Evaluation and design methods for high‐efficiency charring composite under complex coupling mechanisms in both material and boundary layer

2020 ◽  
Vol 138 (1) ◽  
pp. 49615
Author(s):  
Weijie Li ◽  
Jie Huang ◽  
Zhongwei Zhang ◽  
Haiming Huang ◽  
Jun Liang
Keyword(s):  
Boundary Layer ◽  
High Efficiency ◽  
Design Methods ◽  
Coupling Mechanisms

Design and Analysis of a High Pitch to Chord Ratio Cascade Representative of Ducted Propfans

1991 ◽  
Author(s):  
A. Weber ◽  
W. Steinert ◽  
H. Starken
Keyword(s):  
Boundary Layer ◽  
Mach Number ◽  
High Efficiency ◽  
Pressure Ratio ◽  
Flow Analysis ◽  
High Pitch ◽  
Integral Boundary ◽  
Pressure Loss Coefficient ◽  
Distribution Boundary ◽  
Very High

Efforts to reduce the specific fuel consumption of a modern aero engine focus in particular on increasing the by-pass ratio beyond the current level of around 5. One concept is the counterrotating shrouded propfan operating at low overall pressure ratio and having only very few fan blades of extremely high pitch/chord ratios. The relative inlet Mach numbers cover a range from 0.7 at the hub to 1.1 at the tip section of the first rotor. A propfan cascade was designed by taking into account two characteristic features of a propfan blade-blade section: • a very high pitch/chord ratio of s/c = 2.25 • an inlet Mach number of M1 = 0.90 which leads to transonic flow conditions inside the blade passage In the design process a profile generator and a quasi-3D Euler solver were used iteratively to optimize the profile Mach number distribution. Boundary layer behavior was checked with an integral boundary layer code. The cascade design was verified experimentally in the transonic cascade wind tunnel of DLR at Cologne. The extensive experimental results confirm the design goal of roughly 5 degree flow turning. A total pressure loss coefficient of less than 1.5% was measured at design conditions. This validates the very high efficiency level the propfan concept is calling for. A 2D Navier-Stokes flow analysis code yields good results in comparison to the experimental ones.

Loss and Flow Path Studies on Centrifugal Compressors—Part II

1970 ◽  
Vol 92 (3) ◽  
pp. 287-300 ◽  
Author(s):  
O. E. Balje´
Keyword(s):  
Boundary Layer ◽  
High Efficiency ◽  
Flow Path ◽  
Flow Conditions ◽  
Centrifugal Compressors ◽  
Mixed Flow ◽  
Path Design ◽  
Balanced Flow ◽  
Efficiency Data ◽  
Rotor Flow

The flow conditions in a mixed flow rotor are investigated for a “pressure balanced” flow path design. Boundary layer arguments are applied to calculate the losses in the rotor as well as in the subsequent diffuser section. The resulting efficiency data imply a comparatively high efficiency potential for mixed flow compressors with multiple cascaded components, designed on the premise of a “pressure balanced” rotor flow path.

scholarly journals A new multicopter-based unmanned aerial system for pollen and spores collection in the atmospheric boundary layer

2019 ◽  
Vol 12 (3) ◽  
pp. 1581-1598 ◽  
Author(s):  
Claudio Crazzolara ◽  
Martin Ebner ◽  
Andreas Platis ◽  
Tatiana Miranda ◽  
Jens Bange ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Atmospheric Boundary Layer ◽  
High Efficiency ◽  
Aerosol Particles ◽  
Pollen Grains ◽  
Dust Particles ◽  
Unmanned Aerial System ◽  
Pollen Concentration ◽  
Concentration Data ◽  
Particle Collection

Abstract. The application of a new particle collection system (PCS) developed in-house and operated on board a commercially available multicopter unmanned aerial vehicle (UAV) is presented as a new unmanned aerial system (UAS) approach for in situ measurement of the concentration of aerosol particles such as pollen grains and spores in the atmospheric boundary layer (ABL). A newly developed impactor is used for high-efficiency particle extraction on board the multicopter UAV. An airflow volume of 0.2 m3 min−1 through the impactor is provided by a battery-powered blower and measured with an on-board mass flow sensor. A bell-mouth-shaped air inlet of the PCS is arranged and oriented on the multicopter UAV to provide substantial isokinetic sampling conditions by advantageously using the airflow pattern generated by the propellers of the multicopter UAV. More than 30 aerosol particle collection flights were carried out near Tübingen in March 2017 at altitudes of up to 300 m above ground level (a.g.l.), each with a sampled air volume of 2 m3. Pollen grains and spores of various genera, as well as large (>20 µm) opaque particles and fine dust particles, were collected, and specific concentrations of up to 100 particles per m3 were determined by visual microscopic analysis. The pollen concentration values measured with the new UAS match well with the pollen concentration data published by the Stiftung Deutscher Polleninformationsdienst (PID) and by MeteoSwiss. A major advantage of the new multicopter-based UAS is the possibility of the identification of collected aerosol particles and the measurement of their concentration with high temporal and spatial resolutions, which can be used inter alia to improve the database for modelling the propagation of aerosol particles in the ABL.

