Spark Plug Research Articles

Effect of pre-chamber volume and nozzle number on turbulent jet combustion characteristics of GDI engines

There are few studies on the effect of turbulent jets on the combustion characteristics of passive pre-chamber (PC) gasoline engines, and their mechanism needs to be elucidated. Therefore, a 3-D simulation was performed using CONVERGE software. The results reveal that a modest expansion in the PC volume contributes to combustion due to the increased jet energy, but when it is too large, the above effect is weakened. In this study, at a smaller 0.8 ml volume, the combustion is still similar to traditional spark plug ignition. At middle 1.6 ml volume, the mixture concentration in the PC increases and the uniformity is better, resulting in the highest jet velocity and shortest jet duration, thus achieving the fastest flame propagation and the highest heat release rate (HRR). However, at a larger 1.8–2.0 ml volume, the mixture concentration near the spark-plug is sharply reduced, thus the reduced combustion rate in the PC leads to insufficient jet energy in the subsequent jets and resulting deterioration in combustion. An appropriate increase in nozzle number also improves combustion by introducing more ignition sources. But more nozzles not always improving the combustion. In the eight-nozzle case, three nozzles are close to the exhaust valve so that the intake is inhibited, resulting in a worsening of the ignition. The combustion under six-nozzle shows the highest HRR and shortest combustion duration. However, the combustion deteriorates at eight-nozzle, since the increase in the ignition point is not enough to compensate for the negative impact of the reduced jet intensity on combustion.

Study of activity stratification-controlled NH3–H2 combustion in a large-bore gas engine utilizing split-channel supercharge and fuel-air mixing technology

In this study, the split-channel supercharge and fuel-air mixing technology (SCS-FAM) is firstly proposed for large-bore ammonia (NH3)-hydrogen (H2) engine, which involves the separation of fuel and air intake ports to mitigate the risk of H2 backfire in intake system. We explored the activity stratification under different intake schemes and H2 blend ratios through simulation, as well as how it affects the NH3–H2 combined combustion characteristics including in-cylinder flow turbulence, temperature, concentration, and key intermediates distribution. The results show that in Scheme 2 when air entered the high swirl ratio intake 1 and fuel entered the low swirl ratio intake 2, a rich mixture was formed near the spark plug, accompanied by localized NH3 thermal reforming phenomena, which improved the activity distribution of H2. Additionally, the strong swirl promoted combustion in the squish zone and significantly shortened the post-combustion period. Scheme 2 achieved a higher indicated thermal efficiency (ITE) than Scheme 1 with a small amount of H2 addition, with the highest ITE of 42.1% obtained at 15 vol% H2 blend ratio. Notably, the addition of H2 promoted NH3 consumption and the generation of active radicals, resulting in reduced N2O emissions during the expansion stroke, but causing an increase in NO emissions.

Experimental Investigation on Compact Current Non Thermal Plasma Assisted Hydrocarbon Reforming Hydrogen Rich Gas

On-board vehicle hydrogen-rich gas extraction of gasoline reforming utilizing for fuel cells and GDI-engine lean burn combustion enhancement NOx trap applications. A non-thermal plasma discharge electrode that produces a reduce current, increased voltage 15kV source arc plasma fuel reformer is designed to operate at an arc frequency of 50 Hz. The operating factors gasoline equivalence ratio between 4 and 6.and electronically control by the fuel injector and eliminating ground spark plug plasma arc generation. The plasma arc non-thermal reformer gasoline converted into gas that contains partial oxidation contains combustible gases like hydrogen (H2), CO, non-combustible gases like CO2, N2, and a small quantity of H2O. The nonthermal plasma technology alternative for on-board hydrogen vehicle applications.

