Methods for Specific Emission Evaluation in SI Engines Based on Calculation Procedures of Air-Fuel Ratio: Development, Assessment and Critical Comparison

2003 ◽  
Author(s):  
Stefano d’Ambrosio ◽  
Ezio Spessa ◽  
Alberto Vassallo
Keyword(s):  
Operating Conditions ◽  
Sensor Data ◽  
Injection System ◽  
Specific Mass ◽  
Nox Formation ◽  
Exhaust Gases ◽  
Wide Range ◽  
Specific Emissions ◽  
Ic Engines ◽  
Working Parameters

New computational procedures are proposed for evaluating the exhaust brake specific mass emissions of each pollutant species in IC engines. The procedures start from the chemical reaction of fuel with combustion air and, basing on the measured exhaust raw emissions THC, CH4, NOx, CO, O2, CO2, calculate the volume fractions of the compounds in the exhaust gases, including those that are not usually measured, such as water, nitrogen and hydrogen. The method also takes the effects of various fuel and combustion air compositions into account, with particular reference to different natural gas blends as well as to the presence of water vapor, CO2, Ar and He in the combustion air. The molecular mass of the exhaust gases is then evaluated and the brake specific emissions can be obtained if the exhaust flow rate and the engine power output are measured. The methods stem from the extension of the different procedures that are used in the literature to evaluate α from measured raw volume emissions of IC engines running on conventional fuels. In the present study, a new algorithm is developed so as to generalize and refine all the mentioned α evaluation procedures, keeping conventional and alternative fuel compositions into account. First, the algorithm is applied to the evaluation of α in an automotive bi-fuel SI engine running on gasoline and CNG under a wide range of operating conditions. The α evaluation tests were carried out with a carefully controlled multipoint sequential injection system for both gasoline and CNG fueling. The results are compared to those obtained from the directly measured air and fuel mass flow rates as well as from more conventional UEGO sensor data. The algorithm is then applied to the evaluation of the brake specific mass emission of each pollutant species under gasoline and CNG engine operations for different steady-state working conditions. The sensitivity of results to the main engine working parameters, the influence of environmental conditions (in particular the effect of air humidity on NOx formation) and the experimental uncertainties are determined. The specific emissions calculated from the proposed algorithm are finally compared to those obtained by applying SAE and ISO recommended practices.

Methods for Specific Emission Evaluation in Spark Ignition Engines Based on Calculation Procedures of Air-Fuel Ratio: Development, Assessment, and Critical Comparison

2005 ◽  
Vol 127 (4) ◽  
pp. 869-882 ◽  
Author(s):  
Stefano d’Ambrosio ◽  
Ezio Spessa ◽  
Alberto Vassallo
Keyword(s):  
Natural Gas ◽  
Spark Ignition ◽  
Operating Conditions ◽  
Specific Mass ◽  
Exhaust Gases ◽  
Fuel Ratio ◽  
Wide Range ◽  
Specific Emissions ◽  
Ic Engines ◽  
New Procedures

New computational procedures are proposed for evaluating the exhaust brake specific mass emissions of each pollutant species in internal combustion (IC) engines. The procedures start from the chemical reaction of fuel with combustion air and, based on the measured exhaust raw emissions THC, CH4,NOx, CO, O2,CO2, calculate the volume fractions of the compounds in the exhaust gases, including those that are not usually measured, such as water, nitrogen and hydrogen. The molecular mass of the exhaust gases is then evaluated and the brake specific emissions can be obtained if the exhaust flow rate and the engine power output are measured. The algorithm can also be applied to the evaluation of air-fuel ratio from measured raw volume emissions of IC engines. The new procedures take the effects of various fuel and combustion air compositions into account, with particular reference to different natural gas blends as well as to the presence of water vapor, CO2, Ar and He in the combustion air. In the paper, the algorithms are applied to the evaluation of air-fuel ratio and brake specific mass emissions in an automotive bi-fuel Spark Ignition (SI) engine with multipoint sequential port-fuel injection. The experimental tests were carried out in a wide range of steady-state operating conditions under both gasoline and compressed natural gas operations. The specific emissions calculated from the new procedures are compared to those evaluated by applying Society of Automotive Engineers (SAE) and International Standards Organization (ISO) recommended practices and the air-fuel ratio results are compared to those obtained either from directly measured air and fuel mass flow rates or from Universal Exhaust Gas Oxygen (UEGO) sensor data. The sensitivity of the procedure results to the main engine working parameters, the influence of environmental conditions (in particular the effect of air humidity on NOx formation) and the experimental uncertainties are also determined.

