Towards cleaner combustion engines through groundbreaking detailed chemical kinetic models

Abstract

In the context of limiting the environmental impact of transportation, this paper reviews new directions which are being followed in the development of more predictive and more accurate detailed chemical kinetic models for the combustion of fuels. In the first part, the performance of current models, especially in terms of the prediction of pollutant formation, is evaluated. In the next parts, recent methods and ways to improve these models are described. An emphasis is given on the development of detailed models based on elementary reactions, on the production of the related thermochemical and kinetic parameters, and on the experimental techniques available to produce the data necessary to evaluate model predictions under well defined conditions. A IntroductionEven with the expected development of new and cleaner sources of energy, it is still believed that the combustion of liquid fuels will remain the main source of energy for transportation for the next 50 years 1 . It is therefore of the highest importance to limit the environmental impact of using these fuels during this transition period. As traditional fossil fuels are considered to be largely responsible for causing important atmospheric degradations 2 such as global warming 3 , acid rain, and tropospheric ozone increase, an important effort has been made by industry to develop both more efficient types of engines and cleaner types of fuels. A good example is the development of Homogeneous Charge Compression Ignition (HCCI) engines. The HCCI engine is characterised by the fact that the fuel and air are mixed before combustion starts and the mixture auto-ignites as a result of the temperature increase in the compression stroke 4 . This new type of engine has been proposed not only because of its high efficiency compared to that of diesel engines, but also because of its very low emissions compared to gasoline engines with a catalytic converter. With regard to fuels, there is an increasing interest to shift from hydrocarbon fossil fuels to biofuels (particularly bioethanol and biodiesel) 5,6,7,8,9 .While it is especially important to lower the emissions of CO 2 through the use of more efficient powertrains and through an increased biomass derivative content in traditional fuels, the emission reduction of other pollutants should certainly not be neglected. A paper of Wallington et al. 10 describes the parts of automotive engines which could be sources of

Combustion chemistry and flame structure of furan group biofuels using molecular-beam mass spectrometry and gas chromatography – Part I: Furan

“…Calibration of reactant species was done using the same approach at the burner surface. The error in the mole fractions is estimated to be less than 15% for major species and less than 20% for H 2 . Further details on the calibration procedures and on the error estimation can be found in Ref.…”

“…Eq. (1) then simplifies to: (2) where k i (E) is the species-and energy-dependent calibration factor. With this normalization, all parameters can be condensed into a calibration factor k i (E).…”

“…Decades of research have been performed to provide chemical databases for the conventional hydrocarbon fuels, but similar information on the richer chemistry of oxygenated and other bio-derived fuels is comparatively recent [1,2]. The so-called "furanics", including furan and its derivatives, are potential biofuels and have significant advantages compared to first-generation biofuels [3][4][5].…”

Quantification of OH and HO 2 radicals during the low-temperature oxidation of hydrocarbons by Fluorescence Assay by Gas Expansion technique

“…For this purpose, a heated JSR has been used, a device that has already been used many times for studying the chemistry of organic compounds before ignition (15). Note that this reactor has been recently used to follow the formation of alkylhydroperoxides (17) and H 2 O 2 (18) through its coupling with a reflectron time-of-flight mass spectrometer and cw-Cavity Ring Down Spectroscopy (CRDS) cell, respectively.…”

“…A JSR allows studying gas-phase reactions at temperatures up to 1,000 K without external radical production. Such measurements will be particularly valuable for improving knowledge of the chemistry and detailed kinetic models in the temperature zone (650-900 K), in which reaction mechanisms are the most complex and the kinetic data are the least accurate (15).…”