Showing papers on "Ignition system published in 1998"

An Introduction to Fire Dynamics

Abstract: Machine generated contents note: About the AuthorPreface to the Second EditionPreface to the Third EditionList of Symbols and Abbreviations1 Fire science and combustion 1.1 Fuels and the Combustion Process 1.2 The Physical Chemistry of Combustion in Fires Problems2 Heat transfer 2.1 Summary of the heat transfer equations 2.2 Conduction 2.3 Convection 2.4 Radiation Problems3 Limits of flammability and premixed flames 3.1 Limits of flammability 3.2 The structure of a premixed flame 3.3 Heat losses from premixed flames 3.4 Measurement of burning velocities 3.5 Variation of burning velocity with experimental parameters 3.6 The effect of turbulence Problems4 Diffusion flames and fire plumes 4.1 Laminar jet flames 4.2 Turbulent jet flames 4.3 Flames from natural fires 4.4 Some practical applications Problems5 Steady burning of liquids and solids 5.1 Burning of liquids 5.2 Burning of solids Problems6 Ignition: The initiation of flaming combustion 6.1 Ignition of^

Inertial Confinement Fusion: The Quest for Ignition and Energy Gain Using Indirect Drive

Abstract: ICF overview historical development of the indirect drive in the US ICF programme ignition physics pulse shaping implosion dynamics hydrodynamic instability, ignition threshold, and capsule gain hohlraum coupling efficiency hohlraum radiation uniformity combined tests of symmetry and hydrodynamic instability hohlraum plasma conditions hot electron preheat national ignition facility and ignition targets inertial fusion energy.

Supercharged Homogeneous Charge Compression Ignition

Abstract: The Homogeneous Charge Compression Ignition (HCCI) is the third alternative for combustion in the reciprocating engine. Here a homogeneous charge is used as in a spark-ignited engine, but the charge is compressed to autoignition as in a diesel. The main difference compared with the Spark Ignition (SI) engine is the lack of flame propagation and hence the independence from turbulence. Compared with the diesel engine, HCCI has a homogeneous charge and hence no problems associated with soot and NOdx formation. Earlier research on HCCI showed high efficiency and very low amounts of NOdx, but HC and CO were higher than in SI mode. It was not possible to achieve high IMEP values with HCCI, the limit being 5 bar. Supercharging is one way to dramatically increase IMEP. The influence of supercharging on HCCI was therefore experimentally investigated. Three different fuels were used during the experiments: iso-octane, ethanol and natural gas. Two different compression ratios were used, 17:1 and 19:1. The inlet pressure conditions were set to give 0, 1, or 2 bar of boost pressure. The highest attainable IMEP was 14 bar using natural gas as fuel at the lower compression ratio. The limit in achieving even higher IMEP was set by the high rate of combustion and a high peak pressure. Numerical calculations of the HCCI process have been performed for natural gas as fuel. The calculated ignition timings agreed well with the experimental findings. The numerical solution is, however, very sensitive to the composition of the natural gas. (Less)

Hot electron production and heating by hot electrons in fast ignitor research

Abstract: In an experimental study of the physics of fast ignition the characteristics of the hot electron source at laser intensities up to 10(to the 20th power) Wcm{sup -2} and the heating produced at depth by hot electrons have been measured. Efficient generation of hot electrons but less than the anticipated heating have been observed.

Combustors for micro-gas turbine engines

Abstract: The development ofa hydrogen-air microcombustor is described. The combustor is intended for use in a 1 mm 2 inlet area, micro-gas turbine engine. While the size of the device poses several difficulties, it also provides new and unique opportunities. The combustion concept investigated is based upon introducing hydrogen and premixing it with air upstream of the combustor. The wide flammability limits of hydrogen-air mixtures and the use of refractory ceramics enable combustion at lean conditions, obviating the need for both a combustor dilution zone and combustor wall cooling. The entire combustion process is carried out at temperatures below the limitations set by material properties, resulting in a significant reduction of complexity when compared to larger-scale gas turbine combustors. A feasibility study with initial design analyses is presented, followed by experimental results from 0.13 cm 3 silicon carbide and steel microcombustors. The combustors were operated for tens of hours, and produced the requisite heat release for a microengine application over a range of fuel-air ratios, inlet temperatures, and pressures up to four atmospheres. Issues of flame stability, heat transfer, ignition and mixing are addressed. A discussion of requirements for catalytic processes for hydrocarbon fuels is also presented.

