chawki said:Homework Statement
An engine burns 1.4 kg of gasoline per hour and yields 3.5 kW of power.
Homework Equations
Calculate the efficiency of the engine when the heating value of gasoline is 43 MJ/kg.
The Attempt at a Solution
Plz i just need the rule for engine efficiency.
Not really.chawki said:ok so:
efficiency = power generated/heat energy ?
You are correct. Efficiency is the ratio of energy output to energy input. This is the same as power output/power input.chawki said:in my work, efficiency has no unit.
it's kw/kw
Andrew Mason said:You are correct. Efficiency is the ratio of energy output to energy input. This is the same as power output/power input.
AM
Engine efficiency is calculated by dividing the amount of energy output (in this case, 3.5 kW) by the amount of energy input (1.4 kg gasoline/hr). This gives you a percentage which represents the efficiency of the engine.
The energy content of gasoline varies depending on the composition, but on average, it contains about 45 MJ/kg. This means that for every 1.4 kg of gasoline, 63 MJ of energy is available.
The higher the engine efficiency, the lower the fuel consumption. This is because a more efficient engine can convert a greater percentage of the energy in the fuel into useful work, reducing the amount of fuel needed to produce the same amount of power.
Some factors that can affect engine efficiency include the design and condition of the engine, the type and quality of fuel used, the load on the engine, and the operating temperature.
Engine efficiency can be improved through regular maintenance and tune-ups, using high-quality fuel, reducing the load on the engine, and utilizing technologies such as turbochargers and variable valve timing.