Ignition System Research Articles

Overview and recent applications of the miniaturized HiPoLas ignition system

The requirements of the space industry for reusable, low cost or clustered engines have triggered high interest in a laser ignition system capable of multi-point ignition. The miniaturized SAL HiPoLas laser ignition system developed for single-point direct-plasma ignition has recently been enhanced towards a fiber coupling, multiplexing, and distribution system. A brief history of the HiPoLas development with an overview of the latest, highly miniaturized generation V ignition system is shown. Applications of the miniaturized ignition system, summarizing more than 10 years of development in the field of rocket engine laser ignition, as well as the first results of a recently developed prototype of a fiber distribution system, based on diffractive optical elements, are presented.

Research on jet ignition phases and control parameters in an active pre-chamber optical engine under ultra-lean combustion conditions

The active pre-chamber (APC) jet ignition system is one of the primary technologies for achieving ultra-lean combustion and high thermal efficiency in engines. The impact of the jet process within the engine, as well as its control parameters, on emission pollutants (particularly soot particles) remains unclear. This study focuses on examining the effects of various low-flow injection control strategies on engine combustion and emissions by using optical experiments and numerical simulations. It also explores the impact of different ignition advance angles (ignition timings) based on a short pre-chamber mixing interval to observe ignition combustion, flame propagation, and emission characteristics under ultra-lean conditions (λ = 2.0). The main conclusions are as follows. Appropriately increasing the injection mass can enhance engine load. However, further increases in injection mass significantly raise particulate emissions, resulting in an increase in particle number by up to more than 37-fold, especially for small particles in the 5–––10 nm size range. The chemical reaction between the luminous jet flame and the bright incandescent wake jet flame, as captured by high-speed photography, effectively characterizes the various stages of jet ignition. To reduce particulate matter emissions, it is crucial to avoid the foreseeable wake jet flame caused by the enrichment of the jet mixture in the pre-chamber. The low-flow injection timing should neither be too early nor close to the ignition spark timing. The early injection causes fuel to accumulate at the top of the pre-chamber, hindering the jet flame’s propagation into the main combustion chamber. Late low-flow injection leads to fuel enrichment, resulting in uneven mixing and poor atomization and diffusion due to short mixing times. Ignition after a short mixing time interval tends to increase knocking, resulting in intense combustion and an advanced phase, which slightly reduces load and combustion stability. Regarding the heat release ratio, the total heat release from the two combustion stages in the pre-chamber should ideally account for about 5–6 % of the heat release in the main chamber.

Reviews on Laser-Driven Ignition System for Guidance Missiles and Space Vehicles

Reviews on Laser-Driven Ignition System for Guidance Missiles and Space Vehicles

An experimental study on the influence of nozzle hole numbers and patterns of a passive pre-chamber spark ignition system

Pre-chamber spark ignition system enhances the combustion stability and efficiency of lean burn engines. Pre-chamber spark ignition system performance directly relies on the characteristics of the turbulent flame jet, which are governed by the pre-chamber geometrical parameters and nozzle hole configurations. Based on the existing literatures, limited research on nozzle hole numbers and patterns is noted with passive pre-chamber, and thus, the impact of these nozzle hole configurations on the combustion and flame development characteristics for hydrogen-methane-air mixtures is investigated in a constant volume combustion chamber. In the current study, single-layer nozzle hole configurations with three, four, six, and eight nozzle holes and double-layer nozzle hole configurations with six and eight nozzle holes are designed and tested in an optically accessible combustion chamber under various equivalence ratio conditions. The results indicated that the combustion characteristics deteriorated with an increase in nozzle holes, except with the single-layer four nozzle hole configuration. Compared to the single-layer eight nozzle hole configuration, the ignition delay and combustion duration for hydrogen-methane-air mixtures with single-layer four nozzle hole configuration was reduced by 31.9% and 30.7% under lean conditions. A reduction in flame jet penetration length, area and velocity and increased adjacent flame jet interaction was noticed for the single-layer configuration with more nozzle holes, and thus, a different nozzle hole pattern was studied in the current study. The double-layer configurations with more nozzle holes showed better combustion and flame development characteristics than single-layer configurations due to their unique flame structure, uniform and faster flame jet distribution, and reduced adjacent flame jet interaction. The ignition delay and combustion duration for hydrogen-methane-air mixtures with the double layer eight nozzle hole configuration were reduced by 30.5% and 40.7% compared to the single-layer eight nozzle hole configuration.

