D. I. Baklanov

Transition of combustion into detonation within a channel with the diameter less than the critical diameter of the existence of stationary detonation

An experimental investigation was carried out for transition of combustion into detonation of oxygen-hydrogen and hydrogen-air stoichiometric mixtures within a cylindrical channel with a diameter of 3 mm, which is less than the critical diameter of the existence of stationary detonation in the hydrogen-air mixture. To realize the transition of combustion into detonation in the channel, the combustible mixture was ignited within a precombustion chamber with a diameter of 14.5 mm which was arranged in line with the channel on one of its faces. The expanding products of mixture combustion within the precombustion chamber accelerate the flame front at the input of the channel, thus increasing the energy amount released during mixture combustion within the narrow channel per unit time. As a result, the ratio of the burning energy to dissipative losses in channel walls increases, which makes transition into detonation realizable. The use of the precombustion chamber allowed us to obtain the transition of combustion into the detonation wave with the Chapman-Jouguet parameters at initial mixture pressures of 1 and 2 atm. The effect of the size of the turbulizing precombustion chamber on the length of the transition of combustion into detonation is analyzed, and the average velocities of flame front propagation along the channel are determined.

Inhibition of Developed Detonation of Hydrogen–Air Mixtures

We have shown [1–3] that, in gas-phase ignition and combustion of hydrogen-containing and many other compounds, the branched-chain mechanism and the competition between branching and termination of reaction chains are decisive not only at very low pressures (which should be tens and hundreds of times lower than atmospheric pressure, as was believed until recently [4–7]), but also at atmospheric and higher pressures. The chain mechanism has been found to play a crucial role both under critical ignition conditions and in suppression of the process in the modes of developed combustion and branched-chain explosion, and also in prevention of a deflagration-to-detonation transition [1–3]. Highly efficient environmentally clean inhibitors have been proposed and tested. They intensely terminate reaction chains by reacting with active intermediate particles, and allow one to control gas-phase combustion under all the above modes at atmospheric and higher pressures [3, 8].

Influence of an Acoustic Field on Flame Development and Transition to Detonation

The work is devoted to experimental and numerical study of flame interaction with acoustic waves in closed and semiclosed pipes filled with preliminarily mixed gaseous mixtures. We analyze the influence of eigenfield (generated by the flame itself) and external acoustic field on the flame dynamics. We show that acoustic field affects the combustion process at all stages. The effect increases with any increase in the energy of initiation of combustion. At later stages of flame development, acoustic waves can initiate the transition to detonation or prevent it. Thus, it is possible to control the combustion modes using external acoustic field.

An experimental study of the diffusion-controlled self-ignition of hydrogen in a channel

The pulsed outflow of hydrogen into channels of circular and rectangular cross sections with a surface area of 20 mm2 was experimentally studied. It was revealed that the shock wave formed during the outflow of a pulsed jet is the reason why it ignites at the contact surface. The range of initial pressures of hydrogen at which it ignites was determined and the dependence of the distance from the diaphragm at which a flame arises at the contact surface on the pressure in the shock wave front for circular and rectangular cross section channels was obtained.

Deflagration-to-Detonation Transition of Methane-Oxygen Mixtures in Narrow Tubes

For recent technical applications it is necessary to reduce the distance between the point of ignition and the actual point of the detonation wave. It is basically related to the requirements of portability of an application.

Liquid drop ejection from a membrane driven by gas detonation products

The process of jet formation from a liquid drop placed on a membrane and driven by detonation of hydrogen-air mixture in a thin tube behind the membrane has been studied. It is shown that a gas mixture capable of detonating can be used instead of a solid explosive in devices for ejecting solid particles and liquid drops-in particular, for needle-free injection of drug solutions.

Application of Gas Detonation for a Needleless Device Development

The routine method of introduction of medicinal substance by means of syringe has a number of lacks: painfulness of procedure, possibility of vessels injury, a needle breakage, transmission of infection, disposable syringe utilization problem. All these lacks are missing with needless injections method. These method means introduction of medicinal substance in form of a tiny high-speed jet. But, in spite of obvious advantages current needleless devices haven’t received a wide circulation in view of modern models characteristic lacks. The main difference between current needleless injection devices is an energy source for jet accelerating. It can be compressed gas or solid fuel detonation. The devices based on compressed gas can carry out only a few (10 - 15) injections without recharging. Using solid fuel detonation produces unhealthy products of combustion. In work [1] it was offered to use a detonation of a hydrogen-airmixture for the medicinal substance acceleration. Impulse of detonation wave is transferred to a medicine by means of a deformable diaphragm.

A theoretical study of a special detonation regime of operation of a pulse detonation device with a variable cross section detonation combustion chamber and a valveless supply system

The results of a theoretical study of the special detonation regime that arises in a pulse detonation device with a variable cross section combustion chamber are presented. The problem is solved analytically within the framework of the one-dimensional approximation. In contrast to the standard version of arbitrary discontinuity disintegration, the problem is solved for a variable cross section at the location of the diaphragm. Since the pulse detonation device operated with a valveless system of fuel and oxidizer supply, a fuel flowed through it over the entire period before spark ignition. This peculiarity of the operation of the combustion chamber was also taken into account. The proposed approach was used to perform calculations for methane-oxygen mixtures, for which extensive experimental data exist. The calculation results are compared to the available experimental data.

Inhibition of explosive decomposition of acetylene

An experimental study of the inhibition of the exothermic decomposition of acetylene diluted with household propane+butane mixture and hydrogen was performed. Acetylene-inhibitor mixtures were heated behind reflected shock waves. The shock wave was generated by the detonation wave initiated in a stoichiometric acetylene-oxygen mixture. The minimum volumetric inhibitor concentrations capable of suppressing the self-decomposition of acetylene were determined.