Ignition Energy Research Articles

The Effects of Pilot Structure on the Lean Ignition Characteristics of the Internally Staged Combustor

In order to explore the influence of pilot structure on the lean ignition characteristics in a certain type of internally staged combustor, the current study was conducted on the effects of the auxiliary fuel nozzle diameter, the rotating direction of the pilot swirler, and the swirl number on the lean ignition fuel–gas ratio limit, combining numerical simulation and experimental validation. The optimization potential of the mixing structure of this type of internally staged combustor was further explored. It indicated that the lean ignition fuel–gas ratio limit was significantly influenced by the diameter of the auxiliary fuel nozzles the swirl number of the pilot swirler and the combination of the same rotating direction for both pilot swirlers, while the mass flow rate of air was constant. Increasing the diameter of the auxiliary fuel path nozzles (0.4~0.6 mm) and having excessively higher or lower swirl numbers of the pilot module primary swirlers are not conducive to broadening the lean ignition boundary. Compared with the two-stage pilot swirler with the same rotation combination, the fuel–gas ignition performance of the two-stage pilot swirler with the opposite rotation combination is better. Under the typical working conditions (the air mass flow rate is 46.7 g/s and the ignition energy is 4 J), for a pilot swirler with a rotating direction opposite to the main swirler, the diameter of the auxiliary fuel nozzles is 0.2 mm, the swirl number of first-stage of pilot swirler is 1.4, and the lean ignition fuel–air ratio was reduced to 0.0121, which is 32.78% lower than the baseline scheme, which further broadens the lean ignition boundary of the centrally staged combustion chamber.

Study on the typical influencing factors of gasoline vapor explosion in a confined space

To explore the influencing factors of explosion accidents caused by gasoline leakage in a confined space, the effects of ignition delay time, ignition energy, initial pressure, initial temperature and mass concentration on gasoline vapor explosion pressure and flame propagation velocity were investigated using a 20 L spherical explosion vessel. The dynamic explosion temperature distribution of gasoline vapor was mapped by the colorimetric thermometry, and the results demonstrated that the optimal ignition delay time, ignition energy and mass concentration of gasoline vapor in the confined space were 100 ms, 100 J and 160 g/m3, respectively. When the initial pressure was 0.11 MPa, the deflagration pressure of gasoline vapor explosion reached the maximum of 1.08 MPa. The influence of the increasing initial temperature on the maximum explosion pressure rise rate of gasoline was greater than that on the explosion pressure and combustion duration. When the mass concentration of gasoline vapor was 160 g/m3, the flame propagation velocity and average temperature both obtained their maximum values of 1.23 m/s and 2271 K, respectively. The research results were conductive to reveal the mechanism of explosion accidents caused by gasoline leakage in a confined space, and may provide theoretical guidance for safe storage and transportation of gasoline.

A review of chemical kinetic mechanisms and after-treatment of amino fuel combustion.

Ammonia is a highly promising carbon-neutral fuel. The use of ammonia as a fuel for internal combustion engines can reduce fossil energy consumption and greenhouse gas emissions. However, the high ignition energy required for ammonia and the slow flame propagation rate result in low combustion efficiency when ammonia is used directly in internal combustion engines. The combination of ammonia with highly reactive fuels improves combustion quality and increases efficiency. However, the combustion of these combined fuels generates particulate matter, CO, hydrocarbon, and significant amounts of NOx. Therefore, pollutant emissions must be reduced through after-treatment technologies. In this paper, a series of combustion and post-treatment challenges faced by amino fuel combustion in internal combustion engines are extensively discussed and the combustion reaction mechanisms of different amino fuels are also analyzed. The paper then reviews five key technologies applicable to the reprocessing of amino fuels, including selective catalytic reduction, selective catalytic reduction filter technology, electrochemical methods for NOx removal, direct catalytic decomposition of N2O, and ammonia sliding catalysts. An in-depth discussion of the catalytic materials and reaction mechanisms involved in these technologies is also provided in this paper. Finally, the paper summarizes the main technical challenges that must be addressed for the future application of amino fuels in internal combustion engines. These discussions can serve as an essential reference for developing and applying critical technologies for combustion control and pollutant treatment of amino fuels.

