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Volvo Aero and Swedish Government Invest $18M in Project for More Fuel-Efficient Aircraft Engines

Volvo Aero and the Swedish Government are each investing SEK 63 million (US$9 million) to support the development of lightweight components for more fuel-efficient aircraft engines. This marks the government authority Vinnova’s first distribution of funding to a commercial demonstrator program in the aerospace industry.

The funding for the Volvo Aero project—“Swedish demonstrator for environmentally compatible aircraft engines”—will be paid in installments from 2007 through 2010.

The reply was highly pleasing, since Sweden has never previously had a commercial demonstrator program in aviation. Aviation faces major challenges to deal with environmentally. We can contribute with lightweight technology so that the aviation industry combined shall achieve the emissions targets agreed by the entire industry in Europe.

—Volvo Aero’s President Olof Person

At the European level, Volvo Aero is participating in the forthcoming “Clean Sky” Joint Technologies Initiatives (JTI) within the EU’s seventh framework program. Volvo Aero is participating within SAGE (Sustainable And Green Engine) element of Clean Sky, in cooperation with Rolls-Royce, Snecma, MTU and others.

The Clean Sky initiative is focused on developing technologies that will deliver:

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

Volvo Aero specializes in advanced components for aircraft engines/gas turbines, with the goal of achieving a leadership position in a select set of key technologies. These include technologies for optimized fabricated structures, production process modeling, high-speed machining and integrated analysis tools for fluid dynamics and stress calculations. More than 80% of all new commercial aircraft with more than 100 passengers are equipped with engine components from Volvo Aero.

Volvo Aero is a program partner for General Electric’s next-generation GEnx engine, which last month began flight-testing on GE’s 747 flying test-bed. Volvo Aero has provided the GEnx with six different components. GEnx is the largest commercial engine program yet for Volvo Aero.




Speaking of GEs flying test-bed...How bout strappin 2 GE90-115s to it and see what happens. 747 twinjet anyone?


50% reduction in CO2 emissions and fuel consumption? Great idea. Why nobody else thought about it?

BTW, 18 million $ is about how much ONE big turbofan costs.

Rafael Seidl

A 50% reduction in CO2 implies there are still huge inefficiencies in current aircraft engine designs, including high bypass turbofans.

The only major optimization route I am aware of is recuperating exhaust heat by pre-heating the compressed air before it reaches the combustion cans/annulus. Presumably, current designs don't do this because there's too little room for the piping that would be required for a gas-gas recuperator. An intermediate liquid cycle with two heat exchangers might be a way to recycle the heat without forcing the hot gas jet to reverse direction twice.

Coke Machine


One thing you do not want to do is preheat air before it gets into the combustor. Turbo (fans and Jets) are muc more efficient at high altitude due to the coldness of the air. Typically when flying my F-111 at high altitude the airplane burned 1/2 the fuel as it did flying low altitude. All of our charts in the F-111-1 Aircraft manual which include Takeoff Rolls, performance etc. Show better performance when cold air enters the engine. Heating that air would reduce, not increase enging efficiency.


They don't mean that the 50% reduction in CO2 will come from alterations to engine design, this is meant to come from the use of carbon fibre, flying wing design approaches etc.

The main contribution of the new engine designs to the programme will be reductions in noise and NOx.

Rafael Seidl

@Coke Machine -

overall thermodynamic efficiency does depend on the temperature of the intake air. However, wasting enthalpy via the exhaust is not a good idea, since only its velocity gain actually generates any thrust.

Recuperating exhaust heat reduces the amount of fuel required raise the temperature of the compressed fresh charge to the peak process temperature. The important thing is to pre-heat the incoming air after it's already been compressed. Of course, recuperation is only possible if the gas temperature after turbine is (significantly) higher than that after the compressor.

The efficiency gain is therefore greatest in designs and/or operating states with moderate pressure ratios over the compressor stage. The downside is that the heat exchanger can eat up as much as 10% of rated thrust due to the flow restriction, which is a problem if the aircraft is heavily laden, the runway is short or the ascent corridor steep.

Source: Saravanmuttoo, Rogers, Choen: Gas Turbine Theory, 5th Ed., Pearson/Prentice-Hall, ISBN 0-13-015847-X

Rafael Seidl

@Coke Machine -

btw, the primary reason jet aircraft fly at high altitude is the low density of the air up there, which is proportional to wind resistance.