Analysis of Energy Transfer in the Ignition System for High-Speed Combustion Engines

In order to produce reliable and reproducible ignition of lean fuel–air mixtures and highly stratified mixtures, it is necessary to ensure a high concentration of spark discharge energy and to provide a strong energy impulse for the triggering of chain processes of chemical decomposition of fuel molecules. For this reason, studies have been undertaken on the flow of electrical energy from the ignition system to the spark plug and on the formation of an electric discharge arc with a high concentration of thermal energy. The experimental results were obtained using an ignition coil energy test stand and a constant volume chamber with high-speed spark discharge recording capability. It was confirmed that increasing the charging time of the ignition coil from 0.5 ms to 5.0 ms increases the energy delivered to the coil from 9.5 mJ to 330 mJ. In the same range, the energy generated by the coil was recorded to range from 4.2 mJ to 70 mJ. The coil’s efficiency was found to decrease with increasing charging time from 45% up to 20.5%. Further energy losses were presented when the spark discharge energy was analyzed. In the paper, the results of investigations concerning electric discharge arc development have been presented, illustrated by a few exemplary photos, and discussed. The mathematical interpretation of the electrical energy flux in the ignition system resulting from the energy of the discharge arc has been conducted and illustrated by some functional independences and relationships.

Combustion and emissions of an ammonia heavy-duty engine with a hydrogen-fueled active pre-chamber ignition system

Combustion and emission characteristics of a heavy-duty single-cylinder ammonia engine with a hydrogen-fueled active pre-chamber ignition system are investigated experimentally at the condition of IMEP 10 bar, 1000 rpm, where effects of spark timing, excess air ratio (λ), and hydrogen energy ratio are tested. Three distinguishable combustion phases are observed, including pre-chamber combustion, turbulent-jet-controlled combustion, and ammonia-chemical-kinetics-controlled combustion. Advancing spark timing makes combustion phases earlier, increasing pressure rise rate, combustion pressure, and NOx emissions. The optimal spark timing for the highest indicated thermal efficiency (ITE) is −12°CA ATDC in the experiment. λ range for stable combustion is 1.1–1.5 and ITE peaks at λ = 1.3. The hydrogen energy ratio, 7.9%∼10.5%, has little influence on the engine performance. However, a low hydrogen energy ratio could increase the risk of misfire. The optimal hydrogen energy ratio is about 9∼10%.

Experimental investigation of the ignition dynamics in a premixed annular combustor using a pre-chamber ignition system

In this paper, the ignition characteristics in a MICCA-type annular combustor are studied for the first time using a pre-chamber combustion (PCC) system. The PCC is proposed to replace the traditional spark electrode ignitor in the annular combustor, aiming to shorten ignition time and prevent misfiring. The PCC system is commonly utilized to initiate the ignition process in internal combustion (IC) engines by generating high-temperature turbulent jets that ignite the fuel/air mixture in the main combustion chamber (MCC). The PCC is integrated into a premixed annular combustor consists of sixteen swirling burners. The ignition characteristics and flame propagation patterns are investigated using a high-speed camera under varying conditions of equivalence ratios, bulk velocities, and thermal power levels. Experimental results demonstrate that the PCC exhibits a high ignition response without misfire. The induced turbulent jet from the PCC is observed to propagate into both sides of the annular combustor with high energy, creating a significant initial flame area along the jet trajectory. This enhances the ignition probability compared to traditional spark electrode ignition systems. Due to the higher burning rate resulting from the jet ignition, the light-round time is reduced by 41 % compared to traditional spark electrode ignition systems operating at the same equivalence ratio of 0.81 and the same bulk velocity of 3.22 m/s. This improvement is particularly advantageous for high-altitude re-ignition scenarios.

