Effect of split fuel injection on heat release and pollutant emissions in partially premixed combustion of PRF70/air/EGR mixtures

Dilution of partially-premixed combustion (PPC) using different combinations of excess air (λ>1) and exhaust gas recirculation (EGR) was investigated in a single-cylinder, heavy-duty diesel engine equipped with common-rail fuel injection. The experiments were limited to a single fuel injection event using ultra-low sulphur diesel fuel at a low engine load (∼3 bar BMEP) and engine speeds of 900 and 1350 rpm. The start of injection was varied to optimize the combustion performance and emissions. The experimental results show that increasing air dilution at constant EGR reduced BSFC slightly. CO and HC emissions decreased significantly due to the increased oxygen concentration, but NOx and soot emissions increased. For a given level of charge dilution, there was an optimal EGR rate to minimize BSFC. NOx emissions decreased significantly as the proportion of dilution by EGR was increased, but CO and HC emissions increased due to the reduced in-cylinder temperature and oxygen concentration, which increased the combustion duration.

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Combustion stratification study of partially premixed combustion using Fourier transform analysis of OH* chemiluminescence images

International Journal of Engine Research ◽

10.1177/1468087417740270 ◽

2017 ◽

Vol 19 (10) ◽

pp. 1024-1035 ◽

Cited By ~ 2

Author(s):

Mohammad Izadi Najafabadi ◽

Bart Somers ◽

Bengt Johansson ◽

Nico Dam

Keyword(s):

Heat Release ◽

High Speed ◽

Spatial Information ◽

Fourier Transforms ◽

Combustion Regime ◽

Premixed Combustion ◽

Two Dimensional ◽

Spatial Frequencies ◽

Partially Premixed Combustion ◽

Partially Premixed

A relatively high level of stratification (qualitatively: lack of homogeneity) is one of the main advantages of partially premixed combustion over the homogeneous charge compression ignition concept. Stratification can smooth the heat release rate and improve the controllability of combustion. In order to compare stratification levels of different partially premixed combustion strategies or other combustion concepts, an objective and meaningful definition of “stratification level” is required. Such a definition is currently lacking; qualitative/quantitative definitions in the literature cannot properly distinguish various levels of stratification. The main purpose of this study is to objectively define combustion stratification (not to be confused with fuel stratification) based on high-speed OH* chemiluminescence imaging, which is assumed to provide spatial information regarding heat release. Stratification essentially being equivalent to spatial structure, we base our definition on two-dimensional Fourier transforms of photographs of OH* chemiluminescence. A light-duty optical diesel engine has been used to perform the OH* bandpass imaging on. Four experimental points are evaluated, with injection timings in the homogeneous regime as well as in the stratified partially premixed combustion regime. Two-dimensional Fourier transforms translate these chemiluminescence images into a range of spatial frequencies. The frequency information is used to define combustion stratification, using a novel normalization procedure. The results indicate that this new definition, based on Fourier analysis of OH* bandpass images, overcomes the drawbacks of previous definitions used in the literature and is a promising method to compare the level of combustion stratification between different experiments.

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Simulation of Turbulent Lifted Flames Using a Partially-Premixed Coherent Flame Model (PCFM)

Volume 3: Combustion, Fuels and Emissions, Parts A and B ◽

10.1115/gt2008-50441 ◽

2008 ◽

Author(s):

Yongzhe Zhang ◽

Rajesh Rawat

Keyword(s):

Turbulent Combustion ◽

Practical Interest ◽

Flame Stabilization ◽

Premixed Combustion ◽

Pollutant Emissions ◽

Jet Flame ◽

Premixed Turbulent Combustion ◽

Partially Premixed Combustion ◽

Lifted Flames ◽

Partially Premixed

Partially-premixed combustion occurs in many combustion devices of practical interest, such as gas-turbine combustors. Development of corresponding turbulent combustion models is important to improve the design of these systems in efforts to reduce fuel consumption and pollutant emissions. Turbulent lifted flames have been a canonical problem for testing models designed for partially-premixed turbulent combustion. In this paper we propose modifications to the coherent flame model (CFM) so that it can be brought to the simulation of partially-premixed combustion. For the primary premixed flame, a transport equation for flame area density is solved in which the wrinkling effects of the flame stretch and flame annihilation are considered. For the subsequent non-premixed zone, a laminar flamelet PPDF methodology, which accounts for the non-equilibrium and finiterate chemistry effects, is adopted. The model is validated against the experimental data on a lifted H2/N2 jet flame issuing into a vitiated coflow. In general there is fairly good agreement between the calculations and measurements both in profile shapes and peak values. Based on the simulation results the flame stabilization mechanism for lifted flames is investigated.

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Study on low temperature heat release of partially premixed combustion in a heavy duty engine for real-time applications

Applied Thermal Engineering ◽

10.1016/j.applthermaleng.2018.11.003 ◽

2019 ◽

Vol 148 ◽

pp. 219-228 ◽

Cited By ~ 3

Author(s):

Cheng Fang ◽

Per Tunestal ◽

Lianhao Yin ◽

Fuyuan Yang ◽

Xiaofan Yang

Keyword(s):

Low Temperature ◽

Heat Release ◽

Real Time ◽

Premixed Combustion ◽

Heavy Duty ◽

Partially Premixed Combustion ◽

Temperature Heat ◽

Real Time Applications ◽

Partially Premixed

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Fuel Stratification and Partially Premixed Combustion With Neat n-Butanol in a Compression Ignition Engine

Journal of Engineering for Gas Turbines and Power ◽

10.1115/1.4040517 ◽

2018 ◽

Vol 140 (12) ◽

Cited By ~ 3

Author(s):

