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ISABE-2015-20168 A Fully Non-Metallic Gas Turbine Engine Enabled by Additive Manufacturing Joseph E. Grady and Michael C. Halbig NASA Glenn Research Center Cleveland, OH, USA Mrityunjay Singh Ohio Aerospace Institute Cleveland, OH, USA Abstract pressure turbine nozzle segments for a cooled doublet vane. In addition, IGVs In a NASA Aeronautics Research Institute and acoustic liners were tested in (NARI) sponsored program entitled “A simulated engine conditions in test rigs.
Fully Non-Metallic Gas Turbine Engine The test results are reported and discussed Enabled by Additive Manufacturing”, in detail.
evaluation of emerging materials and additive manufacturing technologies was Keywords: Additive manufacturing, carried out. These technologies may polymer matrix composites, ceramic enable fully non-metallic gas turbine matrix composites, turbine engine engines in the future. This paper applications highlights the results of engine system trade studies which were carried out to Introduction estimate reduction in engine emissions During the last decades, advanced and fuel burn enabled due to advanced lightweight and high temperature materials and manufacturing processes. A materials have made tremendous impact number of key engine components were on the aerospace components and systems identified in which advanced materials in terms of weight reduction, high and additive manufacturing processes operating temperature, reduced fuel burn, would provide the most significant and reduced emissions. In particular, benefits to engine operation. In addition, advances in composites materials and feasibility of using additive manufacturing technologies enabled the manufacturing technologies to fabricate first polymer matrix composite (PMC) fan gas turbine engine components from blades and fan containment system in gas polymer and ceramic matrix composite turbine engines in the 1990’s. More recent were demonstrated. A wide variety of advances in ceramics and coatings will prototype components (inlet guide vanes soon enable the first ceramic matrix (IGV), acoustic liners, engine access door) composite (CMC) components in were additively manufactured using high commercial aircraft engines in 2016.
temperature polymer materials. Ceramic Recent high TRL demonstration of CMC matrix composite components included exhaust nozzle components will lead to first stage nozzle segments and high introduction of CMC exhaust nozzles in turbine engine components. The technical commercial engines in the near future [1]. work was carried out by multidisciplinary, multi ‐ organization NASA-industry team In-spite of many successes and upcoming that included experts in engine design and plans for the introduction of PMCs and analysis, and system analysis, additive CMCs in gas turbine engines, the manufacturing, polymers and PMCs, percentage of advanced composites in structural engineering, ceramic materials these engines is relatively small, on the and CMCs, and sub-component testing order of 10 ‐ 20% compared to nearly 50% under simulated engine conditions.
for airframe structures, with most of it consisting of metallic components.
System Analysis Studies Advanced composite materials have created new opportunities for innovative The systems analysis efforts were focused component designs and opportunities for on evaluating the potential fuel burn, new gas turbine designs/architectures that landing-takeoff (LTO) NO and acoustic X can take full advantage of their unique benefits of polymer matrix and ceramic properties. Recent advances in ceramic matrix composite materials in a regional matrix composite materials and jet class engine. The first step in the technologies could enable the replacement process was the development of the of a wide variety of metallic components current technology, small thrust (i.e., in the hot sections of current gas turbine regional jet class) engine to serve as the engines, leading to reduction of engine baseline. Details of the analysis approach weight and the need for cooling air, and [2-4] and results from these studies are therefore increasing engine efficiency and given in a recent report [5]. The baseline reducing emissions and fuel burn. engine and airplane data used for the However, comprehensive engine design system analysis of engine (CF34-8C5 studies has to be conducted to develop “like”) and the airframe (CRJ900LR design and architecture concepts for a “like”). The analysis effort commenced fully non ‐ metallic gas turbine engine that with the generation of initial performance can be enabled by effective use of PMC and weight benefits from inserting polymer matrix composites (PMC) and and CMC materials and integration of ceramic matrix composites (CMC) into components through additive manufacturing of complex components. the baseline engine.
In this paper, system analysis studies were PMCs were envisioned for use in several locations in the front portion of the engine conducted to assess the benefits of a fully (inlet acoustic duct, fan stator, and the first non ‐ metallic gas turbine engine in terms 4 rows of high-pressure compressor of fuel burn, emissions, reduction of part count, and cost. In addition, technical vanes). In the engine’s hot section, 2600 activities were carried out to assess the °F CMCs were substituted in the combustor liner, high-pressure turbine feasibility of additive manufacturing (HPT) vanes/blades, low-pressure turbine technologies for fabricating complex (LPT) vanes/blades and core nozzle. The polymer matrix composite (PMC) and ceramic matrix composite (CMC) gas cycle was re-optimized to eliminate all turbine blade/vane cooling. The reduction based and had no impact on the “advanced” cycle produced ~2.6% engine performance. As such, the vast improvement in specific fuel majority (~90%) of the fuel burn consumption. The inclusion of the improvement is attributed to the hot composite materials enabled the engine section CMCs [5].
weight to decrease by ~14.5%.
