Time- and space-resolved quantitative LIF measurements of formaldehyde in a heavy-duty diesel engine

Abstract Formaldehyde (CH2O) is a characteristic species for the ignition phase of diesel-like fuels. As such, the spatio-temporal distribution of formaldehyde is an informative parameter in the study of the ignition event in internal combustion engines, especially for new combustion modes like homogeneous charge compression ignition (HCCI). This paper presents quantitative data on the CH2O distribution around diesel and n-heptane fuel sprays in the combustion chamber of a commercial heavy-duty diesel engine. Excitation of the 4 0 1 band (355 nm) as well as the 4 0 1 2 0 1 band (339 nm) is applied. We use quantitative, spectrally resolved laser-induced fluorescence, calibrated by means of formalin seeding, to distinguish the contribution from CH2O to the signal from those of other species formed early in the combustion. Typically, between 40% and 100% of the fluorescence in the wavelength range considered characteristic for formaldehyde is in fact due to other species, but the latter are also related to the early combustion. Numerical simulation of a homogeneous reactor of n-heptane and air yields concentrations that are in reasonable agreement with the measurements. Formaldehyde starts to be formed at about 2 °CA (crank angle degrees) before the rise in main heat release. There appears to be a rather localised CH2O formation zone relatively close to the injector, out of which formaldehyde is transported downstream by the fuel jet. Once the hot combustion sets in, formaldehyde quickly disappears.

[1]  J. Ghandhi,et al.  Investigation of light load HCCI combustion using formaldehyde planar laser-induced fluorescence , 2005 .

[2]  N. Peters,et al.  Temperature cross-over and non-thermal runaway at two-stage ignition of n-heptane , 2002 .

[3]  Robert P. Lucht,et al.  Unburned Gas Temperatures in an Internal Combustion Engine. II:Heat Release Computations , 1987 .

[4]  B. Draine,et al.  Do the Infrared Emission Features Need Ultraviolet Excitation? The Polycyclic Aromatic Hydrocarbon Model in UV-poor Reflection Nebulae , 2002, astro-ph/0201060.

[5]  Formaldehyde formation in the endgas of Otto engines: Numerical simulations and quantitative concentration measurements , 1999 .

[6]  K. Shibuya,et al.  Vibrational and electronic energy transfers from a single vibronic level of H2CO (?, 1A2), the 41 level , 1978 .

[7]  Bengt Johansson,et al.  Studies of the combustion process with simultaneous formaldehyde and OHPLIF in a direct-injected HCCI engine , 2005 .

[8]  Andrew G. Glen,et al.  APPL , 2001 .

[9]  C. Westbrook,et al.  A Comprehensive Modeling Study of iso-Octane Oxidation , 2002 .

[10]  G. G. Stokes.  "J." , 1890, The New Yale Book of Quotations.

[11]  K. Innes,et al.  Energy and character of the lowest excited singlet state of acetaldehyde , 1961 .

[12]  Rsg Rik Baert,et al.  Soot and chemiluminescence in diesel combustion of bio-derived, oxygenated and reference fuels , 2009 .

[13]  Miss A.O. Penney.  (b) , 1974, The New Yale Book of Quotations.

[14]  Edward K. C. Lee,et al.  Radiative and nonradiative transitions in the first excited singlet state of simple linear aldehydes , 1975 .

[15]  Dick T. Co,et al.  Rotationally resolved absorption cross sections of formaldehyde in the 28100-28500 cm(-1) (351-356 nm) spectral region: implications for in situ LIF measurements. , 2005, The journal of physical chemistry. A.

[16]  F. Pope,et al.  Absorption cross sections of formaldehyde at wavelengths from 300 to 340 nm at 294 and 245 K. , 2006, The journal of physical chemistry. A.

[17]  Edward K. C. Lee,et al.  Radiative and nonradiative transitions in the first excited singlet state of symmetrical methyl‐substituted acetones , 1975 .

[18]  N. Sijtsema,et al.  Quantitative spectrally resolved imaging through a spectrograph. , 2003, Optics letters.

[19]  Pradeep Mitra Ecspe,et al.  REPORT NO , 2001 .

[20]  M. Musculus,et al.  In-cylinder unburned hydrocarbon visualization during low-temperature compression-ignition engine combustion using formaldehyde PLIF , 2007 .

[21]  Phillip H. Paul,et al.  Planar laser-induced-fluorescence imaging measurements of OH and hydrocarbon fuel fragments in high-pressure spray-flame combustion. , 1995, Applied optics.

[22]  R. V. Basshuysen,et al.  Internal Combustion Engine Handbook , 2004 .

[23]  John B. Heywood,et al.  Internal combustion engine fundamentals , 1988 .

[24]  Hidenori Kosaka,et al.  Two-dimensional imaging of ignition and soot formation processes in a diesel flame , 2005 .