Conventional Spark Plug Research Articles

Study of an innovative three-pole igniter to improve efficiency and stability of gasoline combustion under charge dilution conditions

A diluted cylinder charge helps in engine fuel efficiency but at the same time presents significant challenges to combustion stability. An innovative three-pole spark igniter is researched to explore multi-spot ignition technology and improve the burning process of high-efficiency combustion under diluted conditions. The unique design features three independent pairs of electrodes in a single spark plug and allows new approaches to apply novel ignition strategies. Optical combustion vessels and high-speed imaging techniques are employed to develop fundamental understandings of the multi-spot ignition process. A large number of tests are performed on instrumented combustion vessels to statistically quantify and demonstrate the effect of the three-pole igniter, in comparison with a conventional spark plug. Finally, the prototype three-pole igniter is implemented on a production engine to validate and demonstrate the improvements in engine combustion under low and high dilution conditions. As shown by test results, the three-pole igniter offers shorter ignition delay and faster burning, thereby improving combustion phasing and fuel economy. The three-pole igniter exhibits greater advantages for combustion stability under high dilution conditions that reduce pumping loss and thus gains fuel economy.

A New Spark Plug to Improve the Performances of Combustion Engines: Study and Analysis of Unburned Exhaust Gases

The ignition sparks provided by the conventional spark plug do not always ensure a fast and complete combustion of the hydrocarbon-air mixture. For this reason, we offer a new type of plug with a double spark using two simultaneous discharges generated by a pulsed high voltage-power supply. This work presents the comparison of two spark plugs, a classical one and a double spark plug, by analyzing the unburned hydrocarbon gases from the exhaust pipe of the engine. For a first gasoline engine, we measure the oxygen concentration in the exhaust gases with a lambda probe and the unburned hydrocarbon by the use of GC–MS coupled with SPME extraction technique. We can observe a clear decrease of total unburned hydrocarbon (THC). For a second motor test bench, powered with propane, we complete measures in function of air/fuel ratio of the THC, NOx, CO2 and CO. These results confirm that we obtained a better combustion especially for leaner mixtures.

Turbulent flame propagation enhancement by application of dielectric barrier discharge to fuel-air mixtures

The promotional effect of non-thermal plasma (NTP) on lean flame propagation in turbulent fuel-air mixtures in a reciprocating engine-like high-temperature and -pressure environment was investigated. A turbulent flow was created by installing a perforated plate with oblique holes in the combustion chamber of a rapid compression and expansion machine (RCEM). Ignition was conducted by conventional spark plug. The NTP was generated by a dielectric-barrier discharge (DBD) device installed in the combustion chamber near the spark plug. A portion of the lean fuel-air mixture (ϕ = 0.5) in the chamber passed through the NTP and diffused throughout the chamber before spark ignition. To elucidate whether the effect persisted even when the plasma-affected volume was diffused by the flow, two types of experiments with temporal delay were conducted. The fuels evaluated were n-heptane as a representative fuel with a strong low-temperature oxidation reaction, i-octane as a representative fuel with a weak low-temperature reaction, and a primary reference fuel consisting of a mixture of these two fuels. Temporal growth of the flame was observed using a high-speed camera with an image intensifier. The evolution of in-cylinder pressure was also monitored and the characteristic time of the mass fraction burned was evaluated accordingly. It was found that flame propagation was promoted by DBD for n-heptane-containing mixtures at a certain initial temperature while the i-octane-air mixture did not exhibit such enhancement. The results obtained suggest that long-lived intermediate chemical species formed by the plasma diffuse into the cylinder, affecting flame propagation through promotion of a low-temperature oxidation reaction. In addition to these findings, the effect of NTP on burning periods were evaluated.

A Comparative Study of Cycle Variability of Laser Plug Ignition vs Classical Spark Plug Ignition in Combustion Engines

Over the past 30 years numerous studies and laboratory experiments have researched the use of laser energy to ignite gas and fuel-air mixtures. The actual implementation of this laser application has still to be fully achieved in a commercial automotive application. Laser Plug Ignition as a replacement for Spark Plug Ignition in the internal combustion engines of automotive vehicles, offers several potential benefits such as extending lean burn capability, reducing the cyclic variability between combustion cycles and decreasing the total amount of ignition costs, and implicitly weight and energy requirements. The paper presents preliminary results of cycle variability study carried on a SI Engine equipped with laser Plug Ignition system. Versus classic ignition system, the use of the laser Plug Ignition system assures the reduction of the combustion process variability, reflected in the lower values of the coefficient of variability evaluated for indicated mean effective pressure, maximum pressure, maximum pressure angle and maximum pressure rise rate. The laser plug ignition system was mounted on an experimental spark ignition engine and tested at the regime of 90% load and 2800 rev/min, at dosage of λ=1.1. Compared to conventional spark plug, laser ignition assures the efficiency at lean dosage.

