Showing papers on "Ignition system published in 1992"

Hot-spot ignition mechanisms for explosives and propellants

Abstract: This paper describes the response of explosives to stress and impact and in particular the mechanisms of ‘ hot-spot production. Samples in the form of single crystals, powder layers, pressed pellets, gels, polymer bonded explosives (PBXS) and propellants have been studied. Techniques used include a drop-weight facility with transparent anvils which allows photography at microsecond framing intervals, an instrumented drop-weight machine, a miniaturized Hopkinson bar system for high strain rate property measurement, laser speckle for studying the deformation and fracture of PBXS, an automated system for analysing speckle patterns and heat sensitive film for recording the positions and temperatures of hot spots. Polishing and staining methods have been developed to observe the microstructure of PBXS and failure during quasi-static loading. Ignition, when it occurred, took place at local hot-spot sites. Evidence is discussed for a variety of ignition mechanisms including adiabatic shear of the explosive, adiabatic heating of trapped gases during cavity collapse, viscous flow, friction, fracture and shear of added particles and triboluminescent discharge.

A model for turbulent flame ignition and propagation in spark ignition engines

Abstract: A model describing flame ignition in a premixed turbulent flow is coupled to a flamelet model for turbulent combustion to describe flame ignition and propagation in a spark ignition piston engine. During the first instants of ignition, a laminar ignition model (called LI) solves the one-dimensional, spherical Navier-Stokes equations for a given chemical scheme to predict the radius of the first laminar flame kernel. In a second phase, this kernel grows because of laminar effects but is also stretched by turbulent eddies. Later, a criterion based on the comparison of the laminar stretch (due to the laminar flame kernel growth) and of the turbulent stretch (generated by turbulent eddies) is used to initiate the computation of a fully turbulent combustion. During this turbulent propagation, an extended version of the Coherent Flame Model (CFM) is used. This model includes a novel expression for turbulent flame stretch based on direct simulation results. The total model (LI-CFM) has been implemented in an improved version of KIVA including a k -e compressible model and a robust treatment for wall turbulence. The results are compared with experimental data (Schlieren visualizations, LDA measurements and pressure measurements) obtained on a fully instrumented laboratory engine. The LI-CFM model correctly predicts flame ignition and growth for a set of typical engine cases with no parameter adjustments. Computed effects of changes in spark timing, total pressure or equivalence ratio agree well with experimental results.

Global kinetics for n-heptane ignition at high pressures

Abstract: A kinetic mechanism of 1011 elementary reactions with 171 chemical species for n-heptane ignition is analysed and reduced to 4 global steps with adjusted rate coefficients to describe ignition at pressures around 40 atm. Two of these steps account for the high temperature branch and the other two for the low temperature branch of the ignition mechanism. The ignition delay time passes through a negative temperature dependence during the transition between the two branches. This is accounted for by the reversible third reaction step, which models the first and second O2-addition in the degenerated chain branching mechanism at low temperatures. Ignition delay times calculated with the adjusted 4-step model are compared to those from the detailed kinetics and experimental data. Finally the 4-step mechanism is analysed by asymptotic methods and explicit ignition delay time formulas are derived.

The Influence of the Temperature on Extinction and Ignition Limits of Strained Hydrogen-Air Diffusion Flames

Abstract: Structures, extinction and ignition limits of strained diffusion flames are examined. The influence of the oxidizer stream temperature is specifically considered. Calculations are performed for diffusion flames formed by a counterflow of diluted hydrogen and air. The air temperature differs from the hydrogen temperature. The reactive flow equations are solved numerically by employing Newton iterations and adaptive continuation techniques. The model includes detailed transport and complex kinetics. Flame structures, extinction and ignition limits and characteristic flame response curves are determined for different values of the fuel-air ratio and for a set of air stream temperatures. It is shown that this last parameter strongly affects the conditions producing extinction. For an air stream temperature of 100OK, the critical extinction strain rate is ten times that found for an air stream at room temperature It is also found that a temperature exists beyond which combustion always takes place wha...