Using Multi-Dimensional Combustion Simulations of a Natural Gas/Diesel Dual Fuel Engine to Investigate NOx Trends With Air-Fuel Ratio

2017 ◽  
Author(s):  
Andrew Hockett ◽  
Michael Flory ◽  
Joel Hiltner ◽  
Scott Fiveland
Keyword(s):  
Natural Gas ◽  
Oil And Gas ◽  
Operating Conditions ◽  
Dual Fuel ◽  
Nox Emissions ◽  
Nox Formation ◽  
Jet Flame ◽  
Gas Drilling ◽  
Fuel Ratio ◽  
Wide Range

Natural gas/diesel dual fuel engines used in oil and gas drilling operations must be able to meet NOx emissions limits across a wide range of substitution percentage, which affects the air to natural gas ratio or gas lambda. In a dual fuel engine operating at high substitution, premixed, propagating natural gas flames occur and the NOx formed in such premixed flames is known to be a strong function of gas lambda. Consequently there is interest in understanding how NOx formation in a dual fuel engine is affected by gas lambda. However, NOx formation in a dual fuel engine is complicated by the interaction with the non-premixed diesel jet flame. As a result, previous studies have shown that enriching the air-fuel ratio can either increase or decrease NOx emissions depending on the operating conditions investigated. This study presents multi-dimensional combustion simulations of an air-fuel ratio sweep from gas lambda 2.0 to 1.5 at 80% substitution, which exhibited a minimum in NOx emissions at a natural gas lambda of 1.75. Images from the simulations are used to provide detailed explanations of the physical processes responsible for the minimum NOx trend with natural gas lambda.

Experimental Study on Effects of Nozzle Hole Geometry on Achieving Low Diesel Engine Emissions

2009 ◽  
Vol 132 (2) ◽  
Author(s):  
Prashanth K. Karra ◽  
Song-Charng Kong
Keyword(s):  
Diesel Engine ◽  
Exhaust Gas Recirculation ◽  
Operating Conditions ◽  
Injection System ◽  
Exhaust Gas ◽  
Convergent Nozzle ◽  
Wide Range ◽  
Soot Emissions ◽  
Gas Recirculation ◽  
Injection Pressures

Three injectors with different nozzle geometries were tested in a multicylinder diesel engine with a high-pressure common-rail injection system. Various injection pressures were tested along with exhaust gas recirculation to achieve low NOx and soot emissions. The injectors used in the study included a six-hole nozzle, a ten-hole nozzle, and a six-hole convergent nozzle with a K-factor of 3. All three injectors had the same flow numbers. All three injectors tested were effective in reducing NOx and soot emissions at appropriate conditions. It was found that low temperature combustion can be achieved by using high levels of exhaust gas recirculation with late injection timings. High injection pressures significantly reduced soot emissions at conventional injection timings. The effect of injection pressure was not significant at retarded injection timings, i.e., 5 ATDC. The convergent nozzle was found to produce higher soot emissions compared with the straight-hole nozzle under the same injection conditions. Effects of the convergent nozzle on NOx emissions and fuel consumption were not significant. The small nozzle size in the ten-hole injector can generate smaller fuel drops and lead to better atomization. The ten-hole injector appeared to have better air utilization and resulted in significant reductions in NOx and soot emissions over a wide range of operating conditions.

scholarly journals High Amplitude Combustion Instabilities in an Annular Combustor Inducing Pressure Field Deformation and Flame Blow Off

2019 ◽  
Vol 142 (1) ◽  
Author(s):  
Guillaume Vignat ◽  
Daniel Durox ◽  
Antoine Renaud ◽  
Sébastien Candel
Keyword(s):  
Velocity Field ◽  
Pressure Distribution ◽  
Pressure Field ◽  
High Amplitude ◽  
Nodal Line ◽  
Operating Conditions ◽  
Injection System ◽  
Combustion Instabilities ◽  
Wide Range ◽  
Annular Combustor

Abstract This article reports experiments carried out in the laboratory scale annular combustor MICCA-spray equipped with multiple swirling spray injectors. The experimental setup consists in an air plenum connected to a combustion chamber formed by two concentric cylindrical quartz tubes, allowing full optical access to the flames. A new injection system is introduced and characterized. For a wide range of operating conditions, strong combustion instabilities are observed, but the focus of this article is placed on very high amplitude combustion instabilities coupled by a standing azimuthal mode. New results are obtained using a higher order reconstruction method for the pressure field: its shape is shown to be modified during high amplitude oscillation, leading to asymmetries of the pressure distribution in the system. Flame blow off occurs near the pressure nodal line when a critical level of oscillation is reached. A method is proposed to reconstruct the acoustic velocity field just before blow off occurs and in this way determine the blow off threshold. It is found that the pressure distribution, velocity field, and blow off pattern become asymmetric as the amplitude of oscillation increases and that this process is accompanied by a rapid shift in frequency of oscillation. Another notable result is that the heat release rate in the flames on the same side of the nodal line is not perfectly in phase and that the phase differences become larger as the amplitude of oscillation increases.

