Inesa Barmina

Experimental Study of the Combustion Dynamics of Renewable & Fossil Fuel Co-Fire in Swirling Flame

Experimental Study of the Combustion Dynamics of Renewable & Fossil Fuel Co-Fire in Swirling Flame The complex experimental research into the combustion dynamics of rene-wable (wood biomass) and fossil (propane) fuel co-fire in a swirling flame flow has been carried out with the aim to achieve clean and effective heat production with reduced carbon emissions. The effect of propane co-fire on the formation of the swirling flame velocity, temperature and composition fields as well as on the combustion efficiency and heat output has been analysed. The results of experimental study show that the propane supply into the wood biomass gasifier provides faster wood fuel gasification with active release of volatiles at the primary stage of swirling flame flow formation, while the swirl-induced recirculation with enhanced mixing of the flame components results in a more complete burnout of wood volatiles downstream of the combustor with reduced mass fraction of polluting impurities in the emissions. Kombinētā Atjaunojamā un Fosilā Kurināmā Degšanas Procesa Dinamikas Eksperimentālie Pētījumi Virpuļplūsmā Veikti kombinētā atjaunojamā (koksnes biomasa) un fosilā kurināmā (propāna) degšanas procesa dinamikas eksperimentālie pētījumi virpuļplūsmās ar mērķi izveidot ekologiski tīrus un efektīvus koksnes biomasas degšanas un siltuma ražošanas procesus, mainot papildus siltuma padevi gaistošo savienojumu degšanas zonā. Eksperimentālo pētījumu komplekss apvieno ātruma sadalījuma, liesmas temperatūras, sastāva un degšanas procesa efektivitātes radiālā un aksiālā sadalījuma veidošanās pētījumus dažādās kombinētā degšanas procesa attīstības stadijās, mainot propāna padevi liesmā. Pētījumu rezultātā parādīts, ka propāna padeve koksnes biomasā ierosina ātrāku koksnes gazifikāciju, nodrošinot pilnīgāku gaistošo savienojumu sadedzināšanu virpuļplūsmas recirkulācijas zonā, kurā notiek intensīva gaistošo savienojumu sajaukšanās ar liesmas komponentēm, palielinot degšanas zonas temperatūru, kas atkarīga no papildus siltuma padeves gazifikātora izejā.

Experimental and Numerical Study of Swirling Flows and Flame Dynamics

Abstract The effect of swirling air on the flow dynamics was investigated for the cold non-reacting flows and the flame arising at thermo-chemical conversion of biomass pellets downstream of a cylindrical channel. Under experimental and numerical investigation was the swirling flow dynamics with the primary axial air supply below a biomass layer and swirling air supply above it. The results indicate that for cold flows the swirling air jet outflow from tangential nozzles leads to the formation of a complex flow dynamics which is influenced both by upstream and downstream air swirl propagation near the channel walls, with correlating swirl-enhanced formation of the upstream and downstream axial flows close to the flow centreline depending on the swirling air supply rate. These axial flows can be completely balanced at their stagnation within the axial recirculation zone. It is shown that at equal boundary conditions for the swirling flame and the cold flows the swirling flow dynamics is influenced by the upstream air swirl-enhanced mixing of the reactants below the air swirl nozzles. This determines the formation of a downstream reaction zone with correlating development of the flow velocity, temperature and composition profiles in the downstream flame regions with improved combustion stability. The low swirl intensity in these regions prevents the formation of a recirculation zone Kopsavilkums Ir veikti kompleksi aukstu nereaģējošu un liesmas virpuļplūsmu dinamikas veidošanās eksperimentālie pētījumi, izvērtējot galvenos faktorus, kas ietekmē šo plūsmu dinamikas veidošanos cilindriskā kanālā virs granulēta biomasas slāņa pie aksiālas primārā gaisa padeves zem granulu slāņa un gaisa virpuļplūsmas padeves virs tā. Auksto virpuļplūsmu pētījumi apliecina, ka plūsmas dinamiku būtiski ietekmē divu savstarpēji konkurējošu un pretēji vērstu virpuļplūsmu veidošanās pie tangenciālās gaisa padeves sprauslas izejas. Lejupvērstā virpuļplūsma, kas veidojas pie kanāla sienām, ierosina no granulu slāņa atstarotās augšupvērstas aksiālās plūsmas veidošanos, palielinot plūsmas aksiālo ātrumu, savukārt augšupvērstā tangenciālā plūsma veido pretēji vērstu aksiālo plūsmu, veidojot recirkulācijas zonu ar izteiktu aksiālās plūsmas stagnāciju tās centrālajā daļā. Pie vienādiem primārā un sekundārā gaisa padeves nosacījumiem atšķirīga plūsmas dinamikas veidošanās ir konstatēta liesmas virpuļplūsmai, kuras veidošanos būtiski ietekmē granulētas biomasas gazifikācija ar sekojošu gaistošo savienojumu uzliesmošanu un degšanas procesa veidošanos liesmas centrālajā daļā. Reversās virpuļplūsmas veidošanās intensificē gaistošo savienojumu sajaukšanos ar gaisa virpuļplūsmu, un stabila degšanas procesa veidošanos plūsmas centrālajā daļā ar korelējošu aksiālā plūsmas ātruma palielināšanos salīdzinot ar nereaģējošo aukstā gaisa plūsmu, pie vienādiem šo plūsmu veidošanās sākuma nosacījumiem samazinot liesmas virpuļskaitli un ierobežojot recirkulācijas zonas veidošanos degšanas zonas pamatnē.

