Tudor Prisecaru

Swirl Injector for Premixed Combustion of Hydrogen–Methane Mixtures

Among the present domains of interest in scientific research, the field of combustion gained more and more attention, especially the search for new greener and more efficient fuels. One idea that is intensely studied worldwide is the possibility of using hydrogen, since new ways for producing and transporting it developed lately. Different studies are trying to confirm the possibility of hydrogen transport using the existing natural gas distribution network, by mixing the two gases. Because the properties of the new mixture influence the combustion parameters, using the existing equipment would face new problems, like the risk of flashback, the effects of higher temperatures and the modification of the flame front. Hence new solutions are needed. In this context, this paper presents a new developed and patented type of injector designated to the combustion of premixed hydrogen-methane fuel in various proportions. Based on the characteristics and dimensions of an existing combustion chamber of Garrett GTP30-67 gas turbine, different types of swirled injectors were numerically simulated and compared. After the analysis of the simulation results, plastic models were produced using 3d printing technology. The preliminary conclusions lead to a final pilot injector, made from titanium alloy. The new type of swirled injector was tested on a low pressure rig designed to have similar dimensions to the combustion chamber of the initial gas turbine. For the experiment only natural gas was used as fuel. Finally, the experiments showed a stable and efficient working flame can be obtained with the new type of injector. Moreover, the results confirmed the possibility of developing and improving the new found type of swirled injector for other types of combustion applications.

Mathematical model and experimental tests of hydrogen diffusion in the porous system of biomass

ABSTRACT The paper deals with mathematical model and experimental tests of hydrogen (pure or mixed) diffusion in the porous system of biomass. A mathematical model has been developed for gas diffusion in a porous system and based on it a numerical simulation for hydrogen absorption gas been carried out. The results are presented graphically and they point out that the concentration variation inside the pore decreases with the increases of pore length and increases with the increase of hydrogen flux. Also, the absorbed hydrogen quantity decreases with the increase of the pore length and for a given pore length the absorbed hydrogen quantity increases with the increases of hydrogen flux and internal pore surface. Research regarding hydrogen diffusion in the porous system of biomass is part of wider research focusing on using hydrogen as an active medium for solid biomass combustion. In parallel with hydrogen diffusion in solid biomass, tests regarding biomass combustion previously subjected to a hydrogen flux will be carried out.

Energy and monomer recovery from polymer wastes

In this paper the products obtained through thermochemical processing of several polymer-based wastes are characterised. The influence of chemical composition of raw materials on the characteristics of obtained products has been investigated by using fixed bed reactor. The aim of this work is to identify the best use of products recovered after pyrolysis of plastic wastes collected from chemical and biochemical laboratories. This work is developed in a laboratory bench installation design to perform O2-free processing at atmospheric pressure. The process parameters such as pyrolysis temperature and adapted heating rate have been determined through the transposition of thermal and kinetic information provided by thermogravimetric analysis (TGA). Gas-chromatography techniques have been used to identify the chemical composition of gases (GC/TCD) and liquids (GC/FID-MS). It was established that polymer wastes can led to a valuable liquid products, with encouraging energetic properties that allow their blending with fuels currently used without altering the performances of burning devices.

Experimental Analysis of a Kinetic Energy Recovery System Intended for Small and Medium Passenger Cars

This article presents experimental tests on kinetic energy recovery system (KERS) intended for small and medium passenger cars. The test rig is composed of an electric motor, a two stage timing belt drive and a high speed flywheel. The evolution of the rotation speed was measured using a speed sensor mounted on the flywheel. The flywheel rotation speed was measured during the first minute of deceleration and the total friction torque was obtained. The measurements were taken for three different maximal speeds of the flywheel. The friction torque on the deep groove ball bearings was computed and hence the percentage of the total friction torque was obtained. It is found that the flywheel presents low friction torque and it is capable to maintain the stored energy for a sufficient period of time in order to give it back to the wheels or to slowly store it to an electrical storage system.

