Ignition Chamber Research Articles

Combustion and soot characteristics of hydrotreated vegetable oil compression-ignited spray flames

Quantitative measurements of combustion and in-flame soot in hydrotreated vegetable oil (HVO), biodiesel (rapeseed methyl ester [RME]) and diesel fuel spray flames are presented in this study. The measurements were performed in a compression ignition chamber with optical access having engine-like thermodynamic conditions. The simultaneously employed optical techniques were high-speed diffuse back-illuminated light extinction imaging for measuring the optical depth (KL) of in-flame soot, and OH* chemiluminescence for imaging high temperature reaction zones. The results show that diesel produces a considerably higher amount of in-flame soot compared to RME and HVO, which is likely due to the aromatics present in diesel, while RME and HVO produce similar levels. RME was found to produce slightly less soot, which is likely due to the fuel-bound oxygen, since HVO and RME have a similar number of carbon-carbon bonds. The soot production during the premixed and mixing-controlled period were found to have similar trends. The time lag between start of ignition and soot formation was found to be constant for varying ambient temperatures for individual fuels, where soot was detected earliest after ignition for diesel, followed by HVO and RME, matching the measured sooting tendencies. The stabilised flame lift-off length of HVO was found to be shorter than that of diesel, while RME had the shortest of them all.

Comparison of open chamber and pre-chamber ignition of methane/air mixtures in a large bore constant volume chamber: Effect of excess air ratio and pre-mixed pressure

Natural gas is an alluring choice to substitute the widely used diesel for environmental and economic reasons as it generates less particulate matter and carbon dioxide emissions. However, natural gas is comparatively difficult to be ignited and its flame penetrates slowly in a large bore combustion chamber especially for the lean condition. In order to analyze how the pre-chamber turbulent jet ignition promotes combustion in a large volume chamber, a comparative study with the traditional open chamber ignition mode was conducted to analyze the effect of excess air ratios and pre-mixed pressures on the combustion characteristics of methane/air mixtures. In rich fuel combustion, the advantage of pre-chamber is not obvious, and the flame propagation rate can only be increased by 2.8 times in maximum. In the case of lean combustion and stoichiometric combustion, the flame propagation speeds can be increased by 5–6 times, especially in lean combustion by pre-chamber. In general, the pre-chamber turbulent jet ignition technique can increase the flame propagation rate of methane/air, and improve combustion and thermal efficiency of natural gas large-bore engines under lean combustion conditions. With comparison to the open chamber ignition mode, the reduction percentage of ignition time by pre-chamber turbulent jet ignition decreases with the rise of initial pressure. However, the asymmetric placement of the spark plug inside the pre-chamber, results in the inhomogeneous spreading of flame jets in the constant volume chamber, which ought to be considered in the design of marine engine.

Embedded Control System for Recent Petrol Engine Control

In the current scenario of automotive industries, it is much challenging for the research and developers to develop updated engines/vehicles to satisfy the proposed demands of environmental policy levels. To achieve the expected demands of emissions coming out from an engine exhaust not only with the help of converters in the exhaust pipe line but also the emissions should be controlled during burning of fuel with air in the ignition chamber itself. The controlled combustion of fuel and air requires not only the control fuel injection timing with duration of injection and tune up of the complete fuel injection system with hardware components of ECU but also requires the control of ignition timing. The complete electronic control for petrol engine with direct injection unit is required to communicate between PC and an engine. CAN with SPI interface is used to communicate the electronic control unit with engine

Scalar predictors of premixed gas ignition by a suddenly-starting hot jet

Hot-jet ignition is usually designed to reduce emissions in lean-burn combustion engines, and has potential in enabling novel pressure-gain combustion. Inspired by our experimental observations related to wave-rotor combustion chamber ignition, this work employs a numerical method to examine the sudden injection of a hot jet into a quiescent mixture of CH4–H2-air and the subsequent ignition. The goal is to provide the range of thermo-physical scalars that are supportive of successful ignition. The evolution of scalar fields is evaluated using large-eddy simulation (LES). The temporal evolution of mixture fraction, the squared gradient of mixture fraction (as indicative of scalar dissipation rate), strain rate, and intermediate species are investigated in order to find the appropriate physical conditions which support ignition. Independent distribution of stain rate and squared gradient of mixture fraction, especially in the leading head vortex, shows the necessity of correlated scalar analysis of the ignition process. Experimental and numerical methods are then employed to provide the qualitative and quantitative understanding of ignition process for fuels with two distinct hydrogen contents. Results show the meaningful difference in spatial distribution of local ignition as hydrogen content of the fuel increases.

