Ignition Pulse Research Articles

Fluid–structure coupled simulation of ignition transient in a dual pulse motor using overset grid method

In this paper, the second pulse ignition transient in a dual pulse solid rocket motor with elastomeric barrier pulse separation device has been conducted numerically. An in-house code has been developed to solve governing equations for unsteady compressible flow, heat conduction and structural dynamic. The solid propellant ignition and burning numerical models have been added. The fluid structure interaction is implemented by using the conventional serial staggered algorithm. The large deformation and expansion of the elastomeric barrier are addressed by the dynamic overset grid technology. The accuracy of the numerical method is validated by the experimental cases. Then, the detailed flow field development, pressure evolution, flame propagation characteristics in the combustion chamber, and the structural response of elastomeric barrier are analyzed carefully. The rupture-time and rupture-pressure of the elastomeric barrier are also obtained. The numerical results show that the elastomeric barrier deformation presents a small displacement at the front part and a large displacement at the rear section. The interaction of the compression waves and expansion waves from the convergent portion of the nozzle and from the motor head-end, as well as the supersonic annular jet flow in the combustion chamber, can induce obvious pressure rises with fluctuations and spikes. The first pulse free volume has a significant effect on the time to reach a steady state.

Effects of pulse rise time and repetition frequency on nanosecond pulsed plasma ignition for combustion

Transient plasma ignition (TPI) employs highly non-equilibrium plasmas driven by nanosecond high-voltage pulses for combustion ignition. The effects of rise time and pulse repetition frequency (PRF) on combustion ignition are evaluated when transient plasmas, powered by 10-ns, kilovolt pulses, are employed to initiate combustion of lean, stoichiometric, or rich methane-dry air mixtures at atmospheric pressure. It was found that the plasmas driven by high voltage pulses with a faster rise time and PRF between 6–10 kHz enhanced combustion with higher peak pressure and/or shorter ignition delay. A mode transition in the plasma, corresponding to the combustion initiation, was observed based on voltage and current waveforms of four consecutive pulsed plasmas driven by a pulse burst at kilohertz PRFs. Although benefits in combustion ignition from a shorter rise time and optimal PRF were observed for all three equivalence mixture ratios, the highest peak pressure and shortest ignition delay were associated with the stoichiometric mixtures. In addition, the gas temperature of the transient plasma was measured by determining the rotational temperature of the 2nd positive system of nitrogen to be ∼1000 K for the first pulse and increased up to 2000 K after the application of the 4th pulse in a four-pulse burst TPI.

Pulsed Plasma Ignition Systems with Synchronization of Discharge Processes

Pulsed plasma ignition systems in gas-turbine engines with synchronization of primary and auxiliary discharge processes are considered. In terms of discharge duration, such systems are intermediate between pulsed capacitive systems and plasma ignition systems with a prolonged arc discharge. Experiments show that pulsed plasma systems have better ignition capabilities than capacitive systems with oscillatory discharge, for the same capacitor charge.

Future gasoline engine ignition: A review on advanced concepts

To meet the future requirements of fuel economy and exhaust emissions, high-efficiency gasoline engines tend to employ diluted combustion concepts along with intensified charge motion and stratified mixtures. Securing the ignition of such mixtures over the full engine operation range is challenging, because of the lowered mixture reactivity and increased discrepancy of stoichiometry. In recent years, increasing research efforts have been spending on innovations of ignition technologies to tackle the challenges. In this paper, the directions of ignition improvement are highlighted based on the fundamental understanding of the ignition mechanisms. The working principles of the primary types of advanced ignition systems are introduced; and relevant engine and combustion vessel test results are reviewed. The ignition systems are categorized as: (1) high-energy spark ignition, (2) pulsed nanosecond discharge ignition, (3) radio-frequency plasma ignition, (4) laser-induced plasma ignition, and (5) pre-chamber ignition. The advanced ignition systems are commented, regarding the ignition effectiveness and the implementation challenges, according to the literatures and the extensive empirical work at the authors’ laboratory.

