Showing papers on "Combustion published in 1997"

Engineering Fundamentals of the Internal Combustion Engine

Abstract: This book was written to be used as an applied thermoscience textbook in a onesemester, college-level, undergraduate engineering course on internal combustion engines. It provides the material needed for a basic understanding of the operation of internal combustion engines. Students are assumed to have knowledge of fundamental thermodynamics, heat transfer, and fluid mechanics as a prerequisite to get maximum benefit from the text. This book can also be used for self-study and/or as a reference book in the field of engine

Emissions from smoldering combustion of biomass measured by open-path Fourier transform infrared spectroscopy

Abstract: Biomass samples from a diverse range of ecosystems were burned in the Intermountain Fire Sciences Laboratory open combustion facility. Midinfrared spectra of the nascent emissions were acquired at several heights above the fires with a Fourier transform infrared spectrometer (FTIR) coupled to an open multipass cell. In this report, the results from smoldering combustion during 24 fires are presented including production of carbon dioxide, carbon monoxide, methane, ethene, ethyne, propene, formaldehyde, 2-hydroxyethanal, methanol, phenol, acetic acid, formic acid, ammonia, hydrogen cyanide, and carbonyl sulfide. These were the dominant products observed, and many have significant influence on atmospheric chemistry at the local, regional, and global scale. Included in these results are the first optical, in situ measurements of smoke composition from fires in grasses, hardwoods, and organic soils. About one half of the detected organic emissions arose from fuel pyrolysis which produces white smoke rich in oxygenated organic compounds. These compounds deserve more attention in the assessment of fire impacts on the atmosphere. The compound 2-hydroxyethanal is a significant component of the smoke, and it is reported here for the first time as a product of fires. Most of the observed alkane and ammonia production accompanied visible glowing combustion. NH3 is normally the major nitrogen-containing emission detected from smoldering combustion of biomass, but from some smoldering organic soils, HCN was dominant. Tar condensed on cool surfaces below the fires accounting for ∼1% of the biomass burned, but it was enriched in N by a factor of 6–7 over the parent material, and its possible role in postfire nutrient cycling should be further investigated.

Air-fuel ratio control system for internal combustion engines

Abstract: An air-fuel ratio control system for an internal combustion engine includes a LAF sensor and an O2 sensor arranged in an exhaust pipe at respective locations upstream and downstream of a catalytic converter. A desired air-fuel ratio coefficient used in calculating an amount of fuel supplied to the engine is calculated based on operating conditions of the engine, and corrected based on output from the O2 sensor. The air-fuel ratio of a mixture supplied to the engine is feedback-controlled to a stoichiometric air-fuel ratio based on the corrected desired air-fuel ratio coefficient. When the output from the O2 sensor falls within a predetermined range, the desired air-fuel ratio coefficient is not corrected, but held at an immediately preceding value thereof.

Heater well method and apparatus

Abstract: A method and apparatus is disclosed for heating of formations using fired heaters. Each fired heater may consist of two concentric tubulars emplaced in the formation, connected via a wellhead to a burner at the surface. Combustion gases from the burner go down to the bottom of the inner tubular and return to the surface in the annular space between the two tubulars. The two tubulars may be insulated in an overburden zone where heating is not desired. A plurality of fired heaters can be connected together such that the combustion gases from a first fired heater well are piped through insulated interconnect piping to become the air inlet for a second fired heater well, which also has a burner at its wellhead. This can be repeated for other heater wells, until the oxygen content of the combustion gas is reduced near zero. The combustion gas from the last fired heater well may be routed through a heat exchanger in which the fresh inlet air for the first heater well is preheated. A substantially uniform temperature is maintained in each heater well by using a high mass flow into the heater well.

Process for converting gas to liquids

Abstract: A process for converting a hydrocarbon gas (e.g. natural gas) to syngas which, in turn, is converted into a liquid hydrocarbon product wherein a substantial amount of the heat generated in the process is recovered for use in generating steam needed in the process or for conversion into mechanical energy. Further, tail gas produced by the process is used to fuel the gas turbine which, in turn, is used to power the compressor needed for compressing the air used in the process. By using tail gas to fuel the gas turbine, less of the compressed combustion-air is needed to cool the combustion gases in the turbine and, instead, can be used to provide a portion of the process-air required in the process; thereby possibly saving up to 20 to 30 percent of the horsepower otherwise needed to compress the required volume of the process-air.

