Turbojet Engine

DESCRIPTION

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.

ACTUAL COMBUSTOR DESIGN

Proposed Design

Introduction

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].

Objective

1. To design and fabricate a gas turbine burner which uses IDF for operation.
2. To test the flame characteristics like temperature profiles, species concentration and stability using different types of fuel mixtures and at different fuel/air velocities (e.g. hydrogen + methane) with the help of optical techniques like PIV and LDV.
3. To investigate the flame structure with different swirlers numbers and also by rotating individual swirler.

Experimental Apparatus

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.

Methodology

• The high speed air/preheated air enters from the central tube and low speed fuel enters from the outer tube.
• The fuel jet passes through the swirler attached with with the central tube.
• There is a need to test the flame characteristics with static swirler and by rotating it which will achieved by fuel jet momentum. So with some special mechanical attachments the swirler can be made static, movable or replaceable with other.
• Pilot flame will be a better option to ignite the mixture.
• For rotating swirler case, the RPM will be determined by using a calibrated photo optic tachometer.

References

1. Han S. Kim, Vaibhav K. Arghode, Ashwani K. Gupta,"Combustion characteristics of a lean premixed LPG–air combustor", International Journal of Hydrogen Energy", Vol. 34, 2009, pg 1045.
2. Hydrogen addition effects in a confined swirl-stabilized methane-air flame, International Journal of Hydrogen Energy, Vol. 34, 2009, pg 1054.
3. S. Mahesh, D.P. Mishra, "Characterization of swirling CNG inverse jet flame in recessed coaxial burner", Fuel, Vol. 161, 2015, pg. 182-192.
4. S. Mahesh and D. P. Mishra, "Effects of recessed air jet on turbulent compressed natural gas inverse diffusion flame shape and luminosity", Combustion, Explosion, and Shock Waves, Vol. 48, No. 6, pp. 683–688, 2012 .
5. S. Mahesh, D.P. Mishra , "Flame structure of LPG-air Inverse Diffusion Flame in a backstep burner", Fuel 89 (2010) 2145–2148 .
6. D.P. Mishra and R. Kannan, "Experimental Investigation of Lean Premixed Swirl Burner", Int. J. Turbo and Jet Engines, 21, 103 - 113 (2004).