Application of a novel microwave-assisted plasma ignition system in a direct injection gasoline engine

An experimental study was carried out to investigate the effect of microwave-assisted plasma ignition on the combustion and emission characteristics in a 500cm3 single cylinder direct injection gasoline engine. The microwave-assisted plasma ignition system consisted of a 2.45GHz magnetron (3kW), a waveguide, a mixer and a non-resistor spark plug. The first experiments were performed in a 1400cm3 constant volume combustion chamber (CVCC) to clarify the mechanism of combustion enhancement by microwave ejection. The combustion tests were performed using an acetylene-air mixture at a range of relative air/fuel ratios (λ) under initial ambient pressures of 0.3MPa and 0.5MPa. The microwave-assisted plasma ignition has more advanced combustion phase than the conventional spark ignition showing larger initial flame kernel size and faster flame speed. The imaging results of the hydroxyl (OH) radical in ignition and flame demonstrated the potential of a faster chemical reaction by applying microwave on combustion. The microwave-assisted plasma ignition had a higher spark intensity and larger covering area than the conventional spark plug. The distribution and intensity of OH radicals on the surface of the flame were also higher with microwave ejection. In terms of engine test, lean limit was extended up to lambda 1.55 and the fuel efficiency was improved by 6% by microwave-assisted plasma ignition. The combustion phase was advanced so the peak of in-cylinder pressure and heat release rate increased more than those of conventional spark ignition. Based on the faster combustion, the combustion stability was enhanced so the lean limit was extended to lambda of 1.57. The microwave-assisted plasma ignition system was advantageous in the reduction of carbon monoxide and unburned hydrocarbon emissions, whereas nitrogen oxide emissions increased due to the higher temperatures in the combustion chamber. The engine test results finally demonstrated that the certain level of microwave ejection energy could improve all of engine performance and emission characteristics than conventional spark ignition system.

Aspects of experimental investigations of laser plug ignition use at spark ignition engine

Nowadays, the necessity of pollutant emissions reduction brings to the fore new technologies developed for a better control of the combustion process. Ignition is the process of starting radical reactions until a selfsustaining flame has developed and strongly affects the formation of pollutants. Among the new technologies used for ignition and combustion control, the Laser Plug Ignition system is defined as an innovative technology which overcomes several limitations of conventional spark ignition. Laser ignition technology presents many advantages for engine operating control, engine performance improvement and pollutant emissions reduction. The objective of the paper is the experimental research of the laser ignition used in the spark ignition engine. The laser plug ignition system was mounted on an experimental spark ignition engine and tested at the regime of 90% load and 2800 rpm and dosage, λ = 1. The experimental results present the influence of laser ignition on different engine parameters compared to electric spark ignition. The influence on in-cylinder pressure, heat release rate, engine efficiency and pollutant emissions level is analyzed. Compared to a conventional spark plug, a laser ignition system assures efficient engine operation at lean dosages.

Pulse train ignition with passively Q-switched laser spark plugs

Leaner burning and downsizing are two concepts pursued by engine developers to reduce fuel consumption and emissions. Both approaches lead to increasing challenges concerning ignition, as these concepts are typically associated with an increase in flow velocity and degree of turbulence as well as raised pressure at the moment of ignition. In this context, the use of miniaturized passively Q-switched laser spark plugs with pulse train ignition is considered as a promising alternative to conventional spark plugs. However, the application of these passively Q-switched laser spark plugs inevitably leads to the question of optimum pulse train parameters. For a better understanding, this study deals with improved flame formation by passively Q-switched laser pulse train ignition under engine-like conditions. The entire ignition process is investigated with a special focus on interactions of consecutive pulses. Therefore, three methods are combined: energy transfer measurements from laser pulse to plasma with high temporal and spatial resolution show the breakdown process depending on different pressures and fluid mixtures. The temperature decrease in the induced plasma is analyzed with measurement strategies for temporal high-resolved plasma spectroscopy especially adapted to passively Q-switched lasers. In combination with high-speed schlieren measurements, the changing local ignition conditions during pulse train ignition are demonstrated. The experiments show how consecutive pulses interact and contribute to the ignition in case of a gas flow. The used prototypes of laser spark plugs are provided by Robert Bosch GmbH.

