Spark Ignition - Searching for the Optimal Spark Profile

The impact of different spark designs on the ignition and combustion stability is studied using a 13-liter CNG fueled heavy duty spark ignited engine to search for the “optimal” spark design. Experimental results show that robust ignition can be achieved using a significantly shorter spark duration and lower energy than expected. A capacitive discharge ignition (CDI) system enabled to separately control the available spark voltage, current and duration (FlexiSpark®CDI) was compared to a standard CDI system without spark control and an inductive discharge (IDI) ignition system. Typically, a robust ignition can be provided using only 5% of the spark duration and 17% of the spark energy compared to that required by an IDI system to accomplish an equivalent ignition and combustion stability. By applying control of the spark, a robust ignition can be provided which is optimized for the fuel, the engine design, the engine operating condition, and the condition of the spark plugs. This offers a potential to significantly reduce the spark-plug wear and the total cost of ownership without compromising engine performance.The results are especially interesting in the view of Hydrogen fueled SI-ICE, where the required available spark voltage is high, but the required spark energy is low. It is desirable to use a spark design with just enough voltage and power to initiate a sustainable combustion, but with minimal energy not to excessively wear and heat the spark plug electrodes to avoid pre-ignition

A non-destructive transformer oil tester

Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2000.Includes bibliographical references (leaves 62-63).A new non-destructive test of transformer oil dielectric strength is a promising technique to automate and make more reliable a diagnostic that presently involves intensive manual efforts. This thesis focuses some of the issues that must be understood to bring the test from the laboratory to the field. Emphasis is placed on reliability and safety by exploring any effect the test has on the transformer oil, the mechanical parameters necessary to give optimal reliability, and failsafe electronics.by Timothy L. Cargol.M.Eng

High-fidelity Numerical Modelling of Spark Plug Erosion

Spark plug erosion is critical in determining the overall efficiency of a spark ignition engine. Over its lifetime, a spark plug is subject to millions of firings. Each spark event results in material erosion due to several mechanisms such as melting, vaporization, sputtering and oxidation. With electrode wear, the inter-electrode spacing increases and a larger voltage difference is required to initiate the spark. The probability of engine misfires also increases with electrode erosion. Once a critical gap is reached, the energy in the ignition coil is not enough to cause a spark breakdown, and the spark plug must be replaced. Due to the long relevant time scales over which erosion occurs, and the difficulty of analyzing the spark plug environment during operation, determining spark plug lifetime typically requires extensive field testing. A high fidelity commercial thermal plasma solver, VizSpark is used simulate electrode erosion due to spark events. The model preserves key arc physics such as current conservation, conjugate heat transfer, fluid flow and electrode ablation. The solution framework includes the capability of coupling high fidelity arc physics with a dynamically deforming spark-plug electrode. A phenomenological model for electrode erosion based on energy is derived from prior experimental work on single-pulse electrode erosion. The energy based electrode erodion model is validated against experimental results, and 3-D electrode erosion simulations in stationary and cross-flow were performed

Ignition Systems for Gasoline Engines : 4th International Conference, December 6 - 7, 2018, Berlin, Germany

In addition to increasing electrification, forecasts show a worldwide increase in the number of gasoline engines being produced. Rising industrialization will likely lead to 120 million new registrations, at least 75% of them for vehicles based on combustion engines, by the year 2030. Ambitious climate targets will remain a chimera as long as the gasoline engine is not adapted to help significantly reduce carbon emissions. In addition to the requirements of the established markets, we must be prepared for new challenges in emerging economic regions in particular. Engines require greater optimization while remaining sufficiently robust to meet the demands of use all around the world. In addition to the Miller combustion cycle, the industry needs engines that employ strongly charge-diluted combustion to achieve efficiencies significantly above 40%. Instrumental in this will be ignition processes with great potential to shift ignition limits. The question we have to ask ourselves is how can ignition systems help further boost the efficiency of the combustion engine? Together with the participants we discussed this key question during the 4th International Conference on Ignition Systems for Gasoline Engines

Plasma-material interaction and electrode degradation in high voltage ignition discharges

