In this paper,CPCM(Composite Phase Change Material)was manufactured with metal foam matrix used as filling material.The temperature curves were obtained by experiment.The performance of heat transfer was analyzed.The experimental results show that metal foam matrix can improve temperature uniformity in phase change thermal storage material and enhance heat conduction ability.The thermal performance of CPCM is significantly improved.The efficiency of temperature control can be obviously improved by adding metal foam in phase change material.CPCM is in solid-liquid two-phase region when temperature is close to phase change point of paraffin.An approximate plateau appears.The plateau can be considered as the temperature control zone of CPCM.Heat can be transferred fiom hot source and be uniformly spread in thermal storage material by using metal foam matrix since thermal storage material has the advantage of strong heat storage capacity and disadvantage of poor heat conduction ability.Natural convection promotes the melting of solid-liquid phase change material.Good thermal conductivity of foam metal accelerates heat conduction of solid-liquid phase change material.The interior temperature difference decreases and the whole temperature becomes more uniform.For the same porosity with a metal foam,melting time of solid-liquid phase change material decreases.Heat conduction is enhanced and natural convection is suppressed when pore size of metal foam is smaller.The thermal storage time decreases and heat absorption rate increases when the pore size of metal foam reduces.The research results can be used to guide fabricating the CPCM.
The combustion chamber is an important component for the Stifling engine heated by natural gas. In the paper, we develop a combustion chamber for the Stifling engine which aims to generate 3-5 kWe electric power. The combustion chamber includes three main components： combustion module, heat exchange cavity and thermal head. Its feature is that the structure can divide ＂combustion＂ process and ＂heat transfer＂ process into two appar- ent individual steps and make them happen one by one. Since natural gas can mix with air fully before burning, the combustion process can be easily completed without the second wind. The flame can avoid contacting the thermal head of Stifling engine, and the temperature fields can be easily controlled. The designed combustion chamber is manufactured and its performance is tested by an experiment which includes two steps. The experi- mental result of the first step proves that the mixture of air and natural gas can be easily ignited and the flame burns stably. In the second step of experiment, the combustion heat flux can reach 20 kW, and the energy utiliza- tion efficiency of thermal head has exceeded 0.5. These test results show that the thermal performance of com- bustion chamber has reached the design goal, The designed combustion chamber can be applied to a real Stifling engine heated by natural gas which is to generate 3-5 kWe electric power.
LI TieSONG XiangeGUI XiaohongTANG DaweiLI ZhigangCAO Wenyu
本文在实验的基础上,对瓦斯爆炸过程中爆燃向爆轰转捩(DDT,Deflagration to Detonation Transition)问题进行了研究,并运用CJ(Chapman and Jouguet)理论计算了火焰阵面流场参数。研究结果表明:障碍物对瓦斯爆炸过程中爆燃向爆轰转捩具有诱导作用,无障碍物时爆炸波的传播速度较小,爆炸强度较弱;随着障碍物的增多,爆炸波和火焰传播速度明显增大,爆燃易于向爆轰转捩,爆炸强度和危险性显著提高。上述研究结果对于现场如何防治瓦斯爆炸,防止、降低煤矿重大事故的发生具有一定的指导作用。
