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

2017 ◽  
Vol 54 (3) ◽  
pp. 30-39 ◽  
Author(s):  
I. Barmina ◽  
R. Valdmanis ◽  
M. Zaķe
Keyword(s):  
Nozzle Diameter ◽  
Biomass Combustion ◽  
Heat Output ◽  
Complete Combustion ◽  
Combustion Dynamics ◽  
Air Supply ◽  
Flow Formation ◽  
Swirl Intensity ◽  
Inlet Conditions ◽  
Upstream Flow

AbstractThe 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.

Characterization of Combustion Dynamics in Swirl Stabilized Flames

2009 ◽  
Author(s):  
Uyi Idahosa ◽  
Abhishek Saha ◽  
Chengying Xu ◽  
Saptarshi Basu
Keyword(s):  
Heat Release ◽  
Frequency Response ◽  
Equivalence Ratio ◽  
Swirl Number ◽  
Combustion Dynamics ◽  
Flow Rates ◽  
Fuel Flow ◽  
Air Supply ◽  
Swirl Intensity ◽  
Air Speed

This paper investigates flame frequency response relative to changes in swirl intensity and equivalence ratio in a non-premixed swirl stabilized burner. The degree of swirl in the burner is characterized by the swirl number (S) provided by circumferentially distributed air supply ports directed tangentially to the main axial air flow. Equivalence ratio variations are induced using varying constant, linear ramp and exponentially decaying fuel (propane) flow rates towards blowoff. The variations in the air speed at the exit of the burner (U) are measured with an anemometer located at the base of the flame. The emission of CH* radicals (I) is used as a marker of flame heat release and is measured using a photomultiplier (PMT). The frequency response of the PMT heat release and burner velocity signals are analyzed in the frequency domain using the Fast Fourier Transform (FFT) and Continuous Wavelet Transform (CWT) methods. Amplification in the power of heat release fluctuation is observed in low swirl flames close to blowoff. This effect is found to be reversed in higher swirl number flames even close to blowoff. In dynamic approaches to blowoff (using ramp and decaying fuel flow rates), the dominant heat release fluctuation frequencies are observed to be similar to perturbation frequencies in lean flames hovering at constant fuel flow rates close to blowoff.

Conceptual Analysis of Air Supply Systems For In-Flight PEM-FC

2006 ◽  
Author(s):  
Lukas P. Barchewitz ◽  
Joerg R. Seume
Keyword(s):  
Fuel Cell ◽  
Combustion Chamber ◽  
High Efficiency ◽  
Combustion Engine ◽  
Pressure Ratio ◽  
Inlet Temperature ◽  
Thermodynamic Evaluation ◽  
Radial Turbine ◽  
Air Supply ◽  
Inlet Conditions

To cover the increasing demand of on-board electrical power and for further reduction of emissions, the conventional auxiliary power unit (APU) shall be replaced by a fuel cell system. The main components are a compressor-turbine unit, a kerosene reformer, and the fuel cell. Polymer exchange membrane fuel cells (PEM-FC) are favoured because of their currently advanced level of development. During in-flight operation, the inlet conditions of the PEM-FC system must be kept constant in order to avoid mechanical and thermal damage of the membrane and to ensure low levels of pressure fluctuations in the reformer section. A centrifugal compressor is chosen for pressurization of the system. The advantages of turbomachinery are low specific weight, high efficiency, and good controllability by inlet guide vanes and/or adjustable diffuser vanes. To drive the compressor, a radial turbine is used so that the air supply system resembles the turbocharger for a combustion engine (Fig. 1). A steady state thermodynamic evaluation of the entire system is carried out to identify an optimal system configuration that covers the large range of pressure, temperature, and humidity of ground operation of the aircraft in various regions on the earth as well as take-off, cruise, and landing. A catalytic combustion chamber is located between the PEM-FC and the radial turbine. In this combustion chamber, the hydrogen which is not used in the fuel cell is used to raise the turbine inlet temperature (TIT) and thus the mechanical power delivered by the turbine. To overcome an additional pressure loss of the reformer section, which occurs in the anode stream, an additional low-pressure-ratio compressor is used. The result is a highly thermally integrated PEM-FC system with three centrifugal turbomachines.

scholarly journals Low Emissions Resulting from Combustion of Forest Biomass in a Small Scale Heating Device

Energies ◽  
2020 ◽  
Vol 13 (20) ◽  
pp. 5495
Author(s):  
Karol Tucki ◽  
Olga Orynycz ◽  
Andrzej Wasiak ◽  
Antoni Świć ◽  
Leszek Mieszkalski ◽  
...  
Keyword(s):  
Combustion Process ◽  
The Other ◽  
Screw Conveyor ◽  
Small Scale ◽  
Heat Output ◽  
Maximum Heat ◽  
Heating Device ◽  
Air Supply ◽  
Low Emission ◽  
Secondary Air

