Maija Zake

• Dr. Phys. at University of Latvia

Original experimental device with heat output up to 20 kW was developed and tested with the aim to provide wider use of the locally available renewable energy resources - agriculture residues (wheat straw) for sustainable energy production and reduced effect of energy production on climate changes. To provide efficient control of thermochemical con...

In the present study analysis of co-firing microwave (MW) pre-treated biomass pellets of different origins (wood and wheat straw), with raw pellets (wood, straw, and peat), to control and improve thermochemical conversion of biomass blends and achieve a sustainable use of local energy resources in energy production has been carried out. Effects of...

Possibilities of more efficient use of regional lignocellulosic resources (wood, wheat straw, peat) of different origin for an environmentally friendly energy production using selectively MW pre-treated blends of commercial wood or wheat straw pellets with raw peat pellets are studied. A hypothesis is proposed and tested that selective MW pre-treat...

The main objective of research is to promote wider use of the regional bioenergy resources for the development of environmentally friendly energy production providing microwave pre-treatment of different origin lignocellulosic biomass pellets (wood, straw, and peat) at frequency 2.45 GHz. A hypothesis is proposed and tested that MW pre-treatment of...

The objective of the study was to investigate a more effective use of commercially available biomass pellets (wheat straw, wood, peat) using microwave pretreatment to improve heat production. Pellets were pretreated using the originally designed microwave torrefaction device. The effects of microwave (mw) pretreatment were quantified, providing mea...

With the aim to control and improve the thermo-chemical conversion of straw pellets, the experimental investigations of the DC electric field effect on the combustion dynamics and heat energy production were made. The electric field effect on the gasification/combustion characteristics was studied using three different positions of the positively c...

The main goal of the present study is to promote a more effective use of agriculture residues (straw) as an alternative renewable fuel for cleaner energy production with reduced greenhouse gas emissions. With the aim to improve the main combustion characteristics at thermo-chemical conversion of wheat straw, complex experimental study and mathematic...

The aim of this study was to provide more effective use of straw for energy production by co-firing wheat straw pellets with solid fuels (wood, peat pellets) under additional electric control of the combustion characteristics at thermo-chemical conversion of fuel mixtures. Effects of the DC electric field on the main combustion characteristics were...

The main goal of the present study is to assure a more effective use of CO2 neutral fuel (wheat straw) for cleaner energy production with reduced greenhouse carbon emissions by partially replacing a fossil fuel (crashed coal) with a renewable one. This work combines experimental study and mathematical modelling of the processes developing during th...

The main goal of the present study is to obtain a more effective utilization of wheat straw for energy production during a co-combustion with peat. For this purpose, an electric field was applied to the flame produced by the combustion of volatiles. This work combines experimental study and mathematical modelling of the processes developing during...

Thermo-chemical conversion of microwave activated wheat straw mixtures with wood or peat pellets is studied experimentally with the aim to provide more effective application of wheat straw for heat energy production. Microwave pre-processing of straw pellets is used to provide a partial decomposition of the main constituents of straw and to activat...

This paper deals with a simplified model taking into account the interplay of compressible, laminar, axisymmetric flow and the electrodynamical effects due to Lorentz force’s action on the combustion process in a cylindrical pipe. The combustion process with Arrhenius kinetics is modelled by a single step exothermic chemical reaction of fuel and oxida...

The main goal of this research is to promote a more efficient use of wheat straw for cleaner energy production by co-firing straw pellets with solid and gaseous fuels (wood pellets, propane) and to assess the impact of the mixture composition on the gasification/combustion characteristics and heat energy production. The effect of straw co-firing on...

Effects of wheat straw co-firing with gas (propane flame) and co-gasification/co-combustion with wood pellets on the development of thermo-chemical conversion of biomass pellets and on heat energy production were experimentally studied and analyzed with the aim to improve the gasification/combustion characteristics and the applicability of wheat st...

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 format...

The present paper discusses a mathematical model of 3D compressible, laminar flame flow, considering the Lorentz force action on the development of fuel combustion in a cylindrical pipe. The combustion process is modelled with Arrhenius kinetics using two exothermic chemical reactions. A system of non-stationary partial differential equations with...

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...

Mathematical modelling and numerical simulation of second-order reaction kinetics for fast and slow exothermic reactions has been applied with the aim to estimate the development of composition and temperature profiles downstream of the flame reaction zone. The effects of slow and fast exothermic reactions on the formation of the flame composition...

Experimental study and mathematical modelling were aimed to provide electric control of biomass thermochemical conversion and analysis of the DC electric and electromagnetic effects on combustion dynamics to obtain a cleaner and a more effective heat energy production. Mathematical modelling of the formation of flame velocity and temperature profil...

