Tech talks

In the Trent 1000, there is 3 spool arrangement of compressors and turbines. This means that there are three sets of compressors and turbines which are connected by three separate shafts. They are the low pressure compressor (LPC) which is the fan and turbine (LPT), Intermediate pressure compressor (IPC) and turbine (IPT) and high pressure compressor (HPC) and turbine (HPT). This is on contrast to the two spool arrangement currently used in many aircrafts where a LPC/LPT and HPC/HPT are used only. All the three shafts are located within each other. The fan positioned at the front of the engine is run by the LPT via a gearbox so that it can operate at optimum speeds. Since the large diameter fan requires a large torque to start rotating, it limits the high speed attained by the LPT due to which its efficiency decreases. Additions of an additional set of compressor and turbine eliminates the influence of this problem but does not eliminate the problem itself! The problem is elim...

Rolls Royce are one of the leading manufacturers of turbofan engines apart from Pratt & Whitney, General Electric, CFM International and many more. One of their major milestones is the Trent 1000 which is designed and optimised to power the Boeing 787. It is the fifth member of the successful Trent family.   Let's understand certain facts about this turbofan engine before we dig deep into it's systems. It is a three shaft high bypass ratio axial flow British turbofan engine. Occupying a length of 473 cm and diameter of 285 cm, it is one of the most efficient engines discovered by man. It's fan consists of 20 blades made from Titanium alloys with small traces of Vanadium, Iron and Aluminium and is considered one of the lightest in the industry. Presence of chevrons at the rear of the engine helps reduce noise produced due to the temperature differences.      Below are some facts of it that will definitely blow your mind: During take off, tw...

There has been a wide range of materials used for the manufacturing of gas turbine blades. It is one of the most important parts in a gas turbine and any deterioration of it will affect the performance and efficiency of the turbine and most importantly will damage the turbine.  Many materials have been tested and used but the most preferred materials include steel, titanium, Nickel based super alloys and ceramics. The first stage of the compressor is very delicate as it is subjected to a very high temperature of approx. 1400-1500 degree celsius.  This part of the turbine should tolerate high temperatures, high pressures, high thermal stresses including creep and fatigue, vibrations which can influence it's performance. The first stage uses Udimet 500, Nickel based super alloy Inconel 738 or GTD 111.  The relatively cold stages of the turbine employ titanium as there are chances of it igniting when used above 500 degree celsius.      ...

The scope of gas turbines is not limited to aerodynamic uses but can also be extended for industrial purposes as well. These industrial gas turbines are designed such that they can be operated in varying climatic conditions ranging from the arctic cold to desert heat. SGT-A30RB Aeroderivative  The first class of industrial gas turbines are the aeroderivative turbines. As the name suggests, these are aircraft derived gas turbines. They include the same components as that of aircraft turbines with minor modifications so that they can include a wide range of liquid and gas fuels. They operate at an efficiency of 45% which indicates an increase of 15% compared to heavy duty gas turbines. They are light weight and utilize advanced materials for improved efficiency. They are multi shaft so that the mechanical components can operate at their optimal speed. SGT700 Industrial  The second class are the heavy duty gas turbines or frame turbines. They are heavy weight and ar...

After having understood the importance of gas turbines, they are used  for a wide range of airborne, land and marine applications. The airborne applications of gas turbines include the widely known turbojets, turbofans and turbo propellers. . The gas turbines used for land and marine applications are called mechanical drives. Before we begin to understand where they are used let's have a basic idea of them. All the three applications have the same structure as that of the gas turbine but differ only on the areas where they are used and addition of a single component. In a turbojet, the gases which are expanding through the nozzle after combustion is directly converted to thrust which is responsible for the motion of the aircraft.  In case of turbofans, the gases expand through the nozzle and a certain portion of it is converted to thrust while the remaining portion is used for the fan to accelerate the flow of air rearwards. Turbofan Turbofans produce less noise a...

In addition to the components of the gas turbine, there are accessory systems such as the starting system, ignition system, lubrication system and cooling system for proper functioning and maintenance of the system.  In order to start the assembly, a starter is used which can be a diesel engine or a generator that is directly coupled to the shaft of the compressor/turbine assembly.  The functions of the starter are three fold. The starter is to rotate the generator so that it reaches a self sustaining speed and to drive the compressor to purge the inlet and exhaust ducts for the escape of any volatile gases before the ignition occurs.  The starter is also used to rotate the gas generator after shutdown to facilitate cooling. For these purposes two starters are used.  One of them is a high speed starter which is used for rotating the generator and the other is used for purging and cooling purposes which is of low speed.  The gas generator can...