Side-Scan Sonar Image Fusion Based on Sum-Modified Laplacian Energy Filtering and Improved Dual-Channel Impulse Neural Network

The operation mode of a single strip provides incomplete side-scan sonar image in a specific environment and range, resulting in the overlapping area between adjacent strips often with imperfect detection information or inaccurate target contour. In this paper, a sum-modified Laplacian energy filtering (SMLF) and improved dual-channel pulse coupled neural network (IDPCNN) are proposed for image fusion of side-scan sonar in the domain of nonsubsampled contourlet transform (NSCT). Among them, SMLF energy is applied to extract the fusion coefficients of the low frequency sub-band, which combines the characteristics of energy information, human visual contrast, and guided filtering to eliminate the pseudo contour effect of block flow. In addition, the IDPCNN model, which utilizes the average gradient, soft limit function, and novel sum-modified Laplacian (NSML) to adaptively represent the corresponding excitation parameters, is applied to improve the depth and activity of pulse ignition, so as to quickly and accurately select the image coefficients of the high frequency sub-band. The experimental results show that the proposed method displays fine geomorphic information and clear target contour in the overlapping area of adjacent strips. The objective index values are generally optimal, which reflect the information of image edge, clarity, and overall similarity.

АНАЛИЗ ТЕНДЕНЦИЙ РАЗВИТИЯ И ПОСТОБРАБОТКИ АДДИТИВНО ПРОИЗВЕДЁННЫХ ДЕТАЛЕЙ

The subject matter of the study in the article is the analysis of the state, trends and prospects for the development of additive production of metal parts in the aerospace field. The article discusses the need for the application of post-processing processes of additively produced parts; the necessity of parts cleaning after printing is determined, the processes of gas mixture ignition and thermal pulse cleaning as a whole are considered. The goal is to review the application of the additive manufacturing process and the cleaning technology for finished products. In this regard, the following tasks were set: analysis, review and determination of the development trends of additive manufacturing, post-processing of parts and the thermal pulse cleaning process in particular. The following results were obtained. The main areas of practical application of metal parts additive production are analyzed. The technological processes features of post-processing of surfaces and parts as a whole are considered. Based on the above examples, the need for the use of a blank cleaning process is substantiated. In the context of existing cleaning methods, the features of thermal treatment are considered, namely: the essence, advantages and processes accompanying it. Highlighted the current issues of the appointment of technological processing parameters. The following conclusions are formulated. Additive manufacturing is a fast-growing and promising method for the production of parts in the aerospace industry in view of its manufacturability and economy. Thus obtained parts, usually, do not require additional processing, however, it is not always possible to completely get rid of its need at this stage of technology development. One of the most important performance characteristics of parts is the quality of their outer and inner surfaces. In this regard, the use of thermopulse processing is economically determined. To use all the potential capabilities of this cleaning method, it is necessary to study it more deeply in order to determine the influence of processing modes on its result.

Study on the influence of change in axial position of cathode on the ignition process of a Hall thruster

A hollow cathode is an important component of the discharge circuit in Hall thruster. Different axial positions of the hollow cathode will cause the electrons emitted by the cathode to enter the discharge channel differently, thereby affecting the energy acquisition of the electrons and influencing the ignition of Hall thruster. Thus, a high-speed camera with a charge-coupled device was used to examine the plume features over time when the cathode was located at different axial positions. To better understand the changes in the plasma parameters in the discharge channel and plume during ignition, a two-dimensional axisymmetric fully kinetic particle-in-cell/Monte Carlo collision model was used to calculate the ion density and potential distribution at different times during the ignition process of Hall thruster. The results indicate that the ion density generated in the initial stage of ignition is larger at the exit of the discharge channel when the cathode axial position is close to the exit of the discharge channel. The electron avalanche ionization occurs earlier, and the peak value of the ignition pulse current is larger. These differences may occur because the energies of the electrons (emitted by the cathode) entering the discharge channel from different cathode axial positions differ.

