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This paper examines the effects of ambient temperature on the Trans-Amadi gas turbine power station Phase II. The investigation took thirteen (13) months (January 2012 to January 2013) during which plant data were monitored and operational Logsheets like turbine logsheets, plant—auxiliaries’ logsheets and generator logsheets were studied. The gas turbine (GT) that was under investigation was GT-2: MS5001 Nuovopignone with designed installed capacity of 25.0 Megawatts (MW). The result of the study shows that a 1 ℃ rise of the ambient temperature is responsible for the following: 0% - 0.12% decrease in the power output, 0% - 0.12% increase in the power differential, 0% - 1.17% decrease in the thermal efficiency, 0% - 27.18% increase in the heat rate and 0% - 3.57% increase in the specific fuel consumption. An ambient temperature of 30 ℃ is found to yield minimal fuel consumption.

The gas turbine in its most common form is a heat engine operating by means of series of processes consisting of compression of air taken from the atmosphere, increase of gas temperature by constant-pressure combustion of fuel in the air, expansion of hot gases and discharge of the gases to the atmosphere. It is thus similar to the spark ignition (S.I) and internal combustion (I.C) engines in working medium but is akin to the steam turbine in its aspect of the steady flow of the working medium [

The axial-thrust responses due to gas turbine rotor blade distortions have been studied [

The optimization performance analyses of a gas turbine plant were conducted [

The effect of compression ratio on the performance of combined cycle gas turbine was investigated [

The influence of Variation of Power Turbine Inlet Temperature on Overall Turbine Efficiency was studied [

The investigation of the effect of Evaporative Cooling on the Performance of a Gas Turbine Plant located in Bayelsa State, Nigeria has been done [

The Thermodynamic Performance Analysis of a Gas Turbine in an Equatorial Rain Forest Environment has been done [

The present study is on the effects of ambient temperature on the Performance of the Trans-Amadi Gas Turbine Power Station Phase II: (GT)-Unit II: MS5001 Nuovopignone Engine. The energy balance in the combustion chamber was utilized to compute the turbine inlet temperature and study the effect of the ambient temperature on the operating parameters like thermal efficiency, specific fuel consumption and heat rate.

The research methodology involved collection of data from actual plant operational logsheets: turbine logsheets, plant-auxiliaries logsheets and generator logsheets for the months of January 2012 to January 2013. Parameters which could not be directly measured or determined were derived utilizing appropriate thermodynamic equations and principles [

The primary parameters considered during the data collection are the pressures, temperatures and mass flow rates at various points in the gas turbine. However, in the evaluation and treatment of the data, statistical methods were used to calculate the mean values of daily parameters. This was done for every month that is under consideration and the average was taken at the end of each month. The actual performance of the power plant over the period of its installation was determined from their average parameters: inlet pressures, outlet pressures, inlet temperatures, mass flow rates, outlet temperatures and compressor works.

The Brayton (Joule) cycle is the thermodynamic cycle upon which this gas turbine operates and can be analysed using

By applying first law of thermodynamics for an open system, we have:

For the purpose of this analysis, the kinetic energy (v^{2}/2) and the gravitational potential energy (gz) are not significant factors and can be neglected.

The First Law becomes:

Mathematically, we have the following from

Heat Supplied or Heat Added:

The Heat Rejected or Heat Removed will be;

The Turbine Work is equal to:

The Net Power Output is the power generated by the generator and is given as:

Therefore, the energy balance in the combustion chamber is expressed as [

where: LHV = 47541.6 KJ/Kg [

After manipulating Equation (11); the fuel ratio ‘f’ is expressed as:

The Total Heat Supplied is expressed as [

Meanwhile, the Isentropic Efficiency of the Turbine will be:

Therefore, T_{4S} can be defined as:

P_{2} = P_{3} and P_{4} = P_{4}.

Turbine Pressure Ratio = P_{3}/P_{4} and the Compressor Pressure Ratio = P_{2}/P_{1}._{ }

The Compressor Work is calculated from the mass flow rate and enthalpy change across the compressor as follows:

Thermal Efficiency: The gas turbine efficiency is the percentage of the total fuel energy input that appears as the net work output of the cycle.

where: the network is the power output and is given by Equation (6).

Specific Fuel Consumption: The ratio of fuel used by a machine to a certain force such as the amount of power in the machine produced. And it can be determined by the equation:

Heat Rate: This is a measure used to determine how efficiently a generator uses heat energy. It can be expressed as:

Stoichiometric equation: This is the ideal combustion process in which minimum amount of air (Stoichiometric or theoretical air) is needed to completely burn a fuel.

