טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
M.Sc Thesis
M.Sc StudentKadosh Kobi
SubjectMicro-Turbojet to Adaptive Turbofan Conversion through a
Variable Thermodynamic Cycle
DepartmentDepartment of Aerospace Engineering
Supervisor Professor Beni Cukurel


Abstract

In this study, the viability, performance, and characteristics of a micro turbojet-to-turbofan conversion through the use of a continuously variable transmission (CVT) are investigated. By using an in-house thermodynamic simulation code, the performance of the simple cycle turbojet, a direct shaft fixed-gear turbofan, a fixed-gear turbofan with variable bypass, a CVT coupled turbofan with fixed bypass, and a CVT coupled turbofan with variable bypass were contrasted. The baseline turbojet and turbofan simulation findings were used to validate the models against a commercial software. Upon comparison to Gasturb11, a high quantitative agreement was indicated.

Examining the results of the CVT coupled turbofan, it was observed that the change in gear ratio alone yielded no noticeable improvement in the engine’s performance or efficiency. The reason for such effect being that the component’s behavior is coupled, and the change in gear ratio alone did not allow for individual control of the operating line on the different component maps.

To solve this issue, another control parameter was introduced - the variable bypass nozzle. Combining the effect of the gear change through a CVT with the effect of nozzle area change, independent control the each of the engine’s component was achieved.

Analyzing the results of the turbofan engine equipped with a variable bypass and CVT, it was observed that both the thrust and the efficiency were increased. The augmented thrust and efficiency were observed to be an artifact of enhanced component matching and wider operational range introduced by the combination of the CVT and the variable bypass capability. Therefore, the current research suggests that adaptation of a micro-turbojet into a variable cycle micro turbofan will greatly improve the performance and efficiency of existing engines, in addition to providing a pathway towards extended life for aging engine in various applications.