INFLUENCE OF POROSITY OF PRESSED SAMPLES OF SUPERFINE ALUMINUM POWDER ON COMBUSTION PARAMETERS

Данная статья посвящена исследованию влияния пористости прессованных таблеток из сверхтонкого порошка алюминия (СТП Al). Определен механизм горения, протекающий в две стадии: первая, медленная, включающая в себя как «кольцевое» горение боковой поверхности, так и параллельное горение концентрическими слоями, вторая стадия объемная, сопровождающаяся резким самопроизвольным увеличением температуры горения и интенсивности свечения. Показано, что увеличение плотности упаковки СТП Al позволяет замедлить процесс окисления алюминия более чем в два раза. Это обусловлено снижением газопроницаемости таблетки и затруднением доступа воздуха вглубь образца. Повышение пористости материала позволяет регулировать процесс нитридообразования за счёт увеличения содержания азота в продуктах при фильтрационном механизме горения, что открывает возможности получения тугоплавких материалов. This article is devoted to the study of the effect of porosity of compressed tablets from ultrafine aluminum powder (STP Al). The combustion mechanism was determined, which proceeds in two stages: the first, slow, which includes both "ring" combustion of the side surface and parallel combustion with concentric layers, the second stage is volumetric, accompanied by a sharp spontaneous increase in the combustion temperature and glow intensity. It has been shown that an increase in the packing density of HFC Al makes it possible to slow down the process of aluminum oxidation by more than two times. This is due to a decrease in the gas permeability of the tablet and the difficulty of air access deep into the sample. An increase in the porosity of the material makes it possible to regulate the process of nitride formation by increasing the nitrogen content in the products during the filtration mechanism of combustion, which opens up the possibility of obtaining refractory materials.

effect of 1Me-3H additive on the explosive force nanothermite systems SnO2/Al and WO3/Al

Нанотермиты рассматриваются как перспективные энергонасыщенные материалы для создания пиротехнических изделий широкого спектра, ввиду их способности горения в тонких слоях, микрограммовых навесках. Однако из-за высокой чувствительности нанотермитов к электрической искре и трению, сильно осложняется их практическое использование, в связи с чем актуален поиск добавок, снижающих чувствительность, но сохраняющих приемлемые параметры взрывчатых характеристик нанотермитных композиций. В качестве таковых добавок целесообразно использовать высокоэнтальпийные вещества, отличающиеся низкой чувствительностью. Одним из таких веществ является 1-метил-3-нитро-1,2,4-триазол (1Ме-3Н). В работе представлены результаты исследования силы взрыва (F) нанотермитных систем на основе оксида олова и алюминия SnO2/Al, оксида вольфрам и алюминия WO3/Al в зависимости от содержания 1Ме-3Н. Исследован ряд составов разной рецептурной компоновки (I и II): в компоновке I – соотношение компонентов в нанотермитной композиции соответствовало максимальной расчетной теплоте взрыва (Q) при заданном содержании 1Ме-3Н; II – соотношение компонентов базовой нанотермитной пары остается неизменным в тройных смесях. В системе SnO2/Al/1Ме-3Н выявлен экстремальный характер зависимости силы взрыва F от концентрации 1Ме-3Н, при этом максимальные значения F наблюдаются при содержании добавки 10 % для обоих рецептурных компоновок: I – F = 163 %; II – F = 160 %. Для системы WO3/Al/1Ме-3Н обоих рассмотренных рецептурных компоновок наблюдается монотонное снижение силы взрыва с ростом содержания1Ме-3Н: при содержании добавки 15 % композиция теряет взрывчатые свойства (F=0 %). Нанотермитная система SnO2/Al/1Ме-3Н, как и ранее изученные CuO/Al/1Ме-3Н, Bi2O3/Al/1Ме-3Н, MoO3/Al/Ме-3Н проявляет экстремальный характер зависимости силы взрыва F от содержания 1Ме-3Н, подтверждая ранее принятые положения о механизме реакционного взаимодействия в нанотермитных композициях с органическими добавками, тогда как для композиции WO3/Al/1Ме-3Н, по-видимому, присущ отличный от принятого механизм горения, требующий дополнительных исследований. Nanothermites are considered as promising energy-saturated materials for the creation of pyrotechnic products of a wide range, due to their ability to burn in thin layers, microgram quantities. However, due to the high sensitivity of nanothermites to electric spark and friction, their use is very difficult, and therefore the search for additives that reduce sensitivity, but retain acceptable parameters of explosive characteristics of nanothermite compositions is relevant. As such additives, it is advisable to highly use enthalpy substances characterized by low sensitivity. One of these substances is 1-methyl-3-nitro-1,2,4-triazole (1Me-3H). The paper presents the results of a study of the explosion force (F) of nanothermite systems based on tin oxide and aluminum SnO2/Al, tungsten oxide and aluminum WO3/Al depending on the content of 1Me-3H. Several compositions of different prescription configuration (I and II) were studied: in the configuration, I - the ratio of components in the nanothermite composition corresponded to the maximum calculated heat of explosion (Q) at a given content of 1Me-3H; II - the ratio of the components of the base nanothermite pair remains unchanged in triple mixtures. In the SnO2/Al/1Me-3H system, the extreme nature of the dependence of the explosion force F on the concentration of 1Me-3H was revealed, while the maximum values of F were observed at an additive content of 10% for both prescription configuration: I - F = 163%; II - F = 160%. For the WO3/Al/1Me-3H system of both considered compounding arrangements, a monotonous decrease in the explosion force with an increase in the content is observed 1Me-3H: with an additive content of 15%, the composition loses explosive properties (F = 0%). The nanothermite system SnO2/Al/1Me-3H, as well as the previously studied CuO/Al/1Me-3H, Bi2O3/Al/1Me-3H, MoO3/Al/Me-3H, exhibits an extreme dependence of the explosion force F on the content of 1Me-3H, confirming the previously accepted provisions on the mechanism of reaction interaction in nanothermite compositions with organic additives, whereas the composition WO3/Al/1ME-3H, apparently, has a different combustion mechanism from the accepted one, requiring additional research.