Synchronized Electromechanical Shock Wave-Induced Bacterial Transformation.

We report a simple device that generates synchronized mechanical and electrical pressure waves for carrying out bacterial transformation. The mechanical pressure waves are produced by igniting a confined nanoenergetic composite material that provides ultrahigh pressure. Further, this device has an arrangement through which a synchronized electric field (of a time-varying nature) is initiated at a delay of ≈85 μs at the full width half-maxima point of the pressure pulse. The pressure waves so generated are incident to a thin aluminum–polydimethylsiloxane membrane that partitions the ignition chamber from the column of the mixture containing bacterial cells (Escherichia coli BL21) and 4 kb transforming DNA. A combination of mechanical and electrical pressure pulse created through the above arrangement ensures that the transforming DNA transports across the cell membrane into the cell, leading to a transformation event. This unique device has been successfully operated for efficient gene (∼4 kb) transfer into cells. The transformation efficacy of this device is found comparable to the other standard methods and protocols for carrying out the transformation.

Flame Propagation in a Narrow Closed Channel: Effects of Aspect Ratios, Blockage Ratio, and Mixture Reactivity on Flame Speed and Pressure Dynamics

ABSTRACT A set of experiments is conducted to study flame acceleration in a narrow rectangular cross-section channel in order to examine the effects of mixture reactivity, channel height, and blockage ratio (BR). The channel had an ignition chamber at one end and a dump chamber at the opposite end. The initial conditions are mixtures of hydrogen-air at 1 bar and 293 K. Five different compositions of 10, 20, 30, 40, and 50% hydrogen volume fraction in air are studied. The rectangular chamber is 500 mm long and 40 mm in width, with an adjustable height from 2 to 10 mm. To study the relation between channel height and BR, combustion behaviors with three different B.R. (BR of 0.1, 0.5, and 0.9), 5 different obstacle sizes, and different channel heights (from 2–10 mm) are presented. Pressure waves are monitored with seven fast response pressure transducers placed along the chamber, and the flame propagation is observed with a high-speed Schlieren imaging system. There was no detonation observed during this series of experiments. The results show that the flame propagation is affected by both the channel dimensions and the obstacles, with a maximum flame velocity achieved for partially obstructed channels. The evolution of the flame’s propagation and the pressure dynamics through the various obstructed and unobstructed channels, including the dynamics contributed by the ignition and dump chamber, are discussed.

Lean-burn CNG engine with ignition chamber: from the idea to a running engine

Current and further developing CO2- and emission regulations worldwide and the competition to full electric mobility deliver a chal-lenge for internal combustion engines in general. A state of the art solution is the use of natural gas mainly contending methane to reduce CO2 significantly and to offer lowest emission levels. The EU-funded project GasOn developed engine concepts to fully exploit the advantages of CNG. This article describes the development of an innovative, monovalent engine dedicated to Compressed Natural Gas (CNG) and characterised by the lean burn concept and the innovative pre-chamber combustion.

An Experimental Investigation on Glass /Carbon Fibre Hybrid Composite Material

In this study, the aeronautical and aerospace standard rocket injector have been analyzed with different aerodynamic parameters in order to understand the performance of the injectors in different atmospheric conditions. These injectors are the primary device to inject the fuel form the manifold to the ignition chamber. It creates the requited pressure, mass flow rate and the flow velocity in order to generate atomization of the fuel molecule. This atomization of the micro fuel droplet create fuel spray angle, which indeed produce high fuel burn rate. The injector with improper design may cause, unburnt fuel molecule, which will turn to carbon deposit inside the mixture chamber and gets corroded. In this paper the author has investigated the injector flow rate with respect to the injector throat area. The fuel used in this cold flow test study is commercial kerosene. The result indicates that, as the pressure at the inlet increases, the spray cone angle, mass flow rate and flow velocity also increases gradually. This numerical analysis where performed for various injector throat area with respect to various pressure rate from 20-100 psi. The best injector with all aerodynamic properties have been selected. This research paper will be benefit for the researchers and aeronautical industries, which help them to study the different aerodynamic parameter change in various injector throat area.

