Introduction
In this homework, we will study the combustion process of the gas-turbine engine of our project. You may consult or work together with your team partners on this homework, but each student must perform their own calculations and submit their own work.
Nominal Performance*
Output Power, kWe: 4600
Heat Rate, kJ/kWe-hr (Btu/kWe-hr): 9351 (8863)
Exhaust Flow, kg/hr (Ib/hr): 63,700 (140,400)
Exhaust Temperature, C: 377 (F): 710
*ISO: 15C59F, sea level
No inlet or exhaust losses
Relative humidity: 60%
Natural gas fuel with LHV = 31.5 to 43.3 MJ/nm3 (800 to 1100 Btu/scf)
Fuel Input
Combustor
The nominal operation performance data provided by Solar Turbines for the Mercury 50 gas-turbine engine includes specifications:
Air inlet flow rate: 39.2 lbm/s
Power: 4600 kWe
Heat rate: 8863 Btu/kWe-hr
LHV of natural gas fuel: 800-1100 Btu/scf* (assume 1000 Btu/scf)
*scf = standard ft3, or volume of gas when T = 59 F, P = 14.7 psia
Problem #1:
Assume natural gas fuel to be an ideal gas mixture of 95% methane and 5% ethane (by volume). From the given information, determine:
a) specific volume of NG fuel at standard conditions,
b) mass flow rate of fuel at nominal operating conditions (ounces/sec),
c) AFR at nominal operating conditions,
d) write a balanced reaction equation assuming: dry air (O + 3.76N2), natural gas fuel with given composition and AFR, and complete combustion.
Problem #2:
Assume dry air enters the combustion chamber at 840 K and 950 kPa (state 4), and fuel enters at 298 K and 950 kPa. Determine the effective heat input/output to a non-adiabatic combustion chamber if the combustion products exit at (state 5) 950 kPa and temperature of:
a) 840 K,
b) 1500 K.
Problem #3:
Determine the exit temperature of the combustion products for an adiabatic combustion chamber (K).