Regulation possibilities of biomass combustion

Abstract The focus of the recent experimental research is to analyze the regulation possibilities of biomass combustion. Three possibilities were chosen as part of this research: a) biomass cofiring with propane, b) swirling flow with re-circulation zone, and c) use of a permanent magnet. The aim of the research is to provide stable, controllable and effective biomass combustion with minimum emissions. The special pilot device was created where biomass can be combusted separately and co-fired with propane. Wood pellets were used during the experiments.

Magnetic Field Control of Combustion Dynamics

Abstract Experimental studies and mathematical modelling of the effects of magnetic field on combustion dynamics at thermo-chemical conversion of biomass are carried out with the aim of providing control of the processes developing in the reaction zone of swirling flame. The joint research of the magnetic field effect on the combustion dynamics includes the estimation of this effect on the formation of the swirling flame dynamics, flame temperature and composition, providing analysis of the magnetic field effects on the flame characteristics. The results of experiments have shown that the magnetic field exerts the influence on the flow velocity components by enhancing a swirl motion in the flame reaction zone with swirl-enhanced mixing of the axial flow of volatiles with cold air swirl, by cooling the flame reaction zone and by limiting the thermo-chemical conversion of volatiles. Mathematical modelling of magnetic field effect on the formation of the flame dynamics confirms that the electromagnetic force, which is induced by the electric current surrounding the flame, leads to field-enhanced increase of flow vorticity by enhancing mixing of the reactants. The magnetic field effect on the flame temperature and rate of reactions leads to conclusion that field-enhanced increase of the flow vorticity results in flame cooling by limiting the chemical conversion of the reactants.

Electrodynamic Control of the Combustion Characteristics and Heat Energy Production

ABSTRACT Electric field effects (EFE) on combustion characteristics, heat energy production, and composition of polluting emissions have been investigated experimentally for different types of fuels (natural gas, biomass) providing experimental study of the EFE in a district heating boiler and complex modeling experiments in a small-scale pilot device. The DC field-induced variations of the produced heat energy, efficiency of heat energy production, flame characteristics, and the composition of polluting emissions have been studied for a positively biased axially inserted electrode and negatively biased (grounded) heat surfaces by varying the applied DC voltage, net current, and consumed electric field power. Experiments in the district heating boiler have shown that electrodynamic control of the heat production and combustion characteristics depends on the applied field voltage, power, and on the flame region, where the top of the axially inserted electrode is located. The most pronounced EFE was observed when the top of the electrode was placed in the primary mixing zone intensifying the mixing of the flame compounds and thereby completing combustion. The mechanism of the electric field effects on the combustion characteristics is discussed with reference to the analysis of electric field effects on the flame characteristics observed in modeling experiments.

Mathematical Modeling on Electromagnetic field Control of the Combustion Process

The present paper considers a mathematical model of 2 D compressible, laminar, axial symmetric flame flow taking into account the Lorentz force action on the development of fuel combustion in a cylindrical pipe. The combustion process is modeled with Arrhenius kinetics using a single step exothermic chemical reaction between fuel and oxidant. The analysis of nonstationary PDEs system with 7 unknown functions is carried out. For the inviscid flow approximation the implicit finite difference scheme in time with upwind differences in space is used. The results of numerical simulation are confirmed by the results of the experimental study of the electromagnetic field effect on the thermo-chemical conversion of biomass mixture (straw+wood).

