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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.
Dimensional Analysis and Dynamic Similitude
Published in William S. Janna, Introduction to Fluid Mechanics, Sixth Edition, 2020
A jet engine takes in air at atmospheric pressure, compresses it, and uses it in a combustion process to generate high-temperature gases. These gases are then passed through a turbine to provide power for compressing the inlet air. After passing through the turbine, the gases are exhausted to the atmosphere to deliver thrust. The thrust FT developed is a function of inlet air density ρa and pressure pa , pressure after the compressor pc , energy content in the fuel E, exhaust gas pressure pe , and velocity V. Use dimensional analysis to develop an expression for the thrust.
Introduction to Reliability Design of Mechanical System
Published in Seong-woo Woo, Design of Mechanical Systems Based on Statistics, 2021
An aircraft utilizes an onboard propulsion from the mechanical power produced by an aircraft engine, which is either a propeller or jet propulsion. Especially, jet engines supply airplane thrust by taking in the air, compressing the air, and injecting fuel into the hot-compressed air mixture in a combustion chamber, and the accelerated exhaust emits rearwards through a turbine. Modern gas turbine engines are operated by the Brayton cycle that comprises a gas compressor, a combustion chamber, and an expansion turbine (Figures 1.12 and 1.13).
Market Basis for Salt-Cooled Reactors: Dispatchable Heat, Hydrogen, and Electricity with Assured Peak Power Capacity
Published in Nuclear Technology, 2020
Molten Salt Reactors were originally developed in the late 1950s as part of the U.S. Aircraft Nuclear Propulsion Program that had as its goal a jet-powered bomber of unlimited range to deliver nuclear weapons to the Soviet Union. The reactor was chosen based on its ability to efficiently couple to a jet engine, i.e., a Brayton power cycle. In a jet engine, air is compressed, heated, and exhausted through a turbine that powers the compressor. That requires a reactor that delivers all of its heat at high temperatures significantly above the temperature of the compressed air. In modern gas turbines, that compressed air temperature is above 400°C. Salt reactors efficiently couple to Brayton power cycles with all heat delivered significantly above 400°C.
The effect of using triple bio-fuel blend with Jet-A on engine performance and emissions in mini-scale turbojet engine
Published in Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, 2023
In recent years, there have been many developments on small-scale gas turbine engines. Small-scale gas turbine engines, with their ability to obtain high power from small volume, high performance and working with various fuels, bring to the forefront unmanned vehicles, especially for the aviation industry (Marcellan, Visser, and Colonna 2016). In jet engine, which is a type of gas turbine, the thrust consists of momentum depending on the kinetic energy (their velocity) of the exhaust gases (Enagi, Al-Attab, and Zainal 2018). The use of small-scale gas turbine engines has increased in unmanned aerial vehicles, especially in the commercial aviation sector in recent years (Turan 2012). One way to improve the performance of gas turbine engines is to make design changes, while another way is to work on the fuels used. Abd Lati et al. (Abd Lati, Ahma, and Nasir 2017) developed a theoretical model using kerosene fuel on the K-180 G micro gas turbine engine, confirming the thrust performance results with an experimental study. Davies et al. (Davies, Gunabalan, and Davies 2016), used eight different fuels (diesel, Jet-A1, palm oil biodiesel, cooking oil biodiesel, 20/80 (PB/Jet A1), 20/80 (COB/Jet-A1), 50/50 (PB/Jet-A1), and 50/50 (COB/Jet-A1) to performed performance tests on a KingTech K140G gas turbine engine. In this study, it was seen that the low thrust was not only due to low calorific values, but also to the combustion time and low combustion efficiency due to the viscosity of different fuels. Bayona-Roa et al. (Bayona-Roa et al. 2019) performed simulations for different biofuel blends of PT6A turbine engine using GasTurb software. In this study, they performed simulations by estimating the fuel calorific values in various ways and stated that there was no difference on the results. At the same time, Badami et al. (Badami et al. 2014), in a similar study, obtained thrust, TSFC and emission values using experimental and semi-empirical equations and ANSYS software and compared them with pure jet fuel.