Static Ignition Research Articles

Innovative Design and Fast Iterative Manufacturing of Micro-Turbojet Engines at Low Cost

The turbojet is the foundation of the gas turbine engine, which combines knowledge of fluid dynamics, thermodynamics, heat transfer, mechanical design, manufacturing, and jet propulsion. This paper describes in detail the inspiration source, design process, fluid dynamics analysis, manufacturing steps, ignition test method and test process of small jet engines. 3D modeling software SolidWorks was used for the preliminary modeling and fluid simulation was performed to optimize the design. Part of the model was produced by 3D resin printing technology, and the turbine engine model was driven by compressed air for no-load testing to verify the feasibility and structural stability of the resin model. Subsequently, some parts were printed with metal materials, combined with traditional machining techniques to complete production and assembly, and finally successfully carried out static ignition tests. The micro turbojet engine designed in this paper has successfully achieved static ignition test and demonstrated the feasibility of efficient development with limited resources and low manufacturing cost. This exploration proves the feasibility of rapid iteration technology route. The market prospect and manufacturing cost of micro turbojet are also analyzed.

Static ignition hazards with plastic containers

AbstractPlastic containers present unique challenges in flammable liquid service, as most plastics are highly electrically insulating, cannot be grounded, and can easily accumulate electrostatic charges. These electrostatic charges result in elevated risks of electrostatic ignitions where the potential for ignitable mixtures exists, including unique and different exposures on the inside and outside surfaces of plastic containers. In this primer, four specific ignition risks are overviewed: (1) flow electrification, (2) splash filling, (3) triboelectrification, and (4) charge accumulation on workers.

A method of risk assessment for static ignitions

This paper presents a method of risk assessment for static ignitions that can be widely used overseas. It describes how the developed risk assessment method identifies static ignition hazards and analyses static ignition risks. This method has been developed on the basis of the flow of procedures in IEC/ISO Guide 51, lessons learned from incidents over 50 years and the survey of the situation of electrostatic risk assessment in Japanese industry, and has been maintained as an implementation guide to assist safety managers since 2008. The method includes a process/operation review; hazard identification for explosive atmosphere formation, charging, electrostatic induction and electrostatic discharges; static ignition risk estimation and evaluation; and risk reduction countermeasures. Tools are also provided to aid implementation: a risk assessment sheet to follow the method and record the results, and 30 check items to identify static ignition hazards. The method with the guide has been adopted by many safety managers in Japan.

Unsupervised Multimodal Anomaly Detection With Missing Sources for Liquid Rocket Engine.

To achieve reliable and automatic anomaly detection (AD) for large equipment such as liquid rocket engine (LRE), multisource data are commonly manipulated in deep learning pipelines. However, current AD methods mainly aim at single source or single modality, whereas existing multimodal methods cannot effectively cope with a common issue, modality incompleteness. To this end, we propose an unsupervised multimodal method for AD with missing sources in LRE system. The proposed method handles intramodality fusion, intermodality fusion, and decision fusion in a unified framework composed of multiple deep autoencoders (AEs) and a skip-connected AE. Specifically, the first module restores missing sources to construct a complete modality, thus advancing the secondary reconstruction. Different from vanilla reconstruction-based methods, the proposed method minimizes reconstruction loss and meanwhile maximizes the dissimilarity of representations in two latent spaces. Utilizing reconstruction errors and latent representation discrepancy, the anomaly score is acquired. At decision level, the model performance can be further enhanced via anomaly score fusion. To demonstrate the effectiveness, extensive experiments are carried out on multivariate time-series data from static ignition of several LREs. The results indicate the superiority and potential of the proposed method for AD with missing sources for LRE.

Make the Rocket Intelligent at IoT Edge: Stepwise GAN for Anomaly Detection of LRE With Multisource Fusion

Anomaly detection (AD) for liquid rocket engine (LRE) is essential to improve the reliability and safety of space launch missions. However, it is difficult for existing methods to implement fast and precise detection with single-source information and absent anomalous samples. The Internet of Things (IoT) enables intelligent LRE AD via edge computing using multisource data. This article proposed an edge-based detection algorithm named stepwise generative adversarial network (StepGAN) for AD of LRE with multisource fusion at the Edge of IoT. StepGAN incorporates deep autoencoder and relativistic generative adversarial network. Through multistage stepwise training with unlabeled normal data, an encoder-generator-discriminator network is obtained to identify LRE anomalies at the edge. In addition, by fusing multisource information at feature level and aggregating neighboring information at decision level during real-time detection, the performance of StepGAN is further improved. To demonstrate its ability for IoT edge-based AD, the proposed method is compared with typical methods, using real static ignition data of LRE as cloud and edge data, and achieves the best result under multiple evaluation indexes. To evaluate the proposed fusing approach, a channel-varying case is carried out and extensive experimental results indicate its effectiveness.