Combustion Dynamics of Biomass Mixtures with Microwave Pre-Processing of Pellets

Combustion dynamics of wheat straw mixtures with wood or with peat pellets is studied experimentally with the aim to provide a more effective application of wheat straw for heat energy production. Microwave pre-processing of pellets is used to activate their thermal decomposition and thus enhance the release and thermo-chemical conversion of combustible volatiles. Results of the complex measurements of the main flame characteristics and composition of the products show that the enhanced thermal decomposition of pellets provides improvement of the combustion conditions in the flame reaction zone completing thus the combustion of volatiles, increasing the flame temperature, the heat output from the device and energy efficiency and decreasing at the same time the mass fraction of unburned volatiles in the products. Introduction The EU Energy Policy Strategy, which complies with the Kyoto Protocol, prescribes the increased use of cleaner renewable energy sources, partially replacing the fossil fuels with the second generation fuel – wood and agriculture residues [1]. Growing demand for application of agriculture residues for energy production stimulates the production of different types of straw pellets (rape, rice, wheat), which have been known as a more problematic fuel if compared with wood because of the lower heating values (LHV, HHV), higher nitrogen and ash contents in biomass. For that reason, there is a necessity to improve the main combustion characteristics and composition of emission [2, 3]. In order to ensure the wider use of straw for energy production, the co-combustion of straw with renewable or fossil fuels may be used to reduce greenhouse gas emissions during the heat energy production and to improve the main combustion characteristics and the composition of emissions [4]. Further improvement of the combustion characteristics and composition of emissions if straw is used as a fuel, can be achieved using microwave (mw) pre-processed straw pellets that reduces the content of physically bounded water and partially decomposes hemicelluloses, cellulose and lignin, thus reducing the hydrogen-to-carbon (H/C) and oxygen-to-carbon (O/C) content in biomass pellets while increasing their calorific value [5-7]. Actually, it has been demonstrated that mw-pretreatment is an interesting and efficient alternative for biomass conversion to high quality biofuels [8-10]. The results of previous research showed that the microwave pretreatment of biomass pellets could enhance the thermal decomposition of biomass pellets with a faster and more complete thermo-chemical conversion. The main aim of the current study is to provide a more efficient use of wheat straw for energy production by co-combusting straw with wood or with peat pellets and assuring in this way additional improvement of the energy properties of straw pellets at their mw pre-processing. The influence of mw pre-processing of straw pellets on the 133 doi:10.22364/mmp2017.45

Control of the Development of Swirling Airflow Dynamics and Its Impact on Biomass Combustion Characteristics

Abstract The development of the swirling flame flow field and gasification/ combustion dynamics at thermo-chemical conversion of biomass pellets has experimentally been studied using a pilot device, which combines a biomass gasifier and combustor by varying the inlet conditions of the fuel-air mixture into the combustor. Experimental modelling of the formation of the cold nonreacting swirling airflow field above the inlet nozzle of the combustor and the upstream flow formation below the inlet nozzle has been carried out to assess the influence of the inlet nozzle diameter, as well primary and secondary air supply rates on the upstream flow formation and air swirl intensity, which is highly responsible for the formation of fuel-air mixture entering the combustor and the development of combustion dynamics downstream of the combustor. The research results demonstrate that at equal primary axial and secondary swirling air supply into the device a decrease in the inlet nozzle diameter enhances the upstream air swirl formation by increasing swirl intensity below the inlet nozzle of the combustor. This leads to the enhanced mixing of the combustible volatiles with the air swirl below the inlet nozzle of the combustor providing a more complete combustion of volatiles and an increase in the heat output of the device.

