Conventional Ignition Research Articles

Investigation on ignition enhancement characteristics by high-energy spark in a scramjet combustor under low flight Mach conditions

Ignition characteristics of the long electrode distance high-energy spark igniter (LHSI) in a cavity-stabilized scramjet combustor at low flight Mach has been numerically and experimentally investigated and compared with those of conventional lower energy spark igniter (SI). The effects of ignition and injection schemes on ignition performance were analyzed and the enhancement of greater spark energy were verified. The results show that the widest ignition boundary of SI is observed when the kerosene is injected in far field due to the sufficient evaporation of kerosene droplets and the disturbance caused by upstream cavity. Due to the greater energy deposition by LHSI, the ignition performance is markedly improved and the ignition boundary of combustor is extended from 0.131–0.148 to 0.091–0.224 under the scheme of I1+L2. The increased energy deposition of spark plasma ignites more combustible mixture and enhances the initial combustion, leading to a larger high-temperature zone. This is crucial for ensuring the survival of the flame kernel against dissipation of airflow in the scramjet combustor operating at low fight Mach numbers due to the short duration of spark discharge.

Graphene-enhanced sustainable fuel from Calophyllum inophyllum for premixed charge compression ignition engines: Advancing circular economy and emission reduction

This study investigates the impact of modifying a conventional compression ignition (CI) engine by inducting pentanol in inlet manifold and injecting graphene-blended tamanu biodiesel into the cylinder. These modifications significantly enhance ignition quality and expand operational capabilities within the premixed charge compression ignition (PCCI) engine. The use of graphene-enhanced biodiesel in PCCI mode demonstrates potential for improved combustion efficiency and emission reduction. Dispersed graphene nanoparticles in tamanu biodiesel notably improve brake thermal efficiency due to their increased surface area, which enhances fuel-air mixing. Graphene-suspended biodiesel at a concentration of 100 ppm in PCCI mode results in an 11.5 % peak pressure rise and an 8.4 % rise in heat release rate with respect to pure biodiesel in CI mode. This nano-suspension biodiesel also shows significant thermal efficiency improvements, with an 8.20 % increase and a 22.08 % reduction in fuel consumption with respect to neat biodiesel in CI mode. The combination of pentanol and graphene-blended tamanu biodiesel improves combustion quality, yielding a 13 % reduction in carbon monoxide emissions, a 34.67 % reduction in hydrocarbon emissions, a notable 65.84 % lower in nitrogen oxide, and a 33.91 % reduction in smoke with respect to neat tamanu biodiesel in CI mode of operation.

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.

Enhancing reactivity-controlled compression ignition engine performance: A response surface methodology approach with ammonium hydroxide-waste cooking oil biodiesel optimization

The focus on ammonium hydroxide, biodiesels and their combustion technology has garnered significant attention in pursuing carbon-neutral and carbon-free fuels to address greenhouse gas emissions (GHG) and mitigate global warming. Low-temperature combustion (LTC) has been introduced as an alternative method to conventional compression ignition (CI) combustion. Reactivity controlled compression ignition (RCCI) can be achieved by introducing highly reactive waste cooking oil methyl ester (WCOME) oil directly into the manifold in intervals of 10% energy and injecting low-reactive ammonium hydroxide at 20%–50%. Utilizing the response surface methodology (RSM) approach, it was determined that for optimal operation in RCCI mode, an ideal ammonium hydroxide energy sharing (AHES) of 43% would account for the varying parameters and their effects on emissions and performance. The results of the experiments predicted a brake thermal efficiency (BTHE) of 34.85% and a brake specific energy consumption (BSEC) of 10.69 MJ/kWh. Meanwhile, a notable decrease in exhaust emissions was observed for HC, CO, CO2, NO x and smoke by 41.54%, 38.89%, 48.89%, 51.27% and 65.80% respectively when compared to conventional biodiesel combustion (CBC). The experimental result at maximum load operation with an AHES of 50% indicates that RCCI combustion led to an increase in thermal efficiency from 30.36% to 35.42%, and the in-cylinder pressure and heat release rate dropped from 83.42 bar to 59.64 bar and 78.68 kJ to 60.92 kJ, respectively. There was a significant reduction in HC, CO, CO2, NO x and smoke emissions recorded as 58.76 ppm, 0.11%v, 1.61%v, 442 ppm and 6.64 N, respectively, compared to CBC.

