A Numerical Study to Investigate the Effect of Syngas Composition and Compression Ratio on the Combustion and Emission Characteristics of a Syngas-Fueled HCCI Engine

2020 ◽  
Vol 142 (9) ◽  
Author(s):  
Kabbir Ali ◽  
Changup Kim ◽  
Yonggyu Lee ◽  
Seungmook Oh ◽  
Kiseong Kim
Keyword(s):  
Compression Ratio ◽  
Consumption Rate ◽  
Volume Fraction ◽  
Numerical Study ◽  
Load Condition ◽  
Fuel Mixture ◽  
Peak Temperature ◽  
Dominant Factor ◽  
Temperature Range ◽  
Hcci Engine

Abstract The purpose of this work is to investigate syngas composition (of constituents H2, CO, and CO2) and compression ratio (CR) effects on the combustion and emissions characteristics of a syngas-fueled homogenous charge compression ignition (HCCI) engine, which operates in very lean air–fuel mixture conditions for power plant usage. Investigations were conducted using ansys forte cfd package at low (3 bar indicated mean effective pressure (IMEP)) and medium (5 bar IMEP) loads, and the calculated results were compared with the Aceves et al.’s multi-zone HCCI model, using the same chemical kinetics set (Gas Research Institute (GRI)-Mech3.0). All calculations were carried out at maximum brake torque (MBT) conditions by sweeping the air–fuel mixture temperature at intake valve closing (IVC) (TIVC).This study found out that the H2 consumption rate is slightly high in a low-temperature range in the early period of combustion while the CO consumption rate is high in a high-temperature range in the later period of combustion. The results reveal that the change of H2 /CO ratio and inert gas volume fraction according to fuel composition affects combustion, but the TIVC is the dominant factor affecting combustion phasing at MBT conditions. For each fuel and load condition, the TIVC was significantly reduced with the increase of CR (17.1–22.3) to get MBT conditions, which causes to retard combustion phasing and lowers in-cylinder peak temperature. The oxides of nitrogen (NOx) emissions reduced with increasing the CR due to the lowering of the in-cylinder peak temperature.

A comparative numerical study of the combustion performance of the syngas-fueled HCCI engine using a toroidal piston, square bowl piston, and flat piston shape at different loads

2021 ◽  
pp. 1-27
Author(s):  
Kabbir Ali ◽  
Changup Kim ◽  
Yonggyu Lee ◽  
Seungmook Oh ◽  
Ki-Seong Kim
Keyword(s):  
Numerical Study ◽  
Pressure Rise ◽  
Fuel Mixture ◽  
Combustion Efficiency ◽  
Maximum Pressure ◽  
Cross Sectional ◽  
Combustion Performance ◽  
Hcci Engine ◽  
Heat Loss Rate ◽  
Piston Bowl

Abstract This study analyzes the combustion performance of a syngas-fueled homogenous charge compression ignition (HCCI) engine using a toroidal piston, square bowl, and flat piston shape, at low, medium, and high loads, with a constant compression ratio of 17.1. In this study, the square bowl shape is optimized by reducing the piston bowl depth and squish area ratio (squish area/cylinder cross-sectional area) from (34 to 20, 10, and 2.5) %, and compared with the flat piston shape and toroidal piston shape. This HCCI engine operates under an overly lean air–fuel mixture condition for power plant usage. ANSYS Forte CFD with GRI Mech3.0 chemical kinetics is used for combustion analysis, and the calculated results are validated by the experimental results. All simulations are accomplished at maximum brake torque (MBT) by altering the air–fuel mixture temperature at IVC with a constant equivalence ratio of 0.27. This study reveals that the main factors that affect the start of combustion , maximum pressure rise rate (MPRR), combustion efficiency, and thermal efficiency by changing the piston shape are the squish flow and reverse squish flow effects. Therefore, the square bowl piston D is the optimized piston shape that offers low MPRR and high combustion performance for the syngas-fueled HCCI engine, due to the weak squish flow and low heat loss rate through the combustion chamber wall, respectively, compared to the other piston shapes of square bowl piston A, B, and C, flat piston, and toroidal (baseline) piston shape.