The Performance Evaluation of Injector using Numerical Technique

In this study, the aeronautical and aerospace standard rocket injector have been analyzed with different aerodynamic parameters in order to understand the performance of the injectors in different atmospheric conditions. These injectors are the primary device to inject the fuel form the manifold to the ignition chamber. It creates the requited pressure, mass flow rate and the flow velocity in order to generate atomization of the fuel molecule. This atomization of the micro fuel droplet create fuel spray angle, which indeed produce high fuel burn rate. The injector with improper design may cause, unburnt fuel molecule, which will turn to carbon deposit inside the mixture chamber and gets corroded. In this paper the author has investigated the injector flow rate with respect to the injector throat area. The fuel used in this cold flow test study is commercial kerosene. The result indicates that, as the pressure at the inlet increases, the spray cone angle, mass flow rate and flow velocity also increases gradually. This numerical analysis where performed for various injector throat area with respect to various pressure rate from 20-100 psi. The best injector with all aerodynamic properties have been selected. This research paper will be benefit for the researchers and aeronautical industries, which help them to study the different aerodynamic parameter change in various injector throat area.

Air and Fuel Flow Interaction in Combustion for Various Injector Locations

Oil based fills assume a crucial part in fast consumption of regular vitality sources alongside expanding request and furthermore real donors of air poisons. Real segment of the present vitality request in India is being met with non-renewable energy sources. Consequently ample opportunity has already past that substitute powers for motors ought to be gotten from indigenous sources. As India is a rural nation, there is a wide extension for the generation of vegetable oils (both palatable and non-eatable) from various oil seeds. The present work concentrated just on non-palatable oils as fuel for motors, as the consumable oils are in awesome request and excessively costly. The past work uncovered that employments of vegetable oils for motors set up of diesel were researched. In spite of the fact that the concerned scientists suggested the utilization of vegetable oils in diesel motors, there was no proof of any down to earth vegetable oil source motors. The present examinations are arranged after an intensive audit of writing around there. Analyses are done in a more prevalent petter sort single barrel, water cooled motor. Significant issues related with vegetable oils are higher viscosities, bring down warming esteems, ascend in stoichiometric fuel air proportion and warm splitting. The creator has concentrated on use of five non-palatable oils, their mixes with diesel and individual Methyl esters in diesel motors. The perfect oil mixes with diesel were warmed before going into ignition chamber. The warming quality relies upon the expansion in level of flawless oils in blend to diminish the consistency of the fuel. The execution parameters of the test motor Viz. Brake warm productivity, Volumetric proficiency are diminished, Brake particular fuel utilization and Exhaust gas temperature are expanded for every slick oil contrasted with diesel. Emanation parameters of motor, for example, Carbon monoxide, Carbon dioxide, Un-consumed hydrocarbons and Smoke are expanded, yet Nitrogen oxides are diminished for every single slick oil and their mixes contrasted with diesel. This variety is seen because of high thickness combined with bring down warming estimation of the powers. Every single flawless oil are changed over into their separate methyl esters through trans-desertification process. In this procedure, the execution parameters of motor, for example, Brake warm proficiency and volumetric productivity are marginally diminished, Brake particular fuel utilization and Exhaust gas temperature are expanded contrasted with diesel for all bio-diesels. Emanation parameters of motor, for example, Carbon monoxide, Carbon dioxide, Un-consumed hydrocarbons and Smoke are decreased, however Nitrogen oxides expanded for all bio-diesels contrasted with diesel. This pattern is seen because of finish ignition of the bio-diesels, as the consistency is lessened. From the experimentation, it is watched that 25% of perfect oil blended with 75% of diesel is the most appropriate mix, without warming and with no alteration of the motor. Methyl ester of Linseed oil is the better performing fuel because of better execution and lower outflows contrasted with other picked methyl ester.

