scholarly journals Theoretical Investigation on the Influence of Physical Parameters on Soot and NOx Engine Emissions

2001 ◽  
Author(s):  
Arturo de Risi ◽  
Teresa Donateo ◽  
Domenico Laforgia
Keyword(s):  
Velocity Profile ◽  
Time Scales ◽  
Characteristic Time ◽  
Schmidt Number ◽  
Soot Formation ◽  
Physical Parameters ◽  
Nox Emissions ◽  
Swirl Ratio ◽  
Engine Emissions ◽  
Turbulent Characteristic

Abstract CFD simulations need a certain number of parameters to calibrate both empirical and analytical models. The present investigation aims at identifying the effects of these parameters on the numerical prediction of a modified version of Kiva 3V code, which includes the use of the RNG k-ε model for turbulence, the gas/wall convective heat transfer model proposed by Han, Kelvin-Helmholtz Rayleigh-Taylor spray injection and breakup models. Ignition delay was modeled with the Shell model, whereas the laminar-turbulent characteristic time model was used for combustion. Soot formation and oxidation were calculated using Hiroyasu and Nagle and Strickland-Constable models, respectively. NOx was predicted by using the extended Zel’dovich mechanism. This study was carried out for a common-rail direct injection, small-bore Diesel engine, including the investigation of both numerical and physical parameters. Numerical parameters are intended to be variables related to breakup, turbulence, and combustion models that are adjusted according to grid resolution, engine and injection system geometry, and operating conditions. In particular, the effect of laminar and turbulent time scales, characteristic breakup length and time scales, initial turbulence kinetic energy density, initial swirl velocity profile, on engine emissions was analyzed. The investigated physical parameters were initial swirl ratio, air water content, Schmidt number for mass diffusion. All simulations were performed by changing one of the above parameters at each run and keeping approximately the same pressure and heat release rate curves. Results show that similar pressure vs. crank angle curves can be obtained with different values of these parameters but they lead to very different values of predicted emissions levels. In particular, changes of laminar and turbulent characteristic time resulted in a strong influence on NOx emissions but their effects on soot levels were minor. Mass diffusion characteristics (e.g. Schmidt number) were found to strongly affect both soot and NOx emissions. Spray parameters were found mainly to affect soot formation. Furthermore, NOx and soot emissions showed a dependence on swirl ratio and velocity profile.

Effects of Nano-Nozzles Cross-Sectional Geometry on Fluid Flow: Molecular Dynamic Simulation

2017 ◽  
Vol 34 (5) ◽  
pp. 667-678 ◽  
Author(s):  
H. Nowruzi ◽  
H. Ghassemi
Keyword(s):  
Fluid Flow ◽  
Velocity Profile ◽  
Cross Sections ◽  
Md Simulation ◽  
Flow Behavior ◽  
Water Model ◽  
Physical Parameters ◽  
Cross Sectional ◽  
Behavior Characteristics ◽  
Fanning Friction Factor

AbstractNano-nozzles are an essential part of the nano electromechanical systems (NEMS). Cross-sectional geometry of nano-nozzles has a significant role on the fluid flow inside them. So, main purpose of the present study is related to the effects of different symmetrical cross-sections on the fluid flow behavior inside of nano-nozzles. To this accomplishment, five different cross-sectional geometries (equilateral triangle, square, regular hexagon, elliptical and circular) are investigated by using molecular dynamics (MD) simulation. In addition, TIP4P is used for atomistic water model. In order to evaluate the fluid flow behavior, non-dimensional physical parameters such as Fanning friction factor, velocity profile and density number are analyzed. Obtained results are shown that the flow behavior characteristics appreciably depend on the geometry of nano-nozzle's cross-section. Velocity profile and density number for five different cross sections of nano-nozzle at three various measurement gauges are presented and discussed.

