Ignition Technique Research Articles

Particulate emissions from laser ignited and spark ignited hydrogen fueled engines

Exponentially increasing energy demand and stricter emission legislations have motivated researchers to explore alternative fuels and advanced engine technologies, which are more efficient and environment friendly. In last two decades, hydrogen has emerged as promising alternative fuel for internal combustion (IC) engines and vehicles. For gaseous fuels, laser ignition (LI) has emerged as a novel ignition technique due to its superior characteristics, leading to improved combustion, engine performance and emission characteristics. Numerous advantages of LI system such as flexibility of plasma location, lower NOx emissions and capability of igniting ultra-lean fuel–air mixture makes LI system superior compared to conventional spark ignition (SI) system. This study experimentally compares particulate emissions from hydrogen fueled engine ignited by LI and SI systems. Experiments were performed in a constant speed engine prototype, which was suitably modified to operate on gaseous fuels using both LI as well as SI systems. Particulate were characterized using engine exhaust particle sizer (EEPS) spectrometer. Results showed that LI engine resulted in relatively higher particulate number concentration as well as particulate mass compared to SI engine. In both ignition systems, particulate emissions increased with increasing engine load however rate of increase was relatively higher in LI system. Relatively larger count mean diameter (CMD) of particulate emitted from SI engine compared to LI engine was another important observation. This showed emission of relatively smaller particles in larger numbers from LI engine, compared to baseline SI engine.

Coagulation and splitting of droplets of coal-water slurry containing petrochemicals and their effect on ignition characteristics

The coal-water slurries based on different types of coals and waste petrochemicals or other combustible liquids (CWSP) are very attractive for creation of cheap energetic fuel (for replacement of the coal and gas). Together with evident economic effect, the CWSP is perspective from ecological point of view. It contains a lot of water and therefore the air pollution by nitrogen and sulphur oxides is low. However, the energetic parameters of combustion of such slurry are enough far from excellence. Numerous publications were done during last years about development of new CWSP compositions as well as about improvements of its ignition and combustion techniques. The actual task is stable ignition of the slurry composition at low (critical) temperatures. In this work, we have investigated for a first time the influence of coagulation and splitting of fuel droplets onto the integral parameters of the ignition (using high-speed video-recording technique). These results clearly show the differences of ignition processes of single CWPS droplets and the aerosol flow ignition in combustion chamber. Our experiments gave the understanding of scales of co-influence of fuel droplets onto the ignition parameters. We have used the fuel compositions based on milled (particle size ∼100μm) lignite and bituminous coal, coal-processing wastes, waste industrial oils and mazut. The investigations were done for two-body system where droplet sizes were the same (0.5–1.5mm) at every experiment. The temperature in the combustion chamber was in range from 600K to 1200K. Some sequences of coagulation/splitting were observed: coagulation/splitting inside the combustion chamber; droplet coagulation before injection into the combustion volume. The influence of these processes on the ignition delay time and critical ignition temperature was defined. It was shown that splitting of the CWSP droplets leads to essential (for some times) decrease of the heating stage duration and faster ignition. Otherwise, the coagulation leads to deceleration of fuel heating and therefore to deceleration of gas-phase and heterogeneous ignition. It was shown for a first time that ignition delay time of coagulating droplets can be determined as average value between ignition delays of separate initial droplet and the droplet with the twice bigger volume. The critical ignition temperatures of separate fuel droplets are in range between temperature conditions of the splitting and coagulation. The ignition delay times of fuel fragments which appear after splitting are much lower than for initial droplets. At low temperature ignition the conditions of droplets coagulation and splitting are very important because the ignition delays durations can differ for some times. The influence of the coagulation and splitting effects becomes vanishingly small at oxidant flow temperature more than 1000K. The obtained in this paper results should be accounted for combustion chambers working in low-temperature regime of the CWSP combustion that looks attractive from ecological, technical, economical and fire-safe points of view.

