الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
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Abstract
Improving the efficiency of combustion systems is one of the main challenges in reducing the consumption of fuel. Advanced waste heat recovery, heat insulation enforcement and combustion enhancement technologies have been created. The increase in combustion air temperature, however, increases the flame temperature and the emissions of NOx significantly when using traditional burners. There are many techniques for reducing NO and CO emissions levels such as combustion with a highly preheated air and low-oxygen concentration. These technologies deliver important energy saving and uniform heat features within the combustion chamber, reducing pollution and equipment sizes.
The main objectives of the present study can be summarized in three parts: the first part is studying the effects of nitrogen percentages addition in air stream on the flame characteristics of liquefied petroleum gas (LPG) fuel when the combustion air temperature at 300 K. The parameter investigated is; the percentages of nitrogen addition in air stream of 0, 5, 7.5, 10 and 12.5 % to give low oxygen concentration by mass of 23.3, 18.3, 15.8, 13.3 and 10.8 %, respectively at constant air swirl number, air mixture (air + nitrogen added) to fuel mass ratio and thermal load of 1.5, 30 and 23 kW, respectively. In the second part, the effects of air temperatures on the flame characteristics for liquefied petroleum gas were studied with preheating the combustion air before entering the combustor by air preheating unit (APU). The effects of air temperature on the flame characteristics were examined. The main parameter is the air temperature of 300, 350, 400, 450, and 500 K at constant air swirl number, air mixture to fuel mass ratio, thermal load and percentage of nitrogen addition of 1.5, 30, 23 kW and 5 %, respectively. In the third part, the effects of gaseous fuel mixture (NG and LPG) on the flame characteristics were studied. The main parameter is the gaseous fuel mixture percentage of 0, 25, 50, 75, and 100 % of NG thermal heat percentage at constant air swirl number, air to fuel mass ratio, combustion air temperature and thermal load of 0.87, 40, 300 K and 46 kW, respectively.
To study the previous parameters, a test rig was constructed including a vertical water cooled test combustor, air line, nitrogen line and LPG and NG fuel lines. The effect of nitrogen percentages addition, preheated air temperature and gaseous fuel mixture percentages on the temperature pattern, visible flame length and the combustion species concentrations were studied. The results showed that, as the nitrogen percentages addition increases, the high temperature region is decreased to disappear at the nitrogen percentages addition of 12.5%, therefore, the flame length, NO, O2, CO2 and CO concentrations are decreased at the combustor end. When air preheated temperature increased, the high temperature region increased, the chemical reaction rates increased, enhancement combustion process leads to shorter flame and NO and O2 concentrations increased, but CO2 and CO concentrations decreased at the combustor end.
Increasing NG thermal heat percentages, the high temperature region, the flame length, NO, O2 and CO concentrations increased, while CO2 concentration decreased at the combustor end.