In: Mechanical Engineering

An adiabatic gas turbine uses air to produce work. Air expands adiabatically from 600 kPa and 287 C to 90 kPa and 67 C. Take specific heats at room temperature (300 K). a) Find the isentropic efficiency of the turbine. b) Find the work produced by the turbine for a mass flow rate of 2.5 kg/s. c) If the mass flow rate of air is again 2.5 kg/s, find the entropy generation under steady conditions

A gas turbine expands air adiabatically at 1000 kPa
and 550 ⁰C to 120 kPa and 130⁰C. Air enters the
turbine through a 0.25 m
2 opening with an aveage velocity of 45 m/s, and exhausts through a
1 m2
opening. Assume the air is ideal gas with constant specific heats.
Take the constant pressure specific
heat and gas constant of air as Cp= 1.05 kJ/(kg K) and R=0.287
kJ/(kg K), respectively. Determine;
(a) the mass flow rate of air...

Air enters the turbine of a gas turbine at 1400 kPa, 1400 K, and
expands to 100 kPa in two stages. Between the stages, the air is
reheated at a constant pressure of 350 kPa to 1400 K. The expansion
through each turbine stage is isentropic.
Determine:
(b) the heat transfer for the reheat process, in kJ/kg of air
flowing.
(c) the increase in net work as compared to a single stage of
expansion with no reheat.

Air is expanded isentropically in an adiabatic turbine, to
produce 135 kW of power. If the mass flow rate is 0.75 kg/s, and
the air at the exit is 500 K and 305 kPa, then what is the
temperature and pressure at the inlet of the turbine?
(a) The temperature is K.
(b) The pressure is kPa.
NOTE: Do NOT approximate the air as having a constant specific
heat.

Thermodynamics
Air at 3.5 MPa and 500°C is expanded in an adiabatic gas turbine
to 0.2 MPa. Assume that the process is reversible. Changes in KE
and PE may be neglected and the average temperature of the gases is
550 K.
(a) Create a schematic representation of the equipment. (b)
Represent the process on a T-s diagram. (c) Determine the
polytropic exponent. (d) Determine the change in entropy for this
expansion process

A quantity of air (γ = 1.40) expands adiabatically from an
initial pressure of 2 atm and volume of 2 L at temperature 20 ° C
to twice its original volume. Find:
a) The final pressure
b) The final temperature

3.19 A gas with adiabatic exponent γ is compressed adiabatically
from an initial state (Pi, Vi) to final state (Pf, Vf). (a) Show
that the work done in this process is
W=((ViPi)/y-1)*[(Vi/Vf)^(y-1) -1]
(b) Evaluate the result numerically for one mole of helium gas
initially
at P = 1.0 atm and T = 300 K compressed to half its initial
volume.
(c) Compute the work done in an isothermal compression from the
same
initial point to half the initial volume....

Why
does an ideal gas cool when it expands adiabatically and
reversibly?

Air enters the
compressor of a gas-turbine plant at ambient conditions of 100 kPa
and 25°C with a low velocity and exits at 1 MPa and 347°C with a
velocity of 90 m/s. The compressor is cooled at a rate of 1500
kJ/min, and the power input to the compressor is 235 kW. Determine
the mass flow rate of air through the compressor. The inlet and
exit enthalpies of air are 298.2 kJ/kg and 628.07 kJ/kg.
The mass flow rate...

Steam at 4 MPa and 350°C is expanded in an adiabatic turbine to
120 kPa. What is the isentropic efficiency of this turbine if the
steam is exhausted as a saturated vapor?

A gas turbine receives 10 kg/s of helium and expands it
polytropically (n = 1.8) from 1100K and 600 kPa to 100 kPa.
Determine the power produced, the entropy change of the helium
through the gas turbine (kW/K) and the entropy change of the
surroundings (kW/K).
answer: 28,221 kW, 10.53 kW/K (Engineering thermodynamics)

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