Spark Ignition of SPP Injector Under Sub-Atmospheric Conditions

Abstract The sub-atmospheric ignition performance of an SPP (Stratified Partially Premixed) injector and combustor is investigated experimentally on the high-altitude test facility. In order to explore the influence of sub-atmospheric pressure on reignition performance and flame propagation mode, experiments are conducted under different pressures ranging from 19 kPa to 101 kPa. The inlet temperature and pressure drop of the injector (ΔPsw/P3t) are kept constant at 303 K and 3% respectively. The transparent quartz window mounted on the sidewall of the model combustor provides optical access of flame signals. Ignition fuel-air ratio (FAR) under different inlet pressures are experimentally acquired. The spark ignition processes, including the formation of flame kernel, the flame development and stabilization are recorded by a high-speed camera at a rate of 5kHz. Experimental results indicate that the minimum ignition FAR grows rapidly as the inlet air pressure decreases. An algorithm is developed to track the trajectory of flame kernels within 25ms following the spark during its breakup and motion processes. Results show that the calculated trajectory provides a clear description of the flame evolution process. Under different inlet air pressures, the propagation trajectories of flame kernels share similarities in initial phase. It is pivotal for a successful ignition that the initial flame kernel keeps enough intensity and moves into CTRZ (Center-Toroidal Recirculation Zone) along radial direction. Finally, the time-averaged non-reacting flow field under inlet pressure of 54kPa and fuel mass flow of 8kg/h is simulated. The effects of flow structure and fuel spatial distribution on kernel propagation and flame evolution are analyzed.

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A New Micro Turbo-Machinery Test Facility

Volume 5: Industrial and Cogeneration; Microturbines and Small Turbomachinery; Oil and Gas Applications; Wind Turbine Technology ◽

10.1115/gt2010-23257 ◽

2010 ◽

Author(s):

Chen Xia ◽

Guoping Huang ◽

Jie Chen

Keyword(s):

Mass Flow ◽

High Speed ◽

Modular Design ◽

Thermal Protection ◽

Dynamic Pressure ◽

Pressure Sensors ◽

Test Facility ◽

Inlet Temperature ◽

Test Bed ◽

Turbo Machinery

The design and construction of a new test facility of micro turbo-machinery are presented for micro centrifugal compressors and radial turbines. The bed can be used for the full speed compressor test and the long duration hot turbine test. In order to adjust the testing condition rapidly, all the regulations of operating state are completed automatically by the control system. The test bed can be used for testing impeller performance with a series of diameter from 55 to 180 mm as a result of the modular design. A thermal protection system is designed to avoid the heat distortion caused by the high inlet temperature of turbine which may exceeds 1100K and provide a proper experimental environment for the electronic components. A photoelectric torque transducer with an accuracy of 1% is designed to measure the torque of a rigid shaft at a high speed over 120000rpm, and the maximum shaft torque is 7.7 N·m. The pressure and temperature are measured by pressure probes and thermocouples. The dynamic pressure signal of the centrifugal compressor is monitored by dynamic pressure sensors. The V-cone pressure-difference mass-flow meters are used for measuring mass-flow. The maximum rotating speed is 125000rpm, and the mass flow adjusted by the electric control valves varies from 0.1 to 1.0 kg/sec. The maximum inlet total temperature of the turbine is 1180K.

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Investigation of the Effect of Electrode Surface Roughness on Spark Ignition

10.31224/osf.io/ne8fv ◽

2018 ◽

Author(s):

Mohammadrasool Morovatiyan ◽

Martia Shahsavan ◽

Mengyan Shen ◽

John Hunter Mack

Keyword(s):

