Introduction, 1st Edition
In the gas turbine world, it is essential for all industry sectors to learn from each other. Despite how expensive reinventing the wheel might be, this does not happen enough or sufficiently.
The extent to which it does happen, however, is owed largely to the inception of the aeroderivative gas turbine engine. In part fostered by the offshore industry’s need for a lighter-than-industrial-engine-frame, OEMs (original engine manufacturers) took specific aircraft engines and placed them on a light, strong, and flexible base. Some of industry’s largest fleets are aeroderivative. The land-based Rolls Royce RB211, Trent, and Avon all had mothers who fly (or flew). A General Electric CF6-80C2 eventually “produced” an LM2500 on the ground. In fact the metallurgy of contemporary General Electric Frame 7 and 9 engines is quite similar to that used for the CF6 mature models. The Rolls Royce Olympus and Spey that are used so effectively in marine, offshore, and conventional land-based applications have aero roots.
The logic for the panel that I discussed in the Preface continues. When the General Electric first released their F404 engine triple redundancy architecture was relatively new to industrial users. It is now commonplace in modern power plants.
The concept of a cycle of gas turbine life used versus a calendar hour evolved from realizing that the leader of an aerobatics squadron might only develop 1/20 of the wear on his engines, as compared with the engines of his followers who have to “hunt and follow” a specific distance from his wings. Algorithm development uses the parameters of time, temperature, and speed essentially, to calculate cycles. Unless the engine is among specific models of Rolls Royce that can use just time and speed parameters for the most part. Additional cooling may cost in some ways but pays off in others. Land based users slowly caught on with experimental work on how much a stop and start to a conventional industrial machine (such as an original General Electric Frame 5) versus a much smaller workhorse (such as a Solar Centaur) was worth.
Profit margins are directly affected by how quickly different sectors can learn from each other. The sheer size of GE’s aviation CF680C2 fleet and their land-based LM2500 fleet (the stimulus of GE’s unparalleled financing program notwithstanding) can attest to that. As can the sizes of the Rolls Royce RB211 (land and air fleets). As can the success of the Alstom (once ABB) GT35 both on land and at sea.
Note also that as personnel and technology travel across national boundaries, proprietary technical innovations follow them. The wide chord fan blade is an acknowledged Rolls Royce “first.” It was an enviable one as its performance attributes, both in terms of aerodynamic performance and bird (FOD or foreign object damage) chopping ability, verified. The latter rang the bell at 24 pounds of bird (a vulture over the Indian Air approach in Calcutta). In fairly short order, the wide chord fan blade has appeared on other OEM’s models, albeit with different “internals.”
Gas turbines and their development are plagued with the whims and dips of global finance and politics. Rarely do all sectors have the development money required for their progress at the same time. Military aviation engines may have large budgets at a time when funds in the land-based sector are scarce. In times of peace, certain military engine development programs may be totally suspended. In more recent wars, the priority with military engines may shift from performance to longevity.
The end-user parameter throws the OEM a variable and sometimes exasperating curve. Not all end users are as astute as they’d like to believe. Many of them “shoot from the hip” with unfortunate “brainwaves.” Even when OEMs phase out a model by refusing to service it, some less affluent user generally salvages it, illegally or otherwise. The fact that they might not know the meaning of terms like “not under the stress endurance curve” or “hydrogen embrittlement” does not stop some from midnight raids on the scrap heaps of legitimate shops.
That brings us to the “buyer beware” issue. I have spent a little space discussing cases that books rarely touch, such as the case where 5 JT8Ds were sold to a hapless U.S. courier service by a trusted U.S. ally that claimed the engines had undergone “ESV2” (major overhaul complete status). The engines were missing significant components such as inner air seals on the low-pressure turbine. The diffuser cases (that have to hold significant pressure) had cracks long enough in them that they should have been scrapped. “Zero-timed” overhaul may thus be a function of who’s making that claim.
One way the end user can get leverage with OEMs is by joining an end-user group: a lobby of sorts. This is discussed in some detail in Chapters 14 and 17. In the mechanical drive land-based world, one former group that did this was called the Gas Turbine Users Association. It was the strength of this forum that persuaded a major manufacturer of 3,000 and 1,000 horsepower turbines to back off obliging many end users who had no use for a specific service bulletin to “adopt it or void warranty.” It was similar “users’ strength in numbers” that had Rolls Royce developing cycle use algorithms for the major hot section components in their Spey and Olympus models, which gave the end user a hefty additional lease of life.
In the power generation world, each major model has its own end-user group. Alstom’s (formerly ABB) GT11N group will meet separately from the Alstom GT24 group and so forth. Here the division between end user and OEM can get blurred. Many OEMs now own large shares of power stations. Or they may participate in “BOOT” (build, own, operate, transfer) contracts. Another notable advance is that oil and gas giants are now entering the independent power generation business. Exxon-Mobil, Chevron, and Shell are among those who have moved in a big way on the opportunity to build their own power plants, to whom their refineries and gas fields could then sell their own fuel. I say “in a big way.” When dictated by demographics, oil companies have always made their own power. I cut my power generation teeth at the first Syncrude tarsands project that has always sold excess power back to the public grid.
In military aviation, there are CIP (component improvement meetings). In my military chopper days, I recall a number of CIPs with the U.S. Coastguard most in attendance. In terms of mandate and mission profile, the Canadian helicopter fleets (Army, Navy, and Air Force) most commonly resemble the U.S. Coast Guard for search and rescue and smuggling/drug enforcement patrols. In fact, some of those profiles might sometimes be more demanding than conventional military operations impose.
And so to get maximum benefit for this book, although you might scour the index for mention of “your” model, the more useful stuff you learn may be from applications that run 40,000 feet higher—or lower—than yours. Or a wartime pressed version of “your” aeroengine at sea that had to use heavier fuel than the manufacturer specified. Or a power generation version of your mechanical drive application whose end users happen to have a great deal more budget for financing new repair development or performance analysis system development.
OEM design development that also considers the results from these meetings may include optimized controls and diagnostics (Chapter 9), performance methods (Chapter 10), environmental strategy (Chapter 11), repair and overhaul (Chapter 12), improved testing and installation (Chapter 13), business methods (Chapter 14), and manufacture (Chapter 15). Chapter 19 deals with the design and calculation strategy used by OEMs. The chapter on education also deals with OEM and agency participation in gas turbine educational programs.
Hybrid systems (Chapter 16) are taking on a larger profile for energy conservation and other reasons: combined cycle power generation for instance. Fuel cells and microturbines are proving to have their place, independently and in combination with more conventional machinery.
The book contains detailed discussion of all gas turbine components (Chapters 1 and 2) and elements of a gas turbine system including instrumentation, monitors, filters, and other accessories (Chapters 3 through 8). Specific landmark and case histories on interesting contemporary applications in plants have also been included.