Shock wave propagation through air: a reactive molecular dynamics study

2021 ◽  
Vol 477 (2247) ◽  
pp. 20200676
Author(s):  
S. Pal ◽  
N. Mitra
Keyword(s):  
Shock Compression ◽  
Chemical Species ◽  
Thermodynamic Quantities ◽  
Compression Process ◽  
Gaseous Species ◽  
Dry Air ◽  
Reactive Molecular Dynamics ◽  
High Shock ◽  
Particle Velocities ◽  
Altitude Level

Shock compression of air is observed in numerous situations ranging from explosions to hypersonic vehicle entry into atmosphere. In an effort to develop continuum-based equation of state for air subjected to shock compression, it is necessary to understand the dynamics of the shock compression process with regards to formation of new chemical species in air at the molecular level. With this in perspective, three different models of air (consisting a mixture of O 2 , N 2 and CO 2 gas, with or without H 2 O based on presence of humidity) are subjected to shock compression ranging from 0.5 km s −1 to 5.0 km s −1 particle velocities. Thermodynamic quantities are evaluated to plot Rankine Hugoniot planes for the three different air models: dry air at mean sea level (MSL), humid air at MSL and dry air at high altitude level of 36 000 ft above MSL. It is observed that high shock velocities eventually results in dissociation of gaseous molecules and formation of new gaseous species which has been quantified in the manuscript.

A reactive molecular dynamics study on the anisotropic sensitivity in single crystal α-cyclotetramethylene tetranitramine

RSC Advances ◽  
2015 ◽  
Vol 5 (12) ◽  
pp. 8609-8621 ◽  
Author(s):  
Ting-Ting Zhou ◽  
Yan-Geng Zhang ◽  
Jian-Feng Lou ◽  
Hua-Jie Song ◽  
Feng-Lei Huang
Keyword(s):  
Molecular Dynamics ◽  
Single Crystal ◽  
Shock Compression ◽  
Slip Plane ◽  
Reactive Molecular Dynamics ◽  
Cyclotetramethylene Tetranitramine

Anisotropic sensitivity is related to the different intermolecular steric arrangements across the slip plane induced by shock compression along various orientations.

Shock compression of a perfect gas

1956 ◽  
Vol 1 (4) ◽  
pp. 399-408 ◽  
Author(s):  
Cerda Evans ◽  
Foster Evans
Keyword(s):  
Shock Compression ◽  
Entropy Change ◽  
Rigid Wall ◽  
Adiabatic Process ◽  
Perfect Gas ◽  
Compression Process ◽  
Specific Heats ◽  
Initial Shock ◽  
The One ◽  
Shock Reflections

The compression of a perfect gas between a uniformaly moving piston and a rigid wall is discussed in the one-dimensional case. If the piston moves with a finite speed, it will initiate a shock in the gas which will reflect successively from rigid wall and piston and cause the compression process to deviate from a reversible adiabatic process. Expressions are derived for the relative changes in pressure and density at each shock reflection. Then values of density and pressure after any number of shock reflections are computed relative to their initial values, and, in terms of these, the corresponding values of temperature and entropy, as well as shock speeds, are determined. The limiting value of the entropy change, as the number of reflections goes to infinity, is obtained as a function of the ratio of specific heats of the gas and the strength of the initial shock. Hence it is possible to estimate an upper limit to the deviation of the shock compression process from a reversible adiabatic process. Some illustrative numerical examples are given.

Resistivity behavior of hydrogen and liquid silane at high shock compression

2018 ◽  
Vol 541 ◽  
pp. 89-94
Author(s):  
Yi-Gao Wang ◽  
Fu-Sheng Liu ◽  
Qi-Jun Liu
Keyword(s):  
Shock Compression ◽  
High Shock

scholarly journals Contribution of gaseous and particulate species to droplet solute composition at the Puy de Dôme, France

2003 ◽  
Vol 3 (5) ◽  
pp. 1509-1522 ◽  
Author(s):  
K. Sellegri ◽  
P. Laj ◽  
A. Marinoni ◽  
R. Dupuy ◽  
M. Legrand ◽  
...  
Keyword(s):  
Liquid Phase ◽  
Gas Phase ◽  
Removal Rate ◽  
Chemical Species ◽  
Solute Concentration ◽  
Complex Nature ◽  
Gaseous Species ◽  
Phase Partitioning ◽  
Gas Phases ◽  
Set Up