A Numerical Study to Control the Combustion Performance of a Syngas-Fueled HCCI Engine at Medium and High Loads Using Different Piston Bowl Geometry and Exhaust Gas Recirculation

2020 ◽  
Vol 143 (8) ◽  
Author(s):  
Kabbir Ali ◽  
Changup Kim ◽  
Yonggyu Lee ◽  
Seungmook Oh ◽  
Kiseong Kim
Keyword(s):  
Numerical Study ◽  
Combustion Process ◽  
Pressure Rise ◽  
Fuel Mixture ◽  
Exhaust Gas Recirculation ◽  
Maximum Pressure ◽  
Exhaust Gas ◽  
Hcci Engine ◽  
Piston Bowl ◽  
Gas Recirculation

Abstract This study aims to analyze the effect of piston bowl geometry on the combustion and emission performance of the syngas-fueled homogenous charge compression ignition (HCCI) engine, which operates under lean air–fuel mixture conditions for power plant usage. Three different piston bowl geometries were used with a reduction of piston bowl depth and squish area ratio of the baseline piston bowl with the same compression ratio of 17.1. Additionally, exhaust gas recirculation (EGR) is used to control the maximum pressure rise rate (MPRR) of syngas-fueled HCCI engines. To simulate the combustion process at medium load (5 bar indicated mean effective pressure (IMEP)) and high loads of (8 and 10 bar IMEP), ansys forte cfd package was used, and the calculated results were compared with Aceves et al.’s Multi-zone HCCI model, using the same chemical kinetics set (Gri-Mech 3.0). All calculations were accomplished at maximum brake torque (MBT) conditions, by sweeping the air–fuel mixture temperature at the inlet valve close (TIVC). This study reveals that the TIVC of the air–fuel mixture and the heat loss rate through the wall are the main factors that influence combustion phasing by changing the piston bowl geometry. It also finds that although pistons B and C give high thermal efficiency, they cannot be used for the combustion process, due to the very high MPRR and NOx emissions. Even though the baseline piston shows high MPRR (23 bar/degree), it is reduced, and reveals an acceptable range of 10–12 bar/degree, using 30% EGR.

Effect of No-load and Load Condition on Transformer Sound

2018 ◽  
pp. 11-15
Author(s):  
Dr. Hitesh Paghadar
Keyword(s):  
Experimental Study ◽  
Power Transformer ◽  
Load Condition ◽  
Noise Pollution ◽  
Sound Level ◽  
Measurement Scale ◽  
Dominant Factor ◽  
Public Attention ◽  
Level Measurement ◽  
Human Ear

Increasing environment noise pollution is a matter of great concern and of late has been attracting public attention. Sound produces the minute oscillatory changes in air pressure and is audible to the human ear when in the frequency range of 20Hz to 20 kHz. The chief sources of audible sound are the magnetic circuit of transformer which produces sound due to magnetostriction phenomenon, vibration of windings, tank and other structural parts, and the noise produced by cooling equipments. This paper presents the validation for sound level measurement scale, why A-weighted scale is accepted for sound level measurement, experimental study carried out on 10MVA Power Transformer. Also presents the outcomes of comparison between No-Load sound & Load sound level measurement, experimental study carried out on different transformer like - 10MVA, 50MVA, 100MVA Power Transformer, to define the dominant factor of transformer sound generation.

scholarly journals Numerical Study on an Interface Compression Method for the Volume of Fluid Approach

Fluids ◽  
2021 ◽  
Vol 6 (2) ◽  
pp. 80
Author(s):  
Yuria Okagaki ◽  
Taisuke Yonomoto ◽  
Masahiro Ishigaki ◽  
Yoshiyasu Hirose
Keyword(s):  
Linear Theory ◽  
Volume Fraction ◽  
Numerical Study ◽  
Volume Of Fluid ◽  
Interfacial Wave ◽  
Validation Process ◽  
Two Phase ◽  
Numerical Diffusion ◽  
Mesh Resolution ◽  
Water Reactors

Many thermohydraulic issues about the safety of light water reactors are related to complicated two-phase flow phenomena. In these phenomena, computational fluid dynamics (CFD) analysis using the volume of fluid (VOF) method causes numerical diffusion generated by the first-order upwind scheme used in the convection term of the volume fraction equation. Thus, in this study, we focused on an interface compression (IC) method for such a VOF approach; this technique prevents numerical diffusion issues and maintains boundedness and conservation with negative diffusion. First, on a sufficiently high mesh resolution and without the IC method, the validation process was considered by comparing the amplitude growth of the interfacial wave between a two-dimensional gas sheet and a quiescent liquid using the linear theory. The disturbance growth rates were consistent with the linear theory, and the validation process was considered appropriate. Then, this validation process confirmed the effects of the IC method on numerical diffusion, and we derived the optimum value of the IC coefficient, which is the parameter that controls the numerical diffusion.