Laser ignition versus conventional spark ignition system performance for hydrogen-enriched natural gas-air mixtures in a constant volume combustion chamber

This study compares the performance of a laser ignition system vis-à-vis a conventional electrical spark ignition system in a constant volume combustion chamber. A custom-built constant-volume combustion chamber was used to compare the performance of the laser and spark ignition systems. A combination of three lenses in the optical path was used to create laser plasma in the constant volume combustion chamber. Initial chamber pressure and temperature were maintained constant at 4 bar and 150 °C during the experiments. The effect of hydrogen enrichment of compressed natural gas on combustion was assessed for three relative air–fuel mixture strengths (λ: 1.0, 1.2 and 1.4) to compare the performance of both ignition systems. The laser ignition system exhibited superior combustion characteristics to the spark ignition system. The combustion duration of laser ignition was considerably lower than spark ignition. Three hydrogen-enriched natural gas blends (10HCNG, 20HCNG and 40HCNG) were assessed and compared with baseline compressed natural gas. Hydrogen enrichment improved the combustion characteristics, increasing the excess chamber pressure and reducing the combustion duration. Two locations were taken for assessing the performance of the laser ignition system in this study. The first location was the same as the spark from a conventional electrical spark ignition system, and the second was at the centre of the constant volume combustion chamber. The central location of laser ignition showed a higher reduction in the combustion duration than baseline spark ignition and its corresponding laser ignition, indicating its superiority. The ability to choose an ignition location centrally in the engine combustion chamber emerged to be a main advantage of laser ignition systems.

Motorcycle Engine Performance Comparison Between Laser Ignition System and Conventional Ignition System Through Simulation

Motorcycle Engine Performance Comparison Between Laser Ignition System and Conventional Ignition System Through Simulation

Computational Fluid Dynamics (CFD) Validation and Investigation the Effect of Piston Bowl Geometries Performance on Port Fuel Injection-Homogeneous Charge Compression Ignition (PFI-HCCI) Engines

Computational Fluid Dynamics (CFD) Validation and Investigation the Effect of Piston Bowl Geometries Performance on Port Fuel Injection-Homogeneous Charge Compression Ignition (PFI-HCCI) Engines

Experimental and numerical approach to assess the dynamic performance of an inductive ignition system

This paper envisages studying the features of a conventional inductive ignition system along with its MOSFET and IGBT-based transistorized modifications. The influence of mechanical contact breaker dynamics and ignition coil characteristics on the current and voltage waveforms of the primary and secondary circuits of these studied ignition systems are mathematically and experimentally exposed. The investigation is considered necessary prior to attempting subsequent modeling and diagnostics procedures on the current-voltage performance characteristics of conventional and transistorized ignition systems. The work has demanded the development of an experimental setup based on a basic modifiable ignition system mockup and an instrumentation system to measure and analyze the voltage-current parameters of inductive ignition systems. The paper describes the design details of such instrumentation system, presents mechanical and electrical models for contact breaker and ignition circuits, then simulated to obtain base free-run response waveforms and electrical continuity behavior of the contact. A test of frequency response of the ignition coil provided additional input to the model. An experimental test of continuity of the contact, in agreement with its model, shed light on the actual excitation of the primary coil. The work comments on a sample of the registered current and voltage waveforms in primary and secondary coil windings of the ignition system at atmospheric conditions. Comparisons of waveforms and energy for mechanical contact, MOSFET and IGBT switches are made to establish them as a reference for future tests.

