Showing papers on "Ignition system published in 1991"

Piloted ignition of wood: A review

Abstract: The physical phenomenon of piloted ignition of a material is described A number of mathematical models of this phenomenon are presented in order of decreasing complexity The most sophisticated models include gas-phase phenomena Simple models neglect all chemical effects and are purely thermal The most commonly used criteria for piloted ignition are discussed Correlations used in piloted ignition studies from the past 40–50 years are summarized Many investigators have been successful in correlating piloted ignition data of wood using a simplified thermal model in combination with a critical surface temperature criterion Emphasis of this review is therefore on this approach The paper concludes with a detailed analysis of various factors affecting piloted ignition of wood Some of the factors are related to the experimental conditions, others are associated with the characteristics of the material

Expansion of laser-generated plumes near the plasma ignition threshold

Abstract: Expansion of laser-produced plumes on a solid-vacuum in’ terface during and after the laser shot was investigated theoretically, incorporating several new features into our previous one-component one-dimensional hydrodynamic model. Time development of density, velocity, temperature, and pressure profiles was calculated at laser irradiances below and above the plasma ignition threshold. The estimated velocity of ions released from the plume was close to the measured values. The fast spreading of the blow-off material under the laser vaporization regime and the long lifetime of the relatively compact plasma core above the ignition threshold were predicted in agreement with experimental observations. Cakulated surface recession due to evaporation provided a Jower bound to the measured crater depth, whereas the calculated melt depth proved to be a realistic upper limit.

High-temperature oxidation of ethanol. Part 2.—Kinetic modelling

Abstract: The high-temperature oxidation of ethanol has been modelled in a 97-step, 30 species reaction mechanism and the results of the calculations compared with recent measurements of the ignition delays of mixtures of ethanol, oxygen and argon behind reflected shock waves in the temperature range 1080–1660 K, at pressures of 1.8–4.6 bar and with equivalence ratios of 0.25–2.

Special purpose blends of hydrogen and natural gas

Abstract: An alternative fuel for use in internal combustion engines is disclosed. The fuel comprises a first component, predominated by lower alkanes, such as natural gas, and hydrogen as a second component. The proportion of the mixture is selected to produce a combustion rate which approximately matches the combustion rate of traditional fuels, such as petroleum-based fuels. The fuel of the invention is inexpensive and clean burning and increases the thermal efficiency of internal combustion engines. It can be substituted for or burned interchangeably with conventional fuels in spark ignition internal combustion engines. It can also be burned in conjunction with diesel fuel in compression ignition engines.

Low nox combustion

Abstract: A burner for a gas turbine combustor has a perforated plate facing the combustor and a plurality of gaseous fuel premixing tubes conveying a lean premixed fuel through the plate. A gas pilot extending through the plate projects jets of fuel parallel to the plate between the tube locations nearest the pilot. Ignition stability at turndown is maintained.

Ignition and Combustion of Boron Particles in the Flowfield of a Solid Fuel Ramjet

Abstract: Theoretical investigation on the behavior of individual boron particles in the flowfield of a solid fuel ramjet (SFRJ) combustor is presented. The study was motivated by the observed difficulties in achieving good combustion efficiencies of boron required to exploit its remarkable theoretical energetic performance. The equations describing the gas flowfield and the particle behavior are solved numerically. The solution presents the trajectory, temperature, and history of the boron particles due to the interactions with the surrounding gas, as well as the ignition envelope and combustion time. The results demonstrate the limited ranges of particle size and ejection velocity which enable ignition and sustained combustion, reveal why practical systems often exhibit poor combustion efficiencies, and predict the conditions where ignition and efficient combustion of boron are feasible. Nomenclature

Ignition apparatus for an internal combustion engine

Abstract: An LCDI-type ignition apparatus for an internal combustion engine includes first and second capacitors connected to an ignition coil and a voltage source for generating a charging voltage for the capacitors. The first capacitor is for producing an initial discharge of a spark plug, and the second capacitor is for lengthening the discharge of the spark plug after discharge has been initiated by the first capacitor. In one form of the invention, the second capacitor is charged only after the first capacitor has been charged by the voltage source to a prescribed voltage sufficient to produce a suitable discharge of the spark plug. As a result, even when the engine is operating at a high rotational speed and the time between consecutive firings of the engine is small, an adequate ignition voltage can be obtained. In another form of the invention, the charging voltage(s) of one or both of the capacitors is or are varied in accordance with the one or more engine operating conditions. Each charging voltage can be controlled to the minimum necessary value based on the present engine operating conditions.