内燃機関の熱効率向上に向けた先進着火技術

Natural gas engines have been attracting a lot of attention recently due to the development of unconventional natural gas sources. Achieving lean burn with supercharging is necessary to attain high thermal efficiency. Conventional spark plugs face difficulties with ignition because of the high pressure and lean air/fuel mixture. This paper describes studies on laser spark ignition which has been investigated at AIST as an alternative method for the achievement of stable ignition under such conditions. The extension of lean limit and improvement in thermal efficiency are demonstrated, and the possibilities of advanced laser ignition are also discussed.

Review of Laser Ignition for Methane-Air Mixtures

Reducing vehicle pollutant emissions and fuel consumption is becoming more and more important challenges, while lean-burning are a promising development. However, lean-burning may leads to other problems including combustion instability and incomplete combustion. Recently, laser ignition system has become an attractive field of research in order to replace the conventional spark plug ignition systems in the internal combustion engines to solve problem above. Moreover, methane was regarded as very promising fuel. Therefore, the objective of this article is to review the ignition and combustion characteristics of methane-air mixtures by laser-induced ignition.

Radio frequency spark plug: An ignition system for modern internal combustion engines

Plasma sustained ignition systems are promising alternatives to conventional spark plugs for those applications where the conditions inside the combustion chamber are more severe for spark plug operation, like internal combustion engines with high compression ratio values or intake charge dilution.This paper shows the results of an experimental activity performed on a spark ignition internal combustion engine equipped with a Radio Frequency sustained Plasma Ignition System (RFSI). Results showed that the RFSI improved engine efficiency, extended the lean limit of combustion and reduced the cycle-by-cycle variability, compared with the conventional spark plug for all test conditions. The adoption of the RFSI also had a positive impact on carbon monoxide and unburned hydrocarbon emissions, whereas nitrogen oxide emissions increased due to higher temperatures in the combustion chamber. Therefore, RFSI represents an innovative ignition device for modern internal combustion engines and overcomes the compatibility problems of other non-conventional ignition systems.

Experimental study of fine center electrode spark plug in bi-fuel engines

In the present work, the erosion of platinum fine center electrode spark plugs and conventional nickel plugs are investigated in a gasoline and natural gas bi-fuel engine. The effect of electrode erosion is evaluated by comparing the required ignition voltage and cold start ability of the different plug designs. After durability tests, platinum fine center electrode plug had insignificant electrode erosion and negligible gap growth; whereas the nickel plug had notable erosion and gap growth. There was no detectable side sparking for fine center electrode plugs. In terms of performance, the required ignition voltage of fine center electrode plug was lower than conventional spark plug. Also, results of a cold start test demonstrated that the starting time of the engine with fine electrode plugs was lower than conventional spark plugs. The surface of electrodes was studied by the scanning electron microscope and the energy dispersive X-ray spectroscopy techniques. Cracking and peeling was observed on the surface of the nickel conventional electrodes, but not on the surface of the platinum fine electrodes. These tests show that platinum fine center electrodes could be suitable for gasoline/natural gas bi-fuel engines to meet long lifetime demand.

Comparative experimental evaluation of performance, combustion and emissions of laser ignition with conventional spark plug in a compressed natural gas fuelled single cylinder engine

Laser is emerging as a strong concept for alternative ignition in spark ignition engine. Laser ignition has potential advantages over conventional spark plug ignition. Laser ignition system is free from spark electrodes hence there is no loss of spark energy to the electrodes, which are also free from erosion effect. In addition, there is flexibility in choosing spark location and it offers excellent performance under high in-cylinder pressures. In this paper, performances of laser ignition and conventional spark ignition systems are comparatively evaluated in terms of in-cylinder pressure variation, combustion stability, fuel consumption, power output and exhaust emissions at similar operating conditions of the engine.

