Implementation of the Semi Empirical Kinetic Soot Model Within Chemistry Tabulation Framework for Efficient Emissions Predictions in Diesel Engines

Soot prediction for diesel engines is a very important aspect of internal combustion engine emissions research, especially nowadays with very strict emission norms. Computational Fluid Dynamics (CFD) is often used in this research and optimisation of CFD models in terms of a trade-off between accuracy and computational efficiency is essential. This is especially true in the industrial environment where good predictivity is necessary for engine optimisation, but computational power is limited. To investigate soot emissions for Diesel engines, in this work CFD is coupled with chemistry tabulation framework and semi-empirical soot model. The Flamelet Generated Manifold (FGM) combustion model precomputes chemistry using detailed calculations of the 0D homogeneous reactor and then stores the species mass fractions in the table, based on six look-up variables: pressure, temperature, mixture fraction, mixture fraction variance, progress variable and progress variable variance. Data is then retrieved during online CFD simulation, enabling fast execution times while keeping the accuracy of the direct chemistry calculation. In this work, the theory behind the model is discussed as well as implementation in commercial CFD code. Also, soot modelling in the framework of tabulated chemistry is investigated: mathematical model and implementation of the kinetic soot model on the tabulation side is described, and 0D simulation results are used for verification. Then, the model is validated using real-life engine geometry under different operating conditions, where better agreement with experimental measurements is achieved, compared to the standard implementation of the kinetic soot model on the CFD side.

dx.doi.org/10.18081/2333-5106/016-7/253-264

DNA topoisomerases are ubiquitous, enzymes needed to control topological problems encountered during DNA replication, transcription, recombination and maintenance of genomic stability. They proved to be valuable targets for cancer chemotherapy. The seeds alkaloids extract of Rue plant (Peganum harmala L. Zygophyllaceae) were fractioned by high performance liquid chromatography as a suitable technique, HPLC waters company, gradient, Nova-Pak, C18*, 4µm, 3.9x150mm, mobile phase ACN-water pH10.7. Thirty-four separate solution depending on the retention time of eluents. The aim of this study is to investigate the trace compounds relatively and used as inhibitors for the topoisomerase II enzyme, the study the poison and suppressor model inhibitions and the synergy and antagonism activity of fractions. The visicinone, harmine, visicine and harmaline, were (2.86, 0.75, 13.14, and 16.62 mg/100mg of plant powder. The harmine ˃vicicinone˃ harmaline˃ vicicine as enzyme inhibitors. The unknown trace compounds gave the best inhibition relatively, the alkaloid fractions gave higher inhibitory units of fraction effective (FE). Results of seeds alkaloid fractions showed that the FE in state of fraction mixture was 36% inhibitory units, while summation of FE of each fraction alone gave higher level than their mixture, where sum of FE of them was 1229% inhibitory units. The suppressor inhibition model according to highest percent of the remain supercoiled DNA plasmid than production of linear and open nicked circular with high value in F8 (84%), the poisons inhibition model activity according to the highest percent of linear and nicked open circular DNA plasmid with high level in F31 (88%). There are a trace compounds within some fraction but that the effectiveness of inhibitory relatively higher than known compounds (harmine, vicisinone, harmaline, and vicisine), this can be purified and used as somewhat better inhibitors. There is antagonism activity among seed alkaloids fractions. The all fractions showed a poison and a suppressor model inhibition action in varies percentage, the suppressor inhibition appear in high value in F8 (84%), while the poisons inhibition model gave high level in F31 (88%).

Influence of Wall Sub-Cooling on Local Heat Transfer for Forced Convection Condensation of Steam/Air in a Horizontal Tube

For the purpose of analyzing the influence of wall sub-cooling on condensation heat transfer characteristic in the presence of noncondensable gases inside a horizontal tube, experiments for air-cooling and water-cooling at the secondary side outside the condenser tube have been conducted. By comparing the experimental data of different inlet air mass fraction, mixture gases velocity and coolant volume flow rate, the variation of local heat transfer coefficient with wall sub-cooling was obtained. The results show that for annular and wavy flow, the condensation heat transfer coefficient increases with increasing wall sub-cooling but decreases for stratified flow. For annular and wavy flow, the positive influence of wall sub-cooling on condensation heat transfer coefficient is enhanced by the rise of inlet noncondensable gas mass fraction, mixture gases velocity and pressure.

Performance Investigation of Cascade Refrigeration System Using CO2 and Mixtures

This paper presents reports on simulation and comparative analysis of single stage vapor compression refrigeration system and cascade systems using carbon dioxide, hydrocarbons (HCs) and CO2/HCs mixture. Thermodynamic parameters of fluids are given using the software REFPROP 9.0. To select the most suitable HCs, three criteria have been fixed: Tc, Tt and Tb. It is found that the HCs chosen in low-stage are propane, propylene and ethane and those for the high-stage are propane, propylene and isobutane. The fraction mixture in the two loops has been varied and results are compared with single stage and cascade systems using CO2 and R22. The fraction x[Formula: see text] is varied in the two loops. Results are compared for single and cascade systems using CO2 and R22. For the single stage system, we find for xCO2 = 0.5, an improvement of COP of 14% for CO2/propane mixture and 36% for the CO2/propylene mixture. It is found that for xCO2 = 0.3, cascade system using propane/CO2 mixtures presents a COP lower than that of cascade system using pure CO2. About of 70% of unfriendly fluids like CFCs and HCFCs can be replaced with CO2, without affecting the performance of cascade refrigeration systems.

