Spark Plug Location Research Articles

Mixing measurement on hydrogen jet by LIBS under various injection strategies

Favorable fuel properties of hydrogen for combustion system opens a new avenue to achieve deep decarbonization in transportation sector. Meanwhile, various technical challenges including low volumetric energy density, nitrogen oxide emissions, and backfire impede successful implementation of hydrogen in combustion engines. To overcome those issues, stratified charge combustion (SCC) is considered to optimize engine performance and emissions. As direct injection approach is utilized in SCC mode, ensuring quality of air-fuel mixing in combustion chamber is crucial. This study aims to understand hydrogen mixing behavior by quantitative measurement on equivalence ratio using laser-induced breakdown spectroscopy (LIBS). This measurement has been conducted under non-reacting conditions, employing realistic injection strategy, multiple injection, so the influences of dwell time, and split ratio are addressed. In addition to LIBS, this study includes a morphological analysis of the hydrogen jet, which was visualized using high-speed schlieren imaging. The experimental data showed that shorter first injection duration was resulted in an increased jet width at the spark plug location, which reduced the equivalence ratio within the center of the jet. Longer dwell time also demonstrated wider jet width at the spark plug location, reducing the equivalence ratio within the center of the jet.

The optimization of leading spark plug location and its influences on combustion and leakage in a hydrogen-fueled Wankel rotary engine

The hydrogen-fueled Wankel rotary engine with excellent power and emission characteristic is under spotlight, while the leakage is still the major problem for Wankel rotary engine, especially the leading spark plug leakage. The peak pressure is increased from 3.34 MPa to 3.52 MPa and the indicated thermal efficiency reaches maximum value of 38.29% when the moving distance of leading spark plug is −6.5 mm, and the mass of leakage fresh mixture is reduced from 0.00311 g to 0 g. When leading spark plug is moved to minor axis, the flow field structure of working chamber is enhanced. However, the peak pressure and indicated thermal efficiency decrease when the moving distance of leading spark plug exceeds −6.5 mm. The excess leakage residual gas has negative effects on combustion. The optimum moving distance of leading spark plug is −6.5 mm at 3000 rpm with λ of 1.6.

A knock study of hydrogen-fueled Wankel rotary engine

Hydrogen-fueled Wankel rotary engine (HWER) is an excellent power device with superior power and emission performances. Besides, unlike hydrogen-fueled reciprocating piston engines, HWRE is less prone to backfire due to its structural advantages. However, limited by its long combustion chamber, knock, one of abnormal combustion in engines, still hinders the development of HWER. Hence, based on this consideration, the goal of this work is to investigate the knock of HWRE from different aspects, including ignition timing, spark plug number, spark plug location, excess air ratio and engine speed, to provide relevant information for the design of hydrogen-specific WRE. The results show that the knock intensity gradually increases as the ignition timing is advanced, the excess air ratio is decreased and the engine speed is increased, but the knock duration shows different variations. Adopting dual spark plugs tends to lead to stronger knock caused by unstable combustion of hydrogen, while only adopting leading spark plug tends to lead to the knock caused by auto-ignition. When dual spark plugs are used, the leading spark plug is more responsible for the knock caused by unstable combustion and the trailing spark plug is more responsible for the knock caused by auto-ignition.

Effect of Spark Plug Location on Combustion, Performance and Emission of High-Speed Digital Three Spark Ignition (DTSI) Engine Fueled with Gasoline and Hydrogen

