Toward in-cylinder absorption tomography in a production engine

Abstract

Design requirements for an 8000 frame/s dual-wavelength ratiometric chemical species tomography system, intended for hydrocarbon vapor imaging in one cylinder of a standard automobile engine, are examined. The design process is guided by spectroscopic measurements on iso-octane and by comprehensive results from laboratory phantoms and research engines, including results on temporal resolution performance. Novel image reconstruction techniques, necessary for this application, are presented. Recent progress toward implementation, including details of the optical access arrangement employed and signal-to-noise issues, is described. We present first cross-cylinder IR absorption measurements from a reduced channel-count (nontomographic) system and discuss the prospects for imaging.

Tomographic imaging of the liquid and vapour fuel distributions in a single-cylinder direct-injection gasoline engine

“…For the case of iso-octane/air at these pressures, it has been shown previously [21] that the temperature dependence of k is negligible.…”

“…This absorption feature of long-chain hydrocarbons is very broad (~15 nm half-width at half-maximum) and unstructured, as discussed in [21], when compared with the very narrow spectral width of the diode laser sources used, and when compared with the sub-nm width of absorption features of small molecules that are typically measured in tunable diode laser absorption spectroscopy (TDLAS) systems [22]. The spectral absorption properties of air/HC fuel mixtures are relatively easy to calibrate in terms of temperature and pressure, as reported in [21,23]. For a stoichiometric mixture of air and iso-octane, at about 10 bar pressure in a typical gasoline engine cylinder, a beam of light at 1700 nm passing diametrically through the cylinder will undergo around 5% absorption by HC molecules.…”

“…The above treatment of the first term in exponential form is a departure from the previous practice in [5,21,23], and is found to be helpful below. Both terms are explicitly stated in terms of their deviation from their values at θ ref .…”

A Study of Two Dimensional Tomography Reconstruction of Temperature and Gas Concentration in a Combustion Field Using TDLAS

“…Therefore, the set volume fractions of H 2 O C set in the measurement grids are assumed to be 0.17 ± 0.005 and 0.015 ± 0.005, correspondingly. It is known that the orientation of the view and the number of rays per view has a significant bearing on the quality of reconstruction [28,29]. Therefore, we assumed four different laser beams distributions to study the influence on the reconstruction in simulations.…”

Robust, spatially scanning, open-path TDLAS hygrometer using retro-reflective foils for fast tomographic 2-D water vapor concentration field measurements

“…These setups allow for very fast measurements, since all channels can be recorded simultaneously and the field measurement rate equals the rate at which the concentrations along each projection are measured. However, such highly parallel, bi-static setups either require large amounts of light-source-detectorpairs and the appertaining data acquisition channels (Wright et al, 2005;Terzija et al, 2008;Terzija and McCann, 2011;Ma et al, 2013) or are somewhat limited regarding spatial resolution (Ma et al, 2009;Deguchi, 2012). Additionally, a disadvantage of bi-static setups in field applications is the cumbersome alignment of many detectors.…”