Concentrations of inorganic elements in biomass fuels and recovery in the different ash fractions

Abstract: Inorganic elements and compounds in biomass fuels influence the combustion process and the composition of the ashes produced. Consequently, knowledge about the material fluxes of inorganic elements and compounds during biomass combustion for different kinds of biofuels and their influencing variables is of great importance. The results gained will especially influence the future design and control of biomass furnaces and boilers in order to prevent slagging, fouling and corrosion and to assist in the definition of quality requirements for biofuels as well as the possibilities of a sustainable ash utilization. For this reason, comprehensive test runs were carried out in several biomass combustion plants equipped with different combustion technologies and using various biomass fuels (wood chips, bark, straw and cereals). During continuous observation periods of at least two days, samples of the biomass and the different ash fractions were taken and analysed. Furthermore, the most important operating data of the plants were recorded. The results of the material balances for inorganic elements showed that the concentrations of environmentally relevant heavy metals (especially Cd and Zn) in biomass ashes increase with decreasing precipitation temperature and particle size. This effect is independent of the biofuel used. Consequently, a major requirement for a sustainable ash utilization is a fractionated heavy metal separation, distinguishing between different fly-ash fractions and taking the temperature of fly-ash precipitation into consideration for new furnace technologies. Research has also shown that straw and cereals, as well as their ashes, contain significantly lower amounts of heavy metals than woody biofuels and wood ashes. The same principles pointed out for environmentally relevant heavy metals are also valid for K, Na, Cl and S. The high concentrations of these elements in the filter fly-ash as well as in the boiler fly-ash are of great relevance for reactions that can take place in the boiler section where the flue gas is subjected to a considerable temperature gradient which is accompanied by chemical reactions, phase transitions and precipitation processes that can support or initiate fouling and corrosion. These effects are of special importance for biofuels that are rich in alkali metals and Cl such as straw and cereals.

Mercury from combustion sources: A review of the chemical species emitted and their transport in the atmosphere

Abstract: Different species of mercury have different physical/chemical properties and thus behave quite differently in air pollution control equipment and in the atmosphere. In general, emissions of mercury from coal combustion sources are approximately 20–50% elemental mercury (Hg°) and 50–80% divalent mercury (Hg(II)), which may be predominantly HgCl2. Emissions of mercury from waste incinerators are approximately 10–20% Hg° and 75–85% Hg(II). The partitioning of mercury in flue gas between the elemental and divalent forms may be dependent on the concentration of particulate carbon, HCl and other pollutants in the stack emissions. The emission of mercury from combustion facilities depends on the species in the exhaust stream and the type of air pollution control equipment used at the source. Air pollution control equipment for mercury removal at combustion facilities includes activated carbon injection, sodium sulfide infection and wet lime/limestone flue gas desulfurization.

Chapter 4 Mathematical tools for the construction, investigation and reduction of combustion mechanisms

Abstract: Publisher Summary Chemical mechanisms have been employed in hydrocarbon combustion as a means of understanding the underlying phenomenology of the combustion process in terms of the elementary reactions of individual species. This chapter provides an introduction to most of the mathematical methods that have been used for the construction, investigation, and reduction of combustion mechanisms. The use of algebraic manipulation in techniques, such as the quasi-steady-state approximation (QSSA) and lumping, make the production of a reduced mechanism essential and make subsequent calculations as simple as possible. Computational singular perturbation (CSP) is an alternative to the rate-of-production and sensitivity methods for mechanism reduction and provides an automatic selection of the important reactions as well as time-scale analysis. The simplest and most widely used technique involving the separation of time scales is the QSSA; however, a possible limitation is that it may not provide the minimum low-order system. Chemical lumping can prove very useful in areas, such as the combustion of hydrocarbon mixtures or soot formation. Several programs are available for the investigation and reduction of combustion mechanisms, including MECHMOD, a code for the automatic modification of CHEMKIN format combustion mechanisms, and KINALC, which is an almost automatic program for the investigation and reduction of gas-phase reaction mechanisms. KINALC is a postprocessor to CHEMKIN-based simulation packages SENKIN, PREMIX, OPPDIF, RUN1DL, PSR, SHOCK and EQLIB. Because models in combustion are expected to cover a wide range of conditions, it is natural to expect that a different approach might be used for different cases.

