Ignition Experiments Research Articles

Experiments and numerical simulation on the suppression of explosion of propane/air mixture by water mist

Effect of water mist on minimum ignition energy (MIE) and lower and upper flammability limits (LFL and UFL) of C3H8–air mixtures were investigated by experiments and numerical simulation. Ignition experiments were performed in a combustion tube. Polydisperse water mist with a Sauter mean diameter of D32 = 21 µm was generated by a piezoelectric atomizer. Mixture was ignited by an exploding wire heated instantaneously by electrical discharge. Ignition probability follows the cumulative probability distribution function of energy density, i.e., energy per unit volume of the wire. Water mist increases minimum ignition energy density (MIED) defined at 50% ignition probability when the equivalence ratio φ < 1.0 and φ > 1.3. However, for 1.0 < φ < 1.3, the suppression effectiveness was scarcely observed. In numerical simulation, water mist was assumed to be an imaginary ideal gas and evaporation process was expressed by a chemical reaction. Ignition energy is added in the flame kernel at the center and the flame propagates spherically if ignited. This model can predict MIE of the mixture without water mist reasonably. MIE increases nonlinearly with the mass fraction of water mist Y0 and flammability range narrows. At Y0 = 0.146 and beyond, the mixture of any φ becomes unable to be ignited. Relative suppression effectiveness factors Se and Ss are newly introduced for experiments and simulation, respectively. Comparison of Se with Ss shows that the water mist is not so effective as expected by simulation. The life time of a droplet before evaporation is much longer for the water mist of D32 = 21 µm than the residence time in the flame, and only a part of water mist can evaporate in the flame zone. To make full use of the suppression potential of water mist, the mist diameter should be sub-5 µm.

Study of Visualization Experiment on the Influence of Injector Nozzle Diameter on Diesel Engine Spray Ignition and Combustion Characteristics

The elementary research of spray and combustion is of great significance to the development of compactness of modern diesel engines. In this paper, three injectors with different nozzle orifice diameters (0.23 mm, 0.27 mm and 0.31 mm) were used to study the diesel spray, ignition and flame-wall impingement visualization experiment. This paper studied the influence of different nozzle sizes on the trends of spray, ignition and flame diffusion under the flame-wall impinging combustion and used the flame luminosity to characterize the soot generation in combustion. By analyzing the quantitative data, such as spray penetration, ignition delay, flame area and flame luminosity systematically, it was shown that the smaller nozzle benefitted diesel combustion to some extent. The 0.23 mm nozzle injector in these experiments had the best fuel-air mixing effect under 800 K. The length of the spray liquid under the 0.23 mm nozzle condition was 19% and 23% shorter than that of 0.27 and 0.31 mm, respectively. Smaller orifice size of the nozzle can help to reach the gas ignition conditions more effectively. Without liquid fuel impingement, the simple flame-wall impingement will not change the trend of the nozzle influence on combustion. The total amount of accumulated soot according to the approximate luminosity spatial integral calculation in the combustion process was reduced by 37% and 43% under 0.27 mm and 0.23 mm nozzles, respectively, which is favorable for the clean combustion of diesel engines.

Counterflow ignition and extinction of FACE gasoline fuels

The demand for petroleum-derived gasoline in the transportation sector is on the rise. For better knowledge of gasoline combustion in practical combustion systems, this study presents experimental measurements and numerical prediction of autoignition temperatures and extinction limits of six FACE (fuels for advanced combustion engines) gasoline fuels in counterflow flames. Extinction limits were measured at atmospheric pressures while the experiments for autoignition temperatures were carried out at atmospheric and high pressures. For atmospheric pressure experiment, the fuel stream consists of the pre-vaporized fuel diluted with nitrogen, while a condensed fuel configuration is used for ignition experiment at higher chamber pressures. The oxidizer stream is pure air. Autoignition temperatures of the tested fuels are nearly the same at atmospheric pressure, while a huge difference is observed as the pressure is increased. Unlike the ignition temperatures at atmospheric pressures, minor difference exists in the extinction limits of the tested fuels. Simulations were carried out using a recently developed gasoline surrogate model. Both multi-component and n-heptane/isooctane mixtures were used as surrogates for the simulations. Overall, the n-heptane/isooctane surrogate mixtures are consistently more reactive as compared the multi-component surrogate mixtures. Transport weighted enthalpy and radical index analysis was used to explain the differences in extinction strain rates for the various fuels.