Enhancement of discharge and deposition rate in dual-pulse pulsed magnetron sputtering: Effect of ignition pulse width

To increase deposition rate during pulsed magnetron sputtering (PMS), a novel dual-pulse pulsed magnetron sputtering (DP-PMS) was proposed. The discharge mode of DP-PMS firstly produced a pulsed high ignition voltage with short duration followed by a subsequent pulsed low work voltage with long duration. CrN coatings were deposited by DP-PMS and PMS. The effect of ignition pulse width of DP-PMS on the discharge of Cr target in argon and the deposition rate of CrN coatings was explored. The target current of DP-PMS was featured by an initial peak, which was different from the triangular waveform in PMS. The DP-PMS with a longer ignition pulse produced a higher substrate current and a larger number of Cr0 at unit target power. There existed a proper width of initial ignition pulse (e.g. 15 us) producing the maximum deposition rate at unit target power, which was nearly four times higher than that of PMS.

Effect of Main Cut and Multiple Trim Cuts on Surface Integrity of 2379 Steel

Wire electrical discharge machine (WEDM) is commonly used in producing tool and die parts. However, it rarely achieves the optimum machining condition due to the inappropriate selection of WEDM machining parameters. In this study, 2379 steel which own properties equivalent to SKD 11 was used as die material. Four main wire electrical discharge machine (WEDM) cutting parameters, namely pulse on time, pulse off time, servo voltage, ignition pulse current has been experimentally studied and optimized at both levels, main cut and multiple trim cuts using Taguchi Method. Based on Taguchi Method optimization and analysis of variance (ANOVA), the result found that pulse on time and pulse off time give significant effect on white layer thickness for both main cut and multiple trim cuts. According to Signal to Noise (S/N) ratio response, the optimal combination of A2B3C2D1 and A1B3C3D1 gave the lowest white layer thickness for main cut and multiple trim cuts respectively. It also has been found that the hardness of machined surface with multiple trim cuts is higher compared to main cut.

The feasibility study of ion driven shock ignition of reactor-size targets in inertial confinement fusion

In this paper, we are intending to investigate the shock ignition approach to inertial confinement fusion (ICF) by using an ion beam driver to examine energy gain performance in reactor-size targets filled by cryogenic deuterium-tritium hydrogen isotopes. Here, pressure dynamics across the fuel layer affected by ignition beam parameters have been analyzed by using the DEIRA-4 simulation code, for the two targets that we chose for the case study. By choosing the proper pulse shaping and evaluation of finding the appropriate time and position of the inter-collision time between two compression and ignition pulses, it has been found that shock ignition can create the pressure more than 104 Gbar at the fuel center and therefore increase gain by 18% and 25% for Case 1 and Case 2, respectively. Ionic shock ignition can also decrease the ignition threshold; hence, it causes 19% reduction for Case 1 and 39% reduction for Case 2 of the internal beam energy. It has been shown that besides the lower implosion velocities relative to traditional central ignition, which are now maintained, the fuel pressure at stagnation becomes much higher than it is. In addition, the stable stagnation stage, ignition condition, and high-energy gain are achieved when the optimum configuration of the ignition beam has been derived. Our results show that we can attain pressures level of 200 Gbar < P < 500 Gbar and implosion velocities of 170 km s−1 < Uimp < 291 km s−1 which are in agreement with laser-driven shock ignition alternatives. The pressure range is more than the Standard ICF, laser-driven shock ignition, and impact fast ignition (IFI), and the implosion velocity range is less than Standard ICF and IFI.

Experimental Study of Multipoint Ignition in Methane–Air Mixtures by Pulsed Microwave Power

Microwave plasma offers a promising method to achieve faster combustion in internal combustion engine. In this paper, microwave multipoint ignition was confirmed via the high-speed imaging technique. The experiment was conducted with microwave resonant ignition system and optical system. A 2-ms, 3000-W, 2.45-GHz pulsed microwave power was used as energy source to produce initial flame kernel in combustion chamber. High-speed imaging was used to record the ignition characteristics via high-speed camera. Ignition experiments were conducted at high pressure of 2 bars of stoichiometric methane–air mixtures. It can be observed in the image and the pressure curves that multiple flame kernels are generated simultaneously. Faster combustion speed is achieved by pulsed microwave power ignition than traditional spark plug ignition in constant volume chamber.