Table 1: Effect of key materials Figure 1 shows the analysis of regional jet technologies on various system level fuel burn sensitivities indicating influence benefits.
of engine weight reduction on the reduction in fuel burn. The combination of fuel efficiency improvement and engine weight reduction would indicate an airplane that has a 4.9% reduction in total fuel burn versus the current technology baseline.
Additive Manufacturing and Testing of PMC Components In this project, several target components for the PMC manufacturing efforts were identified based on the operational Figure 1: Regional jet fuel burn requirements, material properties, sensitivities showing reduction in fuel manufacturing capability of commercially burn and engine weights.
available and developmental polymer composites. Figure 2 shows few of the The second part of the assessment was to high-payoff engine components identified allocate the projected 4.9% fuel burn for advanced materials and manufacturing benefit between the PMCs and CMCs.
technologies Polymer based components Table 1 shows the influence of different included inlet guide vanes (IGVs) and materials and components on the system acoustic liners. The inlet guide vane (IGV) level benefits. In addition to the weight is a static structural component currently reduction versus the metallic parts made of Ti-6Al-4V alloy. This component replaced, CMC usage enabled the is subjected to low pressures and elimination of all turbine blade and vane temperatures suitable for the polymer cooling. By removing the need for cooling matrix composite material systems and the associated mixing losses, an assessed in this program. There has been efficiency improvement in the HPT (1.5 industrial experience with manufacturing pts) and LPT (0.5 pt.) was assumed. The and testing a PEEK thermoplastic IGV.
PMC benefits were entirely weight The polymer composite IGV components are expected to provide benefits from effective weight reduction, superior strength and temperature capability as well as advanced manufacturing processes of this program.
Figure 3: Inlet Guide Vanes (IGVs) and Acoustic liner fabricated using Fused Deposition Modeling (FDM).
Inlet Guide Vane (IGV) Cascade Testing A set of additively manufactured inlet guide vanes were tested in the Engine Research Building (ERB) SW-2 wind tunnel facility at NASA Glenn Research Center. The details of testing facility and set up (Figure 4) has been described in another publication [5]. This facility uses Figure 2: High-payoff engine the lab-wide central exhaust system to components identified for advanced draw atmospheric air through an acrylic materials and manufacturing wind tunnel. The four different inlet guide technologies.
vane designs were tested. Two vanes were made of ABS and two were made of Fused Deposition Modeling approach, Ultem 1000 with 10% chopped carbon used to fabricate polymer matrix fiber. Additionally two fillet designs at the composite components, has been hub and tip of each vane were employed described in detail in other reports [5-6].
in this test. One set of vanes (ABS and Different types of materials were used carbon fiber Ultem) was fabricated with including commercially available the standard Honeywell fillets, while polyetherimides– Ultem 9085 and another set of vanes (ABS and Carbon experimental Ultem 1000 mixed with 10% fiber Ultem) was fabricated with a larger chopped carbon fiber. The testing details reinforced fillet at the tip and hub. The of inlet guide vanes fabricated using ABS vanes were roughly 6 in long, with an and carbon fiber reinforced Ultem 1000 airfoil section 4.5 in long. Each vane was and acoustic liners fabricated from Ultem later painted with a speckled pattern to 9085. Figure 3 shows a number of allow for imaging by the ARAMIS Digital components fabricated using the FDM image correlation) DIC system.
process.
Tests were performed at various inlet velocities ranging from nominally 100 to 600 ft/sec and at angles from 0 to 60 degrees. Additionally the vane cascade was tested in a “closed” position i.e. vanes were set to 90 degrees to the inlet flow in ceramic matrix composite materials.
an attempt to fracture the vanes. Effect of powder size and powder Deflection up to several millimeters was spreading on the layer build up and the observed but no fracture was detected, print quality was evaluated. The powder even at the “closed” condition. As bed was filled with SiC powders or expected, for all vanes the displacement powder + fiber mix to manufacture CMCs.
increases with increasing incidence angle. The SiC powders of different sizes were Also, the largest displacement generally obtained from Washington Mills, MA and occurs on the ABS vane with the baseline utilized to fill the powder bed. Fiber fillet design. The vane maximum additions, ranging from 25-75 vol. %, displacement data for nominal velocities were added to the powder bed powder mix o o o from 100 to 600 ft/sec and 20 , 30 , 40 to manufacture fiber reinforced composite o and 50 angles were measured. Generally materials. The fiber reinforcement was the ABS vanes (4 and 5) show higher Si-TUFF SiC fiber (Advanced Composite deflection than the carbon reinforced Materials, LLC). The manufacturer Ultem 1000 vanes (6 and 7). In addition, reports fiber dimensions of 7 micron mean the reinforced fillet improves the stiffness diameter x 65-70 micron mean length.