Oxidation of di-n-butyl ether: Experimental characterization of low-temperature products in JSR and RCM

The oxidation of di-n-butyl-ether (DBE) was performed in a jet-stirred reactor (JSR) at 1 atm, 520 and 530 K, and from 480 to 670 K at 10 atm, at a residence time of 1 s, an equivalence ratio of 0.5, and an initial fuel concentration of 5000 ppm. Ignition experiments on DBE/air mixtures were also performed in a rapid compression machine (RCM) under stoichiometric conditions, 5 bar, and from 550 to 630 K. Low-temperature products formed in JSR and RCM experiments were characterized. To this end, high-resolution mass spectrometry analyses (HRMS) with flow injection analyses or ultra-high pressure liquid chromatography coupling were used to characterize hydroperoxides and diols (C8H18O3), ketohydroperoxides (C8H16O4), carboxylic acids (C2H4O2, C3H6O2, C4H8O2), di-keto ethers (C8H14O3), and highly oxygenated molecules (C8H14O5, C8H16O6, C8H14O6, C8H14O7, C8H16O8, and C8H14O9) resulting from up to five O2 additions on fuel's radicals. Whereas HOMs are of minor importance in combustion, they are considered key species for the formation of secondary organic aerosols. In addition, cyclic ethers and esters (C8H16O2) were observed. Heated electrospray and atmospheric pressure chemical ionizations (HESI and APCI) were used in positive and negative modes for MS analyses. H/D exchange with D2O was used to confirm the presence of –OH or –OOH groups in the products. The present results show that DBE oxidation proceeds similarly under JSR and RCM conditions. Whereas the CH2 groups neighboring the ether group are the most favorable sites for H-atom abstraction reactions, speciation indicated that other sites can react by metathesis forming a large pool of intermediates and products. Our kinetic reaction mechanism needs to be extended for simulating the formation of newly detected species.

Influences of initial coal concentration on ignition behaviors of low-NOx bias combustion technology

In order to provide the key parameters of initial coal concentration to low-NOx bias combustion technology and enrich the pulverized-coal bias combustion theory, pilot-scale ignition experiments of bias coal streams were carried out using a 250-kW fuel input bias combustion facility. The experimental results including combustion temperature, unburned residues, gas species, and flame spectra were collected. The influences of initial coal concentration on the ignition behaviors of an Indonesian subbituminous in a reducing atmosphere were studied. Our findings show that as initial coal concentration increased, the intensity of visible light and the carbon burnout progressively increased, while the ignition distance and the fuel NOx formation continually decreased. It was observed that the region of continuous flame became successively concentrated, and the flame stability was increasingly enhanced, indicating that the ignition behaviors improved in a gradual way. Furthermore, the mechanism of the combined homo-heterogeneous ignition changed to homogeneous ignition. To be specific, at initial coal concentrations of 0.33 kg/kg and 0.41 kg/kg, the homo-heterogeneous combined ignition mechanism occurred. While at an initial coal concentration of 0.53 kg/kg, the mechanism changed to homogenous ignition. For a tangentially-fired pulverized-coal boiler burning the Indonesian subbituminous, the highest initial coal concentration of the horizontal bias combustion burners can be designed as 0.53 kg/kg, which will be beneficial to the strong ignition and low-NOx emission.

Determination of kinetic parameters of exothermic condensed phase reaction using the energetic material ignition delay data

The kinetic parameters of condensed phase global reaction are required to calculate temporal and energetic characteristics of the ignition and combustion of energetic materials (EMs). The heating rate of EM in these processes exceeds 1000 K/s and therefore the kinetic data obtained via using classical thermal analysis methods with heating rate of 1–50 K/min may not provide the processes adequate description. A solution to the problem was suggested more than 50 years ago by Merzhanov who noticed a possibility to determine required kinetic parameters from the EM experimental ignition delays. However, mathematical background and justification for this approach has not been performed. It is commonly assumed that the approach yields the true kinetics at high heating rates of EMs. The present work aims to verify the validity of Merzhanov's approach. Numerical calculations were performed using transient mathematical models of the EM ignition and the results of virtual ignition experiments were processed using Merzhanov's ignition criterion. The deliverables were the values of kinetic parameters that substantially differ from those used as input data in numerical calculations. The paper concludes about necessity of elaborating mathematically substantiated techniques for determining kinetic parameters of global exothermic condensed-phase reaction via using the EM ignition delays.

