Search Results

Extending the planar Particle Image Velocimetry (PIV) technique to enable measurements on multiple planes simultaneously allows for some of the 3 dimensional nature of unsteady flow fields to be investigated. This requires less hardware and retains the typically higher spatial resolution of planar PIV compared to fully 3-dimensional PIV techniques. Performing multi-plane PIV measurements requires the light scattered from the different measurement planes to be distinguishable. This may be achieved by using different laser wavelengths which adds significantly to the expense and complexity of the system, by using different light sheet polarisations which is challenging for engine measurements through windows due to stress-induced birefringence, or by making alternating measurements of each plane which sacrifices the simultaneity of the flow measurement across multiple planes.

In-cylinder temperature measurements are vital for the validation of gasoline engine modelling and useful in their own right for explaining differences in engine performance. The underlying chemical reactions in combustion are highly sensitive to temperature and affect emissions of both NOx and particulate matter. The two techniques described here are complementary, and can be used for insights into the quality of mixture preparation by measurement of the in-cylinder temperature distribution during the compression stroke. The influence of fuel composition on in-cylinder mixture temperatures can also be resolved. Laser Induced Grating Spectroscopy (LIGS) provides point temperature measurements with a pressure dependent precision in the range 0.1 to 1.0 % when the gas composition is well characterized and homogeneous; as the pressure increases the precision improves.

Model M15 gasoline fuels have been created from pure fuel components, to give independent control of volatility, the heavy end content and the aromatic content, in order to understand the effect of the fuel properties on Gasoline Direct Injection (GDI) fuel spray behaviour and the subsequent particulate number emissions. Each fuel was imaged at a range of fuel temperatures in a spray rig and in a motored optical engine, to cover the full range from non-flashing sprays through to flare flashing sprays. The spray axial penetration (and potential piston and liner impingement), and spray evaporation rate were extracted from the images. Firing engine tests with the fuels with the same fuel temperatures were performed and exhaust particulate number spectra captured using a DMS500 Mark II Particle Spectrometer.