A new processing technique combining the freeze gelation process with sacrificial templating is used to create self‐supporting ceramic sound absorption structures for high‐temperature applications. The process leads to near‐net shape components with an open‐pored structure. Expanded perlite, acting as melting filler, increases the porosity up to 74%. The resulting properties of the microstructure such as porosity and airflow resistance are presented. Acoustical measurements in an impedance tube show high sound absorption coefficients up to 0.7. The measured sound absorption is compared with a mathematical simulation. In summary, this process allows the fabrication of temperature‐resistant ceramic sound absorbers.

No abstract

This paper discusses the use of novel porous sound absorbent ceramic tiles as heat shields in combustion chambers with respect to their sound absorption. For this purpose, a theory describing the bulk properties of a homogeneous porous absorber layer was combined with a transfer matrix approach to account for the temperature gradient within the absorber. By means of a high temperature scenario, the maximum absorption performance and the required microscale properties of the absorber are presented.

This paper discusses the use of novel porous sound absorbent ceramic tiles as heat shields in combustion chambers with respect to their sound absorption. For this purpose a theory describing the bulk properties of a homogeneous porous absorber layer was combined with a transfer matrix approach to account for the temperature gradient within the absorber. By means of a high temperature scenario, the maximum absorption performance and the required microscale properties of the absorber are presented.

The autoignition properties of GTL-kerosene sprays have been examined in a hot blow-down wind-tunnel. The results are compared to those of fossil kerosene and the model fuel for GTL-kerosene. A total of more than 1100 experiments were carried out in the pressure range between 4.5 and 6 bar and at temperatures between 740 and 840 K. The sprays were injected in a jet-in-crossflow configuration into hot air of about 30 m/s velocity. It can be shown that the induction times of GTL-kerosene are essentially longer (between 10 and 30%) than those from fossil Jet A1 and its pressure and temperature dependency compares favorably to those of n-decane sprays. This indicates that GTL-kerosene has very good properties if a lean prevaporized premixed combustion with low NOx-emissions is desired. N-decane as the well matching model fuel for GTL-kerosene was found through single droplet ignition experiments performed in microgravity in the Bremen drop tower. These experiments were comparing various mono- and bi-component fuel’s ignition properties to those of GTL-kerosene droplets.