Auto-Ignition and Reaction Front Dynamics in Mixtures With Temperature and Concentration Stratification

In-cylinder thermal and concentration stratification is omnipresent in the operation of internal combustion engines, especially for various types of direct injection engines. Meanwhile, mixture stratification and ϕ-sensitivity is frequently adopted in advanced compression ignition strategies to modulate heat release profile and control combustion phasing, such as homogeneous charge compression ignition (HCCI) with partial fuel stratification (PFS), and premixed charge compression ignition (PCCI). Hence, ignition and combustion mode evolution in a stratified charge are of substantial significance in the understanding and prediction of combustion in advanced compression ignition engines. To probe complex combustion in a stratified charge, we have performed one-dimensional direct numerical simulations with detailed chemistry and transport, using a recently developed open source reacting flow CFD platform based on OpenFOAM. N-heptane is adopted in this work as a typical fuel exhibiting low temperature chemistry. Temperature and equivalence ratio gradients are varied among the simulations to observe ignition and the subsequent combustion development. Three stages of heat release are identified, including the low temperature chemistry chain branching, H2O2 chain branching and CO oxidation, consistent with the recent ignition experiment for lean n-heptane air mixture in a rapid compression machine (RCM). Reaction fronts induced by these oxidation stages are found to be unaffected by diffusion process and exhibit unique propagation features. The results provide useful guidance to the understanding of combustion in a stratified charge and shed light on the development of novel low temperature combustion strategy for advanced compression ignition engines.

Comparison on Laser Ignition and Combustion Characteristics of Nano- and Micron-Sized Aluminum

ABSTRACT This paper presents a comparative study on the laser-induced ignition and combustion characteristics between nanometer-sized aluminum (nano-Al) and micron-sized aluminum (micro-Al) powder stacks. Six different sizes of Al powders (56.0 nm, 74.4 nm, 93.4 nm for nano-Al and 2.9 μm, 6.1 μm, 10.8 μm for micro-Al) were selected to conduct ignition and combustion experiments, at the same operation conditions in the static air flow with atmospheric temperature and pressure and 55% relative humidity. The results demonstrated that ignition delay time of nano-Al is much lower than that of micro-Al. The size of nano-Al has a weak effect on ignition delay time. Whereas, the size of micro-Al has an exponential effect on ignition delay time. The combustion of nano-Al is more intense and the self-maintenance performance is better than micro-Al. Finally, a comparative model on the ignition and combustion difference between nano-Al and micro-Al was built, which comprehensively considers the influences of particle core size, oxide shell thickness and porosity. This study will be helpful to recognize the difference of ignition and combustion characteristics between nano-Al and micro-Al and promote the application in solid rockets.

Development of single-shot frequency-resolved optical gating for characterizing the instantaneous intensity and phase of LFEX laser pulses

Frequency-resolved optical gating (FROG) is a novel means of measuring the fast motion of a critical density surface during relativistic laser–plasma interaction. Herein, we present a design and demonstration results for a new single-shot FROG system and optical transport system for characterizing the instantaneous intensity and phase at the LFEX (Laser for Fast Ignition Experiment) laser facility at the Institute of Laser Engineering of Osaka University. At LFEX, the laser intensity at the vacuum window is intrinsically high because of two unique properties, namely, the large F-number of the off-axis parabolic mirror and the small radius of the interaction chamber. Consequently, to obtain an accurate FROG trace, attention must be paid to spectrum modulation due to self-phase modulation. The appropriate laser intensity for FROG operation was investigated experimentally, and an optical transport system with an energy attenuator composed of reflective optics was designed to eliminate the concern of spectrum modulation from measurements. A FROG trace recorded at LFEX shot with 161 J energy was reconstructed 100 times using an iterative phase-retrieval algorithm. Despite some differences in structure, the reconstructed spectrum agrees reasonably well with the spectrum obtained by a time-integrated spectrometer. This shows that the developed FROG system and the optical transport system can measure the instantaneous intensity and phase of a laser pulse without spectrum modulation.