Surface Roughness ◽

Electrode Surface ◽

High Speed ◽

Fuel Efficiency ◽

Spark Ignition ◽

Ignition Process ◽

Flammability Limit ◽

Lean Burn ◽

Flame Kernel ◽

Spark Plug

Lean-burn engines are important due to their ability to reduce emissions, increase fuel efficiency, and mitigate engine knock. In this study, the surface roughness of spark plug electrodes is investigated as a potential avenue to extend the lean flammability limit of natural gas. A nano-/micro-morphology modification is applied on surface of the spark plug electrode to increase its surface roughness. High-speed Z-type Schlieren visualization is used to investigate the effect of the electrode surface roughness on the spark ignition process in a premixed methane-air charge at different lean equivalence ratios. In order to observe the onset of ignition and flame kernel behavior, experiments were conducted in an optically accessible constant volume combustion chamber at ambient pressures and temperatures. The results indicate that the lean flammability limit of spark-ignited methane can be lowered by modulating the surface roughness of the spark plug electrode.

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The Effects of Initial Flame Kernel Conditions on Flame Development in SI Engine

10.4271/912402 ◽

1991 ◽

Cited By ~ 40

Author(s):

Yvan Bianco ◽

Wai K. Cheng ◽

John B. Heywood

Keyword(s):

Si Engine ◽

Flame Kernel ◽

Flame Development ◽

Initial Flame

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A Numerical Study of Concurrent Flame Propagation Over Methanol Pool Surface

Journal of Heat Transfer ◽

10.1115/1.4005111 ◽

2012 ◽

Vol 134 (4) ◽

Author(s):

Seik Mansoor Ali ◽

Vasudevan Raghavan ◽

K. Velusamy ◽

Shaligram Tiwari

Keyword(s):

Flame Spread ◽

Numerical Study ◽

Leading Edge ◽

Reacting Flow ◽

Atmospheric Conditions ◽

Air Velocity ◽

Two Phase ◽

Spread Velocity ◽

Pool Surface ◽

Initial Flame

Concurrent flame spread over methanol pool surface under atmospheric conditions and normal gravity has been numerically investigated using a transient, two-phase, reacting flow model. The average flame spread velocities for different concurrent air velocities predicted using the model are quite close to the experimental data available in the literature. As the air velocity is increased, the fuel consumption rate increases and aids in faster flame spread process. The flame initially anchors around the leading edge of the pool and the flame tip spreads over the pool surface. The rate of propagation of flame tip along the surface is seen to be steady without fluctuations. The flame spread velocity is found to be nonuniform as the flame spreads along the pool surface. The flame spread velocity is seen to be higher initially. It then decreases up to a point when the flame has propagated to around 40% to 50% of the pool length. At this position, a secondary flame anchoring point is observed, which propagates toward the trailing edge of the pool. As a result, there is an increasing trend observed in the flame spread velocity. As the air velocity is increased, the initial flame anchoring point moves downstream of the leading edge of the fuel pool. The variations of interface quantities depend on the initial flame anchoring location and the attainment of thermodynamic equilibrium between the liquid- and gas-phases.

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Ignition Probability and Lean Ignition Behaviour of a Swirled Premixed Bluff Body Stabilised Annular Combustor

Volume 4B: Combustion, Fuels, and Emissions ◽

10.1115/gt2020-15434 ◽

2020 ◽

Author(s):

Roberto Ciardiello ◽

Rohit S. Pathania ◽

Patton M. Allison ◽

Pedro M. de Oliveira ◽

Epaminondas Mastorakos

Keyword(s):