Dynamic Study on Vacuum Pyrolysis Reaction of Chinese Fir Sawdust Biomass

2012 ◽  
Vol 512-515 ◽  
pp. 375-378
Author(s):  
Su Wen Yang ◽  
Jian Min Yi ◽  
Ke Qiang Qiu ◽  
Xin Deng ◽  
Jian Shan Chen
Keyword(s):  
Heating Rate ◽  
Free Water ◽  
Chinese Fir ◽  
Peak Temperature ◽  
Gravimetric Analysis ◽  
Water Desorption ◽  
Exponential Factor ◽  
Pyrolysis Reaction ◽  
Temperature Range ◽  
Vacuum Pyrolysis

This thesis does thermal gravimetric analysis（TGA）studies on Chinese fir sawdust biomass by integrated thermal analyzer under vacuum conditions. Through the analysis on lostmass curve at different heating rate of 10, 15, 20 and 30°C/min, we found the process of Chinese fir sawdust vacuum pyrolysis can be mainly divided into three stages: evaporation of free water and combined water desorption, rapid lostmass of pyrolysis and slow decomposition of residues. The lostmass major temperature range is between 250 ~ 450°C, the peak temperature is between 365 ~ 400°C. When the pyrolysis temperature is 500°C, vacuum pyrolysis reaction of Chinese fir sawdust has basically completed. As the heating rate rises, the lostmass curve is moving to the right, the peak temperature is shifting to higher temperature, and the temperature range of thermal decomposition reaction widens significantly. According to experimental datas, we tried to obtain the vacuum pyrolysis dynamic parameters of Chinese fir sawdust, and the results are that the apparent activation energy of vacuum pyrolysis reaction of Chinese fir sawdust biomass is 128.34kJ/mol, with the pre-exponential factor being 6.42×109 and reaction order being 1.08, similar to first order reaction.

A Parametric Numerical Study of Radiative Transfer in Thermotropic Materials

2013 ◽  
Author(s):  
Adam C. Gladen ◽  
Susan C. Mantell ◽  
Jane H. Davidson
Keyword(s):  
Particle Size ◽  
Radiative Transfer ◽  
Optical Thickness ◽  
Parametric Study ◽  
Volume Fraction ◽  
Numerical Study ◽  
Anisotropic Scattering ◽  
Index Of Refraction ◽  
Spherical Particles ◽  
Size Parameter

A thermotropic material is modeled as an absorbing, thin slab containing anisotropic scattering, monodisperse, spherical particles. Monte Carlo ray tracing is used to solve the governing equation of radiative transfer. Predicted results are validated by comparison to the measured normal-hemispherical reflectance and transmittance of samples with various volume fraction and relative index of refraction. A parametric study elucidates the effects of particle size parameter, scattering albedo, and optical thickness on the normal-hemispherical transmittance, reflectance, and absorptance. The results are interpreted for a thermotropic material used for overheat protection of a polymer solar absorber. For the preferred particle size parameter of 2, the optical thickness should be less than 0.3 to ensure high transmittance in the clear state. To significantly reduce the transmittance and increase the reflectance in the translucent state, the optical thickness should be greater than 2.5 and the scattering albedo should be greater than 0.995. For optical thickness greater than 5, the reflectance is asymptotic and any further reduction in transmittance is through increased absorptance. A case study is used to illustrate how the parametric study can be used to guide the design of thermotropic materials. Low molecular weighted polyethylene in poly(methyl methacrylate) is identified as a potential thermotropic material. For this material and a particle radius of 200 nm, it is determined that the volume fraction and thickness should equal 10% and 1 mm, respectively.