<div class="section abstract"><div class="htmlview paragraph">The United Nations sustainable development goals can be met by reduced use of fossil fuels in the power & transportation sector and by protecting the environment. Various efforts to utilize alternative fuels (with low or without carbon contents) in the transportation sector are in the anvil. In this research, an experimental study is performed on a single cylinder gasoline engine of 200 cc with port fuel injection and digital three spark ignition (DTSI). The effect of spark plug location is analyzed using gasoline and hydrogen fuels separately. The combustion, performance, and emissions characteristics are analyzed at 6000 rpm, Wide Open Throttle (WOT) condition with a compression ratio of 11:1 for three different spark plug locations, i.e., at Center, Left-hand side and Right-hand side of combustion bowl. The following are the best results for a centrally located spark plug in comparison with the spark plug located at the sides. The volumetric efficiency is increased by 3.6% and 10% when tested with gasoline and hydrogen fuel; the maximum brake thermal efficiency (BTE) obtained for hydrogen is 38.05%, and gasoline is36.8%. The maximum combustion pressure recorded is 62.5 bar and 54.9 bar for gasoline and hydrogen fuel. The effects of spark plug locations on engine power output, the heat lost to the coolant, the heat lost to exhaust gases, unaccounted heat, heat release rate (HRR), and cumulative heat release rate (CHRR) are also studied. The net heat release rate (NHRR) is increased by 75 % with gasoline and 107 % with hydrogen. The mean gas temperature (MGT) recorded with gasoline is 2746 K, and 2232 K for hydrogen, this decrease in MGT for hydrogen is due to lean burn combustion at 1.6 equivalence ratio. The increase in NOx emission for gasoline and hydrogen fuel is 37.5 % and 58 % as the combustion is proper with increased NHRR, and MGT.</div></div>

G-equation based ignition model for direct injection spark ignition engines

To accurately model the Direct Injection Spark Ignition (DISI) combustion process, it is important to account for the effects of the spark energy discharge process. The proximity of the injected fuel spray and spark electrodes leads to steep gradients in local velocities and equivalence ratios, particularly under cold-start conditions when multiple injection strategies are employed. The variations in the local properties at the spark plug location play a significant role in the growth of the initial flame kernel established by the spark and its subsequent evolution into a turbulent flame. In the present work, an ignition model is presented that is compatible with the G-Equation combustion model, which responds to the effects of spark energy discharge and the associated plasma expansion effects. The model is referred to as the Plasma Velocity on G-surface (PVG) model, and it uses the G-surface to capture the early kernel growth. The model derives its theory from the Discrete Particle Ignition (DPIK) model, which accounts for the effects of electrode heat transfer, spark energy, and chemical heat release from the fuel on the early flame kernel growth. The local turbulent flame speed has been calculated based on the instantaneous location of the flame kernel on the Borghi-Peters regime diagram. The model has been validated against the experimental measurements given by Maly and Vogel,1 and the constant volume flame growth measurements provided by Nwagwe et al.2 Multi-cycle simulations were performed in CONVERGE3 using the PVG ignition model in combination with the G-Equation-based GLR4 model in a RANS framework to capture the combustion characteristics of a DISI engine. Good agreements with the experimental pressure trace and apparent heat-release rates were obtained. Additionally, the PVG ignition model was observed to substantially reduce the sensitivity of the default G-sourcing ignition method employed by CONVERGE.

Energy optimization of a micro-CHP engine using 1-D and 3-D modeling

This research focused on utilizing numerical simulation tools to improve the performance of a micro-CHP engine. The engine was developed at West Virginia University by screening candidate technologies and implementing those which were balanced between practicality and cost. The engine was a 34-cc, two-stroke engine which was modified to operate on low-pressure direct injection of natural gas combined with resonant intake and exhaust systems. This engine served as a baseline engine design. A 1-D simulation was developed and trained based on the baseline engine geometry and experimental data collected from laboratory experiments. After verifying the 1D model with measured data from the baseline configuration, a genetic algorithm approach was used to optimize the exhaust resonator design such that the fuel efficiency was maximized. Based on simulation outcomes, a new exhaust resonator was fabricated and tested. The experimental results showed an 8.3% improvement in brake thermal efficiency (BTE) compared to the baseline design. The test results of the optimized exhaust design were used in a 3-D CFD cold flow model to optimize the spark plug location to exploit charge stratification. The 3-D simulations suggested an alternative spark plug location, which was then applied on the engine and improved results were verified with additional experimental operation. The experimental results showed relative increase in BTE of 5.7% and a 4% decrease in total unburnt fuel compared to the original spark location.

