Ignition Failure Research Articles

Challenges and solutions for local flame development during spark ignition in a kerosene-fueled scramjet combustor

This study experimentally investigates the challenges and solutions related to the development of local flame into global flame during kerosene spark ignition in a scramjet combustor operating at Mach 4 flight conditions. The ignition and intensity of local flame are explored with different injection pressures. Two potential solutions have been proposed to facilitate the development. The results show that injection pressure plays a critical role in controlling fuel transport into the ignition cavity T1, affecting the local equivalence ratio and local flame formation. Higher injection pressures lead to less fuel transported into cavity T1, resulting in fuel-lean local equivalence ratios and potential ignition failure. Extending the duration of ignition and injection improves ignition reliability. The suppressive effect of dense spray on local flame is the main cause of the local flame development problem. A higher injection pressure can reduce the suppressive effect and increase the intensity of downstream cavity flames. When the downstream cavity flames reach a critical intensity, the flashback of downstream cavity flame will occur, achieving global flames. The dense spray can be thinned out by very low upstream injection pressure, which can also result in global flames.

Time/frequency domain analysis of detonation wave propagation mechanism in a linear rotating detonation combustor

Controlling the rotating detonation combustor (RDC) is crucial for enhancing propulsion system safety, efficiency, and overall performance. Swift and precise identification of the operational mode of RDC is of great significance for refining the propulsion dynamics of detonation-based technologies. In this study, two-dimensional numerical simulations are performed to investigate time-domain characteristics and frequency-domain characteristics of various operational modes of the RDC, hydrogen–air mixtures are used as fuel, and fast Fourier transformation (FFT) is applied to the analysis of frequency-domain. The alteration of the RDC operational mode is achieved through adjustments to the chemical equivalent ratio (ER) of the fuel, spanning from 0.52 to 3.50. Our findings reveal four distinct operational modes within this equivalent ratio range: ignition failure (ER ≤ 0.52 and ER ≥ 3.50), collision failure (ER = 0.85, 1.60 and 1.65), single wave (0.53 ≤ ER ≤ 0.80 and 1.70 ≤ ER ≤ 3.40) and multiple wave mode (0.90 ≤ ER ≤ 1.50). For the ignition failure mode, the detonation waves in RDC decouple from the flame and fail after ignition. In the collision failure mode, the inability of detonation waves to propagate sustainably within the RDC is evident. Frequency-domain analysis underscores the significance of a characteristic low-frequency (0.3 kHz) in distinguishing this mode from others. For single wave mode, it represents the steady and continuous propagation of a detonation wave in the RDC. Frequency-domain analysis reveals characteristic frequencies approximately equal to integer multiples of the propagation frequency (fD), where fD ∼ 10fD serves as the primary characteristic frequencies. The multiple wave mode can be categorized into two subtypes: the forward and reverse single detonation waves appear alternately or the forward and reverse single detonation waves finally co-direction double detonation waves. In the former subtype, characteristic frequencies are integer multiples of the fD, but the amplitude distribution is different with single wave mode. In contrast, primary characteristic frequencies of the latter subtype are fD ∼ 4fD, accompanied by two adjacent characteristic frequencies near each integer multiples of fD. These findings promise advancements in the controllability of RDC and lay the foundations for the development of RDC control systems.

Hypergolic Ignition by Off-Center Binary Collision of Monoethanolamine-NaBH4 and Hydrogen Peroxide Droplets

Hypergolic ignition of H2O2 and MEA-NaBH4 by off-center collision of their droplets was experimentally studied, focusing on the characteristics and mechanism of droplet mixing, droplet heating and evaporation, and gas-phase ignition. The whole collision ignition process was divided into five stages, which were compared, respectively, with that of head-on collision. Under the condition of a slightly off-center collision (for cases where B < 0.35), H2O2 droplets penetrate MEA-NaBH4 droplets after the collision and coalesce with it, but the internal H2O2 drop inside the MEA-NaBH4 droplet does not form a stable sphere. Instead, it rotates and expands inside the mixed droplet. With B increasing to 0.59, the droplets no longer coalesce after collision but separate away, forming satellite droplets. In such cases, multi-ignition mode is observed. When B increases to a certain extent, specifically, 0.85, a grazing collision is observed such that no mass transfer exists during the interaction of droplets, which leads to ignition failure. A theoretical model quantifying droplet swelling rate was established to calculate the volume change of the droplet. It was found that the swelling can be attributed to the flash boiling of superheated internal H2O2 fluid. Meanwhile, the ignition delay time was found to linearly decrease with B at various Wes until the extent where the chemical reaction takes over control, leading to an almost constant time delay defined as RDT. Additionally, the regime of ignition modes corresponding to different droplet mixing features is summarized in the We-B parametric space.