AN APPARATUS FOR COMPARISON OF THERMOCOUPLES

1955 ◽  
Vol 33 (6) ◽  
pp. 275-285 ◽  
Author(s):  
T. M. Dauphinee
Keyword(s):  
Peak Temperature ◽  
Tube Furnace ◽  
Furnace Temperature ◽  
Temperature Range ◽  
Different Types

This paper describes a semiautomatic apparatus for routine or precision comparisons of thermocouples of the same type in the temperature range 0–1100 °C. The couples being compared are welded together at the tips and placed in a tube furnace which is heated at rates varying from 10 to 100 °C./min. Measurements of carefully annealed thermocouples show that in the temperature range 300–1100 °C. platinum – platinum 10% rhodium thermocouple comparisons may be made to accuracies of ± 0.3 μv. (± 0.03 °C.) at heating velocities as great as 15 °C./min. while accuracies of ± 1.5 μv. at velocities of 100 °C./min. are feasible. The furnace temperature is varied by means of a motor-driven variac with automatic reversal at peak temperature. In addition to this standard comparison procedure, provision is made for comparing corresponding elements of the couples, for suppression of all or part of the measured e.m.f., and for measuring the whole e.m.f. of all couples when a comparison of different types is desired. The system can be adapted to XY recording with total e.m.f. plotted against e.m.f. differences.

Numerical Simulation of Heat Transfer in Laminar Natural Convection of Mixed Newtonian-Non-Newtonian and Pure Non-Newtonian Nanofluids in a Square Enclosure

2021 ◽  
pp. 1-44
Author(s):  
Ajay Vallabh ◽  
P.S. Ghoshdastidar
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Base Fluid ◽  
Volume Fraction ◽  
Numerical Study ◽  
Transfer Model ◽  
Nanoparticle Concentration ◽  
Left Wall ◽  
Square Enclosure ◽  
First Case

Abstract This paper presents a steady-state heat transfer model for the natural convection of mixed Newtonian-Non-Newtonian (Alumina-Water) and pure Non-Newtonian (Alumina-0.5 wt% Carboxymethyl Cellulose (CMC)/Water) nanofluids in a square enclosure with adiabatic horizontal walls and isothermal vertical walls, the left wall being hot and the right wall cold. In the first case the nanofluid changes its Newtonian character to Non-Newtonian past 2.78% volume fraction of the nanoparticles. In the second case the base fluid itself is Non-Newtonian and the nanofluid behaves as a pure Non-Newtonian fluid. The power-law viscosity model has been adopted for the non-Newtonian nanofluids. A finite-difference based numerical study with the Stream function-Vorticity-Temperature formulation has been carried out. The homogeneous flow model has been used for modelling the nanofluids. The present results have been extensively validated with earlier works. In Case I the results indicate that Alumina-Water nanofluid shows 4% enhancement in heat transfer at 2.78% nanoparticle concentration. Following that there is a sharp decline in heat transfer with respect to that in base fluid for nanoparticle volume fractions equal to and greater than 3%. In Case II Alumina-CMC/Water nanofluid shows 17% deterioration in heat transfer with respect to that in base fluid at 1.5% nanoparticle concentration. An enhancement in heat transfer is observed for increase in hot wall temperature at a fixed volume fraction of nanoparticles, for both types of nanofluid.

Mechanical And Superconducting Properties Of Cu-Nb3Sn In Situ Produced Composite Wires

1981 ◽  
Vol 12 ◽  
Author(s):  
A. Kolb-Telieps ◽  
B.L. Mordike ◽  
M. Mrowiec
Keyword(s):  
Mechanical Properties ◽  
Tensile Strength ◽  
Yield Strength ◽  
Wide Temperature Range ◽  
Volume Fraction ◽  
Superconducting Properties ◽  
Temperature Range ◽  
Composite Wires ◽  
Strength And Ductility

ABSTRACTCu-Nb composite wires were produced from powder, electrolytically coated with tin and annealed to convert the Nb fibres to Nb 3Sn. The content was varied between 10 wt % and 40 wt %. The superconducting properties of the wires were determined. The mechanical properties, tensile strength, yield strength and ductility were measured as a function of volume fraction and deformation over a wide temperature range. The results are compared with those for wires produced by different techniques.

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