Experimental Study of Thermal Decomposition and Combustion of Lignocellulosic Biomass Pellets / GRANULĒTAS LIGNOCELULOZES BIOMASAS TERMISKĀS SADALĪŠANĀS UN DEGŠANAS PROCESU EKSPERIMENTĀLIE PĒTĪJUMI

The study is aimed at cleaner and more efficient heat energy production through investigation and analysis of the thermal decomposition of lignocellulosic biomass pellets with different elemental composition, the heating values and contents of hemicellulose, cellulose and lignin. The estimation is provided for the influence of biomass composition on the combustion characteristics for softwood, wheat straw and wheat straw lignin pellets. The kinetics of thermal decomposition was studied experimentally, using a pilot device for two-stage processes of thermochemical conversion including gasification and combustion of biomass pellets under varying conditions. The experimental study includes time-dependent measurements of the biomass pellet weight loss during gasification and the correlating variations of the flame temperature, heat production rates, combustion efficiency and composition of the products at different stages of thermochemical conversion. Estimation is also given for the influence of the biomass composition on the combustion characteristics and heat energy production. Kopsavilkums Pētījumu galvenais mērķis ir iegūt tīru un efektīvu siltumenerģijas ražošanu, izmantojot dažādas izcelsmes biomasas granulas (koksnes, kviešu salmu, kviešu salmu lignīna) ar atšķirīgu elementāro sastāvu, siltumspēju, hemicelulozes, celulozes un lignīna saturu, veicot detalizētu šo granulu termiskās sadalīšanās un degšanas procesu izpēti. Eksperimentālie termiskās sadalīšanās un degšanas procesu pētījumi ir veikti, izmantojot eksperimentālo iekārtu ar integrētu gazifikatoru un degšanas kameru. Granulētās biomasas termiskās sadalīšanās un degšanas procesu kinētiskie pētījumi ietver granulu masas zudumu mērījumus biomasas gazifikācijas procesā un korelējošās degšanas zonas temperatūras, saražotā siltuma daudzuma un degšanas produktu sastāva mērījumus dažādās gazifikācijas un degšanas procesa stadijās, izvērtējot biomasas elementārā un ķīmiskā sastāva ietekmi uz šiem procesiem.

Effect of Microwave Pre-Processing of Pelletized Biomass on its Gasification and Combustion / Mikroviļnu Priekšapstrādes Ietekme Uz Granulētas Biomasas Gazifikācijas Un Degšanas Procesiem

Abstract To effectively produce clean heat energy from biomass, microwave (mw) pre-processing of its different types - pelletized wood (spruce), herbaceous biomass (reed canary grass) and their mixture (50:50) - was carried out at the 2.45 GHz frequency with different durations of biomass exposure to high-frequency oscillations. To estimate the mw pre-processing effect on the structure, composition and fuel characteristics of biomass, its thermogravimetric (TG), infrared spectroscopy (FTIR) measurements and elemental analysis were made. The pre-processing is shown to enhance the release of moisture and low-calorific volatiles and the partial destruction of biomass constituents (hemicelluloses, cellulose), promoting variations in the elemental composition and heating values of biomass. The field-enhanced variations of biomass characteristics and their influence on its gasification and combustion were studied using an integrated system of a biomass gasifier and a combustor with swirl-enhanced stabilization of the flame reaction zone. The results show that the mw pre-processing of biomass pellets provides a faster weight loss at the gasification, and, therefore, faster ignition and combustion of the activated pellets along with increased output of heat energy at their burnout Kopsavilkums Veikti kompleksi eksperimentālie pētījumi par mikroviļņu (2,45 GHz) priekšapstrādes ietekmi uz dažādas izcelsmes biomasas granulu (egles, miežabrāļa un to maisījumu 50:50) gazifikācijas un degšanas procesiem. Pētījumi apvieno granulētās biomasas elementārā sastāva un termogravimetriskos mērījumus, kā arī granulētās biomasas gazifikācijas un degšanas procesu kompleksu izpēti, apvienojot biomasas svara izmaiņu kinētiskos mērījumus ar degšanas zonas temperatūras, iekārtas jaudas un degšanas produktu sastāva kinētiskiem mērījumiem. Pētījumiem izmantota mazas jaudas eksperimentālā iekārta (līdz 2,5 kW), kuru veido integrēts gazifikātors un degšanas kamera. Pētījumu rezultātā konstatēts, ka mikroviļņu priekšapstrāde nodrošina intensīvāku biomasas gazifikāciju, ātrāku gaistošo savienojumu veidošanos, uzliesmošanu un pilnīgāku sadedzināšanu ar sekojošu saražotās īpatnējā siltuma enerģijas pieaugumu