Research on the underground ignition mechanism of ignition fuel and ground simulation experiments

Abstract In the increasingly severe environment of the “dual carbon” situation and the urgent objective demand for national energy transformation and upgrading, the development and use of clean energy have become a new research field and direction. Underground coal gasification technology (UCG) is a clean coal technology that completely bypasses the traditional coal combustion process by converting coal underground into gas and then classifying and recycling it. This method removes sulfur before fuel combustion Nitrogen compounds and particles make it clean like natural gas. The most commonly used ignition method in this technology is chemical ignition. A certain proportion of ignition fuel and main fuel is injected into the underground through pipelines, and then combustion supporting gas is introduced to cause a chemical reaction and generate an open flame to ignite the coal. However, due to the complex internal environment of the pipeline, uneven bending of the pipeline column, and the length of the pipeline exceeding one kilometer, the concentration threshold of the ignition fuel when it reaches the underground igniter cannot be accurately controlled, resulting in ignition failure. In response to the above difficulties, this article has conducted research on the ignition mechanism of ignition fuel, and developed a dedicated ground simulation test bench to conduct ground simulation experiments. The research has strong support for the on-site pilot testing and engineering services of underground coal gasification technology.

Simulated signatures of ignition

Ignition on the National Ignition Facility (NIF) provides a novel opportunity to evaluate past data to identify signatures of capsule failure mechanisms. We have used new simulations of high-yield implosions as well as some from past studies in order to identify unique signatures of different ignition failure mechanisms: jetting due to the presence of voids or defects, jetting due to the capsule fill tube, interfacial mixing due to instabilities or due to plasma transport, radiative cooling due to the presence of contaminant in the hot spot, long-wavelength drive asymmetry, and preheat. Many of these failure mechanisms exhibit unique trajectories that can be distinguished through variations in experimental observables such as neutron yield, down-scattered ratio (DSR), and burn width. Our simulations include capsules using both plastic and high-density carbon ablators and span all high-yield designs considered since the beginning of the National Ignition Campaign in 2011. We observe that the variability in trajectories through the space of neutron yield, DSR, and burn width varies little across capsule design yet are unique to the failure mechanism. The experimental trajectories are most consistent with simulated preheat and jetting due to voids and defects, which are the only failure mechanisms that are indistinguishable in our analysis. This suggests that improvements to capsule compression due to improved capsule quality or reduced preheat have played a primary role in enabling high yields on NIF. Furthermore, our analysis suggests that further improvements have the potential to increase yields further.

Phenomenon of ignition and explosion of high-entropy alloys of systems Ti-Zr-Hf-Ni-Cu, Ti-Zr-Hf-Ni-Cu-Co under quasi-static compression

The phenomenon of ignition and explosive failure of specimens from high-entropy alloys (HEAs) of systems Ti-Zr-Hf-Ni-Cu, Ti-Zr-Hf-Ni-Cu-Co at quasi-static compression tests was found. It physical model is proposed. It is exhibited that the reason for this phenomenon is the release of energy of the oxidation reaction; such reaction is initiated due to the heat released ahead of the shear crack tip at brittle fracture of the specimens under quasi-static compression. It is shown that ignition and failure by explosion are the specific features of brittle fracture for high-entropy alloys containing Ti-Zr-Hf, in general. This phenomenon is realised when certain critical levels of strength and ductility of these alloys are reached. The importance of these critical levels of strength and ductility lies in the fact that they predetermine the maximum permissible level of strength and brittleness for this class of HEAs, above which they lose their structural and functional properties, turning to the energetic alloys capable of explosive release of a significant amount of thermal energy. This specific feature of the high-entropy alloys containing Ti-Zr-Hf outlines the scope of their application and defines the boundary separating structural and functional high-entropy alloys from energetic high-entropy alloys.

