Cleaner Combustion

Abstract

The jet-stirred reactor is a type of ideal continuously stirred-tank reactor which is well suited for gas phase kinetic studies. It is mainly used to study the oxidation and the pyrolysis of hydrocarbon and oxygenated fuels. These studies consist in recording the evolution of the conversion of the reactants and of the mole fractions of reaction products as a function of different parameters such as reaction temperature, residence time, pressure and composition of the inlet gas. Gas chromatography is classically used for the analysis of the species in the gas phase, but recent studies aimed at coupling new types of analytical devices to a jet-stirred reactor to observe new types of species and to gain accuracy in the identification and the quantification of species. 8.1 Overview of the Jet-Stirred Reactor Gas phase kinetic studies are mostly performed using closed vessels, burners and continuous stirred-tank reactors. Among continuous stirred-tank reactors is the jet-stirred reactor. One of its major advantages relies on the efficient mixing of the gas phase which provides identical and homogeneous compositions of the outlet gas and of the gas inside the reactor. When operated at steady state and at constant residence time, temperature and pressure, this type of reactor is easily modelled by a very simple system of mass balances. Another advantage of this reactor is the possibility of being coupled with analytical techniques such as gas chromatography and mass spectrometry for the identification and the quantification of the species in the gas phase. One of the best ways to achieve the mixing of the gas phase is to use turbulent jets obtained from nozzles. Despite the strong pressure drop in the nozzles, this technique provides very intense internal recycle streams. The material used for the manufacturing of the reactor is of great importance. The use of metal is not recommended because of possible large wall effects and the use of Pyrex glass or fused silica is preferred. The jet-stirred reactor has often been used to study the gas phase oxidation and the thermal decomposition of fuels. These studies consist in measuring the evolution of the mole fractions of species at the outlet of the reactor as a function of different parameters such as reaction temperature, residence time, pressure and composition of the inlet gas (the fuel concentration and the equivalence ratio in combustion experiments). The reactivity of the fuel and the selectivity of the reaction products can be deduced from these data. The residence time of the gas in the reactor (Eq. 8.1) is actually a mean residence time (or space time) which is defined as the ratio of the volume of the reactor, , and of the volume flow rate of the gas flowing through the reactor, , which is also the volume flow rate at the outlet of the reactor, (Fig. 8.1). To verify that the reactor can be considered as a continuous stirred-tank reactor, one can measure the residence time distribution by doing a short injection of a very small amount of tracer at the inlet and by ...

Advances in rapid compression machine studies of low- and intermediate-temperature autoignition phenomena

“…Recent efforts have also targeted jet fuels. Chemical kinetic models are typically formulated based on data from a variety of sources, including rapid compression machines (RCMs) [39], motored or skip-fired engines [40], flow/jet reactors [41,42], and shock tubes [43].…”

“…Shock tubes are typically designed with consideration for minimizing boundary layer influences on the gas dynamics, while some have been extended to lower temperature operation and longer reaction times, e.g., ms [43,46], by careful tailoring of the mixture used in the driver section, and extension of the length of the driver section to minimize expansion wave and contact surface interactions with the test gas mixture (see [47] and references therein). A particular strength of shock tube studies remains higher temperature of 218 dilute mixture conditions, which are particularly well suited to studies of elementary chemical reactions and can be more straightforward to model without considering complex boundary conditions [48].…”

“…The relative simplicity, range of accessible pressure and temperature conditions and the ability to tailor and control the reactant composition have allowed data acquired from RCMs to reliably quantify the reactivity and reaction pathways of a large range of fuels, as well as provide valuable data for the development and validation of chemical kinetic mechanisms. Recent reviews by Kéromnès [63] and Sung and Curran [39] describe state-of-the-art techniques for applying RCMs in this manner. The current manuscript extends these works to additionally cover utilization for studying physical-chemical interactions, as well as detailed design considerations, diagnostic implementation and insight, and alternative approaches to modeling RCM processes.…”

“…The objective of this paper is to extend the recent reviews by Kéromnès [63], and Sung and Curran [39], and present a summary of important advances that have been achieved via rapid compression machines as experimental platforms towards improving the understanding, development and validation of models for low temperature combustion. Thanks to both historical and recent innovations, uncertainties associated with the reaction chemistry of the LTC regime have been substantially reduced.…”

Accidental Combustion Phenomena at Cryogenic Conditions

“…Sometimes, this notation can be preceded by aug, representing the augmented version of the indicated basis sets. Further information on the nomenclature and the theoretical principles founding quantum mechanics can be found elsewhere [28,36,37].…”