Effects of split direct-injected hydrogen strategies on combustion and emissions performance of a small-scale rotary engine

To achieve more efficient and robust combustion, split direct-injected hydrogen as a new injection strategy for rotary engines was used to clarify the influences of various injection parameters, including hydrogen amount for each pulse, the dwell between pulses, and secondary injection pulse-width, on combustion performance and emissions formation by CFD modeling. The results of this investigation confirmed the benefit of split direct-injection as a useful means to govern mixture stratification which enabled the combustion more effective and rapid compared to single-injection mode. Enhanced combustion could be achieved by increasing the mass fraction of post-injection with an optimized dwell between injections. Further investigation on secondary injection pulse-width demonstrated that engine performance was substantially improved with a wider second injection pulse. From one side, as the secondary injection pulse-width was increased, the surrounding mixture distribution of the spark-plug location was richer, which was confirmed as a beneficial inhomogeneous circumstance of hydrogen to accelerate the burning rate. From another side, strong tumble level and turbulence intensity were of significant importance for facilitating the combustion process and getting optimal thermal efficiency. For emissions formation, split direct-injected hydrogen made a near-zero HC and CO emissions at the price of a comparable increase of NOx emissions.

Performance and combustion characteristics of a retrofitted CNG engine under various piston-top shapes and compression ratios

ABSTRACT Compressed natural gas is one of the alternative fuels for internal combustion engines as they produce less smoke and greenhouse gas emission. Understanding the combustion characteristics of compressed natural gas engines help experts to come up with better combustion chamber designs for high performance and low emission engines. In this study, three different designs of piston bowl geometry in a retrofitted compressed natural gas engine were investigated in relation to engine performance and its combustion characteristics. Three types of piston-tops including two concentric bowls and one eccentric bowl operated with two different values of compression ratio (11.5:1 and 12.5:1) were the subject of the current research. Based on the results from the experiment and simulation performed in this investigation, while differences in bowl-in-piston design did not have any significant effect on engine performance and combustion characteristics of port injection compressed natural gas engines, the authors observed a significant impact of advance ignition angle and spark plug location relative to bowl’s centerline having on the combustion process and engine performance characteristics. As a result, the application of concentric bowl-in-piston and compression ratio of 11.5:1 was found to yield the lowest brake specific fuel consumption and the highest brake power. The particular outcome presents a potential strategy for the combination of piston-top shape and compression ratio in compressed natural gas engine application to attain high combustion efficiency.

Ignition Diagnostics in EGR- and Air-diluted Methane/Air Mixtures Using Spark Induced Breakdown Spectroscopy

ABSTRACT A diagnostic tool based on Spark Induced Breakdown Spectroscopy (SIBS), designed and developed for providing information on the mixture composition at the spark plug location, was successfully used in diluted methane/air mixtures at engine relevant conditions. The INSIDE technique (INduced Spectroscopy for Ignition Diagnostics in Engines) allows deriving information on the local fuel to air equivalence ratio (φ) in the vicinity of the spark plug and on operating pressure based on the features of the spectral emissions. In the present work, a capacitive discharge ignition (CDI) system is used for the first time for SIBS-based ignition diagnostics in spark-ignition engines’ relevant conditions. The mixture dilution is performed following different approaches: dilution with synthetic EGR, dilution with pure nitrogen, and dilution through φ variation with and without constant EGR addition. Spectral signatures are measured in the spark plug location, and the peaks intensities of four atomic lines (hydrogen at 656 nm, nitrogen at 744–746 nm, carbon at 765–769 nm and oxygen at 777 nm) are compared to the non-diluted stoichiometric mixture. The atomic peak intensity ratios show distinct trends depending on the dilution strategy selected. Therefore, the atomic line ratios can be used to extract information on the local mixture composition also in the case of EGR dilution.

Theoretical investigation on combustion characteristics of ethanol-fueled dual-plug SI engine

In this study, effects of equivalence ratio, spark timing and spark plug number and locations on combustion characteristics were theoretically investigated using an ethanol-fueled dual-plug SI engine. Two-zone quasi-dimensional model was used throughout analyses. Three spark plug configurations (diagonally, centrally and side located), three equivalence ratios (0.8, 0.9, and 1.0), and three spark timings (−30, −25, and −20 CA @ BTDC) were considered to analyze variation of total burn duration, mass fraction burned, cylinder pressure, and temperatures (exhaust and maximum burned gas). Variation of mass fraction burned and cylinder pressure were also investigated at lean mixture ratio and 2800 rpm (MBT engine speed). Lastly, the effect of engine speed on total burn duration, maximum cylinder pressure and aforementioned temperatures were investigated in the range of 1000–6000 rpm. The findings show that dual-plug configuration yields approximate combustion characteristics by comparison with centrally located single plug configuration in ethanol-fueled SI engine.