Investigation of Performance and Emission Characteristics of a Heavy Duty Natural Gas Engine Operated with Pre-Chamber Spark Plug and Dilution with Excess Air and EGR

This article deals with application of turbulent jet ignition technique to heavy duty multi-cylinder natural gas engine for mobile application. Pre-chamber spark plugs are identified as a promising means of achieving turbulent jet ignition as they require minimal engine modification with respect to component packaging in cylinder head and the ignition system. Detailed experiments were performed with a 6 cylinder 9.4 liter turbo-charged engine equipped with multi-point gas injection system to compare performance and emissions characteristics of operation with pre-chamber and conventional spark plug. The results indicate that ignition capability is significantly enhanced as flame development angle and combustion duration are reduced by upto 30 % compared to those with conventional spark plugs at certain operating points. Maximum possible dilution (limited by combustion stability index, Coefficient of Variation (COV) of Gross Indicated Mean Effective Pressure (IMEPg)) with excess air and EGR were investigated experimentally at engine speed of 1500 rpm and 5, 12 and 18 bar IMEPg operating load and results indicate that the lean limit is extended by 0.8-1 Lambda unit and 5-8% EGR rate units. It was also observed that pre-chamber spark plugs cause charge pre-ignition at loads exceeding 10-12 bar IMEPg. To avoid this, the minimum amount of dilution, with excess air and then EGR, which is required to operate above 10 bar IMEPg was estimated experimentally. Finally, to compare performance and emission characteristics of operation with these two ignition techniques, the engine was tested on an ESC-like (European Stationary Cycle) 12 mode cycle. Results indicated marginal reduction in cycle averaged NOx emissions with maximum excess air dilution and about 50% reduction with maximum EGR dilution, whereas CO and HC emissions increased. Other operating characteristics like the flame development angle, combustion duration, brake efficiency etc. are also compared for the tested operating range of the test engine. (Less)

Advancing lean combustion of hydrogen–air mixtures by laser-induced spark ignition

We investigate how ignition through laser-induced plasma can improve the application of lean combustion, in particular in environmental conditions relevant to hydrogen internal combustion engines (ICE). Major design goals when developing combustion engines are increasing thermal efficiency and decreasing combustion emissions. High compression ratios, lean combustion and precise ignition timings are contributing factors in ICE optimization. In our studies, several gains from laser spark ignition are investigated. The high energy content of laser-induced ignition kernels are shown to speed up the development of the early flame kernels. These extended ignition kernels transfer into self propagating flames even in lean mixtures. Leaner mixtures are ignited in our experiments using laser spark ignition in comparison to conventional electrical spark plugs. Precise ignition timing is realized. Multi-point ignitions are synchronized on the timescale of microseconds to enhance the progress of combustion. We modified the locus of ignition in a mixture flow to decrease the temporal extent of flame contact with the wall. Therefore, burning duration and heat loss can be reduced.

220203 エタノール噴霧の既燃ガスジェット着火現象(OS12 燃焼工学の新展開,オーガナイズド・セッション)

In this study, we experimentally investigated the effects of burnt gas jet ignition on ethanol spray combustion using a constant volume combustion vessel with a sub chamber. The ignition and combustion phenomena were observed by using a high-speed video camera, and combustion pressure history was measured as well. In case of burnt gas jet ignition, compared with a conventional spark plug ignition, stronger luminous flames were observed, and rate of pressure rise and maximum overpressure much increased. Moreover, it was confirmed that measured HCHO concentration of the burnt gas in the combustion vessel remained at low level although the amount of ethanol related to combustion reaction increased. It is mainly due to the strong turbulent mixing effects of the hot burnt gas jet and the spray flows.

Laser-induced optical breakdown applied for laser spark ignition

AbstractIn the present article, the experimental investigation of optical breakdown induced by ns/mJ pulses at two wavelengths, 1064 nm and 532 nm, in air of atmospheric pressure is reported and discussed. The obtained breakdown thresholds were compared with theory and are in good agreement. The generated plasmas have been characterized by their amount of scattered laser light, energy transmission, and change of the transmitted temporal shape. Laser-induced plasma formation in a gas, in air, also generates an acoustic pressure wave. The acoustic energy is compared to the laser pulse energy and is found to be linearly dependent. Moreover, the frequency distribution of the characteristic acoustic pressure wave was analyzed. The experiments described were accomplished in order to optimize a laser ignition system with regard to efficiency and costs. The laser system employed for these investigations is a compact high peak power, passively Q-switched, longitudinally diode-pumped solid-state laser. Such a “laser spark plug” should replace conventional spark plugs in internal combustion engines because conventional ignition has reached its limits in terms of efficiency and durability. Thereby, a reduction of pollutant emission should also be feasible.