Shouvik Dev ◽

Tongyang Gao ◽

Xiao Yu ◽

Mark Ives ◽

Ming Zheng

Keyword(s):

Fuel Injection ◽

Direct Injection ◽

Premixed Combustion ◽

Injection Timing ◽

Compression Ignition ◽

Compression Ignition Engine ◽

Fuel Stratification ◽

Partially Premixed Combustion ◽

Partially Premixed ◽

Ci Engines

Homogeneous charge compression ignition (HCCI) has been considered as an ideal combustion mode for compression ignition (CI) engines due to its superb thermal efficiency and low emissions of nitrogen oxides (NOx) and particulate matter. However, a challenge that limits practical applications of HCCI is the lack of control over the combustion rate. Fuel stratification and partially premixed combustion (PPC) have considerably improved the control over the heat release profile with modulations of the ratio between premixed fuel and directly injected fuel, as well as injection timing for ignition initiation. It leverages the advantages of both conventional direct injection compression ignition and HCCI. In this study, neat n-butanol is employed to generate the fuel stratification and PPC in a single cylinder CI engine. A fuel such as n-butanol can provide additional benefits of even lower emissions and can potentially lead to a reduced carbon footprint and improved energy security if produced appropriately from biomass sources. Intake port fuel injection (PFI) of neat n-butanol is used for the delivery of the premixed fuel, while the direct injection (DI) of neat n-butanol is applied to generate the fuel stratification. Effects of PFI-DI fuel ratio, DI timing, and intake pressure on the combustion are studied in detail. Different conditions are identified at which clean and efficient combustion can be achieved at a baseline load of 6 bar IMEP. An extended load of 14 bar IMEP is demonstrated using stratified combustion with combustion phasing control.

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Simulation of Turbulent Lifted Flames Using a Partially Premixed Coherent Flame Model

Journal of Engineering for Gas Turbines and Power ◽

10.1115/1.3026559 ◽

2009 ◽

Vol 131 (3) ◽

Cited By ~ 2

Author(s):

Yongzhe Zhang ◽

Rajesh Rawat

Keyword(s):

Turbulent Combustion ◽

Practical Interest ◽

Flame Stabilization ◽

Premixed Combustion ◽

Pollutant Emissions ◽

Jet Flame ◽

Premixed Turbulent Combustion ◽

Partially Premixed Combustion ◽

Lifted Flames ◽

Partially Premixed

Partially premixed combustion occurs in many combustion devices of practical interest, such as gas-turbine combustors. Development of corresponding turbulent combustion models is important to improve the design of these systems in efforts to reduce fuel consumption and pollutant emissions. Turbulent lifted flames have been a canonical problem for testing models designed for partially premixed turbulent combustion. In this paper we propose modifications to the coherent flame model so that it can be brought to the simulation of partially premixed combustion. For the primary premixed flame, a transport equation for flame area density is solved in which the wrinkling effects of the flame stretch and flame annihilation are considered. For the subsequent nonpremixed zone, a laminar flamelet presumed probability density function (PPDF) methodology, which accounts for the nonequilibrium and finite-rate chemistry effects, is adopted. The model is validated against the experimental data on a lifted H2∕N2 jet flame issuing into a vitiated coflow. In general there is fairly good agreement between the calculations and measurements both in profile shapes and peak values. Based on the simulation results, the flame stabilization mechanism for lifted flames is investigated.

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Dynamics of Flame Stabilized by Triangular Bluff Body in Partially Premixed Methane-Air Combustion

Volume 2: Combustion, Fuels and Emissions, Parts A and B ◽

10.1115/gt2011-46241 ◽

2011 ◽

Cited By ~ 2

Author(s):

T. V. Santosh Kumar ◽

P. R. Alemela ◽

J. B. W. Kok

Keyword(s):

Heat Release ◽

Vortex Shedding ◽

Bluff Body ◽

Reaction Rates ◽

Flame Stabilization ◽

Operating Conditions ◽

Premixed Combustion ◽

Partially Premixed Combustion ◽

Computational Fluid Dynamics Analysis ◽

Partially Premixed

In the design and operational tuning of gas turbine combustors it is important to be able to predict the interaction of the flame stabilization recirculation area with the burner aerodynamics. In the present paper transient computational fluid dynamics analysis is used to study these effects. Vortex interactions with the flame play a key role in many practical combustion systems. The interactions drive a large class of combustion instabilities and are responsible for changing the reaction rates, shape of the flame and the global heat release rate. The evolution of vortex shedding in reactive flows and its effects on the dynamics of the flame are important to be predicted. The present study describes dynamics of bluff body stabilized flames in a partially premixed combustion system. The bluff body is an equilateral wedge that induces the flame recirculation zone. The wedge is positioned at one-third length of the duct, which, is acoustically closed at the bottom end and open at the top. Transient computational modeling of partially premixed combustion is carried out using the commercial ANSYS CFX code and the results show that the vortex shedding has a destabilizing effect on the combustion process. Scale Adaptive Simulation turbulence model is used to compare between non-reacting cases and combustion flows to show the effects of aerodynamics-combustion coupling. The transient data reveals that frequency peaks of pressure and temperature spectra and is consistent with the longitudinal natural frequencies and Kelvin-Helmholtz instability frequency for reactive flow simulations. The same phenomenon is observed at different operating conditions of varying power. It has also been shown that the pressure and heat release are in phase, satisfying the Rayleigh criterion and therefore indicating the presence of aerodynamic-combustion instability. The data are compared to the scarce data on experiments and simulations available in literature.

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