Lecture 7 Fuels and Engine
Fuels
Fuels are different materials used to produce large amount of energy. The energy produced by the combustion of one kg of fuel is known as its calorific value. Fuels are of three types.
- Solid- wood, coal, peat, dung, coke, charcoal
- Liquid- petroleum, diesel, gasoline, kerosene, LPG, coal tar, naphtha, ethanol
- Gaseous- natural gas, hydrogen, propane, methane, coal gas, water gas, blast furnace gas, coke oven gas, CNG
Fossil Fuel- Formed from the fossilized remains of ancient plants and animals under high pressure and temperature. Fossil fuels contain high percentages of carbon and include coal, petroleum, and natural gas.
Types of Reservoir
Conventional Reservoir- Oil and gas stored in permeable rocks referred to as conventional reservoirs.
Unconventional Reservoir- Oil and gas stored in tightly bound and less permeable rocks referred to as unconventional reservoirs.
Gas fuels
- Natural Gas(CH4)- Generally found along with coal or petroleum reserve.
- Shale Gas- Unconventional natural gas
- Syngas/Synthesis Gas(CO + H2)- Produced by partial oxidation of natural gas
- Hydrogen Gas(H2, click here for detail)
Engine Knocking- Undesirable sound and phenomenon that occurs when the air-fuel mixture in the combustion chamber ignites prematurely or unevenly. For petrol fuel octane number denotes anti knocking ability. Petrol with higher octane number will have low knocking. For diesel fuel cetane number denotes anti knocking ability. Diesel with lower cetane number will have low knocking.
Nuclear Fuel- Any material that can produce nuclear energy by nuclear fission(splitting nuclei apart) or fusion(combining nuclei together) process.
For more details on nuclear energy(click here)
Biofuels
Biomass- Matter from recently dead organisms which is used for bioenergy production. Biomass is mainly in solid form.
Biofuels- Liquid or gaseous fuel produced from biomass such as plant or agricultural/domestic/industrial biowaste. Biofuels are regarded as a renewable energy source.
Generation of biofuels-
- 1st Generation(Conventional Biofuels)- Biofuels derived from food items
- 2nd Generation(Advanced Biofuels)- Biofuels derived from non food items(waste vegetables, jatropha)
- 3rd Generation- Biofuels derived from Algae
- 4th Generation- Biofuels derived from genetic engineering
Transesterification- lipid to biofuel generation(in 2nd and 3rd generation Biofuels)
2018 biofuel policy- 20% Ethanol blending with petrol, 5% biodiesel blending with diesel by year 2030
Global Biofuel Alliance(GBA)- Launched by India in 2023 during G20 summit to promote the use of eco friendly biofuel around the world.
First 2G Ethanol Project- Panipat, Haryana (2022)
Cryogenic Fuels- Extremely low temperatures is required to maintain the fuel in the liquid state. Cryogenic fuels are mainly used in space sector(space/satellite rocket).
Liquid H2 + Liquid O2 → Cryogenic fuel used by ISRO
Cryogenic fuels are environmentally cleaner than gasoline and fossil fuels. It has lower carbon footprint.
Sonic Engine
Speed of sound= 1 Mach(343 metre per second)
- Subsonic- Speed < 1 Mach
- Supersonic- 1 Mach < Speed < 5 Mach
- Hypersonic- Speed > 5 Mach
Air Breathing Propulsion System- use of atmospheric oxygen to burn the fuel thus making the system much lighter, more efficient and cost effective.
Turbojet- Jet engine that uses a turbine to drive an air compressor and operates near sonic speed(1 Mach) .
Ramjet- Air breathing jet engine that uses the vehicle's forward motion to compress incoming air for combustion without an axial compressor. Ramjet works best at supersonic speeds.
Scramjet- Improved version of the ramjet engine that operates at hypersonic speeds and allows supersonic combustion.
Dual Mode Ramjet(DMRJ)- Mix of ramjet and scramjet. Upto 5 Mach engine work as ramjet and above 5 Mach spped engine work as a scramjet engine.
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