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Combustion engines
Published in Mike Tooley, Lloyd Dingle, Engineering Science, 2020
Note: This very useful equation tells us immediately that the propulsive efficiency will be increased; the closer the jet velocity is to the velocity of the aircraft. Unfortunately, as we bring these velocities closer together, then from equations 16.13 and 16.18 both the thrust power and the thermal efficiency are reduced! There is a way out of this dilemma, and that is to increase the mass flow rate of the gas stream (air flow) (m.a) through the engine. Then, as can be seen from PT=m˙a(vj2−va2)va, the thrust power can be maintained. To achieve this increase in the mass flow of the air through the engine, turbofan and other high frontal area engines are used.
Engine performance
Published in Mohammad H. Sadraey, Aircraft Performance, 2017
The propulsive efficiency, ηP, of a propulsion system is a measure of how effectively the engine power W˙out is used to power the aircraft. Propulsive efficiency is the ratio of the aircraft required power (thrust [T] times aircraft velocity [V]) to the power out of the engine W˙out . In equation form, this is written as () ηP=TVW˙out
Wind assisted propulsion system onboard ships: case study Flettner rotors
Published in Ships and Offshore Structures, 2021
Nader R. Ammar, Ibrahim S. Seddiek
Based on the true wind speed and direction weighting table, the predicted net output power of each Flettner rotor is evaluated. The calculated power takes into consideration the true wind characteristics and ship course during each route. From the predicted output power values, the amount for fuel saving at each route can be calculated. In order to calculate the true wind speed weights, the probability density function (pdf) for the wind speed data is performed at first as expressed in Equation (20) (Tillig and Ringsberg 2020). Using wind characteristic data at each route, a weighting scheme can be developed for the true wind speed and directions at each ship route as shown in Table 1. The amount of fuel saving due to using Flettner rotors is calculated as the summation of the wind and ship course data weights at each port all over the year. The previously mentioned method is used to predict the amount of fuel saving due to using Flettner rotor onboard the case study for the three ship routes. The data are based on the wind statistics for one year. The accuracy can be increased by increasing the time of the statistics for the true wind characteristics over more than one year. The uncertainties used in the method for estimating the amount of fuel saving due to using Flettner rotors include the following parameters: the forecast of true wind characteristics in ship route, the produced lift and drag forces from Flettner rotor on the ship hull, and the estimated propulsive efficiency as well as the main engine fuel consumption.
Aerodynamic analysis of the asynchronous phenomenon of a impinging jet on a concave surface
Published in International Journal of Computational Fluid Dynamics, 2019
Benoit LeBlanc, Gérard J. Poitras, Laurent-Emmanuel Brizzi, Gilles Roy
Impinging jets have been subject to numerous aerodynamic studies, mainly due to their heat transfer properties. They provide an effective way to transfer energy between a surface and the surrounding fluid in various applications. Heat transfer applications include cooling of electronic components, cooling for material forming processes, heating of optical surfaces for defogging, cooling of turbine components and many other industrial processes. In turbine applications, impinging jet flows are used to cool sections of the engine. For example, the blades outside the combustion chamber jet engine reach very high operating temperatures, hence the need to employ new methods to dissipate heat. The ultimate goal is controlling the temperature of turbine blade materials and allow for greater operating temperatures in the combustion chambers. Engine specific fuel consumption at a given propulsive efficiency can be achieved by improvements in thermal efficiency, Kyprianidis (2011). Jets impinging turbine blades are thus a method of forced convection cooling used by industry.
Sequential design of an injection molding process using a calibrated predictor
Published in Journal of Quality Technology, 2018
Po-Hsu Allen Chen, María G. Villarreal-Marroquín, Angela M. Dean, Thomas J. Santner, Rachmat Mulyana, José M. Castro
Many real-world applications require the simultaneous optimization of multiple competing objective functions. For example, Leatherman et al. (2014) developed a finite element model of the human knee to identify robust designs for a meniscal substitute that can provide both small mean and low variability in peak contact stress. For titanium nitride/titanium multilayer tool coatings, Draguljić et al. (2015) used computer experiments to simultaneously minimize the maximum radial stress (associated with cohesive failures) and the maximum shear stress (associated with adhesive failures). Atashkari et al. (2005) sought settings of the turbine inlet temperature, the pressure ratiom and the flight Mach number to optimize specific thrust, thrust-specific fuel consumption, propulsive efficiency, and thermal efficiency in the thermodynamic cycle of ideal turbojet engines.