Effect of vertical location of the spark plug on the performance of a raw biogas-fueled variable compression ratio spark ignition engine

The present experimental investigations deal with the spark plug location and its effect on the performance and emission of a 100% raw biogas-fueled variable compression ratio engine. Different mea...

A study of hydrous ethanol combustion in an optical central direct injection spark ignition engine

The aim of this experimental work was to improve understanding of the influence of hydrous ethanol on combustion in an engine demonstrating a tendency for biased flame migration towards the hotter exhaust walls as often reported for typical modern pent roof design IC engines. The work aimed to uncover the degree of residual water content that can be reasonably tolerated in terms of combustion characteristics in future ethanol SI engines (with the energy required to reduce water levels then potentially reduced). The experiments were performed in a single cylinder optical research engine equipped with a modern central direct injection combustion chamber and Bowditch type optical piston. Results were obtained under part-load engine operating conditions (selected to represent typical highway cruising conditions) with hydrous ethanol at 5%, 12% and 20% volume water. Baseline results were obtained using pure isooctane. High-speed cross-correlated particle image velocimetry was undertaken at 1500 rpm under motoring conditions with the intake plenum pressure set to 0.5 bar absolute. The horizontal imaging plane was fixed 10 mm below the combustion chamber “fire face”. Comparisons were made to CFD computations of the in-cylinder flow. Complimentary flame images were obtained via the “natural light” (chemiluminescence) technique over multiple engine cycles. The flame images revealed the tendency of an iso-octane fueled flame to migrate towards the exhaust side of the combustion chamber, with no complimentary bulk air motion apparent in this area in the horizontal imaging plane. The faster-burning ethanol offset this tendency of the flame to migrate towards the hotter exhaust walls. The fastest combustion rate occurred with pure ethanol, with higher water content (>5%) generally slowing down the flame speed rate to 10.64 m/s from 10.92 of ethanol and offsetting the flame speed/migration benefit (in good agreement with recent laminar burning velocity correlations for hydrous ethanol). When adding 20% water to ethanol the combustion rate was significantly slower (8.2 m/s) with a considerable increase in flame shape distortion as quantified by flame image shape factor values. The results demonstrate how the added water increases flame distortion and leads to higher flame centre displacement. Such flame centre displacement could potentially be offset in the future with a spark plug location biased further towards the intake side of the chamber (albeit sometimes practically constrained by the priorities given to intake valve sizing and local cooling jacket design). The results indicate that ethanol fuels offset such bias flame growth and allow residual water to be tolerated for an equivalent degree of biased flame migration. The implication is reduced fuel production energy and cost required to produce usable ethanol fuels.

Development of a quasi-dimensional, fractal-base combustion model for SI engines by simulating flame-wall interaction phenomenon

A quasi-dimensional thermodynamic model was developed using concept of the fractal-geometry combustion model by focusing on the behavior of the natural gas flame near the combustion chamber walls in SI engines. A new wall-flame interaction sub-model was designed and implemented in the thermodynamic model by considering the flame geometry and temperature of the combustion chamber walls. Near the walls, the dimensionless factor affects the fractal combustion model which reduces the heat release rate (HRR). First, the combustion process of natural gas fueled SI engine was simulated using a CFD software and the flame geometry was extracted for each crank angle. The results were validated with experimental data at various engine operating conditions so that the results were in good agreement with the corresponding experimental data. The results show that the concentric spherical flame propagation assumption is not true for the off-center spark plug. The walls near the flame prevent its propagation and its shape deviates from the spherical form. The points of flame collisions on the walls are one of the determinant factors in the heat release process. The flame quenching and HRR vary at different walls of the combustion chamber and both of them are proportional to the wall temperature and flame area affected by the walls. Finally, it can be concluded that, natural gas turbulent flame propagation is occurred in three stages: 1- The initial propagation of flame with high acceleration, in which 15% of the fuel is burned with a high HRR. 2- Collision of the flame with the floor of the piston, HRR continues with almost constant rate, in which 30% and 50% of the fuel is burned for the off-centered and centered spark plug locations, respectively. 3- Deceleration of the flame propagation after colliding with the side walls, in which 55% and 35% of the fuel is burned for the off-centered and centered spark plug locations, respectively.

