Numerical Simulation of Thermodynamic Parameters during Diffusion Combustion for Vehicle Air Heater

2011 ◽  
Vol 80-81 ◽  
pp. 783-787
Author(s):  
Pei Yong Ni ◽  
Xiang Li Wang ◽  
Sheng Li Wei
Keyword(s):  
Heat Flux ◽  
Turbulence Intensity ◽  
Gas Flow ◽  
Diffusion Combustion ◽  
Operation Condition ◽  
Radial Temperature ◽  
Air Heater ◽  
Exhaust Temperature ◽  
Excess Air ◽  
Excess Air Coefficient

The diffusion combustion of the air heater was numerically simulated at different excess air coefficient using Fluent software. The distributions of the temperature, gas flow velocity, and turbulence intensity were present. And the heat flux was calculated. The result showed that the excess air coefficient had a little effect on the maximum combustion temperature distribution. As the excess air coefficient increased, the axial temperature at first increased and then decreased, and in contrast both the total heat flux and radiation heat flux decreased. The radial temperature, velocity and turbulence intensity increased firstly and then decreased at the same operation condition. The measured exhaust temperature increased with time. At 90 second, it was about 250 °C, which showed good agreement with simulation result. This provides theory basis for the reform of the heater.

scholarly journals Effect Analysis on Combustion and Emission Characteristics of a Rotary Burner Fueled by Biomass Pellet Fuel

2020 ◽  
Vol 2020 ◽  
pp. 1-12
Author(s):  
Guohai Jia ◽  
Lijun Li ◽  
D. M. Zhang
Keyword(s):  
Gas Flow ◽  
Combustion Temperature ◽  
Concentration Field ◽  
Large Temperature ◽  
Middle Region ◽  
Steady State Condition ◽  
Excess Air ◽  
Excess Air Coefficient ◽  
Simulation Results ◽  
Biomass Pellet

A biomass pellet rotary burner was chosen as the research object, in order to study the influence of excess air coefficient on the combustion phenomenon of biomass rotary burner, the finite element simulation model of a biomass rotary burner was established, and simulation results of a biomass rotary burner were verified by the experiment. The computational fluid dynamics software was applied to simulate the combustion characteristics of biomass rotary burner in a steady-state condition, and the effect of excess air coefficient on temperature field and component concentration field in biomass rotary burner was analyzed. The results show that the flue gas flow rate inside the burner gradually increases with the increase of air velocity, the area with large temperature is mainly concentrated in the middle region of the rotary burner, and the maximum combustion temperature also appeared in the middle region of the combustion chamber, and the formation area of CO decreases with the increase of excess air coefficient. CO2 is mainly concentrated in the middle region of the burner, and the CO2 generating region decreases with the increase of excess air coefficient. The experimental value of the combustion temperature of the biomass rotary burner is in good agreement with the simulation results.

Modeling and Experiment on Combustion Characteristics for Biomass Rotary Burner

2020 ◽  
Vol 04 ◽  
Author(s):  
Guohai Jia ◽  
Lijun Li ◽  
Li Dai ◽  
Zicheng Gao ◽  
Jiping Li
Keyword(s):  
Combustion Chamber ◽  
Combustion Temperature ◽  
Combustion Efficiency ◽  
Middle Part ◽  
Combustion Characteristics ◽  
Maximum Temperature ◽  
Excess Air ◽  
Element Simulation ◽  
Excess Air Coefficient ◽  
Secondary Air

Background: A biomass pellet rotary burner was chosen as the research object in order to study the influence of excess air coefficient on the combustion efficiency. The finite element simulation model of biomass rotary burner was established. Methods: The computational fluid dynamics software was applied to simulate the combustion characteristics of biomass rotary burner in steady condition and the effects of excess air ratio on pressure field, velocity field and temperature field was analyzed. Results: The results show that the flow velocity inside the burner gradually increases with the increase of inlet velocity and the maximum combustion temperature is also appeared in the middle part of the combustion chamber. Conclusion: When the excess air coefficient is 1.0 with the secondary air outlet velocity of 4.16 m/s, the maximum temperature of the rotary combustion chamber is 2730K with the secondary air outlet velocity of 6.66 m/s. When the excess air ratio is 1.6, the maximum temperature of the rotary combustion chamber is 2410K. When the air ratio is 2.4, the maximum temperature of the rotary combustion chamber is 2340K with the secondary air outlet velocity of 9.99 m/s. The best excess air coefficient is 1.0. The experimental value of combustion temperature of biomass rotary burner is in good agreement with the simulation results.

