Sunday, June 23, 2024

The Jet Engine: Future Perfect

By Bikram Vohra

Bikram Vohra, IA&D Consulting Editor

Most of us do not understand the seriousness of aircraft emissions and are hard-pressed to see the 7000 odd aircraft that bunny hop across 4000 airports in the world every 24 hours causing any great harm. For that reason, years have gone by with very little being done to reduce emissions and protect the environment. Even today we are not seized of the problem as passengers who actually contribute to the destruction from up on high every time we fly.  

Officials say that aircraft engines produce emissions that are similar to other emissions resulting from fossil fuel combustion. However, aircraft emissions are unusual in that a significant proportion is emitted at altitude. These emissions give rise to important environmental concerns regarding their global impact and their effect on local air quality at ground level.

 A comprehensive assessment concerning aviation’s contribution to global atmospheric problems is contained in the Special Report on Aviation and the Global Atmosphere. It was prepared at ICAO’s request by the Intergovernmental Panel on Climate Change (IPCC) in collaboration with the Scientific Assessment Panel to the Montreal Protocol on Substances that Deplete the Ozone Layer and was published in 1999. This told us inter alia: That was a caution issued 23 years ago. 

It was proven that aircraft emit gases and particles which alter the atmospheric concentration of greenhouse gases, trigger the formation of condensation trails and may increase cirrus cloudiness, all of which contribute to climate change. It was also concluded that aircraft are estimated to contribute about 3.5 per cent of the total radiative forcing (a measure of change in climate) by all human activities and that this percentage, which excludes the effects of possible changes in cirrus clouds, was projected to grow.

We may not think that this small percentage is significant but with projections indicating the purchase of another 41,000 aircraft between 2022 and 2041 the cumulative impact on the environment is tangible. Boeing’s commercial outlook is more explicit: For single-aisle airplanes, compared to CMO 2019, forecast deliveries are down just 1% over 10 years and 2% over 20 years, while widebody deliveries are down over 6% over 10 years and 11% over 20 years. Airlines will take delivery of 19,575 airplanes to meet the needs of the market through 2031. Deliveries over the 20 years through 2041 will be 41,170 airplanes. New single-aisle deliveries will make up 75% of total deliveries, with airlines needing more than 30,880 in the next 20 years. Widebody deliveries over the 20-year forecast period will total 7,230 airplanes, 18% of the total. Demand for single aisle airplane deliveries from 2022–2031 will total 14,620 aircraft. 

Therefore, we must conclude that sustainable aviation fuels (SAF) must be the future. And the baton is placed squarely in the hands of the power plant manufacturers. As of now the CFM 56 engine has been the bestseller having covered 1 billion engine flight hours. As these major players take responsibility for making cleaner engines very seriously, some innovations are already on the anvil. Since 1980 CFM has managed to reduce Co2 emissions and fuel consumption. The co-operation between GE and Safran has made major breakthroughs with its Revolutionary Innovations for Sustainable Engines (RISE) programme.

It has also contributed to the European Clean Skies open rotor engine that is even more efficient. The successor to the CFM 56 is the (Leading Edge Aviation Propulsion) a high-bypass engine produced through a joint venture between GE Aviation and French Safran Aircraft Engines (formerly Snecma). GE is also actively developing technology that could ultimately lead to an engine that would use 20% less fuel and produce 20% fewer CO2 emissions than the most efficient jet engines today. The General Electric GE9X is a high-bypass turbofan developed by GE Aviation exclusively for the Boeing 777X. It first ran on the ground in April 2016 and first flew on March 13, 2018; it powered the 777-9’s maiden flight in early 2020.

Meanwhile, Rolls Royce is pretty much on the highway to changing the game dramatically with its efforts to create a hydrogen engine with zero emissions. The RR-easyjet combine is working on this project on a series of engine tests on the ground, starting later this year and have a shared ambition to take the technology into the air. The objective of the partnership is to demonstrate that hydrogen has the potential to power a range of aircraft from the mid-2030s onwards.

