Characterizing Two-Stage Combustion Process in a Natural Gas Spark Ignition Engine Based on Multi-Wiebe Function Model

2020 ◽  
Vol 142 (10) ◽  
Author(s):  
Jinlong Liu ◽  
Chris Ulishney ◽  
Cosmin Emil Dumitrescu
Keyword(s):  
Natural Gas ◽  
Energy Release ◽  
Combustion Process ◽  
Spark Ignition ◽  
Spark Ignition Engine ◽  
Function Model ◽  
Two Stage ◽  
Long Tail ◽  
Stage Combustion ◽  
Wiebe Function

Abstract The Wiebe function is a simple and cost-effective analytical approach to approximate the burn rates in internal combustion (IC) engines. Previous studies indicated that a double-Wiebe function model can better describe the two-stage combustion process inside diesel engines retrofitted to natural gas (NG) spark ignition (SI) compared with a single-Wiebe function. Specifically, the two Wiebe functions are associated with the bowl burn and the squish burn. However, the long tail in the energy release at the end of combustion produces some differences between experiment and model, which can be attributed to the complexity of the late oxidation process inside the post-flame zone and the incomplete combustion of the unburned mixture flowing out from engine crevices. To improve the matching between the model and experimental data, this paper investigated the effect of adding a third Wiebe function just to describe the long tail in the energy release at the end of combustion. The results indicated that such a methodology greatly improved the fitting accuracy in terms of phasing and magnitude of the heat release rate in each combustion stage.

Improved Thermodynamic Model for Lean Natural Gas Spark Ignition in a Diesel Engine Using a Triple Wiebe Function

2019 ◽  
Vol 142 (6) ◽  
Author(s):  
Jinlong Liu ◽  
Cosmin Emil Dumitrescu
Keyword(s):  
Natural Gas ◽  
Diesel Engines ◽  
Mass Fraction ◽  
Internal Combustion Engines ◽  
Combustion Process ◽  
Spark Ignition ◽  
High Energy ◽  
Multi Stage ◽  
Stage Combustion ◽  
Wiebe Function

Abstract The use of natural gas (NG) in heavy-duty internal combustion engines can reduce the dependence on petroleum fuels and greenhouse gas emissions. Diesel engines can convert to NG spark ignition (SI) by installing a high-energy ignition system and a gas injector. The diesel combustion chamber affects the flow inside the cylinder, so some existing SI combustion models will not accurately describe the operation of converted diesels. For example, the single Wiebe function has difficulties in correctly describing the mass fraction burn (MFB) throughout the combustion process. This study used experiments from a 2L single-cylinder research engine converted to port fuel injection NG SI and operated with methane at 1300 rpm and equivalence ratio 0.8 (6.2 bars IMEP) to compare the standard Wiebe function with a triple Wiebe function. Results indicated that lean-burn engine operation at an advanced spark timing produced three peaks in the heat release rate, suggesting a multi-stage combustion process. A “best goodness-of-fit” approach determined the values of the key parameters in the zero-dimensional Wiebe function model. The triple Wiebe function described the mass fraction burn and combustion phasing more accurately compared with the single Wiebe function. Moreover, it provided the duration and phasing of each individual burning stage that can then characterize the combustion in such converted diesel engines. This suggests that a multiple Wiebe function combustion model would effectively assist in analyzing such a multi-stage combustion process, which is important for engine optimization and development.

Two-Stage Lean-Burn Combustion Inside a Natural-Gas Spark-Ignition Engine With a Bowl-in-Piston Chamber

2019 ◽  
Author(s):  
Jinlong Liu ◽  
Cosmin E. Dumitrescu
Keyword(s):  
Natural Gas ◽  
Combustion Chamber ◽  
Combustion Process ◽  
Spark Ignition ◽  
Spark Ignition Engine ◽  
Intake Manifold ◽  
Hydrocarbon Emissions ◽  
Fuel Injector ◽  
Unburned Hydrocarbon ◽  
Piston Chamber