Numerical model for linear stimulated Raman scattering in inhomogeneous plasmas

Numerical model for calculating convective gains and absolute thresholds of stimulated Raman scattering (SRS) in inhomogeneous plasmas is constructed based on the Fourier-space method. The model is valid for arbitrary density profiles and scattering geometries, including both backscattering and side scattering. It is shown that 90 deg side scatter has a lower absolute threshold than other scattering geometries. Backscatter, on the other hand, has a relatively large absolute threshold under conventional direct-drive ignition conditions. For a parabolic density profile, the absolute threshold of backscatter decreases dramatically at the peak of parabola, but is still much larger than that of side scatter. We also discuss the absolute thresholds of side scatter under different density profiles, showing not big differences with the linear density profile as well as the analytic formulas. Convective gains, however, are sensitive to the density profiles and collisional damping. The k-space numerical model is verified via analytic formulas and real-space envelope model, and it offers us new perspective on the scattering angles compared with previous models for SRS.

Numerical study of piston bowl geometries on PFI-HCCI engine performance

Homogeneous charge compression ignition (HCCI) is an advanced combustion strategy proposed to provide higher efficiency and lower emissions than conventional compression ignition. However, there are still tough challenges in the successful operation of HCCI engines. Among these challenges, homogeneous mixture preparation and combustion phase control plays a vital role in determining the efficiency and emissions. Piston bowl geometry significantly enhances the process by improving the flow, turbulence, and mixing for the combustion. The study utilised experimental and numerical simulation methods to analyse HCCI combustion in port fuel injection (PFI) mode and evaluate the effect of piston geometries on engine performance. For this purpose, the different pistons bowl geometries (Baseline model, SQC, and CCC) with the same volume, compression, and equivalence ratio were numerically tested in a four-stroke, single-cylinder, YANMAR diesel engine. The numerical simulation results provide adequate assurance to proceed with the study with different piston geometries design. Compared to SQC and CCC, the Baseline model produced significantly higher cylinder pressure, temperature, and heat release rate. Different piston shape designs influenced the formation of air-fuel mixing, thereby affecting the time and location of onset combustion. The present investigation offered the significant role of piston geometry for the control mechanism of PFI-HCCI combustion, that is a vital part in demonstrating HCCI combustion.

A co-kurtosis PCA based dimensionality reduction with nonlinear reconstruction using neural networks

For turbulent reacting flow systems, identification of low-dimensional representations of the thermo-chemical state space is vitally important, primarily to significantly reduce the computational cost of device-scale simulations. Principal component analysis (PCA), and its variants, are a widely employed class of methods. Recently, an alternative technique that focuses on higher-order statistical interactions, co-kurtosis PCA (CoK-PCA), has been shown to effectively provide a low-dimensional representation by capturing the stiff chemical dynamics associated with spatiotemporally localized reaction zones. While its effectiveness has only been demonstrated based on a priori analyses with linear reconstruction, in this work, we employ nonlinear techniques to reconstruct the full thermo-chemical state and evaluate the efficacy of CoK-PCA compared to PCA. Specifically, we combine a CoK-PCA-/PCA-based dimensionality reduction (encoding) with an artificial neural network (ANN) based reconstruction (decoding) and examine, a priori, the reconstruction errors of the thermo-chemical state. In addition, we evaluate the errors in species production rates and heat release rates, which are nonlinear functions of the reconstructed state, as a measure of the overall accuracy of the dimensionality reduction technique. We employ four datasets to assess CoK-PCA/PCA coupled with ANN-based reconstruction: zero-dimensional (homogeneous) reactor for autoignition of an ethylene/air mixture that has conventional single-stage ignition kinetics, a dimethyl ether (DME)/air mixture which has two-stage (low and high temperature) ignition kinetics, a one-dimensional freely propagating premixed ethylene/air laminar flame, and a two-dimensional dataset representing turbulent autoignition of ethanol in a homogeneous charge compression ignition (HCCI) engine. Results from the analyses demonstrate the robustness of the CoK-PCA based low-dimensional manifold with ANN reconstruction in accurately capturing the data, specifically from the reaction zones.