Also the Specific Fuel Consumption can also be calculated with the following formula:

Therefore, Air Fuel Ratio:

The parameters in

Finally, the effects for every 1˚C rise in the ambient temperature with the power output, power differential, thermal efficiency ratio, specific fuel consumption and heat rate were determined and plotted using Excel Software as shown in Figures 2-6 respectively while

S/N | Parameters | Units | Design Data |
---|---|---|---|

1 | Power Output | MW | 25.0 |

2 | Thermal Efficiency | % | 26.6 |

3 | Heat Rate | Kcal/W∙h | 2.833 |

4 | Specific Fuel Consumption | Kg/KW∙h | 0.308 |

5 | Ambient Temperature | ˚C | 25.0 - 45.0 |

6 | Specific Heat at Constant Pressure of gas | KJ/KgK | 1.155 |

7 | Specific Heat at Constant Pressure of Air | KJ/KgK | 1.005 |

8 | Isentropic Constants for air | None | 1.40 |

9 | Isentropic Constants for gas | None | 1.33 |

10 | Mass Flow Rate of air | Kg/s | 122.9 |

S/N | T_{1}˚C Ambient Temperature | T_{2}˚C Compressor Exit Temperature | T_{3}˚C Turbine Inlet Temperature | T_{4}˚C Exhaust Temperature | ṁ_{f} (kg/s) Fuel Supply | Ẇ_{c} (KW) Compressor Work | Ẇ_{T} (KW) Turbine Work | Ẇ_{net } (KW) Net Work | AFR Air Fuel Ratio | h_{h}(%) Thermal Efficiency | SFC (kg/KWh) Specific Fuel Consumption | HR (KCal/W∙h) Heat Rate | (MW) Power Output | |
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|

1 | 25 | 240 | 1017 | 378 | 2.60 | 26,556 | 1670 | 98,002 | 24,886 | 0.485 | 25.39 | 0.298 | 3.94 | 11.14 |

2 | 26 | 242 | 1025 | 382 | 2.62 | 26,679 | 1693 | 98,774 | 24,986 | 0.481 | 25.30 | 0.300 | 3.95 | 11.14 |

3 | 27 | 244 | 1032 | 384 | 2.64 | 26,803 | 1719 | 99,420 | 25,084 | 0.478 | 25.23 | 0.300 | 3.96 | 11.13 |

4 | 28 | 246 | 1041 | 385 | 2.66 | 26,926 | 2015 | 100,319 | 24,911 | 0.474 | 24.83 | 0.305 | 4.03 | 11.13 |

5 | 29 | 247 | 1045 | 387 | 2.67 | 26,926 | 2029 | 100,706 | 24,897 | 0.472 | 24.72 | 0.306 | 4.05 | 11.13 |

6 | 30 | 248 | 1049 | 390 | 2.68 | 26,926 | 2040 | 101,093 | 24,886 | 0.470 | 24.62 | 0.308 | 4.06 | 11.13 |

7 | 31 | 250 | 1054 | 392 | 2.69 | 27,050 | 2054 | 101,479 | 24,996 | 0.470 | 24.60 | 0.308 | 4.06 | 11.12 |

8 | 32 | 254 | 1092 | 394 | 2.80 | 27,420 | 2257 | 105,863 | 25,163 | 0.449 | 23.77 | 0.319 | 4.20 | 11.11 |

9 | 33 | 257 | 1101 | 388 | 2.82 | 27,667 | 2322 | 106,638 | 25,345 | 0.445 | 23.77 | 0.319 | 4.20 | 11.10 |

10 | 34 | 258 | 1127 | 400 | 2.90 | 27,667 | 2435 | 109,867 | 25,232 | 0.432 | 22.97 | 0.330 | 4.35 | 11.09 |

11 | 35 | 260 | 1135 | 389 | 2.92 | 28,451 | 2516 | 110,643 | 25,935 | 0.430 | 23.44 | 0.322 | 4.27 | 11.08 |

12 | 36 | 262 | 1156 | 388 | 2.98 | 28,591 | 2643 | 113,099 | 25,948 | 0.420 | 22.94 | 0.330 | 4.36 | 11.07 |

13 | 37 | 265 | 1165 | 379 | 3.00 | 28,849 | 2724 | 113,877 | 26125 | 0.418 | 22.94 | 0.330 | 4.36 | 11.04 |

S/N | Ambient Temperature (˚C) | Percentage of Power Output (%) | Power Differential (%) | Percentage of Thermal Efficiency (h_{th}) (%) | Percentage of Specific Fuel Consumption (SFC) (%) | Percentage of Heat Rate(HR) (%) |
---|---|---|---|---|---|---|