of the vane for the ABS but not so much Two types of infiltrants (SMP-10 and for the Ultem. phenolic based) were utilized to densify the printed objects. For microstructural analysis and secondary infiltration studies, various specimens of approximately 12.7 mm wide x 25.4 mm long x 4.0 mm thick size were printed. For mechanical properties characterization, approximately 50.8 mm x 50.8 mm x 4.0 mm size plates were printed, and specimens were Figure 4: Inlet Guide Vane Cascade machined for mechanical testing. Optical Test Section and scanning electron microscopy (SEM) studies were carried out for It is important to note however, that these microstructural evaluation.
tests were conducted with a very limited Microstructural analysis of polished number of trials and test specimens and cross-sections of samples was conducted more samples should be tested to confirm using optical and scanning electron this result. The main objective was to microscopes. In the following sections, determine if the vanes could withstand air micrographs from selected samples are speeds that may be typical of an actual presented to illustrate the results obtained IGV. While a fair amount of bending was using different constituents and observed, none of the 4 center test vanes infiltration methods. In order to further (vanes 4-7) fractured during these tests.
densify different types of printed materials, extra infiltration steps were Additive Manufacturing of CMCs conducted on 50.8 mm x 50.8 mm panels Binder jet process using an ExOne M-Flex from several of the materials sets.
print machine was used to fabricate Additional iterations of SMP-10 vacuum infiltration followed by pyrolysis in a furnace were conducted. Each infiltration and pyrolysis step increased the densities by 0.20-0.55 g/cc. Most of the increase in density occurred in the first two (a) infiltrations with less effect from the third infiltration. Flexural strength specimens were machined from these plates.
Mechanical testing of specimens was conducted using 4 point bend tests. Details of the results have been discussed in other publications [7-8].
The polished cross-section of a fiber reinforced sample from Set-O which (b) underwent three extra infiltration steps is shown in Figure 5. This material consists Figure 5: Optical micrographs of fiber of 35 vol. % of 67 wt. % 220 and 33 wt. % reinforced composite materials (Set-O).
Carborex 600 SiC Powder mix and 65 vol.
% Si-Tough SiC fiber. Multiple Figure 7 shows the demonstration of the infiltrations were conducted with SMP-10 additive manufacturing of turbine engine loaded with 17 wt.% 800 nano SiC CMC components (20 vol. % SiC fiber).
particles. The Figure 5 (a) shows views of Two different sizes of turbine vanes were the polished cross-section at the two ends printed to include larger size high pressure and in the middle of the sample. The turbine nozzle segments for a cooled sample does have some relatively larger doublet vane and two smaller first stage pockets of porosity throughout the cross- nozzle segments (Figure 7, top). Two section. However, in the close-up view cooled double vane sections were aligned (Figure 5 (b) it is seen that the infiltrant is to illustrate how the sections are placed to filled in around the constituents and there form a vane ring section (Figure 7, is a good distribution of the SiC fibers.
bottom). While the material processing may need further optimization to improve Flexural strength testing results from two the properties, it is encouraging that such non-reinforced and two fiber reinforced complex and relevant shapes can be made.
panels are provided in Figure 6. Stress versus strain curves are shown for flexure tests of three bend bars from each panel.
The two fiber reinforced CMC panels had higher strengths and strains to failure than the samples from the two non-fiber reinforced panels. The highest strengths were from Set N with 65 vol. % fiber loading which had an average strength of 66 MPa.
(a) Summary and Conclusions System analysis studies indicate that there are potential fuel saving benefits from PMC and CMC engine components for a regional-jet class system. The CMC components were combustor liner, the high-pressure and low-pressure turbine blade/vanes, and the core nozzle. The benefits included a weight reduction in the aforementioned components due to (b) replacing metallic parts with ceramic- Figure 6: Plots of stress versus strain based alternatives, in addition to the for the results of three bend bar tests elimination of requisite turbine cooling.
from each panel for the non-reinforced The PMCs were applied in the inlet materials (a) and the Si-Tuff SiC fiber acoustic liner, the fan stator and the first 4 reinforced materials (b). rows of the high-pressure compressor vanes and the PMC benefits consisted of weight reductions only in each component. The resultant propulsion system generated a 4.9% fuel burn improvement over the baseline and a 7.7% increase in landing-takeoff (LTO NO ) X margin with respect to the CAEP/6 stringency.
