It was my Diploma final year project and in this I tried to develop a working model of Turbojet engine. The purpose of developing this project is to develop an experimental test facility in which certain parameters like thrust, turbine inlet and exit temperatures and fuel flow rate etc. are determined including some combustion/emission analysis. My first and foremost objective in this project is to develop a combustor in which the combustion takes place and is able to drive the turbine wheel of turbocharger, for achieving this task first I theoretically determine the stoichiometric ratio of air-fuel mixture that is required for combustion and then based on that calculation we made the geometry of combustor on SolidWorks. Then with the help of computational package, visualization of flow dynamics inside the combustion chamber and determination of temperatures at different positions on combustor on ANSYS Fluent is done. After that I made a Combustor (shown in figure) from stainless steel pipe, it consist of two fuel injectors, air inlet entrance, an ignition switch. Based on my pre calculations I tested it but unfortunately we are not able to achieve proper combustion inside this chamber, the major problems I face in this entire project is the incomplete combustion, flame stability is not achieved and improper fuel/air mixing, at Diploma level I didn’t get much information about this work from my academic course. Beside these technical problems I also suffer with some non-technical problems related in funding and fabrication work.
I think that with this facility the experimental research involving the development of different type of thermal & fluid measurement sensors and systems within the institution will also take place which are either very costly or not available in the market such as heat flux measurement, flow-rate, turbine speed measurement, thrust measurement etc.
Nowadays most of the practical combustion system used in gas turbines employs a non-premixed combustion having a normal diffusion flame (NDF). However the presence of soot particles in NDF have undesirable effects on combustors and also on the human & environmental health. Recently, the interest in a special type of non-premixed flame known as Inverse Diffusion Flame (IDF) come into existence which produce much less amount of soot particles as compared to NDF. Besides that the lift-off phenomena which is very common in NDF doesn’t occur in IDF even at high speed. An IDF is formed when a high speed velocity of air jet surrounded by a low jet velocity is ignited in a backstep or coaxial burner [1-2].
Below is the picture of the proposed design of gas turbine burner. The burner body is made up of 10 gauge mild steel material. There are two concentric tubes one for entering high speed air and other for low speed fuel. The inner tube is placed at a distance below outer tube for enhance mixing. A movable swirler is provided in the path of fuel jet which create turbulence which further allow better air-fuel mixing. Tiny holes are provided in the inner tube so that a small partial premixing can be achieved in the mixture. A calibrated photo-optic tachometer will be mounted on the outer tube which can determine the actual speed of swirler. Arrangements for an optical glass window (Quartz material) will be made on the outer body of burner to investigate the flame characteristics with the help of PIV and LDV techniques.