Ignition and monitoring technique for plasma processing of multicell superconducting radio-frequency cavities

An in-situ plasma processing technique has been developed at the Spallation Neutron Source (SNS) to improve the performance of the superconducting radio-frequency (SRF) cavities in operation. The technique uses a low-density reactive neon-oxygen plasma at room-temperature to improve the surface work function, to help remove adsorbed gases on the RF surface, and to reduce its secondary emission yield. SNS SRF cavities have six accelerating cells and the plasma typically ignites in the cell where the electric field is the highest. This article details the technique to ignite and monitor the plasma in each cell of the SNS cavities.

Effect of draught conditions and ignition technique on combustion performance of firewood roomheaters

Firewood roomheaters are popular, widespread and important for reaching European CO2 emission targets. Since they contribute significantly to local air pollution, they have to be optimized towards minimal emission release, especially in real-life operation. Draught conditions and user behavior, particularly the ignition technique, significantly affect the emission and efficiency performance of firewood roomheaters. This study assessed the effects of the respective parameters experimentally. The results revealed a clear correlation between draught conditions and thermal efficiency. Increased draught conditions up to 48 Pa significantly decreased thermal efficiency by 6%–11% absolutely. However, for gaseous emissions no clear trend was observed. Accordingly, CO and OGC emissions increased at higher draught conditions for one tested roomheater by 30% and 60%, but decreased for two other tested roomheaters by 13%–45%. For PM emissions no effect of increased draught conditions was evident. Top-down ignition technique did not lead to a significant decrease of PM emissions compared to bottom-up ignition. In contrast, bottom-up ignition led to best thermal efficiencies. The use of either spruce or beech as kindling material revealed no significant relevance for the ignition performance.

Low voltage ignition of nanoenergetic materials with a conductive paper heater for compact remote ignition system

A solution-processed conductive paper heater (CPH) with metallic features is used as a new class of low voltage ignitor of nanoenergetic materials (nEMs). In contrast to conventional electrothermal ignition techniques that typically require high operating voltages, the combustion of a paper substrate with a relatively low ignition point generates high thermal energy instantaneously, which makes it possible to ignite nEMs even at low voltages as low as ∼1V. In addition, the ignition and explosion properties of CPH-based low voltage ignitors are highly controllable and reproducible, mainly due to their simple fabrication and reliable electrical properties. Based on the low voltage ignition property, a compact remote ignition system is demonstrated by integrating wireless a switching circuit, portable batteries, and heater mounter in a small plastic package and operated remotely to ignite the nEMs.

Quantified infrared imaging of ignition and combustion in a supersonic flow

The utility of quantified infrared radiation imaging was evaluated through interrogating ignition and burning processes within a cavity-based flameholder in supersonic flows. Two ignition techniques, spark discharge and pulse detonation, along with quasi-steady cavity burning were used to assess the sensitivities of measurements of radiation intensities in the infrared. The shedding of ignition kernels from the spark discharge was imaged, showing that sufficient signal-to-noise ratios can be achieved even with weak radiation emission levels. The ignition events using a pulse detonator were captured with time-resolved measurements of the plume evolution, including the barrel shock, Mach disk, and shock diamonds. Radiation emissions from subsequent firings of the pulse detonator increased, indicating that heat loss to the tube walls occurred in the early pulses. Imaging of the quasi-steady burning within the cavity demonstrated that the highest burning flux (visible broadband chemiluminescence) and radiation from hydrocarbons (3.4 µm) do not coincide with each other for the fueling strategy used. Numerical simulations provided insight into the species distributions that caused the infrared emissions. Overall, infrared radiation measurements have been shown to be feasible through combustor windows in the harsh combustion environments that were interrogated, and offer a new avenue for rapid and quantitative measurements of reactive flow.