In the case of polymer composites, compressor inlet guide vanes, fabricated from ABS and carbon fiber reinforced Ultem 1000, were tested in wind tunnel to measure the deflection and strain. The ABS vanes show higher deflection than the carbon reinforced Ultem 1000 vanes.
Additionally this data seems to show that reinforced fillet improved the stiffness of the vane for the ABS but not so much for the Ultem 1000.
Figure 7: Demonstration of the additive In CMCs, the ability for the binder jet manufacturing of turbine engine CMC method to be used to fabricate relevant components (20 vol. % SiC fiber). Two shapes for turbine engine component smaller first stage nozzle segments in applications was demonstrated. Silicon addition to two high pressure turbine carbide powders of different sizes and nozzle segments for a cooled doublet blends were used in the powder bed to vane (top). Aligned cooled double vane investigate the printability during the sections (bottom).
printing process such as powder spreading Aerospace Sciences Meeting and layer build up and the print quality, including the New Horizons Forum powder packing, porosity, and infiltration. and Aerospace Exposition, 07 - 10 Silicon carbide fibers were added to the January 2013, Grapevine (Dallas/Ft.
powder bed to make ceramic matrix Worth Region), Texas.
composite materials. Microscopy showed that the fibers were well distributed with 2. R.W. Claus, A.L. Evans, J.K. Lytle no preferred orientation on the horizontal and L.D. Nichols, "Numerical plane and fibers in the vertical plane were Propulsion System Simulation," at angles as much as 45°. Secondary Computing Systems in Engineering, infiltration steps were necessary to further Vol. 2, No. 4, pp.357-364, 1991.
densify the material. Flexural testing of specimens showed that fiber reinforced 3. NPSS User Guide Software Release: specimens had higher strengths and strains NPSS_1.6.5 and NPSS Reference to failure than the non-fiber reinforced Sheets Software Release: specimens.
NPSS_1.6.5.
Acknowledgements 4. M.R. Kirby and D.N. Mavris, "The Environmental Design Space," 26th The authors would like to thank Drs. Mike Congress of International Council of Dudley and Koushik Datta from NASA the Aeronautical Sciences (ICAS), Aeronautics Research Institute for their Anchorage, Alaska, Sept 14-19, 2008, continuous support and encouragements.
ICAS 2008-4.7.3.
We would like to thank test facility staff at NASA Glenn Research Center and NASA 5. Joseph E. Grady, William J. Haller, Langley Research Center for their help in Phil Poinsatte, Michael C. Halbig, IGVs and acoustic liner testing. The Sydney L. Schnulo, Mrityunjay Singh, authors would also like to recognize Jeff Don Weir, Natalie Wali, Michael Berton, Scott Jones and Mike Tong from Vinup, Michael G. Jones, Clark the propulsion systems analysis Patterson, Tom Santelle, Jeremy organization at NASA Glenn Research Mehl, “A Fully Non-Metallic Gas Center who provided key technical Turbine Engine Enabled by Additive support during the benefit assessment Manufacturing-Part I: System effort. Technical help from various Analysis, Component Identification, engineers from Honeywell and rp+m Additive Manufacturing, and Testing during this work is also gratefully of Polymer Composites”, NASA acknowledged.
Technical Memorandum NASA/TM- 2015-218748.
References 6. Kathy Chuang, Joseph E. Grady, Steve 1. M.C. Halbig, M.H. Jaskowiak, J.D.
Arnold, Robert Draper, Eugene Shin, Kiser, and D. Zhu, “Evaluation of Clark Patterson, Tom Santelle, Chao Ceramic Matrix Composite Lao, Morgan Rhein, and Jeremy Mehl, Technology for Aircraft Turbine “A Fully Non-Metallic Gas Turbine Engine Applications,” 51st AIAA Engine Enabled by Additive Manufacturing-Part II: Additive Manufacturing and Characterization of Polymer Composites”, NASA Technical Memorandum NASA/TM- 2015-218749.
7. Michael C. Halbig, Joseph E. Grady, Mrityunjay Singh, Jack Ramsey, Clark Patterson, and Tom Santelle, “A Fully Non Metallic Gas Turbine Engine Enabled by Additive Manufacturing-Part III: Additive Manufacturing and Characterization of Ceramic Composites”, NASA Technical Memorandum NASA/TM- 2015- in process.
8. M. Singh, M.C. Halbig, and J.E.
Grady. “Additive manufacturing of Light Weight Ceramic Matrix Composites for Gas Turbine Engine Applications”, Ceramic Science and Engineering Proceedings, Wiley- ACerS (2015) in press.