Structural Optimization of the Aircraft NACA Inlet Based on BP Neural Networks and Genetic Algorithms

With the development of the increasing demand for cooling air in cabin and electronic components on aircraft, it urges to present an energy-efficient optimum method for the ram air inlet system. A ram air performance evaluation method is proposed, and the main structural parameters can be extended to a certain type of aircraft. The influence of structural parameters on the ram air performance is studied, and a database for the performance is generated. A new method of integrating the BP neural networks and genetic algorithm is used for structure optimization and is proven effective. Moreover, the optimum result of the structure of the NACA ram air inlet system is deduced. Results show that (1) the optimization algorithm is efficient with less prediction error of the mass flow rate and fuel penalty. The average relative error of the mass flow rate is 1.37%, and the average relative error of the fuel penalty is 1.41% in the full samples. (2) Predicted deviation analysis shows very little difference between optimized and unoptimized design. The relative error of the mass flow rate is 0.080% while that of the fuel penalty is 0.083%. The accuracy of the proposed optimization method is proven. (3) The mass flow rate after optimization is increased to 2.506 kg/s, and the fuel penalty is decreased by 74.595 Et kg. The BP neural networks and genetic algorithms are studied to optimize the design of the ram air inlet system. It is proven to be a novel approach, and the efficiency can be highly improved.

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Validated Analytical Modeling of Diesel Engines Intake Manifold with a Flexible Crankshaft

Energies ◽

10.3390/en14051287 ◽

2021 ◽

Vol 14 (5) ◽

pp. 1287

Author(s):

Salah A.M. Elmoselhy ◽

Waleed F. Faris ◽

Hesham A. Rakha

Keyword(s):

Mass Flow Rate ◽

Relative Error ◽

Mass Flow ◽

Flow Rate ◽

Diesel Engines ◽

Analytical Modeling ◽

Vacuum Pressure ◽

Analytical Models ◽

Intake Manifold ◽

Flow Losses

The flexibility of a crankshaft exhibits significant nonlinearities in the analysis of diesel engines performance, particularly at rotational speeds of around 2000 rpm. Given the explainable mathematical trends of the analytical model and the lack of available analytical modeling of the diesel engines intake manifold with a flexible crankshaft, the present study develops and validates such a model. In the present paper, the mass flow rate of air that goes from intake manifold into all the cylinders of the engine with a flexible crankshaft has been analytically modeled. The analytical models of the mass flow rate of air and gas speed dynamics have been validated using case studies and the ORNL and EPA Freeway standard drive cycles showing a relative error of 7.5% and 11%, respectively. Such values of relative error are on average less than those of widely recognized models in this field, such as the GT-Power and the CMEM, respectively. A simplified version for control applications of the developed models has been developed based on a sensitivity analysis. It has been found that the flexibility of a crankshaft decreases the mass flow rate of air that goes into cylinders, resulting in an unfavorable higher rate of exhaust emissions like CO. It has also been found that the pressure of the gas inside the cylinder during the intake stroke has four elements: a driving element (intake manifold pressure) and draining elements (vacuum pressure and flow losses and inertial effect of rotating mass). The element of the least effect amongst these four elements is the vacuum pressure that results from the piston's inertia and acceleration. The element of the largest effect is the pressure drop that takes place in the cylinder because of the air/gas flow losses. These developed models are explainable and widely valid so that they can help in better analyzing the performance of diesel engines.

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Thermo-Efficiencies of a Tubular Combustor Under Different Inlet Conditions

International Journal of Turbo and Jet Engines ◽

10.1515/tjj-2018-0005 ◽

2018 ◽

Vol 0 (0) ◽

Cited By ~ 1

Author(s):

Ahmet Topal ◽

Onder Turan

Keyword(s):

