IN-CYLINDER MEASUREMENT OF MIXTURE MALDISTRIBUTION IN A L-HEAD ENGINE

The distribution of fuel-air mixtures in many L-head engines is not ho mogeneous. If the local mixture is too rich or too lean, then incomple te combustion occurs. This can play a major role in unburned hydrocarb on and carbon monoxide emissions. Fuel-air mixture distribution depend s on in-cylinder swirl and turbulence, and is directly related to inta ke-manifold configuration, fuel-delivery-system design and combustion- chamber shape. Understanding the spatial mixture distribution may help improve the design of these aforementioned components. Consequently, a more complete combustion process may result, and emissions reduced. An optical fiber bundle was used to measure the emissions of CH and C- 2 radicals in this research to map the mixture uniformity in the combu stion chamber. The experimental results showed that there exists a rel ationship between the intensity ratio (I-C2/I-CH) and the fuel equival ence ratio. The local fuel equivalence ratios can be obtained after th e relationship between the light intensity ratio and fuel equivalence ratio is established. In addition, fuel-rich combustion zones were ide ntified in the vicinity of spark plug and valves. Two fuels, propane ( C3H8) and Indolene (CH1.86)(7), were used for investigating the effect s of different types of fuel on the intensity ratio. A L-head spark-ig nition engine was selected for this study since this type of engine us es a conventional carburetor in which the fuel-air mixture is relative ly nonhomogeneous which produces high hydrocarbon emissions. Furthermo re, the flat cylinder head supplies sufficient space for the installat ion of the optical fiber bundles.