Agglomeration and combustion characteristics of solid composite propellants containing aluminum-based alloys

Agglomeration in solid composite propellants is known to exacerbate two-phase flow losses. In this experimental study, we investigate the substitution of aluminum particles with metallic alloys in order to reduce agglomeration in aluminized propellants. We consider five different aluminum-based alloys: Al-Mg, Al-Ni, Al-Si, Al-B, and Al-Zn. Through thermogravimetric-differential scanning calorimetry measurements, we find that all five alloys can increase the initial oxidation temperature relative to a baseline Al propellant, but that only Al-Si and Al-Zn exhibit lower melting temperatures. Laser ignition experiments show that Al-Mg produces the most balanced combination of a short ignition delay time and a short self-sustaining combustion time. High-pressure experiments at 0.5 to 3 MPa show that Al-Si has a markedly higher burning rate than the baseline Al propellant, while Al-Mg and Al-Ni have the lowest pressure exponents. High-speed microscopic surface imaging at 0.5 and 1 MPa shows that Al-Ni produces the largest reduction in agglomeration, with an average agglomerate size some 30% smaller than the baseline value. By contrast, Al-Zn produces the worst agglomeration, with an average agglomerate size around 15% larger than the baseline value. From these findings, we propose a qualitative phenomenological mechanism for agglomeration in metallic-alloy propellants based on a competition among four distinct effects: the metal melting temperature, the adhesive force of the agglomerates, the propellant burning rate, and micro-explosions. We then analyze the agglomeration of the different alloys using the proposed mechanism. As well as providing new experimental data on the agglomeration, ignition and combustion characteristics of solid composite propellants containing aluminum-based alloys, this study reinforces the notion that the agglomeration and combustion performance of aluminized propellants can be optimized through a judicious choice of alloying elements.

Ignition of methane/air mixtures with inert and reactive particles heated by radiation

This study utilizes a self-designed experimental apparatus to heat inert silicon carbide and reactive coal particles via thermal radiation in order to ignite methane-air mixtures. The objective of these ignition experiments is to determine the difference in ignition characteristics between inert and reactive particles. Therefore, a series of ignition experiments with varying types of particles, irradiances, particle sizes, and fuel mixture equivalence ratios were performed to determine the effects of these parameters on ignition time and ignition temperature. The results of the experiments indicate that ignition time and ignition temperature are both influenced by the fuel mixture equivalence ratio, particle type, and particle size, while irradiance only influences ignition time. Ignition temperature and time were observed to be higher and longer, respectively, for reactive particles than inert particles. Furthermore, ignition temperature is inversely proportional to particle size; while, ignition time is directly proportional to particle size and inversely proportional to irradiance. Chemical reaction of coal particles narrowed the flammability limit of the fuel mixtures, results in a longer time and higher ignition temperature, and causes a more powerful ignition than that of inert particles due to the possibility of secondary ignition.

Effect of nano Aluminum on Thermal Behavior and Ignition Characteristics of Al/KClO4 Thermite Composition

Ignition experiments of micron size Al/KClO 4 (ALCLO) thermite composition was carried out at high heating rate (40°C/min.) using DTA (differential thermal analysis), and it was observed that no ignition took place up to 700°C. Similarly in case of STA (simultaneous thermal analyzer) experiments, no ignition peaks were found up to 1100°C at 20/min. ALCLO when ignited in a bomb calorimeter for heat of combustion output measurement it produced a large amount of heat of combustion (2100 cal/g). To study the ignition aspect, DSC (Differential Scanning Calorimetry) experiments were carried out for ingredients and compositions at different heating rates, i.e., 10, 20, 25, 28, and 30°C/min. Nano-Al was used as additive to understand the ignition behavior below 700°C and experiment was successful. It was observed that a sharp ignition peak is obtained below 700°C. The ignition temperature was found below 600°C in DTA for nano-added ALCLO. Ignition mechanism is reported for the compositions by using XRD (X-ray Diffractometer). Effect of heating rate and additives on ignition temperature has also been reported in this study. Again, with increasing nano-Al weight ratio, ignition took place at lower heating rate (25°C/min).

Effects of ignition condition on the initiation characteristics of rotating detonation wave in plane-radial structure

The ignition experiments of the plane-radial rotating detonation engine have been tested to identify the impact of ignition methods and ignition positions on the initiation characteristics of rotating detonation wave. The low-energy spark plug, high-energy spark plug and H2/O2 pre-detonation tube are used to ignite the engine. Results show that, for different ignition methods, the initiation process undergoes five stages: ignition, disordered deflagration, circumferential flame-wave propagation, unstable rotating detonation and stable rotating detonation. As the ignition energy increases, the circumferential flame wave is more easily obtained in combustor, and the initiation time of rotating detonation wave is shortened with better consistency. In this paper, the shortest initiation time is obtained by the H2/O2 pre-detonation tube. For the low-energy spark plug, as the mass flow rate increases, the average initiation time shows a downward trend with local fluctuation. When the rotating detonation engine is ignited close to the injection surface, the initiation time is shortened and fluctuates more slightly, and the optimal ignition position is obtained in the plane-radial combustor. Under specific operating conditions, changing the ignition position may affect the propagation mode of rotating detonation wave in the initial stage, and igniting close to the combustor center is more likely to obtain the multi-head rotating detonation wave. But changing the ignition method or ignition position has little effect on the propagation process and detonation-wave parameters in stable stage.