Magnetohydrodynamics Williamson Fluid Comprising Gyrotactic Microorganisms Flows Through a Permeable Stretching Layer with Variable Fluid Properties

2020 ◽  
Vol 9 (4) ◽  
pp. 375-387
Author(s):  
Amit Parmar ◽  
Rakesh Choudhary ◽  
Krishna Agarwal
Keyword(s):  
Boundary Layer ◽  
Velocity Profile ◽  
Layer Thickness ◽  
Boundary Layer Thickness ◽  
Schmidt Number ◽  
Gyrotactic Microorganisms ◽  
Williamson Fluid ◽  
Non Linear ◽  
Fluid Properties ◽  
Variable Prandtl Number

The present study shows the impacts of Williamson fluid with magnetohydrodynamics flow containing gyrotactic microorganisms under the variable fluid property past permeable stretching sheet. Variable Prandtl number, mass Schmidt number, and gyrotactic microorganisms Schmidt number were all considered. The momentum, energy, mass, and microorganism equations’ governing PDEs are converted into nonlinear coupled ODEs and numerically solved with the bvp4c solver using suitable transformations. The main outcome of this study is that Williamson fluid parameter constantly decreases in velocity profile, however reverse effects can be shown in temperature profile. Also, M parameter and Kp parameter enhance the heat transfer rate, concentration rate and microorganisms boundary layer thickness but declines in momentum boundary layer thickness and velocity profile. The aim of this research is to see how velocity slide, temperature jump, concentration slip, and microorganism slip affect MHD Williamson fluid flow with gyrotactic microorganisms over a leaky surface embedded in spongy medium, with non-linear radiation and non-linear chemical reaction.

scholarly journals Characteristics of Large-Scale Orographic Precipitation in a Linear Perspective

2011 ◽  
Vol 12 (1) ◽  
pp. 27-44 ◽  
Author(s):  
Michael Kunz
Keyword(s):  
Time Scales ◽  
Characteristic Time ◽  
Large Scale ◽  
Linear Perspective ◽  
Horizontal Wind ◽  
Small Scale ◽  
Orographic Precipitation ◽  
Observation Data ◽  
Horizontal Wind Speed ◽  
Precipitation Patterns

Abstract Simulations of orographic precipitation over the low mountain ranges of southwestern Germany and eastern France with two different physics-based linear precipitation models are presented. Both models are based on 3D airflow dynamics from linear theory and consider advection of condensed water and leeside drying. Sensitivity studies for idealized conditions and a real case study show that the amount and spatial distribution of orographic precipitation is strongly controlled by characteristic time scales for cloud and hydrometeor advection and background precipitation due to large-scale lifting. These parameters are estimated by adjusting the model results on a 2.5-km grid to observed precipitation patterns for a sample of 40 representative orography-dominated stratiform events (24 h) during a calibration period (1971–80). In general, the best results in terms of lowest rmse and bias are obtained for characteristic time scales of 1600 s and background precipitation of 0.4 mm h−1. Model simulations of a sample of 84 events during an application period (1981–2000) with fixed parameters demonstrate that both models are able to reproduce quantitatively precipitation patterns obtained from observations and reanalyses from a numerical model [Consortium for Small-scale Modeling (COSMO)]. Combining model results with observation data shows that heavy precipitations over mountains are restricted to situations with strong atmospheric forcings in terms of synoptic-scale lifting, horizontal wind speed, and moisture content.

Effects of Intake Port Optimization on Soot Emission from Diesel Engine

2014 ◽  
Vol 535 ◽  
pp. 333-339
Author(s):  
Yue Chen ◽  
Lin Lv ◽  
Jie Shen
Keyword(s):  
Standard Deviation ◽  
Soot Formation ◽  
Combustion Engine ◽  
Double Helix ◽  
Direct Injection ◽  
Combustion Process ◽  
Flow Coefficient ◽  
Swirl Ratio ◽  
Characteristic Parameters ◽  
Double Tangent

All future engine developments must consider the primary task of achieving the required emission levels. An important step towards the development of combustion engines is the optimization of the flow in the intake ports. The charging movement in the combustion chamber, which is generated by the intake flow, considerably influences the quality of the combustion engine. In this paper, steady CFD analysis were applied to different structures of double-tangent-port. The swirl ratio can be improved while flow coefficient remains unchanged if port eccentricity is 34.4 mm. By defining three characteristic parameters, the speed non-uniformity index, standard deviation and mixture concentration standard deviation and equivalent ratio range, quantitatively describing the combustion process in cylinder, and then compared with transient CFD three-dimensional contours, we can see that characteristic parameters can be more accurate and comprehensive in analyzing the influence of inlet structure of soot formation. Effects of different intake ports on fuel-air mixing in a turbocharged diesel direct injection engine during intake and compression strokes are analyzed. It turns out that the optimized double-tangent-port has the highest uniformity of velocity, in the meanwhile, air/fuel mixing is relatively uniform. On the other hand, mixed-port and double-helix-port can cause uneven flow field which is bad for combustion, even though the swirl ratio can increase largely. Finally, the simulation results show that soot emissions of the optimized double-tangent-port have significantly lower levels, at 2200 r/min under full load.

scholarly journals Influence of blends of diesel and renewable fuels on CI engine emissions over transient engine conditions.

