Basic Mechanical Engineering - BT203

BME Unit 5: Reciprocating Machines

Complete RGPV exam-oriented page covering steam engine, Carnot cycle, Otto cycle, Diesel cycle, Dual cycle, P-V and T-S diagrams, two stroke engines, four stroke engines and compressor.

Read Notes Important Questions PYQ Analysis

Unit 5 Syllabus

Reciprocating Machines important topics

Thermodynamic Cycles

  • Carnot cycle
  • Otto cycle
  • Diesel cycle
  • Dual cycle
  • P-V and T-S diagrams

Engines

  • Steam engine
  • Two stroke petrol engine
  • Four stroke petrol engine
  • Two stroke diesel engine
  • Four stroke diesel engine

Compressor

  • Working principle of compressor
  • Classification of compressors
  • Applications of compressors

Short Exam Notes

Easy points for fast revision

Reciprocating Machines

Reciprocating machines are machines in which piston moves back and forth inside a cylinder. They are used in engines, compressors and pumps.

Steam Engine

Steam engine converts heat energy of steam into mechanical energy. Steam pushes the piston and piston motion is converted into rotary motion by crankshaft.

Carnot Cycle

Carnot cycle is an ideal thermodynamic cycle having maximum possible efficiency. It consists of two isothermal and two adiabatic processes.

Otto Cycle

Otto cycle is the air standard cycle for petrol engines. Heat addition and heat rejection take place at constant volume.

Diesel Cycle

Diesel cycle is the air standard cycle for diesel engines. Heat addition takes place at constant pressure.

Dual Cycle

Dual cycle is the combination of Otto and Diesel cycles. Heat is supplied partly at constant volume and partly at constant pressure.

Four Stroke Engine

In four stroke engine, one power stroke is obtained in two revolutions of crankshaft. Strokes are suction, compression, power and exhaust.

Compressor

Compressor is a machine used to increase pressure of gas. It converts mechanical energy into pressure energy of gas.

Quick Revision Formulas

Important numerical formulas

Carnot Cycle Efficiency: η = 1 − (T₂ / T₁)
Otto Cycle Efficiency: η = 1 − 1 / rγ−1
Compression Ratio: r = V₁ / V₂
First Law of Thermodynamics: Q = ΔU + W

Most Important Questions

High chance RGPV exam questions

14 Marks Questions

  • Explain working principle of steam engine with neat diagram.
  • Explain Carnot cycle with P-V and T-S diagrams and efficiency derivation.
  • Explain Otto cycle with neat diagram and efficiency derivation.
  • Explain Diesel cycle with P-V and T-S diagrams.
  • Explain Dual cycle with applications.
  • Explain P-V and T-S diagrams of thermodynamic cycles.
  • Explain working of two stroke petrol engine with neat sketch.
  • Explain working of four stroke petrol engine with neat sketch.
  • Differentiate two stroke and four stroke engines.
  • Differentiate petrol and diesel engines.
  • Explain working principle of compressor with applications.

7 Marks Questions

  • Define reciprocating machines.
  • Explain Carnot cycle efficiency.
  • Explain Otto cycle applications.
  • Explain Diesel cycle applications.
  • Explain Dual cycle.
  • Explain compressor applications.
  • Explain P-V diagram.
  • Explain T-S diagram.
  • Explain compression ratio.

Important Numericals

  • Carnot cycle efficiency numerical problems
  • Otto cycle efficiency numerical
  • Diesel cycle numerical problems
  • Compression ratio calculations
  • Work done in thermodynamic cycles

PYQ Analysis Table

Repeated questions from previous RGPV papers

Topic Repeated Questions Frequency Priority
Carnot Cycle P-V and T-S diagrams, efficiency derivation and numerical Very High ★★★★★
Otto Cycle Neat diagram, efficiency derivation and applications Very High ★★★★★
Diesel Cycle P-V and T-S diagrams, applications and comparison with Otto cycle Very High ★★★★★
Two & Four Stroke Engines Working, neat sketch and difference High ★★★★
Compressor Working principle, classification and applications High ★★★★
Steam Engine Working principle and applications Medium ★★★
Dual Cycle Neat sketch and applications Medium ★★★
P-V and T-S Diagrams Draw and explain diagrams Medium ★★★

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FAQs

Common student doubts

Which topic is most important in BME Unit 5?

Carnot cycle, Otto cycle, Diesel cycle, two stroke and four stroke engines, and compressor are most important.

Which numericals should I practice?

Carnot efficiency, Otto efficiency, compression ratio and thermodynamic cycle work done numericals are important.

Which diagrams are important?

P-V diagram, T-S diagram, Carnot cycle, Otto cycle, Diesel cycle, two stroke engine and four stroke engine diagrams are important.

Related Units

Unit 1 Unit 2 Unit 3 Unit 4