Multiple purpose burner process and apparatus

Abstract: A multiple purpose burner process and apparatus in which a burner assembly having a burner member defining a burner throat bore extending therethrough and forming an ignition zone and at least one mixing zone in the burner throat bore, the total combustion air passing through the burner throat bore. A minor portion of fuel gas as ignition fuel produces a continuous ignition flame in the ignition zone, and plural meter channels extending through the burner member communicate with the mixing zone to pass an admixture of a diluent gas with the remainder portion of the fuel, as a primary fuel stream, to the mixing zone for forming with the remaining combustion air a primary fuel/diluent/combustion air mixture, and the primary fuel/diluent/combustion air mixture is ignited by the ignition flame in the mixing zone. Diluents can be internally recirculating flue gas or can be from an external source, and the flame envelope achieved by the burner assembly can be variously shaped for an industrial combustion application as required.

Ignition system for an engine

Abstract: An ignition system has a plurality of primary and secondary coils, ignition timing means for providing an ignition timing signal and current supply means for supplying a current to the primary coils in response to an ignition timing signal. A current is supplied to a plurality of the primary coils at the same time to charge the coils so that a charge time is shortened.

Operation of an internal combustion engine

Abstract: A method is described for reducing the total emissions during cold starts from an engine burning a hydrocarbon fuel and having an afterburner arranged upstream of a catalytic converter. The method comprises the steps of: (i) adding an excess of fuel to the engine combustible charge and adding air to the engine exhaust gases immediately after the engine has first fired to assure the presence in the exhaust/air mixture of sufficient concentrations of hydrogen and oxygen to permit the resulting exhaust/air mixture to be ignitiable and to burn with a steady flame in the afterburner while the latter is at a temperature close to the ambient temperature, and (ii) igniting the exhaust/air mixture in the afterburner immediately after the engine has first fired. In the preferred embodiment of the invention, the excess fuel and/or the additional air are regulated after ignition has occurred in the afterburner to maintain a steady flame in the afterburner until at least part of the matrix of the catalytic converter has reached its light off temperature.

Effectiveness of plasma torches for ignition and flameholding in scramjet

Abstract: A newly developed plasma torch with a feed stock of air or oxygen was investigated experimentally in order to determine its effectiveness on ignition and flameholding in a scramjet combustor. This design comes from the viewpoint of total system design of scramjet engine and vehicle because it is preferable to utilize incoming air or onboard propellants as a feed stock. Three patterns of fuel injection were tested 1) from one orifice: 2) from four orifices on one wall; and 3) from all nine orifices on both walls. Ignition and flameholding phenomena were examined through direct photographs of internal and exit flames of the combustor and by wall temperature measurements. The specially devised plasma torch with air or oxygen was able to operate stably without any support gas, for example, argon. Ignition limit curves, with and without the plasma torch, were obtained on a plane relating the air total temperature to the fuel equivalence ratio for the three patterns of fuel injection, and then compared to each other. For a wide range of experimental conditions, it was shown that the effectiveness of an air or oxygen plasma torch was comparable to that of a nitrogen or argon-hydrogen plasma torch. For single-wall injection, it was observed that the plasma torch ignited the fuel jet located directly downstream, and the flame thus formed ignited adjacent fuel jets. In double-wall injection, however, ignition of the fuel injected from the wall opposite the plasma torch was unsuccessful. It was also found that, under some conditions, flameholding can be continued even after the plasma torch is turned off, most notably in the case of single-wall injection. The occurrence or nonoccurrence of this phenomenon is also shown in the ignition limit curves diagram.

