Analysis of Spark Plug Gap on Flame Development using Schlieren Technique and Image Processing

The development of the automotive world experienced rapid development, and the most prominent development was in the ignition system. In this study will be discussed about the gasoline motor ignition system, especially the effect of spark plug gap on the power produced by the gasoline engine. The aim of research is to produce a good combustion process in the engine combustion chamber by determining the distance of the spark plug so that the sparks produced are perfect. The right spark plug gap will produce perfect combustion and the power produced will also be in accordance with the specifications of the engine. In order to maintain good spark plug work, it needs to be done in a maintenance manner to determine the extent of the effect of spark plug gap on the engine power of the gasoline motor. As for what will be examined in this study is the engine speed and engine power which is influenced by the distance of the spark plug to produce engine power on the gasoline motor. The method used in this study in the research is by using the direct method of conducting research in Cv. Prosperous motorbike. Materials used in research, one unit of Toyota Innova, with equipment measuring instruments and keys needed. In the study measurements were taken by measuring the distance of spark plug gap from 0.8 mm to the normal power, 0.6 mm the effect on power is not good because at high speed the fire jump is not large so the combustion is not perfect, and 1 mm the effect on the power The result is very low because the low and high speed sparks are unable to burn the fuel mixture. The results show differences in engine speed and power produced by the engine on a gasoline motor. To produce perfect engine power, it is necessary to do routine maintenance, especially the ignition system for spark plugs so that ignition and engine power are produced as stable as the specifications.

A visualization study using the schlieren method is adopted in an optically-accessible, cylindrical constant volume combustion chamber to identify the mechanism of ignition energy and ignition system interaction in spark ignited, lean gasoline-air mixture. In order to research the effects of ignition system on flame propagation, two kinds of ignition system are designed, and several kinds of spark plugs are tested and evaluated. To control the discharge energy, the dwell time is varied. The initial flame development is quantified in terms of 2-D images which provides information about the projected flame area and development velocity as a function of ignition system and discharge energy. The results show that high ignition energy and extended spark plug gap can shorten the combustion duration in lean mixtures. The material, diameter and configuration of electrodes the flame development by changing the transfer efficiency from electrical energy to chemical energy and discharge energy. However these factors do not affect of flame development as much a ignition energy or extended gap does.

<div class="section abstract"><div class="htmlview paragraph">In-cylinder spray imaging by Mie scattering has been taken with frame rates up to 27,000 fps, along with high speed video photography of chemiluminescence and soot thermal radiation. Spectroscopic measurements have confirmed the presence of OH*, CH* and C2* emissions lines, and their magnitude relative compared to soot radiation. Filtering for CH* has been used with both the high speed video and a Photo-Multiplier Tube (PMT). The PMT signals have been found to correlate with the rate of heat release derived from in-cylinder pressure measurements. A high power photographic strobe has been used to illuminate the fuel spray. Images show that the fuel spray can strike the ground strap of the spark plug, break up, and a fuel cloud then drifts over and under the strap through the spark plug gap. Tests have conducted at two different spark plug orientations using a single spark strategy. The images show interaction of a fuel jet with the earth electrode, stretching of the arc, variable location for the start of combustion and significant cycle-by-cycle variations with the same operating point leading: to normal combustion, slow combustion and misfiring cycles. The high speed photography confirms that liquid droplets exist in the spark plug gap at the 10 o'clock spark plug orientation but not at the 2 o'clock spark plug orientation.</div></div>

Computational insights into flame development and emission formation in an ammonia engine with hydrogen-assisted pre-chamber turbulent jet ignition