Conventional versus microwave combustion synthesis of CoFe2O4 nanoparticles

Cobalt ferrite (CoFe2O4) nanoparticles have been synthesized by sol–gel autocombustion method ignited by conventional and microwave heating techniques. The precursor solutions were prepared with different fuel types such as citric acid and urea. The ignition technique and fuel type affected the phase evolution, microstructure, and magnetic properties of CoFe2O4 nanoparticles. X-ray diffraction results revealed that the single-phase and well-crystallized CoFe2O4 nanoparticles would only be formed using citric acid as fuel and after calcination at 600 °C. Microwave ignition resulted in the formation of larger sphere-like CoFe2O4 particles, possibly due to the contribution of microwave-absorbing products in attaining of higher temperatures. Furthermore, the single-phase CoFe2O4 nanoparticles synthesized by microwave ignition exhibited the higher saturation magnetization (Ms = 77 emu/g) compared to that of conventional method (Ms = 53 emu/g), due to their larger particle size and higher inversion coefficient. Magnetization curves of the as-combusted and as-calcined samples (CCA: conventional ignition with citric acid fuel, MCA: microwave ignition with citric acid fuel, CU: conventional ignition with urea fuel, and MU: microwave ignition with urea fuel).

Ultraviolet Laser-induced ignition of RDX single crystal.

The RDX single crystals are ignited by ultraviolet laser (355 nm, 6.4 ns) pulses. The laser-induced damage morphology consisted of two distinct regions: a core region of layered fracture and a peripheral region of stripped material surrounding the core. As laser fluence increases, the area of the whole crack region increases all the way, while both the area and depth of the core region increase firstly, and then stay stable over the laser fluence of 12 J/cm2. The experimental details indicate the dynamics during laser ignition process. Plasma fireball of high temperature and pressure occurs firstly, followed by the micro-explosions on the (210) surface, and finally shock waves propagate through the materials to further strip materials outside and yield in-depth cracks in larger surrounding region. The plasma fireball evolves from isotropic to anisotropic under higher laser fluence resulting in the damage expansion only in lateral direction while maintaining the fixed depth. The primary insights into the interaction dynamics between laser and energetic materials can help developing the superior laser ignition technique.

Numerical Simulation on the Laser Induced Oxygen Spark under Different Ambient Conditions

Abstract As a new type of ignition technique, laser induced spark ignition can be widely used in the ignition system of internal combustion engines and aero-engines. In this paper, laser induced oxygen spark evolution has been numerically studied with a two-dimensional, unsteady, multi-components and time-accurate model under different ambient temperatures and pressures. The chemical kinetics between species has been considered. A commercial software Fluent is used to solve the problem. Results show that both ambient conditions have great effect on the maximum temperature and maximum pressure of oxygen spark initially, but the effect decreases with time going on. The maximum velocity and maximum electron number density are also prominently influenced by ambient conditions. For the relationship between shock wave radius and time, ambient temperature plays an important role while ambient pressure is insignificant. These results above will be the foundation for the applications of laser induced spark ignition in the future.

Fabrication and Characterization of Graphene from Solid Carbon Dioxide

Graphene was fabricated by a well-known technique of ignition of magnesium (Mg) metal ribbon in solid carbon dioxide. Two dry ice slabs were used as carbon source for the production of graphene. A hemispherical cavity of about 3-4 cm diameter was carved on surfaces of both dry ice slabs. About 0.5g of Mg ribbon was burnt and immediately placed into the dry ice cavity. It was then covered up by another carved slab of dry ice. After complete combustion, mixture of black and white residues was formed. It was then recovered. 20 ml of 1 M HCl acid was added to the product mixture. Reaction of HCl with MgO and unburned Mg formed MgCl2 which was then washed away by deionized water. The isolated carbon material was separated as product. Characterization of the product was performed using optical microscopy (OM), where images showed the presence of sheet-like light gray objects. Field emission scanning electron microscopy (FESEM) and transmission electron microscope (TEM) analyses revealed the presences of graphene. The lateral length of the sheet was about 3-3.5 μm and the surface area was about 3-5.5 μm2 using images analysis software.