Electrochemical behaviour of 1-{[(3-halophenyl)imino]methyl}-2-naphthol Schiff bases on graphite electrodes

An electrochemical study of the reduction of 1-{[(3-halophenyl)imino]methyl}-2-naphthol compounds on graphite electrodes was carried out. All the compounds were dissolved in a 1:4 (volume fraction) mixture of tetrahydrofuran (THF) and methanol. NaClO4 (0.1 mol L–1) was used as the supporting electrolyte. Cyclic voltammetry, chronoamperometry, constant-potential coulometry (bulk electrolysis), and constant-potential preparative electrolysis were employed. The cyclic voltammetric data revealed that the reduction on graphite was irreversible and followed an EC mechanism. The diffusion coefficients and the number of electrons transferred were determined using the chronoamperometric Cottrell slope and the ultramicro electrode steady-state current. The number of electrons was also determined by bulk electrolysis. The products of the electroreduction were synthesized in milligram quantities by the use of constant-potential preparative electrolysis. These products were purified and characterized by spectroscopic methods. Based on these findings, a mechanism for the electroreduction process is proposed.Key words: electrochemical reduction, hydroxynaphthylideneaniline Schiff bases, cyclic voltammetry, ultramicro electrode.

Generalized Thermohydraulics Module GENFLO for Combining With the PWR Core Melting Model, BWR Recriticality Neutronics Model and Fuel Performance Model

Thermal hydraulic simulation capability for accident conditions is needed at present in VTT in several programs. Traditional thermal hydraulic models are too heavy for simulation in the analysis tasks, where the main emphasis is the rapid neutron dynamics or the core melting. The GENFLO thermal hydraulic model has been developed at VTT for special applications in the combined codes. The basic field equations in GENFLO are for the phase mass, the mixture momentum and phase energy conservation equations. The phase separation is solved with the drift flux model. The basic variables to be solved are the pressure, void fraction, mixture velocity, gas enthalpy, liquid enthalpy, and concentration of non-condensable gas fractions. The validation of the thermohydraulic solution alone includes large break LOCA reflooding experiments and in specific for the severe accident conditions QUENCH tests. In the recriticality analysis the core neutronics is simulated with a two-dimensional transient neutronics code TWODIM. The recriticality with one rapid prompt peak is expected during a severe accident scenario, where the control rods have been melted and ECCS reflooding is started after the depressurization. The GENFLO module simulates the BWR thermohydraulics in this application. The core melting module has been developed for the real time operator training by using the APROS engineering simulators. The core heatup, oxidation, metal and fuel pellet relocation and corium pool formation into the lower plenum are calculated. In this application the GENFLO model simulates the PWR vessel thermohydraulics. In the fuel performance analysis the fuel rod transient behavior is simulated with the FRAPTRAN code. GENFLO simulates the subchannel around a single fuel rod and delivers the heat transfer on the cladding surface for the FRAPTRAN. The transient boundary conditions for the subchannel are transmitted from the system code for operational transient, loss of coolant accidents and anticipated transients without scram. Experiences with the GENFLO code have pointed out that the efforts needed for the code development and its validation can be minimized with this kind of the generalized solution.

Dielectric Relaxation of Three Ethanolamines

Relaxation spectra have been measured at 20°C for mono-, di-and triethanolamine in the pure liquid state and in a 0.6 mole fraction mixture with 1,4-dioxane. The general resemblance to the dielectric behaviour of alcohols and aminoalcohols shows that relaxation is governed by association effects. In this regard, several features point to significantly differing behaviour of the mono compound in comparison with both di-and triethanol­ amine.

Effect of PO2 and Ag on the phase formation of the Bi(Pb)-2223 superconductor

The chemical reactions and the compositional characteristics of liquids which lead to the phase formation of the Bi(Pb)-2223 [(Bi, Pb): Sr: Ca: Cu: O] superconductor have been studied for a precursor composition of Bi1.8Pb0.4Sr2Ca2.2Cu3Ox. The combined techniques of quenching, powder x-ray diffraction, differential thermal/thermogravimetric analysis (DTA/TGA), scanning electron microscopy (SEM), and energy dispersive x-ray spectroscopy (EDS) were used to characterize the subsolidus phases and the presence of liquid. Samples were annealed under purified air and under a volume fraction mixture of 7.5% O2/92.5% Ar. The effects of Ag in both the pure air and the 7.5% O2/92.5% Ar experiments were also studied. Results are discussed with respect to their processing implications.