Calculate jet engine bypass ratio from air mass flows, solve either stream, or split total inlet flow using a known ratio. A separate mode compares fan and core thrust; thrust ratio does not determine mass-flow bypass ratio.
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Bypass Ratio Formula
The following formula is used to calculate the bypass ratio for a given mass flow rate of bypass air and core air.
Variables:
- BR is the bypass ratio
- Mbypass is the mass flow rate of bypass air in kg/s
- Mcore is the mass flow rate of core air in kg/s
To calculate the bypass ratio, divide the mass flow rate of bypass air by the mass flow rate of core air.
What is a Bypass Ratio?
The bypass ratio is a parameter used in jet engines to describe the ratio of the mass flow rate of air that bypasses the engine core to the mass flow rate of air that passes through the engine core. High bypass ratios are typical in modern commercial jet engines, as they contribute to greater fuel efficiency and reduced noise levels. The bypass air provides additional thrust and helps cool the engine, making it more efficient and environmentally friendly.
How to Calculate Bypass Ratio?
The following steps outline how to calculate the Bypass Ratio.
- First, determine the mass flow rate of bypass air (Mbypass).
- Next, determine the mass flow rate of core air (Mcore).
- Finally, calculate the bypass ratio using the formula BR = Mbypass / Mcore.
- Select the value to solve, enter the required quantities and units, then select Calculate. For 200 kg/s bypass air and 50 kg/s core air, the bypass ratio is 4:1 and the bypass mass-flow share is 80%; this is not the fan thrust share.
Example Problem :
Use the following variables as an example problem to test your knowledge.
Mass flow rate of bypass air (Mbypass) = 200 kg/s
Mass flow rate of core air (Mcore) = 50 kg/s
