The emerging need for cost- and energy-efficient propulsion systems have shifted the research interest to radical concepts, with several challenges to overcome in order to enter into service. However, revitalizing old, yet provably successful engine designs - a practice followed by engine manufacturers over the years - can provide low risk alternative solutions to move immediate market demands. The paper reviews this approach, known as concept of growth engines or core commonality, and investigates how a geometrically fixed or geometrically similar engine core can be utilized across a family of engines. The development programs of the highly successful CFM56 and PT6 engine families are analyzed, proving the success of this concept over the years. This concept is based on the engineering paradigm of product families and is briefly presented from a theoretical perspective. Implementation methods and simulation tools to initiate, conceptualize, design and evaluate an engine family program are reviewed. The potential application of engine core commonality into electrified propulsion systems is investigated. Design challenges and opportunities that electrification imposes to the growth engine concept are discussed. Finally, future research directions for achieving a successful family of engines for electrified applications are proposed.

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