Thermodynamic evaluation for a small scale compressed air energy storage system by integrating renewable energy sources

The present work aims to store renewable energy from wind and sun in the form of compressed air. Several scenarios to find the best operating conditions for a small scale compressed air energy storage system has been analyzed in this paper. The results show a primary efficiency of 52% to 68% for a configuration in which the heat extracted from the air during compression is returned to it during expansion. While for a configuration in which the heat is used for other purposes the theoretical primary efficiency has been found between 37% and 51%, but in this configuration the system its able to provide an important amount of hot and cold. According to consumer needs the current system can be configured to deliver hot, cold and electricity or only electricity.

A Method to Increase the Natural Frequency of a Ground Moving System

The paper presents the summary of the finding solution process for the vibrations attenuation of a ground moving system designed for a terrestrial / aerial drone. A spring was calculated, a damping system was designed and natural frequency simulated. Comparison was made between the natural frequencies obtained for both situations: the ground moving system equipped with the damper and without the damper.Key words: natural frequency, modal analysis, 3D printing, dumper.

Mathematical Modelling of a Hybrid Micro-Cogeneration Group Based on a Four Stroke Diesel Engine

Abstract The paper presents a part of the work conducted in the first stage of a Research Grant called ”Hybrid micro-cogeneration group of high efficiency equipped with an electronically assisted ORC” acronym GRUCOHYB. The hybrid micro-cogeneration group is equipped with a four stroke Diesel engine having a maximum power of 40 kW. A mathematical model of the internal combustion engine is presented. The mathematical model is developed based on the Laws of Thermodynamics and takes into account the real, irreversible processes. Based on the mathematical model a computation program was developed. The results obtained were compared with those provided by the Diesel engine manufacturer. Results show a very high correlation between the manufacturer’s data and the simulation results for an engine running at 100% load. Future developments could involve using an exergetic analysis to show the ability of the ORC to generate electricity from recovered heat

Detection and Reconnaissance Ranges Evaluation Using Thermovision

The paper presents own adapted methodologies used in detection and reconnaissance probability calculations before developing or buying thermal equipments. The methodologies are presented like a succession of calculation steps, easy to run once some input data is established.

Methods for Determining the Characteristics of Laser Beams and the Optical Transmission

The paper presents new methods and procedures to measure the characteristics of laser beams and their transmission through optical systems. The paper describes the work procedures and equipments used to measure the characteristics of laser beams and their transmission through optical systems. Using these working procedures, experimental measurement for the characteristics of the beam for a 1.54 µm laser rangefinder and the transmission of a 633 nm laser beam through laser protection glasses were made.

Injection Technology of Enriched Hydrogen Gas to Reduce Sulfur Oxide and Fly Ash Emission

This paper presents a CFD model and the first validation set of results concerning a new technology to inject and adsorb, under safe conditions, a hydrogen enriched gas in solid fuel that has been milled, at the burner inlets of a power designated steam boiler. The present paper presents a dynamic model of enrichment technology which refers to the improvement of the classical existent technological flow of the pulverized coal burning installation in order to prepare and burn weak volatile matters pulverized fuel. The model refers to obtain an enriched hydrogen pit coal by the injection of an hydrogen enriched gas into the average ground pulverized pit coal current, the control of the gas diffusion into the porous environment of the powder particles, process that is accelerated in comparison with other gaseous component parts due to the hydrogen atom / molecule characteristics, and finally, the adsorption of this molecule into coal particles. The complex nature of this model consists in: to issue and simulate the procedure to inject and diffuse the hydrogen enriched gas in the pulverized coal current; to design and to simulate an installation to enrich by injection the pulverized pit coal in primary mixture stream — a special attention is paid to the influence of the pit coal particles porosity upon the hydrogen adsorbing process; to develop a model to simulate the burners operation in these new conditions. Burning process of this enriched pulverized pit coal is expected to produce a strong decrease in sulfur dioxide emissions and also in the flying ash concentration at the end of the furnace. A set of preliminary experimental results concerning all aspects of this technology will be also presented. These results have been obtained on a laboratory scaled installation which is located at labs of the Politehnica University of Bucharest. This installation has a storage capacity of hydrogen, a 5000 rpm ventilator mill to prepare the solid fuel. Test equipment includes Horiba gas analyzer, high speed camera and all other facilities to determine all the operational parameters. Different types of burners can be installed at this installation in order to determine an optimal procedure.Copyright