Combustion Chamber Analysis Using CFD for Operation Condition

The gas turbine ignition chamber is a standout amongst the most basic segments to be unlined, in light of the fact that it must guarantee a steady operation in an extensive variety of air/fuel proportion and load. Among a few estimations engaged with the plan of a burning chamber, the reference region is the most vital physical parameter, particularly by the considerable effect on different measurements. As a rule, this parameter must be ascertained from an investigation of the impediments forced both compound responses and optimal design, i.e., in light of ignition process prerequisites and most extreme weight drop passable in the burning chamber, individually. In this way, the point of this paper is research the impact of the reference territory in the speed profile, in the temperature conveyance, in the blending procedure and in the fire conduct, as per the reference zone utilized as a part of the burning chamber. These numerical investigations were completed utilizing ANSYS CFX, contrasting them and the base esteem figured by Lefebvre [5], for a thermodynamic cycle of 600 kW gas turbine motor, conduced in Gate Cycle program. At last, it can be inferred that a few changes in the reference region figured by Lefebvre [4] creates better outcomes, particularly by enhancing the consuming procedure and the conduct of the fire.

A numerical study of the combustion and jet characteristics of a hydrogen fueled turbulent hot-jet ignition (THJI) chamber

Turbulent hot-jet ignition (THJI) is an advanced ignition enhancement technology which can potentially overcome the problem associated with lean burn combustion. The present study makes an effort on the comprehensive understanding of a hydrogen fueled THJI chamber with various pre-chamber spark locations. Computational fluid dynamics (CFD) simulations are performed using an in-house code based on the KIVA-3V release 2 program coupled with an in-house chemical solver. A detailed chemical kinetics mechanism with 10 species and 19 reversible reactions is used for the H2/air mixture in both the pre-chamber and the main chamber. The results show that moving the spark ignition location farther from the orifice significantly reduces the 0−10% mass fraction burn period. By analyzing the local Mach number, turbulence kinetic energy and turbulence length scale, the compressibility and turbulence level of the jet flow are evaluated. Further analysis of the OH mass fraction distribution identifies three regions in the hot jet, i.e. extinction region, just-igniting region and combustion region. A critical Damköhler number of 0.3 is determined to separate the extinction region from the other regions. Meanwhile, transition Damköhler numbers ranging from 0.3 to 0.6 are determined in the just-igniting region.

Understanding conflagration of one-story mud-brick structures: an experimental approach

Many Near Eastern destruction layers are characterized by burnt, partially collapsed, mud-brick structures. Despite the prominence of these layers in archaeological field research, the processes that generated these layers are little understood. In order to explain field observations and identify patterns that may be useful for archaeological interpretation, experimental burning of miniature single-story mud-brick structures was conducted. Two types of structures—covered by vegetal roofs or by mud-plastered roofs—were conducted. Each experiment was duplicated. Temperatures in chambers, walls, roofs, and floors were recorded continuously. Bricks, floor, and roof sediments were sampled and analyzed by Fourier transform infrared (FTIR) spectroscopy after the burned structures cooled down. The results showed that ignition of vegetal roofs does not produce a pattern recognizable in Near Eastern destruction layers, while chamber ignition within mud-plastered roofed structures produces patterns that most resemble field evidence. These include (a) upper portions of walls and mud roofs witness temperatures above 500 °C resulting in a mineralogical change that is identifiable by FTIR, (b) no significant heat in floor deposits, (c) higher temperatures in upper parts than the bottom portions of walls, (d) external walls experience heat diffusion to the outside environment and do not burn through, and (e) internal walls can burn through. The directly measured temperatures correlate with reconstructed temperatures via FTIR and with brick color patterns. Future field research should explore color patterns in cross-sections of mud-brick walls and apply FTIR spectroscopy to reconstruct distribution of heat across destruction levels.