Mechanism of Influence of High‐Speed Self‐Spin on Ignition Transients for a Solid Rocket Motor: a Numerical Simulation

AbstractHigh‐speed self‐spin is one of extreme working conditions that alters ignition internal ballistic performance and can induce ignition abnormalities. To demonstrate the studies on mechanism of interior ballistics as the results of acceleration loads imposed on spinning SRM, the modes of swirl dynamical flow and acceleration‐induced combustion phenomena for igniter and propellant are developed and first taken into account in a new ignition model by user‐defined sources (UDS). To verify the model, the heat transfer, added‐mass and build‐up pressure modes of this ignition model are verified by comparison with static ignition experimental data, second, the swirl flow field mode is validated through comparison between models and by analogy with experimental phenomena, then the numerical model is proved by grid‐independent verification. Dimensionless analysis eliminates diversity in time scales at different periods. The influences of swirl flow, igniter, and propulsion acceleration‐induced combustion on various stages of ignition are studied. It was found that: (1) Time scale in the ignition process of spinning SRM is mainly affected by the igniter‘s sensitivity to rotational acceleration (Aig), whose change is approximately described as an empirical equation based on rotational overload (α) and ignition sensitivity coefficient limit Aig,max; (2) The acceleration effect on propellant combustion is mainly manifested in the pressure peak and the pressure rate, however, it has little effect on the ignition delay; (3) Swirl flow factors are not the main factors affecting the ignition process for small SRMs with small‐contraction nozzles.

Static Fire Danger Estimation Based on the Historical MODIS Hotspot Data Using Geospatial Techniques for the Uttarakhand State, India

Forest fires are more frequent in Uttarakhand state, especially during the months from March to June each year, causing a major impact on forest resources, wildlife habitats, economic and environment. The essential factors favourable to fire danger are the ignition factors and spreading factors. Ignition factors are either natural or androgenic activities; spreading factors are type of vegetation, topographic properties and terrain characteristics and dynamic weather variables such as temperature, relative humidity and precipitation. Vegetation, topographic and terrain conditions are static, whereas the dynamic variables change more frequently in a day. In this study, Static Fire danger Index (SFDI) has been developed from the MODIS TERRA, AQUA and ASTER datasets namely, MODIS Land cover type yearly L3 global 500 m SIN grid (MCD12Q1) and ASTER GDEM. LULC danger index, Slope danger index, Aspect danger index, Elevation danger index and Terrain ruggedness danger Index have been generated from the above datasets based on the historical fire data and field observation. The SFDI has been generated by integrating the above-mentioned indices and categorized into 5 fire danger classes from no fire to very high. The results were compared with the MODIS active fire product (MCD14) and the accuracy of SFDI is 90%, 95.9% and 92.5% for the years 2015, 2016 and 2017 respectively. The SFDI is generated each year with updated MODIS land cover type product with a spatial resolution of 1 km and is useful to understand the spatial pattern of fire occurrence and also determine areas of high fire danger due to the static ignition factors.

Ignition risks associated with migratory antistatic liners at the point of use

Dissipative plastics are often used to reduce risks of static ignition sources in explosive atmospheres. Migratory agents which diffuse to the surface can aid dissipation. The agent attracts ambient moisture to the surface thus decreasing the electrical resistance. In tests it has been found that surface resistance of migratory liners can take around 24 hours to become dissipative. This brings into question whether conditioning periods recommended for surface resistance tests could be masking the ignition risk of materials. Surface resistance, transferred charge and gas probe ignition tests have been carried out to investigate the ignition likelihood further. Rubbing tests indicated that a protective lubricating film formed at around 1 hour that could prevent charge transfer events but subsequent rubbing removed the film leading to charge transfer events. Liner filling tests were set up similar to IEC 61340-4-4. This testing recorded charge transfer events of over 60 nC for all liners even after 24 hours exposure. Liner filling tests with the gas ignition probe produced ignitions with standard insulating liners (no migratory agent) but produced no ignitions or measurable charge transfers for migratory liners. A question remains over the use of charge transfer values to evaluate ignition risks for migratory static dissipative materials and more guidance is sought to help industry manage these risks.