Pulsed Ignition Devices with New Circuit Solutions

The most of threelead domestic pulse ignition devices (PID) do not provide parameters of highvoltage pulses determined by the lamp operation manuals. New circuit solutions are presented, which meet the requirements to HP sodium lamps used in street illumination and greenhouse irradiation. It is proposed to separate two functions of the threelead PID pulse transformers: generation of highvoltage pulses and transmission of the lamp full current. To generate highvoltage pulses, transformers with a big turn number of thin wire should be used. And to transmit lamp full current, highfrequency throttles with a low resistance should be applied. A version of calculating parameters of a high­frequency throttle and oscillograms of pulses generated by the PID are given.

Design of Monitoring and Control System for Multi-Tube Ignition Pulse Detonation Engine

A multi-processers monitoring and control system, which use the Lora as wireless communication technology, was designed to meet needs of mobility, safety, fast frequency adjustment, portability, none affect on PDE thrust test and so on. This paper elaborated on scheme of whole system, local high-speed signal acquisition, storage, data export and ignition control method. Experimental results show that the monitoring and control system was able to implement timely and accurately control and data acquisition of detonation tubes, dynamical parameters changing, remote control and eliminate the damage for human beings caused by PDE, with mobile and portable, high integration, convenient operation, reliable performance characteristics.

A feasibility study on wire electrical discharge machining of carbon fibre reinforced plastic composites

This paper details preliminary experimental work to investigate the wire electrical discharge machining (WEDM) of unidirectional carbon fibre reinforced plastic (CFRP) composites using a high tensile strength zinc rich coated brass wire (0.25 mm diameter). A fractional factorial L18 Taguchi experimental design was employed to evaluate the influence of varying open gap voltage (120 and 140 V), ignition current (3 – 5 A) as well as pulse on-time (0.8 – 1 µs) and off-time (4 – 8 µs) on material removal rate (MRR), top (Wt) and bottom (Wb) kerf widths as well as workpiece edge damage. The ignition current and pulse off-time were found to be statistically significant factors affecting MRR based on an analysis of variance, with percentage contribution ratios (PCR) of 48.5% and 24.3% respectively. It was observed that MRR, which ranged between 0.43 and 2.41 mm3/min, increased with both ignition current and pulse on-time due to the higher discharge energy generated in the machining gap. No signs of workpiece damage in terms of delamination or surface burning was apparent, despite the higher MRR. Conversely, the larger open gap voltage surprisingly led to reductions in MRR, which was likely due to unstable gap conditions caused by greater levels of residual melted resin within the gap or re-deposition on the workpiece surface. In terms of kerf width, ignition current was revealed as the sole significant factor with respect to the top surface (up to ~ 0.28 mm) having a PCR of 56.6%, while none of the variable parameters had a major effect on the bottom kerf width.

Controlled Fusion Strategy Using Ultra-Intense Laser Derived Positron Generation for Initiation

A controllable strategy for eliciting nuclear fusion is presented through ultra-intenselaser derived positron generation by a conceptual first physics perspective. The capability to generate positrons on demand in a controlled manner through an ultra-intense laser incident on a high atomic number target, such as gold, is the intrinsic core to the foundation of controllable nuclear fusion. Positron antimatter generated from the periphery of the fusion fuel pellet provides the basis for initiating the fusion reaction, which is regulated by controlling the operation of the ultra-intense laser. A dual pulsed Fast Ignition mechanism is selected to achieve the fusion reaction. Based on first physics performance analysis the controllable strategy for eliciting nuclear fusion through ultra-intenselaser derived positron generation offers a realizable means for achieving regulated nuclear fusion. A future perspective of the controllable fusion strategy addresses the opportunities and concerns of a pathway toward regulated nuclear fusion.

Structure and Properties of Parts with Coatings After Heat Treatment

Microstructures of combined coatings deposited under radiation heating in vacuum with pulsed ignition of glow discharge are presented. The effect of the heat treatment on the structure and properties of the coatings is studied.