Erosion of material caused by electrical discharges takes place in many technical applications. Particularly, in spark plugs, the durability is mainly determined by the electrode erosion caused by ignition discharges. A better understanding of the wear mechanisms will help in developing new electrode materials with enhanced resistance against spark erosion. In this work, different aspects of the complex interaction between the plasma of the ignition discharge and the electrode are investigated based on experimental observations and simulations. The discharge mode behavior is quantitatively analyzed with regard to the arc and glow phase fractions for different electrode materials and conditions of pressure and gas. The influence of these parameters on the discharge is discussed. This work especially focuses on the formation of microscopic erosion craters on the electrode surface. Their morphology and microstructure are characterized by means of FIB/SEM dual beam techniques. The depth of modifications and the extent of the molten region are determined. To complete these experimental observations, thermal analysis of the crater formation is performed using analytical models and FEM simulations. Characteristic values of time, power density and current involved in the crater formation are estimated. These values are related to the electrical characteristic of the spark, and the effects of the discharge phases on the electrode surface degradation are discussed.Die Erosion von Materialien, die von einer elektrischen Entladung hervorgerufen wird, tritt in zahlreichen technischen Anwendungen auf. Auch die Lebensdauer einer Zündkerze wird durch die von den Zündentladungen verursachte Erosion an Elektrodenmaterialien maßgeblich bestimmt. Ein besseres Verständnis der Verschleißmechanismen ist von großer Bedeutung, um maßgeschneiderte Werkstoffe mit verbessertem Funkenerosionsverhalten zu entwickeln. In dieser Arbeit werden verschiedene Aspekte der komplexen Wechselwirkung zwischen dem Plasma der Zündentladung und der Elektrode anhand von experimentellen Beobachtungen und Simulationen erforscht. Das Entladungsverhalten (Bogen- und Glimmanteil) wird für verschiedene Elektrodenwerkstoffe, Gas-, und Druckbedingungen quantitativ untersucht. Die Morphologie und Mikrostruktur von Erosionskratern werden mit Hilfe von FIB/REM Dual-Beam-Techniken charakterisiert. Die mikrostrukturellen Veränderungen des Materials unterhalb der Oberfläche und insbesondere der Schmelzbadgröße werden bestimmt. Zur Ergänzung der experimentellen Beobachtungen, wird eine thermische Analyse der Kraterbildung mittels analytischen Modellen und FEM-Simulationen durchgeführt. Charakteristische Werte des Kraterbildungsprozesses wie z.B. die Wärmezufuhr, der Strom, und die Wechselwirkungsdauer werden bestimmt und in Bezug auf die verschiedenen Phasen der Zündentladung diskutiert

Prospects of lean ignition with the quarter wave coaxial cavity igniter

New ignition sources are needed to operate the next generation of lean high efficiency internal combustion engines. A significant environmental and economic benefit could be obtained from these lean engines. Toward this goal, the quarter wave coaxial cavity resonator, QWCCR, igniter was examined. A detailed theoretical analysis of the resonator was performed relating geometric and material parameters to performance characteristics, such as resonator quality factor and developed tip electric field. The analysis provided for the construction and evaluation of a resonator for ignition testing.;The evaluation consisted of ignition tests with liquefied-petroleum-gas (LPG) air mixtures of varying composition. The combustion of these mixtures was contained in a closed steel vessel with a precombustion pressure near one atmosphere. The resonator igniter was fired in this vessel with a nominal 150 W microwave pulse of varying duration, to determine ignition energy limits for various mixtures. The mixture compositions were determined by partial pressure measurement and the ideal gas law. Successful ignition was determined through observation of the combustion through a view port. The pulse and reflected microwave power were captured in real time with a high-speed digital storage oscilloscope. Ignition energies and power levels were calculated from these measurements. As a comparison, these ignition experiments were also carried out with a standard non-resistive spark plug, where gap voltage and current were captured for energy calculations.;The results show that easily ignitable mixtures around stoichiometric and slightly rich compositions are ignitable with the QWCCR using the similar kinds of energies as the conventional spark plug in the low milli-Joule range. Energies for very lean mixtures could not be determined reliably for the QWCCR for this prototype test, but could be lower than that for a conventional spark. Given the capability of high power, high energy delivery, and opportunity for optimization, the QWCCR has the potential to deliver more energy per unit time than a conventional spark plug and thus should be considered be as a lean ignition source

