4. petrol engines
TRANSCRIPT
Design for Manufacture
4. Petrol Engines
Design for Manufacture
Design for Manufacture
Design for Manufacture
Design for Manufacture
Briggs & Stratton Engine
Design for Manufacture
Petrol Engines for Lawnmowers Quantum
Design for Manufacture
Design for Manufacture
Design for Manufacture
Design for Manufacture
Otto cycley
An 'Otto cycle' is an idealized thermodynamic cycle, describing the f i i f i l k i i i i i i ifunctioning of a typical spark ignition reciprocating piston engine
1-2 isentropic compression2-3 constant-volume heat transfer3 4 isentropic e pansion (po er stroke)3-4 isentropic expansion (power stroke)4-1 a constant-volume process (heat rejected)
Design for Manufacture
Design for Manufacture
Design for Manufacture
Idealised indicator diagram for 4-stroke engine
Design for Manufacture
Design for Manufacture
Stylised indicator diagram for 4-stroke engine
Engine Thermal Efficiency
Design for Manufacture
Energy Balance for per 1 kW power output
Heat Measurement Temperature t (Celsius) = T-273.15 (Kelvin) Q – heat energy joules/kgQ gy j g Specific heat capacity: heat transfer per unit temperature. Unit: joules/kg K (Joules per kg per degree)Unit: joules/kg K (Joules per kg per degree) Water: 4180 J/kg ·K Ice (-10ºC): 211 J/kg ·K S (100ºC) 208 J/k KSteam (100ºC): 208 J/kg ·K Air(room condition): 1012 J/kg ·K Copper: 385 J/kg ·K Calorific value of fuel The heat liberated by burning unit mass or volume of a fuel.
t l 43MJ/ke.g. petrol: 43MJ/kg Heat Unit Calorie 1 calorie = 4.18 joules (The heat to raise 1 degree for 1 gram water)j ( g g )
Fuel Consumption
Single cylinder 4 stroke petrol engine thermal efficiency 20-25%. Example: A 3 KW petrol engine has a thermal efficiency 20.5%. Find fuel consumption per hour. 3KW·hr= 3000J/s ×3600s=10,800,000J=10.8MJ Petrol heat energy is 43MJ/kggy g The fuel consumption:
kg23.1205.0438.10
=×
Take petrol density 719.7 kg/m3. 1.23 kg = 1.23 /0.7197 = 1.7 L