The effect of centrifugal acceleration on the mixed flame speed has over time been observed to be significantly important in both theoretical research and engineering application. Recently, empirical investigations on the novel inter-turbine burner engine and the Ramgen engine have shown that they possess significant benefits on performance, since they apply the concept of combustion in high centrifugal fields. Previous studies on centrifugal forces have revealed that high centrifugal acceleration possess significant strengthening effect on combustion. On the contrary, little exists on the adaptation, derivation and harnessing of this power in written academia.
Researchers led by professor Yong Huang at the Collaborative Innovation Center of Advanced Aero-Engine, National Key Laboratory of Science and Technology, School of Energy and Power Engineering, Beihang University described the effect of centrifugal acceleration, specifically high centrifugal acceleration of more than 200 times the gravitational acceleration, on the premixed flame speed in a rotating closed tube. Their main objective was to derive a theoretical predicted correlation which would describe the laminar premixed flame speed in a centrifugal field with the aid of directly solving simplified governing equations on 1-D steady adiabatic flame by theoretical analysis. Their research work is now published in International Journal of Hydrogen Energy.
The research team begun by employing the 1-D steady adiabatic flame model which was fixed. The team then obtained the premixed flame speed in a rotating closed tube after considering the amplification effect of the closed tube on the laminar premixed flame speed. The researchers then, using the predicted correlation, obtained the physical mechanisms of the premixed flame speed in a rotating closed tube.
The authors observed that the flame speed accelerated by the centrifugal force was nearly proportional to the square root of the centrifugal acceleration in the rotating closed tube. The team also noted that the theoretical prediction was also able to revealed that the flame speed in a rotating closed tube was determined by the initial temperature, the critical ignition temperature, the adiabatic flame temperature and the thicknesses of reaction zone. Eventually, the premixed flame speed in a rotating closed tube was seen to increase nearly linearly with the increasing of the initial temperature or square root of the thicknesses of reaction zone, or with decreasing of the critical ignition temperature or the adiabatic flame temperature.
Herein, a theoretical analysis to study the effect of centrifugal acceleration, especially high centrifugal acceleration, that is, more than 200 times the gravitational acceleration of earth, on the premixed flame speed has been successfully presented. More importantly, a theoretical predicted correlation has been proposed to describe the premixed flame speed in a rotating closed tube. The results of the theoretical prediction have been seen to agree well with the empirical data obtained by Lewis & Smith. The result of the study verifies that the flame speed accelerated by the centrifugal force is nearly proportional to the square root of the centrifugal acceleration.
Lei Sun, Yong Huang, Yingyi Ji. Theoretical analysis for the centrifugal effect on premixed flame speed in a closed tube. International Journal of Hydrogen Energy, volume 42(2017) pages 18658 – 18667.Go To International Journal of Hydrogen Energy