The effects of oxygen concentration and gas temperature on coal stream ignition and particle surface temperature in reducing-to-oxidizing environments

2020 ◽  
Author(s):  
Dishant Khatri ◽  
Zhiwei Yang ◽  
Richard L. Axelbaum
Keyword(s):  
Surface Temperature ◽  
Oxygen Concentration ◽  
Particle Surface ◽  
Gas Temperature

INFLUENCE OF DEPOSITION AND FOULING ON WALL TEMPERATURE DISTRIBUTION IN CONVECTIVE PATH

2020 ◽  
pp. 1-21
Author(s):  
Deli Li ◽  
Enlu Wang ◽  
Jinda Mao ◽  
Wei Wu ◽  
Yiyang Wang
Keyword(s):  
Temperature Distribution ◽  
Surface Temperature ◽  
Temperature Control ◽  
Theoretical Calculations ◽  
Influence Factors ◽  
Control Technology ◽  
Tube Surface ◽  
Gas Temperature ◽  
Surface Distribution ◽  
Super Heater

Abstract To develop a method of controlling the deposit tube surface temperature, the rules of deposition and fouling on the fireside, and the influence factors of the surface distribution were determined through experiments and theoretical calculations. The surface temperature distribution of a clean tube was compared with that of a deposit tube. Through theoretical calculations, the influence factors of the deposit tube surface temperature were evaluated. Based on the investigation, surface temperature control technology applicable to a super-heater was proposed and the feasibility of this heater was determined. A bimodal distribution was obtained when the temperature distribution of the deposit tube was plotted as a function of the angle, whereas a unimodal distribution was obtained for the clean tube. The results revealed that the heat exchange tube surface temperature is most effectively controlled by controlling the flue gas temperature. Prior to the development of higher performance materials (compared with conventional materials), surface temperature control technology can be used to ensure that the super-heater surface temperature lies below the allowable temperature of existing super-heater materials.

Preliminary Thermal Analyses on Diesel Converter Overheating

2004 ◽  
Author(s):  
Jun Zuo ◽  
Meiping Wang ◽  
Graham T. Reader ◽  
Ming Zheng
Keyword(s):  
Oxygen Concentration ◽  
Active Flow Control ◽  
Thermal Analyses ◽  
Gas Temperature ◽  
Engine Exhaust ◽  
Transient Model ◽  
Exhaust Temperature ◽  
Combustible Gas ◽  
Soot Loading ◽  
Reduce Emissions

The use of oxidation catalytic converters (OCC) in Diesel engines has proved to be an effective method to reduce emissions of total hydrocarbons (THC), carbon monoxide (CO), and the soluble organic fractions (SOF) of particulate matter (PM). However, the exothermal reaction effected by the oxidation of THC, CO, and especially the soot accumulated in the converters impose a risk of catalytic flow bed overheating that subsequently results in catalyst failure and may cause safety concerns. This paper presents a one-dimensional transient model that uses an energy balance method to analyze the overheating scenario when considering combustible gas reaction, clogged soot burning, and active flow control for a number of Diesel aftertreatment devices. The monolith temperature profiles were simulated by varying the exhaust gas temperature, oxygen concentration, and flow rate. Simulation results indicated that the potential of overheating elevates with increases in combustible gas concentration, soot loading, oxygen concentration, and engine exhaust temperature. The impacts of active control, such as flow reversal control, on converter overheating have also been investigated therein.

Time-Dependent Deposition Characteristics of Fine Coal Flyash in a Laboratory Gas Turbine Environment

2011 ◽  
Author(s):  
Robert G. Laycock ◽  
Thomas H. Fletcher
Keyword(s):  
Surface Temperature ◽  
Gas Turbine ◽  
Gas Flow ◽  
Coal Fly Ash ◽  
Time Dependent ◽  
Gas Temperature ◽  
Brigham Young University ◽  
Fine Coal ◽  
Two Samples ◽  
Nickel Base

Time-dependent deposition characteristics of fine coal flyash were measured in the Turbine Accelerated Deposition Facility (TADF) at Brigham Young University. Two samples of subbituminous coal fly ash, with mass mean diameters of 3 and 13 μm, were entrained in a hot gas flow with a gas temperature of 1250°C and Mach number of 0.25. A nickel base super alloy metal coupon approximately 0.3 cm thick was held in a hot particle-laden gas stream to simulate deposition in a gas turbine. Tests were conducted with deposition times of 20, 40, and 60 minutes. Capture efficiencies and surface roughness characteristics (e.g., Ra) were obtained at different times. Capture efficiency increased exponentially with time while Ra increased linearly with time. The increased deposition with time caused the surface temperature of the deposit to increase. The increased surface temperature caused more softening, increasing the propensity for impacting particles to stick to the surface. These data are important for improving models of deposition in turbines from syngas flows.