High Speed ◽

Bluff Body ◽

Recirculation Zone ◽

Ignition Process ◽

High Speed Imaging ◽

Ignition Probability ◽

Flame Kernel ◽

Annular Combustor ◽

Initial Flame ◽

Limiting Condition

Abstract An experimental investigation was performed in a premixed annular combustor equipped with multiple swirl, bluff body burners to assess the ignition probability and to provide insights into the mechanisms of failure and of successful propagation. The experiments are done at conditions that are close to the lean blow-off limit (LBO) and hence the ignition is difficult and close to the limiting condition when ignition is not possible. Two configurations were employed, with 12 and 18 burners, the mixture velocity was varied between 10 and 30 m/s, and the equivalence ratio (ϕ) between 0.58 and 0.68. Ignition was initiated by a sequence of sparks (2 mm gap, 10 sparks of 10 ms each) and “ignition” is defined as successful ignition of the whole annular combustor. The mechanism of success and failure of the ignition process and the flame propagation patterns were investigated via high-speed imaging (10 kHz) of OH* chemiluminescence. The lean ignition limits were evaluated and compared to the lean blow-off limits, finding the 12-burner configuration is more stable than the 18-burner. It was found that failure is linked to the trapping of the initial flame kernel inside the inner recirculation zone (IRZ) of a single burner adjacent to the spark, followed by localised quenching on the bluff body probably due to heat losses. In contrast, for a successful ignition, it was necessary for the flame kernel to propagate to the adjacent burner or for a flame pocket to be convected downstream in the chamber to grow and start propagating upwards. Finally, the ignition probability (Pign) was obtained for different spark locations. It was found that sparking inside the recirculation zone resulted in Pign ∼ 0 for most conditions, while Pign increased moving the spark away from the bluff-body or placing it between two burners and peaked to Pign ∼ 1 when the spark was located downstream in the combustion chamber, where the velocities are lower and the turbulence less intense. The results provide information on the most favourable conditions for achieving ignition in a complex multi-burner geometry and could help the design and optimisation of realistic gas turbine combustors.

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An Experimental and Simulation Study of Early Flame Development in a Homogeneous-charge Spark-Ignition Engine

Oil & Gas Science and Technology – Revue d’IFP Energies nouvelles ◽

10.2516/ogst/2017028 ◽

2017 ◽

Vol 72 (5) ◽

pp. 32

Author(s):

Y. Shekhawat ◽

D.C. Haworth ◽

A. d'Adamo ◽

F. Berni ◽

S. Fontanesi ◽

...

Keyword(s):

High Speed ◽

Spatial Scales ◽

Model Development ◽

Optical Diagnostics ◽

Spark Ignition ◽

Spark Ignition Engine ◽

Eddy Simulation ◽

Computational Mesh ◽

Flame Development ◽

The Times

An integrated experimental and Large-Eddy Simulation (LES) study is presented for homogeneous premixed combustion in a spark-ignition engine. The engine is a single-cylinder two-valve optical research engine with transparent liner and piston: the Transparent Combustion Chamber (TCC) engine. This is a relatively simple, open engine configuration that can be used for LES model development and validation by other research groups. Pressure-based combustion analysis, optical diagnostics and LES have been combined to generate new physical insight into the early stages of combustion. The emphasis has been on developing strategies for making quantitative comparisons between high-speed/high-resolution optical diagnostics and LES using common metrics for both the experiments and the simulations, and focusing on the important early flame development period. Results from two different LES turbulent combustion models are presented, using the same numerical methods and computational mesh. Both models yield Cycle-to-Cycle Variations (CCV) in combustion that are higher than what is observed in the experiments. The results reveal strengths and limitations of the experimental diagnostics and the LES models, and suggest directions for future diagnostic and simulation efforts. In particular, it has been observed that flame development between the times corresponding to the laminar-to-turbulent transition and 1% mass-burned fraction are especially important in establishing the subsequent combustion event for each cycle. This suggests a range of temporal and spatial scales over which future experimental and simulation efforts should focus.

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Investigation of the Effect of Electrode Surface Roughness on Spark Ignition

Volume 1: Large Bore Engines; Fuels; Advanced Combustion ◽

10.1115/icef2018-9691 ◽

2018 ◽

Cited By ~ 1

Author(s):

Mohammadrasool Morovatiyan ◽

Martia Shahsavan ◽

Mengyan Shen ◽

J. Hunter Mack

Keyword(s):

Surface Roughness ◽

Electrode Surface ◽

High Speed ◽

Fuel Efficiency ◽

Spark Ignition ◽

Ignition Process ◽

Flammability Limit ◽

Lean Burn ◽

Flame Kernel ◽

Spark Plug

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Impacts of Spark Discharge Current and Duration on Flame Development of Lean Mixtures Under Flow Conditions

Volume 1: Large Bore Engines; Fuels; Advanced Combustion ◽

10.1115/icef2018-9771 ◽

2018 ◽

Cited By ~ 3

Author(s):

Zhenyi Yang ◽

Xiao Yu ◽

Shui Yu ◽

Jianming Chen ◽

Guangyun Chen ◽

...