Abstract. Chemical reactions of dissolved gases in the liquid phase play a key role in atmospheric processes both in the formation of secondary atmospheric compounds and their wet removal rate but also in the regulation of the oxidizing capacity of the troposphere. The behavior of gaseous species and their chemical transformation in clouds are difficult to observe experimentally given the complex nature of clouds. During a winter field campaign at the summit of the Puy de Dôme (central France, 1465 m a.s.l), we have deployed an experimental set-up to provide a quantification of phase partitioning of both organic (CH3COOH, HCOOH, H2C2O4) and inorganic (NH3, HNO3, SO2, HCl) species in clouds. We found that nitric and hydrochloric acids can be considered close to Henry's law equilibrium, within analytical uncertainty and instrumental errors. On another hand, for NH3 and carboxylic acids, dissolution of material from the gas phase is kinetically limited and never reaches the equilibrium predicted by thermodynamics, resulting in significant sub-saturation of the liquid phase. On the contrary, SIV is supersaturated in the liquid phase, in addition to the presence of significant aerosol-derived SVI transferred through nucleation scavenging. Upon droplet evaporation, a significant part of most species, including SIV, tends to efficiently return back into the gas phase. Overall, gas contribution to the droplet solute concentration ranges from at least 48.5 to 98% depending on the chemical species. This is particularly important considering that aerosol scavenging efficiencies are often calculated assuming a negligible gas-phase contribution to the solute concentration. Our study emphasizes the need to account for the in-cloud interaction between particles and gases to provide an adequate modeling of multiphase chemistry systems and its impact on the atmospheric aerosol and gas phases.

Multiple shock compression using a piston of finite weight

1960 ◽  
Vol 8 (2) ◽  
pp. 264-272 ◽  
Author(s):  
D. F. T. Winter
Keyword(s):  
Wind Tunnel ◽  
Shock Waves ◽  
Shock Compression ◽  
Compression Process ◽  
Real Gas ◽  
Hypersonic Wind Tunnel ◽  
Multiple Shock ◽  
Gas Properties

This paper describes a theory for a piston-operated compressor in which shock waves are used to heat the gas being compressed. Detailed calculations are given showing the use of such a compressor to heat air for use in a hypersonic wind tunnel. The effect of real gas properties on the compression process is included in this discussion.

Transport of Gases in Porous Membranes

MRS Bulletin ◽  
1999 ◽  
Vol 24 (3) ◽  
pp. 41-45 ◽  
Author(s):  
Stratis V. Sotirchos ◽  
Vasilis N. Burganos
Keyword(s):  
Pore Space ◽  
Chemical Species ◽  
Molecular Size ◽  
Porous Membrane ◽  
Transport Processes ◽  
Porous Membranes ◽  
Gaseous Species ◽  
Interior Space ◽  
Separation Processes ◽  
Membrane Pore

The capability of membranes to affect differently, both qualitatively and quantitatively, the transport rates of chemical species of dissimilar chemical structure through their interior space renders them attractive for use in many separation problems. Extensive research efforts have thus been undertaken on the preparation and characterization of membrane materials and the study of the transport processes involved in their use in separation applications. The study of the transport of gaseous species through the pore space of porous membranes and the analysis and understanding of the mechanisms that are involved in this process are a very important, if not the most important, element in the development of membranebased separation processes.The resistance that a gaseous species encounters as it is transported through the pore space of a porous membrane is a function of its molecular properties, of its interaction with the material that makes up the walls of the pores, and of the membrane pore structure. Gaseous transport in pores can take place through various mechanisms, whose contribution to the overall transport rate of a particular species is, in general, determined by the strength of the interactions of the molecules of that species with the pore walls and by the relative magnitudes of three length scales that characterize the molecular size, the distance between pore walls, and the density of the fluid in the pore space.

scholarly journals Thermodynamic modelling of the lead sintering roasting process

2019 ◽  
Vol 55 (1) ◽  
pp. 21-29
Author(s):  
Sánchez Rojas ◽  
Romero Serrano ◽  
Hernández Ramírez ◽  
Rodríguez López ◽  
Guzmán Almaguer ◽  
...  
Keyword(s):  
Gas Flow ◽  
Chemical Species ◽  
Packed Bed ◽  
Operating Conditions ◽  
Sintering Process ◽  
Gaseous Species ◽  
Proposed Model ◽  
Roasting Process ◽  
Simulation Strategy ◽  
Experimental Trials

This work proposes a simulation strategy of the lead sintering process assuming that it takes place in a horizontally moving packed bed with transverse air flow. Some local chemical reactions occur at rates that depend on the temperature, and chemical species formed in one volume stage will flow for further reaction in other stages. To simulate this process, the model reactor is divided into a number of sequential stages. Condensed species flow horizontally, and gaseous species leave each stage vertically. The compositions and temperatures of the species are calculated considering that the local thermodynamic equilibrium is reached in each stage without external heat transfer, apart from the gas flow, before moving on to the next stage. The model calculates the temperature profile along the sintering machine, the compositions of the sinter and the exhaust gas. The results of the proposed model were compared with sinter pot experimental trials and a reasonably good agreement was obtained. This model can be used to optimize the operating conditions of the lead sintering process.

scholarly journals Regularized machine learning on molecular graph model explains systematic error in DFT enthalpies

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Himaghna Bhattacharjee ◽  
Nikolaos Anesiadis ◽  
Dionisios G. Vlachos
Keyword(s):  
Gas Phase ◽  
Density Functional ◽  
Statistical Tests ◽  
Molecular Graph ◽  
Chemical Species ◽  
Graph Model ◽  
Basis Set ◽  
Gaseous Species ◽  
Elementary Reactions ◽  
Gas Phase Molecules