Review of Pre-Ignition Research in Methanol Engines

Methanol can be synthesized using green electricity and carbon dioxide, making it a green, carbon-neutral fuel with significant potential for widespread application in engines. However, due to its low ignition energy and high laminar flame speed, methanol is susceptible to hotspot-induced pre-ignition and even knocking under high-temperature, high-load engine conditions, posing challenges to engine performance and reliability. This paper systematically reviews the manifestations and mechanisms of pre-ignition and knocking in methanol engines. Pre-ignition can be sustained or sporadic. Sustained pre-ignition is caused by overheating of structural components, while sporadic pre-ignition is often linked to oil droplets entering the combustion chamber from the piston crevice. Residual exhaust gas trapped within the spark plug can also initiate pre-ignition. Knocking, characterized by pressure oscillations, arises from the auto-ignition of hotspots in the end-gas or, potentially, from deflagration-to-detonation transition, although the latter requires further experimental validation. Factors influencing pre-ignition and knocking, including engine oil, in-cylinder deposits, structural hotspots, and the reactivity of the air–fuel mixture, are also analyzed. Based on these factors, the paper concludes that the primary approach to suppressing pre-ignition and knocking in methanol engines is controlling the formation of pre-ignition sources and reducing the reactivity of the air–fuel mixture. Furthermore, it addresses existing issues and limitations in current research, such as combustion testing techniques, numerical simulation accuracy, and the mechanisms of methanol–oil interaction, and offers related recommendations.

A Systematic Analysis of Progress in Doping Combustion Characterization of Ammonia-Fueled Engines

In the global environment of carbon emission reduction, diesel engine emissions of carbon dioxide, nitrogen oxide and other harmful gases seriously polluting the environment has been boycotted by governments around the world. Ammonia, as a clean, environment-friendly, easy-to-transport green energy, has broad application prospects. However, due to its poor combustion performance and high calorific value, there are some limitations in its application. In this paper, the mechanism, combustion characteristics and emission characteristics of an engine fueled with ammonia-hydrogen fuel and ammonia-carbon-based fuel are reviewed. Hydrogen fuel and diesel fuel with low ignition energy and fast laminar flame spread characteristics, can make up the shortage of pure ammonia fuel, reduce nitrogen oxide emissions. Among them, hydrogen ammonia fuel has become the mainstream and the most promising fuel, compared with pure ammonia fuel and ammonia diesel fuel has the advantages of clean, low transport costs, fast combustion and so on, will become the future engine main application fuel.

Experimental and numerical investigation of abnormal combustion phenomena in high-performance hydrogen direct-injection engine operated in stochiometric conditions

Nowadays the use of Hydrogen (H2) within Internal Combustion Engine (ICE) represents a valuable solution also for high-performance applications since it allows carbon free combustion process preserving, at the same time, the driving experience of the engines fuelled with conventional fuels. On the other side, the low ignition energy and the high flammability range may lead to a high probability of abnormal combustion events especially at high engine loads. Therefore, this work aims at investigating the occurrence of knock and pre-ignition phenomena in a high-performance Direct Injection (DI) single cylinder Spark Ignition (SI) engine through the synergistic use of numerical simulations and experimental activities. A 3D-CFD model was calibrated against a set of experimental measurements. The engine model showed satisfactory predictive capabilities with a good matching with the experimental in-cylinder pressure traces. This virtual test rig was then used to investigate the impact of a different coolant temperature and different injector recess in terms of knock and pre-ignition tendency, and most of all, to define a robust simulation methodology to estimate the risk of hydrogen abnormal combustion events.

Present understanding of ignition and gain using indirect-drive inertial confinement fusion target designs on the U.S. National Ignition Facility

Abstract For many decades, the running joke in fusion research has been that `fusion' is thirty years away and always will be. Yet, these past few years we find ourselves in a position where we can now talk about the milestones of burning plasmas, fusion ignition, and target energy gain greater than unity (scientific breakeven) in the past tense. Fusion is no longer a joke! Yet getting to fusion ignition, the tipping-point of thermonuclear instability resulting in an explosive increase in ion thermal temperature and fusion reaction-rate, and scientific breakeven (target gain, $G_{target}=$ fusion yield/deposited laser energy $> 1$, in the laser-driven inertial confinement fusion context) has not been easy. In this publication we discuss our present understanding of the physics and technological challenges surrounding ignition and Gain as well as highlight some outstanding problems that still need resolution.

