It can be seen from Table 2.1 that the composite index S of S3, 9, S10 and S11 is larger than that of S2, S5 and S7, which shows that the combustion performance of S3, S9, S10 and S11 is better than that of S2, S5 and S7. This result is consistent with the results of the ignition index (Dt) and burnout index (Df). In addition, the results of the composite index Hf are also consistent with the results of the ignition index (Dt) and burnout index (Df).