Effects of waste tire-based pyrolysis oil-diesel fuel blends on the performance and emissions of a diesel engine

---

Thesis Type: Postgraduate

Institution Of The Thesis: Yozgat Bozok University, Institute of Postgraduate Education, MAKİNE MÜHENDİSLİĞİ ANABİLİM DALI, Turkey

Approval Date: 2026

Thesis Language: Turkish

Student: OKAN TUNCER

Supervisor: Zeki Yılbaşı

Abstract:

The sharp growth in per capita energy demand due to industry and population growth, added to environmental problems, has led to a shift towards renewable and alternative energy sources. Waste tire oil (WTO), obtained from end-of-life tires, a significant source of environmental pollution, is of great importance in terms of both waste management and energy recovery due to its potential as a fuel additive. In this thesis, the effects of adding WTO obtained through pyrolysis to diesel fuel at specific ratios on the performance and emissions of diesel engines were experimentally investigated. In the study, ALY2, ALY5, and ALY10 fuel blends, consisting of 2% WTO, 5% WTO, and 10% WTO, respectively, were made with D100 reference diesel fuel, and their density, viscosity, lower calorific value, and elemental analyses were analyzed. Tests were carried out on a single-cylinder, direct-injection diesel engine at 25%, 50%, 75%, and 100% engine loads. The data collected showed that WTO blends have a lower hydrogen/carbon (H/C) ratio and lower calorific value than D100, and that their viscosity values are acceptable for fuel injection systems. In engine performance tests, it was observed that due to the lower calorific value of WTO-based fuels, the mass fuel consumption increased and the brake specific fuel consumption values increased in order for the engine to deliver the same power output. With each increase in engine load, the rise in cylinder temperatures reduced the volumetric efficiency and caused the air excess coefficient (λ) to fall below the critical smoke limit at full load (λ = 1.28 for ALY10). When the emission results were examined, it was determined that nitrogen oxide emissions decreased due to the enrichment of the mixture with increasing WTO ratio, but the high carbon content and oxygen deficiency of fuels containing WTO caused an increase in carbon monoxide, smoke, and unburned hydrocarbon emissions. It was concluded that WTO blends can be used in the engine without any modifications, but that using oxygen-containing additives would be beneficial to improve emissions.