By Bikram Vohra
As global aviation struggles to get up and walk after the brutal two-year hammering it has received by the COVID pandemic, engine manufacturers continue to research, experiment, and in this effort, try to attain three significant goals.
These reduce engine noise under severe noise abatement laws, become more fuel-efficient, and lower emission levels by using alternative fuels. Some of this is a contradiction, especially since the demand is for more powerful engines and higher thrust, so it becomes a major challenge to balance all these factors. You cannot be more silent or more fuel-efficient or bring emissions to zero at a certain point.
There is pressure on the manufacturers to preserve the environment, and there’s no getting away from that. Before we go any further, let’s see what the industry is doing using power plants. At Rolls Royce, they have officially started to construct the world’s largest aero-engine, and this might well redefine the parameters of sustainable air travel for the next two decades and more. The Ultrafan is currently being put together at the dedicated DemoWorks factory in Derby and should see action by 2030.
This engine will presumably form the basis of a potential new family of engines that will power both narrow-body and wide-body aircraft. The winning point is that they will be able to deliver a 25% fuel efficiency improvement compared to the first generation of Trent engines.
The company says its new offering will help usher transition to Sustainable Aviation Fuel (SAF). The target is to make sure the first test run of the UltraFan will be conducted on 100 percent SAF. Current standards allow aircraft SAF to legally go for a 50/50 mix in their operations, but many airlines do not even cross 1% and stick to petroleum-based aviation fuel.
In an aside, although there has been much discussion and debate about scramjets and their ability to travel at five times the speed of sound, they are not yet anywhere near being a viable option for commercial aviation and will stay in the realm of science fiction as well as aerospace. But not for at least another two decades will the concept of being transported hopefully across the world inside the hour be considered even a possibility. Even then, the fallout from the sonic boom will make commercial air travel with scramjets where the airbreathing jet engine obtains combustion from a supersonic airflow a hazard.
If you recall, the Concorde was also limited in its routes because of its limitations for going supersonic.
Add to that hurdle the high cost of creating materials that can withstand the instant intense heat generated by such combustion, and it might just never happen because it won’t be financially sensible.
Experts are quoted saying, “The critical challenge is the aero-heating, caused by the friction of air rushing over the vehicle’s solid surface at extreme speeds. Aero-heating dominates every aspect of hypersonic vehicle design: materials, vehicle shape, and internal heat management. It’s generally not a significant problem at speeds less than or equal to Mach 2. But at hypersonic speeds, aero-heating can cause hazardous temperatures of up to two to three thousand degrees Fahrenheit. That can melt aluminium and titanium.”
Ergo, totally new materials are called for, and they haven’t yet been confirmed as found.
Rolls Royce wishes to help improve the economics of an industry that currently has to take sustainable fuels as a very valid option and replace traditional jet fuel. Companies are experimenting with the latest composite materials, including light and heat resistance space-age ceramic matrix composites. These CMCs will work in conjunction with various 3D printed parts, thereby giving this range of fifth-generation engines more efficiency and durability.
Another new jet engine that is being experimented with is called LEAP, and it’s being developed by CFM International, a joint venture between GE and Safran Aircraft Engines. LEAP has already been tested and also uses composite materials like the Ultrafan. It speaks volumes for its reliability that CFM has received orders for 12,200 engines, and it may be recalled that it was the proud manufacturer of the highly successful CFM 56.
In June 2021, CFM announced its new RISE (Revolutionary Innovation for Sustainable Engines) programme to produce the next-generation power plant by the mid-2030s. The final goal is to reduce fuel consumption and carbon emissions by more than 20 percent while ensuring that it performs on optimum power while being 100 percent compatible with Sustainable Aviation Fuel (SAF) and hydrogen.
The Pratt & Whitney GTF™ engine is the only geared propulsion system delivering industry-leading sustainability benefits and dependable, world-class operating costs. The manufacturer markets it by saying the GTF engine delivers the most efficient, most sustainable power for the Airbus A320neo family aircraft. To paraphrase: Building upon mature dispatch reliability, the Pratt & Whitney GTF Advantage™ engine for the A320neo family makes the best even better.
It believes that its improved geared version of the turbofan engine will contribute tangibly to building up the A320neo backlog. By 2025 Airbus will be expecting to mount 75 engines every month. The GTF promises a 4% higher thrust, 1% improved fuel burn, and the assurance that it can last longer between scheduled maintenance appointments. Pratt and Whitney are confident that it will be the most powerful engine for the A320 neo family when it enters service in January of 2024.
Do you remember the V2500 engine designed and manufactured by International Aero Engines, a global partnership of aerospace leaders including Pratt & Whitney, Japanese Aero Engine Corporation and MTU Aero Engines? It had commercial, freight and military success in its derivatives and was a top contender for powering the A320ceo. It still has a market presence in the 150 seater segment and has a sustainable maintenance infrastructure backed by 18 established facilities worldwide that provide maintenance, repair and overhaul (MRO) services. This includes nine IAE party company facilities.
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 took to the air on March 13, 2018, while being the engine of choice on the 777-9’s maiden flight in early 2020. It is packaged as the most fuel-efficient engine from the GE stable. It was initially tailor-made for the Boeing 777X and is ten percent more fuel-efficient than the GE90 while emitting fewer NOx emissions than any other GE engine.
Central to all these efforts to get to the next rung is the compatibility with biodiesel alternatives. “Sustainable Aviation Fuel (SAF) is seen as a clean substitute for fossil jet fuels. Rather than being refined from petroleum, SAF is produced from sustainable resources such as waste oils from a biological origin, agri-residues, or non-fossil CO2.” But so far, the exercise is relatively expensive, and carriers stick to petroleum derivatives.
Sci-fi, if you may, has played a role in the earlier days, with cryogenic fuels like liquid hydrogen and boron derivatives being tried out. Superman stuff but none of it was viable. Then there was a frantic search for fuel after the 1973 US fuel crisis and the sharp rise in barrels forcing the government to order a high priority research programme into alternative fuels.
Some work was done at that time on biomass conversion to fuel. But this is the first time it looks as all the big players are taking SAF very seriously and intend to move the envelope to the happier side of the environment.