Influence of operating conditions on chemical composition of particulate matter emissions from residential combustion

Wood combustion experiments were carried out in a Portuguese woodstove to determine the effects of biofuel type, ignition technique, biomass load and cleavage, as well as secondary air supply, on the chemical composition of particles (PM10). Two typical wood fuels in the Iberian Peninsula were tested: pine (Pinus pinaster), a softwood, and beech (Fagus sylvatica), a hardwood. PM10 samples were analysed for organic and elemental carbon (OC and EC), levoglucosan and 56 elements. Total carbon (TC) represented 54–73wt.% of the particulate mass emitted during the combustion process, regardless of wood species burned or operating condition tested. The carbonaceous component of PM10 was dominated by OC. The OC content of PM10 was higher when higher loads were fed into the combustion chamber, for both fuels. EC represented from 8 to 35wt.% of the particulate mass. OC/EC ranged from 1.1 to 6.1 (avg. 3.0±1.8) for pine combustion and from 1.1 to 3.4 (avg. 2.0±0.8) for beech combustion. The lowest OC/EC ratios for both woods were observed for ignition from the top. Levoglucosan was found in all samples, representing from 3.7 to 7.5wt.% and from 4.2 to 8.9wt.% of PM10 emitted from the combustion of pine and beech, respectively. The use of low loads of fuel generated high amounts of levoglucosan either for pine or beech. Altogether, trace elements obtained by ICP-MS and ICP-AES comprised from 0.46wt.% to 1.41wt.% and from 0.87wt.% to 2.36wt.% of the PM10 mass for pine and beech combustion, respectively. Among elements, K, Ca, Na, Mg, Fe and Al contributed to more than 75% of the total ICP-MS mass. Potassium was the major element in almost all PM10 samples.

Solution combustion synthesis of La1−xSrxFe1−yCuyO3±w (x=0, 0.2; y=0, 0.2) perovskite nanoparticles: Conventional vs. microwaves ignition

La1−xSrxFe1−yCuyO3±w (x=0, 0.2; y=0, 0.2) nanoparticles have been prepared by solution combustion synthesis exploiting both conventional and microwave heating in the ignition of the self-sustaining reactions. Interaction of microwaves with the reaction mixture allowed significant reduction of the ignition time according to the dielectric properties of the precursor gels, which have been measured at room temperature in the 0.5–3GHz frequency range. Both the ignition strategies led to the preparation of crystalline single-phase products without affecting particles morphology. The ignition technique influenced only the average particles size with those prepared by microwaves-ignition, possessing typically larger dimension, as a probable consequence of the higher temperatures reached due to microwave absorbing products. Perfectly crystallised nanoparticles were obtained after combustion syntheses and calcination at 600°C for 3h in the particle size range between 20 and 80nm dependently upon the heating source and the dopant level.

Comparative study of laser ignition and conventional electrical spark ignition systems in a hydrogen fuelled engine

Increasing population and demand for fossil fuels is leading to rapid depletion of petroleum reserves. Hydrogen has great promise as an alternative fuel for powering next generation internal combustion engines with improved thermal efficiency and reduced emissions. Laser ignition (LI) has emerged as an efficient ignition technique for delivering superior engine efficiency with lower emissions. Use of LI to initiate combustion in an engine fuelled with hydrogen–air mixtures can greatly help in reducing emissions, improving engine performance and tackling the problem of fossil fuel depletion. In this study, a laser ignited hydrogen fuel prototype engine has been developed and comparison of its performance, emissions and combustion parameters is done with baseline data generated using conventional spark ignition (SI) system.

The influence of ignition technique on fire behaviour in spinifex open woodland in semiarid northern Australia

Unplanned, unmanaged wildfires are a significant threat to people, infrastructure and ecosystems around the world. Managed, planned burning is widely used for reducing the incidence, extent or intensity of wildfires. Fire weather and the season of burning are recognised as crucial factors influencing fire behaviour but the demonstrated influence of ignition technique on fire behaviour is not as prominently discussed in relation to planned fires. We found wildfires, irrespective of season, burnt the ground layer more completely (i.e. were less patchy) and produced greater crown scorch severity than did planned fires in a spinifex (Triodia spp.)-dominated open woodland. Fires ignited with a 50-m line burning with the wind produced significantly higher intensities than did line ignition against the wind, and spot ignitions with or against the wind. These data suggest that the higher severity of wildfires in spinifex-dominated habitats is strongly influenced by long fire fronts, in addition to fire season and weather conditions. This study supports the value of planned burning for reducing fire severity and highlights the value of spot ignitions in ecological burning to create a patchily burnt landscape, with limited canopy severity.

