Business Aviation Turbine Technology

 - February 27, 2009, 7:59 AM

Turbofan engine makers active in business aviation– such as General Electric, Honeywell, Pratt & Whitney Canada, Rolls-Royce and Snecma– all have their hands full with research-and-development (R&D) programs, many of which are driven by aircraft programs. However, almost all of the engine companies also run demonstration programs that will not necessarily morph into full engine development. Instead, these demonstrators ensure technologies are ready when an aircraft maker issues a request for proposals. One startup company–Price Induction–seems to have attracted enough interest to plan for a full certification program without any application. Repeated inquiries to Williams International about product development remained unanswered.

General Electric (GE) is developing the HF120 jointly with Honda for the HondaJet and Spectrum S40 Freedom business jets. The engine maker is currently working on the first fully conforming HF120, and plans to begin testing it by mid-year. “The program is on track for certification late this year or early in 2010,” Shawn O’Day, GE’s marketing leader for business and general aviation, told AIN. Entry into service for the HF120–rated at 2,095 pounds of thrust–is expected in 2010. The two partner companies have so far run 10 core and 10 full engines. Testing, teardown and rebuilding of full turbofan engines have been under way at Honda’s Aircraft Engine R&D Center in Japan for more than 18 months. This year, the engine is slated to undergo tests on a flying testbed, as well as on the HondaJet. By service entry, the HF120 is expected to have accumulated some 15,000 hours of ground and flight testing.

HF120 engine production is to begin this year at GE’s Lynn, Mass. facility. Production will then transition to Honda Aero’s new factory in Burlington, N.C., which is slated to open in 2010. The GE Honda Aero Engines joint venture was formed in 2004.

The HF120’s fan is a bladed integrated disk (blisk) and has wide-chord, swept blades. The fan’s final design was the culmination of a competition between GE and Honda teams. The two proposed designs were eventually merged.

A two-stage booster–also composed of blisks–is followed by a single-stage centrifugal compressor. The impeller builds on Honda’s experience in Indy Car turbochargers.
The reverse-flow combustor features advanced materials for its laser-drilled multi-hole cooling arrangement. The single-stage high-pressure turbine has single-crystal blades that will “help reach the 5,000-hour TBO target,” O’Day said. The low-pressure turbine has two stages with two counter-rotating spools.

The noise target is “Stage 4 with margin,” according to the manufacturers. Although the engine’s thrust falls below CAEP 6 compliance limits, GE and Honda still want emissions to remain within extrapolated CAEP 6 numbers. As for fuel burn, O’Day said he wants “better than that of same-class engines.” The HF120 weighs less than 400 pounds and has a bypass ratio of 2.9.

With regard to maintainability, O’Day promises all components in the engine will be accessible, with one-deep line replaceable units (LRUs).

GE also has a core engine demonstration program that could form the basis for a 10,000-pound-thrust engine development. Dubbed eCore, “it is a starting point for business, regional and [single-aisle] commercial jets” covering 10,000 to 20,000 pounds of thrust, O’Day said. GE’s CF34 replacement plan is codenamed NG34 and will use eCore technology.

The eCore builds “to a great degree” on the core design of the GEnx, which is to power the Boeing 787. Thanks to advanced materials (such as ceramic matrix composites) and three-dimensional aerodynamics, the goal is to raise the pressure ratio to 20:1 with a corresponding 16-percent increase in fuel efficiency over the best GE engines currently in operation. A time frame for certification depends on aircraft makers, but O’Day believes 2015 could be possible.

The eCore belongs to a wider company demonstration program called Tech X. “With Tech X, we offer better integration; we look at the aircraft in a more holistic way,” said O’Day, who alluded to improved aircraft-nacelle integration, electric power and a new generation of engine diagnostics and prognosis as hallmarks of the program. The first eCore is to run this year in Evendale, Ohio.

Price Induction–a French startup company with just 22 employees–is now claiming to have raised enough funds to complete the certification program of its 570-pound-thrust DGen 380 turbofan. The core engine is poised to start a second series of ground tests.