Effect Of Environmental Variables On Piloted Lgnition

Abstract: In this paper the effect of environmental variables on piloted ignition of wood is investigated both experimentally and theoretically. The environmental variables considered are the moisture content of the solid, wind speed and its oxygen concentration and external radiation. Simultaneous measurements of weight loss rate, ignition time, sample surface temperature, oxygen depletion and production of CO2 , CO, total hydrocarbons, and water vapor were made. As expected, the presence of moisture delays the decomposition process and dilutes the decomposition products. The surface temperature and the evolved mass flux at ignition increased with increase in moisture content, decrease in oxygen concentration and increase in air velocity. All the ignition data are correlated according to an equation derived for surface temperature with convective and radiative heat losses. This equation reveals how the moisture content, air velocity, oxygen concentration and external radiation affect the ignition delay time. It also enables the determination of the critical incident heat flux below which piloted ignition does not occur.

Effect of Boron Particle Surface Coating on combustion of solid propellants for ducted rockets

Abstract: Combustion behavior of B/MA/AP/HTPB fuel rich propellants containing different coated boron particles was studied with several diagnostic facilities such as windowed strand burner, CO2 laser ignition facility, rapid depressurization quenched device, thermal analyzer and micromotor static test. Materials selected for boron coating include LiF, Viton A and silane. Baseline propellant containing uncoated boron was also studied for comparison Results from windowed strand burner and static test show that LiF-propellant exhibits the most remarkable overall behavior. Ignition study indicates that LiF-propellant gives the shortest while Viton A-propellant gives the longest ignition time under the same heat flux. Moreover, mechanisms were proposed to elucidate the experimental results and the observed combustion phenomena.

Ignition and combustion of boron in wet and dry atmospheres

Abstract: A description of ignition and combustion of boron particles is developed with the aim of obtaining a theory that is as simple as possible yet consistent with available data. For the ignition stage the model involves equilibrium reactive dissolution of B in the thin B2O3(l) layer to form dissolved BO, for example, surface attack of BO by O2(g) and by H2O(g) to form BO2(g), and HOBO(g), respectively, vaporization of B2O3, and later clean-surface attack of B by O2(g) to form B2O2(g). For the combustion stage the mode involves only the last of these processes. Values of relevant rate constants are identified that achieve agreement with experiments. Early laser-ignition experiments, not previously explained quantitatively, are employed for obtaining needed dry-gas rate parameters. New experiments on ignition and combustion of boron suspensions in hot combustion products of a flat-flame burner are performed to test adopted values of wet-gas rate parameters. Results provide a basis for calculation of ignition and combustion of boron in propulsions applications.

Method of starting a gas turbine engine

Abstract: A method of starting a gas turbine engine eliminating the need for oversizing a starter motor or the like to attain a proper transition through the "pinch point" includes the steps of applying a torque from an external source to the gas turbine engine (10) to accelerate the same toward a self sustaining speed, igniting fuel in the engine (10) at a pre-determined speed less than the self-sustaining speed, and at or about the time of fuel ignition, momentarily increasing the torque applied to accelerate the engine (10). The acceleration torque and momentary increase can be achieved by applying torque from a gas turbine containing auxiliary power unit (20) to an engine (10) either mechanically or pneumatically and then overspeeding and/or increasing the turbine inlet temperature of the gas turbine within the APU (20) to achieve a momentary burst of torque.

Diagnostic device for gas turbine ignition system

Abstract: A device for diagnosing the state of health of an ignition system is provided, where the system includes at least one spark producing channel comprising an exciter, output circuit and igniter plug. The device provides a diagnosis of the state of health for both the exciter and igniter plug by monitoring the high energy pulses at the output of the exciter. By monitoring the ignition system at an intermediate point in the system such as the output of the exciter, the sensor and electronics of the device may be completely contained within the electronic environment of the exciter, thereby avoiding any need for attaching sensors at the output of the system adjacent to the igniter plug in order to diagnose the plug's state of health. As an alternative to the device being built into the ignition system, it can be incorporated into automatic test equipment that produces high energy pulses for delivery to an igniter plug to be tested. The device is capable of diagnosing failure of either the exciter or the igniter plug and may also be configured to detect the impending failure of the plug.

Ascertaining running irregularity value of IC engine - deriving correction term from medians formed from time spans differences of ignition phases

Abstract: At least one crankshaft angle sector related to the t.d.c. of each cylinder before its ignition phase is set out. The sector time spans for each ignition phase during which the given crankshaft angle sectors are covered are measured. A first difference is formed from two sector time spans for each ignition phase. This provides a basic running deviation term. A correction term for running deviation is obtained. The running deviation value is obtained by correcting the basic term through subtraction of the correction term. The correction term is derived through medians formed from several sector time span differences for ignition phases of interest. ADVANTAGE - Median deviation ensures that not only linear but also at least a partial class of non-linear accelerations and decelerations can be fully compensated. Running irregularity value not affected at all.

