1. Gas Turbine Engine – Turbojet

2. Uses for Gas Turbine Engines

3. Gas Turbine Ideal Thermodynamic Cycle
IDEAL SITUATION
Ideal
Brayton
Cycle P
Gas turbine engine again acts as a ‘heat engine’.
Heat added to gas through combustion is converted to useful work.
Work
Out
Work In V

4. Gas Turbine Thermodynamic Cycle
Inlet + Compressor P
Turbine + Nozzle
Work
Out
Work In
Combustor V

5. Types of Gas Turbine Engines
Axial
Centrifugal

6. Turbine
● Engine thermal efficiency is optimized by increasing the turbine inlet temperature, but there is a limit.
● Current turbine exhaust temperatures ~ 1350° C
● Special materials and active cooling used to prevent melting of blades.
TURBINE BLADES

8. Port Fuel Injected 4-Stroke
Overall Comparison
BSFC: Brake Specific Fuel Consumption (lb fuel / hour / hp)
TYPE
CATEGORY
BSFC
DIESEL
Industrial / 4-Stroke
Other 4-Stroke
2-Stroke
SI-ENGINE
Automotive
Port Fuel Injected 4-Stroke
Carbureted 4-Stroke
Automotive 2-Stroke
0.55 +
GAS TURBINE
Sample – Rolls Royce MT30
0.35

9. Thermal Efficiencies Better Efficiency at High Power Output? Thermal
50%
Gas Turbine
Diesel
25%
Otto, Rankine
% Full Power
50%
100%

10. Gas Turbine Performance
Advantages
Disadvantages
Large power-to-weight ratio (ideal for aircraft)
Small size (compared to diesel at same power output)
High RPM – advantage for power generation
Provides high speed exhaust – ideal for high- speed air travel.
Expensive
Difficult to design and maintain
Operates only at high RPMs – gas guzzler !!
Not good for rapid changes in load / speed

11. MiniLabTM Gas Turbine Power System (1)
Start Procedure

12. MiniLabTM Gas Turbine Power System (2)
Compressor Analysis – compressor pressure ratio, power required, rotational speed and compressor efficiency
Turbine Analysis – work and power developed, expansion ratio and turbine efficiency
Brayton Cycle Analysis – mass flow rate, inlet and exit velocity, station temperature and pressures, combustion and thermal efficiency, specific fuel consumption and power/thrust developed
Combustion Analysis – excess air and fuel-air ratio
General Analysis – diffuser and nozzle performance and efficiency

13. SR-30 – Compact Turbojet Engine
Single Stage
Centrifugal Flow Compressor
Reverse Flow Annular Combustor
Engine Diameter: 17 cm
Engine Length: 27 cm
Single Stage
Axial Flow Turbine

14. Engine Sensor Locations
Design Max. RPM:
87,000
Mass Flow:
0.5 kg/s
Design Max. Thrust:
178 N (40 lbf)

15. Control Panel and Data Acquisition
All data needed for the analysis assignments can be downloaded into an Excel file.
You must bring a thumbdrive to save your data to.

16. Brayton Cycle Analysis

17. Experimental and Requirements – Brayton Cycle
Thrust Specific Fuel Consumption (TSFC) Analysis:
Select at least four RPM settings (from low to highest operating RPM in the range of 40,000‒80,000 RPM) for your run.
Calculate Thrust Specific Fuel Consumption at each RPM setting.
Determine the power settings that offer the best and worst TSFC.
System Analysis:
For a chosen RPM, conduct Brayton cylce analysis.
Determine
the state of each cycle point
the specific work done by the compressor
the specific energy added by the fuel
the specific work of the turbine
the specific work done by the cycle
the thermodynamic efficiency of the cycle

18. Things to Study* Air-Standard Otto Cycle and Brayton Cycle
Work
Mean Effective Pressure and Back Work Ratio
Thermal Efficiency
Effect of Compression Ratio
Reacting Mixtures and Combustion
Complete Combustion
Stoichiometric Coefficients
Air-Fuel Ratio
Enthalpy of Formation
Enthalpy of Combustion
Higher and Lower Heating Values
Determination of Adiabatic Flame Temperature
*: M.J. Moran and H.N. Shapiro, Fundamentals of Engineering Thermodynamics, Chapters 9 &13.