“We want to understand the core’s performance better,” deputy manager Romain Cassan told AIN. The first engine test campaign ended in 2007 after accruing 50 hours and 1,200 starts. The company expects to achieve certification of the DGen 380 late next year, and according to Cassan there is also enough money to certify an uprated version, the DGen 390, in 2011.

Price Induction completed a e10 million ($13 million) fund-raising round last summer, adding Financière de Brienne and Aerofund as new shareholders. Despite the lack of a firm application, the program is going forward regardless. However, Cassan said Price Induction is talking to several companies that are interested in building a demonstrator aircraft. With such meager thrust, the platform would likely be in the four- to six-seat category, aircraft that are smaller than in-service very light jets (VLJs).

Price Induction delivered one engine, in September, to the ISAE, a Toulouse-based aerospace engineering school that now uses a DGen 380 for educational purposes. “They keep us informed on their own test results,” Cassan said.

The DGen has one fan, one stage of high-pressure compressor, one stage of high- pressure turbine and one stage of low-pressure turbine. This apparent simplicity disguises innovations such as a geared fan and a shaft-mounted electric generator. The bypass ratio, at 7.6, is high for this class of engine.

Pratt & Whitney Canada (P&WC) is investing C$1.5 billion (US$1.2 billion) in R&D between 2007 and 2011. Selected to power the Cessna Citation Columbus, the PW810 is on schedule to run this summer, Andrew Tanner, v-p for business and regional aviation, told AIN. The engine traces its roots back to a demonstrator called the advanced turbofan integrator (ATFI) in the early 2000s. Under P&WC’s PurePower banner, it is supposed to bring significant benefits in operating economics and be “very green,” according to Tanner.

Certification of the 8,830-pound-thrust engine is pegged for 2011. Its new-generation Talon combustor is expected to emit 35 percent less carbon monoxide and 50 percent fewer nitrous oxides (NOx) than ICAO CAEP 6 standards.

The specific fuel consumption (SFC) will bring a “double-digit improvement.” As for noise, Tanner would not give a number but said it will be “well below Stage 4.” Time on wing will be improved thanks to horizontal–rather than vertical–hot-section inspections, limiting the need for removing the engine and taking it to a workshop.
Another engine in development at P&WC is the 6,100-pound-thrust PW307B, destined to power the Learjet 85, certification of which is expected in late 2011.

“It is similar to the Falcon 7X’s PW307A,” Tanner explained. “We have just tailored the installation and thus modified some software and control systems.”

The 3,200-pound-thrust PW535E, which powers the Embraer Phenom 300, is “almost all done,” according to the engine manufacturer. Certification, however, has been postponed by a few months, to the middle of this year. The PW535E is “similar” to other PW535s, such as the PW535D that powers the Hawker Beechcraft 450XP and the PW535B on the Cessna Citation Encore+.

In terms of VLJ powerplants, P&WC’s PW600 series is now in service, including the PW610F for the Eclipse 500, the PW615F for the Cessna Citation Mustang and the PW617F for the Embraer Phenom 100. Pressed about the overly optimistic forecasts for an onslaught of VLJs, Tanner noted that PW600 production has been “in the ramp-up mode since the beginning,” and the “eight-hour engine,” a reference to a much faster assembly cycle, “is still a target.” The engine comes together well, Tanner said, but “so far we do not really need to go to that rate.”

Arizona-based Honeywell has its HTF7250G “in the middle of full-scale development,” according to Ron Rich, director of advanced technology for Honeywell Aerospace. The engine was selected for the G250, which Gulfstream expects to fly for the first time in the second half of this year. The engine will have “the same reliability and maintenance standards” as the HTF7000, Rich told AIN. Its combustor uses Honeywell’s Sabre technology, which stands for single annular combustor for reduced emissions. The 7,445-pound-thrust engine is to be certified “before the G250 is certified in the second half of 2011,” said Mike Bevans, Honeywell’s manager of technical sales for propulsion engines.

Honeywell has a demonstrator called Tech 7000, the “enabling technologies” of which could apply to various thrust classes, including a 10,000-pound engine. A “quiet high-speed fan” with swept blades has been tested at the component, rig and full engine levels and, according to Rich, engineers have managed to cut noise despite its higher tip speeds.