Ignitability Study of a Spark-ignited Heavy-duty Engine, fueled with Natural Gas (CNG)

In-order to meet today’s stringent emission regulations of the European Union, the use of low-carbon fuels in ICE, for instance, Natural Gas (CNG)1 is on the limelight. Due to the high knock-resisting properties of methane (high octane rating), the SI (Spark-Ignition) combustion process is the best match with CNG1. A major disadvantage with an SI engine is its low thermal efficiency mainly due to the engine, being throttled. Hence, in-order to increase its efficiency, diluted air (by means of EGR) can be a promising solution.However, with the addition of EGR, combustion stability degrades, hence indicating a potential need for high Ignitability. A robust ignition system can be a solution to achieve high combustion stability by discharging high spark current and duration at the spark-plug gap, therefore, an excessive waste of spark energy in the combustion chamber. As an impact, it will lead to increase in wear in the spark plug electrodes, which is not desirable. Therefore, an experimental research is performed in a heavy-duty SI-ICE fueled with Natural Gas, in-order to study the ignitability requirements of the engine to attain robust combustion, even with high dilution/EGR level.Three different ignition systems are considered in the experiment: a conventional Inductive Discharge Ignition (IDI) system, a Standard Capacitive Discharge Ignition (CDI) system, and an optimized CDI system using FlexiSparkTM Ignition Control Module (ICM), developed by SEM AB. The experiments are performed at different engine operating conditions to review the ignitability requirements with the change in engine load and RPM while adding dilution (by means of EGR). After comparing multiple spark discharge parameters of the ignition systems with respect to engine performances, it is found that the most influential parameter that governs the ignitability capability of an ignition system is “Spark Power”. By effectively varying spark power, the engine can still achieve stable combustion with minimal spark duration. Therefore, a significant amount of spark energy can be saved from being wasted by optimizing the spark discharge parameters, hence keeping the spark plug electrodes wear to a minimum.Finally, a best suitable spark design strategy is proposed for the ignition systems tested at different engine operating conditions while assuring minimal waste of both spark power and energy in the combustion chamber and maintaining a stable engine operation with high EGR/dilution level

Spark Breakdown Voltage Sampling During Early Stage Compression

This thesis proposes a novel methodology to enable cycle by cycle control of a two-stroke cycle type engine. These engines are well known for offering high specific power density solutions, however, this advantage cannot be fully exploited without new technologies enabling significantly reduced emissions and improved fuel economy. If this could be provided, working with direct fuel injection, new highly efficient, low emission, power units could result. One of the main reasons why this has not previously been achieved has been the inability to accurately measure and quantify the amount of combustible charge available for metering of the Air/Fuel ratio. This is due to the highly dynamic gas conditions in the engine which cause significant cyclic variations of scavenging and trapping efficiencies. Existing combustion control methods are unable to accurately compensate for these conditions because fuel quantity is determined using the results of previous combustion events which do not reflect the actual gases available for each combustion. This thesis proposes a different approach, whereby accurate fuel quantities could be determined cyclically from in-cylinder measurements ahead of each combustion event. The intention being, for optimal fuel quantities and ignition initiation timings to be calculated and provided for each cycle. This technology would significantly improve the ability to achieve an optimal combustion of each individual combustion event. The principle of measurement uses and extends proven existing extensive scientific knowledge of the relationships between the value of Spark Break-Down Voltage (SBDV) to gas density and speciation. The methodology presented, applied pulses of voltage to the spark plug, which is normally used only to initiate ignition, to also function as a non-intrusive in-cylinder sensor. Experimental results were obtained using three items of equipment purposely designed and manufactured for the present work. These consisted of a) A new high frequency spark breakdown voltage electronic circuit. b) A static volume sparking chamber. c). A motored test engine into which exhaust gas was supplied from an auxiliary engine via an air mixing system. The novel use of an auxiliary engine enabled a wide range of mass fractions to be subjected to cyclic compression events for evaluation independent of test engine conditions

The development and use of off-shore mineral exploration techniques

Imperial Users onl