Papers by Keyword: Combustion

Abstract: This study investigates numerically the NOx reduction by SNCR in a CO boiler. The combustion and fluid flow in the FPC CO boiler is examined with emphasis on the influence of the injection position of reducing agent on NOx reduction. Simulation results indicate that NOx is formed mainly in the high temperature region near the boiler inlet where the mixing caused by swirler is strong. Among the reducing agent injection positions investigated, the boiler inlet has the best NOx reduction efficiency, while 0.5m behind the boiler inlet is the worst. When reducing agent is injected from the boiler inlet, a NOx reduction efficiency of 51% is achieved if default amount of reducing agent is injected. When reducing agent is injected from 3.6m behind the boiler inlet, the NOx reduction efficiency is 14% for default amount of reducing agent. The injection position of reducing agent has a siginificant influence on the NOx reduction efficiency. Better injection positions for NOx reduction should be where reducing agent can pass through a region where temperature is suitable for the SNCR reaction or residence time of reducing agent in the SNCR reaction region can be longer, e.g., the boiler inlet or the downstream region of the oxidizer lower portion where recirculation exists.

Abstract: Mercury is one of important trace heavy metal elements and about 1/3 of mercury in the air comes from emissions of coal-fired flue gas. In this study, we simulated mercury’s 4 important reactions of the oxidation kinetics mechanism and got every reactions’ rate variations; meanwhile we studied the kinetics of four reactions and got the reacting paths, five pre-exponential factor in different temperatures, reaction activation energy change and reaction rate constant change, a relatively comprehensive homogeneous oxidation model established. Through the above simulation study, the kinetics and thermodynamics parameters of 4 primitive reactions are obtained, having a great benefit for understanding the transformation mechanism of mercury in the process of coal combustion.

Abstract: The influence of air distribution modes on boiler efficiency was researched by combustion adjustment tests. Boiler efficiency variation was studied by changing factors such as oxygen content, upper tertiary air, over fire air and secondary air distribution modes. Boiler efficiency reached maximum under 3.9% design oxygen content. Carbon content in fly ash increased as upper tertiary air ratio, consequently boiler efficiency declined. Average furnace flame temperature decreased inversely as over fire air baffle opening, and boiler efficiency variation was small. Under different conditions, boiler efficiency varied within 1.12%. Beam waist air distribution mode obtained the highest boiler efficiency.

Abstract: Combustion adjustment tests about air distribution modes were performed on 1 025 t/h boiler for NO_x emission controlling. NO_x emission was affected by factors such as oxygen content, upper tertiary air, over fire air and secondary air distribution modes. Fuel-NO_x raised drastically with the increase of oxygen content. NO_x concentration declined with the rise of upper tertiary air ratio. Both average flame temperature and NO_x emission concentration decreased inversely with over fire air. Beam waist mode had the lowest NO_x emission concentration among different air distribution modes. It emitted less 14.2% NO_x than that of balanced air distribution mode. NOx concentration can be reduced 10%-20% by combustion adjustment.

Abstract: The performance of engine fueled with biodiesel was tested. It was indicated from the experimental results that NOx emission of biodiesel reduced significantly with decreasing fuel delivery advance angle BTDC, while soot emission also reduced when the fuel delivery timing was retarded for 2°CA, and the starting position of heat release rate retarded with the delay of fuel delivery timing. It can be concluded that, retarding fuel delivery timing was an effective method to reduce the NOx emission of engine fueled with biodiesel, but led to reduce the brake power output slightly.

Abstract: This paper has studied the influence of the different ratio on combustion process and emissions of air premixed methanol/diesel dual fuel engine. The research was based on 4B26 diesel engine, and the 3-D numerical simulation on combustion process and emissions of the diesel engine with intake premixed methanol was carried out using AVL FIRE software. The study showed that,with the compression ratio reducing,the ignition delay period prolonged, and the ignition timing delayed, the maximum firing pressure, the peak of pressure rise rate and the maximum combustion temperature in cylinder decreased, the crank angle postponed, the NOX emission decreased and the Soot emission increased obviously.

Abstract: This paper addresses the physicochemical characteristics of petroleum based diesel, coal based diesel and blended diesel (volume ratio of petroleum based diesel and coal based diesel 1:1), the power performance, fuel economy and exhaust emission with the three kinds of fuel were investigated on an engine test bench. The results show that: without any change in the diesel engine, when the engine fueled with coal based diesel power slightly upgraded, fuel consumption rate change little, exhaust smoke decrease obviously compared with using petroleum based diesel, that means coal based diesel is a kind of low-pollution alternative fuel for diesel engine.

Abstract: The following paper proposes a new system based on the direct transformation of a small-size jet engine thrust into torque. The paper determines the performance indices both of the design of the system transforming the jet thrust into rotary motion and the power generation.

Abstract: In this work, attention was paid to the understanding of the chemical modifications occurring in xerogeis of 58S bioglass (60% mol SiO₂; 36%mol CaO; 4%mol P₂O₅), during the 58S bioglass synthesis, prepared by the sol-gel (SG) and sol-gel self-propagating combustion (SGSPC) methods using citric acid as reductant/fuel. The chemical modifications of the xerogels were evaluated in the temperature range 70-920°C. Characteristic functional groups were evidenced by Fourier transform infrared spectroscopy (FTIR), and the thermal behaviour was evidenced by thermal gravimetric (TG) and differential thermal (DSC) analysis, the transition from glass to glass ceramic was also followed by X-ray diffraction.

Abstract: Diesel engine emission has been considered as major air pollution sources. Feedstocks blending method is motivated by cost reduction and property enhancement. In this paper crude rubber seed oil and palm oil are mixed in 50:50 vol. % and converted to biodiesel. Thermophysical property of the biodiesel was studied. Blends with varying contents of diesel and biodiesel 5-20 vol. % were prepared. Engine emissions and combustion characteristics were measured and analysed. The CO emission was reduced but the exhaust gas temperature and NOx emission increased proportional to the blends ratio. Premixed combustion phase in all tested blends start earlier the neat diesel .Short ignition delay and lower heat release rate were noticed.