Compression ignition type engine

Abstract: A compression ignition type engine, wherein a first combustion where the amount of the recirculated exhaust gas supplied to the combustion chamber is larger than the amount of recirculated exhaust gas where the amount of production of soot peaks and almost no soot is produced and a second combustion where the amount of recirculated exhaust gas supplied to the combustion chamber is smaller than the amount of recirculated exhaust gas where the amount of production of soot peaks are selectively switched between and where the second combustion is switched to the first combustion when the temperature of the catalyst arranged in an engine exhaust passage is about to fall below the activation temperature.

The oxidation and ignition of dimethylether from low to high temperature (500–1600 K): Experiments and kinetic modeling

Abstract: The oxidation of dimethylether (DME) has been studied in a fused silica jet-stirred reactor (JSR) at 10 atm, 0.2≤φ≤1, 550–1100 K. Concentration profiles of reactants, intermediates, and products of the oxidation were measured by low-pressure sonic probe sampling and off-line gas chromatography analyses. The results obtained in the cool flame regime are the first to be reported. The ignition delays of DME/O2/Ar mixtures have been measured in a shock tube at 1200 to 1600 K, at 3.5 atm and 0.5≤φ≤2. A numerical model consisting of a detailed kinetic reaction mechanism with 331 reactions (most of them reversible) among 55 species is proposed to describe both the low and high-temperature oxidation of DME in the JSR (550–1275 K, 1–10 atm) and the ignition of DME in shock tubes from low to high temperature (650–1600 K, 3.5–40 bar). A general good agreement between the data and the model was observed. A kinetic analysis involving sensitivity and reaction path analysis is used to interpret the results.

Handbook of Air Pollution from Internal Combustion Engines: Pollutant Formation and Control

Abstract: Overview: J.B. Heywood, Motor Vehicle Emissions Control: Past Achievements, Future Prospects. Global Aspects: E. Sher, Environmental Aspects of Air Pollution. R. Carel, Health Aspects of Air Pollution. P.O. Plaut and S.E. Plaut, Economic and Planning Aspects of Transportation Emission. Spark-Ignition Engines: R. Stone, Introductory Chapter: Overview and the Role of Engines with Optical Access. S. Hochgreb, Combustion RelatedEmissions in Engines. M. Dulger, Pollution from Rotary Internal Combustion Engines. B.E. Milton, Control Technologies in Spark Ignition Engines. Compression-Ignition Engines: F. Pischinger, Introductory Chapter: The Diesel Enginefor Cars--Is There a Future? J.G. Hawley, C.J. Brace, F.J.Wallace, and R.W Horrocks, Combustion Related Emissions in Engines. S.J. Charlton, Control Technologies in Compression Ignition Engines. Two-Stroke Engines: C.C. Stan, Introductory Chapter: From a Simple Engine to an Electronically-Controlled Gasdynamic System. Y. Ikeda, T. Nakjima, and E. Sher, Air-Pollution from Small Two-Stroke Engines and Technologies to Control It. S. Henningsen, Air-Pollution from Large Two-Stroke Diesel Engines and Technologies to Control It. Fuels: D.R. Blackmore, Introductory Chapter: Fuel Effects. Y. Zvirin, M. Gutman, and L. Tartakovsky, Fuel Effects on Emissions. References. Appendices: National Gasoline Specifications. National Specifications for Automotive Diesel Fuel. US EPA Models for Calculation of Fuel Effects on Exhaust Emissions.

A constitutive model for the non-shock ignition and mechanical response of high explosives

Abstract: An understanding of the non-shock ignition properties of energetic particulate composite materials, high explosives such as PBX-9501 is an important part of the safety assessments for conventional handling (transportation, storage, etc.) of weapons systems including assembly operations. This paper develops and demonstrates the use of a numerical constitutive model for PBX-9501 that includes viscoelastic response, statistical fracture mechanics, and an ignition hot-spot mechanism. The intent is that this model can be used in safety analyses involving accidents to prevent undesirable dispersion of Pu. The parameters have been determined that will predict the mechanical response and ignition:non-ignition of a set of experiments that have explored the non-shock properties of this material.

Lasers in combustion: From basic theory to practical devices

Abstract: In recent years, a large number of linear and nonlinear laser-based diagnostic techniques for nonintrusive measurements of species concentrations, temperatures, and gas velocities in a wide pressure and temperature range with high temporal and spatial resolution were developed and have become extremely valuable tools to study many aspects of combustion. Modern “pump-probe” laser spectroscopic methods give direct insight into the microscopic dynamics, product channel distributions, and reaction rates of elementary combustion reactions over a wide range of temperatures and pressures. Nonlinear laser spectroscopic techniques using infrared-visible sum-frequency generation can now bridge the pressure and materials gap to provide kinetic data for catalytic combustion. Laminar flames are ideal objects to develop the application of laser spectroscopic methods for practical combustion systems and to test and improve gas-phase reaction mechanism in combustion models. Besides diagnostics, lasers can also provide well-defined starting conditions for detailed experimental and theoretical studies of ignition processes. Non-intrusive laser point and field measurements, especially joint velocity-scalar data at the same point in space and time, are of basic importance in the validation and further development of turbulent combustion models. As an are for the application of quanitative laser spectroscopy to practical combustion devices, investigations in internal combustion engines are described. Finally, the potential of laser techniques for active combustion control in various devices from laboratory burners to full-scale jet engines, municipal waste incinerators, and pressurized fluidized-bed reactors are illustrated.

