How much coal is required for a steam locomotive developing a power of 1470 kW
How much coal is required for a steam locomotive developing a power of 1470 kW at efficiency? 7.5% to cover 1000 km at an average speed of 54 km / h?
N = 1470 kW = 1.47 * 10 ^ 6 W.
S = 1000 km = 10 ^ 6 m.
V = 54 km / h = 15 m / s.
Efficiency = 7.5%.
λ = 2.7 * 10 ^ 7 J / kg.
m -?
When coal is burned, the amount of heat Q is released from it, which we express by the formula: Q = λ * m.
Only 7.5% of this amount of heat is converted into useful work by Apol.
Q * efficiency / 100% = Apol.
Find useful work Apol by the formula: Apol = F * S, where F is the traction force of the train, S is the movement of the train.
We express the power N by the formula: N = F * V.
F = N / V.
Apol = N * S / V.
λ * m * efficiency / 100% = N * S / V.
m = N * S * 100% / V * λ * efficiency.
m = 1.47 * 10 ^ 6 W * 10 ^ 6 m * 100% / 15 m / s * 2.7 * 10 ^ 7 J / kg * 7.5% = 48390 kg.
Answer: for the train to move, it is necessary to burn coal m = 48390 kg.