scholarly journals Analysis of the impact of damage to the injection system on the emission of toxic substances in a spark-ignition internal combustion engine

2019 ◽  
Vol 179 (4) ◽  
pp. 112-118
Author(s):  
Mieczysław DZIUBIŃSKI ◽  
Ewa SIEMIONEK ◽  
Artur DROZD ◽  
Paweł ŻUR ◽  
Michał ŚCIRKA ◽  
...  
Keyword(s):  
Internal Combustion Engine ◽  
Combustion Engine ◽  
Internal Combustion ◽  
Spark Ignition ◽  
Operating Conditions ◽  
Injection System ◽  
Coolant Temperature ◽  
Toxic Substances ◽  
Exhaust Gases ◽  
The Impact

The article presented analyses the impact of damage to the injection system on the emission of toxic subsumes in a spark-ignition internal combustion engine. The work focuses on the basic elements of the injection system, which include injectors, throttle position sensor, coolant temperature sensor and lambda sensor. In addition, a catalytic reactor has been included in the context of its direct cooperation with the injection system under set conditions. The toxicity of exhaust gases of different spark-ignition engines fueled with petrol or gas in determined operating conditions using the MAHA MGT5 exhaust gas analyser was tested. The content of toxic substances in the exhaust gases was recorded for the correct settings of the injection system and for the engine working with damage to this system. The tests carried out will allow to assess the impact of the damage of the injection system on the toxicity of exhaust gases.

Experimental Investigation and Numerical Modeling of Spray Combustion and Emission in a Diesel Engine

2002 ◽  
Author(s):  
Xiao-Bei Cheng ◽  
Rong-Hua Huang ◽  
Wang Zhi ◽  
Mei-Lin Zhu
Keyword(s):  
Diesel Engine ◽  
Formation Process ◽  
Operating Conditions ◽  
Turbulent Dispersion ◽  
Injection System ◽  
Spray Combustion ◽  
Injection Timing ◽  
Nox Formation ◽  
Pollutant Formation ◽  
Good Agreement

An improved multi-dimensional CFD code has been employed to simulate the spray, combustion and pollution formation process within a diesel engine cylinder. The computational results are compared with experimental data from an optical high-speed research engine equipped with a high-pressure injection system. Several spray sub-models have been implemented into the code, and their influence on the predicted droplet characteristic was evaluated. These models account for liquid core atomization, droplet secondary breakup, spray/wall interaction, droplet turbulent dispersion and evaporation. These models improve the prediction of the droplet sizes within a diesel spray and provides a more accurate initial condition for the evaporation, combustion models. The combustion sub-model employed has two components: one for predicting auto-ignition and one for computing the subsequent combustion of the ignited gas. Thermal NOx formation is calculated according to the extended Zeldovich mechanism, which gives the NOx formation as a function of temperature and O, H and OH radical concentrations. Soot formation process adopted in present study is modeled according to a hybrid chemical kinetics/turbulent mixing controlled rate expression. For the engine configurations and operating conditions considered, in most case the calculated cylinder averaged results show good agreement between measured and global pressure, heat release rate and emission data, but in some case they have limitations. Discrepancies are highlighted and possible reasons suggested. The major influences of the injection timing and combustion chamber geometry on the pollutant formation processes have been identified. The calculated results provide a detailed insight into the processes governing combustion and pollutant formation in spray flames under diesel engine conditions. The good agreement indicates that computer models are available for use by the engine industry to provide directions for engine design.

Modeling Mixture Formation in a Gasoline Direct Injection Engine

2005 ◽  
Vol 73 (6) ◽  
pp. 931-939 ◽  
Author(s):  
Rossella Rotondi
Keyword(s):  
Flow Field ◽  
Fuel Injection ◽  
Direct Injection ◽  
Operating Conditions ◽  
Gasoline Direct Injection ◽  
Injection System ◽  
Fuel Spray ◽  
Computational Domain ◽  
Mixture Formation ◽  
Wide Range

Mixture formation and combustion in a gasoline direct injection (GDI) engine were studied. A swirl-type nozzle, with an inwardly opening pintle, was used to inject the fuel directly in a four stroke, four cylinder, four valves per cylinder engine. The atomization of the hollow cone fuel spray was modeled by using a hybrid approach. The most important obstacle in the development of GDI engines is that the control of the stratified-charge combustion over the entire operating range is very difficult. Since the location of the ignition source is fixed in SI engines the mixture cloud must be controlled both temporally and spatially for a wide range of operating conditions. Results show that the volume of the spark must be considered when discretizing the computational domain because it highly influences the flow field in the combustion chamber. This is because the volume occupied by the plug cannot be neglected since it is much bigger than the ones used in port fuel injection engines. The development of a successful combustion system depends on the design of the fuel injection system and the matching with the in-cylinder flow field: the stratification at part load appears to be the most crucial and critical step, and if the air motion is not well coupled with the fuel spray it would lead to an increase of unburned hydrocarbon emission and fuel consumption

scholarly journals Development of an Oil Injection System Optimised to the ABB Double Cone Burner

