Papers by Keyword: Detonation

Abstract: The relationship between substance characteristic temperatures: autoignition, melting, flash, boiling is demonstrated and analyzed. Based on the oscillatory and step changes presence, a conclusion was made about the supramolecular structures presence and periodicity in the n-alkanes homologous series. A method for modeling equivalent lengths of peroxide supramolecular structures for predicting the explosion and fire hazard parameters of n-alkanes is proposed. An approximation dependence was developed for predicting autoignition temperatures t_ai of n-alkanes. It is shown that stoichiometric concentrations of the various supramolecular peroxide structures formation accord to different flammability and explosion limits. A correlation between t_ai and Anti-Knock Index (AKI) was established. An approximation dependence was developed for predicting n-alkanes AKI. The detonation propensity index К_D was introduced based on cluster supramolecular structures modeling and melting temperatures. It is shown that К_D indicator correlates with the n-alkanes AKI and with the explosives detonation velocity. The possibility of taking into account during calculations the supramolecular structures presence at the combustion stage confirms their existence.

Abstract: High Explosive Mortar bombs are used on the battlefield for destroying the manpower, non-armoured equipment and shelters. The paper describes an original experimental and numerical approach regarding the potential threats caused by the detonation of 120 mm HE mortar bombs. The evaluation of the bomb effect presumes the fulfillment of experimental trials that focus on two physical mechanisms which appear after the detonation of the cased high explosive. These mechanisms are the shock wave generation and the fragments propulsion, which were also studied by a numerical model that provides results over the bomb fragmentation mode. The novelty of the paper consists in the calibrated 3D numerical model confirmed by the experimental data, which provides information over the fragmentation process of the case and the initial velocity of its fragments, proving that the main threat of this type of ammunition is the effect through metal fragments. The results of numerical simulation and experimental data are used for their comparative analysis and the assessment of the phenomena.

Abstract: The scientific study of detonation stretches over a century and the potential to harness detonations for propulsion and power was recognized for almost as long. It is only in the past two decades that detonation applications have received intense attention. Attractions for utilizing detonations include the higher theoretical thermodynamic efficiency compared to deflagration-based systems, high power-to-weight or volume ratio and lack of moving parts. Despite these attractive features, a number of fundamental physics and engineering challenges must be overcome before such systems can be practical. Some of these include the ability to achieve consistent and reliable detonations in a practical arrangement, understanding of the unsteadiness, and integration with ancillary systems. Illustrations will be provided on how some of these issues were understood and overcome. Potential challenges are also highlighted.

Abstract: In conventional charge structure, the shell of charge’s containment is normally closed, with no explosive. When initiating charge, shell expanding to the outward, rupturing and eventually spreading out which was driven by the charge, this don’ have a guiding role to the detonation product flow. To further enhance the control of charge’s detonation product and energy flow, realizing the effective use of detonation products. The thesis put forward a structure design of filling thin-layer explosive in multi-layer shell, by initiating thin-layer explosive to control the deformation of shell, obtaining a approximately function with Laval Nozzle structure which can control the gas product when charge detonation. The thesis put forward a structure that including multi-layer explosive shell, establishing a numerical simulation model. Analysis the difference of shell’ deformation on different initiation method, provides a design references for further engineering application.

Abstract: when detonation wave is spreading in cylindrical charge which has a shell constraint, the border of the shell will reflect the detonation wave, reflection wave still has a strong influence on charge’s centerline. Compared with cylindrical charge, the influence of variable-section charge’s stack reflection wave on centerline is unsteady, relating to the gradual trends height of section area. On the condition of end-point detonation, doing the numerical simulation on detonation process of equal-section charge 、reduced-increased charge and increased-reduced charge, analyzing the pressure and velocity of detonation products on position of centerline, founding in the range of gradually decreasing section al, detonation wave through reflecting and then occur oblique collision that induce the pressure increasing rapidly. Doing the numerical simulation on variable-section charge’s detonation, promoting the understand of the reflection wave mechanism and the velocity of detonation product, this can be a practical significance to further improve the charge structure design and realize the efficient utilization of detonation energy.