Numerical investigation on turbulent flame jet characteristics of a pre-chamber fueled with CH4/O2 and CH4/NH3/O2 mixture under different initial pressures

Ammonia is a very potential carbon-free alternative fuel with extremely low reactivity. The application of ammonia in internal combustion engines faces the risks of ignition failure, low burning rate, and poor combustion stability. Pre-chamber turbulent jet ignition (TJI), which can provide much more ignition energy, is a promising method to ignite ammonia fuel. However, the transient propagation process of pre-chamber jet flame has not been fully investigated yet. In this paper, the propagation characteristic of methane jet flame was numerically studied based on a constant volume combustion system. The supersonic jet flame propagation and Mach disk phenomenon were further analyzed with numerical methods. And the propagation characteristic of methane/ammonia mixed jet flame was investigated. According to the results, the formation and propagation process of methane jet flame has different characteristics at different stages. In High-speed development stage (Stage II) and Low-speed oscillation development stage (Stage III), the penetration distance of flame jet tip is almost proportional to the penetration time. However, the penetration speed of the two stages is significantly different. The change trend of the jet velocity at the outlet of orifice hole can also be divided into four stages: slow increasing, rapid increasing, gradual decreasing, and periodic oscillation. The periodic oscillation of the jet tip velocity and the jet velocity at the outlet of orifice hole is caused by the effect of forward and reverse shock waves. The calculation results of CH4/NH3/O2 mixture jet flame show that the addition of ammonia has significant effects on the flame propagation process in PC, the thermodynamic state of PC, and the propagation characteristics of jet flame. With the increase of ammonia proportion, the maximum pressure of PC gradually decreases and the pressure rise rate slows down. Meanwhile, the two-stage (the high-speed development stage and the low-speed development stage) characteristic of jet propagation process gradually disappears. And the addition of ammonia is more likely to destroy the two-stage characteristic under low initial pressure.

Future zero carbon ammonia engine: Fundamental study on the effect of jet ignition system characterized by gasoline ignition chamber

Ammonia is a carbon-free fuel with tremendous potential for clean internal engine applications in the future. However, the combustion and emissions limitations of ammonia fuel have impeded the development of ammonia engine. As a combustion enhancement technology, the ignition chamber (pre-chamber) jet ignition system has emerged as an effective solution to address the challenges associated with ammonia combustion. This study utilized a high-speed camera to capture the evolution of jet and the combustion processes of ammonia. The combustion method entailed the injection of gasoline into the ignition chamber, while ammonia was injected into the main chamber. The experimental results demonstrated that ignition chamber jet ignition system significantly enhanced ammonia combustion and shortened the combustion duration as compared to spark plug ignition system. The study involved evaluating the ammonia combustion performance under different equivalence ratios (1.0 and 0.8) while comparing it to various gasoline energy percentages (2.5%, 2.0%, 1.5%, and 1.0%). The results revealed that the combustion performance at 1.5% was superior to other gasoline energy percentages. Additionally, in comparison to ignition chamber outlet diameter of 4.5 mm and 6.0 mm, it was found that the 3.0 mm diameter exhibited weak ignition capability, resulting in a 107.1% and 40.3% increase in ignition delay at the equivalence ratio of 0.8, and ignition failure at the equivalence ratio of 0.6. However, its high jet velocity induced a more homogeneous mixing of radicals with ammonia/air, leading to a 30.6% reduction in rapid combustion and a 43.1% decrease in combustion duration at the equivalence ratio of 0.8. Additionally, the investigation of equivalence ratios (0.8, 1.0, and 1.1) demonstrated that the fastest initial combustion of ammonia occurred at the equivalence ratio of 0.8, with an ignition delay of only 4.7ms. Therefore, an appropriate reduction in the equivalence ratio could enhance the ammonia combustion efficiency to some extent. The findings of this study provide a fundamental ignition technique for future applications of zero carbon ammonia engines.

Urban Environment and People’s Perception on Risk Reduction in Fire Related Hazards in Srinagar City

This study aims to understand people’s risk perception to environmental hazards especially that of fires in context to an urban area. The fire is one of the major disasters in an urban environment but evidence of the effectiveness of education interventions against fire risks is limited. Fires start in three main ways i.e. accidents (misuse of appliances), deliberate ignition and equipment failure (electrical malfunction) and produce smoke and toxic gases which could be extremely fatal to those exposed to it hence the need for prevention and protection from spreading fires by delaying ignition period to allow people more time to escape and for the fire brigade to arrive at the incident. Urban disasters especially fires have tended to receive a baffling lack of response from aid agencies indicating major gaps in urban preparedness. Srinagar city is faced with inadequacy in responding to fire disasters of high magnitude and rescue teams have failed in many of the occasions to live up to expectations. The study area (Srinagar City, J & K) which is urban in nature and character has recorded highest number of fire incidents in last so many years, claiming dozens of lives and damaging property worth crores. The present study is an attempt to assess the people’s risk perception to fire hazards and their prevention, mitigation and preparedness measures in residential, commercial, educational and health related buildings. For this purpose both primary as well as secondary data has been used. The overall scenario reveals that the perception of selected respondents gives a very poor result, as more than 40 % of them either have no knowledge about the fire fighting equipment or lack their use during fire incidents. Factor identification has been done on prior knowledge upon which emphasis was on people’s perception, preparedness and mitigation measures adopted by different stakeholders.