Abstract The conversion of existing diesel engines to spark ignition (SI) operation by adding a low-pressure injector in the intake manifold for fuel delivery and replacing the original high-pressure fuel injector with a spark plug to initiate and control the combustion process can reduce U.S. dependence on petroleum imports and increase natural gas (NG) applications in heavy-duty transportation sectors. Since the conventional diesel combustion chamber (i.e., flat-head-and-bowl-in-piston-chamber) creates high turbulence, the converted NG SI engine can operate leaner with stable and repeatable combustion process. However, existing literatures point to a long late-combustion duration and increased unburned hydrocarbon emissions in such retrofitted engines that maintained the original combustion chamber. Consequently, the main objective of this paper was to report recent findings of NG combustion characteristics inside a bowl-in-piston combustion chamber that will add to the general understanding of the phenomena. The new results indicated that the premixed NG burn inside the bowl-in-piston combustion chamber will separate into a bowl-burn and a squish-burn processes in terms of burning location and timing. The slow burning event in the squish region explains the low slope of the burn rate towards the end of combustion in existing studies (hence the longer late-combustion period). In addition, the less-favorable conditions for the combustion in the squish region explained the increased carbon monoxide and unburned hydrocarbon emissions.

On the use of artificial neural networks to model the performance and emissions of a heavy-duty natural gas spark ignition engine

2021 ◽  
pp. 146808742110344
Author(s):  
Qiao Huang ◽  
Jinlong Liu ◽  
Christopher Ulishney ◽  
Cosmin E Dumitrescu
Keyword(s):  
Neural Network ◽  
Natural Gas ◽  
Combustion Process ◽  
Spark Ignition ◽  
Spark Ignition Engine ◽  
Heavy Duty ◽  
Network Algorithm ◽  
Performance And Emissions ◽  
Neural Network Algorithm ◽  
Artificial Neural

The use of computational models for internal combustion engine development is ubiquitous. Numerical simulations using simpler to complex physical models can predict engine’s performance and emissions, but they require large computational capabilities. By comparison, statistical methodologies are more economical tools in terms of time and resources. This paper investigated the use of an artificial neural network algorithm to simulate the nonlinear combustion process inside the cylinder. Three engine control variables (i.e. spark timing, mixture equivalence ratio, and engine speed) were set as the model inputs. Outputs included peak cylinder pressure and its location, maximum pressure rise rate, indicated mean effective pressure, ignition lag, combustion phasing, burn duration, exhaust temperature, and engine-out emissions (i.e. nitrogen oxides, carbon monoxide, and unburned hydrocarbons). Eighty percent of the experimental data from a heavy-duty natural gas spark ignition engine were utilized to train the model. The perceptions accurately learned the combustion characteristics and predicted engine responses with acceptable errors, evidenced by close-to-unity coefficient of determination and close-to-zero root-mean-square error. Moreover, the regressors captured the effect of key operating variables on the engine response, suggesting the well-trained models successfully identified the complex relationships and can help assist engine analysis. Overall, the neural network algorithm was appropriate for the application investigated in this study.

An Experimental Study of the Combustion Process in a Natural-Gas Spark-Ignition Engine

2019 ◽  
Author(s):  
Jinlong Liu ◽  
Cosmin E. Dumitrescu ◽  
Hemanth Bommisetty
Keyword(s):  
Natural Gas ◽  
Equivalence Ratio ◽  
Internal Combustion Engines ◽  
Combustion Process ◽  
Spark Ignition ◽  
High Energy ◽  
Operating Conditions ◽  
Spark Ignition Engine ◽  
Intake Manifold ◽  
Spark Timing

Abstract The conversion of existing internal combustion engines to natural-gas operation can reduce U.S. dependence on petroleum imports and curtail engine-out emissions. In this study, a diesel engine with a 13.3 compression ratio was modified to natural-gas spark-ignited operation by replacing the original diesel injector with a high-energy spark plug and by fumigating fuel inside the intake manifold. The goal of this research was to investigate the combustion process inside the flat-head and bowl-in-piston chamber of such retrofitted engine when operated at different spark timings, mixture equivalence ratios, and engine speeds. The results indicated that advanced spark timing, a lower equivalence ratio, and a higher speed operation increased the ignition lag and made it more difficult to initiate the combustion process. Further, advanced spark timing, a larger equivalence ratio, and a lower speed operation accelerated the flame propagation process inside the piston bowl and advanced the start of the burn inside the squish. However, such conditions increased the burning duration inside the squish due to more fuel being trapped inside the squish volume and the smaller squish height during combustion. As a result, the end of combustion was almost the same despite the change in the operating conditions. In addition, the reliable ignition, stable combustion, and the lack of knocking showed promise for the application of natural-gas lean-burn spark-ignition operation in the heavy-duty transportation.