1 | 25 | 44.56 | 55.44 | 95.45 | 96.75 | 139.08 |

2 | 26 | 44.56 | 55.44 | 95.11 | 97.40 | 111.90 |

3 | 27 | 44.52 | 55.48 | 94.85 | 97.40 | 139.78 |

4 | 28 | 44.52 | 55.48 | 93.35 | 99.03 | 142.25 |

5 | 29 | 44.52 | 55.48 | 92.93 | 99.35 | 142.96 |

6 | 30 | 44.52 | 55.48 | 92.56 | 100.00 | 142.31 |

7 | 31 | 44.48 | 55.52 | 92.48 | 100.00 | 142.31 |

8 | 32 | 44.44 | 55.56 | 89.36 | 103.57 | 148.25 |

9 | 33 | 44.40 | 55.60 | 89.36 | 103.57 | 148.25 |

10 | 34 | 44.36 | 55.64 | 86.35 | 107.14 | 153.55 |

11 | 35 | 44.32 | 55.68 | 88.12 | 104.54 | 150.72 |

12 | 36 | 44.28 | 55.72 | 86.24 | 107.44 | 153.90 |

13 | 37 | 44.16 | 55.84 | 86.24 | 107.44 | 153.90 |

that the power output decreases as the ambient temperature increases. It also shows that as the ambient temperature increases from 29˚C to 35˚C, the power output decreases from 44.52% to 44.33%. In real terms, the power output decreases from 4.96 MW to 4.91 MW.

Finally,

The result of the study shows that the ambient temperature has effect on the performance of the gas turbine and that a 1˚C rise of the ambient temperature is responsible for the following: 0% - 0.12% decrease in the power output, 0% - 0.12% increase in the power differential, 0% - 1.17% decrease in the thermal efficiency, 0% - 27.18% increase in the heat rate and 0% - 3.57% increase in the specific fuel consumption.

Igoma, E.N., Lebele-Alawa, B.T. and Sodiki, J. (2016) Evaluation of the Influence of Ambient Temperature on the Performance of the Trans-Amadi Gas Turbine Plant. Journal of Power and Energy Engineering, 4, 19-31. http://dx.doi.org/10.4236/jpee.2016.411002

AFR Air Fuel Ratio

C_{p} Specific Heat Capacity of the Product KJ/KgK

C_{pa }Specific Heat of Air at Constant Pressure KJ/KgK

C_{pg} Specific Heat of Gas at Constant Pressure KJ/KgK

CV Calorific Value of the Fuel

Ʃ Summation

F Fuel Ratio

g Acceleration due to Gravity g = 9.81 m/s^{2}

GT Gas Turbine

h Specific Enthalpy KJ/KgK

HR Heat Rate Kcal/KW∙h

LHV Lower Heat Value KJ/Kg

MW Meggawatts

ṁ Mass Flow Rate Kg/s

ṁ_{p} Mass Flow Rate of the Product Kg/s

ṁ_{a} Mass flow rate of air Kg/s

ṁ_{g} Mass flow rate of gas Kg/s

ṁ_{f} Mass flow rate of fuel Kg/s

ɳ_{th} Thermal Efficiency %

ɳ_{ts} Isentropic Efficiency of Turbine %

P Pressure bar

P_{atm} Atmospheric Pressure bar

P_{Diff}_{.} Power Differential MW

P_{Output} Power Output MW

P_{1} Compressor Inlet Pressure: Atmospheric Pressure bar

P_{2} Compressor Outlet Pressure bar

P_{3 }Turbine Inlet Pressure bar

P_{th} Thermal Energy MW

P_{4} Turbine Outlet Pressure bar

ρ_{a }Density of Air Kg/m^{3}

Q_{added} Heat Added or Heat Supplied KJ/Kg

s Specific Entropy KJ/KgK

SFC Specific Fuel Consumption Kg/KW∙h

T Temperature ˚C or K

T_{f} Temperature of Fuel ˚C

T_{1} Ambient Temperature ˚C

T_{2} Compressor Exit Temperature ˚C

T_{3} Turbine Inlet Temperature ˚C

T_{4} Exhaust Temperature ˚C

T_{4S} Exhaust Isentropic Temperature ˚C

v Velocity m/s

v_{a} Specific Volume of air aspirated by the compressor m^{3}/kg

Ẇ_{c} Compressor Work KJ/Kg

Ẇ_{Net} Turbine Net Work KJ/Kg

Ẇ_{SHAFT} Shaft Work Transfer KW or KJ/Kg

Ẇ_{T} Turbine Work KJ/Kg

ϒ Isentropic index

z Distance m

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