Leeham News and Analysis
There's more to real news than a news release.
Leeham News and Analysis
- Bjorn’s Corner: Air Transport’s route to 2050. Part 25. June 6, 2025
- New RISE powerplant benefits from decades of GE research and development June 5, 2025
- Engine makers emphasizing durability, reliability June 4, 2025
- Boeing CEO: Lessons learned are key to certification of 737-7/10 and 777X June 2, 2025
- Digital twin is a key to JetZero’s hopes for Blended Wing Body entry June 2, 2025
Bjorn’s Corner; Turbofan engine challenges; Part 6
By Bjorn Fehrm
December 08, 2016, ©. Leeham Co: We have now come to the turbine in our trip through a modern turbofan. The turbines make up the rear of the engine, before the propelling nozzle.
The turbines are the workhorses in the engine. They take the energy released by the fuel in the combustion chamber and convert it to shaft hp to drive the fan or compressors.
Figure 1. GasTurb principal representation of a three-shaft turbofan like our reference Rolls-Royce Trent XWB. Source: GasTurb.
The hotter they can operate, the better. They can then generate more hp on a smaller size turbine. The temperature of the gas entering the high pressure compressor is one of the key parameters of a gas turbine. It dictates the power efficiency of the core and how much work it can perform to drive the fan and the compressors. Read more
Bjorn’s Corner: Turbofan engine challenges, Part 5
By Bjorn Fehrm
December 02, 2016, ©. Leeham Co: We will now look at the combustor area in our series on modern turbofan engines. There is a lot of activity in this area, as it sets the level of pollution for the air transportation industry for some important combustion products.
We will also finish off the compressor part of our series by looking at the bleeding of cooling air for the engine and for servicing the aircraft with air conditioning and deicing air.
Figure 1. GasTurb principal representation of a three-shaft turbofan like our reference Rolls-Royce Trent XWB. Source: GasTurb.
The amount of air which is tapped from compressor stages for cooling and other purposes can exceed 20% of the core flow (some of the flow paths are shown in Figure 1). At that level, it has a marked influence on the performance of the engine. Read more
Bjorn’s Corner: Turbofan engine challenges, Part 4
By Bjorn Fehrm
November 18, 2016, ©. Leeham Co: In our series on modern turbofan airliner engines, we will now go deeper into the compressor part. Last week, we covered the fundamentals of compressors. As compressors and turbines use the same principles, we also covered the fundamental working principles of turbines.
We also described that compressors are temperamental parts, which can protest to wrong handling with violent “burps” (burst stalls with the combustion gases going out the front of the engine) or end up in a rotating stall where it simply stops working.
Figure 1. Stylistic cross section of a two shaft turbofan with both axial and radial compressor. Source: GasTurb.
Turbines, on the other hand, are your robust companions. Aerodynamically they just work, albeit more or less efficiently dependent on what one asks them to do (mechanically it can be very different; we recently saw a turbine disintegrate with large consequences on an American Airlines Boeing 767 in Chicago). More on the turbines later.
In the GasTurb cross section of a two shaft turbofan in Figure 1, the engine has both an axial and a radial compressor. We will consider why engine designers combine these two for certain engine types. Read more
Bjorn’s Corner: Turbofan engine challenges, Part 3
By Bjorn Fehrm
November 12, 2016, ©. Leeham Co: In our trip through a modern turbofan airliner engine and its technologies, we looked last week at the engine intake and the fan. We now continue with the compressor parts.
As compressors and turbines use the same principles (but in opposing ways), we will look at these principles this week and how their roles in the engine create their special characteristics.
Figure 1. Stylistic cross section of a three-shaft turbofan with section numbers. Source: GasTurb.
As before, to make things concrete, we use a GasTurb simulation of a Rolls-Royce Trent XWB 84k engine to look at practical data when needed. As before, I have no specific knowledge about the engine and will not use any data outside what is public information.