High Peak Power, Passively $Q$-switched Microlaser for Ignition of Engines

The compact (electric spark plug size), diode-pumped, passively Q-switched Nd:YAG/Cr4+:YAG microlaser was developed for ignition of engines. Output energy of 2.7 mJ per pulse and 11.7 mJ per four-pulse train with a pulsewidth of 600 ps and an M 2 value of 1.2 were obtained at a pump duration of 500 ?s. The optical-to-optical conversion efficiency was 19%. Brightness of the microlaser was calculated as 0.3 PW/ sr-cm2 and optical power intensity was calculated as 5 TW/cm2 at the focal point of ignition. The enhanced combustion by the microlaser ignition was successfully demonstrated in a constant-volume chamber at room temperature and atmospheric pressure. The cross section area of a flame kernel generated by laser ignition is 3 times larger than that by a conventional spark plug at 6 ms after ignition in a stoichiometric mixture (A/F 15.2) of C 3H 8/air, even though ignition energy of the laser is 1/3 of that of the spark plug. Hundred percent ignition was successfully demonstrated in a lean mixture of A/F 17.2 by laser ignition, where electric spark plug ignition failed.

Electromagnetic design of a novel microwave internal combustion engine ignition source, 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. Towards this goal, the quarter wave coaxial cavity resonator (QWCCR), igniter was examined. A brief overview of the QWCCR's history is presented, followed by an electromagnetic analysis of the resonator. Microwave and radio-frequency gas breakdown at atmospheric and higher conditions are reviewed briefly. The presented analysis focuses on geometric and material parameter relations compared with performance characteristics, such as resonator quality factor and developed tip electric field which initiates a single-electrode high-pressure microwave gas breakdown. Conductor surface losses, dielectric losses, and radiation losses of the device are considered in the analysis, for which parameters of a prototype QWCCR were chosen for construction and evaluation of a resonator. Improved designs allowed successful integration of a QWCCR into a Briggs and Stratton engine. Given the capability of precise control, high power, and high energy delivery, and the opportunity for further optimization, the QWCCR has the potential to deliver more energy per ignition than a conventional spark plug and thus should be considered for application as a lean ignition source.

Experimental Study on Laser-Induced Ignition of Swirl-Stabilized Kerosene Flames

Conventional ignition systems of aeroengines are an integral part of the combustion chamber’s structure. Due to this hardware-related constraint, the ignition spark has to be generated in the quench zone of the combustion chamber, which is far from the optimum regarding thermo- and aerodynamics. An improved ignitability of the fuel-air mixture can be found in the central zone of the combustor, where higher local equivalence ratios prevail and where mixing is favorable for a smooth ignition. It would be a major advancement in aeroengine design to position the ignition kernel in these zones. A laser system is able to ignite the fuel-air mixture at almost any location inside of the combustion chamber. Commercial laser systems are under development, which can replace conventional spark plugs in internal combustion engines and gas turbines. This study was conducted to evaluate the applicability of laser ignition in liquid-fueled aeroengines. Ignition tests were performed with premixed natural gas and kerosene to evaluate the different approaches of laser and spark plug ignition. The experiments were carried out on a generic test rig with a well-investigated swirler, allowing sufficient operational flexibility for parametric testing. The possibility of the free choice of the laser’s focal point is the main advantage of laser-induced ignition. Placing the ignition kernel at the spray cone’s shear layer or at favorable locations in the recirculation zone could significantly increase the ignitability of the system. Consequently, the laser ignition of atomized kerosene was successfully tested down to a global equivalence ratio of 0.23. Furthermore, the laser outperformed the spark plug at ignition locations below axial distances of 50 mm from the spray nozzle.

Further Development of a Smoke Sensor for Diesel Engines

This paper describes experimental research aimed at developing an on-board smoke sensor for diesel engines. The sensor element was similar to a conventional spark plug. Electrical heating of the insulator was used to prevent carbon fouling from the diesel soot. The sensing element created sparks within the exhaust pipe and changes in smoke levels were detected through analysis of the voltage levels of the sparks. The system was tested in a heavy duty diesel engine equipped with exhaust gas recirculation (EGR) and compared with reference measurements of the filter smoke number (FSN). The experiments showed good sensitivity to step changes in smoke levels (accomplished by varying EGR levels) at smoke levels below 0.5 FSN. However, the sensor suffered from temperature induced signal drift and was unstable under some circumstances. The use of a spark plug with a smaller electrode tip diameter improved the signal stability. It is proposed that measurement and control of the electrode temperature will be necessary to control the signal drift.