Effect of steady and periodic strain on unsteady flamelet combustion

Abstract: An unsteady, finite-rate kinetics, strained, flat-flame model is used to investigate the effects of unsteady dynamics on the burning rate and non-equilibrium processes including ignition, quenching and extinction in non-premixed combustion in the flamelet limit. Unsteady computations are performed for a steady and a periodic strain. Results show that for a shortduration (spark) ignition, a steady positive strain rate enhances the burning rate while exponentially increasing the ignition delay time. Increasing the strain rate leads to sudden quenching of the reaction, with no potential for re-ignition, as kinetic rates can no longer support combustion. The quenching strain is increased and ignition delay is substantially reduced when the ignition source is a long-duration “pilot-flame.” These results indicate that the burning rate depends strongly on the strain history, when flow and chemical time scales are close. An important example of strain history, which resembles that produced by a turbulent flow, is an oscillating strain. We find that flamelet combustion exhibits strong sensitivity to strain field oscillations. For high amplitude oscillation, the flame is quenched as the total strain exceeds the steady quenching strain, even though the mean strain may be well below the quenching strain. Partial quenching and re-ignition may replace permanent quenching if the frequency of oscillations is increased. When compressive strains prevail, partial extinction is observed. The flamelet re-ignites as positive strains induce reactants' fluxes towards the hot extinct reaction zone. quenching, partial quenching, extinction and re-ignition result in large variations in the unsteady burning rate and in a mean burning rate which is smaller than the steady burning rate computed using the mean strain.

Physics basis for compact ignition experiments

Abstract: Compact ignition experiments can be designed to attain peak densities n0 1021 m-3 reliably and to achieve low temperature D-T ignition under conditions where the heating power of the ?-particles does not exceed twice the ohmic heating power. An average current density near 1 kA/cm2 with a maximum plasma current Ip 12 MA are the reference design parameters of the representative Ignitor Ult machine. The peak density value is consistent with that of B/R0, as R0 1.3m and B 13 T, when compared to the Alcator, FT, and TFTR machines. The vacuum toroidal field B is reinforced by the contribution of a large paramagnetic poloidal current (I? < 10 MA). The high values of the poloidal field Bp (3.9T) produce a strong rate of ohmic heating, while the correspoinding high values of Ip ensure that most of the fusion ?-particles can be confined to deposit their energy in the central part of the plasma column. The confinement parameter n0 ?E is expected to exceed 4 x 1020sec/m3 by a considerable margin on the basis of the confinement properties of plasmas with prevalent ohmic heating. The necessary degree of plasma purity (Zeff ? 1.6) is expected to be ensured by the high particle densities, the high magnetic fields and the relatively low values of the thermal loading on the first wall. Since ignition is achieved through transient conditions rather than, as is frequently assumed, a sequence of steady state conditions, numerical simulations have shown that the ohmic power can remain considerable up to ignition, when programming the rise of the plasma current and the particle density while gradually increasing the cross section of the plasma. The volume where the magnetic parameter q ? 1 and macroscopic m0 = 1 plasma modes may be excited, has been shown to maintain quite low values until ignition is attained. The stability margin against these modes is made uniquely favorable by the low values of ?-poloidal that are characteristic of Ignitor. An injected heating source of 16MW of ICRF power is included to broaden the scenarios under which ignition is achieved.

Ignition system for combustion-powered tool

Abstract: For a combustion-powered tool, an ignition system is powered by a battery and is arranged so that a sudden discharge of a capacitor, as charged via an oscillator, produces a spark at a spark gap of a spark plug, so that the oscillator is enabled if a trigger switch is closed while a head switch is closed, but not if the trigger switch is closed while the head switch is opened, and if a battery voltage, as monitored, is not less than a reference voltage, and so that a silicon-controlled rectifier, which is arranged to produce a sudden discharge of the capacitor, is switched to a conductive state if the capacitor voltage, as monitored, and is not less than a reference voltage. The head and trigger switches, which are photoelectric, are polled intermittently to determine whether they are closed. Predominantly, solid-state components are used.

Integrated converter high power CD ignition

Abstract: A high power high energy capacitive discharge (CD) ignition system for internal combustion engines using a separate resonating inductor (7) in the discharge circuit which is constructed and arranged to provide suitable operation of the discharge circuit and to allow coupling of energy from a voltage source (13a) for storage in the inductor (7) for delivery to the CD system discharge capacitor (4) during the operation of the ignition to help maintain energy during the preferred mode of multiple spark pulse firings of an ignition spark in a preferred large toroidal gap spark plug and to recharge the capacitor (4) between firings.