Flow dynamics near the spark plug gap have become more important to promote more stable lean/dilute combustion in internal combustion engines. One experimental technique for the measurement of instantaneous gaseous flow in an engine cylinder is particle image velocimetry (PIV). However, PIV measurement of the flow near solid objects is difficult because of the flare due to strong scattered light from the solid objects. Therefore, methods that use fluorescent particles (f-particles) have been proposed to reduce this undesirable effect. The mass production of inexpensive inorganic-based f-particles was previously proposed by one of the authors of this paper, assuming flow measurement in a firing engine. Furthermore, flow measurement near the spark plug gap was attempted using PIV with these f-particles, whereby the unsteady flow motion near the spark plug was successfully detected. However, the measurements were conducted under atmospheric conditions at room temperature. Therefore, as a next step, investigation of the effect of ambient pressure and temperature on the fluorescence intensity of the f-particles, is required to clarify the degree of oxygen quenching and temperature quenching of the f-particles. The effect of ambient pressure on fluorescent intensity was investigated fundamentally using a constant volume vessel. As a result, the intensity of fluorescence emitted from the f-particles was almost equal at pressures between 0.1 MPa and 2.0 MPa.

This study investigates the effect of ignition parameters on the cyclic dispersion and the specific fuel consumption of a carburetted single-cylinder engine. Ignition energy measurements were made on the low- and high-voltage sides of the ignition coil, and the performance was predicted satisfactorily by a simple model with passive elements. The spark energy was varied by changing the spark plug gap and the coil-on-time. The spark energy was measured in a special calorimeter: the aim was to find a correlation between engine performance and the spark energy measured by the calorimeter. The tests were conducted at part load and low speed with a weak mixture, as these conditions are known to give high levels of cyclic dispersion. The spark calorimeter showed a higher spark plug conversion efficiency for spark plugs with large gaps. However, the spark plug gap was found to be a more significant determinant of engine performance than the spark energy measured by the calorimeter. The experimental results are preceded by a review of ignition phenomena and their influence on combustion.

The paper presents the results of the experimental research on the combustion process inside the cylinder of a large piston radial aircraft engine with dual spark plug ignition. The tests were carried out on the ASz-62IR-16X radial engine equipped with a double, electronically controlled ignition system with two spark plugs in each cylinder. The constant engine speed tests allowed for comparing the combustion processes with ignition carried out with different ignition advance angle offset between both spark plugs. In the test, the ignition advance angle for one spark plug was changed while leaving the ignition advance angle for the other spark plug. The tests performed for two engine operating points were to change the angle of the front spark plug and the rear spark plug. The analyses were based on the recorded pressure signal from one of the engine cylinders. It has been shown that the ignition advance angle offset significantly affects the combustion process. The obtained results indicate the leading role of the rear spark plug in initiating the combustion process. When ignition is carried out with a steady rear spark plug advance angle, the combustion process practically does not change when the ignition advance angle of the front spark plug changes. However, changing the rear spark plug advance angle at a constant front spark plug ignition advance angle significantly changes the combustion process.

Mixture preparation is a key contributor to both the combustion and emissions of the automotive gasoline engine. The air-fuel ratio near the spark plug may have an effect on combustion characteristics, especially at low load, since it is related to flame development. Therefore, measurements of the cycle-resolved equivalence ratio near the spark plug are particularly important for a better understanding of their contribution to combustion and emissions. This paper describes how the in-cylinder equivalence ratio was determined from the measured hydrocarbon concentrations near the spark plug using a fast response flame ionization detector (FRFID). The procedures established were then applied to a limited range of engine operating conditions, and the cycle-resolved equivalence ratio near the spark plug was determined from the measured hydrocarbon concentration. The results showed that with premixed propane fuel the cyclic variation in equivalence ratio near the spark plug was quite small and corresponded to the overall equivalence ratio from the universal exhaust gas oxygen (UEGO) sensor signal. However, with gasoline fuel the equivalence ratio near the spark plug varied by up to 10 per cent and did not coincide with the UEGO sensor signal on a cyclic basis. The variation in equivalence ratio near the spark plug affected the heat release rate, which in turn affected the indicated mean effective pressure (i.m.e.p.). The equivalence ratio excursions and its effects during acceleration and deceleration are strongly related to the exhaust emissions, fuel economy and so on. With this in mind, the quantitative measurement method using the measured hydrocarbon concentrations was studied for detailed analysis during transient conditions. It was also observed that cyclic variation in the equivalence ratio near the spark plug might be one cause of cycle-by-cycle variation.

