Investigations on a Spark Ignition Engine, Part I: Fuelled With Biogas Extracted From Sewage

Abstract

In this study, experiments were conducted on a single-cylinder, four-stroke modified diesel engine into a spark ignition engine using biogas from sewage sludge as fuel. The engine was operated at 1500 revolutions per minute at a compression ratio of 13:1. The throttle was set to 25% and 100% to operate the engine at various equivalence ratios to study the combustion, performance, and emissions. At various equivalence ratios and throttle openings, the effects of cycle-by-cycle variation were studied and compared. The brake thermal efficiency and brake power reached their highest values at an equivalence ratio of 0.95 and 1.01 respectively. At these equivalence ratios, carbon monoxide and hydrocarbon emissions were minimal but nitric oxide levels were high. When the mixture becomes lean, the coefficient of variation of the mean effective pressure increases considerably on both throttles. When the engine is running in steady conditions far from the lean limit, the cycle-by-cycle variation is stochastic in nature. Prior cycle impacts and cycle-by-cycle variation occur when the engine is running lean, and they are deterministic. Part II of this study represents the effect of hydrogen addition and change in compression ratio in the performance of spark ignition engines fueled with biogas.