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.