A review of the application development and key technologies of rotary engines under the background of carbon neutrality

Rotary engines possess advantages such as light weight, high power density, and strong fuel adaptability, which are essential for powertrain systems. They hold great potential in the field of power machinery. However, the development of rotary engines has been constrained by increasingly stringent emission regulations. Despite this, numerous scholars and institutions continue to optimize rotary engines, leading to a proliferation of related research. It is necessary to synthesize these findings to guide future promotion and application efforts. This review examines the current applications and development status of rotary engines globally. It summarizes the development of key technologies such as sealing techniques, rotor configurations, and ignition devices, which have achieved lower energy consumption and emissions. The suitability of rotary engines for automotive and unmanned aerial vehicle applications has also been reported. To further reduce carbon emissions, researchers have explored zero-carbon fuel rotary engines. Hydrogen-fueled rotary engines have demonstrated higher combustion efficiency. By integrating EGR, load control strategies, and ignition system layouts, they have addressed issues such as NOx emissions, knock, and leakage. The development of ammonia-hydrogen hybrid fuels is also a potential effective solution. Continuous innovative research indicates that, with their inherent advantages and the integration of alternative fuels and advanced ignition technologies, rotary engines have the potential to meet future energy and environmental requirements. This positions them as strong contenders in future diversified power systems.

Enhancing ignition stability in an annular combustor using a pre-chamber ignition system

The traditional method using spark electrode ignition in annular combustors lacks safety due to its long ignition delay and deficiencies in reliability and repeatability. The present work investigates the ignition characteristics of a premixed annular combustor using pre-chamber combustion (PCC) as an ignition source. The ignition process of the annular combustor is studied experimentally with PCC and is compared to the one with the traditional spark electrode ignition under the same equivalence ratio and bulk velocities. The ignition process is recorded using a high-speed camera. The two-dimensional time-resolved Mie scattering technique is employed to determine the flame front position in the annular combustor. It was found that the jet issued from PCC generates hot radicals associated with strong turbulence, exhibiting distributed ignition sites along the jet trajectory inside the annular combustor. Introducing PCC to the annular combustor increases the ignition probability and burning rate, as well as reduces the light-round time by about 24 % compared to the spark electrode at a thermal power of 18.6 kW. Moreover, the experimental results indicate that flame propagation in the annular combustor is significantly influenced by the PCC operating parameters. In contrast, combustion within the PCC is less affected by the local flow structure in the annular combustor, making the PCC a favourable solution for various operating conditions. Additionally, a slightly rich mixture in the PCC increases the burning rate, whereas a very rich mixture decreases the burning rate.

CFD Simulation of Pre-Chamber Spark-Ignition Engines—A Perspective Review

The growing demand to reduce emissions of pollutants and CO2 from internal combustion engines has led to a critical need for the development of ultra-lean burn engines that can maintain combustion stability while mitigating the risk of knock. One of the most effective techniques is the pre-chamber spark-ignition (PCSI) system, where the primary combustion within the cylinder is initiated by high-energy reactive gas jets generated by pilot combustion in the pre-chamber. Due to the complex physical and chemical processes involved in PCSI systems, performing 3D CFD simulations is crucial for in-depth analysis and achieving optimal design parameters. Moreover, combining a detailed CFDs model with a calibrated 0D/1D model is expected to provide a wealth of new insights that are difficult to gather through experimental methods alone, making it an indispensable tool for improving the understanding and optimization of these advanced engine systems. In this context, numerous previous studies have utilized CFD models to optimize key design parameters, including the geometric configuration of the pre-chamber, and to study combustion characteristics under various operating conditions in PCSI engines. Recent studies indicate that several advanced models designed for conventional spark-ignition (SI) engines may not accurately predict performance under the demanding conditions of Turbulent Jet Ignition (TJI) systems, particularly when operating in lean mixtures and environments with strong turbulence–chemistry interactions. This review highlights the pivotal role of Computational Fluid Dynamics (CFDs) in optimizing the design of pre-chamber spark-ignition (PCSI) engines. It explores key case studies and examines both the advantages and challenges of utilizing CFDs, not only as a predictive tool but also as a critical component in the design process for improving PCSI engine performance.

