The Small Turbine Engine Test Cell

Rolls-Royce has a couple new test cells, the result of the determination of such a need in 2007. By 2009, the first had been delivered; both are now on-line and in daily use. The test cells don’t house your standard dynamometers. They’re unusual in...


Rolls-Royce has a couple new test cells, the result of the determination of such a need in 2007. By 2009, the first had been delivered; both are now on-line and in daily use. The test cells don’t house your standard dynamometers. They’re unusual in several respects, all of them good.

The demand for its small (Rolls-Royce M250 core) engines, many used in helicopter applications, was growing, and Rolls-Royce needed additional new dynos (its legacy equipment is still fully functional and is used regularly) to speed testing and throughput.

The company wanted to cover several bases with the new dynos: disaster recovery was one such consideration; being as “green” as possible was another; and of course the functionality of the test cells was paramount: quick turnaround, minimal maintenance, state-of-the-art telemetry and data logging, engine-configuration flexibility, and accessibility were all important.

Modular construction

Taking these into consideration, Rolls-Royce became the first customer for a new dyno system from a Texas company, Atec. That company’s release (in February 2007) said, “This project marks the launch of Atec’s Phoenix Series modular test facilities, a containerized test cell enclosure which can be fully equipped with all engine support systems — load absorption, fuel, air, oil and fire suppression … Atec has developed an innovative dynamometer system using an electric regenerative dynamometer. This dynamometer is a cleaner alternative than traditional systems, and it offers full range power absorption without the need of a gearbox, in most applications.” The system, says Atec, provided “… all the functionality of a traditional engine test cell with the benefits of [modular construction].”

The system was tailored for use in the Rolls-Royce Indianapolis, IN, facility. Being of modular construction, the Rolls-Royce test cell sits on its own platform, the backbone of which is made up of 24-inch I-beams. This offers some insulation from rare possibilities — earthquakes and most imaginable floods — and maintains the module’s independence — should a need arise to reposition it, the entire building can be moved with relative ease. “We have no plans to do that,” says Paul Bushue, manufacturing and test engineer. “But we have the capability if we ever need it. These modules enhance our manufacturing campus by being lean and flexible.”

Eco-friendly

As for being “green,” well, running turbine engines at high loads for sometimes days on end doesn’t seem all that eco-friendly, even though no one disputes the necessity of running these engines for certification, testing, and routine quality assurance. Standard dynamometers use a water or air brake, where the medium absorbs (and wastes) the power generated by the engine. The new Rolls-Royce dynos use a pair of Schorch 500-hp-rated electric motor/generators controlled by a Parker SSD drive system to provide a precisely measurable load, and the electricity generated by the tests is fed back to the power grid, through an arrangement with the local utility. Rolls-Royce estimates it saves about a thousand dollars a month by selling its generated power back to the utility; and as throughput rises, of course the savings will follow.

Test cell operations

Interesting and important as those qualities are, the daily operational function of the cells is the paramount priority. Accuracy, safety, and throughput are the keywords in production-engine testing, and the new Atec dynos deliver.

Using a Rolls-Royce proprietary data collection system (internally called UMACS — universal monitor and control system), much of the test cycling is automated, although the cells are currently manned; repeatability is assured, and data are more robust. Both hydromechanical control and full authority digital engine control (FADEC) system engines are accommodated on either test cell, and the data collection covers the usual operational parameters — engine and gearbox oil temps and pressures, ambient air temp, inlet and exhaust temperatures — and development and engineering parameters, as well. (For example, various vibration points are monitored, through a highly configurable set of additional sensors.)

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