scholarly journals Computational Fluid Dynamics Investigation of a Core-Mounted Target-Type Thrust Reverser—Part 1: Reverser Stowed Configuration

2018 ◽  
Vol 140 (9) ◽  
Author(s):  
Tashfeen Mahmood ◽  
Anthony Jackson ◽  
Vishal Sethi ◽  
Bidur Khanal ◽  
Fakhre Ali
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Computer Aided Design ◽  
Three Dimensional ◽  
Engine Performance ◽  
Target Type ◽  
Research Centre ◽  
Experimental Investigations ◽  
Successful Implementation ◽  
Thrust Reverser

During the second half of the 90 s, NASA performed experimental investigations on six novel thrust reverser (TR) designs; core-mounted target-type thrust reverser (CMTTTR) design is one of them. To assess the CMTTTR efficiency and performance, NASA conducted several wind tunnel tests at sea level static (SLS) conditions. The results from these experiments are used in this paper series to validate the computational fluid dynamics (CFD) results. This paper is part one of the three-part series. Parts 1 and 2 discuss the CMTTTR in stowed and deployed configurations; all analyses in the first two papers are performed at SLS conditions. Part 3 discusses the CMTTTR in the forward flight condition. The key objectives of this paper are: first, to perform the three-dimensional (3D) CFD analysis of the reverser in stowed configuration; all analyses are performed at SLS condition. The second objective is to validate the acquired CFD results against the experimental data provided by NASA (Scott, C. A., 1995, “Static Performance of Six Innovative Thrust Reverser Concepts for Subsonic Transport Applications: Summary of the NASA Langley Innovative Thrust Reverser Test Program,” NASA—Langley Research Centre, Hampton, VA, Report No. TM-2000-210300). The third objective is to verify the fan and overall engine net thrust values acquired from the aforementioned CFD analyses against those derived based on one-dimensional (1D) engine performance simulations. The fourth and final objective is to examine and discuss the overall flow physics associated with the CMTTTR under stowed configuration. To support the successful implementation of the overall investigation, full-scale 3D computer aided design (CAD) models are created, representing a fully integrated GE-90 engine, B777 wing, and pylon configuration. Overall, a good agreement is found between the CFD and test results; the difference between the two was less than 5%.

Effects of equivalence ratio and CNG addition on engine performance and emissions in a dual sequential ignition engine

2019 ◽  
Vol 21 (6) ◽  
pp. 1067-1082 ◽  
Author(s):  
Ahmet Alper Yontar ◽  
Yahya Doğu
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Equivalence Ratio ◽  
Three Dimensional ◽  
Engine Performance ◽  
Maximum Torque ◽  
Performance And Emissions ◽  
Increment Rate ◽  
Engine Performance And Emissions ◽  
Dynamics Analyses

Compared to widening usage of CNG in commercial gasoline engines, insufficient but increasing number of studies have appeared in the open literature during last decades, while engine characteristics need to be quantified in exact numbers for each specific fuel and engine. CNG usage in spark-ignition engine offers many advantages such as high specific power outputs, knock resistance, and low CO2 emission. Engine performance and emissions are strong functions of equivalence ratio. This study focuses on determination of the effects of equivalence ratio on engine performance and emissions for a unique commercial engine for three fuels of gasoline, CNG, and gasoline–CNG mixture (90%–10%: G9C1). For this aim, the tests and the three-dimensional in-cylinder combustion computational fluid dynamics analyses were employed in quantification of engine characteristics at wide open throttle position. Equivalence ratios were defined between 0.7 and 1.4. The engine’s maximum torque speed of 2800 r/min was examined. The tested commercial engine is an intelligent dual sequential ignition engine which has unique features such as diagonally positioned two spark-plugs, dual sequential ignition with variable timing and asymmetrical combustion chamber. This gasoline engine was equipped with an independent CNG port-injection system and a specific engine control unit for CNG. In addition, the engine test system has a concomitant dual fuel delivery system that supplies gas fuel into intake airline while liquid gasoline is injected behind the intake valve. Other than testing the engine, the three-dimensional in-cylinder combustion computational fluid dynamics analyses were performed in Star-CD/es-ice software for the three fuels. The CFD model was built by using renormalization group equations, k–ε turbulence model, and G-equation combustion model. Computational fluid dynamics analyses were run for the compression ratio of 10.8:1, equivalence ratio of 1.1, and engine’s maximum torque speed of 2800 r/min. Test results show that brake torque for all fuels increases rapidly from the lean blend to the rich blend. The brake-specific fuel consumption for all fuels decreases from Φ = 0.7 through the stoichiometric region and then slightly increases up to Φ = 1.4. The volumetric efficiencies for three fuels have similar decreasing trend with respect to equivalence ratio. Overall, CNG addition decreases the performance values of torque, brake-specific fuel consumption, volumetric efficiency, brake thermal efficiency, while it decreases emissions of CO2, CO, HC, except NOx. Engine model results show that the maximum in-cylinder pressure is 72 bar at 722 crank angle degree (CAD), 68 bar at 730 CAD, and 60 bar at 735 CAD for gasoline, CNG, and G9C1, respectively. The cumulative heat release for gasoline is 9.09% higher than G9C1, while G9C1 is 15.71% higher than CNG. The CO2 mass fraction for gasoline is about 22.58% lower than G9C1, while it is 40.32% higher than CNG. The maximum mass fraction value of CO is 0.21, 0.17, and 0.08 for gasoline, CNG, and G9C1, respectively. The CO for G9C1 is overall 60.04% lower than CNG and 67.45% lower than gasoline. At maximum point, HC for G9C1 is 31.43% and 71.43% higher than gasoline and CNG, respectively. CNG has the highest level of NOx formation. Maximum NOx mass fractions are 0.0098, 0.0070, and 0.0043 for CNG, G9C1, and gasoline, respectively. After the ignition, the flame development is completed at 1.07, 1.18, and 1.28 ms for gasoline, G9C1, and CNG, respectively. Flame velocities are 28.52, 30.93, and 34.11 m/s for CNG, G9C1, and gasoline, respectively, at 2800 r/min and Φ = 1.1. When the time between ignition moment and top dead center moment is considered, the increment rate of flame center temperature is 904.19, 884.10, and 861.77 K/s for CNG, gasoline, and G9C1, respectively. The highest temperature increment rate occurs for CNG.

