3-1 Copyright  2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Puffett, Hossack, Stone, Burn & Miles, Gasfitting 2e Chapter 3 PRINCIPLES AND PRODUCTS OF COMBUSTION

3-2 Copyright  2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Puffett, Hossack, Stone, Burn & Miles, Gasfitting 2e Principles of combustion Combustion is a chemical reaction that takes place at a high temperature and results in the oxidation of gas. For combustion to occur three ingredients are required. 1. Fuel (hydrocarbon) 2. Oxygen (normally taken from air, which consists of approx. 20% oxygen and 80% nitrogen) 3. Ignition (heat) Note: Nitrogen is an inert gas and does not burn.

Combustion process 3-3 Copyright  2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Puffett, Hossack, Stone, Burn & Miles, Gasfitting 2e

Products of complete combustion The combustion process results in: 1. heat (what is required) 2. water vapour (H 2 O) 3. carbon dioxide (C0 2 ) Note: Nitrogen passes through combustion unchanged. 3-4 Copyright  2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Puffett, Hossack, Stone, Burn & Miles, Gasfitting 2e

Causes of incomplete combustion Lack of air—insufficient air will not provide enough oxygen to complete combustion. Over-gassing—if a burner is over-gassed there is no guarantee sufficient air will be available for combustion. Blocked or inadequate flue—failure to remove combustion products will affect the combustion process. Impingement of the inner cone—a solid object in the inner cone of the flame will cool the fuel below ignition temperature. This will result in incomplete combustion. Incomplete combustion produces carbon monoxide, which is harmful! 3-5 Copyright  2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Puffett, Hossack, Stone, Burn & Miles, Gasfitting 2e

Important! Appliances and burners are designed and certified to ensure that, when fitted and adjusted correctly, complete combustion will take place. Correct installation and commissioning of the appliance will ensure the appliance performs safely and efficiently. 3-6 Copyright  2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Puffett, Hossack, Stone, Burn & Miles, Gasfitting 2e

Types of burners 1.Post-aerated Gas is supplied at the burner head with all the air for combustion coming from around the burner head. 2.Aerated Approximately half the air used is entrained into the burner and mixed with the gas prior to burning. The remainder of the air comes at the point of combustion at the burner head. 3-7 Copyright  2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Puffett, Hossack, Stone, Burn & Miles, Gasfitting 2e

Post-aerated burners 3-8 Copyright  2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Puffett, Hossack, Stone, Burn & Miles, Gasfitting 2e

Aerated burners 3-9 Copyright  2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Puffett, Hossack, Stone, Burn & Miles, Gasfitting 2e

Aeration adjustment 3-10 Copyright  2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Puffett, Hossack, Stone, Burn & Miles, Gasfitting 2e

Burner adjustment An aerated burner should be adjusted when burning the correct maximum amount of gas Copyright  2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Puffett, Hossack, Stone, Burn & Miles, Gasfitting 2e

Burner adjustments a. Correct flame b. Over-aerated c. Under-aerated 3-12 Copyright  2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Puffett, Hossack, Stone, Burn & Miles, Gasfitting 2e

Combustion—Summary For combustion to occur three ingredients are required. 1. Fuel (hydrocarbon) 2. Oxygen (normally taken from air) 3. Ignition (heat) The combustion process results in: 1. heat (what is required) 2. water vapour (H 2 O) 3. carbon dioxide (C0 2 ) Incomplete combustion results in: –carbon monoxide Burner types: post-aerated, aerated (bunsen), forced and induced draught Copyright  2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Puffett, Hossack, Stone, Burn & Miles, Gasfitting 2e