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 (DKVR) and complex modelling experiments in a small-scale pilot devic...

With the aim to provide control of biomass thermal decomposition and combustion of volatiles, the external electric field effect on the wood biomass gasification/combustion characteristics during biomass thermo-chemical conversion at different stages of the swirling flame formation and heat energy production was experimentally studied.The DC electr...

An experimental was conducted with the aim to provide magnetic field control of the gasification / combustion characteristics and heat energy production at thermo-chemical conversion of biomass (wood) pellets. The results show that the gradient magnetic field - enchanced mass transfer of paramagnetic oxygen can be used as a tool to provide control...

Experimental investigations of the DC electric field effect on thermal decomposition of biomass, formation of the axial flow of volatiles (CO, H2, CxHy), mixing of volatiles with swirling airflow at low swirl intensity (S ≈ 0.2-0.35), their ignition and on formation of combustion dynamics are carried out with the aim to understand the mechanism of...

The effects of DC and AC electric field at 50 Hz and 13.56 MHz and 41 MHz frequencies on the combustion characteristics of biomass pellets have been investigated using an experimental setup of average power 20-40 kW with continuous pellet feed into the setup at average rates 1.5-3 g/s by applying AC voltage to the flame base, where thermal decompos...

The main aim of the present study is to obtain clean and effective heat energy production by applying a DC electric field to the flame reaction zone and providing control of the processes developing at thermochemical conversion of biomass (wood) pellets. The average heat power of the experimental device with continuous supply of pellets at an avera...

The aim of this study is to investigate the DC electric field effect on biomass gasification to provide effective control of processes developing at thermal decomposition of pelletized renewable fuels under oxygen rich conditions (a ≈ 0.06-0.12) and controllable production of combustible volatiles (CO, H2), which can be used as a fuel for energy pr...

Development of the swirling flame dynamics at thermo chemical conversion of biomass (wood pellets) has been investigated experimentally at a low swirl number of the swirling flame flow (S < 0.6) different rates of biomass thermal decomposition and swirling air supply with the aim to estimate key factors determining the formation of the flame dynami...

An experimental study was conducted by applying a DC electric field to the swirling flame of hydrocarbons with the aim to provide electric control of the gasification/combustion characteristics of biomass (wood pellets). An experimental study of the DC electric field effect on the biomass gasification/combustion characteristics was carried out by v...

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 swirlin...

An experimental study of the electric field effect on combustion dynamics at thermo-chemical conversion of biomass pellets was carried out with the aim to determine the DC field effect on the processes of biomass gasification, combustion of volatiles, formation of swirling flame structure, efficiency of heat energy production and composition of pol...

The main aim of this paper is improvement of the combustion characteristics of different biomass types (wood and agriculture residues, herbaceous biomass) by adding birch outer bark or bark (up to 20 %) to raw biomass with densification of the produced mixture. Produced pellets are experimentally characterized by elemental analysis determining the...

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-proce...

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 o...

The paper presents the results of an experimental study of the effect of high-frequency electromagnetic (EM) field oscillations on combustion and emission characteristics of biomass pellets with the aim to provide active control of the processes of biomass gasification and combustion. The effects of high frequency oscillations on the combustion cha...

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 effect...

A kinetic study on the combustion of a renewable energy resource - pelletized biomass - is carried out with the aim to obtain clean and effective energy production by minimizing the impact of the heat production process on the environment. To control the processes of biomass gasification, combustion of volatiles and heat energy production, a gradie...

The main aim of this study is to provide the experimental research of the combustion characteristics for the different types of the biomass pellets during their thermo chemical conversion with estimation the correlations between the main characteristics of pelletized plant biomass and combustion characteristics. The experiments include first, the p...

With the aim to provide a more effective utilization of different renewable energy resources for cleaner and more effective heat energy production, this work presents a complex experimental research and comparison of the chemical composition and combustion characteristics for different types of pelletized biomass fuels. Biomass pellets are produced...

Combustion characteristics of microwave (2.45 GHz) pre-treated biomass (wood) pellets are investigated experimentally with the aim to find out the effect of pellets pre-treatment on the biomass composition and the feasibility of their thermo-chemical conversion. A complex study of the main combustion characteristics of the pre-treated biomass sampl...

The main aim of the study was to develop and investigate a small-scale experimental gasification technique for the effective thermal decomposition of pelletized renewable fuels (wood sawdust, wheat straw). The technical solution of the biomass gasifier for gasification of renewable fuels presents a downdraft gasifier with controllable additional he...

