Influences of a new glow plug shield on natural gas combustion characteristics in direct-injection engines

Fuel ◽  
2021 ◽  
Vol 294 ◽  
pp. 120401
Author(s):  
Kang Pan ◽  
James S. Wallace
Keyword(s):  
Natural Gas ◽  
Direct Injection ◽  
Combustion Characteristics ◽  
Gas Combustion ◽  
Direct Injection Engines ◽  
Glow Plug ◽  
Natural Gas Combustion

Large-eddy simulation of direct injection natural gas combustion in a heavy-duty truck engine using modified conditional moment closure model with low-dimensional manifold method

2018 ◽  
Vol 21 (5) ◽  
pp. 824-837 ◽  
Author(s):  
Jian Huang ◽  
Gordon McTaggart-Cowan ◽  
Sandeep Munshi
Keyword(s):  
Natural Gas ◽  
Direct Injection ◽  
Moment Closure ◽  
Dimensional Manifold ◽  
Conditional Moment ◽  
Gas Combustion ◽  
Conditional Moment Closure ◽  
Natural Gas Combustion ◽  
Low Dimensional ◽  
Low Dimensional Manifold

This article describes the application of a modified first-order conditional moment closure model used in conjunction with the trajectory-generated low-dimensional manifold method in large-eddy simulation of pilot ignited high-pressure direct injection natural gas combustion in a heavy-duty diesel engine. The article starts with a review of the intrinsic low-dimensional manifold method for reducing detailed chemistry and various formulations for the construction of such manifolds. It is followed by a brief review of the conditional moment closure method for modelling the interaction between turbulence and combustion chemistry. The high computational cost associated with the direct implementation of the basic conditional moment closure model was discussed. The article then describes the formulation of a modified approach to solve the conditional moment closure equation, whose reaction source terms for the conditional mass fractions for species were obtained by projecting the turbulent perturbation onto the reaction manifold. The main model assumptions were explained and the resulting limitations were discussed. A numerical experiment was conducted to examine the validity the model assumptions. The model was then implemented in a combustion computational fluid dynamics solver developed on an open-source computational fluid dynamics platform. Non-reactive jet simulations were first conducted and the results were compared to the experimental measurement from a high-pressure visualization chamber to verify that the jet penetration under engine relevant conditions was correctly predicted. The model was then used to simulate natural gas combustion in a heavy-duty diesel engine equipped with a high-pressure direct injection system. The simulation results were compared with the experimental measurement from a research engine to verify the accuracy of the model for both the combustion rate and engine-out emissions.

Ignition by Shielded Glow Plug in Natural Gas Fueled Direct Injection Engines

2011 ◽  
Author(s):  
Mark Fabbroni ◽  
James S. Wallace
Keyword(s):  
Diesel Engine ◽  
Natural Gas ◽  
Combustion Chamber ◽  
Heated Surface ◽  
Direct Injection ◽  
Cylinder Wall ◽  
Fuel Utilization ◽  
Direct Injection Engines ◽  
Glow Plug ◽  
Gas Jets

Injected natural gas requires some form of ignition assist in order to ignite in the time available in a diesel engine combustion chamber. A glow plug — a heated surface — is one form of ignition assist. Ignition by glow plug results in a single site of ignition from which the flame must propagate to other jets in the ignition pattern. The goal of this work was to determine what factors affect how the flame propagates from this initial ignition site to the remaining unburned mixture. The combustion of natural gas jets under diesel engine conditions was studied over a range of temperatures with a glow plug shield using a CFR engine as a rapid compression device. The results showed that of all the factors considered it is the inter-related geometries of the injection pattern, combustion chamber, and glow plug shield that are most dominant in controlling combustion rates and fuel utilization, because those factors determine the distribution of fuel in the combustion chamber. Ignition of adjacent gas jets requires a flammable path between jets, which is achieved: 1) through mixing between the entrainment regions of adjacent jets and 2) through mixing along the cylinder wall of adjacent jets that are spreading along the wall. Ignition by either of both of these pathways can provide high fuel utilization and combustion rates and low combustion variability. Autoignition of an adjacent jet due to heat release from ignition of the first jet was not observed in these experiments with two jets.

Parametric study of pilot-ignited direct-injection natural gas combustion in an optically accessible heavy-duty engine

2019 ◽  
Vol 21 (3) ◽  
pp. 497-513 ◽  
Author(s):  
Jeremy Rochussen ◽  
Gordon McTaggart-Cowan ◽  
Patrick Kirchen
Keyword(s):  
Natural Gas ◽  
Heat Release ◽  
Internal Combustion Engines ◽  
Direct Injection ◽  
Injection Pressure ◽  
Gas Combustion ◽  
Gas Ignition ◽  
Partially Premixed ◽  
Natural Gas Combustion ◽  
Combustion Processes

Natural gas is an attractive fuel for internal combustion engines in light of its potential for reduced greenhouse gas and particulate emissions, and significant reserves. To facilitate natural gas use in compression ignition engines, pilot-ignited direct-injection natural gas combustion uses a small pilot injection of diesel to ignite a more significant direct injection of natural gas. Compared to modern diesel combustion, this strategy is a promising technology for the reduction of CO2 emissions while retaining diesel-like efficiency without a significant CH4 emission penalty. To further develop this technology, investigation of in-cylinder combustion processes is needed to identify the primary fuel conversion processes. The objective of this work was to provide a framework of conceptual understanding by identifying key processes in a typical pilot-ignited direct-injection natural gas combustion event and characterizing their sensitivity to fuel injection parameters. A parametric sweep of injection pressure, natural gas injection duration, and relative timing of the diesel pilot and natural gas injections was performed in an optically accessible 2 L single-cylinder engine. Combined heat release rate and OH*-chemiluminescence reaction zone analysis was used to demarcate the transition from ignition reactions to primary natural gas heat release. Five distinct combustion processes were identified: (1) pilot auto-ignition; (2) natural gas ignition; (3) rapid, distributed partially premixed natural gas combustion; (4) non-premixed combustion; and (5) late-cycle oxidation. While natural gas ignition was found to be insensitive to injection pressure, it was strongly affected by the time between pilot and natural gas injections. Reducing the relative injection timing from +8° to −6° resulted in the primary natural gas heat release transitioning from non-premixed, to distributed partially premixed, to stratified premixed flame propagation as a result of increasing natural gas premixing. The presented measurements and analysis serve to refine an initial conceptual model of the combustion process and lay the groundwork for future, more focused studies of pilot-ignited, direct-injection natural gas combustion.

Flame Propagation in Natural Gas Fueled Direct Injection Engines

2010 ◽  
Author(s):  
Mark Fabbroni ◽  
James S. Wallace
Keyword(s):  
Diesel Engine ◽  
Natural Gas ◽  
Combustion Chamber ◽  
Heated Surface ◽  
Direct Injection ◽  
Direct Injection Engines ◽  
Glow Plug ◽  
Compression Device ◽  
Engine Combustion ◽  
Ignition Site

Injected natural gas requires some form of ignition assist in order to ignite in the time available in a diesel engine combustion chamber. A glow plug — a heated surface — is one form of ignition assist. Ignition by glow plug results in a single site of ignition from which the flame must propagate to other jets in the injection pattern. The goal of this work was to determine what factors affect how the flame propagates from this initial ignition site to the remaining unburned mixture site. The combustion of natural gas jets under diesel engine conditions was studied over a range to temperatures, pressures with and without a glow plug shield using a CFR engine as a rapid compression device. The results showed that of all the factors considered it is the geometry of the injection pattern, combustion chamber and glow plug shield that are most dominant in controlling combustion rates and fuel utilization.

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