## 3 Results and Discussion
### Influence of Blended Ratio on Combustion Characteristics  
Figure 3 presents the weight loss and rate of weight loss curves of the samples obtained by blending SC with HTB and OS in different ratios at a temperature heating rate of 10 \({}^{\circ}\)C min\({}^{-1}\). As mentioned in the previous section, based on the DSC curves, the entire combustion process could be separated into five stages (see Figure 3E,F). The DSC curves and DTG curves show the same tendency. Initial peaks can be seen on all DTG curves around 310 \({}^{\circ}\)C. The first peak is higher than OS but significantly lower than that of HTB combustion alone. The peak temperature of the second peak is between 365 and 542.8 \({}^{\circ}\)C, which is much lower than that of SC. This indicates that the blending of OS and HTB promotes the combustion reaction of tri-fuel. The values of the peaks vary irregularly.  
When the SC content in the tri-fuel is high (Figure 3A,C,E), the first peak value of the DTG curve is smaller than the second. The tri-fuel does not begin to release a large amount of heat until Stage 3. The above phenomenon indicates that the tri-fuel is dominated by the combustion of fixed carbon mainly. The exothermic peak of Stage 3 is as high as 24.8 w g\({}^{-1}\) for a mixing ratio of SC:HTB:OS = 50%:40%:10%, while its exothermic peak of Stage 2 is lower than for SC:HTB:OS = 50%:35%:15%. From Figure 3A, when the SC content is high and the OS percentage is low, significant weightlessness can be seen. The final weight loss is highest at mixing ratios of SC:HTB:OS = 50%:30%:20%, 50%:40%:10% and 45%:45%:10%, which can reach 90%. When SC:HTB:OS is 45%:35%:20%, the combustion characteristics are poor, and the weight loss is only 49.3%. The tri-fuel exergy at this ratio does not exceed more than 10 w g\({}^{-1}\), which indicates that the tri-fuel has an inhibitory effect on combustion. And its \(C_{\rm i}\) is only 0.23 \(\times\) 10\({}^{-7}\), which is the lowest among all mixing ratios. When the SC mixing ratio is high, excessive OS inhibits the tri-fuel's combustion. After mixing OS, the ignition temperature of the tri-fuel rises.  
Figure 3B,D,F show TG, DTG and DSC curves for a low SC percentage mixed tri-fuel. Figure 3F shows that the heat release in Stage 2 is overall higher than that of tri-fuels with a high SC percentage blending. The combustion advances and Stage 2's involvement in the combustion pathway rises as the mixing ratio of HTB and OS increases. When the SC:HTB:OS is 40%:50%:10% and 35%:45%:20%, respectively, the first peak of the DTG curve is larger than the second peak. At the same time, Table 2 shows that the \(T_{\rm i}\) of the two mixing ratios are 271.5 and 269.8 \({}^{\circ}\)C, respectively, and the combustion temperature is also advanced. Additionally, when \(C_{\rm i}\) is 1.2 \(\times\) 10\({}^{-7}\), the optimal mixing ratio for combustion efficiency is 40%:50%:10%. The performance of combustion obviously improves when HTB adopts the primary body. Different from previous studies [38; 39], as the OS mixing ratio increases from 10% to 20% with the 45% HTB, \(T_{\rm i}\) and \(T_{\rm h}\) decrease from 354.9 and 514.3 \({}^{\circ}\)C to 269.8 and 452.7 \({}^{\circ}\)C, respectively. For OS, the modification of \(T_{\rm i}\) is greater than that of \(T_{\rm h}\). When the HTB mixing ratio is higher than 50% or lower than 40%, the blending of OS would reduce the expected combustion performance of the tri-fuel.  
Stage 2's heat output is considerably less than Stage 3's heat emission, the exotherm of Stage 2 is still not high. Carbon in compound form has a lower calorific value than fixed carbon. This clarifies why the rate of weight loss decreased but the heat release rose from Stage 2 to Stage 3 when the SC, HTB and OS were, respectively 40%, 50% and 10% and 35%, 45% and 20%. Compounds containing carbon can increase ignition characteristics and combustion performance without producing much heat.