Michael Buchman

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. 2 Buchman et al. / SAE Int. J. Engines / Volume 11, Issue 4, 2018

Method for Turbocharging Single Cylinder Four Stroke Engines

This paper presents a feasibility study of a method for turbocharging single cylinder, four-stroke internal combustion engines. Turbocharging is not conventionally used with single cylinder engines because of the timing mismatch between when the turbo is powered, during the exhaust stroke, and when it can deliver air to the cylinder, during the intake stroke. The proposed solution involves an air capacitor on the intake side of the engine between the compressor and the intake valves. The capacitor acts as a buffer and would be implemented as a new style of intake manifold with a larger volume than traditional systems. In order for the air capacitor to be practical, it needs to be sized large enough to maintain turbo pressure, cause minimal turbo lag and significantly increase the density of intake air. By creating multiple flow models of air through the turbocharged engine system, we found that the optimal size air capacitor is between four and five times the engine capacity. For a capacitor sized for a one-liter engine, the lag time was found to be approximately two seconds, which would be acceptable for slowly accelerating applications such as tractors, or steady state applications such as generators. The density increase that can be achieved in the capacitor, compared to air at standard ambient temperature and pressure, was found to vary between fifty percent for adiabatic compression and no heat transfer from the capacitor, to eighty percent for perfect heat transfer. These increases in density are proportional to, to first order, the anticipated power increases that could be realized with a turbocharger and air capacitor system applied to a single cylinder, four-stroke engine. NOMENCLATURE A Cross sectional area of connecting tube D Diameter of connecting tube F Friction factor K Minor losses L Length of connecting tube mc Mass of gas inside the capacitor