Enhancement of waste heat conversion efficiency from an internal combustion engine using a turbocharger with an extension

Approximately 30–40 % of the heat energy of an internal combustion engine is wasted through the exhaust gas. The continuous demand for energy and growing concern about environmental issues have led to the exploration of alternative energy sources, such as waste heat recovery from internal combustion engines. One method for recovering energy from exhaust gas is to utilize a turbocharger. Usually, a turbocharger is placed at the end of the exhaust manifold, resulting in low energy conversion efficiency. In the present study, an extension is placed in between the exhaust manifold and the turbocharger of a 1331 cc 4-cylinder petrol engine to improve the energy conversion efficiency. The three configurations of the extension passage, including Convergent-Divergent, Divergent-Convergent, and Convergent, are considered to utilize the maximum possible exhaust gas energy conversion to electrical energy. A 12V DC motor is used as a generator by connecting its shaft to the turbocharger, which causes it to generate electricity as it rotates. Various performance parameters, such as engine speed, turbocharger speed, exhaust gas temperature, pressure drop, and engine efficiency, are considered for each configuration. The results show that the Convergent-Divergent configuration provides the highest energy recovery of approximately 663.1 W. These findings indicate that the Convergent-Divergent configuration significantly enhances energy recovery (2.3 %) from waste heat, which is more than double (i.e., 1.1 %) the amount reported in the literature. In addition, based on the maximum obtained energy from exhaust gas, it could lead to saving 112 L of fuel per year and a 5.7 % reduction of CO 2 emission for a typical vehicle, offering a promising solution for the development of more efficient and sustainable energy generation systems for automotive applications.