An efficient combustion depends on many factors, such as injection, turbulence and ignition characteristics. With the improvement of internal combustion engines the turbulence intensity and internal pressure have risen, demanding more efficient and powerful ignition systems. In direct injection engines, the stratified charge resultant from the wall/air-guided or spray-guided system requires even more energy. The Paschen’s law shows that spark plug gap and mixture density are proportional to the dielectric rupture voltage. It is known that larger spark gaps promote higher efficiency in the internal combustion engines, since the mixture reaction rate rises proportionally. However, the ignition system must be adequate to the imposed gap, not only on energy, but also on voltage and spark duration. For the reported study in this work two test benches were built: a standard inductive ignition system and a capacitive discharge high energy ignition system, with variable voltage and capacitance. The influence of the important parameters energy and ignition voltage on the spark duration, as well as the electrode gap and shape were analyzed. It was also investigated the utilization of a coil with lower resistance and inductance values, as well as spark plugs with and without internal resistances.

ABSTRACTFlame acceleration and flame–shock interactions are important physical phenomena in combustion science. The primary contribution of this work is to observe different combustion phenomena in the flame acceleration process and during flame–shock interactions in a confined space with a perforated plate. The effect of the perforated plate is to generate a rapidly accelerating flame. The experiment is conducted with an improved experimental apparatus with larger optical windows to observe the complete flame development process and the results are obtained using high-speed Schlieren photography. The complete process is observed clearly, including jet flame formation, turbulent propagation, and shock formation and propagation. Meanwhile, the obvious propagation of the turbulent flame, shock waves and reflected shock waves in burnt and unburnt materials is observed clearly in our experiment in terms of flame–shock interactions. The present results indicate that the perforated plate positions can change the flame propagation as well as the in-cylinder pressure oscillation, and affect the combustion intensity in the confined space significantly. For the middle distance between spark plug and perforated plate (position A), the flame tip velocity after perforated plate increases with increasing hole size. In contrast, the significantly different flame propagation behaviors can be obviously observed for the small distance between the spark plug and perforated plate (position B). The flame tip velocity decreases with increasing hole size initially after the flame passes through the perforated plate. Subsequently, a large hole size results in a turbulent eddy with a larger eddy structure, and consequently the turbulent flame acceleration behavior becomes more obvious for the hole size of 5 mm. Furthermore, a reflected shock wave with a sequence of compression waves with oscillating propagation in the confined space is observed experimentally. The present work could provide valuable insights into super-knocking combustion in gasoline engine, fire-safe fields in mining operations and buildings.

<div class="htmlview paragraph">The first part of the paper is a brief review of the techniques needed for measuring the voltage and current during the ignition process. These techniques have been used in test rigs and an engine to gain insights into the breakdown and subsequent discharge development.</div> <div class="htmlview paragraph">New correlations are presented for breakdown voltage as functions of spark plug gap, gas composition, temperature and pressure. The discharge voltage is affected by the flow, so an elevated pressure flow rig was used to look at the effect of flow and pressure on the discharge voltage history, with different stored energies in the ignition coil. This study led to a model for the discharge voltage history, from which it was possible to deduce the flow velocity through the spark plug gap.</div> <div class="htmlview paragraph">Finally, these techniques were applied to a single cylinder, 4-valve, pent-roof combustion chamber SI engine, for determining the cycle-by-cycle variations in velocity through the spark plug at the time of ignition. The paper ends with some comparisons with LDA data.</div>

On the ignition and flame development in a spray-guided direct-injection spark-ignition engine