Ignition and structure of a laminar diffusion flame in a compressible mixing layer with finite rate chemistry

Abstract: The ignition and structure of a reacting compressible mixing layer is considered using finite rate chemistry lying between two streams of reactants with different freestream speeds and temperatures. Numerical integration of the governing equations show that the structure of the reacting flow can be quite complicated depending on the magnitude of the Zeldovich number. An analysis of both the ignition a diffusion flame regimes is presented using a combination of large Zeldovich number asymptotics and numerics. This allows to analyze the behavior of these regimes as a function of the parameters of the problem.

A Thermal Model For Piloted Ignition Of Wood Including Variable Thermophysical Properties

Abstract: A simplified thermal model of piloted ignition is formulated. The model equations are then solved numerically for the thermally thick case using a finite difference technique. A systematic analysis of some solutions leads to a functional relationship between ignition time fig and irradiance «; suitable for correlation of piloted ignition data. This suggests plotting ignition data in a graph of (figtO.547 versus q;. The critical irradiance n: is then found as the intercept with the abscissa of a straight-line fit through the data. An apparent kpc can be obtained from the slope of the regression line. Theoretical calculations show that this apparent kpc for wood products is evaluated at a temperature approximately halfway between T\", and 1;g. The suggested correlating procedure is applied to measurements for six oven dry wood species obtained in the Cone Calorimeter.

High-pressure discharge lamp and lighting method

Abstract: The invention provides a high-pressure discharge lamp incorporating an outer envelope storing a pair of electric terminals a plurality of arc tubes which are respectively stored in this outer envelope and electrically connected in parallel, and a plurality of ignition aids available for assisting operating of these arc tubes, where these ignition aids are provided for each of these arc tubes and contain potentials different from each other. In addition, the invention also provides a lighting system for operating the high-pressure discharge lamp. The lighting system comprises the first and second power supply lines which respectively provides mutual connection between a pair of terminals of the high-pressure discharge lamp, a ballast which is at least provided for either of the first and second power supply lines, a power switch which is provided for either the first or the second power supply line, a pulse generating means which generates either the positive or the negative ignition pulses to be superimposed on AC power voltage output from an AC power supply source, and a control circuit which alters polarity of the ignition pulses output from the pulse generator.

Distributorless capacitive discharge ignition system

Abstract: A high power high energy distributorless ignition system for multicylinder internal combustion engines using a single energy storage capacitor (4), a single leakage resonating inductor (20) with a switch SS partially or entirely across it, and one or more coils Ti with bi-directional switches Si and with single or double hith voltage outputs, the system defining a compact coil assembly powered by a resonant converter power supply (12), the ignition power delivery controlled by means of circuitry based on a robust gate (17), an oscillator (19), and steering circuitry (21).

Ignition and extinction of surface and homogeneous oxidation of NH3 and CH4

Abstract: Ignition, extinction and autothermal behavior of surface and homogeneous oxidation reactions of CH4, NH3, and mixed NH3/CH4 fuel systems in air over resistively heated Pt foils was studied in an atmospheric pressure flow reactor. Also examined were the effects of varying fuel concentration on the ignition, extinction, and autothermal surface temperatures. Heterogeneous ignition occurred at ∼200°C for NH3 and at ∼600°C for CH4. The mixed fuel systems exhibited two surface ignitions (∼200°C and ∼600°C), implying a sequential ignition of the two fuels. The effects of removing one of the fuels during autothermal operation gave results consistent with this hypothesis. In homogeneous ignition, two types of flames were observed: a boundary layer flame associated with NH3 systems and an independent flame observed in all systems. Homogeneous ignition of the two fuels and the mixtures occurred at surface temperatures ranging from 1,100°C to 1,600°C and appeared to be dominated by CH4 in the mixed systems. A generic behavior is proposed for homogenous-heterogeneous combustion of single and mixed fuels.

Extinction of a Free Methanol Droplet in Microgravity

Abstract: The combustion of isolated, unsupported methanol droplets under microgravity conditions has been studied in the NASA-Lewis 2.2-sec drop tower. The substitution of O2/He mixtures for O2/N2 mixtures results in a substantial increase in the oxygen index required for ignition, the rate of gasification, and the diameter at extinction. As a result, droplets with initial size larger than 1 mm can be produced, deployed, ignited, and burned to extinction, all under microgravity conditions in this facility. A comprehensive time dependent numerical model incorporating detailed multicomponent molecular transport mechanisms and complex elementary chemical kinetics was developed and applied to simulate the entire transient droplet combustion processes (ignition/quasi-steady burning/extinction). Model outputs show good agreement with the experimental measurements, without parameter adjustment. Analysis of modeling results shows that the thermal conductivity of the gas phase under combustion environments increased by a factor of two when the 50-percent O2/50 percent He mixture is used instead of air. The increased thermal conductivity accelerates the heat transfer from the flame front to the droplet surface, resulting in a factor of two increase in the burning rate.