Engineering reference for Indian students

Thermal & fluids

Fluid Machinery

5 self-contained study topics — notes, diagrams, formulas, and worked examples for exams and GATE.

Topics

Impact of Jets
A jet exerts force by momentum change: on a stationary flat plate F = ρaV², and on a moving plate F = ρa(V − u)². A curved vane deflecting the jet gives F = ρaV²(1 + cosθ), per Modi & Seth.
$Momentum equation: F = ṁ(V_{out} - V_{in})$
Pelton and Francis Turbines
Turbine work per unit mass follows Euler's equation W = u(V_w1 − V_w2)/g; the Pelton is an impulse machine for high heads and the Francis a reaction machine for medium heads. Bucket/runner speed u = πDN/60, per Modi & Seth.
$Degree of reaction R = \frac{(h_{1} - h_{2})}{(h_{1} - h_{3})} \approx 0.5 for Francis$
Centrifugal Pump
A centrifugal pump adds head via Euler's relation H_m = (V_w2·u₂ − V_w1·u₁)/g; overall efficiency η = ρgQH_m/P_shaft. Cavitation is avoided by keeping NPSH_available above NPSH_required, per Modi & Seth.
Reciprocating Pump
A reciprocating pump displaces Q = ALN (single-acting) or 2ALN (double-acting); slip = (Q_theoretical − Q_actual)/Q_theoretical. An air vessel smooths flow and reduces acceleration head, per Modi & Seth.
$Slip = \frac{(Q_{theoretical} - Q_{actual})}{Q_{theoretical}}$
Specific Speed and Similarity
Specific speed characterises a machine's type: N_s = N√Q/H^(3/4) for pumps and N√P/H^(5/4) for turbines. Geometrically similar machines share N_s and follow the affinity laws, per Modi & Seth.
$Cavitation parameter \sigma = \frac{H_{a}}{H}$