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# Anticipated but UnwelcomePUBLIC ACCESS

Even as Gas Turbines Get Bigger and Better than Ever, Small Problems Beset New Products—and the Industry.

[+] Author Notes

Lee S. Langston is professor emeritus of mechanical engineering at the University of Connecticut in Storrs and a frequent contributor to Mechanical Engineering.

Mechanical Engineering 140(06), 37-41 (Jun 01, 2018) (6 pages) Paper No: ME-18-JUN2; doi: 10.1115/1.2018-JUN-2

## Abstract

This article provides the latest trends in the gas turbines market and their future outlook. The last three years of operation have generated more profit for the commercial airline industry than the previous 30 years combined. That money has led to new orders for commercial aircraft and as a result, production of commercial aviation gas turbines is in full swing. Engine manufacturers such as Pratt&Whitney, Rolls-Royce, General Electric, Safran, and others have taken this surge in orders as an incentive to develop new technology. The launch of a new jet engine by a manufacturer can be a multi-billion dollar effort. Financial projections and executive careers hang on a smooth roll-out of the new technology.

## Article

The launch of a new jet engine by a manufacturer can be a multi-billion dollar effort. Financial projections and executive careers hang on a smooth roll-out of the new technology.

Engineers know better. It is normal-even expected—that "new engine" problems should crop up when these machines first go into service. I remember that, as a young engineer at Pratt & Whitney in 1970, our team ran into problems with the introduction of the JT9D, the engine that powered the first Boeing 747s.

Today, two innovative jet engines are being launched to power new twin-engined single-aisle, narrow-body commercial aircraft. A lot is riding on these two new planes, the Airbus A320neo and the Boeing 737MAX. Yet, production of these aircraft is currently being delayed, in part, by the "new engine" problems being ironed out in their power plants, Pratt & Whitney's PW1100G geared turbofan engine and by CFM International's LEAP turbofan engine. Both of these new engines are in the 20,000-30,000 pounds thrust range and are demonstrating double-digit fuel savings, as high as 20 percent on longer flights.

To look only at the PW1000G, since that engine entered commercial service in January 2016 on a Lufthansa Airbus A320neo flight, Pratt has had problems that have included engine seals, combustion liners, and fan blade production issues. To be expected by engineers, perhaps, but frustrating to the rest of the company.

Such is the state of the gas turbine industry as a whole. The industry is beset by a myriad of problems that, while not exactly predicted, were at least predictable. The biggest parts of the industry are thriving, however, and even the areas where production is slipping, the problems seem temporary and easily surmountable.

This cutaway illustration of a Rolls-Royce turbofan under development shows the epicyclic fan gearbox that will enable it to perform with great efficiency. Photo: Rolls Royce

According to Aviation Week, the last three years of operation have generated more profit for the commercial airline industry than the previous 30 years combined. That fire hose of money has led to new orders for commercial aircraft-combined, Boeing and Airbus have a 12,000-unit backlog of orders-and as a result, production of commercial aviation gas turbines is in full swing.

Engine manufacturers such as Pratt & Whitney, Rolls-Royce, General Electric, Safran, and others have taken this surge in orders as an incentive to develop new technology.

General Electric, for instance, is in the midst of developing the world’s largest jet engine, the GE9X. Designed to produce just over 100,000 pounds thrust, the GE9X has an inlet fan diameter of 134 inches-a span of rotation equal to the 6 seat-across cabin width of a Boeing 737. The nacelle housing the GE9X exceeds a B737 fuselage width by more than two feet. This behemoth engine will be an attention getter at airport passenger terminals when it begins deployment on the new Boeing 777X 400-passenger jet beginning in 2020.

With a large frontal area, commercial aircraft turbofans are designed to produce peak thrust at takeoff, with most of the thrust produced by air drawn in by the fan and bypassing the jet engine core itself. Bypass ratios-the mass of fan air bypassed for every unit mass of air through the engine core-are currently as high as 9:1 on GE’s GE90, used on Boeing’s current 777s. As the bypass ratio is increased, engine fuel consumption goes down.