Laser ignited combustion of graphene oxide/nitrocellulose membranes for solid propellant micro thruster and solar water distillation

Laser ignited combustions are challenging owing to high ignition threshold, poor combustion propagating of the typical energetic materials, e.g., nitrocellulose (NC). Here, reported is the enhancement in both laser ignition and combustion properties of NC by formulating NC/GO composite with controlled microstructure. The results from laser ignition experiments indicate that GO is an efficient additive, enabling low threshold ignition and improving the combustion propagation of NC by introducing pores in NC/GO composite to facilitate convective heat and mass transfer. The NC/GO composite with 20 wt% GO has the maximum combustion efficiency and tremendous gas release, which is demonstrated as a promising solid-propellant for micro thruster. Furthermore, it is found that the energy release of NC/GO can be tuned by adding specific materials, which favors the preparation of advanced function materials by combustion synthesis. As a proof of concept, a self-supporting active carbon/reduced GO/MWNTs (AC/rGO/MWNTs) membrane with a well-defined and interconnected porous structure is prepared by depressing combustion of NC/GO with a small quantity of MWNTs added. The resultant AC/rGO/MWNTs membrane is demonstrated as a high performance photothermal converter for efficient interfacial solar water distillation, delivering a high energy efficiency (94.7% under 1 kW m−2 irradiation), excellent reusability and desalting capacity.

Nano carbides-mediated acceleration of energy release behavior of amorphous boron during ignition and combustion

Action mechanism of nano titanium carbide (nTiC), nano zirconium carbide (nZrC), and nano silicon carbide (nSiC) was studied using a concentrated ignition experimental system, an X-ray diffractometer and a scanning electron microscope. Each nano-carbide was mixed with B in mass ratio of 2/8 and then pressed into tablets, respectively. Furthermore, a sample of amorphous B was also prepared as the control group. All the three nano-carbides showed positive influence on the ignition of B. During the first stage of combustion, only nTiC could increase the maximum emission spectral intensity of the sample, while both nTiC and nZrC helped to increase that during the second stage of combustion. Although the addition of nano-carbides intensified the energy release rate of B (except nSiC), the expansion and diffusion of generated carbon dioxide took large amounts of heat away and reduced the surface temperature of the samples The temperature change in solid-phase exhibited a relationship with the spectral intensity change in gas-phase. The temperature increase was slow during the ignition delay stage, while the first combustion stage proceeded with rapid increase in surface temperature. The high-temperature areas regressed during the second combustion stage, accompanied by the gradual stopping of gas-phase reactions. The components and microstructure of the condensed combustion products (CCPs) were analyzed after the ignition experiment. Results showed that both nTiC and nZrC could react with B to generate corresponding metal borides, capable of promoting the ignition of B. Moreover, the catalysis of produced TiO2 and ZrO2 explain the increase of emission spectral intensity during the second combustion stage. A lot of micropores formed in the CCPs after adding nTiC, which showed a destructive effect of generated gaseous CO2 on the surface oxide layer. In general, nTiC is the top accelerant for B oxidation in this study, while nSiC is at the bottom.

Development of Tritium Tracer Doped Liquid Fuel Target for Inertial Confinement Fusion at the Gekko XII-LFEX Facility

In inertial confinement fusion (ICF), a fuel target containing deuterium and tritium is used. In recent ICF experiments on the Gekko XII LFEX facility at the Institute of Laser Engineering at Osaka University (ILE-Osaka), a target comprised of a polystyrene capsule filled with D2O liquid and a solution of X-ray tracer materials, such as copper, titanium, or chlorine, was developed. In this study, an additional T2O doping technique by which tritium can be mixed uniformly has been developed. The T2O is synthesized by T2 gas using a CuO oxidation catalyst. The T2O is agglutinated by cold trap and transferred to a target cell in which a D2O-solution-filled target is placed. Because polystyrene is slightly permeable for T2O and D2O, D2O is exchanged by T2O and completely mixed. Thus, a uniform tritium-doped ICF target with various materials can be fabricated. The T2O synthesizing and doping system is developed and tested using H2 as a cold run. The H2O is successfully doped to a D2O prefilled target at approximately 50% doping. This scheme will be utilized in future fast ignition experiments at ILE-Osaka.

