Figure 1.
(
left) The porous matrix of the OCMC FW12. (
right) Weak matrix concept resulting from the porous matrix, according to Levi et al. [
10].
Figure 1.
(
left) The porous matrix of the OCMC FW12. (
right) Weak matrix concept resulting from the porous matrix, according to Levi et al. [
10].
Figure 2.
The energy dissipating fibre pullout within an FW12 sample.
Figure 2.
The energy dissipating fibre pullout within an FW12 sample.
Figure 3.
Assembly structure for the leak test of various material samples.
Figure 3.
Assembly structure for the leak test of various material samples.
Figure 4.
Test rig for the experimental examination of chemical space propulsion systems with the propellants ethanol (left fluid line) and LOX (right fluid line).
Figure 4.
Test rig for the experimental examination of chemical space propulsion systems with the propellants ethanol (left fluid line) and LOX (right fluid line).
Figure 5.
Hot test of the flame tube carried out with the engine test rig ©Holm Helis.
Figure 5.
Hot test of the flame tube carried out with the engine test rig ©Holm Helis.
Figure 6.
(left) Segmented structure of the production mould and (right) first manufactured prototype with a total mass of around 300 g.
Figure 6.
(left) Segmented structure of the production mould and (right) first manufactured prototype with a total mass of around 300 g.
Figure 7.
Layer structure of the laminate for prototype production with fabric images to illustrate the fibre directions.
Figure 7.
Layer structure of the laminate for prototype production with fabric images to illustrate the fibre directions.
Figure 8.
Detailed views of the manufactured prototype: (a) the edge at the transition from the cylindrical combustion chamber to the mounting flange is inhomogeneous and not sharp, (b) the nozzle neck shows a relatively smooth surface with a nevertheless visible fibre structure.
Figure 8.
Detailed views of the manufactured prototype: (a) the edge at the transition from the cylindrical combustion chamber to the mounting flange is inhomogeneous and not sharp, (b) the nozzle neck shows a relatively smooth surface with a nevertheless visible fibre structure.
Figure 9.
The graphite gasket surrounded by mica (a) is used to seal the flange connection between the combustion chamber and the injector head (b), but shows a highly inhomogeneous distribution of force, which is visible through the red imprints of the indicator foil (c).
Figure 9.
The graphite gasket surrounded by mica (a) is used to seal the flange connection between the combustion chamber and the injector head (b), but shows a highly inhomogeneous distribution of force, which is visible through the red imprints of the indicator foil (c).
Figure 10.
The revised flange connection (a) creates a homogeneous force distribution, which is visible through the closed red ring imprint of the indicator film (b).
Figure 10.
The revised flange connection (a) creates a homogeneous force distribution, which is visible through the closed red ring imprint of the indicator film (b).
Figure 11.
After disassembly, the graphite gasket shows a homogeneous imprint of the fibre structure of the CMC surface.
Figure 11.
After disassembly, the graphite gasket shows a homogeneous imprint of the fibre structure of the CMC surface.
Figure 12.
Revised connection of combustion chamber and injector head with a conical flange connection (left), which clamps the OCMC with a circumferential ring (right).
Figure 12.
Revised connection of combustion chamber and injector head with a conical flange connection (left), which clamps the OCMC with a circumferential ring (right).
Figure 13.
In bending tests determined bending stress in dependence of the deflexion for two samples and two reference square sections each.
Figure 13.
In bending tests determined bending stress in dependence of the deflexion for two samples and two reference square sections each.
Figure 14.
The coated sample of FW12 shows smooth fracture edges of the coating after a bending test, while the fibre pull-out of the base material, which is responsible for the damage tolerance, is preserved.
Figure 14.
The coated sample of FW12 shows smooth fracture edges of the coating after a bending test, while the fibre pull-out of the base material, which is responsible for the damage tolerance, is preserved.
Figure 15.