Effect of Static Spark Timing on the Performance and Emissions of a Spark Ignition Engine Using CNG

In this paper, studying the effects of static spark time on the performance and emissions of a spark ignition engine using compressed natural gas. Engine performance and emissions were measured repeatedly at different static ignition time (15° BTDC, 18° BTDC, 21° BTDC and 24° BTDC) with fixed coolant temperature (90°C± 2°C). the results showed that advancing the static ignition time with CNG from 15° BTDC to 24° BTDC at the full load increased the brake power, brake torque, brake thermal efficiency and hydrocarbon by 4.07%, 4.67%, 3.58% and 4.89% respectively, while carbon monoxide and volumetric efficiency doesn’t change effectively at the full and half load conditions.

Combustion Characteristics and Cyclic Variation of a LPG Fuelled MPFI Four Cylinder Gasoline Engine

Abstract Present study deals with to investigate the effect of dual mode of operation on combustion characteristics of engine and cyclic variation in a modified multi-cylinder SI engine. Experiments will be conducted with baseline gasoline and later with dual fuel mode of experiments i.e., gasoline with LPG with different ratios (25%, 50%, 75% and 100% of LPG by mass). Experiment will be carried out with varying speed from 2000 rpm to 4500 rpm in steps of 500 rpm at full load condition with factory set static ignition timing of 5 deg. bTDC to investigate combustion characteristics and cyclic variations. Results revealed that as the LPG percentage increases the peak pressure also increases and it is maximum for 100% LPG for all the speed. At 4500 rpm the percentage increase in peak pressure is 20% for 100% LPG, 9% for 25%LPG, 3% for 50%LPG, 1% for 75%LPG when compared to gasoline at full load. This increase in peak pressure will indicate the LPG will give better combustion properties compared to that of gasoline. Compared to peak pressure, the variation in cycle to cycle for IMEP is less.Net heart release rate shows that gasoline will give the more heat release compare to all other fuels, but LPG will release the heat little earlier than gasoline. Since peak pressure is near to TDC for LPG which results in NHRR to occur earlier than gasoline. Final outcome of the research is LPG will have better combustion properties compared to gasoline but cyclic fluctuations are more for LPG.

Prototype Scale Development of an Environmentally Benign Yellow Smoke Hand-Held Signal Formulation Based on Solvent Yellow 33

We report herein the development of an environmentally benign yellow smoke formulation aimed to replace the environmentally hazardous mixture currently specified for the U.S. Army’s M194 yellow smoke hand-held signal. Static ignition test measurements have identified a replacement candidate that generates a robust fountain of yellow smoke, burning for 15 s from a consolidated cardboard tube configuration. This new formulation meets the burn time parameters outlined in the military requirement and is composed entirely of dry, powdered, solid ingredients without the need for solvent-based binders. In addition, this formulation was found to have relatively low sensitivity to impact, friction, and electrostatic discharge.

Static ignition hazards of “conductive” liquids during container filling

This paper briefly discusses the hazards of “splash filling” containers with liquids that are sufficiently conductive to produce sparks at their surfaces. It is advised that the “2 mm” (2000 micron) maximum safe coating thickness for containers given in Codes and Recommended Practices is unsafe and should probably read “2 mil” (50 micron) instead. For a typical drum filling operation the effect of increased coating thickness in this range is to increase the liquid voltage by a factor of about 80. This paper advises on the appropriate use of dip pipes and other precautions. © 2010 American Institute of Chemical Engineers Process Saf Prog, 2010

Pyrophoric potential of plutonium-containing salt residues

Ignition temperatures of plutonium and the pyrophoric potential of plutonium-containing pyrochemical salt residues are determined from differential thermal analysis (DTA) data and by modeling of thermal behavior. Exotherms observed at 90–200°C for about 30% of the residues are attributed to reaction of plutonium with water from decomposition of hydrated salts. Exotherms observed near 300°C are consistent with ignition of metal particles embedded in the salt. Onset of self-sustained reaction at temperatures as low as 90°C is not precluded by these results and heat-balance models are developed and applied in predicting the static ignition point of massive metal and in evaluating salt pyrophoricity. Results show that ambient temperatures in excess of 200°C are required for ignition of salt residues and that the most reactive salts cannot ignite at low temperatures because diffusion of oxidant to embedded metal is limited by low salt porosity.