Pilot Project: Application of Multi-Component Thermal Fluid Stimulation on Shallow Heavy Oil Reservoir in Kazakhstan

Cyclic steam simulation (CSS) was widely used to recover heavy oil in shallow reservoirs in Kazakhstan. In the late stage of CSS in M oilfield, the performance of this CSS project was poor with high water cut and low oil steam ratio (OSR), indicating low economic benefit. The multi-component thermal fluid (MTF) stimulation trial has been conducted there since March 2018 to evaluate the feasibility of this technology. This paper introduces the field experience and the production performance of MTF stimulation. Results are from 32 cycles of MTF stimulations in 23 wells, most of which had completed their 4 cycles of CSS before. MTF technology is based on a high-pressure jet combustion mechanism, generating a mixture of nitrogen, carbon dioxide and vapor (MTF) under a sealed combustion condition. The mixture fluid provides a significant enhancement through a synergistic effect in the reservoir. The soaking and recovery process are the same as the conventional steam stimulation, meanwhile the requirements for completion and wellbore structure are the same as well. By the time of statistic, average cyclic OSR reaches 2.19 from 0.49 of last CSS cycle. Average water cut declines from 90% to 40% and daily oil production rises from 22 bbls to 33 bbls. Free water is almost invisible in the produced fluid, instead, a stable quasi-monophasic flow has been presented even at low temperatures. This effectively increases the fluidity and dilatancy of crude oil, and greatly replenishes the elastic energy of the formation. Meanwhile, with all components injected into the formation, MTF stimulation achieves significant reduction in carbon emissions. Although this is a pilot test, considerable economic benefits have been achieved with the increase of oil production efficiency. MTF stimulation brings an additional profit of USD 4.4 million for the first year under conditions of local material's cost. This successful pilot demonstrates that MTF stimulation may play an important role at late stage of CSS, even it has its own prospect in an initial heavy oil reservoir development. In the meantime, this pilot experience can be used as a reference for other similar reservoirs’ development.

The Effect Mechanisms of Intake Manifold Water Injection on the Emissions of a Natural Gas Engine

NOx is the main emission of lean burn natural gas engine (NGE). Water injection (WI) is an effective method to reduce NOx, which has been widely studied in conventional fuel engine. Currently, there are few researches on the application of WI in NGE. The influences of WI on NGE are not clear. In the paper, the effect mechanisms of WI on the emissions of NGE are studied. Based on the thermodynamic properties of water and the combustion mechanism of natural gas, the emissions generation mechanism of NGE with WI was analyzed. According to the experimental system, the effects of intake manifold water injection (IMWI) on the emissions of a lean burn NGE was carried out. The results show that, with WI, the in-cylinder temperature decreased greatly, which effectively inhibited the formation of thermal NO. Water generated a lot of OH groups, which effectively inhibited the formation of rapid NO. At 1800 rpm and 0.92g/s WI rate, NOx is reduced by 70.4%. OH group could effectively promote CO oxidize to CO2. At 1000 rpm and 0.92g/s WI rate, CO is decreased by 22.2%. However, since the decrease of the total activation energy of combustion reaction, the chain breaking reaction increased, resulting in a significant increase in HC. At 800rpm and 0.92g/s WI rate, HC was increased by 11.6%.

Reduced Combustion Mechanism for Fire with Light Alcohols

The need for sustainable energy has incentivized the use of alternative fuels such as light alcohols. In this work, reduced chemistry mechanisms for the prediction of fires (pool fire, tank fire, and flash fire) for two primary alcohols—methanol and ethanol—were developed, aiming to integrate the detailed kinetic model into the computational fluid dynamics (CFD) model. The model accommodates either the pure reactants and products or other intermediates, including soot precursors (C2H2, C2H4, and C3H3), which were identified via sensitivity and reaction path analyses. The developed reduced mechanism was adopted to predict the burning behavior in a 3D domain and for the estimation of the product distribution. The agreement between the experimental data from the literature and estimations resulting from the analysis performed in this work demonstrates the successful application of this method for the integration of kinetic mechanisms and CFD models, opening to an accurate evaluation of safety scenarios and allowing for the proper design of storage and transportation systems involving light alcohols.