Effect of thermal input, excess air coefficient and combustion mode on natural gas MILD combustion in industrial-scale furnace

Fuel ◽  
2021 ◽  
Vol 302 ◽  
pp. 121179
Author(s):  
Mingming Huang ◽  
Ruichuan Li ◽  
Jikang Xu ◽  
Shen Cheng ◽  
Haoxin Deng ◽  
...  
Keyword(s):  
Natural Gas ◽  
Industrial Scale ◽  
Combustion Mode ◽  
Mild Combustion ◽  
Excess Air ◽  
Excess Air Coefficient

scholarly journals High-Fidelity Simulations of a Linear HPT Vane Cascade Subject to Varying Inlet Turbulence

2017 ◽  
Author(s):  
Richard Pichler ◽  
Richard D. Sandberg ◽  
Gregory Laskowski ◽  
Vittorio Michelassi
Keyword(s):  
Heat Flux ◽  
Turbulence Intensity ◽  
Side Surface ◽  
Suction Side ◽  
Transition Process ◽  
Length Scale ◽  
Length Scales ◽  
Inflow Turbulence ◽  
High Turbulence ◽  
Turbulence Length

The effect of inflow turbulence intensity and turbulence length scales have been studied for a linear high-pressure turbine vane cascade at Reis = 590,000 and Mis = 0.93, using highly resolved compressible large-eddy simulations employing the WALE turbulence model. The turbulence intensity was varied between 6% and 20% while values of the turbulence length scales were prescribed between 5% and 20% of axial chord. The analysis focused on characterizing the inlet turbulence and quantifying the effect of the inlet turbulence variations on the vane boundary layers, in particular on the heat flux to the blade. The transition location on the suction side of the vane was found to be highly sensitive to both turbulence intensity and length scale, with the case with turbulence intensity 20% and 20% length scale showing by far the earliest onset of transition and much higher levels of heat flux over the entire vane. It was also found that the transition process was highly intermittent and local, with spanwise parts of the suction side surface of the vane remaining laminar all the way to the trailing edge even for high turbulence intensity cases.

Energy Efficiency Improvement of Diesel Aftertreatment With Flow Reversal and Central Fuelling

2007 ◽  
Author(s):  
Ming Zheng ◽  
Siddhartha Banerjee ◽  
Xiaohong Xu ◽  
Usman Asad ◽  
Xiaoye Han ◽  
...  
Keyword(s):  
Gas Flow ◽  
Flow Reversal ◽  
Regeneration Rate ◽  
Exhaust Temperature ◽  
Energy Efficiency Improvement ◽  
Unidirectional Flow ◽  
Central Heating ◽  
Fuel Delivery ◽  
Delivery Technique ◽  
Substrate Properties

Empirical and theoretical studies are made between the inlet and central heating schemes in a flow reversal embedment of diesel aftertreatment converters in order to investigate the influences of gas flow, heat transfer, chemical reaction, oxygen concentration, and substrate properties. The periodic flow reversal converter is found effective to treat engine exhausts that are difficult to cope with conventional unidirectional flow converters. However, the previous work indicates that the exhaust temperature from modern diesel engines is commonly insufficient to sustain a high conversion or regeneration rate and thus supplemental heating techniques are commonly applied. A technique of fuelling at the central region of a flow-reversal embedment is found more energy-efficient to raise the temperature of the catalytic flow-bed and therefore to drastically reduce the supplemental heating to the substrate. An effective fuel delivery technique has been tested to improve the fuel dispersion of the central fuel delivery strategy at various engine-out exhaust temperatures, compositions, and flow rates.

