This paper describes the development and a demanding field application of a double charge-coupled device (CCD) camera system, which allows simultaneous imaging at two different wavelength bands through common front-end optics. The imaging system has been assembled using two 1280 × 1024-pixel, 12-bit digital cameras together with standard, commercially available optical components for image splitting and filtering. The pixel resolution and wavelength separation of the system can be changed according to the requirements of the given application and the basic optical set-up can be used together with a variety of different types of front-end optics. The construction and performance of the double-camera system are described, together with preliminary experimental results from applying the system to in-cylinder combustion diagnostics of heavy-duty size-class, direct-injection diesel engines. To provide optical access into the combustion chamber of series-production-type engines, endoscope-based optics were used together with the camera system. Images taken at the two separate wavelength bands were used to calculate pyrometric diesel flame temperatures based on the blackbody radiation of the soot contained in the flame. The measurement system has been applied to engines with cylinder bores ranging from 20 cm up to 64 cm, delivering 0.15-1.6 MW power per cylinder during the measurements. In this paper specific results from measurements with Wärtsilä 4L20 and 6L32 engines are reported. These engines have 20 and 32 cm cylinder bores, respectively. In addition to the two-colour flame-temperature measurements, spectrally resolved measurements were performed to investigate a cloud-like, self-luminous phenomenon that was observed above the piston top even prior to the injection of fuel into these engines. This phenomenon was associated with the evaporating and chemically reacting fuel that originates from the residues which have been carried onto the piston top from the previous cycles. For the in-cylinder measurements reported here, the production-type test engines were only slightly modified to accept the endoscopic optics. During the measurements the engines were operated with realistic diesel fuels and other operation parameters. To the best of our knowledge, there have been no previous corresponding measurements reported in the literature for diesel engines of this size.

A heated and pressurized quartz cell with 150.5-mm pathlength was used to experimentally determine UV absorption spectra and further absorption cross sections of SO2, C2H2, and O2 in the wavelength range between 200 and 400 nm. Spectra were recorded at room temperature, and at 600 and 800 °C and at absolute pressures between 1 and 6 bar. A 30-W deuterium lamp was used as a light source, and the light was detected with a photomultiplier tube through a 0.4-m Czerny–Turner monochromator. Slit widths of the monochromator were adjusted to achieve a 5 Å measurement bandwidth, and the scan through the wavelength range was made in 5 Å steps. For each individual temperature and pressure level, a reference spectrum was first recorded with the cell filled with nitrogen. After this, the cell was filled with the selected species mixed with nitrogen, and the absorption spectra were recorded in similar conditions. The studied gas mixtures were calibrated to 3% accuracy.

No abstract

No abstract

No abstract