Influence of Hydrogen on the Performance and Emissions Characteristics of a Spark Ignition Ammonia Direct Injection Engine

Because ammonia is easier to store and transport over long distances than hydrogen, it is a promising research direction as a potential carrier for hydrogen. However, its low ignition and combustion rates pose challenges for running conventional ignition engines solely on ammonia fuel over the entire operational range. In this study, we attempted to identify a stable engine combustion zone using a high-pressure direct injection of ammonia fuel into a 2.5 L spark ignition engine and examined the potential for extending the operational range by adding hydrogen. As it is difficult to secure combustion stability in a low-temperature atmosphere, the experiment was conducted in a sufficiently-warmed atmosphere (90 ± 2.5 °C), and the combustion, emission, and efficiency results under each operating condition were experimentally compared. At 1500 rpm, the addition of 10% hydrogen resulted in a notable 20.26% surge in the maximum torque, reaching 263.5 Nm, in contrast with the case where only ammonia fuel was used. Furthermore, combustion stability was ensured at a torque of 140 Nm by reducing the fuel and air flow rates.

Gas-Dynamic Interactions between Pre-Chamber and Main Chamber in Passive Pre-Chamber Ignition Gasoline Engines

<div>Pre-chamber turbulent jet ignition (TJI) is a method of generating distributed ignition sites through multiple high-speed turbulent jets in order to achieve an enhanced burn rate in the engine cylinder when compared to conventional spark plug ignition. To study the gas-dynamic interactions between the two chambers in a gasoline engine, a three-dimensional numerical model was developed using the commercial CFD code CONVERGE. The geometry and parameters of the engine used were based on a modified turbocharged GM four-cylinder 2.0 L GDI gasoline engine. Pre-chambers with nozzle diameters of 0.75 mm and 1.5 mm were used to investigate the effect of pre-chamber geometry on pre-chamber charging, combustion, and jet formation. The local developments of gas temperature and velocity were captured by adaptive mesh refinement, while the turbulence was resolved with the k-epsilon model of the Reynolds averaged Navier–Stokes (RANS) equations. The combustion process was modeled with the extended coherent flamelet model (ECFM). Data from engine experiments were compared with the computed main chamber pressures and heat release rates, and the results show good consistency with the model calculations. The scavenging and air–fuel equivalence ratio (λ) distribution of the pre-chambers improved with the larger nozzle, while the smaller nozzle generated jets with higher velocity, greater turbulence kinetic energy, and longer penetration length. Moreover, after the primary jet formation, secondary pre-chamber charging, combustion, and secondary jet formation were observed.</div>

Experimental evaluation and neural network modelling of reactivity-controlled compression ignition engine using cashew nut shell oil biodiesel-alumina nanoparticle blend and gasoline injection

The current desire is for enhanced combustion techniques that improve engine efficiency while successfully reducing emissions. Reactivity controlled compression ignition (RCCI) combustion encompasses the ability to increase fuel efficiency and decrease oxides of nitrogen emissions compared to conventional compression ignition (CI) combustion. This study presents a novel investigation that focuses on the capabilities of the RCCI engine, utilizing a unique combination of gasoline and diesel blended with cashew nut shell oil biodiesel (CNSOB) and the addition of aluminum oxide (Al2O3) nanoparticles. CNSOB extracted from waste shell has an oil content of 30–35 wt% yield. The cost of the oil range between is ₹. 40–50 in India. The engine operates on a blend of gasoline, known for its low reactivity, and diesel blended with CNSOB, a renewable and environmentally friendly alternative to diesel. The effects of varying proportions of the blend (B0, B50, and B100) and the addition of Al2O3 nano additive (25 and 50 ppm) on the efficiency and emissions of RCCI combustion are comprehensively analyzed experimentally. The results reveal that RCCI combustion significantly improves engine performance compared to compression ignition engines. A 2% increase in maximum in-cylinder pressure indicates improved combustion efficiency. Furthermore, fuel economy is improved by up to 2% due to increased engine brake thermal efficiency (BTE). Further, nitrogen oxide (NOx) emissions are reduced by up to 54% during RCCI combustion, demonstrating its potential for reducing pollution. Utilizing CNSOB biodiesel results in a 50% reduction in hydrocarbon (HC) emissions as well as a 17% reduction in carbon monoxide (CO) emissions. This indicates improved air quality and reduces environmental pollution. The incorporation of Al2O3 nano additives into the RCCI engine results in a 5% reduction in brake specific energy consumption (BSEC), showing better engine energy efficiency. Based on the results of the investigation, a neural network framework was developed. The neural network framework was developed to replicate both the efficiency and pollution parameters of the RCCI engine using the experimentally determined relationship between input factors and output parameters. The neural network model was trained using 70% of the available data, and its performance was evaluated by comparison of predictions with the corresponding observations from experiments. The forecast outcomes matched those of the trial, demonstrating the artificial neural network (ANN) models effectiveness and precision in predicting the engine performance and emissions.