Monte Carlo particle collision model for qualitative analysis of neutron energy spectra from anisotropic inertial confinement fusion

A Monte Carlo (MC) code simulating the kinetics of two-particle collisions has shown to have certain advantages in the spectral analysis of neutrons from fast-ignition inertial confinement fusion (ICF). The MC code quickly displays neutron spectra produced in the expected fusion plasma kinetics (incl. ion energy spectrum, anisotropy, and collision geometry). This allows to explore various potential mechanisms of neutron production without using time-consuming hydrodynamic or particle simulations and makes it possible to give a feedback to ongoing experiments. The validity of this model was demonstrated in the ”cone-free-shell” fast ignition experiment at the GEKKO-XII - LFEX laser facility, where the model provided a clear explanation for the significant spectral modulation of D(d, n)3He neutrons generated through the interaction between a high-power laser and a long-scale plasma.

Laser-Induced Plasma Ignition Experiments in a Direct-Connect Supersonic Combustor at Mach 3

A new direct-connect supersonic combustor has been designed and tested for the study of plasma-assisted combustion in the ACT-II supersonic combustion tunnel. Laser-induced plasma ignition was investigated in an ethylene-fueled cavity flame holder at Mach 3. Combustor design, geometry, and flow characteristics are discussed in the first part of the paper. The supersonic combustor includes a cavity flame holder, where ethylene fuel is injected, mixed with entrained air, and ignited. Two injector configurations are included, one horizontal and one vertical, which were designed in such a way as to enhance the cavity flow recirculation. Two different plasma ignition mechanisms were considered: 1) a laser-induced plasma located at the center of the cavity, and 2) a spark plug placed on the bottom surface of the cavity. The diagnostics tools tested to characterize the flow include time-resolved pressure measurements, high-speed schlieren visualization and chemiluminescence visualization, and instantaneous planar laser-induced fluorescence of the CH radical. The second part of the paper discusses the results of the comparison between horizontal and vertical fuel injection. The larger backpressurization of the isolator and a more uniform distribution within the cavity suggest a greater heat release and combustion efficiency when the horizontal jet is used.

Comparative study of experimental testing methods for characterization parameters of coal spontaneous combustion

The test method and principle that isothermal difference leading the elevated temperature experiment and the large coal spontaneous ignition experiment are different, data acquisition methods are also different, the content and calculation basis of coal spontaneous combustion characterization parameters and solution are slightly different. In order to realize the comparative analysis of isothermal difference leading experiment and large coal spontaneous combustion experiment, it selects samples of Zhaoxian Coal Mine to conduct large coal spontaneous combustion experiment (defined as ZXDY) and isothermal difference leading experiment (defined as ZXYM), and to make an analysis of the characterization parameters of coal spontaneous combustion, obtaining the characteristics and applicability of the two experimental methods of coal spontaneous combustion characterization parameters.

Enhanced energy coupling for indirect-drive fast-ignition fusion targets

One of the most promising approaches to reach a high gain in inertial confinement fusion is the fast ignition scheme. In this scheme, a relativistic electron beam is generated; this passes through the imploded plasma and deposits parts of its energy in the core. However, the large angular spread of the relativistic electron beam and the poorly controlled compression of the target affect realization of the fast ignition technique. Here, we demonstrate that indirectly driven (that is, driven by X-rays generated inside a gold hohlraum) implosions with a ‘high-foot’ and a short-coast time of less than 200 ps allow us to tightly compress the shell. Furthermore, we show the ability to optimize the symmetry of the imploding shell by changing the hohlraum length, successfully tuning a suitable tube-shaped shell to compensate for the large angular spread of the relativistic electron beam and to enhance the electron-to-core coupling efficiency via resistive magnetic fields. Benefiting from those experimental techniques, a significant enhancement in neutron yield was achieved in our indirectly driven fast ignition experiments. These results pave the way towards high-coupling fast ignition experiments with indirectly driven targets similar to those at the National Ignition Facility. Experiments realizing the indirect-drive fast ignition scheme for inertial confinement fusion are reported. Enabled by a tightly compressed target, an increase of neutron yield is observed.