Combined effects of intake flow and spark-plug location on flame development, combustion stability and end-gas autoignition for lean spark-ignition engine operation using E30 fuel

Lean or dilute spark-ignition engine operation can provide efficiency improvements relative to that of traditional well-mixed stoichiometric spark-ignition operation. However, to maintain a sufficiently short burn duration with the direct-injection spark-ignition engine hardware of the current study, mixed-mode combustion is required for operation with ϕ < 0.6. Such mixed-mode combustion uses a combination of deflagration and end-gas autoignition whereby the pressure rise of the deflagration-based combustion compresses the end-gas reactants to the point of autoignition. For better understanding of the transition from deflagration to autoignition, it is desirable to apply optical diagnostics. However, with the use of a single centrally located spark plug, the end-gas is found at the periphery of the combustion chamber, where it is difficult to examine optically. To overcome this, two additional spark plugs were mounted in the pent-roof gables (called East and West). Performance testing was performed for five different spark strategies: Central Only, East-West, ALL Three, East Only, and West Only. The five spark strategies are combined with swirl or no-swirl operation for a total of 10 ϕ-sweeps. A high-octane E30 fuel is used here, and intake heating is used to promote both lean combustion stability and end-gas autoignition. The best lean combustion stability is found for the ALL Three spark strategy, followed by the East-West and Central spark strategies, enabling stable mixed-mode spark-ignition combustion for ϕ down to 0.50 and 0.55, respectively. Here, operation without swirl provides the most stable combustion. High-speed imaging of ultra-lean operation without swirl at ϕ = 0.55 using the East-West spark strategy reveals that the transition from deflagration to end-gas autoignition frequently occurs within the view offered by the small piston-bowl window. These results encourage future optical investigations of fuel effects on this transition process, but a larger piston-bowl window is recommended.

Effects of spark plug configuration on combustion and emission characteristics of a LPG fuelled lean burn SI engine

Introduction of technological innovation in automotive engines in reducing pollution and increasing efficiency have been under contemplation. Gaseous fuels have proved to be a promising way to reduce emissions in Spark Ignition (SI) engines. In particular, LPG settled to be a favourable fuel for SI engines because of their higher hydrogen to carbon ratio, octane rating and lower emissions. Wide ignition limits and efficient combustion characteristics make LPG suitable for lean burn operation. But lean combustion technology has certain drawbacks like poor flame propagation, cyclic variations etc. Based on copious research it was found that location, types and number of spark plug significantly influence in reducing cyclic variations. In this work the influence of single and dual spark plugs of conventional and surface discharge electrode type were analysed. Dual surface discharge electrode spark plug enhanced the brake thermal efficiency and greatly reduced the cyclic variations. The experimental results show that rate of heat release and pressure rise was more and combustion duration was shortened in this configuration. On the emissions front, the NOx emission has increased whereas HC and CO emissions were reduced under lean condition.

ANN Modelling of Propane-Powered 4-Stroke Spark Ignition Engine

An ANN model was developed by the authors and tested against experimental data available for an engine as supplied in the manual by the manufacturers. The model was found to perform excellently well by showing similar trends of performance for this engine as well as other engines for which the necessary data was available. This model was then used to perform some parametric studies to improve the performance of an engine using LPG (mainly Propane C3H8) as a fuel. This paper presents discussion on some of the parameters that affect the engine’s thermal efficiency with suggestions to improve it. The effect of equivalence ratio, compression ratio and spark plug location at different speeds on the thermal efficiency have been studied. Based on the engine and the range of variables studied it was found that the best spark plug location was 0.395 for all equivalence ratios studied at CR = 9.

