Turbines in Hydraulics: Pelton, Francis & Kaplan – Complete ECET 2026 Civil Guide

Concept Notes (Deep Explanation + Examples)

🌊 Introduction

In Hydraulics, turbines are devices that convert the energy of flowing water into mechanical energy, which is further converted into electrical energy by a generator.
They are the heart of hydroelectric power plants — a vital topic in ECET Civil Engineering.

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⚙️ Classification of Turbines

Turbines are broadly classified based on:

1. Type of Energy at Inlet
   • Impulse Turbines: Water hits the blades with kinetic energy only (e.g., Pelton Wheel).
   • Reaction Turbines: Water possesses both pressure and kinetic energy (e.g., Francis and Kaplan).
2. Direction of Flow through Runner
   • Tangential → Pelton Wheel
   • Radial → Francis Turbine
   • Axial → Kaplan Turbine
3. Head of Water
   • High Head → Pelton
   • Medium Head → Francis
   • Low Head → Kaplan

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⚡ 1. Pelton Turbine (Impulse Type)

• Working Principle: Converts kinetic energy of high-velocity water jets into mechanical energy.
• Construction:
  • Nozzles direct water jets onto double-cupped buckets mounted on the runner.
  • Each bucket splits the jet into two to balance the force.
• Head: 300 m – 1800 m (High Head)
• Speed: Low (300–500 rpm)
• Efficiency: Around 85–90%
• Example: Power plants in hilly regions like Himachal Pradesh or Sikkim.
• Field Insight: At sites with steep gradients, Pelton turbines are ideal due to high potential energy of falling water.

Diagram (Explained in Words):
Imagine a wheel with spoon-shaped cups arranged along its rim. Water jets hit these cups tangentially, spinning the wheel.

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⚙️ 2. Francis Turbine (Reaction Type)

• Working Principle: Utilizes both pressure and kinetic energy of water.
• Construction:
  • Water enters radially inward and exits axially.
  • It has a spiral casing, guide vanes, runner, and draft tube.
• Head: 30 m – 300 m (Medium Head)
• Speed: Medium (600–1000 rpm)
• Efficiency: 90%
• Example: Common in medium-head dams like Nagarjuna Sagar.
• Field Example: When water from a reservoir flows through penstocks and enters the runner through adjustable guide vanes to control flow rate.

Diagram (Explained in Words):
Picture a circular turbine with curved blades. Water enters from the sides and exits downwards through the center.

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⚙️ 3. Kaplan Turbine (Axial Flow Reaction Type)

• Working Principle: Water flows axially (parallel to shaft) and imparts reaction force on blades.
• Construction:
  • Similar to a propeller but with adjustable blades.
  • Fitted with movable guide vanes for efficiency at varying loads.
• Head: 2 m – 40 m (Low Head)
• Speed: High (1000–3000 rpm)
• Efficiency: Up to 92%
• Example: Used in low-head plants like river-based hydro systems.
• Field Insight: Works efficiently where large volumes of water are available with small head differences.

Diagram (Explained in Words):
Imagine a boat propeller inside a tube where water flows through the blades causing them to rotate.

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⚖️ Comparison Table

Parameter	Pelton	Francis	Kaplan
Type	Impulse	Reaction	Reaction
Head	High	Medium	Low
Flow Direction	Tangential	Radial → Axial	Axial
Speed	Low	Medium	High
Efficiency	85–90%	90%	92%
Example Site	Tehri	Nagarjuna Sagar	Srisailam Low Head

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💡 ECET Important Points

• Pelton → High Head → Impulse
• Francis → Medium Head → Reaction
• Kaplan → Low Head → Axial Flow
• Draft Tube is used in reaction turbines to recover kinetic energy.
• Specific Speed (Ns): Decides the type of turbine used.

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3️⃣ ⚙️ Formulas (Plain LaTeX Only — No Boxes)

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4️⃣ 🔟 10 MCQs (GATE + ECET Mix)

1. Pelton wheel turbine works under ______ head.
   A) Low
   B) Medium
   C) High
   D) Very Low
2. The type of flow in a Francis turbine is:
   A) Tangential
   B) Radial
   C) Axial
   D) Radial → Axial
3. Kaplan turbine is suitable for:
   A) High Head, Low Discharge
   B) Medium Head, Medium Discharge
   C) Low Head, High Discharge
   D) High Head, High Discharge
4. Pelton turbine is a ______ turbine.
   A) Reaction
   B) Axial
   C) Impulse
   D) Mixed Flow
5. In Francis turbine, water flows:
   A) Axially
   B) Radially outward
   C) Radially inward to axially outward
   D) Tangentially
6. Efficiency of Kaplan turbine is approximately:
   A) 70%
   B) 80%
   C) 92%
   D) 50%
7. The function of the draft tube in reaction turbines is to:
   A) Increase pressure head
   B) Reduce pressure head
   C) Recover kinetic energy
   D) Maintain velocity
8. Specific speed of a turbine helps in:
   A) Determining head only
   B) Determining type of turbine
   C) Measuring discharge
   D) Measuring flow velocity
9. Pelton wheel buckets are:
   A) Flat plates
   B) Curved single cups
   C) Double hemispherical cups
   D) Propeller type
10. Francis turbine is ______ type of turbine.
    A) Axial Flow
    B) Radial Flow
    C) Mixed Flow
    D) Tangential Flow

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5️⃣ ✅ Answer Key (WordPress Table Format — NO HTML)

Q.No Answer
1 C
2 D
3 C
4 C
5 C
6 C
7 C
8 B
9 C
10 C

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6️⃣ 🧠 Explanations (Step-by-Step)

1. Pelton Wheel → High Head
   It operates with high potential energy, hence correct: C.
2. Francis Flow → Radial to Axial
   Entry is radial, exit is axial. Hence D.
3. Kaplan → Low Head, High Discharge
   Designed for river-type low head flows. Hence C.
4. Pelton = Impulse Turbine
   Uses only kinetic energy. Hence C.
5. Francis Flow Path: Radially inward → axially outward. Hence C.
6. Kaplan Efficiency: Very high, ~92%. Hence C.
7. Draft Tube → Kinetic Energy Recovery Device. Hence C.
8. Specific Speed: Used to decide turbine type (Pelton, Francis, Kaplan). Hence B.
9. Pelton Buckets: Double hemispherical cups split the jet into two halves. Hence C.
10. Francis Turbine = Mixed Flow Type. Hence C.

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7️⃣ 🎯 Motivation / Why Practice Matters (ECET 2026 Civil)

Turbines are one of the most repeated questions in ECET Civil — from head types to flow direction and specific speed.
Mastering this topic strengthens your Hydraulics base and boosts accuracy in 2–3 marks questions.
When your concepts are clear, even the toughest numerical feels simple.
Keep practicing — consistency is your best strategy for a top ECET 2026 rank! 🚀

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8️⃣ 📲 CTA

Join our ECET 2026 Civil WhatsApp Group for daily quizzes & study notes:
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