Experimental study on soft PSD material of dual pulse solid rocket motor

In order to study the failure reason of the soft PSD in the dual pulse solid rocket motor (SRM), the deformation process of the intermediate section of the second pulse combustion chamber was simplified to the two-dimensional plane strain state, and the calculation method of the circumferential strain of the soft PSD was obtained. The influencing factors of the circumferential strain of the soft PSD were studied. The main factors affecting the circumferential strain of the soft PSD are the gap between the soft PSD and the propellant grain, and the circumferential strain on the inner surface of the propellant grain. The calculation method could be used to initially estimate the circumferential strain of the soft PSD, and then predict the rationality and feasibility of the design scheme. The apparent morphology and area change rate of EPDM materials of PSD under different strains were studied by DIC tensile test. The variation of the porosity of the EPDM material with the increase of strain was obtained by micro-CT. By comparing the SEM results of the fracture and the slit of the tensile test piece, the failure mode of the EPDM material of PSDs was determined, and the failure mechanism of the PSD structure was obtained. The conclusions obtained in this paper can provide a useful reference for the design of the PSD in dual pulse SRM.

Temperature estimating method for exhaust gases in valveless pulsejet engine

The article describes the problem of measuring the temperature in a pulse combustion chamber. The object of the study is a valveless pulsejet. The problem is analysed on the example of exhaust gases temperature measurement. The measurement in these conditions requires the use of a sensor resistant to large changes in gas velocity and temperature and at the same time with adequatly low inertia. This excludes the use of fast and precise yet thin, resistant wire sensors or ultrafast thin film thermocouples. Finally, a temperature measurement system based on sheated thermocouples was chosen. During each test the thermocouple has its own temperature which is different from the medium temperature. In order to properly determine the measured temperature of flowing media it is necessary to take the sensor time characteristics into account. In this article the iteration method is proposed to solve this problem.

Performance and Operating Characteristics of Micro Gas Turbine Driven by Pulse, Pressure Gain Combustor

This paper presents the experimental results of a micro gas turbine driven by pulse, pressure gain combustor. The aim of this study is to demonstrate the improvement of the engine performance by applying the pressure gain combustion. The micro gas turbine is composed of a combustor having two combustion chambers and an automotive turbocharger which is used as a compressor and a turbine. The outlets of two combustion chambers are joined by a confluence part to connect with the turbine. By changing the combustion methods of each combustion chamber, the gas turbine was operated in three modes; normal combustion mode, pulse combustion augmented mode, and fully pulse combustion mode. In the normal combustion mode, two combustion chambers were operated under continuous, constant-pressure combustion. In the pulse combustion augmented mode, one combustion chamber was operated under continuous, constant-pressure combustion and the other was operated under pulse combustion. In the fully pulse combustion mode, two combustion chambers were operated under pulse combustion. The pulse combustion applied in this study was the forced-ignition type, active pulse combustion. Although the pressure increase was attained by the pulse combustion comparing with the normal combustion, the mass-averaged pressure in the combustor showed that the net pressure gain in the combustor was not attained. The engine performance such as thermal efficiency and work and operating characteristics of gas turbine were investigated for two operation modes. In the pulse combustion augmented mode, the gas turbine could successfully sustain its operation as well as normal operation mode. The increase in the combustor pressure affected the air mass flow rate and the compressor performance, resulted in the decrease of performance comparing with the normal combustion mode.

Pulsed Multiphase Flows—Numerical Investigation of Particle Dynamics in Pulsating Gas–Solid Flows at Elevated Temperatures

Although the benefits of pulsating multiphase flows and the concomitant opportunity to intensify heat and mass transfer processes for, e.g., drying, extraction or chemical reactions have been known for some time, the industrial implementation is still limited. This is particularly due to the lack of understanding of basic influencing factors, such as amplitude and frequency of the pulsating flow and the resulting particle dynamics. The pulsation generates oscillation of velocity, pressure, and temperature, intensifying the heat and mass transfer by a factor of up to five compared to stationary gas flow. With the goal of process intensification and targeted control of sub-processes or even the development of completely new processing routes for the formation, drying or conversion of particulate solids in pulsating gas flows as utilized in, e.g., pulse combustion drying or pulse combustion spray pyrolysis, the basic understanding of occurring transport processes is becoming more and more important. In the presented study, the influence of gas-flow conditions and particle properties on particle dynamics as well as particle residence time and the resulting heat and mass transfer in pulsating gas–solid flows are investigated.

Optimizing Pulse Combustion Parameters in Carbon Anode Baking Furnaces for Aluminum Production

Pulsating flame jets have been widely used in open-top carbon anode baking furnaces for aluminum electrolysis. Reducing energy consumption and pollutant emissions are still major challenges in baking (heat-treatment) carbon anode blocks. It is also of immense significance to bake all the anodes uniformly irrespective of their position in the furnace. Baking homogeneity can be enhanced noticeably by optimizing anode baking operational, geometrical, and physical parameters. In the present study, CFD simulations are combined with a response surface methodology to investigate and optimize the effects of pulse pressure, pulse frequency, and mainstream inlet oxygen concentration and mainstream inlet temperature. Two-levels half fractional factorial design with a center point is employed. It is perceived that pulse combustion with short pulse time and high momentum results in significant enhancement of the anode baking furnace energy efficiency. The temperature homogeneity is also significantly improved. It is found that the oxygen concentration is statistically the most significant parameter on NOx and soot formations, followed by the fuel flow rate. For NOx formation, air inlet oxygen concentration has a strong interaction with pulse duration. Coupling CFD models with the response surface methodologies demonstrated great potential in multi-objective optimization of the anode baking process with enhanced energy efficiency and baking uniformity.