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

Energies ◽  
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.

Unsteady Responses of the Impeller of a Centrifugal Compressor Exposed to Pulsating Backpressure

2018 ◽  
Vol 141 (4) ◽  
Author(s):  
Mengying Shu ◽  
Mingyang Yang ◽  
Ricardo F. Martinez-Botas ◽  
Kangyao Deng ◽  
Lei Shi
Keyword(s):  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Centrifugal Compressor ◽  
Combustion Engine ◽  
Fluid Dynamic ◽  
Flow Behavior ◽  
Three Dimensional ◽  
Intake Manifold ◽  
Unsteady Simulation

The flow in intake manifold of a heavily downsized internal combustion engine has increased levels of unsteadiness due to the reduction of cylinder number and manifold arrangement. The turbocharger compressor is thus exposed to significant pulsating backpressure. This paper studies the response of a centrifugal compressor to this unsteadiness using an experimentally validated numerical method. A computational fluid dynamic (CFD) model with the volute and impeller is established and validated by experimental measurements. Following this, an unsteady three-dimensional (3D) simulation is conducted on a single passage imposed by the pulsating backpressure conditions, which are obtained by one-dimensional (1D) unsteady simulation. The performance of the rotor passage deviates from the steady performance and a hysteresis loop, which encapsulates the steady condition, is formed. Moreover, the unsteadiness of the impeller performance is enhanced as the mass flow rate reduces. The pulsating performance and flow structures near stall are more favorable than those seen at constant backpressure. The flow behavior at points with the same instantaneous mass flow rate is substantially different at different time locations on the pulse. The flow in the impeller is determined by not only the instantaneous boundary condition but also by the evolution history of flow field. This study provides insights in the influence of pulsating backpressure on compressor performance in actual engine situations, from which better turbo-engine matching might be benefited.

Design and Optimization of the Restrictor of a Race Car

2015 ◽  
Author(s):  
Prithvi Raj Kokkula ◽  
Shashank Bhojappa ◽  
Selin Arslan ◽  
Badih A. Jawad
Keyword(s):  
Fluid Dynamics ◽  
Pressure Drop ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Air Flow ◽  
Intake Manifold ◽  
Maximum Pressure ◽  
Cross Sectional ◽  
Formula Sae

Formula SAE is a student competition organized by SAE International. The team of students design, manufacture and race a car. Restrictions are imposed by the Formula SAE rules committee to restrict the air flow into the intake manifold by putting a single restrictor of 20 mm. This rule limits the maximum engine power by reducing the mass flow rate flowing to the engine. The pull is greater at higher rpms and the pressure created inside the cylinder is low. As the diameter of the flow path is reduced, the cross sectional area for flow reduces. For cars running at low rpm when the engine requires less air, the reduction in area is compensated by accelerated flow of air through the restrictor. Since this is for racing purpose cars here are designed to run at very high rpms where the flow at the throat section reach sonic velocities. Due to these restrictions the teams are challenged to come up with improved restrictor designs that allow maximum pressure drop across the restrictor’s inlet and outlet. The design considered for optimizing a flow restrictor is a venturi type having 20 mm restriction between the inlet and the outlet complying with the rules set by Formula SAE committee. The primary objective of this work is to optimize the flow restriction device that achieves maximum mass flow and minimum pull from the engine. This implies the pressure difference created due to the cylinder pressure and the atmospheric pressure at the inlet should be minimum. An optimum flow restrictor is designed by conducting analysis on various converging and diverging angles and coming up with an optimum value. Venturi type is a tubular pipe with varying diameter along its length, through which the fluid flows. Law of governing fluid dynamics states that the “Velocity of the fluid increases as it passes through the constriction to satisfy the principle of continuity”. An equation can be derived from the combination of Bernoulli’s equation and Continuity equation for the pressure drop due to venturi effect. [1]. A Computational Fluid Dynamics (CFD) tool is used to calculate the minimum pressure drop across the restrictor by running a series of analysis on various converging and diverging angles and calculating the pressure drop. As a result, an optimum air flow restrictor is achieved that maximizes the mass flow rate and minimizes the engine pull.

scholarly journals Modelling the Exhaust Gas Recirculation Mass Flow Rate in Modern Diesel Engines

2016 ◽  
Author(s):  
Zhijia Yang ◽  
Edward Winward ◽  
Gary O'Brien ◽  
Richard Stobart ◽  
Dezong Zhao
Keyword(s):  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Diesel Engines ◽  
Exhaust Gas Recirculation ◽  
Exhaust Gas ◽  
Gas Recirculation

scholarly journals Simultaneous Air Fraction and Low-Pressure EGR Mass Flow Rate Estimation for Diesel Engines

2013 ◽  
Vol 46 (2) ◽  
pp. 731-736 ◽  
Author(s):  
F. Castillo ◽  
E. Witrant ◽  
V. Talon ◽  
L. Dugard
Keyword(s):  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Diesel Engines ◽  
Low Pressure ◽  
Rate Estimation

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

2020 ◽  
Vol 2020 ◽  
pp. 1-9
Author(s):  
Zhimao Li ◽  
Changdong Chen ◽  
Houju Pei ◽  
Benben Kong
Keyword(s):  
Neural Networks ◽  
Genetic Algorithms ◽  
Mass Flow Rate ◽  
Relative Error ◽  
Mass Flow ◽  
Flow Rate ◽  
Structural Parameters ◽  
Bp Neural Networks ◽  
Inlet System ◽  
Air Inlet

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.

