Figure 7 shows the results of TGA and DTA for heavy oil A. The results indicate that evaporation of the heavy oil takes place at about 60 ℃ and ignition occurs at around 300 ℃. Figure 8 shows the results of TGA and DTA for PE2. The results show that evaporation of PE2 takes place at about 280 ℃ and ignition occurs at around 410 ℃. From these results, it appears that the thermal properties of the plastics are quite different from those of heavy oil A. Figure 9 and 10 show the results for 10% PE2 polymer fuel and 5% PP2 polymer fuel, respectively. As can be seen, vaporization takes place at over 80 ℃. At around 300 ℃, rapid heat release is observed. From these results, it is suggested that the ignition temperature and vaporization characteristics of polymer fuels are similar to those of heavy oil A. Therefore, these polymer fuels can be applied to use in a diesel engine. The TGA results over 300 ℃ are influenced by the plastics in the polymer fuel, which suggests that the plastics become physically mixed with heavy oil at these temperate.
4.1 Production of Polymer Fuel
Polymer fuels to be used in the diesel combustion tests were prepared by the facilities shown in Fig. 2. In the production process, in order to promote the melting and mixing of the plastics, the heavy oil was heated at 220 ℃ in the mixer prior to adding the plastics. Heating took about 60 minutes for 20 kg of heavy oil A. After the addition of plastic, the mixing conditions of heavy oil A and plastics were monitored by extracting a sample of polymer fuel from the bottom of the mixer at 10 minute intervals. About 30 minutes of mixing at 220 ℃ produced homogeneous polymer fuel. The conditions of polymer fuel production are listed in Table 3. The evaporated fractions generated in this process were collected in the buffer tank and returned to the polymer fuel in the mixing tank (Fig. 2). The masses of the evaporated fractions are listed in Table 3. Most of the evaporated fractions seem to have been produced during the heating of heavy oil A. For the case in which the temperature of the mixer and heavy oil A was maintained at 170 ℃, the evaporated fraction was only 2.5%. However, at this temperature, about 100 minutes of mixing was required in order to produce homogeneous polymer fuel after adding plastic to heavy oil A.
4.2 Application to Diesel Engines
The polymer fuels made with 5% PE2, 25% PP1 and 5% PP2 were tested and the results were compared with the test results of heavy oil A. The engine test was performed at an engine speed of 1200 rpm, and under loads of 25% to 100%. Injection timing was set at 15deg. BTDC. In order to maintain the viscosity of the fuels at around 20 cSt, the fuel was heated at 130 to 150 ℃. The injection timing was adjusted to obtain the maximum thermal efficiency for heavy oil A operation.
Figure 11 shows the pressure history in the cylinder and the needle lift for heavy oil A. The pressure history and needle lift for the 5% PE2, 25% PP1 and 5% PP2 fuels are shown in Figs. 12, 13 and 14, respectively.
Fig. 8 The results of TGA and DTA for PE 2
Fig. 9 The results of TGA and DTA for 10% PE2 fuel
Fig. 10 The results of TGA and DTA for 5% PP2 fuel
