Parker Aerospace is taking its industry-leading fluid atomization technology, including best-in-class fuel nozzles, to the next level through additive manufacturing (AM). Traditional techniques for making fuel nozzles use subtractive machining techniques, which lead to significant materials waste, increased lead time, and increased development costs. Substantial improvements to the aerodynamics of fuel nozzle injectors were not possible because of the limitations and constraints of the subtractive machining techniques. The internal flow passages, which are critical to the performance of the fuel spray, could not be optimized as a result of these constraints.
Current and future aerospace fuel component designs benefit from additive manufacturing in several ways. Better combustion for cleaner-burning engines, greater fuel efficiency, and other benefits are achieved through design optimization and advanced engineering and manufacturing techniques.
Current aerospace development
Parker Aerospace has completed multiple additive manufacturing builds for aerospace applications. For example, inner air swirlers had been designed and are planned for tests on ground engines later this year. Successful weld trials with additive manufacturing components have advanced well beyond prototypes. Parker engineers test the components’ integrity with CT scans, X-rays, vibration testing, and other means.
Some additive manufacturing components have progressed into their second round of design iterations. An inner heat shield for air blast nozzles, for example, is moving through testing and into an advanced development phase.
To support the development of additive manufacturing components, Parker’s Gas Turbine Fuel Systems Division (GTFSD) is dedicating resources and personnel for these advanced manufacturing processes, and ramping up procurement of needed equipment. The work of the GTFSD additive manufacturing team builds on a long history of additive manufacturing that has been underway for years at Parker Hannifin Corporation’s Center of Excellence. The long list of Parker collaborators includes specialists in data management, materials analysis, measurement, and other additive manufacturing skill sets who have previously worked with Parker and its OEM partners in other applications outside of aerospace.
First production of additive manufactured fuel nozzles
Parker’s development for additive manufacturing fuel nozzles in aerospace applications has come far enough that an additive manufacturing nozzle is already going into production for use with non-aerospace power generation. Parker Aerospace has been approved by an OEM customer for a first engine platform to be produced using an additive manufacturing part that will go into field service. This accomplishment is a significant milestone that will build a foundation for the application in aerospace use.
The value of OEM partnerships
Parker has a diverse history of partnerships with OEMs in many industries, including aerospace. These partnerships provided opportunities for faster development times, better performance, and cost reductions to OEM partners. The resulting best practices transfer to current projects.
Additive manufacturing techniques improve the fuel flow paths within nozzles. Improved fuel flow paths enable better fuel film formation and atomization performance for optimizing fuel distribution within engine combustion chambers, improving combustion performance. The new additive manufacturing nozzle design is optimized for fuel flow path, among other improvement features. The fuel flow path cross-sectional area is designed to decrease in the direction of the flow, which leads to an increase in fuel flow speed, a reduction in fuel residence time, and a commensurate reduction in the propensity for coking and clogging of flow paths over time.
Improved aerodynamic and spray performance are accomplished largely through modified swirler vane geometries, better fuel prefilming, and improved spray patternation. Advanced flow field diagnostic techniques, including laser diffraction droplet size measurement and phase Doppler interferometry, have demonstrated superior spray performance of the additive manufacturing air blast injector when compared to a conventionally manufactured injector.
Parker is currently validating the aerodynamics and spray performance of the additive manufacturing injector to establish equivalency and obtain ISO and AS certifications, FAA approvals, and buy-in from aerospace OEMs.
Parker’s evaluation of new additive manufacturing components also includes experimenting with various powders to enhance surface finish, mechanical properties, and geometric accuracy of the components and assemblies. The effects of other, secondary processes, including heat treatment, hipping, etc., are also being studied.
Proper fuel atomization and dispersion are both important to the efficient combustion of fuel. But how much? Parker has found that uniformity of film, or homogeneous thin film that interacts with a high-velocity air stream, leads to optimal atomization of fuel. We have documented a 30- to 40-percent reduction in droplet size under varying conditions (e.g., injector air pressure drops). A 40- to 50-percent emission reduction is anticipated as potential for lean burn engine systems. Parker has filed both design and utility patents for the additive manufacturing designs.
Improving the performance of an OEM’s product is one important goal in all Parker partnerships. But improving the OEM’s operations is another critical objective. In the development of the Inner heat shield mentioned above, what was previously made from three machined pieces is now a single piece, made with additive manufacturing from nickel-based material. A 3D printer uses laser beam fusion to create the single piece, which has a single part number to inventory and track versus three previously.
Additive manufacturing also positively impacts the product development cycle by reducing supply chain requirements and speeding a product’s time to market.
As a component supplier, Parker can also report a reduction in waste of raw materials and a lowering of energy usage with the use of its additive manufacturing techniques.
Outlook for the future
As Parker engineers validate fuel aerodynamics improvements and resulting spray performance to obtain certifications this year, the goal for 2020 is for OEM partners to receive additive manufacturing components for testing in their new aerospace engines. Additive manufacturing of fuel system components should help OEMs dramatically speed time to market in the future.
Parker’s long-range goals for additive manufacturing are to expand its list of aerospace components to include valves, housings, fuel mixers, and more. Additive manufacturing products will meet FAA certification standards and AS quality requirements. Eventually, ISO, SAE, ANSI, and other standards will be met, as well.
And as Parker’s product offerings in additive manufacturing grow, so will risk mitigation efforts and safety audits. Safety goals include identification of required maintenance and additive manufacturing machine health “checkups.” As with other Parker products made for a wide variety of markets, it will be important to define processes, procedures, and best practices needed for maintaining best-in-class status.
At Parker, a customer-focused philosophy extends beyond design—to operations, maintenance, and eventually replacement with even better products.
For more information, visit http://www.parker.com/gasturbine.
This post was contributed by the additive manufacturing team of the Parker Aerospace Gas Turbine Fuel Systems Division.