Emission of carbon monoxide, total hydrocarbons and particulate matter during wood combustion in a stove operating under distinct conditions

Wood combustion experiments were carried out to determine the effect of ignition technique, biomass load and cleavage, as well as secondary air supply, on carbon monoxide (CO), total hydrocarbon (THC), particulate matter (PM10) and particle number emissions from a woodstove. Wood from two typical tree species in the Iberian Peninsula was selected: pine (Pinus pinaster) and beech (Fagus sylvatica). The highest CO and total hydrocarbon emission factors (EFs) were observed, respectively, for pine and beech, for high and low fuel loads. The highest PM10 EF was recorded for the operation with low loads for both woods. Secondary air supply produced the lowest PM10 emission factors. The top ignition can decrease the PM10 EF to less than half when compared with the common technique of lighting from the bottom. The lowest particle number emission factors were observed when operating with high loads of split beech logs and when using secondary air supply during the combustion of pine. Regarding particle number distributions, the highest geometric mean diameter (Dg), for both woods, were observed when operating with high loads (with split and non-split wood).

Investigation on the flame characteristics in a PCCI engine using endoscope system with micro-cassegrain

Diesel engines are most frequently used in vehicles because of their high efficiency and durability. However, nitrogen oxide (NOx) and particulate matter (PM) from diesel engines are became problem. Recently, the premixed charged compression ignition (PCCI) technique has been studied specifically to reduce NOx and PM emissions simultaneously. While the PCCI engine has the advantage of reducing NOx and PM emissions, control of the combustion phase is difficult. Therefore, it is very important to understand the flame developing process and heat release pattern in a real PCCI engine. However, most research into the characteristics of PCCI combustion has used an optical access engine. This paper describes the combustion characteristics obtained using a micro-Cassegrain sensor and discusses how the sensor can be used to directly detect the flame characteristics for future control of PCCI combustion. From this research, the differences of flame characteristics between PCCI engine and conventional diesel engine were clarified.

High Temperature Oxidation of Nickel-based Cermet Coatings Composed of Al2O3 and TiO2 Nanosized Particles

AbstractNew technological challenges in oil production require materials that can resist high temperature oxidation. In-Situ Combustion (ISC) oil production technique is a new method that uses injection of air and ignition techniques to reduce the viscosity of bitumen in a reservoir and as a result crude bitumen can be produced and extracted from the reservoir. During the in-situ combustion process, production pipes and other mechanical components can be exposed to air-like gaseous environments at extreme temperatures as high as 700 °C. To protect or reduce the surface degradation of pipes and mechanical components used in in-situ combustion, the use of nickel-based ceramic-metallic (cermet) coating produced by co-electrodeposition of nanosized Al2O3 and TiO2 have been suggested and earlier research on these coatings have shown promising oxidation resistance against atmospheric oxygen and combustion gases at elevated temperatures. Co-electrodeposition of nickel-based cermet coatings is a low-cost method that has the benefit of allowing both internal and external surfaces of pipes and components to be coated during a single electroplating process. Research has shown that the volume fraction of dispersed nanosized Al2O3 and TiO2 particles in the nickel matrix which affects the oxidation resistance of the coating can be controlled by the concentration of these particles in the electrolyte solution, as well as the applied current density during electrodeposition. This paper investigates the high temperature oxidation behaviour of novel nanostructured cermet coatings composed of two types of dispersed nanosized ceramic particles (Al2O3 and TiO2) in a nickel matrix and produced by coelectrodeposition technique as a function of the concentration of these particles in the electrolyte solution and applied current density. For this purpose, high temperature oxidation tests were conducted in dry air for 96 hours at 700 °C to obtain mass changes (per unit of area) at specific time intervals. Statistical techniques as described in ASTM G16 were used to formulate the oxidation mass change as a function of time. The cross-section and surface of the oxidized coatings were examined for both visual and chemical analyses using wavelength dispersive x-ray spectroscopy (WDS) element mapping, X-ray Diffraction (XRD) and Energy-dispersive X-ray spectroscopy (EDS). The results showed that the volume fraction for each type of particle in the nickel matrix corresponded to its partial molar concentration in the electrolyte solutions. Increase in volume fraction of particles in the nickel matrix was correlated to lower oxidation rates. It was concluded that formation of Ni3TiO5 and NiTiO3 compounds can reduce the oxidation rate of cermet coatings by capturing some inward diffusing oxygen ions resulting in a lower number of nickel cations diffusing upward into the oxide layer.