scholarly journals Computational Fluid Dynamics Investigation of a Core-Mounted Target-Type Thrust Reverser—Part 2: Reverser Deployed Configuration

2018 ◽  
Vol 140 (9) ◽  
Author(s):  
Tashfeen Mahmood ◽  
Anthony Jackson ◽  
Vishal Sethi ◽  
Bidur Khanal ◽  
Fakhre Ali
Keyword(s):  
Fluid Dynamics ◽  
Experimental Data ◽  
Computational Fluid Dynamics ◽  
Sea Level ◽  
Operating Conditions ◽  
Performance Characteristics ◽  
Target Type ◽  
Performance Criteria ◽  
Static Conditions ◽  
Thrust Reverser

Core-mounted target-type thrust reverser (CMTTTR) design was proposed by NASA in the second half of the 90 s. NASA carried out several experiments at static conditions, and their acquired results suggested that the performance characteristics of the CMTTTR design fall short to comply with the mandatory thrust reverser (TR) performance criteria, and were therefore regarded as an infeasible design. However, the authors of this paper believe that the results presented by NASA for the CMTTTR design require further exploration to facilitate the complete understanding of its true performance potential. This part 2 paper is a continuation from Part 1 (reverser stowed configuration) and presents a comprehensive three-dimensional (3D) computational fluid dynamics (CFD) analyses of the CMTTTR in deployed configuration. The acquired results are extensively analyzed for aforementioned TR configuration operating under the static operating conditions at sea level, i.e., sea-level static, International Standard Atmosphere (ISA); the analyses at forward flight conditions will be covered in part 3. The key objectives of this paper are: First, to validate the acquired CFD results with the experimental data provided by NASA; this is achieved by measuring the static pressure values on various surfaces of the deployed CMTTTR model. The second objective is to estimate the performance characteristics of the CMTTTR design and corroborate the results with experimental data. The third objective is to estimate the pressure thrust (i.e., axial thrust generated due to the pressure difference across various reverser surfaces) and discuss its significance for formulating the performance of any TR design. The fourth objective is to investigate the influence of kicker plate installation on overall TR performance. The fifth and final objective is to examine and discuss the overall flow physics associated with the thrust reverse under deployed configuration.

scholarly journals Computational Fluid Dynamics for Brain Circulation and Aneurysm with Therapeutic Devices

2004 ◽  
Vol 10 (2_suppl) ◽  
pp. 108-112 ◽  
Author(s):  
K. Fukasaku ◽  
M. Negoro ◽  
H. Iwase ◽  
K. Yokoi ◽  
R. Himeno
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Computer Aided Design ◽  
Three Dimensional ◽  
Dimensional Structure ◽  
Brain Vessels ◽  
Fluid Analysis ◽  
Brain Arteries ◽  
Aided Design ◽  
The Brain

