Carbon fibers are commonly used in many specialized, high-performance applications such as race cars and aircraft due to their lightweight and high durability. The most important stage in the production of carbon fibers is the carbonization process. During this process, carbon fibers are subjected to high temperatures in the absence of oxygen to prevent fibers from burning. Labyrinth seals are attached to a carbonization furnace to prevent airflow into the furnace and to assist in the elimination of off-gases. This study investigated flow characteristics inside a carbonization furnace and the effects of different geometric parameters of labyrinth seals such as labyrinth tooth shape, number of teeth, and tooth clearance. Varying carbonization furnace operating conditions were also studied in regard to flow behavior, including fiber movement and outlet vacuum pressure. A high working gas flow rate at the furnace inlet resulted in recirculation zones. Properly regulated gas flow from the main and labyrinth inlets enabled uniform flow around the fibers’ inlet and outlet which prevented air from being trapped in the reactor. Flow behavior was minimally effected by changes to labyrinth seal geometry such as tooth length, tooth clearance, and outlet pressure. However, the movement of fibers had a clear effect on flow characteristics in the furnace.

    Abstract
    1 Introduction
    2 Carbonization furnace
    3 Numerical method
    4 Results and discussion
        4.1 Flow behavior inside the carbonization furnace
        4.2 Different sealing chambers
        4.3 Effects of operating conditions on flow characteristics
    5 Conclusions
    References

• Hamada M. Abdelmotalib(Department of Mechanical Power and Energy Engineering, Minia University)
• Dong Guk Ko(Department of Mechanical Design Engineering, Jeonbuk National University)
• Gyo Woo Lee(Department of Mechanical Design Engineering, Jeonbuk National University)
• Ik‑Tae Im(Department of Mechanical Design Engineering, Jeonbuk National University)