Conjugate heat transfer simulation of turbine blade high efficiency cooling method with mist injection

2014 ◽  
Vol 228 (15) ◽  
pp. 2738-2749 ◽  
Author(s):  
Yuting Jiang ◽  
Qun Zheng ◽  
Guoqiang Yue ◽  
Ping Dong ◽  
Jie Gao ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Conjugate Heat Transfer ◽  
High Efficiency ◽  
Turbulence Models ◽  
Operating Conditions ◽  
Cooling Performance ◽  
Convective Cooling ◽  
Mist Cooling ◽  
The Impact

The idea of utilizing a finely dispersed water-in-air mixture has been proven to be a feasible technique to produce very high cooling rates. The accuracy of numerical simulation program for conjugate heat transfer methodology is verified with the Mark II transonic high pressure turbine stator which is cooled by internal convection through radial round pipes, and different turbulence models and transition models are employed to analyze the influence on results. On the basis of it, the mist cooling is simulated under typical gas turbine operating conditions for internal convective cooling to discuss the improvement of cooling performance. Though the results indicate that mist cooling can decrease the temperature of boundary layer without impact on the temperature of the mainstream and the thickness of boundary layer, the cooling capacity is limited by inadequate evaporation of mist. Considering the distribution of thermal stress and mist evaporation, a compound cooling blade of film cooling with trailing edge ejection is acquired which is modified from the blade of Mark II internal convective cooling; the effects of various parameters including mist concentration and mist diameter on the improvement of cooling performance are investigated, meanwhile the impact of curvature on cooling efficiency and mist trajectory is analyzed finally.

Design and Analysis of HP-Turbine for Variable Cycle Engine

2010 ◽  
Author(s):  
Zhi-gang Liu ◽  
Xiang-jun Fang ◽  
Si-yong Liu ◽  
Ping Wang ◽  
Zhao Yin
Keyword(s):  
Boundary Layer ◽  
Working Conditions ◽  
High Efficiency ◽  
Stokes Equations ◽  
Design Method ◽  
Thermodynamic Cycle ◽  
Tip Clearance ◽  
Transition Flow ◽  
Compressive Wave ◽  
Stream Surface

A supersonic highly loaded high-pressure turbine with large enthalpy drop was designed for a variable cycle Engine (VCE) in the conditions of both single and double bypass modes in accordance with the similarity principle in the paper. The blade profiles were designed by means of a three-dimensional (3D) profile design method based on S1 stream surface. Then, 3D numerical simulations were performed on the HP turbine of both working conditions with different thermodynamic cycle parameters to confirm the design methods and results. The one-equation turbulence model of Spalart-Allmaras was applied to solve Reynolds’s averaged Navier-Stokes equations and the transition model of Abu-Ghanam Shaw (AGS) was introduced to capture the development process of boundary layer on blade surfaces in the simulations. The results of simulations indicate that the turbine performances are satisfactory in both working conditions with high efficiency and the design targets being anticipated have been achieved. The method of design profiles based on S1 stream surface is more precise and effective than conventional cylinder method for turbine blade because the 3D characteristics of flow field are considered elaborately. Further research reveals wave structures in the supersonic turbine, behavior of tip clearance flow, the phenomenon of transition flow in boundary layer and the physical mechanism of strong compressive wave-boundary layer interactions.

A Review of Certain Inverse Methods for the Design of Ducts With 2- or 3-Dimensional Potential Flow

1988 ◽  
Vol 41 (6) ◽  
pp. 217-238 ◽  
Author(s):  
John D. Stanitz
Keyword(s):  
Boundary Layer ◽  
Flow Field ◽  
Three Dimensional ◽  
Inverse Methods ◽  
Design Methods ◽  
Two Dimensional ◽  
3 Dimensional ◽  
Fluid Handling ◽  
Layer Behavior ◽  
Flow Field Design

This article reviews the author’s work on inverse methods of flow-field design with prescribed velocity distributions on the boundaries. Such design methods are of some importance, because these velocity distributions, on the boundaries of fluid-handling equipment, determine the boundary-layer behavior and thereby affect the equipment efficiency. The work is limited to design methods for stationary channels with incompressible or subsonic compressible flow. Both two- and three-dimensional design methods are reviewed. The two-dimensional work was done in the early 1950’s and the three-dimensional work in the 1980’s.