2018 ◽  
Author(s):  
Adriaan Smuts Van Niekerk ◽  
Benjamin Drew ◽  
Neil Larsen ◽  
Peter Kay
Keyword(s):  
Fuel Consumption ◽  
Co2 Emissions ◽  
Nox Emissions ◽  
Compression Ignition ◽  
Engine Emissions ◽  
Drive Cycle ◽  
Fuel Blend ◽  
High Oxygen Content ◽  
Fuel Blends ◽  
Ci Engine

To reduce the amount of carbon dioxide released from transportation the EU has implemented legislation to mandate the renewable content of petrol and diesel fuels. However, due to the complexity of the combustion process the addition of renewable content, such as biodiesel and ethanol, can have a detrimental effect on other engine emissions. In particular the engine load can have a significant impact on the emissions. Most research that have studied this issue are based on steady state tests, that are unrealistic of real world driving and will not capture the difference between full and part loads. This study aims to address this by investigating the effect of renewable fuel blends of diesel, biodiesel and ethanol on the emissions of a compression ignition engine tested over the World Harmonised Light Vehicle Test Procedure (WLTP). Diesel, biodiesel and ethanol were blended to form binary and ternary blends, the ratios were determined by Design of Experiments (DoE). The total amount of emissions for CO, CO2 and NOx as well as the fuel consumption, were measured from a 2.4 liter compression ignition (CI) engine running over the WLTP drive cycle. The results depicted that percentages smaller than 10 % of ethanol in the fuel blend can reduce CO emissions, CO2 emissions as well as NOx emissions, but increases fuel consumption with increasing percentage of ethanol in the fuel blend. Blends with biodiesel resulted in minor increases in CO emissions due to the engine being operated in the low and medium load regions over the WLTP. CO2 emissions as well as NOx emissions increased as a result of the high oxygen content in biodiesel which promoted better combustion. Fuel consumption increased for blends with biodiesel as a result from biodiesel's lower heating value. All the statistical models describing the engine responses were significant and this demonstrated that a mixture DoE is suitable to quantify the effect of fuel blends on an engine's emissions response. An optimised ternary blend of B2E9 was found to be suitable as a 'drop in' fuel that will reduce harmful emissions of CO emissions by approximately 34 %, NOx emissions by 10 % and CO2 emissions by 21 % for transient engine operating scenarios such as the WLTP drive cycle.

Investigation of Swirl Ratio Impact on In-Cylinder Flow in a SIDI Optical Engine

2015 ◽  
Author(s):  
Hanyang Zhuang ◽  
David L. S. Hung ◽  
Jie Yang ◽  
Shaoxiong Tian
Keyword(s):  
Flow Field ◽  
Soot Formation ◽  
Flow Characteristics ◽  
Control Valve ◽  
Exhaust Emission ◽  
Swirl Ratio ◽  
Optical Engine ◽  
Crank Angle ◽  
Cylinder Flow ◽  
Intake Swirl