Analysis of Energy Transfer in the Ignition System for High-Speed Combustion Engines

In order to produce reliable and reproducible ignition of lean fuel–air mixtures and highly stratified mixtures, it is necessary to ensure a high concentration of spark discharge energy and to provide a strong energy impulse for the triggering of chain processes of chemical decomposition of fuel molecules. For this reason, studies have been undertaken on the flow of electrical energy from the ignition system to the spark plug and on the formation of an electric discharge arc with a high concentration of thermal energy. The experimental results were obtained using an ignition coil energy test stand and a constant volume chamber with high-speed spark discharge recording capability. It was confirmed that increasing the charging time of the ignition coil from 0.5 ms to 5.0 ms increases the energy delivered to the coil from 9.5 mJ to 330 mJ. In the same range, the energy generated by the coil was recorded to range from 4.2 mJ to 70 mJ. The coil’s efficiency was found to decrease with increasing charging time from 45% up to 20.5%. Further energy losses were presented when the spark discharge energy was analyzed. In the paper, the results of investigations concerning electric discharge arc development have been presented, illustrated by a few exemplary photos, and discussed. The mathematical interpretation of the electrical energy flux in the ignition system resulting from the energy of the discharge arc has been conducted and illustrated by some functional independences and relationships.

The operating parameter optimization of spark duration effect on the performance and emission characteristics of direct-injection propane by genetic algorithm

It is challenging to optimize of the effect of spark discharge duration on low carbon direct injection combustion of propane from a specific aspect of the internal combustion engine. The strategy in this paper combines a genetic algorithm (GA) with an artificial neural network (ANN) to enhance efficiency of a large bore diesel engine modified with spark plug and fueled with propane direct injection under various spark timing durations and identify its engine performance parameters and corresponding conditions for operational control purpose. In-cylinder performance experiments were used to create 756 datasets for training, testing, and validating the ANN with 16 neurons on each hidden layer, respectively. The selected performance parameters were the heat release rate, turbulent kinetic energy, indicated mean effective pressure, and indicated thermal efficiency. The NOx and CO emissions are improved by 7.14 % and 0.74 %, respectively, by the optimized ANN model. In addition, compared to an experimental result, the model improves the indicated thermal efficiency, heat release rate, and indicated mean effective pressure by 1.35 %, 0.37 %, and 0.04 %, respectively. The combined of ANN-GA is effective in identifying the optimal operating parameters for in-cylinder performance and emission.

Effects of charge motion on knock and thermal efficiency under high load condition of a heavy-duty natural gas engine

Nowadays, the carbon-neutral trend and the crude oil crisis have brought natural gas into increasing focus. However, heavy-duty engines fueled by natural gas have been plagued by thermal efficiency and knocking limitation problems. Well-structured charge motions can enhance thermal efficiency and concurrently mitigate knock, however, there is a lack of comprehensive work involving charge motions. In this paper, numerical simulation is employed to investigate the impact of charge motion on knock and thermal efficiency under high load conditions for a heavy-duty spark-ignition natural gas engine. The findings indicate that in the configuration with intense swirl, the diminished turbulent kinetic energy (TKE) at the combustion chamber’s base lessens the convective heat exchange between the fresh charge and the heated exhaust gases, resulting in a noticeable high-temperature zone and triggering hot spots. In configurations with inclined swirl and strong tumble motion, the extensive tumble motion near the spark plug region close to top dead center leads to an asymmetric flame front shape, determining the location of hotspots. The research also revealed that excessive tumbling motion and TKE can increase the likelihood of engine knock, while appropriate cylinder charge motion can improve the knock resistance of the engine to some extent, the maximum reduction in knocking intensity can reach 92.5%. The optimized combustion systems can significantly improve the initial combustion rate, shorten the ignition delay period, and advance the combustion center. With the combined effects of ignition timing and charge motion, the total indicated specific power per unit of fuel mass is increased in the optimized systems. Compared to the original combustion system, the indicated thermal efficiency within the knocking boundary can be improved by 1.11%.

Low-Temperature Reforming Products coupling Spark Plug on Gasoline Compression Ignition and Combustion Characteristics under Low-Load Condition

Low-Temperature Reforming Products coupling Spark Plug on Gasoline Compression Ignition and Combustion Characteristics under Low-Load Condition

Detection of Nickel Atoms Released from Electrodes in Spark Discharges Using Laser-Induced Fluorescence.