Effects of Air Flowrate on the Combustion and Emissions of Blended Corn Straw and Pinewood Wastes

2018 ◽  
Vol 141 (4) ◽  
Author(s):  
Xiaoxiao Meng ◽  
Wei Zhou ◽  
Emad Rokni ◽  
Honghua Zhao ◽  
Rui Sun ◽  
...  
Keyword(s):  
Gas Phase ◽  
Ignition Delay Time ◽  
Fixed Bed ◽  
Combustion Efficiency ◽  
Fixed Bed Reactor ◽  
Corn Straw ◽  
Excess Air ◽  
Burning Rates ◽  
Excess Air Coefficient ◽  
Hazardous Pollutants

This research investigated the effects of the specific primary (under-fire) air flowrate (m˙air) on the combustion behavior of a 50–50 wt % blend of raw corn straw (CS) and raw pinewood wastes in a fixed-bed reactor. This parameter was varied in the range of 0.079–0.226 kg m−2 s−1, which changed the overall combustion stoichiometry from air-lean (excess air coefficient λ = 0.73) to air-rich (excess air coefficient λ = 1.25) and affected the combustion efficiency and stability as well as the emissions of hazardous pollutants. It was observed that by increasing m˙air, the ignition delay time first increased and then decreased, the average bed temperatures increased, both the average flame propagation rates and the fuel burning rates increased, and the combustion efficiencies also increased. The emissions of CO as well as those of cumulative gas phase nitrogen compounds increased, the latter mostly because of increasing HCN, while those of NO were rather constant. The emissions of HCl decreased but those of other chlorine-containing species increased. The effect of m˙air on the conversion of sulfur to SO2 was minor. By considering all of the aforesaid factors, a mildly overall air-rich (fuel-lean) (λ = 1.04) operating condition can be suggested for corn-straw/pinewood burning fixed-bed grate-fired reactors.

Numerically Study on Combustion and NOx Emission Characteristics in Tangentially Fired Boiler Co-Firing Semi-Coke

2018 ◽  
Author(s):  
Yongbo Du ◽  
Chang'an Wang ◽  
Pengqian Wang ◽  
Qiang Lv ◽  
Defu Che
Keyword(s):  
Bituminous Coal ◽  
Combustion Efficiency ◽  
Low Rank ◽  
Operation Performance ◽  
Combustion Heat ◽  
Practical Utilization ◽  
Excess Air ◽  
Utility Boilers ◽  
Excess Air Coefficient ◽  
Char Burnout

Semi-coke is a specific solid fuel, which is mainly produced by upgrading low-rank coal. The poor reactivity of semi-coke makes a difficulty to its practical utilization in utility boilers. Previous research was mainly focused on the combustion behavior of semi-coke, while the industrial application has to be understood. In this paper, the effect of co-firing semi-coke and bituminous coal on the operation performance of pulverized boiler was numerically studied. The work was conducted on a 300 MW tangentially fired boiler, and the temperature distribution, the char burnout and NOx production were mainly examined. The results indicate that the incomplete combustion heat loss drops with the increase in semi-coke blending ratio. The NOx concentration increases from 186 mg/Nm3 for only firing the bituminous coal to 200, 214, and 255 mg/Nm3, when the blending ratio was 17%, 33% and 50%, respectively. With enhancing excess air coefficient for the co-firing condition, the combustion efficiency got improved, while NOx production increased very slightly. In general, the boiler is well adapted to co-firing semi-coke, and the semi-coke blending ratio of 1/3 with an excess air coefficient of 1.235 is recommended.

Numerical Simulation on Moisture Influence to MSW Combustion

2014 ◽  
Vol 1006-1007 ◽  
pp. 181-184
Author(s):  
Zhu Sen Yang ◽  
Xing Hua Liu ◽  
Shu Chen
Keyword(s):  
Numerical Simulation ◽  
Moisture Content ◽  
Flue Gas ◽  
Combustion Process ◽  
Average Temperature ◽  
Excess Air ◽  
Heat Value ◽  
Moisture Influence ◽  
Excess Air Coefficient ◽  
Combustible Gases

The combustion process of municipal solid waste (MSW) in a operating 750t/d grate furnace in Guangzhou was researched by means of numerical simulation. The influence of MSW moisture content on burning effect was discussed. The results show that: with the moisture content dropped from 50% to 30%, the heat value could be evaluated from 13.72% to 54.91% and the average temperature in the furnace could be promoted 90-248°C. However, the combustible gases and particle in the flue gas of outlet would take up a high proportion since lacking of oxygen would lead to an incomplete combustion. The excess air coefficient should be increased to 2.043~2.593 in order to ensure the flue gas residence time more than 2s and temperature in the furnace higher to 800°C.

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