3.3.3. The Effect of WPO–Gasoline RON 90 Blends on Thermal Efficiency

Based on experimental results presented in Figure 10, there was a relationship between engine speed and brake thermal efficiency with the use of the different WPO–gasoline blends. Pure RON90 showed higher thermal efficiency compared to WPO blends. The thermal efficiency for WPO-RON90-10, WPO-RON90-20, and WPO-RON90-30 were obtained as 38.65%, 37.5%, and 38.41%, respectively, at an engine speed of 2000 rpm. For the same engine speed, the thermal efficiency of pure RON90 reached 43.05%. The highest brake thermal efficiency for each type of blend was 38.75%, 37.56%, and 38.41% for WPO-RON90-10, for WPO-RON90-20, and WPO-RON90-30, respectively, at 2000 rpm. Overall, the thermal efficiency for all fuels increased at 2000 rpm compared to that of 1500 rpm. However, as the engine speed increased from 2500 rpm to 3500 rpm, the thermal efficiency decreased. The decreased thermal efficiency can be attributed to the lower heating value of WPO. Secondly, after the efficiency increase of the first stage at 1500–2000 rpm engine speed, thermal efficiency continues to decrease for all types of fuel to 3500 rpm engine speed. This is probably due to the high research octane number on the RON90, meaning that fuel can be compressed because of the ability of high-octane fuels to resist auto-ignition. Usually, more power is generated due to increased efficiency and to higher compression.

**Figure 10.** Effect of WPO-RON90 blends on thermal efficiency compared to RON90.

#### **4. Conclusions**

Pyrolysis of waste plastic was performed in a batch reactor equipped with temperature-controlled reflux to produce WPO. It was found that the properties of WPO are close to that of gasoline fuel. The properties of WPO were also found to be within the limits mandated in ASTM standard. From the results of this study, the following conclusions can be drawn:


**Author Contributions:** Conceptualization, methodology, writing-original draft and supervision by K. T.M.I.R. contribute to validation and writing-review & editing. S.B., S.E.S., J.J. and M.J. contributed to the experiment and investigation. F.K., Y.P., A.S.S. and A.H.S. contributed to analysis the data and improve the manuscript. All authors read and approved the final manuscript.

**Funding:** This research was funded by the Universitas Syiah Kuala, Minister of national education through Research Professor Program No.: 520/UN11/SPK/PNBP/2019.

**Acknowledgments:** The authors graciously acknowledge the financial support provided by the Chair of the Renewable Energy Research Fund—Biofuel/Bioenergy Research Program (201801 KETTHA). The authors would like to appreciate many thanks to bachelor students (Razuardi Kumar) and magister students (T.M Hakim Furqan) in the combustion Laboratory of Mechanical Engineering Department who has supported to conducting of the research. The authors wish to express their appreciation to the Direktorat Jenderal Penguatan Riset dan Pengembangan Kementerian Riset dan Teknologi/Badan Riset dan Inovasi Nasional Republik Indonesia and Politeknik Negeri Medan, Medan, Indonesia.

**Conflicts of Interest:** The authors declare no conflict of interest.