The reduction of greenhouse gas emissions and the effort of carbon neutrality require the improvement of spark-ignition engines in terms of efficiency and capability to operate on renewable fuels. The electrode wear of spark plugs, used for ignition of novel fuels and lean mixtures, emerges as a significant challenge in this transition. Understanding the physical mechanism and influence of spark operation parameters of the wear process is thus important. Compared to the conventional methodology of performing long-term wear tests, laser-based optical diagnostics methods are capable of assessing electrode wear during one single or a few spark discharges. In this work, the necessary initial steps required for performing optical investigations using laser-induced fluorescence (LIF) are presented. Several excitation pathways of nickel atoms were investigated, and 336.96 nm was identified as the optimal one. This excitation approach yielded emissions between 338.75 and 353.58 nm, effectively avoiding the major interference from N2 plasma emission in spark discharges. Additionally, a linear relationship in fluorescence signal intensity with excitation energy up to 400 µJ was observed. These findings indicate the potential of LIF for in situ diagnostics of electrode wear, contributing to engine development in both efficiency and compatibility with sustainable fuels.

Numerical study on the inner spray and combustion of active pre-chamber jet ignition for achieving higher performance of a hybrid engine under ultra-lean conditions

The mechanism of active pre-chamber (APC) inner fuel-air mixing, initial flame kernel formation, and jet flame evolution is still not clear. In this study, different APC inner geometry structures coulped with different mixture status were designed to synthetically analyze the inner gas flow, spray mixing, and hot jet flame evolution. The results showed that the APCs with small cone angles of 45° and 50° could promote the fuel-air mixing and spray atomization in a wider APC top space compared to APCs with large cone angles of 60° and 65°. An appropriate APC cone angle of 55° could reduce rich mixture zone and facilitate rapid flame kernel formation, fast flame propagation, and high jet activity, which was good for igniting the in-cylinder ultra-lean mixture. APCs with real fuel injection showed one heat release rate (HRR) peak, while APCs filled with homogeneous mixture showed the typical two peaks in the HRR profiles, the suitable mixture in APC duct section burned and formed the second HRR peak. The short thick APC induced the rich mixture distributed around the spark plug to form the initial flame kernel and showed a faster concentrated combustion process along with a higher pressure difference between APC and MC.

Laboratory systems for detonation research

Decarbonizing global energy systems is among the most pertinent challenges in the climate crisis. Tightly tied to the economic prosperity of a nation and responsible for more than 75% of global emissions, decarbonization of the energy sector will require well-developed solutions. The emergence of detonation engines can reduce emissions in aviation and gas-fired power generation, with theoretical efficiencies 40% lower than conventional engines. These efficiencies have yet to be realized in practice, due to our lack of understanding of detonation propagation and its instabilities. This project aimed to develop the laboratory systems required to study detonations. To this end, a long rectangular channel was manufactured and outfitted with a gas handling system to inject a mixture, an ignition system, pressure transducers to capture the propagation characteristics, and an optical system enabling Schlieren photography. The gas handling system uses sonic nozzles, thus flow rate is a linear function of upstream line pressure. Each line contains a pressure transducer, microcontroller to process signals, LCD for pressure readout, and a regulator for adjustment of the line pressure. The ignition system uses an ignition box that steps up a 12 V supply to 400 V, an ignition coil raising the voltage to 15-40 kV, and a spark plug to ignite the mixture. Ignition, pressure transducer signal acquisition, and Schlieren photography are all synchronized using a NI-6356 DAQ with LabVIEW. The DAQs analog input ports receive readings from the pressure transducers along the channel, the timing of which and known distance between transducers allows for velocity calculations. The schlieren system utilizes the digital output channels to synchronize camera shutter with an LED driver, and parabolic mirrors, positioned to optimize schlieren imaging. The LED driver requires greater current than produced by the DAQ thus a current amplifier circuit is used to bridge the DAQ and driver.

