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Feeling The Burn: Inside The Boot Camp For Elite Gas Turbines

August 05, 2019
The state of South Carolina may have practically invented the punishing workout. It is home to The Citadel, the famously tough military academy — and anyone who has seen Stanley Kubrick’s “Full Metal Jacket” will never forget drill instructor Gunnery Sgt. Hartmann inflicting a special kind of purgatory on U.S. Marine Corps recruits at Parris Island. The city of Greenville, which is just a couple hundred miles north of the military installation, is also home to an equally grueling boot camp. But there is a major difference: Greenville’s trainees are not fresh cadets, but a crop of elite power plants.
This summer, the 9HA.02, the world’s largest and most efficient heavy-duty gas turbine will be put through its paces in the toughest power plant proving course on earth: Greenville’s huge off-grid gas turbine validation facility located behind GE Power’s massive turbine factory here. And the drill sergeant is the calm, genial Bert Stuck, who has worked for GE Aviation and Power departments for 37 years. The veteran engineer laughs at the notion that his turbine test stand is a giant torture chamber. “Not quite: Our motto is ‘test and learn’,” he says.

Even so, Stuck and his team of engineers will push the 9HA.02 to its limits before it is deployed in the field, generating power for homes and businesses all over the world. They have got a full program of exercises in store for the turbine, which can generate 571 megawatts, enough to power a city with 650,000 households. “We will explore the turbine’s entire operational envelope — inside and out,” says the veteran engineer. That is jargon for the range of parameters in which the turbine can operate safely and effectively. It’s important to punish the machine in this way because it proves to customers that the turbines — which will one day be the grid’s workhorses — can withstand ultra-stressful conditions that are well beyond what they would encounter in ordinary service.

Engineers will test the turbine’s mettle in all areas. Stuck reels off a list: “Performance, efficiency, operational flexibility, mechanical and aeromechanical durability, gas and liquid fuel capability, its response to grid fluctuations, and so on.”

 width= Above: The largest and most efficient heavy-duty gas turbine in the world, the 9HA.02 will be deployed everywhere from Malaysia to northern Europe — so it's vital that it work at its peak in a wide range of conditions. Top: At the Greenville test stand, engineers will push the 9HA.02 to its limits before it is deployed in the field, generating power for homes and businesses all over the world. Top and above images credit: Brian Erkens of Reel Video and Stills.

For example, engineers will ensure the 9HA.02 delivers top-tier performance and efficiency whatever the location. “We will have units going anywhere from Malaysia to northern Europe,” says Stuck. Engineers have a trick up their sleeves for replicating sweltering hot, and freezing cold days, and it is not turning the thermostat up to maximum, or down to zero. “We play with certain factors such as airflows or fuel splits to make the unit ‘think’ it is operating in different conditions,” says Stuck.

This may sound like random tinkering, but in reality, the testing stand is as far away from a mad professor’s laboratory as you can get. Every step taken during the test has been simulated by a team of turbine and plant controls experts before it is run in the test stand.  “We want to understand how the test unit and facility will perform together,” says Stuck.  “The simulations give us an excellent idea of what is going to happen.”

Although there are rarely big surprises, the testing procedure is still a huge learning experience. There are around 5,000 instruments across the turbine that continually gather data about its operations, performance and efficiency. These sensors ferry about 1 gigabyte of data per second to Greenville’s nerve center, a bank of computers manned by around 75 design engineers that resemble NASA’s mission control. “That’s like streaming a full hour of Netflix in one second,” says Stuck.

Safety is paramount, so the engineers stay alert for any data readings which look unusual. “That’s priority No. 1 — although we have a good chance of catching anything before it breaks,” says Stuck. He explains that a test director can easily return the turbine to a safe operating point before any component failure.

“Then they’ll start reviewing the data,” says Stuck. Engineers will dive into data streams on everything from component temperatures, airflow and cooling rates, air pressure, blade vibrations, fuel economy, efficiency and power output. “The design teams can get an idea of how the unit is functioning in real-time, as well as analyzing data streams post-event,” says Stuck.

Engineers are hunting for any marginal gain in performance or efficiency that might be up for grabs. It might lead to last-minute fine-tuning, even if it is just a tiny tweak to the shroud or aerofoil of a turbine blade for greater durability, or a small adjustment to the geometry of an extraction port to optimize cooling flows. “We make these kinds of hardware modifications in the factory to actual production units for the benefit of the customer,” says Stuck.

Turbines in Greenville train as hard as U.S. marine recruits at Parris Island, whose boot camps usually last 13 weeks. The 9HA.02 will undergo about 200 hours of test time over nearly three months, and those grueling sessions will last between 12 hours and two days.

 width= In the test facility, some 5,000 sensors gather data from across the machine before transmitting it to a mission-control-like nerve center, where dozens of engineers hunt for any marginal gains in performance or efficiency that can be wrought. Image credit: Brian Erkens of Reel Video and Stills.

It is crucial to test the 9HA.02 at varying load conditions and demonstrate the capability to handle a significant number of starts. The world’s gas turbines are increasingly required to operate across a wide range of loads and operating modes such as cyclic (daily starts and stops) and peaking — the hours of high demand — because of the growth of renewables such as wind and solar. For example, utilities might switch off the 9HA.02 during periods of healthy renewable energy generation and low demand and switch it back on when demand picks up and solar or wind generation have slumped. “From no load conditions, it can reach full power in about 10 minutes,” says Stuck.

This kind of special testing simply cannot be done at the customer site. Greenville is like a special indoor soft play area that allows the engineers to push the turbine to its limits risk-free because the site is not connected to the grid. “That means we can replicate oddball conditions without the danger of tripping any grid,” explains Stuck.

Some extreme forces and engineering are involved in creating those oddball conditions. This includes the channeling of ambient air that has been compressed at a 22:1 ratio into the turbine’s combustion chamber at a rate that would blow up a Goodyear Blimp in less than 10 seconds.

GE also built a dedicated liquid natural gas storage facility to supplement fuel flow to the turbines on the test stand and a special rail spur and a turntable to bring them in.

Despite the extraordinary nature of testing, the test stand produces very few external indications that anything special is happening.  Stuck points out the incongruity. “If you were standing just outside the building, you’d have no idea what’s going on inside — but you’ve basically got a full power plant on the stand.”

Stuck is scheduled to give another customer demonstration, but he is keen to reiterate the value of physical turbine tests before he goes. “Testing has paid for itself many times over,” he says. “You can run all the computer simulations you want, but you will always have things that you cannot simulate.”

Stuck would know. He has trained enough HA turbines to make up an entire squad: The 9HA.02 will be the fourth from the extraordinary turbine family to go on the stand at Greenville. “Our customers love the idea that we’re testing the turbines like this before they arrive,” says Stuck. “It gives them a massive level of confidence in our products.” Talk about positive energy.