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UAS Propulsion System Design
Published in R. Kurt Barnhart, Douglas M. Marshall, Eric J. Shappee, Introduction to Unmanned Aircraft Systems, 2021
Michael T. Most, Graham Feasey
Turbojets, developed during World War II (WWII) are very noisy, and in terms of fuel consumption, extremely inefficient, particularly at lower airspeeds. On the other hand, they are without the additional complexity and weight of an integral gearbox, prop or fan, and therefore, exhibit a high specific thrust. Turbojets have not recently been installed on UASs but have provided the propulsive force for the Ryan Firefly (General Electric YJ97-GE-3 turbojet producing 17 kN, or 4,000 lb of thrust), the Ryan Firebee (Continental J69-T-29A turbojet generating 7.6 kN, or 1,700 lb of thrust), and Firebee II (Teledyne CAE J69-T-6 turbojet producing 8.18 kN or 1,840 lb of thrust), a UAS frequently flown on reconnaissance missions in Vietnam and as recently as 2003 in Iraq.
Internal combustion engines and fuels
Published in J. F. Griffiths, J. A. Barnard, Flame and Combustion, 2019
J. F. Griffiths, J. A. Barnard
In these engines, air is first compressed and then fuel is injected and burned continuously in a combustion chamber. The burned gas at high pressure and temperature then provides the energy source. The propulsion of a turbojet is gained from the thrust at the exhaust, which is generated by increasing the momentum of the fluid passing through the engine. The exhaust nozzle has an extremely important function in accelerating the fluid to high velocity. The sole function of the turbine is to drive the air compressor which, in the simplest design, is a single spool system; the turbine downstream from the combustion chamber drives the upstream, air compressor (Fig. 13.3). Propulsion by a turboprop aircraft engine relies on an independent power turbine to drive a propeller. The power turbine is driven by the high velocity, combustion exhaust gases and is capable of rotating at different speeds from the compressor/turbine shaft. In industrial and marine gas turbine applications the power turbine follows the turbojet type of compressor/burner/turbine combination. Some industrial and marine gas engines are derived from turbojets.
Force-System Resultants and Equilibrium
Published in Richard C. Dorf, The Engineering Handbook, 2018
with V in kt. Although the range is explicitly independent of V,V must have the value appropriate to the cruise (L/D). Increasing V by increasing the altitude or W/S will not increase the range but will decrease the flight time (and increase the power required). Although the maximum range occurs when (L/D) is at its maximum value, the associated airspeed, especially with an aspirated engine, is usually much lower than the maximum airspeed of the aircraft and the required power for cruise is below the best operating point for the engine. Consequently, the cruise of a piston-prop is customarily at 75% of the maximum power available to reduce flight time and favor the engine. With respect to other power plants, whereas a turbojet is a single-flow engine that produces only jet thrust, a turbofan is a multiflow engine that uses a turbine to drive a multibladed ducted fan that produces thrust power in addition to jet thrust. It has characteristics of both turbojet and propeller aircraft, and its performance (and specific fuel consumption) lies in the region between the two but closer to the turbojet. The turbojet range equation is normally used.
Thermodynamic and environmental considerations of small turbojet engine under different design variables
Published in Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, 2021
The usage of an aerovehicle has enlarged to many applications that people need in several fields of daily life. Especially, unmanned aircraft has gained new missions for military and civil aviation. The propulsion system of these systems could be commonly gas turbine engines. To meet rising demand to thrust power, the related engineers have focused on the improvement of the turbojet engines (Turan 2012). For this aim, a number of dimensions for these systems have existed. Increasing interest in small-scaled turbojet engines have led to rise in the studies about the performance of these system. The most distinct features of turbojet systems are high thrust-to-weight ratio compared with piston engines. In this study, a turbojet engine producing about 1.36 kN at the maximum take-off power was dealt with. It is very similar to a TRS-18 turbojet engine. These systems have been installed in several aircrafts. The major units of a turbojet engine considered consist of a compressor, combustor, and turbine. The pressure ratio of the compressor is 3.4, whereas the turbine inlet temperature is 1050 K at the baseline point. Also, mass flow entering the engine is 2.49 kg/s, while fuel flow is 0.0387 kg/s. In this context, the air-to-fuel ratio (AFR) is found to be 64.34. The major components and the station numbers of the turbojet engine are demonstrated in Figure 1. Moreover, Table 1 presents the thermodynamic value of turbojet engine on component basis.