Numerical Study on the Potential of Stratified Mixture to Improve Thermal Efficiency and Reduce Carbon Emissions in High-Speed Gasoline Direct Injection Engine

Abstract Stratified combustion improves the indicated thermal efficiency (ITE) of gasoline direct injection (GDI) engines, but the mechanism of its impact on unregulated emissions remains unclear. In this simulation-based study, double injection strategies were used to create stratified mixtures in the cylinder. The results indicated that as the second fuel injection quantity (FIQ) was increased or as the second fuel injection timing (FIT) was delayed, the oil-film mass increased, leading to an increase in soot emissions. The formation of a large area of stoichiometry (STO) region at the spark plug and at its right side increases the laminar flame velocity and improves the ITE. At 4000 rpm, the ITE of case2-2 (with a second FIT of −220 °CA after top dead center (ATDC) and a second FIQ of 65.5 mg) increased by 1.6% compared to the original scheme. With the increase in STO area, NOx emissions and the content of CH3OH and CH2O increased, while carbon monoxide (CO) and greenhouse gas emissions showed a decreasing trend. Compared to the original scheme, CO and greenhouse gas emissions decreased by 1.97% and 6.7%, respectively, in case2-2. This study provides guidance for the development of GDI engines with high ITE and low carbon emissions.

The Effect of Number of Spark Plug Ground Electrodes and Octane Rating on Single Cylinder Engine Performance

The Effect of Number of Spark Plug Ground Electrodes and Octane Rating on Single Cylinder Engine Performance

Enhancement of thermal and mechanical properties of PMMA nanocomposites by adding spark plug ceramic waste

In this research, poly methyl methacrylate (PMMA) resin was used as a base material and spark plug ceramic waste (CW) particles as a support material with different weight ratios (0%, 1%, 2%, 4%, 6%, 10%, 14%, and 20%) to study the thermal and mechanical properties through diffraction examination. FE-SEM surface structure images showed that the fracture surface of the (94% PMMA +6%CW) nanocomposite sample manifests a good distribution of particles at low and high levels. The result showed that the thermal conductivity (K) slightly increased until it reached the maximum value (0.6 watt/m.ºC) at the ratio (86%PMMA +14%CW). For the impact strength, it was noticed that the impact strength of PMMA increases with the increased weight ratios (1, 2, 4, 6, 10, 14, and 20%) of fine powder of ceramic waste compared with pure PMMA to reach the maximum value (6.02 kJ/mm2) at the sample (94% PMMA +6%CW) under L.C. Moreover, after 30 days of submersion in water, the PMMA reinforced with ceramic waste particles had enhanced impact strength. The shore D-number readings for all of the samples showed an increase as a result of the findings of nanocomposite compared with PMMA pure, where the sample (94% PMMA+6%CM) attained the greatest shore D numbers (87 H.NO). The compressive strength at the weight percentage (99% PMMA + 1% CW) was somewhat reduced. Then the compressive strength increased till it reached its maximum value (29.94 MPa) at the weight percentage (94% PMMA + 6% CW).

Diesel Control Strategy in Dual-Fuel Engine

Dual-fuel engines are capable of operating using a mixture of two different fuels. Generally, the primary fuel is a gaseous fuel (CNG, LPG, Hydrogen), while diesel is used as a pilot ignition source, i.e. functioning on heat of compression and not a spark plug. There have been a few dual-fuel engine strategies to control the speed of the engine based on varying loads, but these require the addition of complex mechanisms to the existing systems. This paper discloses a methodology for controlling the diesel quantity during dual-fuel operation. According to the engine speed and accelerator pedal position, a gaseous fuel injector in the system injects a predetermined quantity of gaseous fuel. Based on the regulated quantity of gaseous fuel, the intake manifold creates an air-gas fuel mixture. The air-gaseous fuel mixture and a metered quantity of diesel are delivered to the combustion chamber via the intake manifold, fuel injection pump, and other components. The governor and fuel injection pump work together to measure the quantity of diesel according to speed and load conditions. During dual-fuel operation, the governor regulates engine speed by controlling the quantity of diesel delivered to the engine based on speed and load conditions. Keywords: Dual-fuel, Control Strategies, Off-Road Engines, Combustion, Emissions, Diesel Replacement