Keyword(s):

Flame Propagation ◽

Discharge Current ◽

Propagation Speed ◽

Spark Ignition ◽

Spark Discharge ◽

Current Level ◽

Ignition Process ◽

Flame Kernel ◽

Flame Development ◽

Discharge Duration

Lean or diluted combustion has been considered as an effective strategy to improve the thermal efficiency of spark ignition engines. Under lean or diluted conditions, the combustion speed is reduced by the diluting gas. In order to speed up the combustion, in-cylinder flow is intentionally enhanced to promote the flame propagation. However, it is observed that the flow may make the spark ignition process more challenging due to the shortened discharge duration, the frequent re-strikes of spark plasma and the more complicated interactions between the flow and the flame. In this research, the effects of spark discharge current level and discharge duration on flame kernel development and flame propagation of lean methane air mixture are investigated under flow velocity of about 25 m/s and background pressure of 4 bar abs in an optical combustion chamber. A dual coil ignition system and an in-house developed current management module are used to create different discharge current levels. The average discharge current levels range from 55 mA, 190 mA, up to 250 mA. Detached flame kernel is observed under some test conditions. The flame propagation speed with the detached flame is generally slower than the flame developed from a flame kernel attached to the spark plug. The flame detachment is related to both the discharge current level and the discharge duration. When the discharge current level is high at 250 mA, the detached flame is observed at shorter discharge duration of 0.8 ms, while when the discharge current is low at 190 mA, detached flame can happen at longer discharge duration of 1.3 ms. Various discharge current and discharge durations are adopted to initiate the combustion in a single-cylinder engine operating with lean gasoline air mixture. It is shown from the results that a higher discharge current level and longer discharge duration are beneficial for controlling the combustion phasing and improving the operation stability of the engine.

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A semi-empirical laminar-to-turbulent flame transition model coupled with G equation for early flame kernel development and combustion in spark-ignition engines

International Journal of Engine Research ◽

10.1177/1468087419864748 ◽

2019 ◽

pp. 146808741986474 ◽

Cited By ~ 1

Author(s):

Seunghwan Keum ◽

Guangfei Zhu ◽

Ronald Grover ◽

Wei Zeng ◽

Christopher Rutland ◽

...

Keyword(s):

Turbulent Flame ◽

Transition Process ◽

Spark Ignition ◽

Transition Function ◽

Spark Ignition Engine ◽

Navier Stokes ◽

Flame Kernel ◽

Eddy Simulation ◽

Flame Development ◽

Semi Empirical

It has been reported that early combustion in a spark-ignition engine determines the subsequent combustion. Also, the early combustion has a very strong correlation with cycle-to-cycle variability, which limits engine operating range. As such, accurate modeling of the early flame development is very important in accurate simulation of spark-ignition engine combustion. During the early flame development, the flame kernel, initiated by spark, grows initially at laminar flame speed. As the kernel grows, the flame surface wrinkles due to surface instability and interacts with the flow turbulence as the flame transitions from laminar to turbulent flame. In this study, a semi-empirical model is proposed to simulate the laminar-to-turbulent flame transition process during early spark-ignition combustion. A hyperbolic tangent function was used to emulate the laminar-to-turbulent flame speed transition process. The proposed transition function was evaluated during early flame kernel development for both Reynolds-averaged Navier–Stokes and large eddy simulation models against combustion analysis data from high-speed optical particle image velocimetry. Difference in Reynolds-averaged Navier–Stokes and large eddy simulation transition function was analyzed and discussed.

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