"Wild Blue Yonder," Feature Article, May 2006

wild blue yonder

After more than 50 years of intense research, designers are still pushing the gas turbine to new heights of performance.

by Lee S. Langston

the first time ASME sponsored a conference featuring gas turbine technical papers, only two papers were submitted. It was understandable. The gas turbine had been invented only five years earlier and, thanks to wartime restrictions, travel to the Mayo Hotel in Tulsa, Okla., was not exactly easy. Even so, the May 1944 event—the 17th National Oil and Gas Power Conference—caught the attention of this magazine, which reported: "Demonstrating the technical interest aroused by the gas turbine, first new prime mover in 50 years, a capacity crowd of approximately 250 attended the first technical session which was devoted to that subject."

At this meeting, R. Tom Sawyer of the American Locomotive Co. became chairman of a newly formed ASME technical committee that eventually became today's International Gas Turbine Institute. R. Tom, whose vision was that the gas turbine would be the locomotive's engine of the future, led fellow ASME members to contribute, promote, and organize gas turbine technical sessions.

As the international gas turbine community grew, the number of papers sponsored increased to the point that a separate meeting was needed. The First Annual Gas Turbine Conference and Exhibit was held in April 1956 in Washington, D.C. This very first all-gas turbine meeting had 25 exhibitors, six technical sessions, a total of 17 papers, and an attendance of 747. The conference fee was $5, or $2 without papers.

R. Tom Sawyer, who passed away some years ago, likely would have been delighted to learn that over 14,000 gas turbine technical papers have been reviewed, presented, and published in proceedings of Turbo Expo since his first event in 1956. The 50th was held last June in Reno, Nev., where a keynote session offered a unique opportunity for conferees to get an up-to-date overall view of the gas turbine industry from the top management of five major gas turbine OEMs. The keynote session had been organized and was chaired by Brian Rowe, a much-respected gas turbine engineer and the retired chief executive officer of GE Aircraft Engines. For the first time ever, Rowe assembled a panel of CEOs and presidents, from GE Transportation, GE Energy, Pratt & Whitney, Siemens Westinghouse, and Rolls-Royce, to discuss gas turbine markets, technology, and the future.

"Destiny is no matter of chance. It is a matter of choice," said Pratt & Whitney's president, Louis Chenevert, quoting William Jennings Bryan during the keynote session. Chenevert then characterized the focused and sustained use of technology over decades of research, design, testing, and development as the choices that destined the gas turbine to become the premier energy conversion device it is today. Chenevert speculated on sales of as many as 3,000 aircraft for the new "air taxi," twin-engine very light jet (VLJ) market, and engendered some technical discussion from other panel members on P&W's geared turbofan engine concept.

Nighttime testing of the F135 Joint Strike Fighter jet engine at Pratt & Whitney's outdoor test facility in Florida. Shock diamonds are visible in the JSF test engine afterburner exhaust.

John Rice, president and CEO of GE Energy, and Randy Zwirn, president and CEO of Siemens Westinghouse Power, both noted that the market for electric power gas turbines is improving as the overcapacity in the North American market is being worked through. Both of them highlighted new machines that each company is bringing to the electric power marketplace.

GE Transportation's David Calhoun declared that new aircraft sales were vigorous, so much so, in fact, that getting raw materials to fill new engine orders is a real problem.

Sir Ralph Robins, retired chairman of Rolls-Royce, gave a retrospective view of jet engine technology and speculated on future technical developments. He also noted that one needs steady nerves for the business of developing a new jet engine, to withstand the impact of negative cash flows for the first 10 to 12 years, then quipped that holding Turbo Expo in a casino was quite appropriate.

But casinos aren't the only forums for speculation. The recent run-up in the cost of jet fuel has endangered American air carriers. Each dollar rise in the cost of jet fuel can raise the fuel bill for the world's airlines by as much as $400 million. And the sustained spike in natural gas prices in North America has cooled some of the interest utilities have had in gas-fired generation of electricity.

Just how severely has the new level of fuel prices affected the gas turbine industry? And if those prices persist, will they depress the market permanently?

Or will their power and efficiency make gas turbines indispensable?