Effect of spark plug and fuel injector location on mixture stratification in a GDI engine - A CFD analysis

The mixture preparation in gasoline direct injection (GDI) engines operating at stratified condition plays an important role in deciding the combustion, performance and emission characteristics of the engine. In a wall-guided GDI engine, with a late fuel injection strategy, piston top surface is designed in such a way that the injected fuel is directed towards the spark plug to form a combustible mixture at the time of ignition. In addition, in these engines, location of spark-plug and fuel injector, fuel injection pressure and timing are also important to create a combustible mixture near the spark plug. Therefore, understanding the mixture formation under the influence of the location of spark plug and fuel injector is very essential for the optimization of the engine parameters. In this study, an attempt is made to understand the effect of spark plug and fuel injector location on the mixture preparation in a four-stroke, four-valve and wall-guided GDI engine operating under a stratified condition by using computational fluid dynamics (CFD) analysis. All the CFD simulations are carried out at an engine speed of 2000 rev/min., and compression ratio of 10.6, at an overall equivalence ratio (ER) of about 0.65. The fuel injection and spark timings are maintained at 605 and 710 CADs respectively. Finally, it is concluded that, combination of central spark plug and side fuel injector results in better combustion and performance.

FLOW ANALYSIS OF PISTON HEAD GEOMETRY FOR DIRECT INJECTION SPARK IGNITION ENGINE

Constructors of gasoline engines face higher and higher requirements as regards to ecological issues, and increase in engine efficiency at simultaneous decrease in fuel consumption. Satisfying these requirements is possible by the recognition of the phenomena occurred inside engine cylinder, the choice of suitable optimal parameters of fuel injection process, and the determination of geometrical shapes of the combustion chamber and piston head. The aim of this study is to simulate flow in Fuel Direct-Injection engine with different geometrical shapes of piston head. Designing piston head shapes was done by referring to existing motorcycle, Demak 200cc-single cylinder using SolidWork and ANSYS software. The parameter investigated are shallow and deep bowl design of piston head. In term of fuel distribution throughout the combustion chamber, engine model that has deeper bowl (Model 2) shows better fuel distribution than model of shallow bowl as it manages to direct the fuel injected towards the location of spark plug. Total kinetic energy of Model 2 is about 20% higher than Model 1. Therefore, engine with deeper bowl is chose as the best model between the two models as it can create a richer mixture around the spark plug

Influences of Ignition Timing, Spark Plug and Intake Port Locations on the Combustion Performance of a Simulated Rotary Engine

AbstractThe purpose of this paper is to study the flow field of the combustion chamber in a simulated rotary engine by using a computational approach. A dynamic mesh technique is employed to overcome the moving and shape varying computational domain inside the combustion chambers as the rotor is spinning. The key parameters include spark plug timing, leading side spark plug location and intake port location, which are used to investigate their influences on flow field and combustion performance of a rotary engine. It was discovered, with a dual spark plug configuration, that better flame propagation could be obtained through the change of ignition timing. In addition, to change the leading side spark plug location, it was also found that combustion efficiency is improved by shortening the distance from the top dead center (TDC) center line, which is consistent with available experimental results. This research also discovered that the intake port should be properly located in order to prevent pressure loss in the combustion chamber during the compression stroke.

Performance and Sensitivity analysis of Factors Affecting NOx Emissions from Hydrogen Fueled SI Engine

An Analysis of Variance (ANOVA) sensitivity analysis using suitable MATLAB code onthe factors affecting oxides of Nitrogen (NOx) emissions of a hydrogen powered 4-stroke,water-cooled spark-ignition engine was conducted in this work. This was done usingspecialized engine performance and emission simulation software. The parameters studiedwere the engine speed, air-fuel equivalence ratio, spark plug location in addition to some othercombustion parameters like combustion duration, heat loss besides some other usefulperformance parameters. It was found that NOx formation is minimum at peripheral sparklocation, slightly lean (PHI=0.9), and less advance timing is needed. Further, based onANOVA analysis, the combination of engine speed and spark location has more significance(effect based on P-value) compared with engine speed and equivalence ratio. The combinationof engine speed and ignition timing has more significance (effect based on P-value) comparedwith engine speed and equivalence ratio. Also found that NOx emissions behavior is moreclear at lean mixture (PHI = 0.7), central spark location (XSP = 0.5) and retarded ignitiontiming (IGN near zero).