Converting compression ignition engine to dual-fuel (diesel + CNG) engine and experimentally investigating its performance and emissions

Abstract One of the suitable solutions for burning natural gas in diesel engines is the use of dual-fuel technology. In this study, the MT440C compression ignition engine has been converted to dual fuel (diesel + CNG) simultaneously combustion of diesel fuel and natural gas, with the least amount of engine changes and using the most amount of natural gas. The ignition of the engine was in the range of the governor. Experiments in stable conditions for the working modes of the engine were performed with pure diesel fuel and mixed gas diesel fuel. The effects of natural gas fuel as the main fuel and diesel fuel as the spark ignition on a 4-cylinder compression ignition engine were investigated on the performance and emissions. According to the engine speed and load, the amount of diesel-fuel injection was adjusted by making mechanical changes in the governor, while the ignition system was not used. These tests were performed at engine speeds of 1,200, 1,400, 1,600, 1,800, and 2,000 rpm, using single diesel fuel and dual fuel (diesel + CNG). These data were collected in the Engine Research Center of Tabriz Motorsazan Company, and experimental runs were repeated three times One of the goals of this research is to reduce the consumption of diesel fuel, and in the current study, compressed natural gas (CNG) is 72% and diesel is 28% of the dual fuel in idling. This study showed that the emission of some pollutants increased and some decreased in the dual-fuel mode. Therefore, more research is needed on modifying the diesel injection system as a spark plug or the CNG injection system to reduce the emission of greenhouse gases.

Laser ignition of hydrogen/air mixtures in a constant-volume combustion chamber using a pulse-burst Nd:YAG/Cr4+:YAG laser spark plug

In this study, characteristics of laser ignition of H2/air mixtures are investigated in a constant-volume combustion chamber using a compact, passively Q-switched Nd:YAG/Cr4+:YAG laser spark plug. Ignition was conducted at a single point, with precise timing achieved through two laser modes of operation: delivering a single laser pulse and operating in pulse-burst mode, emitting trains of up to five laser pulses. Experiments covered a wide range of relative equivalence ratios (λ= 1.5 to 5.0) at 1 bar initial pressure and extended to 9 bar. Under similar pressure conditions, igniting H2/air mixtures with higher λ values (lean mixtures) results in a reduction of maximum pressure and a slower combustion process. Conversely, maintaining the same λ value for H2/air mixtures, while elevating the initial pressure, yields higher maximum pressures, but concurrently decelerates the combustion process. Pulse-burst mode laser ignition expedited combustion, especially for lean mixtures (λ> 4.0), showcasing advantages over single-pulse laser ignition. Additionally, lean ignition limits were determined at different pressures, revealing pressure-dependent differences between single pulse and pulse-burst modes laser ignition. These results provide insights into the features of laser ignition with pulse trains of H2/air mixtures and the use of this ignition technique in hydrogen-powered reciprocating engines.

Investigation on the lean-combustion characteristics of non-uniform orifice pre-chamber spark plug in low engine speed working conditions compared with high energy spark ignition

For a long time, pre-chamber jet ignition has been an effective method to achieve stable lean-combustion of the engine. However, due to the lack of an additional fuel injector, the passive pre-chamber easily leads to unstable combustion and even misfires during the engine’s low-speed working conditions. This study used simulation and optical single-cylinder engine visualization experiments to investigate the ignition and combustion performance of the pre-chamber spark plug (PCSP) ignition system and different orientations of the scavenging jet nozzle in the cylinder. The results indicate that the PCSP at low speed (1200 r/min) can improve the lean-combustion load performance by up to 6.7% compared with traditional high-energy spark ignition but cannot significantly improve the lean combustion limit and stability. In addition, under each λ condition, the scavenging jet nozzle face toward one of the intake valves (IV2) is most advantageous. The effect of lean combustion on reducing NO began to manifest after λ > 1.3 and achieved the best at 1.6. This kind of jet ignition pre-chamber provides a more stable ignition solution than high-energy spark ignition for low speed and medium/low load aspects.

