Performance and emissions of a methane-fueled spark-ignition engine under consideration of its cyclic variability by using a computational fluid dynamics code

Fuel ◽  
2019 ◽  
Vol 258 ◽  
pp. 116154 ◽  
Author(s):  
G.M. Kosmadakis ◽  
D.C. Rakopoulos ◽  
C.D. Rakopoulos
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Spark Ignition ◽  
Spark Ignition Engine ◽  
Cyclic Variability ◽  
Performance And Emissions

Modeling laminar burning velocity of gasoline using an energy fraction-based mixing rule approach

2018 ◽  
Vol 233 (5) ◽  
pp. 1245-1258 ◽  
Author(s):  
Joohan Kim ◽  
Kyoungdoug Min
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Burning Velocity ◽  
Direct Injection ◽  
Velocity Model ◽  
Spark Ignition ◽  
Spark Ignition Engine ◽  
Mixing Rule ◽  
Laminar Burning Velocity ◽  
Direct Injection Spark Ignition

To determine an optimum combustion chamber design and engine operating strategies, computational fluid dynamics simulations of direct-injection spark-ignition engines have become an indispensable step in the powertrain development process. The laminar burning velocity of gasoline is known as an essential input parameter for combustion simulations. In this study, a new methodology for modeling the laminar burning velocity of gasoline for direct-injection spark-ignition engine simulations is proposed. Considering the gasoline as a complex mixture of hydrocarbon fuel, three hydrocarbons, iso-octane, n-heptane, and toluene were incorporated as surrogate fuel components to represent gasoline with distinct aromatic laminar flame characteristics compared to alkane. A mixing rule, based on energy fractions, was adopted to consider the compositional variation of gasoline. The laminar burning velocities of iso-octane, n-heptane, and toluene were calculated under wide thermo-chemical conditions in conjunction with detailed chemical reaction kinetics in the premixed flame simulation. Finally, a set of laminar burning velocity model equations was derived by curve-fitting the flame simulation results of each hydrocarbon component in consideration of the effect of temperature, pressure, and diluent. The laminar burning velocity model was validated against the measurement data of gasoline’s laminar burning velocity found in the literature, and was applied to the computational fluid dynamics simulation of a direct-injection spark-ignition engine under the various operating conditions to explore the prediction capability.

Development of a zero-dimensional turbulence model for a spark ignition engine

2018 ◽  
Vol 20 (4) ◽  
pp. 441-451 ◽  
Author(s):  
Namho Kim ◽  
Insuk Ko ◽  
Kyoungdoug Min
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Kinetic Energy ◽  
Three Dimensional ◽  
Spark Ignition ◽  
Spark Ignition Engine ◽  
Length Scale ◽  
One Dimensional ◽  
Simulation Results ◽  
Dimensional Simulation

The necessity for the use of one-dimensional simulation is growing because cost and time required for hardware optimization and optimal calibration of engines based on experiment are increasing dramatically as engines are equipped with growing numbers of technologies. For one-dimensional simulation results to be more reliable, the accuracy and applicability of the combustion model of a one-dimensional simulation tool must be guaranteed. Because the combustion process in a spark ignition engine is driven by the turbulence, many of existing models focus on the prediction of mean turbulence intensity. Although many successes in the previous models can be found, the previous models contain a large number of adjustable constants or require information supplemented from three-dimensional computational fluid dynamics simulation results. For improved applicability of a model, the number of adjustable constants and inputs to the model must be kept as small as possible. Thus, in this study, a new zero-dimensional (0D) turbulence model was proposed that requires information on the basic characteristics of the engine geometry and has only one adjustable constant. The model was developed based on the energy cascade model with additional consideration of following aspects: loss of kinetic energy during the intake stroke, the effect of piston motion during the compression and the expansion stroke, modifications to correlations for integral length scale, geometric length scale, and production rate of turbulent kinetic energy. An adjustable constant to consider engine design which determines tumble strength was also introduced. The comparison of the simulation results with those of three-dimensional computational fluid dynamics confirmed that the developed model can predict the mean turbulence intensity without case-dependent adjustment of the model constant.

In-Cylinder Flow Computational Fluid Dynamics Analysis of a Four-Valve Spark Ignition Engine: Comparison Between Steady and Dynamic Tests

2010 ◽  
Vol 132 (5) ◽  
Author(s):  
Damian E. Ramajo ◽  
Norberto M. Nigro
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Flow Field ◽  
Steady Flow ◽  
Spark Ignition ◽  
Spark Ignition Engine ◽  
Mean Flow ◽  
Dynamic Simulations ◽  
Computational Fluid Dynamics Analysis ◽  
Cylinder Flow

Numerical and experimental techniques were applied in order to study the in-cylinder flow field in a commercial four-valve per cylinder spark ignition engine. Investigation was aimed at analyzing the generation and evolution of tumble-vortex structures during the intake and compression strokes, and the capacity of this engine to promote turbulence enhancement during tumble degradation at the end of the compression stroke. For these purposes, three different approaches were analyzed. First, steady flow rig tests were experimentally carried out, and then reproduced by computational fluid dynamics (CFD). Once CFD was assessed, cold dynamic simulations of the full engine cycle were performed for several engine speeds (1500 rpm, 3000 rpm, and 4500 rpm). Steady and cold dynamic results were compared in order to assess the feasibility of the former to quantify the in-cylinder flow. After that, combustion was incorporated by means of a homogeneous heat source, and dynamic boundary conditions were introduced in order to approach real engine conditions. The combustion model estimates the burning rate as a function of some averaged in-cylinder flow variables (temperature, pressure, turbulent intensity, and piston position). Results were employed to characterize the in-cylinder flow field of the engine and to establish similarities and differences between the three performed tests that are currently used to estimate the engine mean flow characteristics (steady flow rig, and cold and real dynamic simulations).

Investigation of Multistage Combustion Inside a Heavy-Duty Natural-Gas Spark-Ignition Engine Using Three-Dimensional Computational Fluid Dynamics Simulations and the Wiebe-Function Combustion Model

2020 ◽  
Vol 142 (10) ◽  
Author(s):  
Jinlong Liu ◽  
Cosmin E. Dumitrescu
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Natural Gas ◽  
Burning Rate ◽  
Three Dimensional ◽  
Spark Ignition ◽  
Spark Ignition Engine ◽  
Heavy Duty ◽  
Piston Speed ◽  
Wiebe Function

Abstract The conversion of existing heavy-duty diesel engines to lean natural-gas (NG) spark ignition can be achieved by replacing the diesel injector with a spark plug and fumigating the NG into the intake manifold. While the original fast-burn diesel chamber will offset the lower NG flame speed, it will result in a two-stage combustion process (a stage inside and another outside the bowl). However, experimental data at more advanced spark timing, equivalence ratio of 0.8, and mean piston speed of 6.5 m/s suggested an additional combustion stage (i.e., three combustion stages). A three-dimensional (3D) computational fluid dynamics (CFD) simulation and a zero-dimensional triple Wiebe-function model were used to better understand the phenomena. While 78% fuel burned inside the bowl, burning rate reduced significantly when the flame approached the squish entrance and the bowl bottom. Moreover, the triple Wiebe-function indicated that the burn inside the squish was also divided into two separate combustion stages, due to the particularities of in-cylinder flow before and after top dead center. The first stage was fast and took place inside the compression stroke. The second took place in the expansion stroke and produced a short-lived increase in the burning rate, probably due to the increasing squish height during the expansion stroke and the increased combustion-induced turbulence, hence the third heat-release peak. Overall, these findings support the need for further investigations of combustion characteristics in such converted engines, to benefit their efficiency and emissions.

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