The GasTurb cross section of a three-shaft turbofan is shown in Figure 1. We will examine the sections between station numbers (22) and (3) and (4) and (5) in the general discussion of compressors and turbines. We will then look at some data for common compressors. Read more
Bjorn’s corner; Turbofan engine challenges; Part 2
By Bjorn Fehrm
November 04, 2016, ©. Leeham Co: We will now start to go through a modern turbofan airliner engine and look at the technologies which are used and what are their technical challenges. We will start today with the engine intake and the fan.
To make things concrete, we will use a GasTurb simulation of a Rolls-Royce Trent XWB 84k engine. This will provide us with realistic example data for the different parts of the engine. I want to stress that all values are assumed as typical for such an engine. I have no specific knowledge of the Trent XWB and will not use any data outside what is public information.
Figure 1. Stilistic cross section of a three-shaft turbofan with section numbers. Source: GasTurb.
The GasTurb cross section of a three-shaft turbofan is shown in Figure 1. We will use the station numbers in the figure to navigate the engine and the data from the simulation to understand modern airline engines and their typical data. Read more
Bjorn’s Corner: The Engine challenge
By Bjorn Fehrm
October 21, 2016, ©. Leeham Co: In our Corners on East bloc aeronautical industries, we could see that the hardest part to master in a new civilian airliner is the engine.
Both new airliners from Russia and China (Irkut MC-21 and COMAC C919) start their lives with Western engines.
Why is this so? What are the challenges that make engines harder to create than aircraft?
LEAP-1C which will be standard engine on COMAC C919. Source: COMAC.
We will spend several Corners on the main reasons that airliner engines are harder to do than aircraft. Read more
Engine industry clamoring for road back
By Bjorn Fehrm
Subscription required.
Introduction
October 13, 2016, ©. Leeham Co: The airline engine industry is like a ticking bomb. Over the years, a business practice of selling the engines under manufacturing cost and planning to recover costs and make a profit on the aftermarket developed. This goes back decades.
The practice was fostered by fierce competition over the engine contracts for aircraft which offered alternative engines. The losses of the engine sales could be made up later by selling spare parts and services at high margins.
Figure 1. Trent 7000 from Rolls-Royce. Source: Rolls-Royce.
These “jam tomorrow” practices have several implications. The engine industry is now confronted with these and wonder how it could put itself in such a bind. How to handle these and what is the way back?
Summary:
- High competition in engine sales forced ultra high discounts for the up-front engine sale.
- Aftermarket schemes was created that should recover profits over spare parts and services.
- But these maintenance practices create all sorts of problems in the used engine market.
- The engine industry now wants to return to more normal business practices. But how do they find the way back?
Airbus, Boeing agree on NMA–for now
One concept of the middle of the market airplane.
Oct. 12, 2016, © Leeham Co.: It’s rare when Airbus and Boeing agree on product strategy, but officials of the two companies seemed in almost perfect alignment in separate interviews by LNC last week.
Barry Eccleston, president of Airbus Americas, and Mike Sinnett, VP of Product Strategy for Boeing, each said there is no consensus yet among customers for the Middle of the Market airplane (MOMA), also known as the New Mid-range Airplane (NMA) at Boeing.
Eccleston was interviewed on the sidelines of the annual Seattle conference organized by the British American Business Council Pacific Northwest. Sinnett was interviewed on the sidelines of the annual Governor’s Conference organized by the Aerospace Futures Alliance, a lobbying group in Washington State.
Bjorn’s Corner: The Chinese aircraft engine industry
By Bjorn Fehrm
October 07, 2016, ©. Leeham Co: In our Corners on East bloc aeronautical industries, we will now look at the Chinese civil aircraft engine industry.
The Chinese engine industry is closely modeled after the Chinese aircraft industry that we looked at last week. It is organized as divisions and later subsidiaries to the major aircraft companies. Contrary to the Chinese aircraft industry, it has had major problems in gaining the necessary know-how to start developing and producing its own designs.
The industry has built Soviet designs on license since the 1950s and only recently managed to present functional own designs, after many failures.