Hydraulic Machines Flashcards
7 cards from real BME practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Hydraulic Machines flashcards as text
The slip in a reciprocating pump is defined as:
Answer: Difference between theoretical and actual discharge expressed as a fraction of theoretical discharge
Slip = (Q_theoretical − Q_actual) / Q_theoretical, representing losses due to leakage and valve timing; negative slip is possible if inertia effects increase actual discharge.
A Kaplan turbine differs from a propeller turbine in that:
Answer: Its runner blades are adjustable, allowing efficient part-load operation
Kaplan turbines have adjustable (controllable-pitch) runner blades that, combined with adjustable guide vanes, maintain high efficiency over a wide range of flows and heads.
Manometric efficiency of a centrifugal pump is the ratio of:
Answer: Actual head developed to Euler's (theoretical) head
Manometric efficiency = H_m / H_Euler, reflecting hydraulic losses (friction, turbulence) between the ideal energy added by the impeller and the actual manometric head.
The purpose of a surge tank in a hydropower system is to:
Answer: Protect the penstock from water hammer during load changes
A surge tank provides a water surface close to the turbine that absorbs pressure transients when turbine load changes, protecting the penstock from water hammer.
In the Euler turbomachinery equation, the torque on the runner depends on:
Answer: Change in the whirl (tangential) component of absolute velocity
Euler's equation states T = ρQ(r₁V_w1 − r₂V_w2); only the whirl (tangential) velocity components contribute to angular momentum change and thus torque.
Which pump characteristic curve feature indicates a stall or unstable operating region?
Answer: A rising portion of the H-Q curve at low flow rates (drooping characteristic)
A rising (or humped) H-Q curve at low flows indicates potential instability because two different flow rates can produce the same head, leading to flow oscillation in parallel pump systems.
The volumetric efficiency of a pump accounts for:
Answer: Internal recirculation and leakage reducing useful discharge
Volumetric efficiency = Q_actual / Q_theoretical, capturing losses due to internal leakage past wearing rings and back through clearances rather than hydraulic or mechanical losses.