The flame tube is the main heated part of the combustion chamber, and its cooling performance has an important influence on the reliability and life of the combustion chamber components.  The main characteristics of the flame tube are: The inner of the flame tube thermal boundary load involves convective heat transfer, heat radiation, swirling motion, chemical reaction near the wall surface, etc.   the outside is the compressor exhaust in the combustion pressure cylinder, mainly with convection, impingement cooling and other non-blending cooling as a means of cooling.  The flame tube and its cooling structure have large size characteristics, and thus have a high characteristic Reynolds number, the Reynolds number of the outer tube of the flame tube can reach 8×10^5^.  In view of the above characteristics, the heat transfer characteristics of the combustion chamber flame tube are very complicated, and the research on the cooling performance of the flame tube is still lacking.

In this paper, the effects of jet Reynolds number, initial cross-flow and outlet pressure on jet impingement cooling  are studied by experimental methods. Transient liquid crystal experiments are carried out to study heat transfer augmentation by jet impingement on smooth target with initial cross-flow. The range of jet Reynolds number is 60000-160000, the velocity ratio of cross-flow and jet velocity is 0\~1.5. The diameter of the jet hole(d) is 7\~12mm, the distance from the jet hole to the target surface to diameter ratio(H/d) is 1.25\~2.5, the distance between the jet holes(x/d) is 2.5\~4.3, the outlet pressure is 0.35\~0.5Mpa. Heat transfer coefficients are measured using a transient Liquid Crystal technique employing a one-dimensional semiinfinite model. Detailed normalized Nusselt number contours have been presented, to identify the regions of high heat transfer augmentation locally, so as to help the designers in the organization of jet structures in an flame tube upon the active heat loads.

The results show that the peak of the Nusselt number is mainly affected by the Reynolds number of the jet, which is less affected by the cross-flow. The Nusselt number peak of the impact target surface is enhanced with the increase of jet Reynolds number. The jet stagnation point corresponding to the Nusselt number peak shifts downstream under the action of the initial cross flow, and the heat transfer effect downstream of the stagnation point is better than that of upstream. When the jet Reynolds number is constant, the average Nusselt number of the target surface has an maximum value as the cross-flow increases. As the ratio of the initial cross-flow to the jet increases, the average Nusselt number of the target surface first increases and then decreases. In the scope of research, the outlet pressure has little effect on the Nusselt number.


Experimental Study on Heat Transfer Characteristics of Array Impingement With Initial Cross-Flow

Division / Sponsor:
International Gas Turbine Institute (IGTI)

Paper Proceedings: https://asmedigitalcollection.asme.org/GT/GT2020/volume/84058

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