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1. Draught and its classification
Presentation by:
Avdhesh Tyagi
Asst. Prof.
Department of Mechanical Engineering
G. L. Bajaj Institute of Technology & Management, Greater Noida
Disclaimer: The materials provided in this presentation and any comments or information
provided by the presenter are for educational purposes only. Nothing conveyed or provided
should be considered legal, accounting or tax advice.

2. Name of Subject: Applied Thermodynamics
Subject Code: KME401
Department of Mechanical Engineering
G. L. Bajaj Institute of Technology and Management,
Greater Noida, Uttar Pradesh
College code: 192
Affiliated to Dr. A.P.J. Abdul Kalam Technical University (Formerly UPTU Lucknow).
Unit 3
Topic covered: Draught and its classification

3. • Small pressure difference created for the flow of
gases inside the boiler.
• Required for expulsion of combustion products
and supply of fresh air inside furnace for
continuous combustion.
• Obnoxious gases formed during combustion
should be discharged at such height these gases
are not objectionable.
• A chimney or stack is generally used for creating
draught.
BOILER DRAUGHT

4. CLASSIFICATION OF DRAUGHT

5. • It is produced by a chimney.
• Hot gases inside the chimney are lighter
than the cold atmospheric air due to their
density difference.
• Thus in a boiler unit, the combustion
products (hot) rise from fuel bed through
chimney, and are replaced by fresh air
(cold) entering the grate.
NATURAL DRAUGHT

6. Natural draught created by using a
chimney

7. • Produced either by mechanical means such
as fans, blowers etc. or by using steam jet
for producing draught.
• These systems do not require tall
chimney/stack, but small stack is always
required for discharge of flue gases to
certain height in atmosphere for
minimizing pollution.
• Artificial draught can be classified as,
(i) Mechanical draught
(ii) Steam jet draught
ARTIFICIAL DRAUGHT

8. It is produced by using fans, blowers etc. It
could be of following type:
i. Forced draught
ii. Induced draught
iii. Combination of above two types i. e.
Balanced draught
MECHANICAL DRAUGHT

9. FORCED DRAUGHT
Image courtesy: Applied Thermodynamics by Onkar Singh, Third edition, New Age
International (P) Limited Publishers

10. INDUCED DRAUGHT
Image courtesy: Applied Thermodynamics by Onkar Singh, Third edition, New Age
International (P) Limited Publishers

11. BALANCED DRAUGHT
Image courtesy: Applied Thermodynamics by Onkar Singh, Third edition, New Age
International (P) Limited Publishers

12. STEAM JET DRAUGHT
Image courtesy: Applied Thermodynamics by Onkar Singh, Third edition, New Age
International (P) Limited Publishers

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