Advanced powertrain technologies have improved engine performance with higher power output, lower exhaust emission, and better controllability. Chief among them is the development of spark-ignition direct-injection (SIDI) engines in which the in-cylinder processes control the air flow motion, fuel-air mixture formation, combustion, and soot formation. Specifically, intake air with strong swirl motion is usually introduced to form a directional in-cylinder flow field. This approach improves the mixing process of air and fuel as well as the propagation of flame. In this study, the effect of intake air swirl on in-cylinder flow characteristics was experimentally investigated. High speed particle image velocimetry (PIV) was conducted in an optical SIDI engine to record the flow field on a swirl plane. The intake air swirl motion was achieved by adjusting the opening of a swirl ratio control valve which was installed in one of the two intake ports in the optical engine. Ten opening angles of the swirl ratio control valve were adjusted to produce an intake swirl ratio from 0.55 to 5.68. The flow structures at the same crank angle degree, but under different swirl ratio, were compared and analyzed using proper orthogonal decomposition (POD). The flow dominant structures and variation structures were interpreted by different POD modes. The first POD mode captured the most dominant flow field structure characteristics; the corresponding mode coefficients showed good linearity with the measured swirl ratio at the compression stroke when the flow was swirling and steady. During the intake stroke, strong intake air motion took place, and the structures and coefficients of the first modes varied along different swirl ratio. These modes captured the flow properties affected by the intake swirl motion. Meanwhile, the second and higher modes captured the variation feature of the flow at various crank angle degrees. In summary, this paper demonstrated a promising approach of using POD to interpret the effectiveness of swirl control valve on in-cylinder swirl flow characteristics, providing better understanding for engine intake system design and optimization.

scholarly journals Superconducting fluctuations and characteristic time scales in amorphous WSi

2018 ◽  
Vol 97 (17) ◽  
Author(s):  
Xiaofu Zhang ◽  
Adriana E. Lita ◽  
Mariia Sidorova ◽  
Varun B. Verma ◽  
Qiang Wang ◽  
...  
Keyword(s):  
Time Scales ◽  
Characteristic Time ◽  
Superconducting Fluctuations

Fluid flow analysis of cilia beating in a curved channel in the presence of magnetic field and heat transfer

2020 ◽  
Vol 98 (2) ◽  
pp. 191-197 ◽  
Author(s):  
Hina Sadaf ◽  
S. Nadeem
Keyword(s):  
Magnetic Field ◽  
Heat Transfer ◽  
Velocity Profile ◽  
Flow Analysis ◽  
Fluid Motion ◽  
Flow Characteristics ◽  
Physical Parameters ◽  
Curved Channel ◽  
Radial Magnetic Field ◽  
Fluid Flow Analysis

This paper investigates fluid motion generated by cilia and a pressure gradient in a curved channel. The flow analysis is carried out in the presence of heat transfer and radial magnetic field. The leading equations are simplified under the familiar suppositions of large wavelength and small Reynolds number approximations. An exact solution has been developed for the velocity profile. The flow characteristics of the viscous fluid are computed in the presence of cilia and metachronal wave velocity. The effects of several stimulating parameters on the flow and heat transfer are studied in detail through graphs. It is found that symmetry of the velocity profile is broken owing to bending of the channel. The radially varying magnetic field decreases the velocity field, but near the left ciliated wall it induces the opposite behavior. It is also found that velocity profile increases due to increase in buoyancy forces throughout the domain. Numerical consequences for velocity profile are also accessible in the table for diverse values of the physical parameters.

scholarly journals Unsteady flow over an expanding cylinder in a nanofluid containing gyrotactic microorganisms

2016 ◽  
Vol 94 (5) ◽  
pp. 466-473 ◽  
Author(s):  
Hui Chen ◽  
Hongxing Liang ◽  
Tianli Xiao ◽  
Heng Du ◽  
Ming Shen
Keyword(s):  
Differential Equations ◽  
Unsteady Flow ◽  
Shooting Method ◽  
Schmidt Number ◽  
Volume Fraction ◽  
Dual Solutions ◽  
Physical Parameters ◽  
Gyrotactic Microorganisms ◽  
Similarity Transformations ◽  
Fifth Order

In this paper, an analysis is made for the unsteady flow due to an expanding cylinder in a nanofluid that contains both nanoparticles and gyrotactic microoganisms with suction. The nonlinear system of partial differential equations is transformed into high-order nonlinear ordinary differential equations using similarity transformations, and then solved numerically using a shooting method with fourth-fifth-order Runge–Kutta integration technique. The influences of significant physical parameters on the distributions of the velocity, temperature, nanoparticle volume fraction, as well as the density of motile microorganisms are graphically presented and discussed in detail. It is found that dual solutions exist for both stretching and shrinking cases and the range of dual solutions increases with the strength of the expansion. The results also indicate that larger bioconvection Peclet number and smaller Schmidt number lead to an increased concentration of microorganisms and thicker boundary layer thickness.

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