Experimental simulation and numerical analysis of coal spontaneous combustion process at low temperature

The characteristic of coal spontaneous combustion includes oxidative property and exothermic capacity. It can really simulate the process of coal spontaneous combustion to use the large scale experimental unit loading coal 1 000 kg. According to the field change of gas concentration and coal temperature determined through experiment of coal self ignite at low temperature stage, and on the basis of hydromechanics and heat transfer theory, some parameters can be calculated at different low temperature stage, such as, oxygen consumption rate, heat liberation intensity. It offers a theoretic criterion for quantitatively analyzing characteristic of coal self ignite and forecasting coal spontaneous combustion. According to coal exothermic capability and its thermal storage surroundings, thermal equilibrium is applied to deduce the computational method of limit parameter of coal self ignite. It offers a quantitative theoretic criterion for coal self ignite forecasting and preventing. According to the measurement and test of spontaneous combustion of Haibei coal, some token parameter of Haibei coal spontaneous combustion is quantitatively analyzed, such as, spontaneous combustion period of coal, critical temperature, oxygen consumption rate, heat liberation intensity, and limit parameter of coal self ignite.

Review: laser ignition for aerospace propulsion

Renewed interest in the use of high-speed ramjets and scramjets and more efficient lean burning engines has led to many subsequent developments in the field of laser ignition for aerospace use and application.Demands for newer,more advanced forms of ignition,are increasing as individuals strive to meet regulations that seek to reduce the level of pollutants in the atmosphere,such as CH_(x),NO_(x),and SO_(2).Many aviation gas turbine manufacturers are interested in increasing combustion efficiency in engines,all the while reducing the aforementioned pollutants.There is also a desire for a new generation of aircraft and spacecraft,utilizing technologies such as scramjet propulsion,which will never realize their fullest potential without the use of advanced ignition processes.These scenarios are all limited by the use of conventional spark ignition methods,thus leading to the desire to find new,alternative methods of ignition.This paper aims to provide the reader an overview of advanced ignition methods,with an emphasis on laser ignition and its applications to aerospace propulsion.A comprehensive review of advanced ignition systems in aerospace applications is performed.This includes studies on gas turbine applications,ramjet and scramjet systems,and space and rocket applications.A brief overview of ignition and laser ignition phenomena is also provided in earlier sections of the report.Throughout the reading,research papers,which were presented at the 2nd Laser Ignition Conference in April 2014,are mentioned to indicate the vast array of projects that are currenty being pursued.

Experimental investigation of a gliding discharge plasma jet igniter

Relight of jet engines at high altitude is difficult due to the relatively low pressure and temperature of inlet air.The penetration of initial flame kernel affects the ignition probability in the turbine engine combustor greatly.In order to achieve successful ignition at high altitude,a deeper penetration of initial flame kernel should be generated.In this study,a Gliding Arc Plasma Jet Igniter(GAPJI)is designed to induce initial flame kernel with deeper penetration to achieve successful ignition at high altitude.The ignition performance of the GAPJI was demonstrated in a model combustor.It was found that GAPJI can generate plasma with deeper penetration up to 30.5 mm than spark igniter with 22.1 mm.The discharge power of GAPJI was positively correlated with flow rate of the carrier gas,approaching 200 W in average.Ignition experiments show that GAPJI has the advantage of extending the lean ignition limit.With GAPJI,the lean ignition limit of the combustor is 0.02 at 0 km,which is 55.6%less than that with spark igniter(0.045).The evolution of flame morphology was observed to explore the development of the flame kernel.It is shown that the advantage of a high penetration and continuous releasing energy can accelerate the ignition process and enhance combustion.