Ignition of a sequential combustor: Evidence of flame propagation in the autoignitable mixture

Ignition of the second stage in a lab-scale sequential combustor is investigated experimentally. A fuel mixing section between jet-in-cross-flow injection and the second stage chamber allows the fuel and vitiated, hot cross-flow to partially mix upstream of the main heat release zone. The focus of the present work is on the transient ignition process leading to a stable flame in the second stage. High-speed OH-PLIF as well as OH chemiluminescence imaging is applied to obtain complementary planar and line-of-sight integrated information on the ignition. We find experimental evidence for the co-existence of two regimes dominating the chamber ignition, i.e. autoignition and flame propagation. As the mass flow of the dilution air injected downstream of the first stage is increased (i.e. mixing temperatures in the fuel mixing section are decreased), we transition from an autoignition to a flame propagation dominated regime. Hysteresis in the ignition behavior is observed indicating that the first stage in a sequential combustor may be operated at leaner conditions than required for ignition of the second stage. The time traces of integral heat release obtained simultaneously with a photomultiplier tube show distinct features depending on the dominating regime, which is important for high-pressure testing with limited optical access.

Ignition of ultra-lean premixed hydrogen/air by an impinging hot jet

The ignition characteristics of a hot turbulent jet impinging on a flat plate surrounded by an ultra-lean premixed H2/air was studied both experimentally and numerically. The hot turbulent jet was generated by burning a small quantity of stoichiometric H2/air mixture in a separate small volume called the pre-chamber. The higher pressure resulting from pre-chamber combustion pushed the combustion products into the main chamber through a small nozzle (0.75–4.5 mm in diameter) in the form of a hot turbulent jet, which then impinged on a flat plate. Six different plates with varying impinging heights and angles were used. Two important parameters controlling the impinging characteristics of the jet, the ratio of the impinging distance to the nozzle diameter, H/D and the impinging angle, θ were examined. Simultaneous high-speed Schlieren and OH∗ chemiluminescence imaging were applied to visualize the jet penetration/impinging and ignition process inside the main combustion chamber. Results illustrate the existence of two distinct types of ignition mechanisms. If the impinging distance is short and the hot turbulent jet hits the plate with high enough momentum, the temperature increases around the stagnation point and ignition starts from this impinging region. However, if the impinging distance is long, the hot turbulent jet mixes with the ambient unburned H2/air in the main chamber and ignites the mixture at the upstream from the plate. For such type of ignition, the impinging plate has a minimum role on main chamber ignition. Employing the stagnation point ignition, a leaner limit of H2/air in the main chamber was achieved. Numerical modeling of the turbulent hot jet impingement process was carried out to explain the impinging jet ignition mechanism. It was found that H/D ratio was the controlling parameter between the two ignition mechanisms. The limiting H/D ratio was found to be 21.6, below which ignition occurred via jet impingement. Unlike the H/D ratio, the impinging angle did not affect the ignition mechanism; however, it affected the main chamber burn time.

A numerical study on effects of pre-chamber syngas reactivity on hot jet ignition

Ignition by a pre-chamber generated hot jet is a promising technology to reduce NOx emissions through extending lean burn limits. However, the role of the pre-chamber fuel reactivity in the main chamber ignition still remains unclear. In the present study, effects of the pre-chamber fuel reactivity on ignition of mixture in a main chamber by the hot jet, which is generated by the combustion of syngas in the pre-chamber, are numerically investigated. In the investigation, different ratios of CO/H2 of syngas are considered under a thermally-equal condition. CFD simulations are performed using the code based on the KIVA-3V release 2 program coupled with an in-house developed chemical solver. A detailed chemical kinetics mechanism with 15 species and 41 reactions is adopted for the hydrogen and syngas oxidation. The hot jet ignition delay time is characterized by the maximum rate-of-change of the pressure in the main chamber. For the combustion initiation process, three stages are identified: ignition stage (stage I), flame development stage (stage II), and flame propagation stage (stage III). Significant effects of fuel reactivity are only observed on stage I that the ignition delay time considerably increases with increasing CO/H2 ratio. Further analyses of the local temperature of the hot gas and some important elementary reactions indicate that the low reaction rate of carbon monoxide oxidation (R22: CO + OH = H + CO2) causes incomplete fuel conversion in the orifice due to insufficiently available time for the reactions . The fuel conversion analysis confirms that the small-diameter orifice effect is the main reason for hot jet temperature drops under low pre-chamber syngas reactivity conditions, exhibiting as inhibiting effects on stage I.

