Micro-Turbojet to Turbofan Conversion Via Continuously Variable Transmission: Thermodynamic Performance Study

Abstract

In this study, the viability, performance, and characteristics of a turbojet-to-turbofan conversion through the use of a continuously variable transmission (CVT) are investigated. By an in-house thermodynamic simulation code, the performance of the simple cycle turbojet, a direct shaft joined turbofan, and a CVT coupled turbofan with variable bypass is contrasted. The baseline turbojet and turbofan findings are validated against a commercial software. The comparison indicates high quantitative agreement. Analyzing the results of the turbofan engine equipped with a variable bypass and CVT, it is observed that both the thrust and the efficiency are increased. The augmented thrust is observed to be an artifact of enhanced component matching and wider operational range introduced by variable bypass capability. On the other hand, the introduction of CVT contributes to the reduction in fuel consumption. 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 toward extended use in various applications.

Unified low-pressure compressor concept for engines of future high-speed micro-unmanned aerial vehicles

“…10 3) gas generator without additional turbine, and (4) variable bypass nozzle. 10 Novelty and brief summary of the current paper…”

“…In terms of unified LPC aggressiveness, based on the previous section, the ''Unified LPC-A'' with 1.6 inner and 1.4 outer pressure ratio is assessed to be a feasible option, beyond which the aforementioned challenges increase and drawbacks grow. A thermodynamic cycle analysis similar to that of Kadosh and Cukurel, 10 which utilize the component maps of a baseline micro-turbojet engine of 0.6 kN and scaleddown ''NASA High-Speed Quiet Fan'' performance maps 15 is performed. The take-off condition, where fan speed is close to maximum and the thrust is 1.7 kN, is selected as the master design point.…”

“…Surveying the market of micro-gas turbines compatible with UAVs, the selection of engines in this category consists mostly of turbojets, with a distinct lacking of advanced turbofans. 10 The reviewed alternatives are generally not applicable to those small engines, as cost and simplicity are the main concerns, while the requirement for high performance persists.…”

“…Figure 1. Schematic representation of the concept: (1) LPC (fan), (2) CVT, (3) gas generator without additional turbine, and (4) variable bypass nozzle 10. …”

Değişken Çevrimli Mikro Turbofan Jet Motoru için Bütünleşik Düşük Basınç Kompresor Sisteminin Aerodinamik Analizleri

“…Most of the gas turbine engine types have been shown significant imrovements with respect to off-design performance and overall efficiency especially in the recent years, yet micro-scaled gas turbine (under 2 kN of thrust) is the only one have been left to be investigated. In the market search, application of gas turbines for UAV propulsion technology is generally restricted by reciprocating and turbojet engines without advanced micro-scaled turbofans [14].…”