Current Issue : April - June Volume : 2012 Issue Number : 2 Articles : 6 Articles
The objective of this work is to explore methods to reduce combustor rumble in a water-injected gas turbine. Attempts to\r\nuse water injection as a means to reduce NOX emissions in gas turbines have been largely unsuccessful because of increased\r\ncombustion instability levels. This pulsation causes chronic fretting, wear, and fatigue that damages combustor components. Of\r\ngreater concern is that liberated fragments could cause extensive damage to the turbine section. Combustion instability can be tied\r\nto the insufficient atomization of injected water; large water droplets evaporate non-uniformly that lead to energy absorption in\r\nchaotic pulses. Added pulsation is amplified by the combustion process and acoustic resonance. Effervescent atomization, where\r\ngas bubbles are injected, is beneficial by producing finely atomized droplets; the gas bubbles burst as they exit the nozzles creating\r\nadditional energy to disperse the liquid. A new concept for effervescent atomization dubbed ââ?¬Å?flash atomizationââ?¬Â is presented where\r\nwater is heated to just below its boiling point in the supply line so that some of it will flash to steam as it leaves the nozzle. An\r\nadvantage of flash atomization is that available heat energy can be used rather than mechanical energy to compress injection gas\r\nfor conventional effervescent atomization....
Wildland fire risk assessment and fuel management planning on federal lands in the US are complex problems that require stateof-\nthe-art fire behavior modeling and intensive geospatial analyses. Fuel management is a particularly complicated process where\nthe benefits and potential impacts of fuel treatments must be demonstrated in the context of land management goals and public\nexpectations. A number of fire behavior metrics, including fire spread, intensity, likelihood, and ecological risk must be analyzed\nfor multiple treatment alternatives. The effect of treatments on wildfire impacts must be considered at multiple scales. The process\nis complicated by the lack of data integration among fire behavior models, and weak linkages to geographic information systems,\ncorporate data, and desktop office software. This paper describes our efforts to build a streamlined fuel management planning\nand risk assessment framework, and an integrated system of tools for designing and testing fuel treatment programs on fire-prone\nwildlands....
This paper presents a method for numerical evaluation of parameters of flammable liquid pool fires caused by storage tank or\ntrunkline failures. The method may be useful for specialists working in oil, gas, and chemical industries. It was successfully applied\nin fire safety analysis of Russian gas and oil processing facilities....
Conventional compression ignition engines can easily be converted to a dual fuel mode of operation using natural gas as main fuel\nand diesel oil injection as pilot to initiate the combustion. At the same time, it is possible to increase the output power by increasing\nthe diesel oil percentage. A detailed performance and combustion characteristic analysis of a heavy duty diesel engine has been\nstudied in dual fuel mode of operation where natural gas is used as the main fuel and diesel oil as pilot. The influence of intake\npressure and temperature on knock occurrence and the effects of initial swirl ratio on heat release rate, temperature-pressure and\nemission levels have been investigated in this study. It is shown that an increase in the initial swirl ratio lengthens the delay period\nfor auto-ignition and extends the combustion period while it reduces NOx. There is an optimum value of the initial swirl ratio\nfor a certain mixture intake temperature and pressure conditions that can achieve high thermal efficiency and low NOx emissions\nwhile decreases the tendency to knock. Simultaneous increase of intake pressure and initial swirl ratio could be the solution to\npower loss and knock in dual fuel engine....
The effect of millisecond wide sub-breakdown pulsed voltage-current induced flow perturbation has been measured in premixed\nlaminar atmospheric pressure propane/air flame. The flame equivalence ratios were varied from 0.8 to 1.2 with the flow speeds\nnear 1.1meter/second. Spatio-temporal flame structure changes were observed through collection of CH (A-X) and OH (A-X)\nchemiluminescence and simultaneous spontaneous Raman scattering from N2. This optical collection scheme allows us to obtain a\nstrong correlation between the measured gas temperature and the chemiluminescence intensity, verifying that chemiluminescence\nimages provide accurate measurements of flame reaction zone structure modifications. The experimental results suggest that the\nflame perturbation is caused by ionic wind originating only from the radial positive space-charge distribution in/near the cathode\nfall. A net momentum transfer acts along the annular space discharge distribution in the reaction zone at or near the cathode fall\nwhich modifies the flow field near the cathodic burner head. This radially inward directed body force appears to enhance mixing\nsimilar to a swirl induced modification of the flame structure. The flame fluidic response exhibit a strong dependence on the\nvoltage pulse width =10 millisecond....
A high pressure EGR system was adopted to a turbocharged inter-cooled diesel engine, to analyze its combustion and emission\r\ncharacteristics under the condition of different loads and constant speed. Under the same steady operating mode, with the increase\r\nof EGR rate, the temperature of compressed gas ascended, the ignition delay was shortened, the pressure and temperature of the\r\nburned gas descended, and the combustion process was prolonged. According to the experimental data, it was found that, at the\r\nsame EGR rate, lower the load of engine was, lower the temperature in cylinder, and higher the increase rate of CO was. However,\r\nthe increase rate of HC present a falling trend. The decrease rate of the specific emission of NOx linearly varied with EGR rate with\r\na slope of 1.651. The increase rate of smoke opacity behaved a second-order polynomial uprising trend, and the higher the load\r\nwas, the sharpener the smoke opacity deteriorated, with the increase of EGR rate. Fromthe point of emission view, the engine with\r\nEGR system can achieve the lesser exhaust emissions in some operations by adjusting the engine parameters....
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