Effects of dual-spark ignition system with two different piston bowl shapes on combustion and efficiency in a single-cylinder engine

In this study, a dual-spark ignition system was systemically evaluated in a single-cylinder engine. Since the test engine was originally based on the diesel engine, two sparks were located symmetrically on the left and right, with the diesel injector in the middle of the engine head. At first, the effect of dual-spark ignition on the combustion process was compared with the single-spark (only right used) condition under 1600 rpm/gIMEP 0.7 MPa. Also, varying excessive air ratios were evaluated for the two conditions. The second experiment changed the piston bowl shape from (a Mexican) hat to a flat (bathtub-shaped) for the dual-spark ignition system under five representative operating conditions. Also, the maximum load was verified under a knocking frequency of 30%. The results emphasized that dual-spark ignition showed superb CoV of net indicated mean effective pressure (nIMEP) as 2.71% under excessive air ratio 1.55 condition, while it was higher than 5% with single-spark ignition. In addition, the net indicated thermal efficiency was 37.33%. Also, when flat bowl-shaped piston was used with dual-spark ignition system, the maximum load with avoidance of severe knocking could be increased from nIMEP 1.07 to 1.44 MPa due to enhancing flame propagation speed.

Optical Investigation of Sparks to Improve Ignition Simulation Models in Spark-Ignition Engines

The use of renewable fuels in place of fossil fuels in internal combustion engines is regarded as a viable method for achieving zero-impact-emission powertrains. However, to achieve the best performance with these fuels, these engines require further optimization, which is achieved through new combustion strategies and the use of advanced ignition systems such as prechambers. Since simulations greatly accelerate this development, accurate simulation models are needed to accurately predict the combustion phenomenon, which requires a deep understanding of the ignition phenomenon as it significantly affects combustion. This work presents a comprehensive experimental methodology to study sparks under engine conditions, providing quantitative data to improve and validate ignition simulation models. The goal was to determine the volume generated by sparks under engine conditions that can initiate combustion and use this information to improve simulation results to match the experimental results. The visible sparks were observed with high-speed cameras to understand their time-resolved evolution and interaction with the flow. The heat transfer from the plasma was also visualized using a modified Background-Oriented Schlieren technique. The information gained from the experimental observations was used to improve an ignition simulation model. Since the velocity of the plasma was found to be slower than the surrounding flow, a user-defined parameter was included to calibrate the velocity of the simulated plasma particles. This parameter was calibrated to match the simulated spark length to the experimental spark length. In addition, since the previous simulation model did not take the heat transfer from the plasma into account, the simulated plasma particles were coupled to have heat transfer to the surroundings. Based on a comparison of the simulation results with the experimental results, the improved approach was found to provide a better physical representation of the spark ignition phenomenon.

Laboratory systems for detonation research

Decarbonizing global energy systems is among the most pertinent challenges in the climate crisis. Tightly tied to the economic prosperity of a nation and responsible for more than 75% of global emissions, decarbonization of the energy sector will require well-developed solutions. The emergence of detonation engines can reduce emissions in aviation and gas-fired power generation, with theoretical efficiencies 40% lower than conventional engines. These efficiencies have yet to be realized in practice, due to our lack of understanding of detonation propagation and its instabilities. This project aimed to develop the laboratory systems required to study detonations. To this end, a long rectangular channel was manufactured and outfitted with a gas handling system to inject a mixture, an ignition system, pressure transducers to capture the propagation characteristics, and an optical system enabling Schlieren photography. The gas handling system uses sonic nozzles, thus flow rate is a linear function of upstream line pressure. Each line contains a pressure transducer, microcontroller to process signals, LCD for pressure readout, and a regulator for adjustment of the line pressure. The ignition system uses an ignition box that steps up a 12 V supply to 400 V, an ignition coil raising the voltage to 15-40 kV, and a spark plug to ignite the mixture. Ignition, pressure transducer signal acquisition, and Schlieren photography are all synchronized using a NI-6356 DAQ with LabVIEW. The DAQs analog input ports receive readings from the pressure transducers along the channel, the timing of which and known distance between transducers allows for velocity calculations. The schlieren system utilizes the digital output channels to synchronize camera shutter with an LED driver, and parabolic mirrors, positioned to optimize schlieren imaging. The LED driver requires greater current than produced by the DAQ thus a current amplifier circuit is used to bridge the DAQ and driver.

A repetitive pulsed electrothermal plasma jet ignition system based on capillary discharge.

