Pembakaran

Dari Wikipedia bahasa Melayu

Pembakaran adalah satu is a proses kimia, satu tindakbalas eksotermik di antara satu bahan (bahanapi) dan satu gas ( pengoksidan), biasanya O₂, untuk membebaskan haba. Dalam satu tindakbalas pembakaran yang sempurna, satu sebatian akan bertindakbalas dengan satu unsur yang beroksigen, dan hasilnya adalah sebatian dari setiap unsur bergabung di dalam bahanapi dengan unsur yang beroksigen. Sbagai contoh:

CH₄ + 2 O₂ → CO₂ + 2 H₂O + haba

CH₂S + 6 F₂ → CF₄ + 2 HF + SF₆ + haba

Jadual isi kandungan 1 Jenis Pembakaran 1.1 Pembakaran Marak/Cepat 1.2 Pembakaran Perlahan 1.3 Pembakaran Sempurna 1.4 Pembakaran Turbulasi 1.5 Pembakaran Tidak Sempurna 1.6 Pembakaran Pendam 2 Persamaan Kimia 3 Pembakaran Bahanapi Cecair 4 Pembakaran Bahanapi Pepejal 5 Suhu Pembakaran 6 Analisis Pembakaran 7 Pautan Luar 8 Lihat Juga

[Sunting] Jenis Pembakaran

Terdapat beberapa jenis pembakaran: -

[Sunting] Pembakaran Marak/Cepat

Pembakaran Marak/Cepat adalah merupakan satu bentuk pembakaran yang mana banyak tenaga haba dan cahaya dibebaskan. Pembakaran sebegini biasanya wujud sebagai api. Biasanya pembakaran ini digunakan dalam bentuk mekanisme, seperti enjin pembakaran dalaman, dan dalam senjata termobarik.

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Rencana ini diterjemahkan daripada sebahagian rencana Wikipedia bahasa Inggeris. Bantulah Wikipedia menterjemahkan lagi seperenggan dua. Bahan-bahan boleh didapati di en:Pembakaran.   Terima kasih kerana membaca rencana ini.  Sumber bantuan: Kamus Dewan Bahasa

[Sunting] Pembakaran Perlahan

Pembakaran perlahan adalah satu bentuk pembakaran yang berlaku pada suhu rendah. Respirasi adalah satu contoh pembakaran perlahan.

[Sunting] Pembakaran Sempurna

In complete combustion, the reactant will burn in oxygen, producing a limited number of products. When a hydrocarbon burns in oxygen, the reaction will only yield carbon dioxide and water. When elements such as carbon, nitrogen, sulfur, and iron are burned, they will yield the most common oxides. Carbon will yield carbon dioxide. Nitrogen will yield nitrogen dioxide. Sulfur will yield sulfur dioxide. Iron will yield iron(III) oxide. Complete combustion is generally impossible to achieve unless the reaction occurs where conditions are carefully controlled (e.g. in a lab environment).

[Sunting] Pembakaran Turbulasi

Turbulent combustion is a combustion characterized by turbulent flows. It is the most used for industrial application (e.g. gas turbines, diesel engines, etc.) because the turbulence helps the mixing process between the fuel and oxidizer.

[Sunting] Pembakaran Tidak Sempurna

In incomplete combustion there is an inadequate supply of oxygen for the combustion to occur completely. The reactant will burn in oxygen, but will produce numerous products. When a hydrocarbon burns in oxygen, the reaction will yield carbon dioxide, water, carbon monoxide, and various other compounds such as nitrogen oxides. Incomplete combustion is much more common and will produce large amounts of byproducts, and in the case of burning fuel in automobiles, these byproducts can be quite lethal and damaging to the environment.

