In-cylinder water measurements in an operating IC engine using a multi-wavelength measurement architecture

There is great interest in automotive R&D to image in-cylinder distributions of residual species from the previous combustion cycle, and water is a promising marker for this purpose. However, the near-IR absorption spectroscopy of water is characterised by many narrow lines. We report here engine tests of a recently published multi-wavelength measurement scheme. Three beams were launched through an optically accessed single-cylinder research engine, each carrying three wavelengths. Data from motored and fired operation are reported. Although not yet fully calibrated, the data are of good quality, and demonstrate many of the anticipated features of the engine cycle.