Honeywell preps small t-shaft as ‘game changer’
Honeywell’s small heavy fuel engine (SHFE), in development since 2003, “will change the game for turboshaft engines in the future,” predicted Ron Rich, the company’s director of advanced aerospace technology.
The SHFE is one of two engines directly applicable to helicopters on which Honeywell is working. The other is the HTS900 destined for the Bell ARH (armed reconnaissance helicopter), a planned replacement for the venerable Bell OH-58 Kiowa. Both are featured at the Honeywell booth (No. 2801) on the Orange County Convention Center exhibit floor. The SHFE is the object of a Honeywell/U.S. Army partnership for an engine that will be a power source for a wide variety of Army applications “for many years to come,” according to Rich. The primary design goal is commonality of fuel logistics throughout the service, using what is essentially kerosene, the “heavy fuel” in SHFE. It would be used in ground and air vehicles, from tanks to helicopters, and in stationary and mobile applications. Such wide use of a single fuel will simplify Army storage and transportation while affording maximum operational flexibility to forces in the field.
Other major design goals, which Rich said the program appears capable of reaching, include a 20-percent improvement in fuel burn, a 50-percent better power-to-weight ratio and a 35-percent reduction in operational costs compared with current kerosene-burning power sources.
While the SHFE has obvious civil potential, its first application will be military, probably aboard manned and unmanned rotary-wing and land vehicles, Rich said. The prototype, for which the first run of a complete engine took place last month in Phoenix, is a turboshaft in the 700-shp class. Even though the SHFE program is still in the technology demonstrator phase, some of the technology developed for it has been “off-ramped” to the HTS900 program. The HTS900’s twin centrifugal compressor design has migrated directly from development for the SHFE. “This is quite unusual,” noted Rich. “It’s not often that we are able to transfer technology so quickly.”
The HTS900 turboshaft is currently in full-scale development and expected to become a production engine soon, Rich said. The SFHE has progressed to full engine status, with a compressor, combustor and high-pressure turbine added to the core. Rich predicted that gas turbines based on the SHFE technology could have a wide variety of military uses. He compared the relative pluses and minuses of gas turbine and diesel engines.
“The gas turbine has a better power-to-weight ratio and smaller installed volume. This gives the operator more flexibility in deciding where to mount it on a platform. It’s also simpler and thus more maintainable and reliable. The diesel offers better fuel economy and has a lower initial acquisition cost, though not necessarily a lower cost of ownership,” he said.
The SHFE is now ready for the next set of engineering tests, this time as a full engine after two full core test series and several component runs. The 700-shp engine is roughly equivalent in potential thrust to a 900- to 1,000-pound turbofan, Rich said. “This core could provide the basis for a scalable family of turbofans, but there are no immediate plans to do so.” He added that Honeywell is unlikely to spin off a turbofan in the very light jet class from the SHFE technology, given that it is more difficult to scale down an engine that to scale it up.
Rich also observed that coming up with a design that will meet target goals is only the first part of the job. “It’s got to be producible within a target cost,” he said. “We design to production cost as well as to operational cost.” Production cost, he added, drives the customer’s acquisition cost.
Rich also pointed out that while it’s fine to design a component that meets an operational goal and can be built in small quantities by skilled engineering shop personnel, the component must have repeatability within design tolerances in mass production. “Design for producibility and repeatability has changed the way we design,” he said.
Rich gave as an example the use of ceramics in high temperature areas of a turbine engine. For many years, going back to its days as Garrett and later AlliedSignal, Honeywell’s engine business had been seeking ceramic materials that could tolerate higher temperatures than metals and thereby achieve higher performance. Materials engineers as long as 15 years ago identified certain ceramic/rare earth combinations that would perform as desired, but problems remained in accurately characterizing those materials and then gaining repeatable mass production.
“We’ve finally solved those problems,” Rich said. “There are ceramic components in the turbines of several of our engines now.”
He outlined the steps from an idea to a product. “First you go from theory to proving that it works in the relevant environment. That’s the science. Then it has to be made producible within the target cost. And, you have to make the infrastructure ready. That is, you must have acquired or developed the tools to design and build that item in the future,” he said.