The Measurement and Analysis of Swirl in Steady Flow

Abstract: The influence of swirl on combustion in diesel and spark ignition engines is reviewed briefly, and this leads to a resume of the swirl measuring techniques. The numerous ways of analysing swirl data are summarised and the relations between the different swirl parameters are presented. Experimental results are presented from a diesel engine in which the flow has been measured by a hot wire anemometer, a paddle wheel and a swirl torquemeter. The performance of the different measurement techniques is compared. Further results are presented (from a spark ignition engine) which illustrate the influence of the inlet port, manifold and entry conditions on the swirl measurements. Integration techniques are reviewed for producing a single swirl parameter to characterise the combined performance of the inlet port, valve and camshaft. Finally, the difficulty in standardising measurements of barrel swirl are discussed. © Copyright 1992 Society of Automotive Engineers, Inc.

Ignition system for water-cooled gas engines

Abstract: A water-cooled, spark-ignited, natural gas burning engine that includes an improved ignition system having a pair of precombustion chambers located in series connected by an orifice from the first chamber into the combustion chamber of the engine whereby a relatively rich fuel/air mixture, ignited in the second prechamber, propagates a flame through an orifice into the first chamber wherein a leaner fuel/air mixture from the combustion chamber is plasma ignited which in turn creates a larger flame that is projected through an orifice into the main combustion chamber for plasma igniting a lean fuel/air mixture which could not otherwise be ignited by spark ignition. The invention also contemplates a kit providing the above for use in converting water-cooled, diesel burning, compression ignited engines into water-cooled, natural gas burning, spark-ignited engines.

Simplex airblast fuel injection

Abstract: A simplex air blast fuel injection system for the atomization of fuel for ignition to drive a gas turbine includes a simplex nozzle which receives fuel from a fuel pump powered by the turbine over a range of pressures between maximum and minimum pressures during the operation of the turbine, and also receives fuel at a substantially lower pressure than the minimum fuel pressure when the turbine is cranked during startup The fuel is discharged from the nozzle orifice as a swirling stream of atomized fuel during turbine operation, and as a film which is insufficiently atomized to initiate ignition during the turbine startup An air compressor is also powered by the turbine to supply air at a low pressure to the fuel issuing from the nozzle orifice during both turbine operation and startup An air director shroud imparts a swirling motion to the low pressure air and directs the swirling air to adjacent the fuel film as it issues from the nozzle orifice during startup to produce a pressure differential between opposite sides of the film to explode and atomize the fuel film sufficiently to permit ignition during turbine startup A stream of low pressure air is also directed to the swirling stream of atomized fuel during turbine operation and that air stream is also preferably swirling

Non-explosive power charge ignition

Abstract: A wellbore tool is provided to perform work in a wellbore by converting a chemical pressure source into a force exerted over a distance. The wellbore tool includes a pressure chamber sealed by a firing head and containing a power charge which includes a plurality of chemical components which are burned in a combustion reaction to generate gas. The combustion reaction of the power charge is initiated by a resistance heater which directly initiates the combustion reaction by receiving electrical energy and generating heat. The combustion reaction generates gas within the pressure chamber, the gas having a pressure which pushes a pressure responsive member into movement relative to the pressure chamber for providing a force over a distance to operate a downhole tool.

