Exhaust oxygen

Recent emission control system development in the automotive industry has been directed mainly towards the use of three-way or dual bed catalytic converters, This type of converter system not only oxidizes the hydrocarbons (HC) and carbon monoxide (CO) in the exhaust gas but will also reduce the nitrous oxides (NO ). An integral part of this type of system is the exhaust oxygen sensor which is used to provide feedback for closed loop control of the air-fuel ratio. This is necessary since this type of catalytic converter system operates efficiently only when the composition of the exhaust gas is very near the stoichiometric point. 

Wang, D.Y. and Detwiler, E. (2006) Exhaust oxygen sensor dynamic study. Sens. Actuators B. 120, 200-6. 

In order to provide the proper stoichiometrically balanced exhaust gas composition required for use of the three-way catalyst, an air/fuel ratio control system had to be developed for the vehicle. Closed-loop electronic air-fuel ratio control required the installation of an exhaust oxygen sensor and an on-board microprocessor to provide the necessary control capability. 

Chen, S. K. Yanakiev, O. (2005). Transient NOx emissions reduction using exhaust oxygen concentration based control for a diesel engine, SAE. No. 2005-01-0372. 

Two catalytic converters may be used with the engine operating in a rich mode. The first catalyst reduces nitrogen oxides in an oxygen deficient exhaust. Oxygen can then be added to the exhaust to remove caibon monoxide and hydrocarbons with an oxidation catalyst in the second container. 

A similar set of equations may be applied for the cathode exhaust. Oxygen flow rate at the outlet, that is, unused oxygen, is equal to oxygen supplied at the inlet minus oxygen consumed in the fuel electrochemical reaction ... 

The oxygen used in the combustion is supplied by a small cylinder (120 Atm.) fitted with a pressure reduction valve, pressure gauge (to avoid the risk of the cylinder becoming exhausted during an actual determination) and fine control knob. It is important that the valve is kept free from oil or grease of any kind. In order to ensure the complete purity of the oxygen it is first passed through a purification train. 

Environmental Aspects. Airborne particulate matter (187) and aerosol (188) samples from around the world have been found to contain a variety of organic monocarboxyhc and dicarboxyhc acids, including adipic acid. Traces of the acid found ia southern California air were related both to automobile exhaust emission (189) and, iadirecfly, to cyclohexene as a secondary aerosol precursor (via ozonolysis) (190). Dibasic acids (eg, succinic acid) have been found even ia such unlikely sources as the Murchison meteorite (191). PubHc health standards for adipic acid contamination of reservoir waters were evaluated with respect to toxicity, odor, taste, transparency, foam, and other criteria (192). BiodegradabiUty of adipic acid solutions was also evaluated with respect to BOD/theoretical oxygen demand ratio, rate, lag time, and other factors (193). 

Vehicle Emissions. Gasohol has some automotive exhaust emissions benefits because adding oxygen to a fuel leans out the fuel mixture, producing less carbon monoxide [630-08-2] (CO). This is tme both for carbureted vehicles and for those having electronic fuel injection. 

Oxidizers. The characteristics of the oxidizer affect the baUistic and mechanical properties of a composite propellant as well as the processibihty. Oxidizers are selected to provide the best combination of available oxygen, high density, low heat of formation, and maximum gas volume in reaction with binders. Increases in oxidizer content increase the density, the adiabatic flame temperature, and the specific impulse of a propellant up to a maximum. The most commonly used inorganic oxidizer in both composite and nitroceUulose-based rocket propellant is ammonium perchlorate. The primary combustion products of an ammonium perchlorate propellant and a polymeric binder containing C, H, and O are CO2, H2, O2, and HCl. Ammonium nitrate has been used in slow burning propellants, and where a smokeless exhaust is requited. Nitramines such as RDX and HMX have also been used where maximum energy is essential. 

The Ohio State University (OSU) calorimeter (12) differs from the Cone calorimeter ia that it is a tme adiabatic instmment which measures heat released dufing burning of polymers by measurement of the temperature of the exhaust gases. This test has been adopted by the Federal Aeronautics Administration (FAA) to test total and peak heat release of materials used ia the iateriors of commercial aircraft. The other principal heat release test ia use is the Factory Mutual flammabiHty apparatus (13,14). Unlike the Cone or OSU calorimeters this test allows the measurement of flame spread as weU as heat release and smoke. A unique feature is that it uses oxygen concentrations higher than ambient to simulate back radiation from the flames of a large-scale fire. 

In 1957, Ethyl Corp. announced anew antiknock compound, methylcyclopentadienyknanganese tricarbonyl [12108-13-3] (MMT). MMT is almost as effective as lead on a per gram of metal basis, but because manganese was more expensive than lead, MMT was not widely used until limits were placed on the lead content of gasoline. MMT was used in unleaded fuel between 1975 and 1978. After a large fleet test suggested that MMT could increase exhaust emissions because it interfered with catalysts and oxygen sensors, EPA banned its use in unleaded fuel in 1978. MMT is used in Canada in unleaded fuel. 

NMOG = nonmethane organic gases, ie, the total mass of exhaust hydrocarbon and oxygenated compounds, excluding methane. 

Black nickel oxide is used as an oxygen donor in three-way catalysts containing rhodium, platinum, and palladium (143). Three-way catalysts, used in automobiles, oxidize hydrocarbons and CO, and reduce NO The donor quaUty, ie, the abiUty to provide oxygen for the oxidation, results from the capabihty of nickel oxide to chemisorb oxygen (see Exhaust control, automotive). 

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