We analysed fluid dynamics at brain arteries having multiple inflow and out flow like Willis ring based on clinical imaging modalities. In addition, we analysed fluid dynamics with therapeutic devices like coils and stents to simulate their influences to blood flow. 3D CTA and MRA obtained three-dimensional structures of the brain vessels. The centreline was obtained from the three dimensional structure. Diameter of the blood vessels was measured by 3D CTA/MRA then smooth surfaced blood vessel models were created. For the fluid analysis, we developed a home brew software which can display parameters such as streamline, etc. In addition, our CFD (computational fluid dynamics) software can work in collaboration with a CAD (computer aided design) software which we also developed (VCAD: Volume CAD). So, therapeutic devices such as coils, balloons and stents could be placed in the models and CFD analysis could be performed placing devices in the models. The flow pattern in the complicated vascular structure could be calculated such as Willis ring which has multiple inputs like ICA, VA and multiple outlets like MCA and PCA with communicating arteries. CFD with therapeutic devices could also analysed with our system.

scholarly journals Computational Analysis to Factor Wind into the Design of an Architectural Environment

2015 ◽  
Vol 2015 ◽  
pp. 1-10 ◽  
Author(s):  
Hassam Nasarullah Chaudhry ◽  
John Kaiser Calautit ◽  
Ben Richard Hughes
Keyword(s):  
Fluid Dynamics ◽  
Power Generation ◽  
Computational Fluid Dynamics ◽  
Three Dimensional ◽  
Numerical Data ◽  
Navier Stokes ◽  
Windward Side ◽  
Average Value ◽  
Continuity Equations ◽  
Prevailing Wind Direction

The effect of wind distribution on the architectural domain of the Bahrain Trade Centre was numerically analysed using computational fluid dynamics (CFD). Using the numerical data, the power generation potential of the building-integrated wind turbines was determined in response to the prevailing wind direction. The three-dimensional Reynolds-averaged Navier-Stokes (RANS) equations along with the momentum and continuity equations were solved for obtaining the velocity and pressure field. Simulating a reference wind speed of 6 m/s, the findings from the study quantified an estimate power generation of 6.4 kW indicating a capacity factor of 2.9% for the benchmark model. At the windward side of the building, it was observed that the layers of turbulence intensified in inverse proportion to the height of the building with an average value of 0.45 J/kg. The air velocity was found to gradually increase in direct proportion to the elevation with the turbine located at higher altitude receiving maximum exposure to incoming wind. This work highlighted the potential of using advanced computational fluid dynamics in order to factor wind into the design of any architectural environment.

scholarly journals Numerical Simulation and Analysis on Spray Drift Movement of Multirotor Plant Protection Unmanned Aerial Vehicle

Energies ◽  
2018 ◽  
Vol 11 (9) ◽  
pp. 2399 ◽  
Author(s):  
Fengbo Yang ◽  
Xinyu Xue ◽  
Chen Cai ◽  
Zhu Sun ◽  
Qingqing Zhou
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Droplet Size ◽  
Wind Field ◽  
Flow Model ◽  
Two Phase Flow ◽  
Plant Protection ◽  
Three Dimensional ◽  
Phase Flow ◽  
Two Phase

In recent years, multirotor unmanned aerial vehicles (UAVs) have become more and more important in the field of plant protection in China. Multirotor unmanned plant protection UAVs have been widely used in vast plains, hills, mountains, and other regions, and become an integral part of China’s agricultural mechanization and modernization. The easy takeoff and landing performances of UAVs are urgently required for timely and effective spraying, especially in dispersed plots and hilly mountains. However, the unclearness of wind field distribution leads to more serious droplet drift problems. The drift and distribution of droplets, which depend on airflow distribution characteristics of UAVs and the droplet size of the nozzle, are directly related to the control effect of pesticide and crop growth in different growth periods. This paper proposes an approach to research the influence of the downwash and windward airflow on the motion distribution of droplet group for the SLK-5 six-rotor plant protection UAV. At first, based on the Navier-Stokes (N-S) equation and SST k–ε turbulence model, the three-dimensional wind field numerical model is established for a six-rotor plant protection UAV under 3 kg load condition. Droplet discrete phase is added to N-S equation, the momentum and energy equations are also corrected for continuous phase to establish a two-phase flow model, and a three-dimensional two-phase flow model is finally established for the six-rotor plant protection UAV. By comparing with the experiment, this paper verifies the feasibility and accuracy of a computational fluid dynamics (CFD) method in the calculation of wind field and spraying two-phase flow field. Analyses are carried out through the combination of computational fluid dynamics and radial basis neural network, and this paper, finally, discusses the influence of windward airflow and droplet size on the movement of droplet groups.

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