Interchangeability of Gaseous Fuels — The Importance of the Wobbe-Index

The Wobbe-index is introduced as an important gas quality criterion when interchanging gaseous fuels for engines. Changes in fuel gas composition appear not to induce noticeable changes in air to fuel ratio and combustion velocity when the Wobbe-index remains the same. This implies that no readjustment of ignition timing and air to fuel ratio settings is required, then. The volumetric energy content, the explosion limits and the knock resistance of a mixture can vary to a moderate extent when the Wobbe-index is constant and the gas composition varies.