Direct fuel injection engine

Abstract: A direct injection engine including an injector disposed in an upper portion of a combustion chamber defined above a piston disposed in a cylinder of the engine with a fuel injecting direction of the injector being provided so that a fuel being injected toward a top portion of the piston, an ignition plug disposed at an upper portion of the combustion chamber, an engine operating condition detector for detecting an engine operating condition The fuel is injected in a compression stroke from the injector when it is detected by the engine operating condition detector that the engine is in a low engine load and speed zone so as to stratify an injected air fuel mixture around the ignition plug to accomplish a stratified combustion The engine further includes a fuel controller for controlling an fuel injection so as to inject the fuel plural times into the combustion chamber in a compression stroke when at least one of an engine load and an engine speed is relatively high in an engine operating zone for accomplishing the stratified combustion A stable combustion is accomplished to improve the fuel consumption efficiency

A comparison of three-dimensional multimode hydrodynamic instability growth on various National Ignition Facility capsule designs with HYDRA simulations

Abstract: Three similar cryogenic ignition capsule designs for the National Ignition Facility [J. Lindl, Phys. Plasmas 2, 3933 (1995)] are analyzed to determine surface roughness specifications required to mitigate the growth of hydrodynamic instabilities. These capsule utilize brominated plastic, polyimid and copper-doped beryllium ablator materials respectively. Direct three-dimensional numerical simulations with the HYDRA radiation hydrodynamic code [M. M. Marinak et al., Phys. Plasmas 3, 2070 (1996)] examine the growth of multimode perturbations seeded by roughness on the outer ablator and inner ice surfaces. The simulations, which showed weakly nonlinear behavior for optimized surfaces, were carried through ignition and burn. A three-dimensional multimode perturbation achieves somewhat larger amplitudes in the nonlinear regime than a corresponding two-dimensional simulation of the same rms amplitude. The beryllium and polyimid capsules exhibit enhanced tolerance of roughness on both the ice and ablator surfaces.

Ignition of hydrogen-air mixing layer in turbulent flows

Abstract: Autoignition of a hydrogen-air scalar mixing layer in homogeneous turbulence is studied using direct numerical simulation (DNS). An initial counterflow of unmixed nitrogen-diluted hydrogen and heated air is perturbed by two-dimensional homogeneous turbulence. The temperature of the heated airstream is chosen to be 1100 K, which is substantially higher than the crossover temperature at which the rates of the chain-branching and termination reactions are equal. Three different turbulence intensities are tested in order to assess the effect of the characteristic flow time on the ignition delay. For each condition, a simulation without heat release is also performed. The ignition delay determined with and without heat release is shown to be almost identical up to the point of ignition for all of the turbulence intensities tested, and the predicted ignition delays agree well within a consistent error band. It is also observed that the ignition kernel always occurs where hydrogen is focused, and the peak concentration of HO2 is aligned well with the scalar dissipation rate. The dependence of the ignition delay on turbulence intensity is found to be nonmonotonic. For weak to moderate turbulence, the ignition is facilitated by turbulence via enhanced mixing, while for stronger turbulence, whose timescale is substantially smaller than the ignition delay, the ignition is retarded due to excessive scalar dissipation, and hence diffusive loss, at the ignition location. However, for the wide range of initial turbulence fields studied, the variation in ignition delay due to the corresponding variation in turbulence intensity appears to be quite small.

Compression ratio effect on methane HCCI combustion

Abstract: We have used the HCT (Hydrodynamics, Chemistry and Transport) chemical kinetics code to simulate HCCI (homogeneous charge compression ignition) combustion of methane-air mixtures. HCT is applied to explore the ignition timing, bum duration, NO x production, gross indicated efficiency and gross IMEP of a supercharged engine (3 atm. Intake pressure) with 14:1, 16:l and 18:1 compression ratios at 1200 rpm. HCT has been modified to incorporate the effect of heat transfer and to calculate the temperature that results from mixing the recycled exhaust with the fresh mixture. This study uses a single control volume reaction zone that varies as a function of crank angle. The ignition process is controlled by adjusting the intake equivalence ratio and the residual gas trapping (RGT). RGT is internal exhaust gas recirculation which recycles both thermal energy and combustion product species. Adjustment of equivalence ratio and RGT is accomplished by varying the timing of the exhaust valve closure in either 2-stroke or 4-stroke engines. Inlet manifold temperature is held constant at 300 K. Results show that, for each compression ratio, there is a range of operational conditions that show promise of achieving the control necessary to vary power output while keeping indicated efficiency above 50% and NO x levels below 100 ppm. HCT results are also compared with a set of recent experimental data for natural gas.

