish a new operation that  will develop and manufacture selected aircraft engine components in composites. These components will be significantly lighter than comparable components in metal and will then significantly influence the fuel consumption and, thereby its carbon dioxide emissions.

The new operation at ACAB will start work immediately.

Volvo Aero develops and manufactures components for aircraft and rocket engines. It offers a range of services, including sales of spare parts for aircraft engines and aircraft, sales and leasing of aircraft engines and aircraft, as well as overhaul and repair of aircraft engines. The company employs lightweight metals (titanium and aluminium) and carbon fibre composites.


Volvo Aero concentrates on making large parts for large engines, says Anders Lundbladh, research engineer, in the company's Environment magazine.

“Our main task is to reduce the weight of engine components,” he says. “If engine components are made lighter then we can also build more efficient engines, while engines with old technology would be too heavy.”

The company mainly works with stationary components – compressor shells, turbine housings and frames – and is trying to find new ways of manufacturing them.

“So far it's been common to cast components using a single material,” he says. “If on the other hand we weld a frame together we can choose between different types of material that would make the product lighter overall. Another possibility is to exchange selected components for ones made from composite materials. If we used carbon fibre for example, which is stronger than steel, and mixed it with different plastics, the material could be just as strong as aluminium. This would make these components between 10 and 30% lighter.”

Titanium and nickel base alloys are the two most common materials the company uses today. Titanium is used for cold parts, such as the casing; nickel-base alloys are used for hotter areas.

According to Lundbladh, there are four important trends in the engine industry to improve fuel efficiency. The first is to make fans bigger, which gives the engines better traction in the air. The second is to increase pressure in the engines to turn fuel energy into mechanical energy more efficiently. The third trend is to make the geometry of the blades in the fan and compressor more complicated. For example, by creating curved blades or sweeping blades so they lean both forwards and backwards, the airflow becomes smoother and less energy is used. The fourth trend involves using the heat emitted by the engine.

Volvo Aero is a partner in the GE GEnx engine, which is being developed for Boeing's new 787 Dreamliner aircraft as well as for the Boeing 747-8 aircraft. The GEnx is claimed to deliver 15% better fuel consumption than the engines it replaces and its emissions are roughly 94% below 2008 regulatory limits. It will also be 30% quieter than comparable current engines available today. The fan case and fan blades will be made of composite material.


Volvo Aero is one of the partners of the VITAL European research and development (R&D) programme. which aims to develop technologies that reduce engine noise by 6 decibels (dB) and carbon dioxide (CO2) emissions by 7%. It believes that these ambitious goals can only be achieved through significant technological breakthroughs. At the same time, VITAL aims to develop ways to reduce the engine's weight, thereby reducing both fuel consumption and CO2 emissions.

Clean sky

The Clean Sky Joint Technology Initiative (JTI) will be officially launched at an event in Brussels, Belgium, next month. It will be one of the largest European research projects ever, with an estimated budget of €1.6 billion shared equally between the European Commission and industry, over the period 2008-2014.

Air transport is an important sector in the EU economy. According to Clean Sky, studies show that the industry accounts for approximately 2.5% of gross domestic product (GDP), creates (directly and indirectly) over 3 million jobs, and contributes in excess of €30 billion to a positive trade balance for Europe. The indirect economic and social impact of the sector is even greater. Based on projected growth, over the next 20 years, air transport could contribute an additional 1.8% of GDP to the EU (equivalent to €200 billion per year).

The Stern review recently published in the UK has shown that the economic cost of inaction on the environment could be a reduction of global GDP by 20%. The report highlighted the need to support the development of a range of low carbon emission and high efficiency technologies on an urgent timescale.

It takes more than a decade to develop a new generation of aircraft and aircraft in service for more than 30 years. Clean Sky will aim to accelerate the introduction of green technologies in new generation aircraft. The project will aim to demonstrate and validate the technology breakthroughs that are necessary to make major steps towards the environmental goals sets by ACARE (Advisory Council for Aeronautics Research in Europe) and to be reached in 2020:

  • 50% reduction of CO2 emissions through drastic reduction of fuel consumption;
  • 80% reduction of NOx emissions;
  • 50% reduction of external noise; and
  • a green product life cycle: design, manufacturing, maintenance and disposal/recycling.

The Clean Sky JTI is based around six integrated technology demonstrators (ITDs):

  • SMART Fixed Wing Aircraft will deliver active wing technologies and new aircraft configuration for breakthrough, new products;
  • Green Regional Aircraft will deliver low-weight aircraft using smart structures, as well as low external noise configurations and the integration of technology developed in other ITDs, such as engines, energy management and new system architectures;
  • Green Rotorcraft will deliver innovative rotor blades and engine installation for noise reduction, lower airframe drag, integration of diesel engine technology and advanced electrical systems for elimination of noxious hydraulic fluids and fuel consumption reduction;
  • Sustainable and Green Engines will design and build five engine demonstrators to integrate technologies for low noise and lightweight low pressure systems, high efficiency, low NOx and low weight cores and novel configurations such as open rotors and intercoolers;
  • Systems for Green Operations will focus on all-electrical aircraft equipment and systems architectures, thermal management, capabilities for 'green' trajectories and mission and improved ground operations to give any aircraft the capability to fully exploit the benefits of a Single European Sky; and
  • Eco-Design will focus on green design and production, withdrawal and recycling of aircraft, by optimal use of raw materials and energies thus improving the environmental impact of the whole products life cycle and accelerating compliance with the REACH directive.

The current members of Clean Sky represent 86 organisations in 16 countries.

VITAL is budgeted at €90.9 million, with half financed by the European Commission. The four-year project started in January 2005. The project partners include Airbus, Avio SpA, GKN Aerospace Services, Rolls Royce, Short Brothers, composites research institute SICOMP of Sweden, and the National Aerospace Laboratory (NLR) of the Netherlands. The programme coordinator is Snecma of France.

Volvo Aero's role in the project includes developing and testing load-carrying structures in aero engines – making engine components as light as possible. 

“There is a actually a direct link between engine weight and the amount of carbon dioxide emissions,” says Anders Sjunnesson, project manager for VITAL at Volvo Aero. “If you increase the engine fan size then you can reduce noise and fuel consumption. But if you build bigger fans the problem is that you increase the weight of the engine, meaning that the engine needs more throttle to take off, which once again increases fuel consumption.”

The challenge is therefore to build bigger fan modules without increasing the engine's weight. One way to do this is to exchange conventional components made of titanium for carbon fibre composites.

“VITAL will develop and manufacture a fan module to conduct a full-scale test in 2008,” says Sjunnesson.

Aviation and the environment

Structural and aerodynamic improvements along with new engine technology have enabled fuel consumption to be more than halved since 1960, with comparable reductions in emissions such as carbon dioxide (CO2) and nitrogen oxides (NOX).

Today, many aircrafts consume just 3 litres of fuel to transport a passenger 100 km and as such are among the most fuel-efficient means of transport in the world.

Improvements in fuel consumption and greater combustion efficiency will contribut to massive reductions in emissions. European Union research programmes aim at further reduction of fuel consumption and CO2 emissions by 50% and NOX reductions of 80% before 2020.

(Source: Volvo Aero.)

“What we're aiming for is that the next generation Boeing 737 and Airbus A320 will have new environmentally friendly engines and be ready for take off in around 2013,” he adds.