Exploration of cross-beam energy transfer mitigation constraints for designing an ignition-scale direct-drive inertial confinement fusion driver

The compression of direct-drive inertial confinement fusion (ICF) targets is strongly impacted by cross-beam energy transfer (CBET), a laser-plasma instability that limits ablation pressure by redirecting laser energy outward and that is projected to be mitigated by laser bandwidth. Here, we explore various CBET mitigation constraints to guide the design of future ICF facilities. First, we find that the flat, Gaussian, and Lorentzian spectral shapes have similar CBET mitigation properties, and a flat shape with nine spectral lines is a good surrogate for what can be obtained with other spectral shapes. Then, we conduct a comprehensive study across energy scales and ignition designs. 3D hydrodynamic simulations are used to derive an analytical model for the expected CBET mitigation as a function of laser and plasma parameters. From this model, we study the bandwidth requirements of conventional and shock ignition designs across four different energy scales and find that they require between 0.5 and 3±0.2% relative bandwidth. Best mitigation is achieved when the beam radius over critical radius Rb/Rc is kept low during the drive while the plasma temperature is kept high. In a steady state, we find that the bandwidth required to mitigate 85% of CBET scales as (Rb/Rc)2.15Ln−0.58I0.7, where Ln is the density scale length, and I the laser intensity. Finally, we find that the chamber beam port layout does not influence CBET mitigation. In the case of a driver using many monochromatic beamlets, we find that ∼10 beamlets per port is required, with diminishing returns above ∼20.

Substitution of diesel fuel in conventional compression ignition engine with waste biomass-based fuel and its validation using artificial neural networks

This study aims to derive bioenergy from waste lather fat and citronella grass. Lather fat oil (LFO), citronella grass oil (CGO), a mixture of leather fat oil and citronella grass oil (LFCGO), and a nano-additive-incorporated mixture of lather fat oil and citronella grass oil (NFCO) were synthesized and used in diesel engines as the novelty of this study. ASTM standards were used to investigate and guarantee the fuel's properties. According to the experimental report, the nanoadditive's brake thermal efficiency and brake-specific fuel consumption were more comparable to diesel fuel. Compared to diesel, the NFCO blend reduced hydrocarbon, carbon monoxide, and particulate emissions by 6.48%, 12.33%, and 16.66%, respectively, while carbon dioxide and oxides of nitrogen emissions increased. The experiment's outcomes were verified using an artificial neural network (ANN). The trained model exhibits a remarkable coefficient of determination of 98%, with high R values varying from 0.9075 to 0.9998 and low mean absolute percentage error values ranging from 0.97% to 4.24%. Based on the experimental findings and validation report, it can be concluded that NFCO is an efficient diesel fuel substitute.