Research and Application of Technology of Mobile Electric Ignition Technology for Fire Flood in Vertical Hole

In-Situ combustion is an important transformation mode for heavy oil development, and the key to its success is ignition in the reservoir, On the basis of investigation and research into some related techniques both at home and abroad, this paper presents the development of mobile electric igniter, technical string, down-hole monitoring system, putting-in and putting-out device; the integral outside diameter of the igniter is φ25.4mm; this paper forms the technique of mobile electric ignition for fire flood in vertical hole and introduces the technical principle. The field test results show that the maximum outlet air temperature of the igniter is 527°C when the steam injection rate is 6500Nm3/d; And that realizes high temperature igniting of mobile electric igniter for the first time. This technique will effectively reduce the operation cost of fire flood, and provides technical reserve for separate zone ignition in thick mass oil pool of Liaohe Oilfield.

Comparative Forensic Soil Analysis of New Jersey State Parks Using a Combination of Simple Techniques with Multivariate Statistics,

This study has shown that the combination of simple techniques with the use of multivariate statistics offers the potential for the comparative analysis of soil samples. Five samples were obtained from each of twelve state parks across New Jersey in both the summer and fall seasons. Each sample was examined using particle-size distribution, pH analysis in both water and 1 M CaCl2 , and a loss on ignition technique. Data from each of the techniques were combined, and principal component analysis (PCA) and canonical discriminant analysis (CDA) were used for multivariate data transformation. Samples from different locations could be visually differentiated from one another using these multivariate plots. Hold-one-out cross-validation analysis showed error rates as low as 3.33%. Ten blind study samples were analyzed resulting in no misclassifications using Mahalanobis distance calculations and visual examinations of multivariate plots. Seasonal variation was minimal between corresponding samples, suggesting potential success in forensic applications.

Core–shell-structured nanothermites synthesized by atomic layer deposition

Thermite materials feature very exothermic solid-state redox reactions. However, the energy release rates of traditional thermite mixtures are limited by the reactant diffusion velocities. In this work, atomic layer deposition (ALD) is utilized to synthesize thermite materials with greatly enhanced reaction rates. By depositing certain types of metal oxides (oxidizers) onto a commercial Al nanopowder, core–shell-structured nanothermites can be produced. The average film deposition rate on the Al nanopowder is 0.17 nm/cycle for ZnO and 0.031 nm/cycle for SnO2. The thickness of the oxidizer layer can be precisely controlled by adjusting the ALD cycle number. The compositions, morphologies, and structures of the ALD nanothermites are characterized by X-ray photoelectron spectroscopy, scanning electron microscopy, and high-resolution transmission electron microscopy. The characterization results reveal nearly perfect coverage of the Al nanoparticles by uniform ALD oxidizer layers and confirm the formation of core–shell nanoparticles. Combustion properties of the nanothermites are probed by laser ignition technique. Reactions of the core–shell-structured nanothermites are several times faster than the mixture of nanopowders. The promoted reaction rate is mostly attributed to the uniform distribution of reactants on the nanometer scale. These core–shell-structured nanothermites provide a potential pathway to control and enhance thermite reactions.