Of the Tech 7000’s combustor, Rich said Honeywell is developing the second generation of Sabre technology. “We are cutting unburned hydrocarbon and NOx emissions while maintaining good durability,” he said. Rig testing has shown “encouraging results.”

Aerodynamic work on the turbine has yielded improved efficiency. In addition, using advanced materials and coatings is translating into “higher power density.” For example, Honeywell is readying a new material dubbed “alloy 10” for turbine disks. An advanced thermal barrier coating is also being tested.

The Tech 7000 has flown on Honeywell’s Boeing 757 testbed. Environmental targets include halving NOx emissions, along with a “sizable cut” in hydrocarbons, carbon monoxide and particulates, Rich said. Noise is expected to be 20 dB within the current Stage 4 standards.

France-based Snecma continues development of the Silvercrest, although it has so far failed to find an application for its first business jet engine. The Silvercrest’s thrust is in the 9,500- to 12,000-pound range. Program director Laurence Finet told AIN that since the first core engine test campaign concluded early last year, engine parts have been thoroughly examined. “The results confirmed we met our objectives for robustness and dynamic behavior,” she said. Snecma engineers found that the compressor’s surge margin was better than expected.

The core engine ran 80 hours, including 60 hours with combustion on. Takeoff setting was tried, at more than 20,000 rpm. From the time the program receives full engine launch–the green light that follows an aircraft maker’s selecting the engine– Snecma anticipates it will need three years to get the powerplant certified.

Snecma expects to appoint partners in the full program, since the $100 million core engine demonstrator program already involved two such collaborators. Turbomeca (like Snecma, a Safran company) helped design the centrifugal compressor, and Avio helped with the combustor.

Finet emphasized that reducing the number of engine stages has been a major goal. Having a centrifugal compressor helps, since it is equivalent to three axial stages, she said. The compressor has one centrifugal and four axial stages.

Snecma claims fuel burn to be 15 percent lower than that of current engines. Maintenance will be on condition–a giant leap, according to Finet. NOx emissions are expected to be 50 percent better than CAEP 6 standards, while noise is expected to be 20 dB better than Stage 4 limits.

Early last month it was reported that Dassault wants more thrust from the Rolls-Royce RB282 engine that will power the still-under-wraps Falcon SMS super-midsize business jet, suggesting a size or weight increase for the latest rendition of the twinjet. So far Rolls-Royce has discussed 10,000 pounds of thrust.
The British engine manufacturer told AIN in the middle of last month: “We are working closely with Dassault and progressively delivering on program technologies. We are not able to provide engine specification details or discuss their program at this time, as we remain in the joint feasibility phase.”

Power requirements for a business jet encompass more than takeoff thrust. Climb thrust is also important, as is cruise thrust to maintain high speed at altitude. The Falcon SMS will replace the discontinued Falcon 50EX as an entry-level Falcon.
More broadly, RB282 is the internal Rolls-Royce designation for “a range of two-shaft engine studies addressing future corporate jet and single-aisle aircraft markets, available from 2012.” These engines cover a thrust range from 6,000 to 30,000 pounds. The initial RB282 variants will be designed for business aviation.

Design engineering for the RB282 series is led by the manufacturer’s Indianapolis facility, while development and production-proving programs will be conducted by Rolls-Royce’s Bristol site in England.

Rolls-Royce is also developing the BR725 for Gulfstream’s under-development flagship, the G650, and “is making good progress,” a company spokesman told AIN.
Five development engines have undergone operability, performance and endurance testing at various locations, including the company’s Dahlewitz facility in Germany, which is also the headquarters of Rolls-Royce’s corporate and regional airliner engine business. The nacelles and thrust reversers have also been undergoing tests there. Crosswind tests have been performed at Rolls-Royce’s outdoor jet engine testing facility, located at NASA’s John C. Stennis Space Center in Mississippi.

Engine certification and clearance for the first G650 flight are planned for
the second half of this year, while deliveries of the aircraft are scheduled to begin in 2012.

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