Effective lifetime of Ni laser induced fluorescence excited at 336.9 nm during spark plug discharge

In this study, the laser induced fluorescence lifetime of Ni atoms in ambient air with presence of a plasma discharge was measured for the first time. Free Ni atoms were generated in air at a pressure of 1 bar by spark plug discharges driven by an inductive coil. The Ni atoms were excited at the 336.957 nm absorption line by a 336.96 nm, 90 ps laser pulse and the resulting temporally resolved decaying fluorescence signals were captured by a PMT. An effective fluorescence lifetime of about 1.1 ns was observed for the fluorescence signal within a 7.4 nm detection window centered at 345 nm. Further analysis also revealed that the lifetime of the transition showed statistically insignificant change throughout the duration of the discharge. The peak intensity of the fluorescence signal was found to be proportional to the integrated signal intensities. This in turn suggests that the integrated fluorescence signals in the aforementioned spectral region are proportional to the population density of ground state Ni atoms in the detection volume. The number density of free Ni atoms in the spark gap was measured over time during the plasma discharge, showing an accumulating trend in the beginning phase of the discharge followed by a slow decrease until the termination.

Computational analysis of piston shape effects on in-cylinder gas flow, fuel-charge mixing, and combustion characteristics in a two-stroke rod-less spark ignition opposed-pistons engine

Compared with the traditional in-cylinder direct-injection spark ignition engine, the side-injection and side-spark-ignition characteristics of the two-stroke opposed-piston engine increase the ignition kernel offset and flame propagation distance. Increasing the flame propagation speed can to some extent solve the drawbacks caused by the non-central arrangement of spark plugs. The combustion chamber structure plays a crucial role in gas flow, fuel-charge mixing, and combustion characteristics. Therefore, three pistons were designed and comparatively analyzed in this study. The results show that: The pancake piston is beneficial to maintaining the intake swirl strength due to its simple and smooth spherical arc structure. The swirl strength of the pit and pit-guided piston decreases obviously, and the tumble strength can be maintained well. Compared to pancake and pit-guided pistons, the average TKE for the pit piston increased by approximately 25%, with a more concentrated distribution at the spark timing. The pancake piston exhibits the best scavenging performance, reducing the residual exhaust gas ratio by 2.1% and fresh air loss by 3.3% to the pit piston. A stable ignition core can be formed at the spark timing, but significant differences are observed in the flame propagation process for three pistons. Compared to the pit-guided piston, the pit piston has a 0.3% decrease in the indicated thermal efficiency, but a 13.1% decrease in combustion duration, which reduces knock tendency.

Ceramic materials as an alternative for conventional spark plug electrodes

AbstractLarge gas engines are typically applied to compensate for peak loads and grid instabilities in the electric power supply. A key component of these engines is the spark plug. Because of the harsh conditions encountered in their use, the spark plug electrodes are subject to significant wear. Conventional electrodes are expensive due to the precious metal alloys they contain. As an alternative, ceramic materials from the groups of silicide, carbides, and nitrides were selected for preliminary experiments that investigate functional as well as mechanical properties and wear behavior. Because of the harsh conditions during operation, the new materials must have a high melting temperature, good thermal shock resistance, high thermal conductivity, and high corrosion/oxidation resistance as well as high density. It was found that the mechanical and thermomechanical properties of certain ceramic candidates are sufficient for application as spark plug electrodes. Furthermore, the chosen ceramic materials achieve an adequate performance in terms of secondary voltage trace and ignition behavior. However, wear resistance may not be sufficient for service times longer than the service time of existing spark plugs and further research is still necessary before ceramic electrodes may be established as a commercial alternative to existing electrodes.