The paper concerns the analysis of harmful emissions during the combustion process in households. The subject of the analysis is a low emission heating device with an output of 50 kW for burning biomass of forest origin (low-quality hardwoods or softwoods). The proposed boiler is automatically fed from the connected container by means of a screw conveyor. In this way, the optimum amount of fuel is supplied for maximum heat output (adjustment of the ratio of primary air to fuel). The proposed biomass heating system is equipped with a primary and secondary air supply system and exhaust gas sensors. This ensures optimal regulation of the air mixture and efficient and clean combustion. Proper control of the combustion process, control of the air supply by means of a lambda sensor and power control of the system ensure a low-emission combustion process. The system precisely adjusts to the heat demand. This results in highly efficient heating technology with low operating costs. In the presented work, the emission of exhaust gases from the proposed heating device during the combustion of woodchips and beech–oak pellets were measured. It is demonstrated that the proposed design of the boiler equipped with intelligent control significantly reduces emissions when the biomass solid fuels are used, e.g., CO emissions from beech and oak chips and pellets in the low-emission boiler—18 extract pipes shows the value <100 ppm, which is even lower than when gas is burned in the other boilers; on the other hand, the pine chips show even higher emission when burned in the low-emission burner. Consequently, the choice of biomass source and form of the fuel play some role in the emissions observed.

Combustion Mechanism of Rich-Lean Flame Burner Controlled Boundary Zone

2007 ◽  
Author(s):  
Shuichi Aoki ◽  
Hiroshi Yamazaki
Keyword(s):  
Numerical Simulation ◽  
Hot Water ◽  
Maximum Temperature ◽  
Boundary Zone ◽  
Flame Zone ◽  
Complete Combustion ◽  
Domestic Hot Water ◽  
Air Supply ◽  
Lean Premixed ◽  
The Rich

Rich-lean flame burners are widely used for supplying domestic hot water and heating in Japan. These burners exhaust low NOx and CO emissions, and conventionally consist of a layered structure of lean flame with two sides of rich flame. Top-runner regulation applied for the domestic hot water generator of fuel gas, is to run to achieve the CO2 reduction two years later in Japan. Not only low NOx and CO emissions, but also higher efficiency, are required for the next generation of domestic hot water generators. Kurachi et al. confirmed experimentally that a new concept, a unique burner with air supplied from the boundary zone between the rich and lean premixed gas nozzles, produces lower NOx and CO emissions (1, 2, 3). Numerous experimental and numerical simulation studies of conventional rich-lean flame burners have been reported, and the mechanism of the complex field mixed with the rich and lean premixed gas has been clarified (4). But the characteristics of the new concept burner have only been investigated experimentally. In this study, a two-dimensional numerical simulation of the new burner was executed to clarify the mechanism of the lower NOx and CO emissions compared to the conventional burner (mesh; 25,000, chemical reaction; GRI-mech II, laminar flow). Heat input was 6.5kW (half of a full load). A conventional burner, without an air supply from the boundary zone, was also calculated to compare with the new concept burner. In a conventional burner, the reaction ratio R178 (N+NO = N2+O), which is a part of the Zeldovich mechanism, is dominant at the area downstream of the rich flame. This area is almost same as the maximum temperature area of the burned gas. The maximum temperature of the new concept burner (1,923K) is approximately 50K lower than that of the conventional burner, successfully maintaining stable combustion. Because of its lower maximum temperature, the amount of NOx emission from the new concept burner is approximately 40% of that from the conventional burner. With the air supply from the boundary zone, the concentration of CO in the flue gas also is decreased by approximately 1/3. In particular, the formation of thermal NOx in the lean flame zone is suppressed by lowering the flame temperature. The amount of CO emission from the rich flame zone is also decreased due to the promotion of complete combustion with the air supply from the boundary zone. As a result, these characteristics are in relatively good agreement with the experimental results, and the dominancy of the new concept burner is also clarified.

Numerical Simulation of Combustion Process in a 350t/d MSW Incinerator

2012 ◽  
Vol 268-270 ◽  
pp. 898-901
Author(s):  
Shui E Yin ◽  
Jun Wu
Keyword(s):  
Numerical Simulation ◽  
Mathematical Model ◽  
Combustion Process ◽  
Species Distributions ◽  
Complete Combustion ◽  
Operational Conditions ◽  
Furnace Outlet ◽  
Air Supply ◽  
Total Temperature ◽  
Secondary Air

A mathematical model was presented for the combustion of municipal solid waste in a 350t/d MSW-burning incinerator. Numerical simulations were performed to predict the temperature and the species distributions in the furnace, with practical operational conditions taken into account. When the total air supply is constant, reducing primary air and increasing secondary air properly results in the higher total temperature of the furnace and the more oxygen concentration at the furnace outlet, and thereby contributes to the complete combustion of combustibles so that an optimal combustion effect can be achieved.

scholarly journals Investigations of combustion process in combined cooker-boiler fired on solid fuels

2006 ◽  
Vol 10 (4) ◽  
pp. 121-130
Author(s):  
Dragoslava Stojiljkovic ◽  
Vladimir Jovanovic ◽  
Milan Radovanovic ◽  
Nebojsa Manic ◽  
Ivo Radulovic
Keyword(s):  
Flue Gas ◽  
Combustion Process ◽  
Solid Fuels ◽  
Gas Temperature ◽  
Weight Changes ◽  
Complete Combustion ◽  
Air Supply ◽  
Class 1 ◽  
Secondary Air ◽  
Co Emission