Pressure curves determined in leak tests, (left) in relation to the reference sample made of copper and (right) in comparison of different layer structures.
Figure 15.
Pressure curves determined in leak tests, (left) in relation to the reference sample made of copper and (right) in comparison of different layer structures.
Figure 16.
Pressure curves determined in leak tests, (left) in relation to the installation direction of the coated specimens and (right) comparing different types of gaskets.
Figure 16.
Pressure curves determined in leak tests, (left) in relation to the installation direction of the coated specimens and (right) comparing different types of gaskets.
Figure 17.
Heating of a sample of FW12 during oblique irradiation with an oxy-acetylene torch.
Figure 17.
Heating of a sample of FW12 during oblique irradiation with an oxy-acetylene torch.
Figure 18.
The material sample (top) shows fibre melting (bottom left) and cracks (bottom right) in the area affected by the burner—the latter result from thermal stresses when the already damaged material cools down again.
Figure 18.
The material sample (top) shows fibre melting (bottom left) and cracks (bottom right) in the area affected by the burner—the latter result from thermal stresses when the already damaged material cools down again.
Figure 19.
(left) glaze foamed on the side facing the flame and (right) apparently undamaged substrate material on the reverse side.
Figure 19.
(left) glaze foamed on the side facing the flame and (right) apparently undamaged substrate material on the reverse side.
Figure 20.
Measured mass flow of Test E.
Figure 20.
Measured mass flow of Test E.
Figure 21.
Comparison photos of the flame tube before the hot tests were carried out (left) and thereafter (right).
Figure 21.
Comparison photos of the flame tube before the hot tests were carried out (left) and thereafter (right).
Figure 22.
(left) combustion chamber and nozzle closed with metal plates and (right) leaks at the nozzle-side flange connection that occurred during the pressure test.
Figure 22.
(left) combustion chamber and nozzle closed with metal plates and (right) leaks at the nozzle-side flange connection that occurred during the pressure test.
Figure 23.
Prototype destroyed as a result of the pressure test with torn-off flange.
Figure 23.
Prototype destroyed as a result of the pressure test with torn-off flange.
Figure 24.
Illustration of the shear stress identified as the cause of failure using a sketch of the flange area (the red cirle highlights the origin of the failure cause).
Figure 24.
Illustration of the shear stress identified as the cause of failure using a sketch of the flange area (the red cirle highlights the origin of the failure cause).
Figure 25.
Defects resulting from manufacturing in the transition area between cylindrical combustion chamber and flange.
Figure 25.
Defects resulting from manufacturing in the transition area between cylindrical combustion chamber and flange.
Figure 26.
(left) sectional view of the steel combustion chamber with graphite lining and (right) its use in a hot test.
Figure 26.
(left) sectional view of the steel combustion chamber with graphite lining and (right) its use in a hot test.
Figure 27.
(left) sectional view of the OCMC combustion chamber with graphite lining and (right) its use in a hot test.
Figure 27.
(left) sectional view of the OCMC combustion chamber with graphite lining and (right) its use in a hot test.
Figure 28.
Damage to the graphite used in the steel combustion chamber during hot tests (left) and crack that occurred in the OCMC shell due to a local overload resulting from damage to the graphite (right).
Figure 28.
Damage to the graphite used in the steel combustion chamber during hot tests (left) and crack that occurred in the OCMC shell due to a local overload resulting from damage to the graphite (right).
Figure 29.
Results of the hot tests of the steel combustion chamber (left) and the OCMC combustion chamber (right) in comparison.
Figure 29.
Results of the hot tests of the steel combustion chamber (left) and the OCMC combustion chamber (right) in comparison.
Figure 30.
Summary of the test data of the steel and OCMC chambers.
Figure 30.
Summary of the test data of the steel and OCMC chambers.
Figure 31.
Comparison of the revised (left) with the clamping ring (right), which has been proven to be inadequate in tests.
Figure 31.