Composite Structure MgB2@KNO3 With Multi-Effect Synergies to Improve Combustion Performance and Energy Release of B

ABSTRACT With the deepening of research, boron compounds have gradually gained favor among researchers due to their high calorific value and excellent ignition and combustion performance. In this paper, MgB2@KNO3, which exhibits excellent ignition and combustion properties, was synthesized using ultrasonic dispersion and magnetic stirring. The improved ignition mechanism and energy release characteristics of MgB2@KNO3 were elucidated using DSC/TG, SEM, EDS, XRD, and optical characterization, in conjunction with computational results from NASA-CEA. The surface activation energy and ignition energy of MgB2@KNO3 are 35.7% and 25%, respectively, lower than those of conventional B/KNO3 mixtures. Compared to the mixed sample of B/KNO3, the heat release of MgB2@KNO3 increased by 72.4%. The synergistic and effective interactions between oxygen, magnesium vapor, and boron in MgB2@KNO3 systems result in efficient energy release performance, making MgB2@KNO3 a promising material for use as a high-energy fuel in propellants, explosives, and pyrotechnic products.

INFLUENCE OF HYDROGEN ON COMBUSTION PROCESS AND ON EMISSION PARAMETERS IN THE RCCI ENGINE

Thanks to its carbon-free nature, it is possible to say that hydrogen is a potential fuel for future automotive systems. Its main favourable properties include high burning rate, wide range of flammability and low ignition energy. In combination with hybrid electric technology, the hydrogen combustion engine has the potential for further development with the goal of maximum efficiency in energy conversion. For more efficient hydrogen combustion, a dual fuel injection hybrid system is designed, where one injector is designed for direct hydrogen injection into the engine cylinder and the other injector is supply fuel to the engine's intake pipe. The greatest challenge is development of a control algorithm intended for management of the combustion process in hydrogen engine and optimization of fuel injection divided into individual doses.

Effects of injection timing on combustion and mixture formation of a methanol direct injection engine equipped with a small volume passive pre-chamber

Effects of injection timing on combustion and mixture formation of a methanol direct injection engine equipped with a small volume passive pre-chamber

Thermal performance, mechanical sensitivity and low speed impact ignition characteristics of PTFE based aluminum alloy active materials

Abstract To solve the problems of low energy release efficiency, slow reaction rate, and long ignition response time of Al/PTFE, the idea of introducing aluminum zirconium alloy powder instead of traditional Al powder is proposed in this paper. By utilizing its high calorific value, high enthalpy value, and high activity, the reaction rate and energy of PTFE based aluminum alloy active materials are promoted and enhanced, which ultimately improved and enhanced the energy release efficiency. Aluminium zirconium nickel based active materials were developed using aluminum zirconium alloy powder, and their thermal properties and mechanical sensitivity were tested. The temperature isostatic pressing preparation process based on prefabricated column was also explored. The research results indicate that the Al/Zr/Ni/PTFE formula has a higher exothermic value when Al reacts with PTFE, and it triggers a reaction in the Al/Zr/Ni alloy powder during the reaction stage; The addition of aluminum zirconium alloy powder reduces the impact and friction sensitivity of Al/PTFE materials, with Al/Zr/Ni/PTFE aluminum alloy active materials showing a slight improvement; The ignition response and energy release characteristics of Al/Zr/Ni/PTFE aluminum alloy active materials under hammer impact are significantly improved compared to Al/PTFE. Therefore, the aluminum zirconium nickel based active material system is one of the important research directions in the future.

Research on sensitivity experiment and RF dudding assessment of EED

Abstract This article refers to radio frequency(RF) sensitivity test and RF dudding assessment method of MIL-STD-1576, select the two kinds of typical bridge-wire electric explosive device(EED) to carry on RF sensitivity experiments and direct current(DC) sensitivity experiments before and after exposure in radio frequency environment, analyze and compare EED DC sensitivity on the impact of 10% RF sensitivity, and assessing the RF dudding possibility on EED. Test results shows that made 10% RF ignition sensitivity as detonation standard, both of two kinds of samples ignited. 4 out of 40 in 1# sample ignited and 3 out of 40 in 2# sample ignited. And detonation test of 10% RF ignition energy did not change the DC ignition feature of two kinds of EED (confidence is 95%). Preliminary study RF dudding assessment method, provide test data and testing methods for deeply researching the RF dudding experiment and assessment method on EED.

Neat ammonia use in a heavy-duty diesel engine converted to spark ignition focused on lean operation

Neat ammonia use in a heavy-duty diesel engine converted to spark ignition focused on lean operation

(Invited) Development of Fiber-Optic Hydrogen Sensor Using Platinum-Supported Tungsten Trioxide-Silica Composite Film