<div class="section abstract"><div class="htmlview paragraph">To explore the production and oxidation characteristics of soot in the flame of diesel jet under the condition equivalent to the direct injection diesel engine condition, the effect of three different important parameters (including injection pressure, injection duration, and oxygen concentration) are experimentally examined. For these purposes, a small CVCC (constant volume combustion chamber) with the volume of 60cc equivalent to the volume of combustion chamber of automotive diesel engine is used.</div><div class="htmlview paragraph">To obtain the experimental data of soot production and oxidation, in experiments, the ambient condition of temperature, pressure and oxygen concentration before injection timing are prepared by the combustion of lean hydrogen mixture (with help of 8 spark plugs) at a high temperature and pressure condition around 1000K and 4.5MPa. The common rail type injector with 8 injection holes for modern diesel engine is attached to this vessel. Injection pressures are set up at 80, 100, and 120 MPa. The effects of three important factors are analyzed including: (1) different injection pressures with constant injection mass; (2) different injection pressures with constant injection duration; (3) oxygen concentrations of 21% and 17% in volume. The optical window is attached on one side of this vessel and the full image of the spray flames can be visualized and recorded through this window by a high-speed color video camera. From the visualized color image of diesel flame, the flame temperature and the amount of soot inside the flame can be quantified by the two color method. This method is based on the theoretical principle that the light emission from the soot cloud is a thermal radiation of gray body which is a function of soot temperature and the KL factor, an index of the amount of soot.</div><div class="htmlview paragraph">The obtained results show that the injection duration and the injection rate are the dominant factors for heat release rate (HRR). On the contrary, within the experimental condition, the heat release rate is affected by both of the injection pressure and the oxygen concentration of ambient mainly at late combustion phase. The injection pressure and the injection duration give small effect on the level of flame temperature; however, the ambient oxygen concentration gives a large effect on the flame temperature.</div><div class="htmlview paragraph">Concerning the soot production and oxidation, all of the considered parameters have large effect. The interesting result is that the effect of injection pressure and ambient oxygen concentration on the maximum value of total KL factor is not so large. However, the soot production rate becomes lower as the decrease of injection pressure and as the decrease of ambient oxygen concentration, and results in the delayed arrival of the maximum total KL factor. Comparing with the HRR curve, it is revealed that the soot oxidation reaction is occurred under the very low HRR combustion in the case of low injection pressure and oxygen concentration condition.</div></div>

The most important factors affecting comfort and performance in motor vehicles are; The exhaust gases generated by the internal combustion engine are noise and vibration. The effect of these factors can be reduced thanks to the fully efficient and regular operation of the engine. The most important part affecting the efficient operation of the spark plug ignition engine is the spark plug. Spark plug failure; emission, noise and vibration values increase. These negative effects reduce vehicle comfort and increase travel costs; it also causes more damage to nature. Vehicles are designed and manufactured to ensure optimum operating parameters during production. However, changes in these parameters occur as the vehicle is used and different types of parts are used during maintenance. In this study, spark plug nail spacing; Emission, noise and vibration effects and determination of optimum nail spacing. In the experiments, iridium spark plug was used as ignition spark type. The spark plugs wear out because the engine fires continuously during operation. This wear increases the distance between the center electrode and the electrode cap and changes the resulting spark quality. According to the experiments; When the iridium spark plug nail spacing is 0.8 mm, the noise is optimum at different revolutions, the vibrations in the 0.9 mm nail spacing increase at low revolutions, and the hydrocarbon value is minimized at high revolutions in the 0.8 mm spark plug nail spacing.

<div class="section abstract"><div class="htmlview paragraph">The article presents the simulation results of the combustion process made based on a 3D-CFD mathematical model of the aircraft radial engine. The object of research was the 9-cylinder aircraft engine ASZ-62IR. The model comprised of the internal geometry of the cylinder and pipes in the cylinder head together with the inlet pipe. The model has been verified on the base of the pressure characteristics in the inlet pipe obtained from the experiment. In order to reproduce the same process of mixture formation as in the real engine, the model involved the process of induction, compression and combustion. The conducted research was aimed at verifying the influence of switching off one of the spark plugs on the combustion process. The simulation was done for three versions of ignition, for two spark plugs at the same time, only the front spark plug, only the rear spark plug. The research has been conducted in the conditions of maximum constant power of engine that is 686 kW.</div><div class="htmlview paragraph">As a result of the conducted research, the reaction progress variables in the combustion chamber representing the spread of flame and rate of heat release have been obtained. A distinct influence of the number of operating spark plugs on the combustion process has been revealed. In fact, in the case of lack of ignition in one of the spark plugs the, combustion occurs, but the process prolongs in time. In order to optimize the process of combustion, research for various angles of ignition will be conducted in the future.</div></div>