AbstractA major goal of materials research is the discovery of novel and efficient heterogeneous catalysts for various chemical processes. In such studies, the candidate catalyst material is modeled using tens to thousands of chemical species and elementary reactions. Density Functional Theory (DFT) is widely used to calculate the thermochemistry of these species which might be surface species or gas-phase molecules. The use of an approximate exchange correlation functional in the DFT framework introduces an important source of error in such models. This is especially true in the calculation of gas phase molecules whose thermochemistry is calculated using the same planewave basis set as the rest of the surface mechanism. Unfortunately, the nature and magnitude of these errors is unknown for most practical molecules. Here, we investigate the error in the enthalpy of formation for 1676 gaseous species using two different DFT levels of theory and the ‘ground truth values’ obtained from the NIST database. We featurize molecules using graph theory. We use a regularized algorithm to discover a sparse model of the error and identify important molecular fragments that drive this error. The model is robust to rigorous statistical tests and is used to correct DFT thermochemistry, achieving more than an order of magnitude improvement.

scholarly journals Extension of a gaseous dry deposition algorithm to oxidized volatile organic compounds and hydrogen cyanide for application in chemistry transport models

2021 ◽  
Vol 14 (8) ◽  
pp. 5093-5105
Author(s):  
Zhiyong Wu ◽  
Leiming Zhang ◽  
John T. Walker ◽  
Paul A. Makar ◽  
Judith A. Perlinger ◽  
...  
Keyword(s):  
Volatile Organic Compounds ◽  
Organic Compounds ◽  
Dry Deposition ◽  
Hydrogen Cyanide ◽  
Chemical Species ◽  
Model Parameters ◽  
Gaseous Species ◽  
Transport Models ◽  
Southeastern Us ◽  
Volatile Organic

Abstract. The dry deposition process refers to flux loss of an atmospheric pollutant due to uptake of the pollutant by the Earth's surfaces, including vegetation, underlying soil, and any other surface types. In chemistry transport models (CTMs), the dry deposition flux of a chemical species is typically calculated as the product of its surface layer concentration and its dry deposition velocity (Vd); the latter is a variable that needs to be highly empirically parameterized due to too many meteorological, biological, and chemical factors affecting this process. The gaseous dry deposition scheme of Zhang et al. (2003) parameterizes Vd for 31 inorganic and organic gaseous species. The present study extends the scheme of Zhang et al. (2003) to include an additional 12 oxidized volatile organic compounds (oVOCs) and hydrogen cyanide (HCN), while keeping the original model structure and formulas, to meet the demand of CTMs with increasing complexity. Model parameters for these additional chemical species are empirically chosen based on their physicochemical properties, namely the effective Henry's law constants and oxidizing capacities. Modeled Vd values are compared against field flux measurements over a mixed forest in the southeastern US during June 2013. The model captures the basic features of the diel cycles of the observed Vd. Modeled Vd values are comparable to the measurements for most of the oVOCs at night. However, modeled Vd values are mostly around 1 cm s−1 during daytime, which is much smaller than the observed daytime maxima of 2–5 cm s−1. Analysis of the individual resistance terms and uptake pathways suggests that flux divergence due to fast atmospheric chemical reactions near the canopy was likely the main cause of the large model–measurement discrepancies during daytime. The extended dry deposition scheme likely provides conservative Vd values for many oVOCs. While higher Vd values and bidirectional fluxes can be simulated by coupling key atmospheric chemical processes into the dry deposition scheme, we suggest that more experimental evidence of high oVOC Vd values at additional sites is required to confirm the broader applicability of the high values studied here. The underlying processes leading to high measured oVOC Vd values require further investigation.

scholarly journals Study of Atkinson cycle in two-stroke diesel engine with opposed pistons

2019 ◽  
Vol 178 (3) ◽  
pp. 121-128
Author(s):  
Wladyslaw MITIANIEC
Keyword(s):  
Diesel Engine ◽  
Power Plant ◽  
Model Simulation ◽  
Combustion Process ◽  
Chemical Species ◽  
Total Efficiency ◽  
Cfd Modelling ◽  
Compression Process ◽  
Atkinson Cycle ◽  
Working Parameters

The paper presents possibilities of change working parameters of two-stroke diesel engine with opposed pistons. Obtaining of higher engine efficiency is realized by applying of Atkinson cycle. Modification of scavenging process by changing pistons position connecting with two crankshafts enables asymmetrical scavenge timing. Decreasing of shorter time of closing exhaust ports before compression process and longer expansion process give higher engine work and with high charging ratio increases engine power. These types of engines are recently recommended for power plant stations. The paper includes full analysis of engine work with scavenge and combus-tion processes for different timing phases based on geometry of the CI Leyland L60 engine by using of CFD modelling and own 0D model. Simulation tests indicate a high scavenge efficiency, good penetration of injected fuel and fast combustion process. The work contains figures of pressure, temperature traces and emission of main chemical species in exhaust gases with comparison of engine works for different timing phases. Atkinson cycle in two-cycle work of engine and full combustion process enables to achieve high total efficiency. The study is an input for realization of such processes in a future of power plant engines with different fuelling systems.

Sign in / Sign up

Export Citation Format

Share Document