Mass Flow Rate ◽

Mass Flow ◽

Flow Rate ◽

Loading Condition ◽

Inlet Temperature ◽

Test Rig ◽

Aerodynamic Loading ◽

Air Inlet ◽

Energy And Exergy ◽

Inlet Conditions

AbstractExergy efficiencies of the gas turbine become an important issue in recent years and by the way conducted studies regarding to this subject shows that the highest exergy destruction is observed in the combustor and afterburner modules. Therefore it is beneficial to perform analyses that are specific to the combustor exergy efficiency. This study includes the energy$\left( {{\eta _{cc}}} \right)$and exergy efficiencies$\left( {{\eta _{ex}}} \right)$(thermo-efficiencies) of a tubular combustor for different inlet conditions. Both of the first law and second law efficiencies have been performed on the experimental data and efficiency trends are investigated for changing aerodynamic conditions. Combustor tests have been conducted in an atmospheric test rig and combustor air inlet temperature$\left( {{T_{03}}} \right)$, air mass flow rate$\left( {{{\dot m}_a}} \right)$and fuel mass flow rate$\left( {{{\dot m}_f}} \right)$have been set for the pre-defined conditions. Moreover, exhaust gas emissions were measured by using a gas analyzer system. In the study, highest energy and exergy efficiencies have been obtained at minimum aerodynamic loading condition as 99.0 % and 70.2 % respectively. Moreover efficiencies have the lowest value as 92.7 % and 54.0 % at the maximum aerodynamic loading condition. To summarize, this study aims to show the energy and exergy trends by changing inlet conditions of a tubular combustor in the atmospheric test rig.

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A CFD technique to investigate the chocked flow and heat transfer characteristic in a micro-channel heat sink

International Journal of Computational Materials Science and Engineering ◽

10.1142/s2047684115500074 ◽

2015 ◽

Vol 04 (02) ◽

pp. 1550007 ◽

Cited By ~ 1

Author(s):

Ahmad Azari ◽

Abdorrasoul Bahraini ◽

Saeideh Marhamati

Keyword(s):

Heat Transfer ◽

Mass Flow Rate ◽

Relative Error ◽

Mass Flow ◽

Flow Rate ◽

Heat Sink ◽

Stanton Number ◽

Micro Channel ◽

Flow And Heat Transfer ◽

Channel Exit

In this research, a Computational Fluid Dynamics (CFD) technique was used to investigate the effect of choking on the flow and heat transfer characteristics of a typical micro-channel heat sink. Numerical simulations have been carried out using Spalart–Allmaras model. Comparison of the numerical results for the heat transfer rate, mass flow rate and Stanton number with the experimental data were conducted. Relatively good agreement was achieved with maximum relative error 16%, and 8% for heat transfer and mass flow rate, respectively. Also, average relative error 9.2% was obtained for the Stanton number in comparison with the experimental values. Although, the results show that the majority of heat was transferred in the entrance region of the channel, but the heat transfer in micro-channels can also be affected by choking at channel exit. Moreover, the results clearly show that, the location where the flow is choked (at the vicinity of the channel exit) is especially important in determining the heat transfer phenomena. It was found that Spalart–Allmaras model is capable to capture the main features of the choked flow. Also, the effects of choking on the main characteristics of the flow was presented and discussed.

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The Use of Dehumidifiers in Desiccant Cooling and Dehumidification Systems

Journal of Heat Transfer ◽

10.1115/1.3246990 ◽

1986 ◽

Vol 108 (3) ◽

pp. 684-692 ◽

Cited By ~ 30

Author(s):

E. Van den Bulck ◽

J. W. Mitchell ◽

S. A. Klein

Keyword(s):

Mass Flow Rate ◽

Mass Flow ◽

Flow Rate ◽

Inlet Temperature ◽

Cooling Load ◽

Humidity Ratio ◽

Air Mass ◽

Air Inlet ◽

Additional Control ◽

Good Agreement

The use of rotary dehumidifiers in gas-fired open-cycle desiccant cooling systems is investigated by analyzing the performance of the rotary heat exchanger–rotary dehumidifier subsystem. For a given cooling load, the required regeneration heat supply can be minimized by choosing appropriate values for the regeneration air mass flow rate and the wheel rotation speed. A map is presented showing optimal values for rotational speed and regeneration flow rate as functions of the regeneration air inlet temperature and the process air inlet humidity ratio. This regeneration temperature is further optimized as a function of the process humidity ratio. In the analysis, the control strategy adjusts the process air mass flow rate to provide the required cooling load. Additional control options are considered and the sensitivity of the regeneration heat required to the wheel speed, regeneration air mass flow rate, and inlet temperature is discussed. Experimental data reported in the literature are compared with the analytical results and indicate good agreement.

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