The new GE9X is designed to have a bypass ratio of 10:1. That ratio, together with a high aerodynamic loading fan design that features only 16 carbon-fiber fan blades instead of the customary 20 to 30, will enable the GE9X to improve its fuel efficiency over the GE90 by 10 percent.

Another innovative engine is the LEAP, produced by CFM, a joint venture of GE and the French aerospace company Safran. The CFM LEAP engine had its first commercial flights last year, in May on a Malindo Air Boeing 737MAX and in August on a Pegasus Airlines Airbus A3209neo. These high-efficiency engines are widely anticipated by airlines, and the high number of orders have led to production delays.

But as should be anticipated, the LEAP experienced some new engine problems of its own. Cracks were discovered in a batch of low-pressure turbine discs, and recently a borescope inspection on one engine in service revealed the coating on GE’s new innovative ceramic matrix composite high pressure turbine shroud had started flaking off. This is an important durability issue, since the coating protects the CMC from destructive chemical reactions with turbine gases.

The GE9X (see cutaway illustration! will be the world's largest jet engine, with an inlet fan diameter of more than 11 ft. It will power the Boeing 777X. Photos: General Electric and Boeing

The push into the technological frontier does bring rewards. For instance, the P&W epicyclic fan gearbox—the technology that sets the PW1000G apart and upon which the whole effort depends— has proved to be robust and trouble free. Its overall performance has met and exceeded targets for both fuel savings and engine noise reduction. In addition to powering the A320neo, Pratt’s geared fan engines are also powering the Bombardier C Series, the Mitsubishi Regional Jet, and Embraer’s new E-Jets, and the Irkut MC-21.

As an indication of gearbox success, Rolls-Royce is now developing a geared turbofan for its future engines in the 25,000-110,000 lbt range, slated for production in the next decade. This major OEM will then join Pratt & Whitney and Honeywell, who both have been designing, developing, and producing geared fan engines for decades—Honey-well since 1968.

The above gives some highlights of what is going on in the recent aviation gas turbine market, but a broader overview can be gotten by using data from Forecast International, or FI, a market research firm in Newtown, Conn. FI reports on the total gas turbine market, dealing with both aviation (commercial and military) and non-aviation (electrical power, mechanical and marine).

A GE 9HA turbine being readied for testing at a facility in Greenville, S.C. One such turbine makes up part of an 826-MW combined cycle plant that operates with better than 64 percent efficiency.

Photo: General Electric

Using FI’s computer models and extensive database, analyst Stuart Slade has provided the value of gas turbine manufacturing production from 1990 to 2017, and has projected values to 2032. FI considers value of production figures to be more accurate than reported sales figures.

Slade reports that the value of production for all gas turbines worldwide for 2017 was $84.3 billion, up from$77.1 billion in 2016. FI predicts that by 2032, production will reach $100.6 billion, representing a 19 percent growth in 15 years. Based on FI’s value of production history and predictions, the worldwide gas turbine industry is and will be a global growth energy converter industry. For 2017, FI data shows that the value of production of all aviation gas turbines was$71.6 billion or 85 percent of the total gas turbine market. Of this, $63.4 billion was for commercial aviation with the remaining$8.2 billion for military.

Although the military portion is only 11 percent of the total aviation market, it is very significant. Advanced technology developed for military jet engines, such as single crystal blades and film cooling, have historically provided for performance improvements in commercial and also non-aviation gas turbines.

Pratt & Whitney’s 40,000 lbt F135, the engine that powers the F-35 Joint Strike Fighter, is currently the largest military jet engine program. The fighter is currently being deployed in large numbers and now is being purchased by U.S. allies. The U.S. Air Force Adaptive Engine Transition Program is underway to use mature adaptive technology to eventually provide a future replacement for the F135 engine in the mid-2020s.

Another program may torch off the development of new gas turbine technologies. As I and many others have pointed out, the most advanced, most extreme, most superlative-laden military engine ever built was Pratt & Whitney’s J58, which powered the SR-71 Blackbird. This supersonic reconnaissance aircraft, which flew at Mach 3.2 at 100,000 feet, was in service from 1963 to 2001. Recent news reports suggest that a Mach 6 “SR-72” is being developed. Who knows what will be needed to power that hypersonic aircraft?