The major goal of the research is to develop a stable, effective and controllable biomass gasification process and produce an environmentally friendly energy resource – fuel gas, which can be used in internal combustion engines for energy production. A pilot scale stratified downdraft gasifier has been developed with the aim to provide a controllab...

The focus of the recent experimental research is to provide control of the combustion dynamics and complex measurements (flame temperature, heat production rate, and composition of polluting emissions) for pelletized wood biomass using a non-uniform magnetic field that produces magnetic force interacting with magnetic moment of paramagnetic oxygen....

The paper presents results of complex experimental study of the composition and heating values as well as the combustion and emission characteristics of a pelletized biomass fuel produced from softwood and wheat straw non-hydrolyzed lignocellulosic residues (LHRs) of bioethanol production. Those biofuels can be estimated as prospective alternative...

When burning fossil fuels and renewable energy resources, greenhouse emissions (GHG) are emitted into the atmosphere. One of the options to reduce GHG emissions is to apply a magnetic field. The effect of a gradient magnetic field on the gasification of renewable fuel and the combustion of volatiles by applying the field to the bottom part of the s...

Magnetic field effect on combustion dynamics of the swirling flame flow is studied experimentally with the aim to obtain a cleaner and more effective combustion of a renewable fuel (wood pellets), providing a joint research of magnetic field effects on the swirling flame velocity field formation, processes of heat/mass transfer and combustion of vo...

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, temperat...

The experimental study of the electric field effects on combustion dynamics and emission characteristics of non-premixed swirling flame with the recirculation is carried out, providing electric control of the flame velocity field, determining the mixing rates of the flame compounds downstream the flame reaction zone with strong electric effect on t...

The main objective of recent study is to provide a clean and effective burnout of a renewable fuel (wood pellets) by co-firing the wood fuel with a fossil fuel - propane. The effect of swirl stabilized flame dynamics on the wet wood fuel burnout and composition of pollutant emissions is studied and analyzed at different rates of propane co-firing a...

The prime objective of the present study is to explore the basic mechanisms that control and stabilize the biomass combustion, and to study the processes involved in the formation of polluting emissions from the cofiring of wet wood biomass (wood pellets) with a premixed swirling propane/air flame flow. The influence of the cofiring on the chemical...

The DC electric field effect on the nonpremixed swirling flame dynamics, flame temperature and composition profiles is studied experimentally with the aim of establishing the feasibility of electric control of swirling combustion and formation of polluting emissions. The results testify that the electric field-enhanced mass transfer inside the inte...

An insight into the processes of electric field control of combustion dynamics and formation of the polluting emissions downstream the near-premixed swirling flame channel flow is presented. The results of experimental investigations allow the following conclusions: Under the conditions of the near-premixed swirling flame formation the most intensi...

The DC field effect on the kinetics of wood biomass co-firing with a fossil fuel (propane) is experimentally studied with the aim to provide electric control of the wood biomass devolatilization, ignition and burnout of the volatiles, resulting in the electric control over the production of main polluting emissions - NO_{x}, CO_{2}. To find out the...

Experimental investigations of the DC field effect on the swirling flame and the phenomena, which cause the formation of soot nanoparticles (carbon black) and greenhouse emissions (CO_{2}, NO_{x}), are carried out. Field-enhanced variations of the flame shape, structure, temperature profiles and the corresponding emission levels are studied for the...

Present experimental research refers to the problem of increased greenhouse emissions (CO_{2}, CH_{4}) from the combustion of the fossil fuels during the heat and energy production. Because high volumes of the carbon (CO_{2}) emissions to the Earth atmosphere promote the global warming, producing an appreciable effect on the climate change, differe...

The experimental investigations of the process of soot formation along the swirling flame flow are carried out with the aim to develop the effective process of carbon control from fuel combustion by converting the primary carbon-rich fuel into the fuel with reduced carbon amount. The results show that the processes of the formation of soot nanopart...

The experimental study of biofuel combustion is performed with the aim to obtain the clean combustion with reduced amount of unburned hydrocarbons, carbon monoxide and the rate of soot formation in a flame. The emphasis of recent investigations is on the domestic heat generation with biofuel (REE- rape oil ethylester) used as an additive to the gas...

The experimental investigations of the AC field effect on the propane combustion and processes that cause the formation of polluting emissions (NO_x, CO, CO_2) are performed. The AC-enhanced variations of the temperature and composition of polluting emissions are studied for the fuel-rich and fuel-lean conditions of the flame core. The results show...

This paper discusses the consequences of the radial electrical field effects on the sooting flame. The electric field-enhanced processes of heat/mass transfer, soot formation and deposition along the fuel-rich flame flow are studied with the aim to perform the electric control of the fuel combustion and flame decarbonization. The field-induced vari...