To get a more detailed look at the global gas turbine industry, consider the values of gas turbine manufacturing production between 1990 and 2005, as provided by David Franus of Forecast International in Newtown, Conn. The results are based on proprietary databases and computer models. In 2005, worldwide gas turbine production amounted to a total of $25.6 billion (in 2006 dollars), which is close to a 16-year (1990 through 2005) average of $25.7 billion. About two-thirds of that production was for aviation—jet and turboprop engines for manned aircraft. Although this is down from a peak in 1990, reflecting major airline purchases in the late '80s, it has remained fairly steady, with a small increase starting in 2003.

BOOM AND CRASH

If production for aviation has been cruising along steadily, nonaviation production—gas turbines produced for electric power generation, mechanical drive, land vehicular power, and marine ship power—resembles the Coney Island Cyclone.

The production of nonaviation gas turbines was $3.6 billion in 1990, only 15 percent of total production. With improvement in thermal efficiency, increases in unit size, and the building of record-breaking combined-cycle electric power plants fueled by cheap natural gas, nonaviation production zoomed to a euphoric high of $25.8 billion in 2001.

That total was nearly double the aviation production that year. This "rush to gas" brought about overbuilding, higher natural gas prices (especially in North America), and uncertainty in the financial world concerning electric utility deregulation. As a result, post-2001 nonaviation gas turbine production tumbled to $8.3 billion in 2004. It improved to $8.7 billion in 2005.

The Forecast International information on gas turbine production contains data on production over the past three years in several categories, as well as projected sales out to 2008. According to the data, the value of production of commercial aviation gas turbines exceeds that of military by a factor of more than three. What's more, the current production values and projections show that the market for commercial aviation gas turbines is increasing and by 2008 may exceed those of the late '80s. Indeed, the orders for commercial aircraft in 2005 have been very strong. Although some legacy North American airlines have gone into and out of bankruptcy, other airlines, such as Emirates based in Dubai, are increasing in size. In addition, many new airlines are coming online—among them Kingfisher and Spicejet in India, and Bmibaby in the U.K. Although increased 2005 oil prices are cutting into profits (or increasing losses), orders for new airplanes are strong, including orders from air cargo carriers and regional airlines.

Orders in 2005 for the new Boeing sub-jumbo 787 ran ahead of those of the Airbus super-jumbo A380, with Boeing at 230 orders and Airbus at 20 (as of December). The latter is undergoing flight testing now, while the former is still in the final design stage. The two also reflect very different sensibilities about the future of air travel. The Boeing 787, a 296-passenger twin jet with either General Electric GEnx or Rolls-Royce Trent 1800 engines, is intended for the long haul, point-to-point air traveler. The A380 Airbus 555-passenger, four-engine jet (using the GP7200 of the GE-P&W alliance or the Rolls-Royce Trent 900) is specifically designed for the consolidated long haul passenger traffic of the hub and spoke system. Time and the marketplace will determine which company has the winning view and the winning engine.

For nonaviation applications, gas turbines powering electric generators represent the largest segment (80 percent of the nonaviation area in 2005), with those used as mechanical drives a distant second, and marine power third with a 5 percent sliver. Mechanical drive units are typically used for natural gas pipeline compressor stations and increasingly, in LNG trains—equipment used to liquefy natural gas. Marine gas turbines, many of which are aeroderivatives (modified jet engines), are used for electric power and propulsion on navy ships and, more recently, on cruise ships.

Forecast International projections show a doubling of electric power gas turbines between 2005 and 2008. The company's analysis predicts an increase in sales to Asia, especially to China, in the near term followed by a turnaround of the North American market in a few years.

Other analysts predict that volatile natural gas prices may dampen the future market for electric power gas turbines. But wide swings in natural gas prices ought to become a thing of the past once the volume of LNG transported by ship becomes larger. LNG, like oil, would then become a fungible commodity with its price set on the global market. The advantages of clean-burning gas turbine plants—thermal efficiencies approaching 60 percent using a fossil fuel with the smallest carbon content—are unbeatable, compared to other combustion prime movers.

Also, one must remember that the proven reserves of natural gas far exceed those of oil, on an energy equivalent basis. Some proponents of the hydrogen economy call natural gas a "transition fuel," predicting that hydrogen gas will be the fuel of the future. But as long as natural gas is plentiful and becomes fungible through a system of worldwide LNG transport, it will be a major energy source for producing electrical power.