Numerical Investigations of Combustion Dynamics and Thermo-Mechanical Stress in the Ignition Assistance System for Small Aircraft Engines

ABSTRACT The utilization of ignition assistance devices offers an effective solution to overcome the challenges associated with ignition control in the development of propulsion systems for unmanned aerial vehicles (UAVs) that rely on sustainable aviation fuels. These devices actively control the combustion process to ensure successful ignition at different altitudes. The objective is achieved by introducing a controlled thermal energy deposit into the combustion chamber, mitigating potential ignition failures. This research presents a comprehensive analysis of the ignition characteristics and subsequent flame structure based on varying electric-circuit energy inputs, employing three-dimensional simulations. The ignition delay patterns are further examined from a fuel chemistry perspective, specifically focusing on the negative temperature coefficient (NTC). Additionally, this study introduces a strategic analysis of the thermo-mechanical stress experienced by the ignition assistance device when subjected to the impact of the spray-jet flame. To accomplish this, a coupled simulation approach combining computational fluid dynamics (CFD) and finite element analysis (FEA) is employed to analyze the transient wall stress. The parametric inputs obtained from the CFD simulations facilitate the FEA analysis, revealing critical mechanical-thermal stress accumulation on the heating element of the ignition assistance device.

Taguchi method-based evaluation of thermal hazard of lift-off pyrotechnics under various storage conditions

This study employed the Taguchi method and analysis of variance to investigate the factors that influence the deterioration of the lift-off pyrotechnics when they are stored under various relative humidity (RH) and temperature conditions. A field emission scanning electron microscope and an energy-dispersive X-ray spectroscope were used to observe the microstructures and elements of pyrotechnic samples. Differential scanning calorimetry (DSC) and Vent Sizing Package 2 (VSP2) were applied to measure the relationship between the trace heat flow of the samples and temperature as well as the thermal runaway reactions in a pseudo-adiabatic environment. A DSC analysis and a thermodynamic ASTM E698 analysis were combined to explore the safety of lift-off pyrotechnics and the related thermal hazards.The energy-dispersive X-ray spectroscopy and DSC experimental results revealed that KNO3 is highly soluble. However, when RH and exposure time increased, the surface dissolution of oxidants decreased the height of the second exothermic peak, resulting in incomplete combustion and ignition failure. The ASTM E698 thermokinetic analysis results indicated that the apparent activation energy (Ea) of the samples increased substantially after being immersed in deionized water. Notably, the Ea of colored smoke increased from 46.88 to 155.91 kJ/mol, indicating that the examined pyrotechnics were more sensitive to a decrease in temperature than to an increase in humidity. A large amount of water can be used to alleviate the reactivity of pyrotechnics and thus reduce pyrotechnic hazards. The VSP2 analysis results indicated that the self-boosting rate of the samples was greater under 40% RH than under pristine conditions; however, this rate decreased substantially under 80% RH and after immersion in deionized water. The results of the Taguchi experiment and analysis of variance revealed that humidity contributed 63.60% and 50.86% to Ea and maximum pressure, respectively. Accordingly, controlling humidity should be prioritized to diminish the hazard of storing pyrotechnics.