Review of freeform TIR collimator design methods

2016 ◽  
Vol 5 (2) ◽  
Author(s):  
Taimoor Talpur ◽  
Alois Herkommer
Keyword(s):  
Total Internal Reflection ◽  
High Efficiency ◽  
Design Methods ◽  
Internal Reflection ◽  
Illumination Design ◽  
Feedback Method ◽  
Compact Geometry

AbstractTotal internal reflection (TIR) collimators are essential illumination components providing high efficiency and uniformity in a compact geometry. Various illumination design methods have been developed for designing such collimators, including tailoring methods, design via optimization, the mapping and feedback method, and the simultaneous multiple surface (SMS) method. This paper provides an overview of the different methods and compares the performance of the methods along with their advantages and their limitations.

A Pressure Gradient Sensitive Wall Function for the Prediction of Turbulent Flow in Thermal Turbomachinery

2005 ◽  
Author(s):  
Paul Pieringer ◽  
Wolfgang Sanz
Keyword(s):  
Boundary Layer ◽  
High Efficiency ◽  
Three Dimensional ◽  
Computational Time ◽  
Wall Function ◽  
Boundary Layer Flows ◽  
Fine Grid ◽  
Time Resolved ◽  
Wall Functions ◽  
Law Of The Wall

The economical design of thermal turbine stages of high efficiency requires very fast CFD tools of high accuracy. Since efficiency is mainly determined by secondary flow, a major focus in CFD is laid on boundary layer treatment. By resolving the boundary layer using a fine grid, usually the best results can be achieved, but at cost of computational time and memory. Wherever resolving the boundary layer is unacceptable, wall functions are used for simulating the flow close to solid walls. This paper describes a novel wall function approach for the prediction of three-dimensional turbulent boundary layer flows. The model is designed especially for the application to thermal turbomachinery in order to properly predict accelerated, decelerated and separated boundary layers at transonic conditions. The model is based on the law-of-the-wall expression by Spalding and also considers the shear-stress distribution perpendicular to the wall surface, which is mainly determined by pressure gradients. To cope with the boundary conditions, this wall function model uses phantom (ghost) cells, that must be located within the boundary layer, so there is a clearance between the first calculation cell and the wall. This allows an improved grid resolution for wall function approaches. To verify the accuracy of the model, results are shown for turbomachinery vane test cases at both steady state and time-resolved flow conditions.

scholarly journals Planetary boundary layer height by means of lidar and numerical simulations over New Delhi, India

2019 ◽  
Vol 12 (5) ◽  
pp. 2595-2610 ◽  
Author(s):  
Konstantina Nakoudi ◽  
Elina Giannakaki ◽  
Aggeliki Dandou ◽  
Maria Tombrou ◽  
Mika Komppula
Keyword(s):  
Boundary Layer ◽  
Planetary Boundary Layer ◽  
High Efficiency ◽  
Monsoon Season ◽  
Wrf Model ◽  
Satellite Observation ◽  
Weather Research And Forecasting ◽  
New Delhi ◽  
Boundary Layer Height ◽  
The Stability

Abstract. In this work, the height of the planetary boundary layer (PBLH) is investigated over Gwal Pahari (Gual Pahari), New Delhi, for almost a year. To this end, ground-based measurements from a multiwavelength Raman lidar were used. The modified wavelet covariance transform (WCT) method was utilized for PBLH retrievals. Results were compared to data from Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) and the Weather Research and Forecasting (WRF) model. In order to examine the difficulties of PBLH detection from lidar, we analyzed three cases of PBLH diurnal evolution under different meteorological and aerosol load conditions. In the presence of multiple aerosol layers, the employed algorithm exhibited high efficiency (r=0.9) in the attribution of PBLH, whereas weak aerosol gradients induced high variability in the PBLH. A sensitivity analysis corroborated the stability of the utilized methodology. The comparison with CALIPSO observations yielded satisfying results (r=0.8), with CALIPSO slightly overestimating the PBLH. Due to the relatively warmer and drier winter and, correspondingly, colder and rainier pre-monsoon season, the seasonal PBLH cycle during the measurement period was slightly weaker than the cycle expected from long-term climate records.

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