1999 ◽  
Author(s):  
Manfred Aigner ◽  
E. Geoffrey Engelbrecht ◽  
Adnan Eroglu ◽  
Jaan Hellat ◽  
Khawar J. Syed
Keyword(s):  
Natural Gas ◽  
Gas Turbine ◽  
Operating Conditions ◽  
Double Cone ◽  
Injection System ◽  
Wide Range ◽  
Development Procedure ◽  
Oil And Natural Gas ◽  
Unburned Hydrocarbons ◽  
Oil Injection

Present day land-based gas turbine combustors, operating on oil, must meet strict requirements for emissions (CO, unburned hydrocarbons, particulates, smoke and NOx) and burn stabily without pulsations over a wide range of operating conditions. In addition many engines, such as those produced by ABB, operate with both oil and natural gas fuels either together or independently. This paper concentrates on the development of an oil injection system which is optimised for ABB’s double cone burner (Figure 1) and which does not affect the operation of this burner on natural gas. The development procedure, which involved a coupling of numerical and experimental techniques, is described. The results of the application of this procedure indicate that a simple plain jet atomiser in conjunction with a small quantity of unswirling air admitted at the head of the burner is the best option for this burner.

scholarly journals High Amplitude Combustion Instabilities in an Annular Combustor Inducing Pressure Field Deformation and Flame Blow-Off

2019 ◽  
Author(s):  
Guillaume Vignat ◽  
Daniel Durox ◽  
Antoine Renaud ◽  
Sébastien Candel
Keyword(s):  
Velocity Field ◽  
Pressure Field ◽  
High Amplitude ◽  
Nodal Line ◽  
Operating Conditions ◽  
Injection System ◽  
Reconstruction Method ◽  
Combustion Instabilities ◽  
Wide Range ◽  
Annular Combustor

Abstract This article reports experiments carried out in the laboratory scale annular combustor MICCA-Spray equipped with multiple swirling spray injectors. The experimental setup consists in an air plenum connected to a combustion chamber formed by two concentric cylindrical quartz tubes, allowing full optical access to the flames. A new injection system is introduced and characterized. For a wide range of operating conditions, strong combustion instabilities are observed, but the focus of this article is placed on very high amplitude combustion instabilities coupled by a standing azimuthal mode. It is found that the frequency decreases as the amplitude of the thermoacoustic oscillation grows. New results are obtained using a higher order reconstruction method for the pressure field: its shape is shown to be modified during high amplitude oscillation, leading to asymmetries of the pressure distribution in the system. Flame blow-off occurs near the pressure nodal line when a critical level of oscillation is reached. A method is proposed to reconstruct the acoustic velocity field just before blow-off occurs. Both the velocity field and the blow-off pattern are skewed. The effect of flame blow-off on the frequency of the oscillation is discussed, and it is shown that it leads to the distortion of the pressure field. A new result is also that the phase of the flame response to acoustic perturbation can vary among flames on the same side of the nodal line.

Comparison of Deterministic and Linear Cosine Spatial Filtering of Transmission Electron Micrographs

1972 ◽  
Vol 30 ◽  
pp. 596-597
Author(s):  
David A. Ansley
Keyword(s):  
Spherical Aberration ◽  
Focal Length ◽  
Chromatic Aberration ◽  
Spatial Filter ◽  
Operating Conditions ◽  
Objective Lens ◽  
List Type ◽  
Spatial Filters ◽  
Transmission Electron ◽  
Wide Range

The coherence of the electron flux of a transmission electron microscope (TEM) limits the direct application of deconvolution techniques which have been used successfully on unmanned spacecraft programs. The theory assumes noncoherent illumination. Deconvolution of a TEM micrograph will, therefore, in general produce spurious detail rather than improved resolution.A primary goal of our research is to study the performance of several types of linear spatial filters as a function of specimen contrast, phase, and coherence. We have, therefore, developed a one-dimensional analysis and plotting program to simulate a wide 'range of operating conditions of the TEM, including adjustment of the:(1) Specimen amplitude, phase, and separation(2) Illumination wavelength, half-angle, and tilt(3) Objective lens focal length and aperture width(4) Spherical aberration, defocus, and chromatic aberration focus shift(5) Detector gamma, additive, and multiplicative noise constants(6) Type of spatial filter: linear cosine, linear sine, or deterministic

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