[Sunting] Pembakaran Pendam

Smouldering combustion is a flameless form of combustion, deriving its heat from heterogeneous reactions occurring on the surface of a solid fuel when heated in an oxidizing environment. The fundamental difference between smouldering and flaming combustion is that in smouldering, the oxidation of the reactant species occurs on the surface of the solid rather than in the gas phase. The characteristic temperature and heat released during smouldering are low compared to those in the flaming combustion of a solid. Typical values in smouldering are around 600 °C for the peak temperature and 5 kJ/g-O2 for the heat released; typical values during flaming are around 1500 °C and 13 kJ/g-O2 respectively. These characteristics make smolder to propagate at low velocities, typically around 0.1 mm/s, which is about two orders of magnitude lower than the velocity of flame spread over a solid. In spite of its weak-combustion characteristics, smouldering is a significant fire hazard.

[Sunting] Persamaan Kimia

Secara umumnya, persamaan kimia untuk pembakaran sempurna hidrokarbon (contohnyaoktana) dalam oksigen adalah seperti berikut:

C_xH_y + (x + y/4)O₂ → xCO₂ + (y/2)H₂O

Contoh pembakaran propana adalah:

C₃H₈ + 5O₂ → 3CO₂ + 4H₂O

The simple word equation for the combustion of a hydrocarbon is:

Fuel + Oxygen → Heat + Water + Carbon dioxide.

[Sunting] Pembakaran Bahanapi Cecair

Combustion of a liquid fuel in an oxidizing atmosphere actually happens in the gas phase, i. e. it is the vapour that burns, not the liquid. Therfore, a liquid will normally catch fire only above a certain temperature, its flash point. Below that temperature the liquid will not evaporate fast enough to sustain the fire.

[Sunting] Pembakaran Bahanapi Pepejal

The act of combustion consists of three relatively distinct but overlapping phases:

• Preheating phase, when the unburned fuel is heated up to its flash point and then fire point. Flammable gases start being evolved in a process similar to dry distillation.
• Distillation phase or gaseous phase, when the mix of evolved flammable gases with oxygen is ignited. Energy is produced in the form of heat and light, flame is often visible.
• Charcoal phase or solid phase, when the output of flammable gases from the material is too low for persistent presence of flame and the charred fuel does not burn rapidly anymore but just glows and later only smoulders.

[Sunting] Suhu Pembakaran

Assuming perfect combustion conditions, such as an adiabatic (no heat loss) and complete combustion, the adiabatic combustion temperature can be determined. The formula that yields this temperature is based on the first law of thermodynamics and takes note of the fact that the heat of combustion (calculated from the fuel's heating value) is used entirely for warming up fuel and gas (e.g. oxygen or air).

In the case of fossil fuels burnt in air, the combustion temperature depends on

• the heating value
• the stoichiometric air ratio λ
• the heat capacity of fuel and air
• air and fuel inlet temperatures

The adiabatic combustion temperature increases for higher heating values and inlet temperatures and stoiciometric ratios towards one.

Typically, the adiabatic combustion temperatures for coals are around 1500 °C (for inlet temperatures of room temperatures and λ = 1.0), around 2000 °C for oil and 2200 °C for natural gas.

[Sunting] Analisis Pembakaran

Combustion analysis is a process used to determine the composition of organic compounds.

[Sunting] Pautan Luar

• Hydrocarbon combustion Simple applet that illustrates the Chemical equation.
• Fuel efficiency (stoichiometric air fuel mixture) vs. decreased emissions in combustion engines

[Sunting] Lihat Juga

• Carbon dioxide
• Deflagration
• Detonation
• Fire
• Flue gas emissions from fossil fuel combustion
• Heat of combustion
• Phlogiston theory (historical)
• Pyrolysis
• Pyrophoric
• Smouldering
• Spontaneous combustion
• Stoichiometry
• Machines
  • Cyclone furnace
  • External combustion engine
  • Internal combustion engine
  • Rotary combustion engine
  • Staged combustion cycle (rocket)
• Measurement techniques
  • Calorimeter
  • Coherent anti-Stokes Raman spectroscopy (CARS)
  • Laser Doppler velocimetry
  • Laser-induced fluorescence
  • Particle image velocimetry
• Social applications and issues
  • Cooking
  • Global warming
  • Immolation