While Rolls-Royce will bring its expertise in engine development and combustion systems, easyJet will contribute its operational knowledge and experience to H2ZERO and will also directly invest in the test programme. If that materialises then it might make plans like the GE-Safran proposal deliver dramatically new gas-turbine engine design by the mid-2030s redundant. It is expected to be an open rotor, which dispenses with the conventional pod around the rotating fan blades. This allows a larger fan, sweeping backward a greater volume of air. 

Pratt and Whitney are no slouches either. They are advancing technologies that will help meet the aviation industry’s environmental goals, including the target of reducing overall emissions by 50% by 2050, compared to 2005 levels. They say there are five ways they’re working to ensure cleaner skies are on the horizon. Saving fuel and CO2 with the GTF engines. With more than 960 GTF-powered aircraft delivered, and another 5,000 on order, Pratt & Whitney GTF is a key enabler for airlines to reduce their environmental footprint while still growing their passenger numbers and route networks.

They are actively working on hybrid-electric concepts that would address aircraft from regional turboprops to large commercial aircraft. In partnership with NASA and other public funding bodies, they test this technology in flight. Since 2006, P&  have been testing SAFs and supporting the development of certification standards, through our participation with the American Society for Testing and Materials International and the Commercial Aviation Alternative Fuels Initiative. All current engines are ready to accept the certified maximum blend of 50% with conventional jet fuel.

The manufacturer offers a Carbon Offset Service that makes it simple to offset for emissions based on the engine’s flight hours. It says: We partnered with a recognized worldwide leader in offset programs – South Pole – to support access to clean water, renewable energy and forest conservation projects to compensate for aircraft emissions. Even as we work toward more efficient aircraft technologies and greater SAF usage, carbon offsets remain an important tool for generating positive action on protecting the environment.

And it all begins at home. Sustainable aviation begins with sustainable practices. At Pratt & Whitney, we approach every process and product is dealt with by a sustainability mind-set – especially our own operations. Quote: We have continually reduced our greenhouse gas emissions over many years, and we are committing to a further 10% reduction by 2025 (compared to 2019). We are also targeting the same 10% reduction in water consumption and waste production, as well as 100% implementation of water, waste and energy/greenhouse gas best management practices.

So strong is this desire in the industry to become environment friendly and yet more comprehensive as a travel option that plasma powered engines are seriously being considered viable in a Chinese endeavour to end emissions all together. 

An article in Spectrum can be quoted for its easy to grasp interpretation:

“Jet planes may one day fly without fossil fuels by using plasma jets, new research from scientists in China suggests. A variety of spacecraft, such as NASA’s Dawn space probe, generate plasma from gases such as xenon for propulsion. However, such thrusters exert only tiny propulsive forces, and so can find use only in outer space, in the absence of air friction. Now researchers have created a prototype thruster capable of generating plasma jets with propulsive forces comparable to those from conventional jet engines, using only air and electricity. An air compressor forces high-pressure air at a rate of 30 litres per minute into an ionization chamber in the device, which uses microwaves to convert this airstream into a plasma jet blasted out of a quartz tube. Plasma temperatures could exceed 1,000 °C.”

We demonstrated that, given the same power consumption, its propulsion pressure is comparable to that of conventional airplane jet engines using fossil fuels,” say the Chinese. At this moment it is an extraordinary claim because the heat generated would melt the aircraft regardless of whether it was using carbon fibre, ceramic alloys or other modern composites. The Chinese are confident they will be able to counter this problem. 

Future technology is unpredictable. A generation ago email was a sci-fi concept. The fact that an 8-ounce mobile phone would hold a tonne of audio-visual equipment and multi-functionality was fiction not too long ago. 

So tomorrow, who knows the battle to protect the ozone layer may still be won.

Bikram Vohra is a Consulting Editor at IA&D


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