Issues Related to the Measurement of Regression Rate of Fast-Burning Hybrid Fuels

Abstract

The measurement of the regression rate of a hybrid rocket fuel is the subject matter of this paper. This is an involved problem because both the regression rate and the oxidizer mass flux G ox vary with the port diameter, which itself varies during combustion. This paper addresses the issue of how G ox should be varied to obtain the regression rate correctly. The most commonly used weight loss method has been employed here. Three methods used here to vary the G ox are artificially changing the port diameter, changing the mass flow rate of the oxidizer, and interrupted burn test. From the experiments conducted, it was evident that the interrupted burn test was the best method. These experiments were also carried out for a larger motor and the results compared quite well with established literature. The role of the recirculation zone size near the head end and the overall heat transferred back to the fuel surface in influencing the regression rate have been explained. The role of the recirculation zone diminishes as the length of the rocket motor is increased.

Measurement of regression rate in hybrid rocket using combustion chamber pressure

“…The maximum uncertainty in the measurement of regression rate, oxidizer mass flux and n were 2, 0.5 and 2.1, respectively. The uncertainty obtained here is smaller than those with weight loss method given in Table 2 [36].…”

“…The results are also compared using the regression rate obtained with the weight loss method with a burn time of 0.5 s reported in ref. [36]. It is observed from Fig.…”

“…12 that the O/F ratio obtained with this method matches well with those obtained using weight loss method after each 0.5 s reported in ref. [36]. The combustion efficiencies required to obtain the above regression rates using the algorithm developed are shown in Table 3 along with average value of combustion efficiency obtained (reported earlier in Table 1).…”

“…The high regression rate fuel used in the present study was wax (combination of 30% of micro-crystalline wax and 70% of paraffin wax) [36]. Commercially available gaseous oxygen was used as the oxidizer.…”

“…The uncertainty analysis in the measurement of regression rate, oxidizer mass flux and mass flux exponent[36] using the weight loss method.Fig. 12.…”