Plasma ignition and combustion enhancement is a promising technology in applications of engines, industrial burners, pollutant emissions controls, etc. A new repetitive electrothermal plasma jet ignition system based on ablated capillary discharge under atmospheric pressure is presented in this paper. It consists of a capillary discharge module, a pulse current circuit, a pulse voltage circuit, a current release unit, an LC series resonant circuit, and a control system. The effects of the energy storage capacitor's voltage and resistance in the current release unit on the electrical parameters are investigated. Increasing the capacitor voltage helps to shorten the discharge delay and increase the energy deposition efficiency in the main discharge process. The increase of the resistance in the current release unit leads to a longer discharge delay and higher energy deposition efficiency in the main discharge process. Balanced parameters between the delay of discharge in 66 µs and the energy deposition efficiency in 84% are achieved through optimization, with a peak radiative heat flux of 23MWm-2 and a maximum jet length of 17cm. Repetitive capillary discharge at 20Hz under atmospheric pressure is achieved with the dispersion of energy storage capacitor charging voltage and energy deposition efficiency of 0.3% and 9.6%, respectively. Simplified circuit topology and control logic contribute to the miniaturization of the ignition system.

Experimental study on multi-point ignition of NH3/air by high-frequency nanosecond dielectric barrier discharge

Non-equilibrium plasma ignition technology, with its ability to expand ignition limits and increase ignition volume, is considered an important development direction of advanced ignition systems, and has significant advantages in improving ignition stability and combustion rate. This study investigates the ignition and combustion assistance effect of high-frequency nanosecond surface dielectric barrier discharge (nSDBD) on NH3/air mixture in a constant volume combustion chamber (CVCC). The study reveals the influence of high-frequency nSDBD on the growth process of the flame kernel in NH3/air mixture. As the discharge pulse number (PN) increases, the flame kernel develops from the middle position of the discharge filament to the head of the discharge filament, while there is no obvious flame at the root and middle of the discharge filament. Continuous discharge causes the flame kernel to appear concave and the center of the flame kernel to shift towards the wall of the CVCC. In the NH3/air mixture, the initial flame kernels exhibit dissipation phenomenon, resulting in a discrepancy between the number of initial flame kernels and the number of stable combustion flame kernels. As the discharge frequency or pulse number increases, and the number of stable combustion flame kernel increases. The adjustment of discharge frequency and pulse number can effectively control the flame development time (FDT) and flame rise time (FRT) of NH3/air mixture. As PN increases, both FDT and FRT are shortened. When discharge frequency is 20 kHz, the maximum shortening of FDT and FRT are 30 ms and 14 ms, respectively, about 55 % and 30 %. The effects of discharge frequency on FDT and FRT exhibit a non-monotonic variation pattern, and it is necessary to comprehensively consider various discharge parameters to achieve the best ignition effect. The ignition success rate curve of high-frequency nSDBD in NH3/air mixture is steep. The study results of this paper provide new discoveries and experimental data for advanced ignition systems.

Passive turbulent jet ignition of jet fuel in a rapid compression machine

Turbulent jet ignition is a promising alternative to conventional spark ignition systems to achieve rapid combustion of difficult-to-ignite mixtures. Jet ignition can facilitate combustion of lean mixtures at low pressure and temperature by ejecting hot reacting jets of unburned gases, intermediate species, and combustion products into the main chamber to accelerate overall ignition. These jets ignite the main chamber at multiple locations, reducing the time required for the main chamber charge to be consumed. The focus of this research is to gain an improved fundamental understanding of the turbulent jet ignition process of F-24 and air at low pressure and temperature conditions with lean (φ = 0.5) and stoichiometric (φ = 1.0) mixtures using 3D RANS simulations. A Rapid Compression Machine with pressure transducers in the pre-chamber and main chamber was modeled, and distinct events during the jet ignition process were determined from pressure measurements and their time derivatives of a single compression stroke. By understanding events during the jet ignition process with jet fuel, these results give insight into achieving stable combustion of heavy fuels at low pressure and temperature conditions with high levels of dilution.

