Soru
A ramjet engine operates at a flight Mach number M_(0)=0.8 at 9000 m altitude where p_(0)=30.14 kPa and T_(0)=229K For an effective exhaust velocity V_(e)=760m/s and inlet cross-sectional area A_(1)=0.187m^2 calculate; (a) the air mass flow rate m_(0) (b) the fuel mass flow rate my for a fuel-to-air ratio of ffa=0.03 (c) the exhaust gas mass flow rate me. (d) the gross thrust, (e) the net thrust, (f) the thrust power, (8) the propulsive efficiency n_(p) (h) the thermal efficiency 7_(th) (i) the specific fuel consumption q (i) the overall efficiency n_(o)
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Cevap
(a) The air mass flow rate
can be calculated using the formula:
where
is the air density at the inlet,
is the inlet cross-sectional area, and
is the inlet velocity.To find
, we can use the ideal gas law:
where
is the inlet pressure,
is the specific gas constant for air, and
is the inlet temperature.Substituting the given values, we get:
Now, we can calculate
:
(b) The fuel mass flow rate
can be calculated using the formula:
Substituting the given fuel-to-air ratio
and the calculated air mass flow rate
, we get:
(c) The exhaust gas mass flow rate
is the sum of the air and fuel mass flow rates:
(d) The gross thrust
can be calculated using the formula:
Substituting the given exhaust velocity
and the calculated inlet velocity
, we get:
(e) The net thrust
can be calculated using the formula:
Substituting the calculated values, we get:
(f) The thrust power
can be calculated using the formula:
Substituting the calculated values, we get:
(g) The propulsive efficiency
can be calculated using the formula:
Substituting the given exhaust velocity
and the calculated inlet velocity
, we get:
(h) The thermal efficiency
can be calculated using the formula:
Substituting the given exhaust velocity
and the calculated inlet velocity
, we get:
(i) The specific fuel consumption
can be calculated using the formula:
Substituting the calculated fuel mass flow rate
and the net thrust
, we get:$q = \