Kaplan Turbine Test Rig Experiment: Procedure, Performance Curves, and Efficiency Calculations



What Is a Kaplan Turbine?

A Kaplan Turbine is an axial-flow reaction turbine with adjustable runner blades and adjustable guide vanes (wicket gates). It is designed for low-head, high-flow applications such as tidal barrages, run-of-river plants, and large canal headworks. The adjustable blades allow the turbine to operate efficiently across a wide range of flow rates and water heads — unlike Francis or Pelton turbines, which have fixed-point peak efficiency.

The Kaplan Turbine Test Rig manufactured by Scientico India is a laboratory-scale apparatus used by engineering colleges to study the performance characteristics, efficiency curves, and unit speed/power/discharge relationships of axial-flow turbines.

Kaplan Turbine vs Francis vs Pelton: Quick Comparison

Parameter	Kaplan Turbine	Francis Turbine	Pelton Turbine
Type	Axial-flow, reaction	Mixed-flow, reaction	Impulse
Head range	2–40 m (low head)	40–600 m (medium)	300–1800 m (high)
Flow	Very high	Medium–high	Low–medium
Runner blades	Adjustable	Fixed	Fixed (buckets)
Efficiency (peak)	90–95%	85–92%	88–92%
Applications	Tidal, run-of-river	Dams, reservoirs	Mountain streams, penstocks

Kaplan Turbine Test Rig Experiment: Objective

Determine the characteristic curves (performance curves) of a Kaplan turbine at constant head.

Plot unit speed (N_u), unit discharge (Q_u), and unit power (P_u) vs guide vane opening.

Determine the efficiency of the turbine at various operating points.

Find the runaway speed and shutoff head.

Theory: Performance Parameters of Kaplan Turbine

Unit Speed (N_u): N_u = N / √H
Unit Discharge (Q_u): Q_u = Q / (D² √H)
Unit Power (P_u): P_u = P / (D² H^(3/2))
Overall Efficiency (η): η = P_shaft / (ρgQH)
Where: N = speed (rpm), H = net head (m), Q = flow rate (m³/s), D = runner diameter (m), P = shaft power (W).

Kaplan Turbine Experiment Procedure

Apparatus Required

Kaplan Turbine Test Rig (Scientico, closed-loop, with sump tank and pump)

Differential pressure gauge / manometer for head measurement

Flow meter (electromagnetic or venture meter in supply pipe)

Tachometer (digital, non-contact)

Rope brake dynamometer or torque sensor for power measurement

Spring balance and weight pan (for rope brake)

Step-by-Step Procedure

Fill the sump tank. Prime the supply pump. Open all inlet valves.

Set guide vane opening to a fixed position (e.g., 50% open). Set runner blade pitch angle.

Start the supply pump. Allow flow to stabilise. Record inlet head H₁ and outlet head H₂ from pressure gauges.

Calculate net head: H = H₁ − H₂ + (V₁² − V₂²)/2g (velocity head correction).

Record flow rate Q from the flow meter.

Record turbine speed N (rpm) from the tachometer.

Apply rope brake load: add dead weights to the weight pan. Record spring balance reading S (N) and weight W (N). Torque T = (W − S) × R, where R = radius of brake drum + half of rope diameter.

Calculate shaft power: P = 2πNT/60 (W).

Calculate water power: P_w = ρgQH.

Calculate efficiency: η = P / P_w × 100%.

Repeat for different guide vane openings (25%, 50%, 75%, 100%) and different brake loads at each opening.

Observations Table

Guide Vane Opening (%)	Head H (m)	Flow Q (m³/s)	Speed N (rpm)	Torque T (Nm)	Shaft Power P (W)	Water Power P_w (W)	Efficiency η (%)
25%
50%
75%
100%

Graphs to Plot

η vs N (efficiency vs speed at constant head)

Q vs N (flow rate vs speed)

P vs N (power vs speed)

η vs P (efficiency vs power — the efficiency hill chart)

Unit speed N_u vs unit discharge Q_u (universal characteristic)

Result and Discussion

Report the maximum efficiency achieved and the operating point (N, Q, H) at which it occurs. Compare the peak efficiency with the theoretical design efficiency. Discuss the effect of guide vane opening on flow rate, speed, and efficiency. Explain the advantage of adjustable runner blades in maintaining efficiency at off-design flow conditions.

Viva Questions: Kaplan Turbine Experiment

What is the main advantage of adjustable runner blades in a Kaplan turbine?

How does a Kaplan turbine differ from a Francis turbine in flow direction?

What is unit speed and why is it used instead of actual speed for turbine characteristics?

Define runaway speed and explain its significance in turbine design.

What is draft tube and what is its function in a Kaplan turbine installation?

What is specific speed and how does it classify turbine types?

Why is Kaplan turbine preferred over Francis at very low heads?

Kaplan Turbine Test Rig Manufacturer India

Scientico India manufactures Kaplan Turbine Test Rigs for fluid mechanics and hydraulic machinery labs in engineering colleges. The closed-loop rig includes adjustable guide vanes, adjustable runner blade pitch, rope brake dynamometer, electromagnetic flow meter, digital tachometer, and complete manuals with observation tables. CE certified and ISO 9001:2015 manufactured. Exported to UAE, Saudi Arabia, Kenya, Bangladesh, Sri Lanka, Philippines, Vietnam, and Nepal. Request a CIF quotation.

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