IoT Based Smart Car Monitoring System

Due to the rapid increase in vehicles on the road, the probability of road accidents is rising steeply. Drunk driving is considered a major cause of road accidents worldwide. The main aim of this project is to develop a system that detects the amount of alcohol consumed by the driver. The proposed system aims to prevent the driver from operating the vehicle while intoxicated, thereby reducing the number of accidents caused by drunk driving. Additionally, it ensures that the driver wears a seatbelt. The system also includes an automatic headlight dim-dip control, which prevents the bright beam of light from disturbing oncoming vehicles. It features brake failure detection, which will identify brake failure and automatically slow down and stop the vehicle. The proposed model is developed using an Arduino Uno, with an alcohol detection sensor, brake failure sensor, and seatbelt sensor as its major components. As a safety measure, when the alcohol level exceeds a permissible limit, the vehicle's ignition system will be turned off, and the concerned authorities will be alerted via an IoT module

Combustion Test for the Smallest Reciprocating Piston Internal Combustion Engine with HCCI on the Millimeter Scale

Micro reciprocating piston internal combustion engines are potentially desirable for high-energy density micro power sources. However, complex subsystem functions hinder the downsizing of reciprocating piston internal combustion engines. The homogeneous charge compression-ignition (HCCI) combustion mode requires no external ignition system; it contributes to structural simplification of the reciprocating piston internal combustion engines under a micro space constraint but has not been adequately verified at the millimeter scale. The study used a millimeter-scale HCCI reciprocating piston internal combustion engine fueled by a mixture of kerosene, ether, castor oil, and isopropyl nitrate for combustion investigation. The test engine with a displacement of 0.547 cc is the smallest reciprocating piston internal combustion engine known to have undergone in-cylinder combustion diagnosis. It is observed that the HCCI combustion mode at the millimeter scale can realize stable combustion with excellent cooperation for the thermodynamic cycle under appropriate structural and operating conditions, which is essentially not inferior to those in conventional-sized reciprocating piston internal combustion engines. This finding helps the next step of scaling down reciprocating piston internal combustion engines.

Laser ignition on single droplet characteristics of aviation kerosene at different pressures and initial diameters: ignition, combustion and micro-explosion

In this study, an experimental system for single-droplet ignition by laser under different pressures is established, and the laser ignition is used to examine how pressure and initial diameter influence ignition properties of RP-3 aviation kerosene single-droplet. The findings reveal that depending on the extent of the impact of bubble rupture on the droplet's shape, The droplet's morphological alterations can be classified into three types: micro-expansion, puffing, and micro-explosion. The ignition and combustion of droplets is segmented into four distinct phases: heating, ignition, intense combustion, boiling combustion. The flame width diminishes with rising pressure. Single droplet ignition delay time is strongly influenced by the pressure, which is reduced by 92.7 %, 94.1 % and 94.3 % for the three droplets from small to large diameters with the pressure increases from 1 bar to 4 bar. The change trends of droplet diameters are first increasing and then decreasing. The whole burning rate of RP-3 droplets goes up with the rise of pressure. A droplet laser ignition model is proposed, the minimum ignition energy of RP-3 droplets with an initial diameter of 1.42 mm at pressures of 1–4 bar are obtained to be 0.88 J, 0.80 J, 0.68 J, and 0.59 J, respectively.

Ignition and flow combustion characteristics of hydroxylammonium nitrate - based liquid propellant based on electric method

Hydroxylamine nitrate (HAN)-based liquid propellants are characterized by high energy content and low toxicity ionic monopropellants, offering great potential application prospects in the space engine. This paper proposes an experimental system for electric ignition and combustion of HAN-based liquid propellant. The energy for decomposition, current, and combustion image of HAN-based liquid propellant are measured under different initial voltage, propellant volume, and the initial pressures in Ar and air atmospheres. The results show that the energy for decomposition decreased with an increase in initial voltage, propellant volume, and initial pressure. An increase in the initial voltage accelerates the reaction speed of HAN-based liquid propellant, and the energy for decomposition is approximately 3 J. An increase in the propellant volume decreases the equivalent resistance in the circuit, increasing the current and enhancing the thermal effect of the propellant. The accumulation of decomposition products and heat under high pressure reduced the energy for decomposition; the energy for decomposition is less than 1.5 J for the pressurization condition. Compared with the Ar atmosphere, the energy for decomposition of HAN-based liquid propellant shows better stability in the air atmosphere. The flow combustion device of HAN-based liquid propellant for the flow state is designed. The HAN-based liquid propellant is successfully ignited for different initial voltages and flow rates. The research results provide a reference for the design of space engine for HAN-based liquid propellant based on the electric ignition method.