The role of NO2 and NO in the mechanism of hydrocarbon degradation leading to carbonaceous deposits in engines (original) (raw)
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Combustion and flame, 1999
Postflame injection of fuel has been proposed as a means of reducing chlorinated hydrocarbons (CHCs) in a combustion exhaust. In this study, the effects of this strategy on CHCs and NO x are investigated. A small amount of fuel, such as CO or CH 3 OH, has been injected into the postflame region from a turbulent combustion-driven flow reactor to assess its effect on the destruction of two CHCs (CH 3 Cl and C 2 H 5 Cl) and simultaneously, the oxidation of NO to NO 2. The results suggest that this strategy is effective only in certain conditions. There is an optimal temperature ϳ 1050 K, where NO is most effectively converted to NO 2. Adding fuel to the postflame region increases the concentrations of both HO 2 and OH radicals, but temperature is the key factor in determining which radical will dominate the reaction pathway. For the destruction of CHCs, attack by OH is the major destruction route, with T Ͼ 1200 K desired. For NO oxidation, the HO 2 radical is the key species, and lower temperatures are necessary.
International Journal of Low-Carbon Technologies
This research aims to study the effect of various blends of an alternative fuel environment (ethanol, isooctane) on the performance of a spark ignition gasoline engine. The blends were obtained from two additives: ethanol and isooctane. The tests were carried out on an engine test bench following DIN 70020. The results show that the petrol additives achieve excellent ecological results. On the other hand, the engine performance was slightly reduced compared with that obtained with pure fuel. We noted a variation in engine performance for the E10 (10% ethanol + 90% pure petrol) and I10 (10% isooctane + 90% pure petrol) blends, namely a reduction in nitrogen oxides (NOx) emissions of 7.5% for E10 and 5% for I10 compared with pure petrol. However, using E10 and I10 blends did not increase the specific fuel consumption. Thus, the increase in the octane rating resulted in a decrease in NOx emissions. The use of 96 octane fuels, which corresponds to I40 (40% isooctane + 60% petrol), is ex...
Effects of active species induced by injected NO on the reduction of diesel NOx emission
Mechanical Engineering Letters, 2016
This study numerically investigates mechanisms of NO x reduction when pure NO is injected into a diesel engine intake. In a previous experiment, emissions were reduced successfully with NO concentrations above 600 ppm at the intake. However, the NO x suppression was significantly smaller when premixed NO concentrations were 600 ppm or below. To explain these observations, the contributions of active species O, OH, H, and N to the production of thermal NO were estimated numerically. First, the equilibrium concentrations of CO 2 , CO, H 2 O, H 2 , O 2 , O, OH, H, and N 2 in flames with various equivalence ratios were calculated. The concentrations of quasi-steady-state N and the NO production rate were then calculated based on the active species concentrations. The analysis shows that the reduced NO suppression at lower premixed NO concentration is primarily due to the role of N changing from production to decomposition of NO in fuel-rich regions when the NO concentration exceeds around 1200 ppm.
Journal of Physical Chemistry A, 2007
Relative rate techniques were used to study the kinetics of the reactions of Cl atoms and OH radicals with ethylene glycol diacetate, CH 3 C(O)O(CH 2) 2 OC(O)CH 3 , in 700 Torr of N 2 /O 2 diluent at 296 K. The rate constants measured were k(Cl + CH 3 C(O)O(CH 2) 2 OC(O)CH 3)) (5.7 (1.1) × 10-12 and k(OH + CH 3 C(O)O(CH 2) 2 OC(O)CH 3)) (2.36 (0.34) × 10-12 cm 3 molecule-1 s-1. Product studies of the Cl atom initiated oxidation of ethylene glycol diacetate in the absence of NO in 700 Torr of O 2 /N 2 diluent at 296 K show the primary products to be CH 3 C(O)OC(O)CH 2 OC(O)CH 3 , CH 3 C(O)OC(O)H, and CH 3 C(O)OH. Product studies of the Cl atom initiated oxidation of ethylene glycol diacetate in the presence of NO in 700 Torr of O 2 /N 2 diluent at 296 K show the primary products to be CH 3 C(O)OC(O)H and CH 3 C(O)OH. The CH 3 C-(O)OCH 2 O• radical is formed during the Cl atom initiated oxidation of ethylene glycol diacetate, and two loss mechanisms were identified: reaction with O 2 to give CH 3 C(O)OC(O)H and R-ester rearrangement to give CH 3 C(O)OH and HC(O) radicals. The reaction of CH 3 C(O)OCH 2 O 2 • with NO gives chemically activated CH 3 C(O)OCH 2 O• radicals which are more likely to undergo decomposition via the R-ester rearrangement than CH 3 C(O)OCH 2 O• radicals produced in the peroxy radical self-reaction.
