23-03-2012, 10:52 AM
AIRCRAFT GAS TURBINE ENGINES
AIRCRAFT GAS TURBINE ENGINES.docx (Size: 15.49 KB / Downloads: 69)
Introduction
Most of modern passenger and military aircraft are powered by gas turbine engines, which are also called jet engines. There are several types of jet engines, but all jet engines have some parts in common . Aircraft gas turbine engines can be classified according to (1) the type of compressor used and (2) power usage produces by the engine.
Compressor types are as follows:
1. Centrifugal flow
2. Axial flow
3. Centrifugal-Axial flow.
Power usage produced are as follows:
1. Turbojet engines
2. Turbofan engines.
3. Turboshaft engines.
Centrifugal Compressor Engines
Centrifugal flow engines are compress the air by accelerating air outward perpendicular to the longitudinal axis of the machine. Centrifugal compressor engines are divided into Single-Stage and Two-Stage compressor. The amount of thrust is limited because the maximum compression ratio.
Axial Flow Compressor Engines
Axial flow compressor engines may incorporate one , two , or three spools (Spool is defined as a group of compressor stages rotating at the same speed) . Two spool engine , the two rotors operate independently of one another. The turbine assembly for the low pressure compressor is the rear turbine unit . This set of turbines is connected to the forward , low pressure compressor by a shaft that passes through the hollow center of the high pressure compressor and turbine drive shaft.
Axial-Centrifugal Compressor Engine
Centrifugal compressor engine were used in many early jet engines , the efficiency level of single stage centrifugal compressor is relatively low . The multi-stage compressors are some what better , but still do not match with axial flow compressors. Some small modern turbo-prop and turbo-shaft engines achieve good results by using a combination axial flow and centrifugal compressor such as PT6 Pratt and Whitney of canada which very popular in the market today and T53 Lycoming engine.