Title Numeričko modeliranje neidealne detonacije ANFO eksploziva primjenom Wood-Kirkwoodove teorije : doktorski rad Title (english) Numerical modelling of nonideal detonation of ANFO explosive using Wood-Kirkwood's theory : doctoral dissertation Author Barbara Štimac Tumara Mentor Muhamed Sućeska (mentor)Mentor Mario Dobrilović (mentor)Committee member Vječislav Bohanek (predsjednik povjerenstva)Committee member Vinko Škrlec (član povjerenstva)Committee member Emi Govorčin-Bajsić (član povjerenstva)Granter University of Zagreb Defense date and country 2021-07-08, Croatia Scientific / art field, TECHNICAL SCIENCES Universal decimal classificationUDC ) 622 - Mining Abstract Odstupanje ponašanja nekih eksploziva od općeprihvaćene Zeldovich-von Neumann-Döering hidrodinamičke teorije detonacije poznato je pod nazivom „neidealna detonacija“. Fenomen neidealne detonacije izuzetno je važan u području gospodarskih eksploziva, ali isto tako i u području improviziranih eksploziva. Neidealno ponašanje eksploziva posljedica je duljeg trajanja kemijskih reakcija (u usporedbi s idealnim eksplozivima) u zoni kemijskih reakcija, a manifestira se (1) zakrivljenom frontom udarnog vala, (2) nelinearnom ovisnošću brzine detonacije o početnoj gustoći eksploziva, (3) ovisnošću detonacijskih parametara o promjeru naboja i oblozi, (4) velikim kritičnim promjerom, (5) nedovršenim kemijskim reakcijama, tj. oslobođenjem toplinske energije u fazi ekspanzije produkata.
Fenomen neidealne detonacije ANFO eksploziva istraživan je eksperimentalno i putem numeričkog modeliranja. Kroz tri seta eksperimentalnih ispitivanja određena je ovisnost brzine detonacije i radijusa zakrivljenosti fronte detonacijskog vala ANFO eksploziva o promjeru naboja. Određene vrijednosti korištene su kao temelj pri kalibriranju elemenata modela radijalne ekspanzije produkata, te za procjenu vrijednosti konstante brzine reakcije u jednostupanjskom modelu brzine reakcija ovisne o tlaku. Primjenom tehnika termičke analize (DSC i TGA) određeni su kinetički parametri u Arrheniusovom tipu kinetičkog modela.
Numeričko modeliranje neidealne detonacija obavljeno je korištenjem termokemijskog računalnog koda EXPLO5, u koji je ugrađena Wood-Kirkwoodova teorija neidealne detonacije. Validacija rezultata modeliranja obavljena je usporedbom eksperimentalno određene ovisnosti brzine detonacije o promjeru naboja, te dostupnim rezultatima hidrodinamičkog modeliranja. Istražen je utjecaj kinetike kemijskih reakcija na relevantne detonacijske parametre i strukturu zone kemijskih reakcija. Konačni rezultat istraživanje je unaprijeđeni model radijalne ekspanzije i model brzine kemijskih reakcija unutar modela neidealne detonacije, što doprinosi boljem razumijevanju fenomena neidealne detonacije, poglavito razumijevanju strukture zone kemijskih reakcija ANFO eksploziva.
Abstract (english) Detonation can be described as a phenomenon resulting in formation of a self-sustaining detonation wave (shock wave accompanied with a chemical reaction zone) moving with supersonic speed (up to 10 km/s) and extremely high pressure and temperature (up to 40 GPa and 6000 K) in nanoseconds. There are two generally accepted detonation theories based on conservation laws and hydrodynamic flow models: Chapman-Jouguet (CJ) theory, which assumes instantaneous chemical reactions with no chemical reaction zone, and Zeldovich-von Neumann-Doering (ZND) theory, which assumes existence of a chemical reaction zone of definite length and duration time. Improvements in experimental techniques and understanding of energy transfer and kinetics in chemical reaction zone have directly impacted improvements in detonation models and understanding of nonideality.
Nonideal explosives are considered those whose behaviour can not be accurately described with a simple CJ theory. Experimentally obtained detonation velocity and pressure of such explosives are considerably lower than values calculated by CJ theory. On top of that, detonation velocity shows a very high dependence on charge radius and existence of confinement, which is not the case for ideal explosives. Typical example of nonideal explosives is ANFO, one of most used commercial explosives. Main cause of nonideality is relatively long duration of chemical reactions in a chemical reaction zone (in microseconds compared to nanosecond scale observed in ideal explosives) directly resulting in a wide chemical reaction zone (in tens of millimetres). Besides that, these slow chemical reactions also result in other nonideal characteristics such as curves detonation wave front, nonlinear dependence of detonation velocity on initial explosive density, dependence of detonation parameters on charge radius and existence of confinement and partly reacted explosive at the end of a chemical reaction zone.
To satisfactory describe nonideal detonation, nonideal detonation model, used for numerical modelling of nonideal explosive behaviour, has to be based on a nonideal detonation theory, as well as take into account reaction rate law (or chemical kinetics), radial expansion of detonation products and equations of state of unreacted explosive and detonation products. Many scientists have devoted their time to researching nonideal detonation models which would be able to satisfactory and accurately describe the behaviour of highly nonideal explosives such as ANFO. However, there is still no generally accepted nonideal detonation model as there is still up to 50% discrepancy between experimentally measured and theoretically calculated detonation velocity. Other major problems in dealing with numerical modelling of nonideal detonation are reliance on empirical data, use of incomplete equations of state, too simple or too complicated reaction rate laws and complete absence of theoretically based confinement model.
This thesis deals with improvements of nonideal detonation model based on one of the most used nonideal detonation theory, Wood-Kirkwood slightly divergent flow theory, incorporated in EXPLO5 thermochemical code.
Main goals of this thesis are:
• Experimental determination of detonation velocity as a function of explosive charge radius to obtain an analytical link between two parameters, increase the reliability of the model and decrease the future need for empirical input data.
• Development of a reliable and theoretically based temperature and/or pressure-based reaction rate law which can adequately describe ANFO behaviour.
• Experimental determination of curvature radius and development of radial expansion model calibrated with experimental curvature radius data.
Scientific impact of this thesis, other than improvements made to the reaction rate and radial expansion model in nonideal detonation model which make it more predictable, is the contribution to better understanding of chemical reaction zone structure and processes for heterogeneous ANFO explosive.
Keywords
neidealna detonacija
numeričko modeliranje
Wood-Kirkwoodova teorija
EXPLO5
ANFO
model brzine kemijskih reakcija
radijalna ekspanzija
Keywords (english)
nonideal detonation
numerical modelling
Wood-Kirkwood theory
EXPLO5
ANFO
reaction rate law
radial expansion
Language croatian URN:NBN urn:nbn:hr:169:791903 Project Number: IP-2019-04-1618 Study programme Title: Applied Geosciences, Mining and Petroleum Engineering Catalog URL http://katalog.nsk.hr/F/?func=direct&CON_LNG=ZAG&local_base=ZAG01_WEB&doc_number=000692395 Type of resource Text Extent 176 str. ; 30 cm File origin Born digital Access conditions Open access Terms of use Created on 2021-07-27 08:39:54
