Figure 1 – uploaded by Laura Silvestroni

See full PDF downloadDownload figure

Fig. 1. Design of the test articles for material characterization for Hybrid Rocket Propulsion application. — Figure 1 Design of the test articles for material characterization for Hybrid Rocket Propulsion application.

Related Figures (27)

Table 1. Summary of nominal time-averaged test conditions.

Fig. 2. Schematic section of the hybrid rocket and test setup for the different samples.

Table 2. UHTCMC samples for free jet test. Samples TSC-SF-1 and ZBSC-LF-1 were tested in conditions 1, while samples TSC-SF-2, ZBSC-SF-1 and ZBSC-LF-2 were tested in conditions 2FJ. As mentioned before, the first step of the characterization of the new UHTCMC materials consisted in testing small samples exposed to the free jet of the exhaust gases coming from the hybrid rocket nozzle. Details about the different test performed found in [18, 19]. A synthesis of the most significant results, concerning test on the samples summarized in Table 2, is presented in the following. In particu samples had can be ar, two a Ti3SiC2 matrix with short (chopped) carbon fibers, uniformly dispersed into the matrix, and are referred matrix based to as TSC-SF. The other samples had the on ZrB2 as major component and SiC as a minority phase. Two of them had long continuous carbon fibers, with a 0°/90° plies architecture, w others had c matrix. hile the hopped fibers uniformly dispersed into the

Fig. 4 shows the thermal histories of the samples detected by the pyrometer, while Fig. 5 and Fig. 6 respectively show pictures of the samples ZBSC-LF-1 and ZBSC-LF-2 after test, taken by a CCD camera and the optical microscope. It can be observed that, except for the case of the sample ZBSC-LF-1, all other samples experienced a sudden rise in temperature, which at the end of the test exceeded 2800 K. This jump might be associated to triggering, at high temperature, of chemical reactions involving the species contained in the ceramic matrix and/or the carbon fibers, which led to the formation of a porous and poorly-conductive oxidized phase, which for example is relatively small on sample ZBSC-LF-1 (Fig. 5) and is significantly more evident in case of ZBSC-LF-2 (Fig. 6). This oxide layer is characterized by low mechanical resistance and is therefore wiped out causing a significant material erosion.

Fig. 4. Thermal histories of the samples in free jet test

Table 3. Chamber insert samples. The chamber insert manufactured from the C/SiC flat plate has been tested subsequently twice, first in Test condition | and then in Test condition 2, referring to Table 1.

Fig. 6. Pictures of sample ZBSC-LF-2 after the test Fig. 5. Pictures of sample ZBSC-LF- 1 after the test

Fig. 8. Pictures of the CI-LF-1 chamber insert before and after test. On the other side, CI-LF-2 chamber insert was not subjected to structural failure, as it can be seen in Fig. 9, and again no significant erosion has been measured

Fig. 7. Pictures of the C/SiC chamber insert: a) before test; b) after test 1; c) after test 2. were detected, the extreme conditions the material was subjected to determined a delamination of parts of the first layers, as it can be seen from Fig. 7c.

Table 4. VHTCMC nozzle throat inserts. For the experimental characterization of each test article, two subsequent tests have been performed, again with an oxygen mass flow rate equal first to 25 g/s and then to 40 g/s, ie. in test conditions 1 and 2 respectively.

Fig. 9. Pictures of the CI-LF-2 chamber insert before and after test.

Fig. 10. Pictures of the CI-SF-1 chamber insert before and after test.

i a I a I Fig. 12. Microscopic pictures of graphite nozzle throat. Fig. 12, Fig. 13 and Fig. 14 show the microscopic pictures of the zone around the throat section before tests and after both firing tests for the graphite nozzle, the TI-SF and TI-LF, respectively, from which the different growth of the throat section area can be observed. In the latter case, also an increase of the surface roughness can be noticed, probably due to the erosion of the carbon fibers which are less resistant than the ceramic matrix.

Fig. 11. Nozzle throat inserts erosion rates. After the first test in condition 1, it was detected that the throat diameter of the graphite nozzle increased from the nominal value of 9.6 mm to 9.9 mm, while no significant erosion occurred with the two UHTCMC throat inserts. After firing test in conditions 2, further considerable erosion occurred in the case of graphite nozzle, whose throat diameter increased up to around 11.4 mm. In the most severe conditions, also the TI-LF has been subjected to a perceptible erosion, which however was smaller than the former case, with an increase of the throat diameter up to 10.4 mm. On the other side, TI-SF showed a good resistance, with negligible erosion rate also at Test condition 2. The diagram in Fig. 11 graphically represents the corresponding average erosion rates, from which the improved resistance of the UHTCMC materials appears clear.

Ay DUELUIY Wot Us SALLE Wools Fig. 13. Microscopic pictures of TI-SF nozzle throat.

Seekggyer. Rates Saar iaenmnneentorns | Oetawtran ents BELPER TD NUNES Fig. 16. Pictures of the CN-SF- 1 nozzle. Nozzles CN-SF-1 and CN-SF-2 have been both tested in test conditions 2 (see Table 1). As can be observed from Fig. 16 and Fig. 17 which respectively show picture of the two nozzles before and after test, although no significant throat erosion was detected in both cases, the nozzle CN-SF-1 characterized by a very ow porosity was subjected to a structural failure. This failure led to leakage of the combusting gases, determining critical damages also to the engine and the consequential drastic reduction of the engine performance, as it can be observed for example from the pressure profile measured in the combustion chamber during the test shown in Fig. 18.

Figure 1 – uploaded by Laura Silvestroni

Related Figures (27)

Connect with 287M+ leading minds in your field