The research and development of in situ non-intrusive optical and temperature diagnostics in an internal combustion engine
Novel instrumentation has been developed and evaluated in a low-cost, purpose built, single-cylinder internal combustion engine test facility designed to simulate many of the combustion features that are common between an internal combustion engine, a gas turbine combustor and a steel rolling furnace. High bandwidth in-cylinder surface temperature measurements are demonstrated with a new application of platinum thin film resistance thermometers. These gauges are exposed to the combustion gases and are mounted to both the cylinder head and piston. It is shown that calculation of flame speed, determination of heat flux levels and flame structure observation are possible. Fibre optic probes capable of high frequency spectral measurements of the combustion emission are presented. The spectral measurements are shown to complement the temperature measurement by being able to differentiate the flame front from the general combustion emission and hot by-products. Beyond this, other optical techniques have been explored in order to gain an understanding of the flame front and flow within the combustion chamber. The novel spark plug described is capable of combustion imaging and its application to in-cylinder PIV and flow visualisation is demonstrated. Combustion modelling has been undertaken using published engine models and a comparison between measured and predicted values of pressure and heat flux is provided as a validation of the in-cylinder heat flux measurements.