The aim of the investigation was to make some reconstructions on the existing stove used for cooking and baking and to obtain the combined cooker-boiler which will fulfill the demands of European standard EN 12815. Implementation of modern scientific achievements in the field of combustion on stoves and furnaces fired on solid fuels was used. During the investigations four various constructions were made with different fresh air inlet and secondary air supply with the intention to obtain more complete combustion with increased efficiency and reduced CO emission. Three different fuels were used: firewood, coal, and wood briquette. A numerous parameters were measured: fuel weight changes during the combustion process, temperature of inlet and outlet water, flue gas composition (O2, CO, SO2, CO2, NOx), flue gas temperature, ash quantity etc. The result of the investigations is the stove with the efficiency of more than 75% - boiler Class 1 (according EN 12815) and CO emission of about 1% v/v. The results obtained during the measurements were used as parameters for modeling of combustion process. .

Experimental Study on Non-Pulverized Wood Biomass Combustion With a New Three-Way Swirling Combustion Cyclone Combustor

2019 ◽  
Vol 12 (3) ◽  
Author(s):  
Kangil Choe ◽  
Yangho Lee ◽  
Soongul Lee ◽  
Michael Weedon
Keyword(s):  
Experimental Study ◽  
Removal Rate ◽  
Maximum Temperature ◽  
Biomass Combustion ◽  
Slag Formation ◽  
Wood Biomass ◽  
Complete Combustion ◽  
Cyclone Combustor ◽  
Combustion Technology ◽  
Future Work

Abstract An experimental study presents a new innovative cyclone combustor, known as the three-way swirling combustion (TSC), utilizing non-pulverized wood biomass. The study shows that the combustor reached near-complete combustion, as evident in the measurements of CO and NOx emissions, and the excess air ratio. It also demonstrates the unique features of the TSC combustor, which includes an air curtain insulation effect with a high ash removal rate that reduces clinker and slag formation, alongside a chamber that does not need a refractory brick. It compares against conventional combustion technology, such as the stoker and the fluidized bed in terms of the amount of emission gases, maximum temperature, and excessive air ratio. Six geometrical and operational design criteria of the TSC for wood biomass combustion are identified for future work of design optimization. Ultimately, the implementation of the TSC for non-pulverized wood biomass and possibly for other biomass holds great potential for economically and technically beneficial incineration and power generation.

Numerical investigation of the effect of air supply and oxygen enrichment on the biomass combustion in the grate boiler

2019 ◽  
Vol 156 ◽  
pp. 550-561 ◽  
Author(s):  
Anqi Zhou ◽  
Hongpeng Xu ◽  
Yaojie Tu ◽  
Feiyang Zhao ◽  
Zhiming Zheng ◽  
...  
Keyword(s):  
Numerical Investigation ◽  
Oxygen Enrichment ◽  
Biomass Combustion ◽  
Air Supply

CFD simulations of the effect of inlet conditions on Taylor flow formation

2008 ◽  
Vol 29 (6) ◽  
pp. 1603-1611 ◽  
Author(s):  
N. Shao ◽  
W. Salman ◽  
A. Gavriilidis ◽  
P. Angeli
Keyword(s):  
Cfd Simulations ◽  
Taylor Flow ◽  
Flow Formation ◽  
Inlet Conditions

Towards a new paradigm in fire severity research using dose–response experiments

2016 ◽  
Vol 25 (2) ◽  
pp. 158 ◽  
Author(s):  
Alistair M. S. Smith ◽  
Aaron M. Sparks ◽  
Crystal A. Kolden ◽  
John T. Abatzoglou ◽  
Alan F. Talhelm ◽  
...  
Keyword(s):  
Dose Response ◽  
Vegetation Index ◽  
Alternative Pathway ◽  
Fire Severity ◽  
Fire Effects ◽  
Heat Output ◽  
New Paradigm ◽  
Combustion Dynamics ◽  
Leaf Level ◽  
Reflectance Indices

Most landscape-scale fire severity research relies on correlations between field measures of fire effects and relatively simple spectral reflectance indices that are not direct measures of heat output or changes in plant physiology. Although many authors have highlighted limitations of this approach and called for improved assessments of severity, others have suggested that the operational utility of such a simple approach makes it acceptable. An alternative pathway to evaluate fire severity that bridges fire combustion dynamics and ecophysiology via dose–response experiments is presented. We provide an illustrative example from a controlled nursery combustion laboratory experiment. In this example, severity is defined through changes in the ability of the plant to assimilate carbon at the leaf level. We also explore changes in the Differenced Normalised Differenced Vegetation Index (dNDVI) and the Differenced Normalised Burn Ratio (dNBR) as intermediate spectral indices. We demonstrate the potential of this methodology and propose dose–response metrics for quantifying severity in terms of carbon cycle processes.

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