Investigation of Gas Detonation in Over-Rich Mixtures of Hydrocarbons with Oxygen

Detonation in mixtures of acetylene, ethylene, and propylene with oxygen in the range of fuel component concentrations with possible formation of carbon condensate in detonation products is studied both experimentally and theoretically. In contrast to the traditional method of studying detonation in a quiescent mixture located in a closed tube, the present investigations are performed in a tube with an open end (for exhaustion of detonation products) under the conditions of separate injection of the components and their mixing after injection into the detonation tube through the ignition chamber. The components are injected into the tube from a computercontrolled multichannel system of gas injection of the CCDS2000 detonation spraying setup. The detonation cell size and detonation velocity are measured; these parameters are also calculated by the BEZOPASNOST (SAFETY) computer program. A comparison of the computed and experimental dependences testifies to a complicated character of transformation of detonation products from a purely gaseous to heterogeneous state and to its effect on the detonation wave.

Analysis of Combustion Process in Industrial Gas Engine with Prechamber-Based Ignition System

Application of a pre-combustion chamber (PCC) ignition system is one of the methods to improve combustion stability and reduce toxic compounds emission, especially NOx. Using PCC allows the operation of the engine at lean combustion conditions or the utilization of low calorific gaseous fuels such as syngas or biogas. The paper presents the results of an experimental study of the combustion process in two stroke, large bore, stationary gas engine GMVH 12 equipped with two spark plugs (2-SP) and a PCC ignition system. The experimental research has been performed during the normal operation of the engine in an industrial compression station. It was observed that application of PCC provides less cycle-to-cycle combustion variation (more than 10%) and nitric oxide and carbon monoxide emissions decreased to 60% and 26% respectively. The total hydrocarbon (THC) emission rate is 25% higher for the engine equipped with PCC, which results in roughly two percent engine efficiency decrease. Another important criterion of engine retrofitting was the PCC location in the engine head. The experimental results show that improvement of engine operating parameters was recorded only for a configuration with one port offset by 45° from the axis of the main chamber. The study of the ignition delay angle and equivalence ratio in PCC did not demonstrate explicit influence on engine performance.

Experimental Investigation of the Flame Propagation and Flashback Behavior of a Green Propellant Consisting of N2O and C2H4

Regarding the research on alternatives for monopropellant hydrazine, several so called green propellants are currently under investigation or qualification. Aside others, the DLR Institute of Space Propulsion investigates a N2O/C2H4 premixed green propellant. During the research activities, flashback from the rocket combustion chamber into the feeding system has been identified as a major challenge when using the propellant mixture. This paper shows the results of ignition experiments conducted in a cylindrical, optical accessible ignition chamber. During the ignition and flame propagation process, pressure, temperature and high-speed video data were collected. The high speed video data were used to analyze the flame propagation speed. The obtained propagation speed was about 20 m/s at ignition, while during further propagation of the flame speeds of up to 120 m/s were measured. Additionally, two different porous materials as flame arresting elements were tested: Porous stainless steel and porous bronze material. For both materials Peclet numbers for flashback were derived. The critical Peclet number for the sintered bronze material was around 20, while for the sintered stainless steel the critical Peclet number seems to be larger than 40. Due to the test results, sintered porous materials seem to be suitable as flashback arresters.

Flame propagation model for a rotary Atkinson cycle SI engine

The rotary Atkinson cycle engine includes two modes of combustion: combustion initiation and propagation in ignition chamber and then flame jet entrainment and propagation in expansion chamber. The turbulent flame propagation model is a predictive model for SI engines which could be developed for this type of combustion for the rotary Atkinson engine similar to the congenital engine with pre-chamber; in split combustion chamber SI engines, small amount of fuel is burned in pre-chamber while the fuel burned in ignition chamber of rotary Atkinson cycle is considerable. In this study a mathematical modeling of spherical flame propagation inside ignition chamber and new combined conical flame and spherical flame propagation model of a new two-stroke Atkinson cycle SI engine will be presented. The mathematical modeling is carried out using two-zone combustion analysis and the model also is validated against experimental tests and compared with previous study using non-predictive Weibe function model.