Hydrogen has been attracting attention in recent years as a clean energy carrier that can be easily obtained by converting water into hydrogen by using various renewable natural energy resources and enable to generate energy through chemical reaction without emitting pollutants. While it has these advantages, hydrogen gas is characterized by two dangerous properties: low ignition energy and wide combustion range. Furthermore, leakage of hydrogen is difficult to detect because of its properties such as colorless, transparent, and odorless. Therefore, a leakage detection system is indispensable for the safe handling of large amounts of hydrogen energy carrier. So far, various high-performance sensors have been proposed and practically utilized. However, developments of sensor devices which can be operated at room temperature are still challenge. Furthermore, there are significant needs for distributed measurements for leakage detection of large-scale hydrogen infrastructure. In this study, fiber-optic techniques that can easily and inexpensively capture hydrogen leakage in a wide spatial area are focused to realize a line-type hydrogen sensor. In order to develop such kind of fiber optic hydrogen sensor, platinum-supported tungsten oxide film and tungsten-silica composite film were utilized as hydrogen-sensitive materials whose optical properties are significantly change through the reaction with hydrogen. A plastic-clad quartz core fiber with a core diameter of 200 μm and a cladding diameter of 230 μm (H-PCF: manufactured by Sumitomo Electric Industries) was used. In order to immobilize the hydrogen-sensitive cladding, the cladding was removed using an organic solvent. Then, the hydrogen-sensitive materials were directly coated on fiber core and immobilized by calcination in air at different temperatures. The sensing mechanism is based on the evanescent field interaction in the hydrogen sensitive clad region. As a first step, transmission spectra of sensing film itself under air and hydrogen atmosphere were evaluated for optimizing wavelength of the light source used in the sensor system. The transmittance of the sensitive film decreased in the range of wavelengths above about 500 nm after exposure to pure hydrogen, and the decrease at 1300 nm was greater than that at 850 nm, suggesting that the 1300 nm wavelength is more likely to extract changes in optical properties caused by the response (Fig. 1). Then, fiber optic sensor device was fabricated, and the amount of propagating light was measured using LED light sources at wavelengths of 850 nm and 1300 nm. In the case of using the light source with a wavelength of 1300 nm, the light attenuation rate with respect to the hydrogen response was nearly twice and the response speed was faster, compared with those at 850 nm. Therefore, it was concluded that a light source with a wavelength of 1300 nm for measurement of propagating light intensity is suitable for monitoring hydrogen leakage. Figure 1

Combustion characteristics of ammonia-hydrogen mixture with turbulent jet ignition

Combustion characteristics of ammonia-hydrogen mixture with turbulent jet ignition

Investigating the impacts of charge composition and temperature on ammonia/hydrogen combustion in a heavy-duty spark-ignition engine

Investigating the impacts of charge composition and temperature on ammonia/hydrogen combustion in a heavy-duty spark-ignition engine

The impact of ignition and activation energy distribution on the combustion and emission characteristics of diesel-ammonia-natural gas engines

The impact of ignition and activation energy distribution on the combustion and emission characteristics of diesel-ammonia-natural gas engines

Investigation of the hydrogen pre-ignition induced by the auto-ignition of lubricating oil droplets

Investigation of the hydrogen pre-ignition induced by the auto-ignition of lubricating oil droplets

Research on the Calculation Method and Diffusion Pattern of VCE Injury Probability in Oil Tank Group Based on SLAB-TNO Method

Accidental leakage from oil–gas storage tanks can lead to the formation of liquid pools. These pools can result in vapor cloud explosions (VCEs) if combustible vapors encounter ignition energy. Conducting accurate and comprehensive consequence analyses of such explosions is crucial for quantitative risk assessments (QRAs) in industrial safety. In this study, a methodology based on the SLAB-TNO model to calculate the overpressure resulting from a VCE is presented. Based on this method, the consequences of the VCE accident considering the gas cloud concentration diffusion are studied. The probit model is employed to evaluate casualty probabilities under varying environmental and operational conditions. The effects of key parameters, including gas diffusion time, wind speed, lower flammability limit (LFL), and environment temperature, on casualty diffusion are systematically investigated. The results indicate that when the diffusion time is less than 100 s, the VCE consequences are significantly more severe due to the rapid spread of the gas cloud. Furthermore, increasing wind speed accelerates gas dispersion, reducing the spatial extent of casualty isopleths. The LFL is shown to have a direct impact on both the mass and diffusion of the flammable gas cloud, with higher LFL values shifting the explosion’s epicenter upward. The environmental temperature promotes gas diffusion in the core area and increases the mass of the combustible gas cloud. These findings provide critical insights for improving the safety protocols in oil and gas storage facilities and can serve as a valuable reference for consequence assessment and emergency response planning in similar industrial scenarios.

Influence of stearate dry coating on ibuprofen powder: What about the combustibility?

Influence of stearate dry coating on ibuprofen powder: What about the combustibility?