For 2017, the analysis of FI’s Stuart Slade shows that the non-aviation gas turbine market amounted to $12.64 billion, a 16 percent increase from 2016. Over the next 15 years, FI predicts the value of production for that market will grow by 30 percent, to$16.5 billion.

The 2017 non-aviation portion is subdivided as follows: Electrical power gas turbines amounted to $10.16 billion; mechanical drive gas turbines, used mostly to drive compressors to boost pressure along natural gas lines and for liquefaction natural gas plants, amounted to$1.85 billion; marine gas turbines used to drive generators for propulsion and shipboard electricity, amounted to \$0.63 billion.

The most fuel-efficient systems for electric generation are gas turbines in combined-cycle plants, where gas turbine exhausts are used to produce steam to drive a steam turbine. Such systems are becoming increasingly popular among electric generating utilities and operate under base load conditions in many regions of the country. According to the U.S. Energy Information Administration, natural gas fired combined-cycle units accounted for 53 percent of the 449 GW of total U.S. natural gas-powered-generator capacity in 2016.

To get a sense of how efficient these plants can be, Mitsubishi Hitachi Power Systems recently reported that their M501JAC gas turbine powered combined-cycle 575 MW unit had achieved 64 percent thermal efficiency. GE has also announced that their 9HA.02 gas turbine powered 826 MW combined-cycle unit had exceeded 64 percent thermal efficiency. Siemens has introduced a new H L-class gas turbine, forecasting combined-cycle efficiencies approaching 65 percent. As an academic, I await thermodynamic text book authors to formally document these gas turbine powered combined-cycle plants as the most efficient heat engines yet produced by mankind.

So, given past market trends, favorable predictions, and proven technical performance, one would expect electric power gas turbine OEMs to be gearing up to reap future market rewards.

Instead, 2017 saw continuous reports of gas turbine manufacturers being forced to restructure their power businesses. GE, which two years ago acquired Alstom’s power business (proclaimed by one pundit as the “best deal in a century”), in December announced it would reduce its global power workforce by about 12,000. In November, Siemens reported it would cut 6,900 jobs, given that the power generation industry is experiencing disruption of an unprecedented scope and speed. Mitsubishi Hitachi is also looking at ways to reduce its cost structure to match cuts its competitors are making.

The SR-72, shown in an artist's rendering, is being developed as a reconnaissance plane capable of flying at Mach 6. It would replace the storied SR-71 Blackbird. Image: Lockheed Martin

Some of these trends were foreseeable, and last year in my annual industry recap I listed some trends that were adversely affecting this segment of the gas turbine market. Those factors—such as the great efficiency of combined-cycle plants reducing the need for more gas turbines, the uncertainty of the future of coal power prompting owners of those assets to run them into the ground to produce income while they still can, and the surge of wind and solar power facilities warping the electricity markets such that some gas turbine power plants often operate at a loss—still seem to be in force this year.

The result is that the rosy forecasts for electricity-generating gas turbines, which were underlying the industry only a few years ago, seem to be on hold indefinitely. Within the 15 year forecast window, FI does not foresee the value of production for these gas turbines reaching the level of ten years ago, let alone that of the spike of the early 2000s.

This is the sort of difficulty that could have been anticipated, but wasn’t. Much like the new engine problems that vex jet manufacturers, however, they should be worked out in time. The technology is too good, and the need is too great.

• Bruno, Michael, Mark Nensel, and Jens Flottan, 2018 “Boeing and Airbus Orders/Deliveries Show Continued Market Strength”, Aviation Week & Space Technology, Jan. 29-Feb. 11, pp. 60-62.

• Langston, Lee S., 2011, “Mounting Troubles”, Mechanical Engineering magazine, March, pp. 46-49.

• Langston, Lee S., 2016, “Hot Plates”, Mechanical Engineering magazine, March, pp. 42-47.

• Langston, Lee S., 2013, “Powering Out of Trouble”, Mechanical Engineering magazine, December, pp. 36-42.

• Larson, Aaron, 2018, “Gas Power Generation Thrives, Turbine Manufacturers Struggle”, January, POWER Magazine, p. 6.

• Langston, Lee S., 2017, “Running in Place”, Mechanical Engineering magazine, June, pp. 32-37.

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