POWER PLAYS

In spite of today's high gas prices, there are great strides being made in gas turbines for the electric market. General Electric's first 9H gas turbine combined-cycle plant went into service at Baglan Bay, Wales, in 2003. It is the world's largest gas turbine with a combined-cycle output rating of 520 megawatts and a record-breaking thermal efficiency of just under 60 percent. GE has two 7H units in Romoland, Calif., scheduled to go on line in 2008. In 2005, Siemens announced it is developing an H-type gas turbine with an output of 340 MW and a combined-cycle output of more than 530 MW, with a promised thermal efficiency over 60 percent. For every gain of two percentage points in efficiency, Siemens calculates a savings of $34 million in fuel costs over the life of the 530 MW plant. The first unit will be installed at Irsching in Bavaria, and will have all air cooling, as opposed to steam cooling used by the GE H machines. These huge combined-cycle plants, incorporating both gas and steam turbines, are the efficiency superstars of the electric power plant world.

Natural gas isn't the only fuel available, however. Integrated gasification combined-cycle power plants convert coal into syngas, a low calorific value gas composed of carbon monoxide and hydrogen. The syngas is then burned in a gas turbine, whose exhaust provides heat to generate steam to run a steam turbine. The first standardized commercial IGCC plant is being designed by GE Energy and Bechtel for American Electric Power, the U.S.'s largest electrical generator. This milestone plant, with an output of 629 MW, will start up in Meigs County, Ohio, in 2010. GE Energy claims the IGCC plant will generate less sulfur dioxide, nitrogen oxide, mercury, and particulate matter emissions than an equivalent steam-powered, pulverized coal plant.

The U.S. Department of Energy announced last year the award of $130 million for 10 new projects to integrate hydrogen-burning gas turbines and turbine subsystems into IGCC central power stations. These awards are part of the Department of Energy's FutureGen initiative, a program to build the world's first integrated sequestration and hydrogen production power plant—in essence, a zero-emissions fossil fuel plant—using gas turbines.

Nuclear generation is also a zero-emissions technology, and Pebble Bed Modular Reactor Ltd., a South African company, is developing a gas turbine-nuclear reactor electric power plant, with participating companies that include Westinghouse, MHI of Japan, Nukem of Germany, and South Africa's Eskom. The plant, with a design output of 165 MW, has a closed-cycle gas turbine in which helium gas, the working fluid, is heated in a nuclear reactor composed of some 400,000 nuclear fuel-filled graphite spheres. Each sphere, or "pebble," is about the size of a rather heavy tennis ball. Plant operators can follow the electrical load variation by varying the amount of helium contained in the closed cycle system. Construction of the first demonstration plant, consisting of a four-pack of pebble bed modular reactors (for a total of 660 MW), will be started in 2007 at Koeberg, near Cape Town. If the plant is successful, the South African government will buy additional plants.

Innovation is taking place in the aviation market as well. In December, Pratt & Whitney completed and delivered Flight Test Engine No. 1, the F135 jet engine for the Lockheed Martin F-35 Joint Strike Fighter. That 40,000-pound thrust engine will be installed in the first test JSF aircraft this year.

The Joint Strike Fighter is notable for being designed with missions for three separate service branches in mind. The engine will eventually power the fighter aircraft in all its variants—conventional takeoff for the Air Force, carrier missions for the Navy, and short takeoff/vertical landing for the Marines.

In the STOVL version, the aircraft will be able to hover solely on engine power, using a separate clutched Rolls-Royce-designed lift fan module, and then go into supersonic flight.
It is the most advanced jet engine in the world, with the highest thrust-to-weight ratio and the highest inlet turbine temperatures in the industry. Based on past history, the gas turbine technical community can look to this Joint Strike Fighter program to lead to performance gains in commercial aviation engines and in nonaviation gas turbines.

Who knows? JSF technology might even provide the means to fulfill R. Tom Sawyer's founding vision of a viable gas turbine-powered locomotive.

Lee S. Langston is professor emeritus of mechanical engineering at the University of Connecticut in Storrs and is the editor of ASME's Journal of Engineering for Gas Turbines and Power.