Comparison of the revised (left) with the clamping ring (right), which has been proven to be inadequate in tests.
Figure 32.
Revised engine design for a pure OCMC combustion chamber with nozzle.
Figure 32.
Revised engine design for a pure OCMC combustion chamber with nozzle.
Table 1.
Composition of the investigated OCMC FW12 [
9].
Table 1.
Composition of the investigated OCMC FW12 [
9].
Characteristic | Value |
---|
Matrix | 75% AlO + 25% ZrO (3YSZ) |
Fibres | Nextel™ 610 DF-11 |
Fibre composition | >99% AlO |
Crystalline phase | -AlO |
Filament diameter | 10–µm |
Fibre density | g/cm |
Fibre-Tensile strength | MPa |
Yarn count | tex |
Texture | Satin weave |
Thickness of woven fabric | mm |
Table 2.
Material properties of the OCMC FW12 (unless specified, all measures under room temperature) [
9].
Table 2.
Material properties of the OCMC FW12 (unless specified, all measures under room temperature) [
9].
Material Property | Value |
---|
Bending strength | 400 MPa |
Tensile strength | 133 MPa |
Interlaminar shear strength | 17 MPa |
Porosity | 25–30% |
Density | 2.5–2.9 g/cm |
Continuous operating temperature | 1500 K |
Melting temperature | 2300 K |
Thermal expansion | 8 × 10/K |
Thermal conductivity | 3.8 W/mK at 300 °C |
| 2.8 W/mK at 600 °C |
| 2.3 W/mK at 900 °C |
| 2.2 W/mK at 1100 °C |
Table 3.
Averaged measurement data recorded during testing of the flame tube.
Table 3.
Averaged measurement data recorded during testing of the flame tube.
Measured Variable | Test A | Test B | Test C | Test D | Test E |
---|
[g/s] | 36 | 33 | 62 | 40 | 70–90 |
[g/s] | 44 | 45 | 83 | 80 | 77 |
/ | 0.82 | 0.73 | 0.75 | 0.5 | 0.91–1.17 |
[s] | 7 | 14 | 26 | 63 | 30 |
Table 4.
Results of the hot tests compared with the design parameters.
Table 4.
Results of the hot tests compared with the design parameters.
Test Results | Steel | OCMC | Design |
---|
Measurements | | | |
Thrust [N] | 394 | 367 | 500 |
[kg/s] | 0.104 | 0.108 | 0.125 |
[kg/s] | 0.117 | 0.121 | 0.125 |
Calculations | | | |
/ | 0.889 | 0.893 | 1 |
Exhaust velocity [m/s] | 1783 | 1.603 | 2.000 |
Specific Impulse [s] | 182 | 163 | 205 |
Estimated with “Rocket Propulsion Analysis” | | | |
Combustion pressure [MPa] | 1.3 | 1.35 | 1.5 |
Combustion temperature [K] | 2350 | 2060 | 2060 |
Table 5.
Measured and calculated engine data in comparison to design specifications.
Table 5.
Measured and calculated engine data in comparison to design specifications.
Test Run | Design | #130 | #135 | #136 |
---|
Measurements | | | | |
Thrust [N] | 520 | 235 | 320 | 424 |
Duration of constant thrust [s] | 20 | 6 | 9 | 17 |
[kg/s] | 0.133 | 0.086 | 0.107 | 0.125 |
[kg/s] | 0.111 | 0.081 | 0.086 | 0.102 |
Calculations | | | | |
/ | 1.20 | 1.06 | 1.26 | 1.23 |
Specific Impulse [s] | 217 | 144 | 169 | 190 |
Estimated with “Rocket Propulsion Analysis” | | | | |
Combustion pressure [MPa] | 1.6 | 1.05 | 1.28 | 1.5 |
Combustion temperature [K] | 2810 | 2497 | 2681 | 2645 |
Characteristic velocity [m/s] | 1615 | 1608 | 1684 | 1679 |