Use of Plate Thermometers for Better Estimate of Fire Development

2011 ◽  
Vol 82 ◽  
pp. 362-367 ◽  
Author(s):  
Alexandra Byström ◽  
Ulf Wickström ◽  
Milan Veljkovic
Keyword(s):  
Heat Transfer ◽  
Surface Temperature ◽  
Large Scale ◽  
Thermal Exposure ◽  
Alternative Methods ◽  
Gas Temperature ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Weighted Mean Temperature ◽  
Adiabatic Surface

The concept of Adiabatic Surface Temperature (AST) opens possibilities to calculate heat transfer to a solid surface based on one temperature instead of two as is needed when heat transfer by both radiation and convection must be considered. The Adiabatic Surface Temperature is defined as the temperature of a surface which cannot absorb or lose heat to the environment, i.e. a perfect insulator. Accordingly, the AST is a weighted mean temperature of the radiation temperature and the gas temperature depending on the heat transfer coefficients. A determining factor for introducing the concept of AST is that it can be measured with a cheap and robust method called the plate thermometer (PT), even under harsh fire conditions. Alternative methods for measuring thermal exposure under similar conditions involve water cooled heat flux meters that are in most realistic situations difficult to use and very costly and impractical. This paper presents examples concerning how the concept of AST can be used in practice both in reaction-to-fire tests and in large scale scenarios where structures are exposed to high and inhomogeneous temperature conditions.

scholarly journals Micro-interface temperature field of catalytic particle under self-rotation regulation

2020 ◽  
Vol 194 ◽  
pp. 05002
Author(s):  
Lei Xu ◽  
Hualin Wang ◽  
Yuan Huang
Keyword(s):  
Surface Temperature ◽  
High Efficiency ◽  
Rotation Speed ◽  
Catalytic Reduction ◽  
Particle Surface ◽  
Reduction Reaction ◽  
The Self ◽  
Spherical Particles ◽  
Interface Temperature ◽  
Catalytic Particle

The micro-interface formed inside and on the surface of the catalytic particle is the place where the catalytic reaction proceeds. The micro-interface temperature is one of the important factors determining the reaction efficiency. Numerical simulation was used to investigate the fluid-solid coupled heat transfer law of micro-interface under the regulation of spherical particles’ self-rotation. The results show it takes up to 4.78 s that the average surface temperature of non-rotating particle with a diameter of 3 mm decreases from 300 ℃ to 150 ℃, which is the lowest temperature required for high-efficiency selective catalytic reduction reaction of NOx with NH3, while self-rotation can reduce the cooling rate of particles. When the direction of particle self-rotation is perpendicular to gas velocity, as the self-rotation speed increases, the high-temperature area of the particle surface diffuses more fully to the latitude direction. Significant effect can be made as the self-rotation speed reaches 5 rad/s, the uniformity of the surface temperature can be increased by 27.1 % ~ 37.7 % compared with non-rotating particle, and the uniformity can be increased by a maximum of 49.5 % at a self-rotation speed of 500 rad/s.

Thermo-swing insulation to reduce heat loss from the combustion chamber wall of a diesel engine

2019 ◽  
Vol 20 (7) ◽  
pp. 805-816 ◽  
Author(s):  
Akio Kawaguchi ◽  
Yoshifumi Wakisaka ◽  
Naoki Nishikawa ◽  
Hidemasa Kosaka ◽  
Hideo Yamashita ◽  
...  
Keyword(s):  
Surface Temperature ◽  
Combustion Chamber ◽  
Heat Loss ◽  
Diesel Engines ◽  
Chamber Wall ◽  
Gas Temperature ◽  
Gasoline Engines ◽  
Air Heating ◽  
Developed Surface ◽  
Insulation Coating

Cooling heat loss is one of the most dominant losses among the various engine losses to be reduced. Although many attempts to reduce it by insulating the combustion chamber wall have been carried out, most of them have not been successful. Charge air heating by the constantly high temperature insulating wall is a significant issue, because it deteriorates charging efficiency, increases the emissions of soot and NOx in diesel engines, and promotes the knock occurrence tendency in gasoline engines. A new concept heat insulation methodology which can reduce cooling heat loss without heating the charging air has been developed. Surface temperature of insulation coating on the combustion chamber wall changes rapidly, according to the quickly changing in-cylinder gas temperature in each engine stroke. During the compression and expansion stroke, the surface temperature of the insulation coating goes up rapidly, and consequently, the heat transfer becomes lower by the reduced temperature difference between the surface and the gas. During the intake stroke, the surface temperature goes down rapidly, and it prevents intake air heating from the wall. To realize the above-mentioned functionality, a thin coating layer with low thermal conductivity and low heat capacity was developed. It was applied on the pistons of diesel engines, and showed improvement in thermal efficiency. It also showed a reduction of unburnt fuel emission in low temperature engine starting condition. The energy balance analysis showed reduction of cooling heat loss and, on the contrary, increase in the brake power and the exhaust loss.

Sign in / Sign up

Export Citation Format

Share Document