India 3D prints IN718 alloy fuel injectors, and demonstrates the potential for missile terminal applications

December 6, 2021, used by researchers at the Defense Metallurgical Research Laboratory (DMRL) of India3D printingThe technology has created an upgraded version of fuel injectors that can reduce the propulsion costs of surface-to-air missiles.The team adopted PBF 3D printingTechnology, integrating a triangular cross-section into their injector design, which allows the two components that had previously been assembled to be integrated into a single, flow-optimized device. Engineers said that not only does this eliminate the need for expensive electron beam welding (EBW) methods, but it also creates unique, grid-like lightweight components.

△The DMRL teamTopology OptimizationA 3D model of the fuel injector. The picture comes from the National Academy of Engineering of India.

India’s national-level missile development strategy

Since 2009, DMRL’s new manufacturing technology team has been usingOptomec The LENS-750 system uses steel, titanium and various super alloys to print missile prototype parts.In the process, the team’s engineers have discovered that additive technology compares favorably with traditionalaviationaerospaceThe advantages under the production process, especially in terms of design freedom and delivery time.However, after the success of a similar thruster project at the Vikram Sarabhai Space Center in India, the researchers decided to abandon the DED technology and determined to design a fuel injector of their own. The engineers stated that since switching to the PBF process, they have been able to redesign the existing missile components in a way that does not hinder their structural integrity and eliminates the need for supports. The team said in the paper: “Due to the limitations of traditional manufacturing, designers do not have much flexibility to achieve more effective designs and create lighter and stronger parts. They are just forced to design parts specifically for manufacturing. As a solution, 3D printing can manufacture parts according to the designer’s conceptualization, design and modeling.”

△The researcher’s 3D printed optical microstructure image of the missile fuel injector. The picture comes from the National Academy of Engineering of India.

Modified aerospace components

In the PBF experiment of the DMRL team, they chose to redesign a fuel injector component, which is usually used in the reaction control system of missiles or rockets to provide them with a high degree of control. These parts are composed of “injector” and “ring” elements and three large holes for fuel and oxidizer output. They are usually produced by CNC machining and EDM, and then fused by EBW.

According to engineers, most of the device components produced in this way are overweight, which greatly affects performance and efficiency, and must also provide support for their complex internal geometries.
On the other hand, by switching to PBF and adopting the DfAM method, the DMRL researchers were able to produce their jet as a printing element, and its new 66.4° cross-section made it unsupported. In their transformation, the team also managed to upgrade the runners of the parts, remove materials from their low-stress areas, and introduce an ultra-light grid structure at the bottom.

Engineers use IN718 nickel alloy inEOS-M400DMLS machine 3D printed a prototype of a fuel injector within 30 hours, then observed its SEM image and conducted mechanical testing. It was found that the part has a good internal cavity area and proved to be densely constructed without any major pores or cracks to weaken its structural rigidity.

In addition, during the test, the device showed a compressive strength of 500 to 600 MPa, as well as impressive hardness and tensile strength characteristics, which the research team said were superior to those of traditional melted and cast IN718.
Therefore, the researchers concluded that they have successfully demonstrated the feasibility of their 3D printing-based method and the ultimate potential for application to end fuel injectors. However, they also expressed the need for more rig testing of printed components to evaluate the functional efficiency of their parts. Further analysis can help identify better equipment optimization opportunities.

△The U.S. defense agency has been testing missiles for a long time3D printing technology. The picture comes from the U.S. Department of Defense.

Application of 3D printing on rocket launch

With large sizeMetal 3D printingThe capabilities of the aircraft continue to expand, and its aerospace applications are also expanding, and defense agencies around the world have conducted extensive testing of the technology.Just last year, after a study commissioned by DARPA, the research institution ASTRO Americas proposed to establish a hypersonic missile production facility, which may be equipped with3D printer.In a 3D printed missile component project at the U.S. Army Research Laboratory, it has acquired Senvol and its machine learningsoftwares help. Using its proprietary artificial intelligence algorithm, Senvol has signed a contract to develop a flexible certification program that can be applied to any component or additive manufacturing system. Elsewhere, 3D printing has also been used to manufacture thrusters in the wider aerospace field. Agile Space now joins the ranks of long-term customers such as Launcher and Rocket Lab, and plans to use additive technology to develop upgraded propulsion systems.

The researchers’ findings are detailed in their paper, titled “3D Printing of FuelInjector in IN718 Alloy for Missile Applications”, which is co-authored by Saride Ramesh Kumar, V. Srinivas, G. Jagan Reddy, M. Raghavender Rao, and T. Raghu write.

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India 3D prints IN718 alloy fuel injectors, and demonstrates the potential for missile terminal applications

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