Forced ignition of premixed cool and hot DME/air flames in a laminar counterflow

Recently, low-temperature chemistry (LTC) and LTC-induced cool flames have attracted extensive interest since they can substantially influence the ignition process and accelerate the subsequent hot flame propagation. However, it is unclear how the flow affects the forced ignition of a cool flame and its subsequent transition to a hot flame. In this study, we conduct transient 2D simulations for the forced ignition processes of premixed cool and hot flames in a laminar, axisymmetric, counterflow configuration with well-defined flow field. Different ignition energies and strain rates are used to ignite and stabilize cool and/or hot flames in a counterflow. The critical conditions for the ignition of cool and hot flames are identified, and the cool flame kernel quenching and its transition to hot flame are discussed. It is found that the ignition energy determines the highest temperature and thereby controls the thermal runaway process. The strain rate influences the flame kernel propagation and the transition from cool flame to hot flame. A large strain rate may quench the cool flame, while a small strain rate may lead to the transition from cool flame to hot flame due to the sufficiently long residence time. Therefore, cool flame ignition and stabilization can only be achieved within a certain range of strain rates. Furthermore, an ignition regime diagram in terms of ignition energy and strain rate is proposed, and four regimes are identified: (I) only cool flame, (II) only hot flame, (III) ignition failure, and (IV) transition from cool flame to hot flame (with appearance of double flame structure). These results provide new insights into how the flow affects the cool flame ignition and transition.

Detection and identification of cylinder misfire in small aircraft engine in different operating conditions by linear and non-linear properties of frequency components

We suggest an approach for detecting and identifying ignition failure on a internal combustion engine used in aviation through the analysis of vibration time series. The research is carried out at the experimental stage, where time series of vibrations are collected from sensors installed in various parts of the facility at various rotational speeds and various operating conditions (no failure/failure of a selected piston). The time series were decomposed into periodic components centered around dominant frequencies. Data with greater dimensionality was statistically described using linear and non-linear indicators in short time windows, and labeled accordingly. Instead of examining the statistical significance of the characteristics of individual groups, machine learning classification methods were used, which allowed to distinguish the operating state of the engine (damaged/undamaged), and also to identify a specific unfired cylinder. The use of non-linear indicators allowed us to obtain 100% classification accuracy with a small number of samples.

Low-temperature structural deformation and fragmentation of lead styphnate by in-situ experiments and calculation

As one of the most used pyrotechnic composites in spacecraft pyrotechnic devices, the reliability of lead styphnate (LS) in a cryogenic environment needs an adaptability evaluation before the deployment of new deep space exploration programs. Nonetheless, there is a limited understanding of the effects of low temperatures on LS. Herein, we have designed cryogenic storage experiments with a low-temperature in-situ methodology to explore the effects of low temperatures on the properties and performance of LS. By comparing the experimental data before, after storage, and at low temperatures, LS exhibited unique characteristics and failure behaviors at low temperatures than at high temperatures. After storage, the impact sensitivity of LS increased sharply due to particle fragmentation, whilst the flame sensitivity of LS decreased significantly at low temperatures. Employing in-situ powder x-ray diffraction (PXRD) characterization and ignition tests, the low-temperature ignition failure of LS is thought to be closely related to the distortion of the crystal structure of LS, resulting in a “structural shutdown” at −80 °C. Our study disclosed the properties of LS at low temperatures and provided feasible research methods for other energetic materials, aiming to prevent possible future risks and help to establish test standards at low temperatures.

A numerical investigation of plasma-assisted ignition by a burst of nanosecond repetitively pulsed discharges

Nanosecond repetitive pulse discharges (NRP) are a promising technology to promote the ignition of a lean reactive mixture. The success or failure of ignition results from complex interaction phenomena between the plasma generated by the discharge and the properties of the turbulent flow. This work presents two approaches for modeling plasma-assisted ignition scenarios resulting from NRP discharges. The first consists of a low-order model based on dimensionless analysis, while the second involves a Large Eddy Simulation (LES) of the reactive turbulent flow that requires high-performance computing. Both methods are presented and successfully applied to an experimental setup, which was specifically designed to study the influence of flow operating conditions and electrical discharge properties on plasma-assisted flame ignition.The simple dimensionless analysis can identify coupled and decoupled regimes, which always lead to ignition success or failure, respectively. However, the model is too crude to predict the fine interactions between plasma kinetics, combustion chemistry, and flow dynamics that control the formation of the reactive core in partially coupled regimes. The LES provides a means to capture these complex interaction mechanisms. A quantitative analysis of the reactive kernel growth has been performed by numerically reconstructing the OH-PLIF signal measured by the camera. A very good agreement is observed, validating the numerical strategy for plasma assisted combustion.