Novel approach for efficient operation and reduced harmful emissions on a dual-fuel research engine propelled with hydrogen-enriched natural gas and diesel

ABSTRACT The stricter emission norms have created a need to study recent combustion technology in internal combustion engines. Dual-fuel (DF) combustion technology is one of the key techniques to achieve future emission goals. Natural gas is one of the easily available low-reactive fuels worldwide that can be used in the DF combustion strategy. The main problem with using NG in the DF strategy is its lean-burning ability to produce emissions like HC and CO. The combustion losses associated due to crevice losses in the piston geometry are also the reasons for getting degraded engine performance. In the present study, the lean flammability of NG was improved by enriching it with hydrogen. The combustion losses were reduced using modified disc piston geometry with lower crevice volume. The results showed that the thermal efficiency obtained using HENG/diesel DF strategy with disc piston (DF disc) was only less than 0.3%, 0.4%, and 1% for low, mid, and high load conditions compared to conventional compression ignition mode using bowl piston (CI bowl). The change in piston geometry from bowl to disc type using the DF strategy improved the thermal efficiency by about 3.8%, 3.3%, and 2.7% for three load conditions. The NOx and smoke opacity reduction by about 6% to 19% and 40% to 60% in DF disc mode was achieved compared to CI bowl mode.

A Study on Coldflame Propagation Characteristics Applying Amplified Ignition Source to Overcome Landfill gas’s Flame Retardant Limit

In this study combustion characteristics were analyzed with LFG, one of the alternative energy sources of SI engines. To overcome the flame retardant limit, which is the shortcoming of LFG, the combustion characteristics were analyzed using the AIS device that was created for this study’s purpose. A static combustion chamber to which AIS can be applied was designed for the experiment that was conducted on the coldflame propagation and combustion characteristics of each LFG fuel using C-type (conventional ignition type) and AIS devices. From the basic LFG experiment, it was identified that as the proportion of carbon dioxide in the fuel increased, the combustibility decreased, and the combustion pressure decreased. When using the AIS device to overcome the flame retardancy of LFG, the combustion pressure was increased by 2 bar even in LFG70 and LFG60, where combustion was actively occurring with the C-type and the combustibility was improved in LFG50 as well. In overall respects, it was judged that the use of AIS could overcome the flame retardancy of LFG and could incorporate LFG into SI engines.

Ignition enhancement of liquid kerosene by a novel high-energy spark igniter in scramjet combustor at Mach 4 flight condition

Spark ignition system is the most widely used method in the combustor. However, it is generally considered unsuitable for scramjet engines due to the shortage of ignition energy. This study firstly presents a novel long electrode distance high-energy spark igniter (LHSI), which significantly increases the energy deposition of spark by simultaneously improving the energy storage and discharge efficiency. The discharge and ignition characteristics of LHSI were investigated based on the discharge waveforms and high-speed photography. The results show that the discharge efficiency of LHSI can reach 62.4% with the single-pulse stored energy of 100 J while that of conventional high-energy spark igniter (HSI) is only 28.2%. The ignition process produced by such a high-energy spark is firstly reported in a scramjet combustor. An initial flame kernel with a larger size and higher combustion intensity can be produced, which is capable of igniting the cavity with proper local equivalence ratio rapidly and reliably. Compared with HSI, the ignition process of LHSI is more active and the ignition limit can be obviously extended. A novel tail flame ignition mode is observed. It can be concluded that the spark ignition with greater energy deposition is worthy to be further studied in scramjet.

Influence of the Ignition Method on the Characteristics of Propellant Burning in the Context of the Geometric Burning Model

Mathematical models for the simulation of the operation of various projectile-throwing systems are continuously modified, simultaneously with the development of propellants. For these models, properly determined values of energetic ballistic characteristics of propellants are very important. This paper presents an original test and the results of closed vessel comparative investigations. The study analyses specific combustion characteristics of single-base propellants using conventional black powder ignition, plasma ignition, and gas ignition. The results of the study indicate the need to take into account—in the calculation of the burning rate—not only the dynamics of gas pressure changes but also the real (experimental) form function, which differs from the theoretical one resulting from the assumed geometric burning model. The obtained results allow for a critical analysis of the existing methods used for the determination of values of ballistic characteristics of propellants. Further, it will allow for creating pyrostatic test conditions that would reflect the condition of instantaneous ignition of propellant grains over their entire surface in the most realistic way.