Numerical and Experimental Characterization of a Natural Gas Engine With Partially Stratified Charge Spark Ignition

2010 ◽  
Vol 133 (2) ◽  
Author(s):  
E. C. Chan ◽  
M. H. Davy ◽  
G. de Simone ◽  
V. Mulone
Keyword(s):  
Natural Gas ◽  
Combustion Process ◽  
Spark Ignition ◽  
Spark Ignition Engine ◽  
Combustion Model ◽  
Turbulence Energy ◽  
Turbulent Fluctuation ◽  
Stratified Charge ◽  
Gas Engine ◽  
Natural Gas Engine

This paper outlines the development of a comprehensive numerical framework for the partially stratified charge (PSC) lean-burn natural gas engine. A 3D model of the engine was implemented to represent fluid motion and combustion. The spark ignition model was based on the works of Herweg and Maly (1992, “A Fundamental Model for Flame Kernel Formation in SI Engines,” SAE Technical Publication, Paper No. 922243) and Tan and Reitz (2006, “An Ignition and Combustion Model Based on the Level-Set Method for Spark Ignition Engine Multidimensional Modeling,” Combust. Flame, 145, pp. 1–15). The EDC model (Ertesvåg and Magnussen, 2000, “The Eddy Dissipation Turbulence Energy Cascade Model,” Combust. Sci. Technol., 159, pp. 213–235) with a two-step mechanism was used to model natural gas turbulent combustion process. An open geometry simulation strategy was adopted to account for intake-exhaust gas and valve movements. Each simulation was executed for multiple cycles to produce a representative residual gas fraction. The numerical results were compared with the experimental data obtained on the Ricardo Hydra single cylinder research engine for both homogeneous and PSC cases and they were found to be in excellent agreement in pressure trace and heat release rate. The detailed investigation of the numerical data showed the development of an ignitable mixture under PSC cases, allowing stable kernel growth well beyond the lean misfire limit of the bulk mixture. Furthermore, limits on successful ignition can be identified using the ignition model, which exhibited self-similar behavior in terms of flame speed and turbulent fluctuation. It can also be shown that, at ultralean air-fuel ratios, the PSC plume helps replicate the ignition conditions that can be found under stoichiometric operation.

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.

Twin-Peak Heat Release Phenomenon Inside a Heavy-Duty Diesel Engine Retrofitted to Natural-Gas Spark Ignition

2019 ◽  
Author(s):  
Jinlong Liu ◽  
Cosmin E. Dumitrescu ◽  
Christopher Ulishney
Keyword(s):  
Diesel Engine ◽  
Natural Gas ◽  
Heat Release ◽  
Energy Release ◽  
Flame Propagation ◽  
Combustion Process ◽  
Spark Ignition ◽  
Operating Conditions ◽  
Heavy Duty ◽  
Double Peak

Abstract Existing compression ignition engines can be modified to spark ignition configuration to increase the use of natural gas in the heavy-duty transportation sector. A better understanding of the premixed natural gas combustion inside the original diesel chamber (i.e., flat-head-and-bowl-in-piston) will help improve the conversion process and therefore accelerate the diesel engine conversion. Previous studies indicated that the burning process in such engines is a two-stage combustion with a fast burning inside the bowl and a slower burning inside the squish. This paper used experimental and numerical results to investigate the combustion process at a more advanced spark timing representative of ultra-lean medium-load operation, which placed most of the combustion inside the compression stroke. At such operating conditions, the high turbulence intensity inside the squish region accelerated the flame propagation inside the squish region to the point that the burn inside the bowl separated less from that inside the squish region. However, several individual cycles produced a double-peak energy-release with the peak locations closer to the only one heat release peak seen in the average cycle. Moreover, RANS CFD simulations indicated that the time at which the flame entered the squish region was near the peak location of the energy-release process for the conditions investigated here. As a result, the data suggests that the double-peak seen in the apparent heat release rate was the result of the cycle-by-cycle variation in the flame propagation.