Fundamental Experiment of Ignition and Flame Development in Turbulent Jet Ignition Ignited Methane Jet Flame

ABSTRACT In heavy-duty natural gas engines, diesel is usually injected before natural gas to initiate methane combustion. However, such an approach requires additional fuel and precise injection strategies. In the present work, an alternative approach of pre-chamber turbulent jet ignition (TJI) ignited methane jet flame is performed experimentally. The underlying mechanism of TJI-HPDI jet combustion is investigated in an optically visualized constant-volume combustion chamber with an active pre-chamber. It is found that with the increase of the injection-ignition delay (ti), the combustion process undergoes several transitions. In addition, the success ignition region and ignition failure region separated by ti and T MI are discerned on the ti-T MI diagram. As ti increases, there is an initial rise in both the mean flame front velocity and peak pressure, followed by a subsequent decrease This behavior highlights the TJI-HPDI system’s notable advantages in expanding the lean combustion limit and enhancing overall combustion characteristics compared to premixed combustion. These advantages can be attributed to the mixture stratification and turbulence. Furthermore, pre-chambers fueled with hydrogen can further improve the intensity and energy of the turbulent hot jet, which further decreases the critical injection-ignition delay to initiate global flame propagation in the TJI-HPDI system. The present work deals with real engineering technologies, and it will provide new insights into the design and control of TJI-HPDI engines, especially for heavy-duty natural gas engines.

Investigation of the effects of flame surface development on the ignition mechanism of aero-engine combustors

Large eddy simulation was employed to simulate the effects of different vane angles of the primary and pilot stages on the ignition process of a combustor under normal temperature and pressure conditions. The simulation results of different vane angles of the pilot stage were then verified experimentally. Kernel initiation and flame propagation in the cases of ignition success and failure were analysed. It was found that in the ignition failure case, the flame kernels are confined to the downstream zones of the venturi and cannot propagate radially, and almost no negative displacement exists in the axial direction. However, in the ignition success case, sub-fire kernels are always present outside the radial boundary of the primary stage. Five ignition modes were finally proposed: (I1) typical ignition, (I2) relatively high-speed ignition, (I3) single-kernel alternating dominant, (I4) main kernel dominant, and (I5) dual-kernel dominant modes. Using high-speed photography, the flame shape changes and ignition characteristics in the cases of successful and failed ignition with different pilot-stage vane angles were investigated.

Efficiency analysis of ignition by Nanosecond Repetitively Pulsed discharges using a low-order model

Plasma-assisted combustion is an interesting method to promote the ignition of a lean reactive mixture instead of conventional spark plugs. Especially, Nanosecond Repetitively Pulsed (NRP) discharges technique is an energy-efficient way to initiate and control combustion processes. Ignition success or failure results from the competition between the discharge energy accumulation, the gas residence time in the discharge region, and the combustion chemistry. Plasma-assisted ignition is modeled here by a Perfectly-Stirred Reactor (PSR) whose volume represents the one surrounding the interelectrode region. NRP discharges are applied inside the reactor to initiate the combustion of the injected mixture. This model numerically identifies a plasma-assisted ignition efficiency map in terms of the amount of energy per pulse and the pulse repetition frequency, at low CPU cost. A criterion based on the residence time, interpulse time, and chemical time is introduced to predict the successful formation of a reactive kernel. This criterion is successfully validated by analyzing the plasma-assisted PSR solutions.

Temperature and flame structure imaging in kerosene swirl-stabilized spray flames at low air flow using TLAF and OH-PLIF

Air flowrate is an important parameter for airbrast nozzles and low air inlet flow rate in airbrast type combustors will lead to worse atomization, combustion instability, and increased pollutant emissions. Using non-linear excitation regime two-line atomic fluorescence (NTLAF) thermography imaging and planar laser-induced fluorescence of hydroxyl radical (OH-PLIF), temperature and flame structure in the near-nozzle area are investigated at different low air flow rate to study the combustion deterioration of kerosene swirl-stabilized spray flames. In this concerned area, combustion occurs mainly at the near-wall region but a few OH signals are present at the centerline region except for the kerosene LIF particles. With the air supply getting low, the near-wall OH signals get low, corresponding to the change of indium Stokes and anti-Stokes fluorescence. The temperature in the centerline region is presented to be reduced and the region for the temperature threshold filter expands, indicating the reduction of the downstream hot combustion products brought back by weak swirl, which is closely related to the extremely low air flowrate. Under extremely low air flow rate, the highly fluctuating temperature and weak gas-liquid mixed combustion at the centerline area may tend to cause combustion instability or ignition failure.

Analysis of Ignition Test Failure of Solid Rocket Engine

This paper reviews the ignition failure of a solid rocket engine in a flight test. A fault tree is established to investigate and analyze the causes. After a series of ground tests to reproduce the faults, it is considered that the humidity of the igniter is the main reason affecting the normal ignition of the engine, and follow-up improvement measures are formulated.