Abstract: Turbochargers are an integral part of today’s modern diesel engines and are a major reason that they are able to produce more power. Unlike a super charger that is driven via a belt from the engine, a turbo takes the exhaust that the engine is producing and puts it to good use. As Turbochargers are driven by exhaust, heat is an unwelcome by product and something that wasn’t really taken into account in automobiles. Then those intercoolers started to come into play in turbocharged automobiles. The forced air produced by the turbocharger is routed through the intercooler where its temperature is reduced before reaching the engine. The use of intercoolers has made turbocharged vehicles far more reliable and, in the case of today’s heavy duty diesel trucks, is a very important component. The inlet air of an IC engine from turbocharger temperature is very much high (due to compression) means oxygen content is very much less. And also air with high temperature causes pre-ignition and detonation. So fuel combustion does not take place properly. Inter Cooling of inlet air is very much essential according to performance point of view. Turbo intercoolers are used for cooling the inlet air of an IC engine from turbo chargers. Moreover cooling of air makes it denser and contributes for better combustion and more power they are mounted close to the radiators for achieving lower air temperature. This arrangement affects the performance of both. So in this project an attempt will be made to increase the efficiency of the turbo intercooler arrangement through design modification and repositioning of intercooler by taking the TATA MARCOPOLO-Star Bus 909 as a reference.

Abstract: In this paper experimental research on rotating detonation carried out at the Institute of Aviation (IA) in Warsaw are presented. Research was focused on 3-D numerical simulations of detonation propagation in cylindrical chambers and on evaluation of conditions at which rotating detonation is propagating in cylindrical channels for kerosene-hydrogen-air mixtures. Conducted simulations are used for analysis of complex flow – detonation front interaction and for estimating the thermodynamic parameters of the outflow gases. Extensive research on continuously propagating rotating detonation in many different chambers and in different fuel-air mixtures were tested. On bases of conducted calculations, as well as results of experimental study, a few chamber were selected for tests with GTD-350 engine. It was shown that application of the continuously rotating detonation to GTD-350 engine can results with increased efficiency of the engine.

Abstract: Detonation combustion wave is much more energetic combustion process in pulse detonation engine combustion system. Numerous experimental, theoretical and numerical analyses have been studied in pulse detonation engine to implement in practical propulsion system. In this present computational study the simulation was carried out for deflagration flame acceleration and deflagration to detonation transition of hydrogen air combustible mixture inside the detonation tube with and without Shchelkin spiral. A three dimensional computational analysis has been done by finite volume discretization method using ANSYS Fluent 14 CFD commercial software. The LES turbulence model with second order upwind discretization scheme was adopted with standard boundary conditions for unsteady combustion wave simulations. From the computational study it was found that intensity of detonation wave velocity and dynamic pressure is higher near to the boundary of Shchelkin spiral in detonation tube. The contour plots comparisons clearly show that deflagration flame accelerates in detonation tube as present of Shchelkin spiral. The contour plots also suggest that deflagration flame velocity and pressure are less in without Shchelkin spiral in detonation tube. The accelerating detonation waves are approximately near about Chapment-Jouguet values in detonation tube with Shchelkin spiral.

Abstract: Multi-chamber detonation sprayer (MCDS) was applied for deposition of WC-Co-Cr powder coatings on corrosion-resistant steel. Powder AMPERIT®554.074 WC-Co-Cr was used to deposit of a coatings. The coatings microstructures and phase compositions were characterized using SEM, OM and XRD techniques. Measurement of the microhardness of samples was done with a micro-hardness tester DM – 8B using a Vickers’s indenter with load on of 0.3 N. It was established that MCDS has provided the conditions for formation of a dense layer with porosity of less than 1.5 % and microhardness 750±50 HV_0.3.

Abstract: In this study, a multi-chamber detonation sprayer (MCDS) was applied for deposition of Co-Cr-Al-Y powder coatings (200-250 mm thick) on nickel base superalloy JS6U (Russia). Powder Co-25Cr-11Al-1Y (d(0.1): 6.6 μm, d(0.5): 62.7 μm, d(0.9): 123,4 μm) was used to deposit of a coatings. The coatings microstructures and phase compositions were characterized using SEM, OM and XRD techniques. Measurement of the microhardness of samples was done with a micro-hardness tester DM – 8B using a Vickers’s indenter with load on of 0.1 N. It was established that MCDS has provided the conditions for formation of a dense layer with porosity 0.05% and microhardness 600±50 HV_0.1.