Dual energy ignition system

Abstract: An ignition system for hydrocarbon based fuels employing two energy sources (10, 16), one to create a spark, and the other to sustain the spark The ignition system is based in part on the principle of a strobe light circuit The system increases ignition efficiency by increasing the power dissipated at a spark gap (14), particularly when used in conjunction with a surface gap spark plug Maximum power transfer is achieved via impedance matching between a transformer (12) of the ignition system to the surface gap spark plug The circuit is particularly appropriate for igniting extremely lean mixtures, highly diluted mixtures, and alternative fuels

Gas generator ignition assembly using a projectile

Abstract: An ignition assembly in a motor vehicle inflatable safety system is provided, preferably to be used with a projectile In one embodiment, the ignition assembly includes an actuation piston and an activator, such as a percussion primer(s) and an ignition material, which are separated by a retention pin When a sufficient force is exerted on the actuation piston, the retention pin fails such that the actuation piston moves and impacts the percussion primer(s) to ignite the propellant within the gas generator The resulting propellant gases are thereafter provided in a predetermined direction(s) Advantageously, a check valve-like device is employed to substantially reduce the flow of propellant gases in a direction other than the predetermined direction(s) The preferred projectile also includes a body that has a smaller dimension than the projectile piercing head when the projectile is used to separate a closure disk to release stored, pressurized gases in addition to activating the gas generator In this case, the preferred projectile facilitates the controlled separation of any closure disk used to retain pressurized, stored gases used by the inflator in addition to the propellant gases

Ignition and combustion of magnesium in carbon dioxide streams

Abstract: The prospects for using Mg as fuel in a CO2-breathing engine in Mars atmosphere without oxygen led to this experimental study on the ignition and combustion of Mg performed in pure CO2 and CO2/CO streams over a wide range of pressure, velocity, and CO concentration of the streams. The critical ignition temperature of Mg in CO2 streams decreased with decreasing ambient pressure, and was insensitive to the stream velocity. The ignition temperature in CO2/CO streams varied little at first, but increased with decreasing CO2 concentration. Ignition occurred in two distinct stages, the first being surface reactions controlled by chemical kinetics and the second being gas-phase reactions controlled by CO2 diffusion. The breaking of a thin protective film formed in the first stage played a crucial role in the ignition process, leading to the beginning of the gas-phase reactions and then to ignition. During combustion, several flames appeared sporadically and intermittently over the swelling samplesurface, which was coated with a thick porous layer. The flames produced CO in the gas phase, while, on the nonflame surface, the reactions of Mg with both CO diffusing from the flames and CO2/CO in the streams generated condensed MgO and C that built the porous layer. The pulsating manner of the flames can be explained in terms of the abrupt breaking of the layer followed by its blockage due to the surface reaction with CO.

Capacitor discharge ignition system with inductively extended discharge time

Abstract: A capacitor discharge ignition device for an internal combustion engine includes a booster coil 21 and a transistor 22 for generating a boosted voltage; a circuit 15A for generating a switching signal for the transistor in response to an ignition signal; first and second condensers 7, 8 for charging with the boosted voltage; an ignition coil 10 to whose secondary a spark plug is connected; a thyristor 13 forming a first closed discharge circuit with the first condenser and the ignition coil primary, which is turned on in synchronism with the ignition signal; and an inductor 9 forming a second closed circuit with the second condenser, the ignition coil primary and the thyristor. The discharge energy of the second condenser stored in the inductor is supplied to the ignition coil primary to extend the discharge time at the spark plug. A delay circuit 16 prevents the transistor from turning on during the extended discharge time, thus establishing a third closed inductor discharge path through the booster coil.

Ignition system battery for preheating of automotive catalytic converter

Abstract: Method and apparatus for initiating electrical preheating of the catalytic converter the exhaust gas system of an internal combustion engine. The latter includes an ignition system having a battery as the engine starting medium, which is provisionally connected to the catalytic converter's heater element to raise the catalytic converter from ambient temperature, to an intermediate temperature, and subsequently to a temperature at which the catalytic converter will most effectively function.

Initiation of SHS processes

Abstract: Results of experimental and theoretical studies on combustion initiation in SHS systems reported in literature and carried out by the author with his colleges for recent 20 years are reviewed. Different procedures of initiation of the process in SHS systems such as radiant flux ignition, laser induction, ignition by combustion wave, spark and hypergolic ignition, etc. are considered. Mathematical models used in different works for description of transition processes taking place in initiation of SHS are discussed. The most interesting theoretical and experimental data are presented. Qualitative and quantitative fitting of calculated data with experimental results is analyzed.