The thermo-structural response of submerged nozzles is widely investigated in the design of modern rockets upon thermal loading and aerodynamic pressure. In this paper, by means of commercial finite element software with the subroutine of non-uniform pressure and non-uniform heat transfer coefficients, the simulation was performed to study the thermo-structural response of a submerged nozzle at the pressure 6MPa and stagnation temperature 3200K. By means of fluid software, the steady flow field with hot gas was determined. The aerodynamic parameters and heat coefficients were obtained. It was found that the thermal loading has an important influence on stress of throat insert for the solid rocket motor (SRM). Secondly, the hoop stress increases at first and then decreases with the increase of time for the throat insert. Finally, the ground hot firing test of SRM with submerged nozzle was carried out. The structural integrity of the submerged nozzle is very perfect during SRM operation. The present method is reasonable, which can be applied to study the thermo-structural response of submerged nozzle for SRM.

SummaryExperiments were performed to investigate the flame thickness of the upward flame on the poly(methyl methacrylate) slabs with width of 100-400 mm. The results indicated that the flame thickness exhibited an increase first and then decrease trend in the upright orientation, and the maximum thickness location was approximately equal to the pyrolysis front location. The thickness of the flame along the lateral side of slab was less than that of the interior flame. The flame maximum thickness as a function of pyrolysis height and width was obtained, which showed the maximum thickness provided a power law increase with the pyrolysis height and width. Furthermore, the maximum thickness exhibited a power law increase with the total heat release rate as well. Based on the obtained flame thickness, the radiation heat flux at the pyrolysis height was The flame height correlation as shown in Equations 1 and 2 were obtained based on theoretical analysis and experimental data 4-9where a, b, and n are constants, x fl is the flame height, x p is the pyrolysis height, and _ Q ′ is the heat release rate (HRR) per unit width. However, the previous researches mentioned above did not consider the

No abstract

The burning characteristics of conduction-controlled pool fires under a ceiling have not been revealed in the past. In this paper, experiments on square ethanol pool fires with dimensions of 4, 6, and 8 cm under the ceiling of various heights were conducted to investigate the ceiling effect on the burning rate of conduction-controlled pool fires. Results show that when the ceiling close to the pool, the burning process exhibited an extra initial steady-stage before its development stage in the burning process. Moreover, a flame-wrapping phenomenon was observed in the later period of this burning process. The pool rim wall temperature and mass burning rate exhibited an increase with the decreasing ceiling height. The rim wall temperature increase was pronounced in relative larger pool fires. However, the burning rate enhancement was prominent in relative smaller ones. The burning rate enhancement was found to be mainly attributed to the increase in pool rim wall temperature. A global factor was developed to correlate the mass burning increment with rim wall temperature increase and pool size, which was confirmed by experimental data.

Original scientific paper https://doi.org/10.2298/TSCI160705200DIn this work, experiments were conducted to study the upward flame spread with cross wind at an early stage (prior to the acceleration of pyrolysis spread rate of the wide slab). An exponential model was fitted to the experimental data of the spread rate of pyrolysis front and the dimensionless cross wind speed, which showed satisfactory results. The pyrolysis front tilt angle showed a decreasing trend with a low cross wind speed. However, at high cross wind speeds, the pyrolysis tilt angle exhibited an increasing trend with the maximum value of 45°. The flame lengths increased with the cross wind for narrower slabs, whereas the phenomenon was most pronounced for the narrowest slab. Additionally, the flame length did not exhibit the lengthening phenomenon for the wider slab (0.1 m). Furthermore, the flame tilt angle did not exhibit significant change over time (even along the pyrolysis length). The correlation of flame tilt angle with the cross wind speed and width was also obtained in this study. The flame tilt angle presented a power-law increase with respect to the dimensionless cross wind speed.