Analytical Modeling of Gaseous Slip Flow in Parabolic Microchannels

2014 ◽  
Vol 136 (7) ◽  
Author(s):  
Farzad Tahmouresi ◽  
Samir K. Das
Keyword(s):  
Pressure Distribution ◽  
Friction Factor ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Analytical Modeling ◽  
Separation Of Variables ◽  
Slip Flow ◽  
Aspect Ratios ◽  
Gaseous Slip Flow

The paper presents an analytical solution of velocity, mass flow rate, and pressure distribution for fully developed gaseous slip flow in nonsymmetric and symmetric parabolic microchannels. The flow is considered to be steady, laminar, and incompressible with constant fluid properties. Fully developed gaseous slip flow in microchannels of parabolic cross section is solved analytically for various aspect ratios using a parabolic cylindrical coordinate system on applying the method of separation of variables. Prior to apply separation of variables, Arfken transform [Arfken, 1970, Mathematical Methods for Physicists, Academic Press, Orlando, FL, Ch. 2] was used on momentum equations and first-order slip boundary conditions at each channel wall were imposed. A simple model is proposed to predict the friction factor and Reynolds number product fRe for slip flow in parabolic microchannels. Through the selection of a characteristic length scale, the square root of cross-sectional area and the effect of duct shape have been minimized. The results of a normalized Poiseuille number for symmetric parabolic microchannels (ɛ=1) shows good agreement with the previous results [Morini et al., 2004, “The Rarefaction Effect on the Friction Factor of Gas Flow in Micro/Nano-Channels,” Superlattices Microstruct., 35(3–6), pp. 587–599; Khan and Yovanovich, 2008, “Analytical Modeling of Fluid Flow and Heat Transfer in Microchannel/Nanochannel Heat Sinks,” J. Thermophys. Heat Transf., 22(3), pp. 352–359] for rectangular microchannels. The developed model can be used to predict mass flow rate and pressure distribution of slip flow in parabolic microchannels.

Experimental Study on Centrifugal Compressor Performance at Pulsating Backpressure Conditions

2019 ◽  
Author(s):  
Mengying Shu ◽  
Mingyang Yang ◽  
Kaiyue Zhang ◽  
Ricardo F. Martinez-Botas ◽  
Kangyao Deng
Keyword(s):  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Centrifugal Compressor ◽  
Rotational Speed ◽  
Hysteresis Loops ◽  
Intake Manifold ◽  
Stable Operation ◽  
Compressor Performance ◽  
Turbo Engine

Abstract The flow in the intake manifold of a downsized internal combustion engine has become more unsteady due to the reduction of cylinder number and increasing boosting level. The turbocharger compressor is thus imposed by an unsteady backpressure when matched with an engine. It has been experimentally confirmed that the compressor performance is affected when exposed to pulsating backpressure. In order to enhance compressor stability and achieve better turbo-engine matching, it is necessary to understand behaviors of compressor at pulsating backpressure conditions. In this study, the performance of compressor exposed to pulsating backpressure is experimentally studied on the compressor test rig located in Shanghai Jiao Tong University. The results show that compressor performance with pulsating backpressure is notably different from the one with constant backpressure. Hysteresis loops which encapsulate the steady performance are generated at pulsating backpressure conditions due to filling-emptying effect. The mass flow rate, pulse frequency and compressor rotational speed all have evident influence on dynamic behaviors of the compressor. As the mass flow rate and rotational speed increase, hysteresis loops are enlarged and the unsteady behaviors are enhanced. The influence of pulsating backpressure on the compressor surge margin is analyzed in detail. Results demonstrate that the stable operation range is evidently influenced by the pulsating backpressure. Particularly, the mass flow rate of surge is postponed by 15.1% compared with the corresponding constant backpressure condition. Fast Fourier Transform method (FFT) is applied to identify the initiation of surge. The frequency domain analysis proves that the pulsating backpressure has little influence on the frequency of surge, but the strength of surge is alleviated indicated by the magnitude of fluctuations. The study provides an insight on the influence of pulsating backpressure on the centrifugal compressor, which can benefit the design methodology of compressor as well as turbo-engine matching.

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

2015 ◽  
Vol 04 (02) ◽  
pp. 1550007 ◽  
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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