Jet fuel ignition delay times: Shock tube experiments over wide conditions and surrogate model predictions

Rotating detonation combustors and their similarities to rocket instabilities

Characterization of instabilities in a Rotating Detonation Combustor

This review examines existing knowledge on the genesis and flame acceleration of explosions from methane–air mixtures. Explosion phases including deflagration and detonation and the transition from deflagration to detonation have been discussed. The influence of various obstacles and geometries on explosions in an underground mine and duct have been examined. The discussion, presented here, leads the readers to understand the considerations which must be accounted for in order to obviate and/or mitigate any accidental explosion originating from methane–air systems.

A review on understanding explosions from methane-air mixture

Investigation of rotating detonation combustor operation with H2-Air mixtures

The paper outlines an experimental study of influence of the ignition position and obstacles on explosion development in premixed methane–air mixtures in an elongated explosion vessel. As the explosion vessel, 1325 mm length tube with 128.5 mm diameter was used. Location of the ignition was changeable, i.e., fitted in the centre or at one of ends of the tube, when the tube was in a horizontal position. When it was in a vertical position, three locations of the ignition (bottom, centre and top) were used. In the performed study, the influence of obstacles on the course of pressure was investigated. Two identical steel grids were used as the obstacles. They were placed 405 mm from either end of the tube. Their blockage ratio (grid area to tube cross-section area) was determined as 0.33 for most of experiments. A few additional experiments (with smaller blockage ratio—0.16) were also conducted in order to compare the influence of the blockage ratio on the explosion development. Also some experiments were conducted in a semi-cylindrical vessel with volume close to 40 l. All the experiments were performed under stabilized conditions, with the temperature and pressure inside the vessel settled to room values and controlled by means of electronic devices. The pressure–time profiles from two transducers placed in the centreline of the inner wall of the explosion vessel were obtained for stoichiometric (9.5%), lean (7%) and rich (12%) methane–air mixture. The results obtained in the study, including maximum pressures and pressure–time profiles, illustrate a quite distinct influence of the above listed factors upon the explosion characteristics. The effect of ignition position, obstacles location and their BR parameters is discussed. The additional aim of the performed experiments was to find the data necessary to validate a new computer code, developed to calculate an explosion hazard in industrial installations.

Influence of ignition position and obstacles on explosion development in methane–air mixture in closed vessels

Experimental and numerical study of rotating detonation is presented. The experimental study is focused on the evaluation of the geometry of the detonation chamber and the conditions at which the rotating detona- tion can propagate in cylindrical channels. Lean hydrogen air mixtures were tested in the experiments. The pressure measured at dierent loca- tions was used to check the detonative nature of combustion. Also, the relationship between detonation velocity and operation conditions is ana- lyzed in the paper. The experimental study is accompanied with numer- ical analysis. The paper brie§y presents the results of two-dimensional (2D) numerical simulation of detonative combustion. The detonating mixture is created by mixting hydrogen with air. The air is injected axially to the chamber and hydrogen is injected through the inner wall of the chamber in radial direction. Application of proper injection con- ditions (pressure and nozzle area) allows establishing a stable rotating detonation like in the experiments. The detonation can be sustained for some range of conditions which are studied herein. The analysis of mean parameters of the process is provided as well. The numerical simulation results agree well with the experiments.

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Experimental and numerical study of the rotating detonation engine in hydrogen-air mixtures

This paper presents a new model of explosion propagation in a closed vessel. The foundation of the formulation is a sub-model of turbulent burning velocity based on the assumption that the burning velocity of a turbulent wrinkled flame can be determined from the flame surface. In addition, model development includes simple sub-models of heat transfer and free convection. In order to verify the physics, the model was utilized to simulate the explosion of a methane–air mixture in two different test vessels. The results obtained by use of this new model were compared with results obtained by use of the classical model. While the simulations showed that both are accurate, the new model presented in this paper (called “flame surface model” for simplicity) is more flexible and can easily accommodate sub-models of different phenomena that can play an important role in fuel–air explosions.

A new phenomenological model of gas explosion based on characteristics of flame surface

Exhaust gas recirculation has become commonplace within the automobile industry to reduce nitrogen oxide emissions because of its ability to lower the combustion temperature However, it leads to an increase of particulate matter and degradation in fuel economy One possible avenue for recovering this efficiency is to use exhaust assisted fuel reforming (EAFR) to generate hydrogen by catalytic means using injected fuel and exhaust and add it to the inlet mixture Adding hydrogen in this manner has shown an increase in combustion stability and efficiency of the engine while reducing particulate matter production Many classical works use incompressible fluid flow models in order to simulate the reactive flow in monolithic catalyst However, such models are not appropriate in the case of EAFR, where exothermic reactions cause a large increase in the temperature and consequently in density To simulate a catalyst undergoing EAFR reactions, a compressible flow solver was used in order to take into account the

Influence of Density Variation on One-Dimensional Modeling of Exhaust Assisted Catalytic Fuel Reforming

An experimental study of the interaction of a shock wave with a hexane droplet is presented. The main goal of the experiments was to record images of the process and measure basic parameters describing movement, dispersion and evaporation of the droplets engulfed by a shock wave propagating in air. A shock tube with a visualization section was used for this research. Photography of the process allowed one to measure the positions, velocities and sizes of mist clouds created by the interaction processes. Analysis of the pictures shows that there is no qualitative difference between cases for different size droplets, but shock Mach number had a significant effect on the process. Quantitative analysis shows that under certain conditions, a catastrophic breakup mechanism of dispersion occurred. The droplets are shattered into a mist cloud before they achieve mechanical equilibrium with the surrounding gas. The approximate time for the complete dispersion and acceleration of the fuel droplet varies from 300 to 500 μs, and depends both on the droplet diameter and shock velocity. The dispersion time is controlled principally by the droplet diameter, and to a lesser extent, the shock Mach number.

A. Kobiera

Papers

Influence of ignition position and obstacles on explosion development in methane–air mixture in closed vessels

Experimental and numerical study of the rotating detonation engine in hydrogen-air mixtures

A new phenomenological model of gas explosion based on characteristics of flame surface

Influence of Density Variation on One-Dimensional Modeling of Exhaust Assisted Catalytic Fuel Reforming

Study of the shock-induced acceleration of hexane droplets