The experimental investigations of the electric field effect on the processes of soot formation and deposition are performed with the aim of achieving the electric control of fuel decarbonization and to reduce the levels of CO2 emissions in pollutants. The field-enhanced mass transfer of hydrocarbons and local variations of the rates of fuel combus...

Results of experimental studies of the radial electric field effect on the processes of heat and mass transfer and fuel combustion in flame channel flows are presented here. These investigations demonstrate the field-enhanced variations of the flame temperature and composition profiles and field-enhanced heat generation, which are determined by the...

The process of a chemical deposition of hard wear-resistant C-H coatings on a steel surface has been developed in a premixed propane-rich flame flow. The experimental investigations are performed under conditions of a field-induced dissociation and ionization of propane. The influence of a process of the sheath-convection of radical ions from a fla...

The results of a laboratory and both industrial experimental investigations of the interaction between a propane flame and external radial electric field are presented in this paper. The effect of the radial electric field on a flame is found by the local measurements of a flame temperature, composition and radiation of gas compounds. It is obtaine...

Diamond-like hard amorphous C:H films are deposited using a combined flame-field technique. The film deposition is carried out in a propane flame using field-induced dissociation of propane and transfer of hydrocarbon radicals to the negatively biased substrates. The electric field effect on the flame parameters and C:H film growth is studied. Inve...

The paper deals with an experimental study of radiative heat transfer and charge transfer processes from the surface of tantalum plates under conditions of unsteady high-temperature heating and oxidation. It is shown that at plate temperatures of 1800 K, the heat flux may be as high as 400 kW/sq m. Heating is shown to stimulate the emissivity of ta...

Experimental results are presented on the interaction of an argon arc-plasma jet with a transverse magnetic field for induction values of 0-0.6 T and gas temperatures at the nozzle of 3000-4000 K. The influence of the transverse field on the gasdynamic, electrical, and spectral characteristics of the jet is investigated. It is found that the change...

Electrical and microwave probes were used to determine the electron temperature and density of an argon plasma jet produced by an arc generator. It is shown that in the initial region of the jet the electron-to-atom temperature ratio is 2-3, and that the value of electron density considerably exceeds that calculated by the Saha formula at a given g...

Experiments were conducted to investigate the axial temperature distribution of single and two phase jets of argon plasma with particles of tungsten and titanium. The plasma was generated in an plasmatron whose arc current density varied from 100 to 300 amps producing temperature variations of argon beyond the nozzle section in the range 2000-5000...

The paper presents results of an experimental study of heat and mass transfer and charge transfer on titanium and zirconium surfaces undergoing chemical reactions and unsteady heating in a low temperature plasma of Ar and 4% O2. In the plasma temperature range 1800-3500 K, a close relation is established between the rate of heat release from the re...

The heat exchange of a chemically active titanium plate in a high-temperature flow of argon-air mixture is studied theoretically and experimentally. The plate temperature varies from 300 to 1800 K and the heating rate ranges from 130 to 150 deg per sec. It is shown that the kinetics of the chemical reactions on the metal surface in the ambient gas...

Magnetic-field-induced variations of swirl flame velocity, temperature, composition and combustion efficiency profiles at different stages of swirl flame formation are experimen-tally studied by varying the magnetic field strength. The results show that the magnetic field-enhanced mass transfer of paramagnetic and diamagnetic flame species signific...

Active electric control of combustion dynamics at different stages of wood fuel burnout have been investigated experimentally, using a small scale pilot device, the main elements of which are a wood fuel gasifier and a combustor with swirl-enhanced mixing of flame compounds and combustion of volatiles. The electric field (DC, AC) effect on wood fue...

Introduction. The intensive using of the fossil fuels (coal, fuel oil, natural gas, etc.) for heat generation results in the formation of huge amounts of green- house gases (CO2 ,N Ox ,C H4, etc.), released into the Earth's atmosphere, which evolve the greenhouse phenomenon, affecting the Earth climate and threatening the health of people. A way to...

The experimental investigations of the DC electric field effect on the swirling flame formation and processes that cause the formation of soot nanoparticles (carbon black) are carried out with the aim to perform the carbon sequesteration from the combustion of fossil fuels and to control the levels of greenhouse emissions (CO 2 , NO x), determining...

The paper presents the results of the experimental study of composition, heating values and combustion characteristics of granulated non-hydrolyzed residues (LHR) of separated hydrolysis and fermentation (SHF) wheat straw bioethanol processing. The LHRs ash content at 1.4-1.7 times exceeds the values for the native wheat straw samples. It was estab...