A Method for Turbocharging Single-Cylinder, Four-Stroke Engines

Turbocharging can provide a low cost means for increasing the power output and fuel economy of an internal combustion engine. Currently, turbocharging is common in multi-cylinder engines, but due to the inconsistent nature of intake air flow, it is not commonly used in single-cylinder engines. In this article, we propose a novel method for turbocharging single-cylinder, four-stroke engines. Our method adds an air capacitor-an additional volume in series with the intake manifold, between the turbocharger compressor and the engine intake-to buffer the output from the turbocharger compressor and deliver pressurized air during the intake stroke. We analyzed the theoretical feasibility of air capacitor-based turbocharging for a single-cylinder engine, focusing on fill time, optimal volume, density gain, and thermal effects due to adiabatic compression of the intake air. Our computational model for air flow through the intake manifold predicted an intake air density gain of 37-60% depending on heat transfer rates; this density translates to a proportional to power gain. An experimental setup was constructed to measure peak power, density gain, and manifold pressure. With an air capacitor seven times the volume of engine capacity, our setup was able to produce 29% more power compared to natural aspiration. These results confirm our approach to be a relatively simple means for increasing power density in single-cylinder engines. Therefore, turbocharging single-cylinder engines using an air capacitor can provide a lower cost alternative for increasing the power-output in diesel-powered machinery such as tractors, generators, and water pumps, when compared to adding an additional cylinder.