Control system for two cycle direct injection engine and the method thereof

Abstract: Disclosed is a control system and method of a two cycle direct fuel injection engine capable of smoothly suspending combustions in the cylinder during light load operation of the engine. Based on a map parameterizing the engine speed and the target engine load, it is judged whether or not, when the engine load is in the light load condition, the target engine load is located in a suspending area in which misfires tend to occur. If the target engine load is not in the suspending area, since there is no possibility of misfire, the normal combustion cycle continues to operate. On the other hand, if the target engine load enters into the suspending area, the control system instructs the fuel injection and ignition apparatuses so as to suspend fuel injection and spark ignition with a frequency determined according to the magnitude of the engine load. The frequency is determined by a predetermined formula such that it is reduced as the engine load becomes high and is increased as the engine load becomes low.

Ignition of fires

Abstract: This paper discusses the mechanisms that lead to ignition of fires and the reasons behind the experimental correlations available in the literature. The objective is to understand and quantify the ...

A Numerical Study of Lean CH4/H2/Air Premixed Flames at High Pressure

Abstract: We perform a numerical study of the effect of including a small amount of hydrogen in lean methane-air premixed flames at high pressure and high temperature conditions. It has been shown recently (Bell and Gupta (1997)) that hydrogen addition extends the lean operating limit of natural gas engines, leading to a potential decrease in pollutant formation. We suggest here that the origin of this effect is that, at constant global equivalence ratio, the stretch resistance of these flames is considerably increased by hydrogen blending, while other flame properties, such as ignition time and burnt gas temperature, are comparatively little modified.

Homogeneous ignition of methane-air mixtures over platinum: Comparison of measurements and detailed numerical predictions

Abstract: The homogeneous ignition of lean methane-air mixtures was investigated numerically and experimentally in a laminar plane channel flow configuration established by two externally heated catalytically active (Pt-coated) ceramic plates, 250 mm long by 100 mm wide, place 7 mm apart. Preheated fuel-air mixtures with equivalence ratios of 0.31 and 0.37 and uniform velocities of 1 and 2 m/s were examined, resulting in incoming Reynolds numbers ranging from 190 to 380. Planar laser-induced fluorescence (PLIF) was used to map the OH concentration field along the streamwise direction and thermocouples to monitor both catalyst plate temperatures. The numerical predictions included a two-dimensional elliptic model with detailed heterogeneous and homogeneous chemical reactions. The homogeneous ignition location strongly depends on the incoming velocity and mildly on the equivalence ratio. Following homogeneous ignition, a very stable V-shaped flame is formed in all cases. Measured and predicted flame sweep angles, OH levels, and the post-flame OH relaxation are in good agreement with each other, while the homogeneous ignition distance is predicted within 9% in all cases. The homogeneous ignition location is shown to be better identified with changes of averaged (over the channel cross section) quantities rather than with changes in local wall gradients. The overall model performance suggests that the employed surface scheme is capable of capturing the coupling between surface and gaseous chemistries leading to homogeneous ignition. Experiments and predictions were also carried out with noncatalytic plates. The resulting flame is unstable and asymmetric, clearly showing the stability advantages of catalytically assisted combustion.

Air-to-fuel ratio control of spark ignition engines using Gaussian network sliding control

Abstract: This paper treats air-to-fuel ratio control of a spark ignition engine. A direct adaptive control method using Gaussian neural networks is developed to compensate transient fueling dynamics and the measurement bias of mass air flow rate into the manifold. The transient fueling compensation method is coupled with a dynamic sliding mode control technique that governs fueling rate when the throttle change is not rapid. The proposed controller is simple enough for online computation and is successfully implemented on an automotive engine having a multiport fuel injection system.

Hand-held ignition voltage tester

Abstract: A hand-held ignition voltage tester for detecting voltage on a spark plug wire in an ignition system, such as a distributorless ignition system. The tester includes a housing, positive and negative power cables and a capacitive probe for capacitively coupling to the spark plug wire. The capacitive probe generates a voltage signal which is representative of the voltage on the spark plug wire. A plurality of voltage level indicators are mounted to the housing to form a bar graph, with each indicator corresponding to a selected voltage level. A measurement circuit is coupled to the power cables and the capacitive probe for activating the voltage level indicators in response to the voltage signal.