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Technical Paper

High-Fidelity Numerical Modeling of Spark Plug Erosion

2019-04-02
2019-01-0215
Spark plug erosion is critical in determining the overall efficiency of a spark ignition engine. Over its lifetime, a spark plug is subject to millions of firings. Each spark event results in material erosion due to several mechanisms such as melting, vaporization, sputtering and oxidation. With electrode wear, the inter-electrode spacing increases and a larger voltage difference is required to initiate the spark. The probability of engine misfires also increases with electrode erosion. Once a critical gap is reached, the energy in the ignition coil is not enough to cause a spark breakdown, and the spark plug must be replaced. Due to the long relevant time scales over which erosion occurs, and the difficulty of analyzing the spark plug environment during operation, determining spark plug lifetime typically requires extensive field testing. A high fidelity commercial thermal plasma solver, VizSpark is used simulate electrode erosion due to spark events.
Journal Article

Mixture Formation in Direct Injection Hydrogen Engines: CFD and Optical Analysis of Single- and Multi-Hole Nozzles

2011-09-11
2011-24-0096
This paper describes the validation of a CFD code for mixture preparation in a direct injection hydrogen-fueled engine. The cylinder geometry is typical of passenger-car sized spark-ignited engines, with a centrally located injector. A single-hole and a 13-hole nozzle are used at about 100 bar and 25 bar injection pressure. Numerical results from the commercial code Fluent (v6.3.35) are compared to measurements in an optically accessible engine. Quantitative planar laser-induced fluorescence provides phase-locked images of the fuel mole-fraction, while single-cycle visualization of the early jet penetration is achieved by a high-speed schlieren technique. The characteristics of the computational grids are discussed, especially for the near-nozzle region, where the jets are under-expanded. Simulation of injection from the single-hole nozzle yields good agreement between numerical and optical results in terms of jet penetration and overall evolution.
Technical Paper

Multi-dimensional Modeling of Non-equilibrium Plasma for Automotive Applications

2018-04-03
2018-01-0198
While spark-ignition (SI) engine technology is aggressively moving towards challenging (dilute and boosted) combustion regimes, advanced ignition technologies generating non-equilibrium types of plasma are being considered by the automotive industry as a potential replacement for the conventional spark-plug technology. However, there are currently no models that can describe the low-temperature plasma (LTP) ignition process in computational fluid dynamics (CFD) codes that are typically used in the multi-dimensional engine modeling community. A key question for the engine modelers that are trying to describe the non-equilibrium ignition physics concerns the plasma characteristics. A key challenge is also represented by the plasma formation timescale (nanoseconds) that can hardly be resolved within a full engine cycle simulation.
Technical Paper

Numerical and Optical Evolution of Gaseous Jets in Direct Injection Hydrogen Engines

2011-04-12
2011-01-0675
This paper performs a parametric analysis of the influence of numerical grid resolution and turbulence model on jet penetration and mixture formation in a DI-H2 ICE. The cylinder geometry is typical of passenger-car sized spark-ignited engines, with a centrally located single-hole injector nozzle. The simulation includes the intake and exhaust port geometry, in order to account for the actual flow field within the cylinder when injection of hydrogen starts. A reduced geometry is then used to focus on the mixture formation process. The numerically predicted hydrogen mole-fraction fields are compared to experimental data from quantitative laser-based imaging in a corresponding optically accessible engine. In general, the results show that with proper mesh and turbulence settings, remarkable agreement between numerical and experimental data in terms of fuel jet evolution and mixture formation can be achieved.
Technical Paper

Predictive Breakdown Modelling for Spark Plug Design

2020-04-14
2020-01-0781
The lifetime of a spark plug is often limited by the ability of a spark plug to generate spark as the plug erodes and deforms. Many parameters including the spark plug gap distance, geometric features such as corners, and the gas itself influence the breakdown event. In order to asses the viability of a spark plug design, the most ideal solution is to perform full fidelity plasma simulations for each design configuration. However, these simulations are extremely expensive and take a long time to give meaningful results. Thus, there is a need for a fast spark plug breakdown model which can predict the breakdown effectiveness for a large number of spark plug design configurations over a much shorter period of time, narrowing the range of spark plug design which can then be studied using a higher fidelity plasma simulation tool. The objective of this work is to describe a fast, predictive breakdown model to simulate the effectiveness of different spark plug configurations.
Technical Paper

Simulation of Spark-Initiated Combustion

2019-04-02
2019-01-0226
There has been an increased interest in understanding the initial stages of flame kernel formation in internal combustion engines as it offers a potential way of improving their thermal efficiency. For spark-ignited engines, the dynamics that govern the initial spark and its transition into a flame kernel play an important role in determining the overall engine efficiency. In this regard, this paper presents a computational model developed to simulate a spark discharge formed in a premixed fuel air mixture. Additionally, by simultaneously modeling the reactive fluid dynamics that governs combustion with the electromagnetics that governs the spark, the overall objective of this paper is to consistently simulate spark-initiated combustion in a premixed fuel-air mixture. Two different fuel-oxidizer mixtures are considered in this study, hydrogen-oxygen and methane-oxygen. Key mechanisms via which the spark channel ignites the mixture are identified and studied in detail.
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