Episode Summary:
Rolls Royce has started construction of the world’s largest turbofan engine, called UltraFan. The 140-inch diameter fan of the engine is not only a record, but will help the engine achieve a 25 percent lower fuel burn than existing designs of similar thrust. Reduction gearing keeps blade tip velocities manageable and advanced digital twin technology tracks the history of each blade.
NASA’s Space Shuttle Main Engines were state of the art thirty years ago, and today, they’re the basis for the upgraded power plants that will lift the Space Launch System to the moon. Modern technology at Aerojet Rocketdyne has reduced the manufacturing cost of the engines by 30 percent while increasing power.
Additive manufacturing is making bigger and bigger parts today and SAFRAN has built an entire jet nose landing gear rough casting using an SLM process in titanium powder. The big part is 15 percent lighter than conventional forging and promises to change the way this critical part is made in the future.
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Transcript of this week's show:
Segment 1: British gas turbine manufacturer Rolls-Royce has officially started construction of the world’s largest jet engine, called UltraFan. Assembly is in the company’s DemoWorks facility in Derby, with a demonstrator engine with a fan diameter of 140 inches. The engine is expected to be completed by the end of the year. The big engine is expected to be the basis for a new family of ultra fan turbines designed to power narrowbody and widebody aircraft with 25% better fuel efficiency compared to the company’s familiar Trent engine series. Rolls-Royce believes that higher efficiency will especially be important as airlines are expected to shift to more expensive biofuels in the future. The company’s first test run of the engine will use sustainable fuel. The engine is built with multiple advanced technologies. Each fan blade has been developed with a digital twin which stores test data for the physical blade, allowing engineers to model in-service performance. The company can monitor more than 10,000 parameters, at data rates of up to 200,000 samples per second. Fan blades are carbon titanium, and a comp is it engine casing reduces weight by up to 1500 pounds per aircraft. Ceramic matrix composites are also used in the engine hot section, and the very high bypass ratio design is spun through reduction gearing from the main spool, a technology that is rapidly becoming standard in large diameter turbofans. A 25% fuel efficiency improvement sets a very high bar in an industry where thousands of engineering hours are invested to find one or 2% of additional fuel efficiency. Burning biofuels, it could keep commercial aviation affordable in the post fossil fuel era.
Segment 2: Additive manufacturing has long been a fast and effective prototyping technology, and it’s starting to show up in high visibility applications in critical applications, especially in aerospace. Safran Landing systems and SLM Solutions have produced the additive equivalent of a rough forging of a business jet nose landing gear strut, a tough and safety critical application. The process for the test was selective laser melting, a form of powder bed fusion that uses laser beams to locally melt metal powders to build three-dimensional structures layer by layer. Very large, high aspect ratio parts have traditionally been limited by the working envelope of existing equipment, but for the experiment, run on an SLM 800 machine, a part measuring 80 cm high, by 45 cm deep and 30 cm wide was produced using titanium. Safran has patented the design of the part, which they claim is 15% lighter than a similar forging. It’s an interesting application, since forging alters a metal’s grain structure and improves strength, while additive manufacturing is roughly equivalent to casting in multiple layers. The ability to build parts with complex internal structures give the additive part designer an extra tool to compensate for the absence of strength enhancement from forging. 15% weight reduction in any aerospace part is a major achievement, and landing gear assemblies are some of the heaviest components in jet aircraft, so the future looks bright for large-format additive in aerospace structural components.
Segment 3: Over three decades, NASA launched 135 shuttle missions using Aerojet Rocketdyne RS 25 rocket engines, three mounted on every shuttle. The engines were state-of-the-art when conceived in the 1970s, and proved to be very reliable, and when the shuttle program ended in 2011, 16 of the power plants were left over and placed in storage. With NASA’s new Space Launch System, the RS 25 was a natural choice for the four main engines that power the liquid fuelled first stage. They have proven reliability, mature technologies and of course they are available. In the SLS application, the engines will use upgraded control electronics, and will operate at 109% of rated thrust, slightly higher than their performance in the shuttle application. SLS however is an expendable system and when leftover engines are gone, they’re gone and as a result NASA contracted with Rocketdyne in 2015 to restart RS 25 production using upgraded manufacturing techniques. New build engines use additive manufacturing, advanced inspection procedures and of course machined parts are built with modern CNC equipment. A major design change to the engine nozzle jacket reduced a part count from 37 components to four large metal cones, a change which reduced the cost of the nozzle assembly by 20%. NASA has contracted for 18 additional engines, which will operate at 111% of original thrust levels and are 30% less expensive to build than the baseline shuttle engines. An SLS engine first stage cluster has already been test fired for a full eight minutes, generating 1.6 million pounds of thrust. Nothing this powerful has been seen since the last Saturn 5 was launched carrying Skylab into low earth orbit in 1973. The next step is a test flight of the space launch system to the moon.