scholarly journals The Effect of Intake Valve Timing on Spark-Ignition Engine Performances Fueled by Natural Gas at Low Power

Energies ◽  
2022 ◽  
Vol 15 (2) ◽  
pp. 398
Author(s):  
Alfredas Rimkus ◽  
Tadas Vipartas ◽  
Donatas Kriaučiūnas ◽  
Jonas Matijošius ◽  
Tadas Ragauskas
Keyword(s):  
Energy Source ◽  
Natural Gas ◽  
Alternative Energy ◽  
Combustion Process ◽  
Spark Ignition ◽  
Spark Ignition Engine ◽  
Valve Closure ◽  
Intake Valve ◽  
Valve Timing ◽  
Spark Timing

To reduce the greenhouse effect, it is important to reduce not only carbon dioxide but also methane emissions. Methane gas can be not only a fossil fuel (natural gas) but also a renewable energy source when it is extracted from biomass. After biogas has been purified, its properties become closer to those of natural gas or methane. Natural gas is an alternative energy source that can be used for spark-ignition engines, but its physicochemical properties are different from those of gasoline, and the spark-ignition engine control parameters need to be adjusted. This article presents the results of a study that considers a spark-ignition engine operating at different speeds (2000 rpm, 2500 rpm, and 3000 rpm) and the regulation of the timing of intake valve closure when the throttle is partially open (15%), allowing the engine to maintain the stoichiometric air–fuel mixture and constant spark timing. Studies have shown a reduction in engine break torque when petrol was replaced by natural gas, but break thermal efficiency has increased and specific emissions of pollutants (NOx, HC, CO2 (g/kWh)) have decreased. The analysis of the combustion process by the AVL BOOST program revealed different results when the engine ran on gasoline as opposed to when it ran on natural gas when the timing of intake valve closure changed. The volumetric efficiency of the engine and the speed of the combustion process, which are significant for engine performance due to the different properties of gasoline and natural gas fuels, can be partially offset by adjusting the spark timing and timing of intake valve closure. The effect of intake valve timing on engine fueled by natural gas more noticeable at lower engine speeds when the engine load is low.

Laminar flame speed correlations for methane, ethane, propane and their mixtures, and natural gas and gasoline for spark-ignition engine simulations

2017 ◽  
Vol 18 (9) ◽  
pp. 951-970 ◽  
Author(s):  
Riccardo Amirante ◽  
Elia Distaso ◽  
Paolo Tamburrano ◽  
Rolf D Reitz
Keyword(s):  
Natural Gas ◽  
Laminar Flame ◽  
Spark Ignition ◽  
Flame Speed ◽  
Operating Conditions ◽  
Spark Ignition Engine ◽  
Computational Time ◽  
Laminar Flame Speed ◽  
Spark Ignition Engines ◽  
Empirical Correlations

The laminar flame speed plays an important role in spark-ignition engines, as well as in many other combustion applications, such as in designing burners and predicting explosions. For this reason, it has been object of extensive research. Analytical correlations that allow it to be calculated have been developed and are used in engine simulations. They are usually preferred to detailed chemical kinetic models for saving computational time. Therefore, an accurate as possible formulation for such expressions is needed for successful simulations. However, many previous empirical correlations have been based on a limited set of experimental measurements, which have been often carried out over a limited range of operating conditions. Thus, it can result in low accuracy and usability. In this study, measurements of laminar flame speeds obtained by several workers are collected, compared and critically analyzed with the aim to develop more accurate empirical correlations for laminar flame speeds as a function of equivalence ratio and unburned mixture temperature and pressure over a wide range of operating conditions, namely [Formula: see text], [Formula: see text] and [Formula: see text]. The purpose is to provide simple and workable expressions for modeling the laminar flame speed of practical fuels used in spark-ignition engines. Pure compounds, such as methane and propane and binary mixtures of methane/ethane and methane/propane, as well as more complex fuels including natural gas and gasoline, are considered. A comparison with available empirical correlations in the literature is also provided.

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