USE OF FUEL-BORNE REDUCTANTS FOR NOx REDUCTION IN DIESEL ENGINE
Journal of KONES, 2001
The method used by the authors involves reduction of nitrogen oxides by means of chemically active hydrocarbons (radicals) from the fuel. In order to obtain partially oxidized and thermally decomposed hydrocarbons, the post-injection of fuel (the injection of an additional portion of fuel) into the diesel engine cylinder during the expansion stroke was implemented. To perform this function, a special fuel supply system consisting of two injection pumps was designed. One of the pumps was injecting the main (primary) fuel dose, and the other one - the additional fuel dose. Injection of both fuel doses was accomplished by the same injector. A catalytic converter was used in the exhaust system of the one-cylinder test engine. During the tests, the fuel post-injection angle (relative to the TDC) was changed. It was found that using that method of the reducing agent dosage, the total effect of nitrogen oxide reduction was a combination of the effects obtained in the engine cylinder by Sel...
New experimental results were obtained for the oxidation of a mixture of 85% of iso-octane and 15% of n-heptane in presence and absence of NO or NO2 in a fused silica jet-stirred reactor operating at 10 atm, lean conditions and over the temperature range 550-1000 K. Concentration profiles of reactants, intermediates and final products were measured and used to validate a detailed kinetic mechanism. The increased production of OH resulting from the oxidation of NO by HO2 promotes the oxidation of the fuel in the negative temperature coefficient region but can also inhibit the cool flame region with an increasing NOx concentration or equivalence ratio.
Oxidation of Alkane Rich Gasoline Fuels and their Surrogates in a Motored Engine
2015
The validation of surrogates formulated using a computational framework by Ahmed et al.[1] for two purely paraffinic gasoline fuels labelled FACE A and FACE C was undertaken in this study. The ability of these surrogate mixtures to be used in modelling LTC engines was accessed by comparison of their low temperature oxidation chemistry with that of the respective parent fuel as well as a PRF based on RON. This was done by testing the surrogate mixtures in a modified Cooperative Fuels Research (CFR) engine running in Controlled Autoignition Mode (CAI) mode. The engine was run at a constant speed of 600 rpm at an equivalence ratio of 0.5 with the intake temperature at 150 °C and a pressure of 98 kPa. The low temperature reactivity of the fuels were studied by varying the compression ratio of the engine from the point were very only small low temperature heat release was observed to a point beyond which autoignition of the fuel/air mixture occurred. The apparent heat release rates of di...
Electrical Engineering in Japan, 2013
The effect of injecting NO (major content of NO x in diesel exhaust gas) into a diesel engine intake, on the reduction of NO x generation at the combustion chamber was investigated. The results demonstrate that 20 to 30% of the injected NO [0.225 to 0.72 slm (slm: standard liter per minute)] is reduced. A discussion of the NO x reduction based on the extended Zeldovich mechanism suggests that the reduction is mainly attributable to the region where the equivalence ratio ranges from 1.1 to 1.5 and that the reaction between NO and hydrocarbon species contributes slightly to the NO reduction. Further experimental data show that the injection of NO slightly improves the specific fuel consumption; for example, a 0.4% reduction is achieved when NO is injected at 0.72 slm for an intake airflow of 285 slm. The experimentally determined change in fuel consumption is highly consistent with the calculations based on the reaction enthalpy of NO reduction and CO oxidation.
The Journal of Physical Chemistry, 1994
The yields of NO2 and oxirane have been studied as a function of pressure in the reactions of NO3 with selected unsaturated hydrocarbons. NO2 yields were detennined using a flow system with double resonance REMPI-MS technique in the range 1-30 mbar, argon being the buffer gas. The yields of oxiranes were studied using in situ FTIR technique in a static system in the pressure range 30-1000 mbar. With styrene, oxirane formation was also determined by REMPI-MS. The experiments revealed that the NO2 yields decreased strongly with pressure in the case of aliphatic dienes and styrene, whereas only a negligible pressure dependence of NO2 formation was observed with alkenes or cyclic dienes. These results were confirmed for 2,3-dimethyl-2-butene and for isoprene in the FTIR experiments in which the corresponding oxirane yields were measured at up to 1000 mbar of argon. Air as buffer gas reduced oxirane formation. In the reaction of cis-2-butene and trans-2-butene with NO3 similar yields of trans-2,3-dimethyloxirane were obtained. This finding is taken as the most direct evidence for the NO3 radical addition to the carbon double bond in alkenes in the primary reaction step in agreement with previous assumptions.