The Dilution, Chemical, and Thermal Effects of Exhaust Gas Recirculation on Disesel Engine Emissions - Part 4: Effects of Carbon Dioxide and Water Vapour

Abstract: This paper deals with the effects on diesel engine combustion and emissions of carbon dioxide and water vapour the two main constituents of EGR. It concludes the work covered in Parts 1, 2, and 3 of this series of papers. A comparison is presented of the different effects that each of these constituents has on combustion and emissions. The comparison showed that the dilution effect was the most significant one. Furthermore, the dilution effect for carbon dioxide is higher than that for water vapour because EGR has roughly twice as much carbon dioxide than water vapour. On the other hand, the water vapour had a higher thermal effect in comparison to that of carbon dioxide due to the higher specific heat capacity of water vapour. The chemical effect of carbon dioxide was, generally, higher than that of water vapour. The chemical effect of water vapour resulted in an increase in the particulate and carbon emissions, but, the chemical effect of carbon dioxide was to decrease these emissions. Similarly, opposite chemical effect were observed on the ignition delay. This is the fourth paper in a series which deals with the effects of EGR on combustion and emissions in diesel engines. The first, second and third papers are SAE 961165, SAE 961167, and SAE 971659 (to be published in 1997 by SAE), respectively. © 1997 Society of Automotive Engineers, Inc.

Determination of carbon and nitrogen in samples of various soils by the dry combustion

Abstract: Carbon and nitrogen (N) content of various soils in the world were analyzed using a CNS‐2000 (LECO, Corp., St. Joseph, MI) analyzer. The results were in good agreement with those obtained by a labo...

Thermally enhanced compact reformer

Abstract: A natural gas reformer (10) comprising a stack of thermally conducting plates (12) interspersed with catalyst plates (14) and provided with internal or external manifolds for reactants. The catalyst plate is in intimate thermal contact with the conducting plates so that its temperature closely tracks the temperature of the thermally conducting plate, which can be designed to attain a near isothermal state in-plane to the plate. One or more catalysts may be used, distributed along the flow direction, in-plane to the thermally conducting plate, in a variety of optional embodiments. The reformer may be operated as a steam reformer or as a partial oxidation reformer. When operated as a steam reformer, thermal energy for the (endothermic) steam reforming reaction is provided externally by radiation and/or conduction to the thermally conducting plates. This produces carbon monoxide, hydrogen, steam and carbon dioxide. When operated as a partial oxidation reformer, a fraction of the natural gas is oxidized assisted by the presence of a combustion catalyst and reforming catalyst. This produces carbon monoxide, hydrogen, steam and carbon dioxide. Because of the intimate thermal contact between the catalyst plate and the conducting plates, no excessive temperature can develop within the stack assembly. Details of the plate design may be varied to accommodate a variety of manifolding embodiments providing one or more inlets and exit ports for introducing, pre-heating and exhaust the reactants.

High Temperature Sensors Based on Metal–Insulator–Silicon Carbide Devices

Abstract: High temperature gas sensors based on catalytic metal-insulator-silicon carbide (MISiC) devices are developed both as capacitors and Schottky diodes. A maximum operation temperature of 1000 degrees C is obtained for capacitors based on 4H-SiC, and all sensors work routinely for several weeks at 600 degrees C. Reducing gases like hydrocarbons and hydrogen lower the flat band voltage of the capacitor and the barrier height of the diode. The time constants for the gas response are in the order of milliseconds and because of this good performance the sensors are tested for combustion engine control. For temperatures around 600 degrees C total combustion occurs on the sensor surface and the signal is high for fuel in excess and low for air in excess. At temperatures around 400 degrees C the response is more linear. The high temperature operation causes interdiffusion of the metal and insulator layers in these devices; and this interdiffusion has been studied. At sufficiently high temperatures the inversion capacitance shows different levels for hydrogen free and hydrogen containing ambients, which is suggested to be due to a reversible hydrogen annealing effect at the insulator-silicon carbide interface.

Method and apparatus for operation of combustion engines

Abstract: A heat engine system for optionally combining various embodiments selected from those based on fuel injection to induce denser air delivery to a combustion chamber, direct injection of fuel into a combustion chamber, stratified charge fuel combustion, utilization of variable degrees of excess air to control peak combustion temperature, regenerative conversion of kinetic energy into fuel value, positive ignition by spark discharge, catalytic ignition, heated surface ignition, turbocharging, turbogenerating, moisture recovery by exduction, electrolysis, thermochemical regeneration, and electrothermochemical regeneration.

Apparatus and method for reducing emissions in a dual combustion mode diesel engine

Abstract: A diesel engine is adapted to operate in a conventional diesel combustion mode within a first speed and load range, and in a homogeneous charge compression ignition mode in a second load and speed range. When operating in the homogeneous charge compression ignition mode, the emissions are dramatically reduced, resulting in a significant net reduction in emissions over the total load and speed operating range of the engine.