Research on measurement of aviation magneto ignition strength and balance

Aviation magneto ignition system failure accounted for two-thirds of the total fault aviation piston engine and above. At present the method used for this failure diagnosis is often depended on the visual inspections in the civil aviation maintenance field. Due to human factors, the visual inspections cannot provide ignition intensity value and ignition equilibrium deviation value among the different spark plugs in the different cylinder of aviation piston engine. So air magneto ignition strength and balance testing has become an aviation piston engine maintenance technical problem needed to resolve. In this paper, the ultraviolet sensor with detection wavelength of 185~260nm and driving voltage of 320V DC is used as the core of ultraviolet detection to detect the ignition intensity of Aviation magneto ignition system and the balance deviation of the ignition intensity of each cylinder. The experimental results show that the rotational speed within the range 0 to 3500 RPM test error less than 0.34%, ignition strength analysis and calculation error is less than 0.13%, and measured the visual inspection is hard to distinguish between high voltage wire leakage failure of deviation value of 200 pulse ignition strength balance/Sec. The method to detect aviation piston engine maintenance of magneto ignition system fault has a certain reference value.

Virtual engine management simulator for educational purposes

This simulator was conceived as a software program capable of generating complex control signals, identical to those in the electronic management systems of modern spark ignition or diesel engines. Speed in rpm and engine load percentage defined by throttle opening angle represent the input variables in the simulation program and are graphically entered by two-meter instruments from the simulator central block diagram. The output signals are divided into four categories: synchronization and position of each cylinder, spark pulses for spark ignition engines, injection pulses and, signals for generating the knock window for each cylinder in the case of a spark ignition engine. The simulation program runs in real-time so each signal evolution reflects the real behavior on a physically thermal engine. In this way, the generated signals (ignition or injection pulses) can be used with additionally drivers to control an engine on the test bench.

Laser ignition of an experimental combustion chamber with a multi-injector configuration at low pressure conditions

In search of reliable and light-weight ignition systems for re-ignitable upper stage engines, a laser ignition system was adapted and tested on an experimental combustion chamber for propellant injection into low combustion chamber pressures at 50–80 mbar. The injector head pattern consisted of five coaxial injector elements. Both, laser-ablation-driven ignition and laser-plasma-driven ignition were tested for the propellant combination liquid oxygen and gaseous hydrogen. The 122 test runs demonstrated the reliability of the ignition system for different ignition configurations and negligible degradation due to testing. For the laser-plasma-driven scheme, minimum laser pulse energies needed for 100% ignition probability were found to decrease when increasing the distance of the ignition location from the injector faceplate with a minimum of 2.6 mJ. For laser-ablation-driven ignition, the minimum pulse energy was found to be independent of the ablation material tested and was about 1.7 mJ. The ignition process was characterized using both high-speed Schlieren and OH* emission diagnostics. Based on these findings and on the increased fiber-based pulse transport capabilities recently published, new ignition system configurations for space propulsion systems relying on fiber-based pulse delivery are formulated. If the laser ignition system delivers enough pulse energy, the laser-plasma-driven configuration represents the more versatile configuration. If the laser ignition pulse power is limited, the application of laser-ablation-driven ignition is an option to realize ignition, but implies restrictions concerning the location of ignition.

The Role of Hydrodynamic Enhancement on Ignition of Lean Methane-Air Mixtures by Pulsed Nanosecond Discharges for Automotive Engine Applications

ABSTRACTThe downsizing and boosting of automotive engines for increased fuel economy poses challenges in both obtaining stable ignition at boosted intake pressures and high dilution conditions. Pulsed nanosecond discharge ignition technologies have shown promise in more reliably igniting dilute charge mixtures in internal combustion engine experiments. However, reasons for this combustion enhancement remain unclear. In this study, we ignited lean methane-air mixtures in a constant volume chamber at 2 bar absolute pressure to evaluate pulsed discharge ignition using a novel electrode geometry. The in-chamber pressure history indicates faster flame development times than those produced by traditional inductive spark. High-speed schlieren imaging reveals a significant hydrodynamic component to the observed enhancement: a more wrinkled flame kernel structure and increased burning rates from increased flame surface area. Increasing the number of pulses increased expulsion of the flame kernel. Our results clarify the enhancement observed by other researchers in internal combustion engine experiments.