Ignition in Nonpremixed Counterflowing Hydrogen versus Heated Air: Computational Study with Skeletal and Reduced Chemistry

Nonpremixed ignition of counterflowing H 2 against hot air is studied numerically with emphasis on developing simplifying approximations to the conservation equations governing this system. We derive and examine a number of different “skeletal” and “reduced” chemical reaction mechanisms that are used to simplify the full kinetic mechanism consisting of 9 species and 19 bidirectional elementary reaction steps. It is found that the use of inherently homogeneous approximations such as the steady-state or partial equilibrium approximations in the derivation of reduced reaction mechanisms can lead to significant errors in this inhomogeneous system. We demonstrate that reaction step R11 (H + HO 2 → 2OH) plays a critical step in kinetically controlled H 2–air ignition, and present a 6-step skeletal mechanism which represents the smallest set of elementary reactions that will provide proper turning point behavior in the first and second ignition limits. A new sensitivity analysis methodology is introduced that quantifies the sensitivity of the system response, particularly near the ignition turning point, to important parameters in the conservation equations. We also examine the so-called decoupled ignition environment approximation in which ignition takes place within a static ignition environment, consisting of the temperature and major species concentration profiles, that is decoupled from and can be solved independently of the minor species profiles.

Development of a 15 kWe spark ignition producer gas engine and some investigations of its in-cylinder processes

A 15 kWe spark ignition producer gas engine (SIPGE) has been developed by machine converting a 17 kWe direct injection diesel engine. The design modifications carried out are combustion chamber geometry, reduction of compression ratio from 17 to 11.5, incorporation of ignition system and mounting of an air-gas mixer. The static ignition timing provided is 35° btdc. The engine efficiency is 28–32%. Wood based Producer gas of calorific value 6 to 7 MJ/Nm 3 is used as engine fuel. This paper reports the development of a simulation model for estimating the in-cylinder process parameters of the SIPGE and an attempt made for its validation.

Using material data in static hazard assessment

AbstractMinimum ignition energy (MIE) test methods for gases, liquid mists and dust suspensions are reviewed. A compilation of gas MIEs is given and applications described both in assessing static ignition risks for flammable liquids and the basic requirements for static grounding. The relevance of liquid electrical properties is discussed and a large compilation provided. MIE interpretation problems are discussed with emphasis on dust suspensions.

The use (and misuse) of bonding for control of static ignition hazards

AbstractIn this paper, specific procedures to minimize potential hazards related to the accumulation of static electricity are addressed. The hazards of concern herein are those arising from the ignition of mixtures of air and flammable gases, vapors, and dusts. Accordingly, concerns related to process operability, sensitivity or reliability of electronic components, or nuisance effects are not considered. Also, ignition of condensed phase explosives or oxygen enriched systems are not specifically included through many of the principles and conclusions discussed below will apply.

Ignition Hazards of Charged Dielectrics in Flammable Environments

Five categories of dielectric materials are discussed that may cause static ignition hazards in an industrial environment. Examples of fires that have been caused by static charge accumulation on nonconducting materials are described. Procedures for evaluating the degree of hazard and for avoiding static spark ignition are recommended.

Some characteristics of liquid-to-metal discharges involving a charged “low risk” oil

Liquids possessing electrical conductivities greater than about 10 pS m −1 may be classified as “low risk” as regards hazardous levels of charge accumulation when loaded into grounded containers. The same liquids, when loaded into insulating containers, may give rise to liquid-to-metal discharges that are incendive either to vapor or to finely-dispersed oil mist in the vapor space. Using both theoretical and experimental approaches some characteristics of these discharges are evaluated in terms of measurable parameters; empirical ignition test data are employed to help establish safety criteria. When identifying “bad actors” in terms of tendency to static ignition it is recommended that both the liquid vapor pressure and the incidence of high negative charging levels be considered. In the present study, a negatively charged test oil produced energetic positive brush discharges accompanied by surface streamers. Positively charged oil yielded negative brush discharges which did not penetrate to the surface or produce surface streamers. The negative brushes carried an order-of-magnitude lower charge and were shown to be non-incendive during empirical ignition tests. Ignition of paraffin vapor by negative oil discharge occurred for surface potentials above 25 kV. High flash-point oil mists were ignited at surface potentials of about 60 kV, this being limited principally by the representative mist droplet diameter and the mist concentration in the discharge region.