RS, I think you are correct for a low altitude one not only runs into wind resistent, one runs into turbulence, bad visibility, and an occational mountain.

I would be surprised in the modern fan-jet engines are able to be improved a whole lot, but the aircraft itself, can be made with lower drag and lighter weight, so that the combined effect of all three could reduce fuel consumption by 50%.



I get the impression that you use Google a lot. Regenerative gas turbines have been around for ages, although for specific applications. Did you realise that automotive applications were of that configuration to try to get decent efficiency. And yes Mercedes did one and you can see an example in the technical museum in Munich. However one should realise that gas turbines which use work from the turbine shaft to propel a vehicle must try to expand the combustion gases completely through the turbine to get reasonable efficiency.

Jet propulsion gas turbines only expand enough gas through the turbine to drive the compressor and the rest is used as jet thrust.

The maximum efficiency of gas turbines is at near full power and therefore there is a trade-off between efficiency at cruising speed, take-off power requirements and emissions.

I think you make the common mistake of mixing up enthalpy and entropy. Ultimately it is the second law of thermodynamics which needs to be considered w.r.t. irreversibilities. If you don't take that into account you will end up trying to make a perpetual motion machine.

Rafael Seidl

Daydreamer -

I quoted my source, a standard textbook on gas turbine fundamentals. What's yours?

Btw, the fact that Chrysler and Rover built and then abandoned gas turbines for cars is entirely irrelevant to this discussion of aviation jet engines.

The notion that recuperating some of the heat would make a gas turbine a perpetual motion machine just underlines your lack of understanding of the fundamentals of thermodynamics, not mine.


M-m-m, Rafael, I believe you missing up the difference between stationary and aero-propulsion gas turbines.

Coke Machine


I spent a lot of time trying to fashion a response that didn't seem to be trying to one up you as that is not my intention. I have 14 years of experience with jet engines, specifically on seven types of jet aircraft. I was a functional check flight test pilot on three of those types. I stand by my original post that trying to heat the air coming into the combustor is a bad idea. The USAF has specific data about the same jet engines in both hotter and colder environments, as well as specific data about engine performance in cold vs hot areas. While there are many factors here, I still think it is a bad idea on aircraft engines to preheat air coming into the combustor. Both from an efficiency perspective and from a mechanical perspective. Your post mentioned reversing the direction twice. This sounds like bleed air to me and any removal of air in this manner reduces the efficiency of the engine by having less thrust come out of the back. Any apparatus to recover the exhaust heat and then preheat the air into the engine would be so large as to render any improvement (which I doubt there is)in performance moot because of the increase in weight and form drag. Andrey has a point where this would not be a problem with stationary jets, but I still doubt they would use the waste heat like that. Additionally this post was about aircraft engines. Most likely the use of a stationary engine like this would use the waste heat as a means of co-gen. Tropicana Products has a jet turbine co-gen facility at their orange juice plant in Bradenton Florida which does exactly that, both using the turbine as a generator and the waste heat in their plant. I also know from personal experience that jet engines flying in hotter areas of the country had higher maintenance problems than jets at cooler areas of the country. BTW, flying at high altitude is not governed by just the one criteria of less dense air you mentioned. There are many factors that go into the decision of where to fly. We typically had many factors to contend with when flight planning about which altitude to select. Temperature, (which effects air density), specific engine performance at altitude and temp (colder was always more efficient, but that may be because colder was denser and may have allowed our fan portion of the engine to produce more thrust than the same at higher temp, wind speed at altitude (no sense trying to fly into a 100kt wind in the jet stream) Weight of the aircraft, aircraft load, etc. All data I have seen on the seven aircraft types I was affiliated with show a marked increase in performance at all altitudes with colder air entering the engine. This can be verified by checking the aircraft performance data in the following publications, (though probably not readily available to non-military personnel); F-111A-1, F-111D-1, F-111F-1, T-37B-1, T-38A-1, AT-38B-1, F-15C-1





What Rafeal was talking about is characteristic of regenerative gas turbine designs. It involves adding heat to the compressed air i.e. the air stream after the compressor and not before as you are describing. You are correct in saying that efficiency is degraded by heating the inlet air ahead of the compressor.

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