What are the theoretical processes involved in the Atkinson cycle?
The Atkinson cycle, like the Otto cycle used in many gasoline engines, involves four theoretical processes:
1. Isentropic Compression(1-2): Air is compressed in the cylinder without heat transfer, raising its pressure and temperature. This process is similar in both Atkinson and Otto cycles.
2. Constant Pressure Heat Addition(2-3): Fuel is injected and combusts at a nearly constant pressure, further increasing the temperature. This process is also largely similar between the cycles.
3. Isentropic Expansion(3-4-4'): In the Atkinson cycle, this is where it diverges from the Otto cycle. The Atkinson cycle employs a longer isentropic expansion stroke compared to compression. This allows the hot, high-pressure gas to expand further, extracting more thermal energy and potentially leading to higher efficiency.
4. Constant Volume Heat Rejection(4'-1): Heat is removed from the cylinder at a constant volume, lowering the temperature and pressure back to its starting point.
Why do we need to reduce the compression ratio for the Atkinson cycle?
In the Otto cycle, after the combustion process, the force exerted on the piston during the power stroke increases so that when the piston reaches BDC, the exhaust valve opens, and useless heat discharges from the combustion chamber.
Therefore, this cycle uses to reduce the compression ratio for more expansion during the expansion stroke so that the entire force generated due to the combustion process can be used on the piston before the piston reaches BDC.
This means that the Atkinson cycle always has a lower/equivalent performance than the Otto cycle. However, the Otto cycle has lower thermal efficiency than the Atkinson cycle.
How to Calculate Thermal Efficiency of Atkinson Cycle?
Thermal Efficiency of Atkinson Cycle calculator uses Thermal Efficiency of Atkinson Cycle = 100*(1-Heat Capacity Ratio*((Expansion Ratio-Compression Ratio)/(Expansion Ratio^(Heat Capacity Ratio)-Compression Ratio^(Heat Capacity Ratio)))) to calculate the Thermal Efficiency of Atkinson Cycle, Thermal Efficiency of Atkinson Cycle refers to the effectiveness of Atkinson engine to convert heat energy from burning fuel into usable work output. Atkinson cycle engines prioritize a longer expansion stroke compared to a traditional Otto cycle. This theoretically allows for more complete extraction of thermal energy, potentially leading to higher efficiency. However, achieving this theoretical advantage in real-world engines requires balancing efficiency gains with power output. Thermal Efficiency of Atkinson Cycle is denoted by ηa symbol.
How to calculate Thermal Efficiency of Atkinson Cycle using this online calculator? To use this online calculator for Thermal Efficiency of Atkinson Cycle, enter Heat Capacity Ratio (γ), Expansion Ratio (e) & Compression Ratio (r) and hit the calculate button. Here is how the Thermal Efficiency of Atkinson Cycle calculation can be explained with given input values -> 62.24168 = 100*(1-1.4*((4-20)/(4^(1.4)-20^(1.4)))).