scholarly journals Mathematical Modelling Pressure Losses of Trapezoidal Labyrinth Channel at Low Inlet Pressure and Bi-Objective Optimization of the Design Parameters

2019 ◽  
Vol 8 (1) ◽  
Keyword(s):  
Mathematical Modelling ◽  
Inlet Pressure ◽  
Design Parameters ◽  
Pressure Losses ◽  
Labyrinth Channel

Correlation Between Pressure Recovery of Highly Loaded Annular Diffusers and Integral Stage Design Parameters

2017 ◽  
Author(s):  
Dajan Mimic ◽  
Bastian Drechsel ◽  
Florian Herbst
Keyword(s):  
Boundary Layer ◽  
Dynamic Pressure ◽  
Boundary Layer Separation ◽  
Flow Coefficient ◽  
Tip Vortex ◽  
Pressure Recovery ◽  
Design Parameters ◽  
Steam Turbines ◽  
Pressure Losses ◽  
Induced Velocity

Exhaust diffusers significantly enhance the available power output and efficiency of gas and steam turbines by allowing for lower turbine exit pressures. The residual dynamic pressure of the turbine outflow is converted into static pressure, which is referred to as pressure recovery. Since total pressure losses as well as construction costs increase drastically with diffuser length, it is more than favourable to design shorter diffusers with rather steep opening angles. However, those designs are more susceptible to boundary layer separation. In this paper, the stabilising properties of tip leakage vortices generated in the last rotor row and their effect on the boundary layer characteristics are examined. Based on analytical considerations, for the first time a correlation between the pressure recovery of the diffuser and integral rotor parameters of the last stage, namely the loading coefficient, flow coefficient and reduced frequency, is established. Both, experimental data and scale resolving simulations, carried out with the SST-SAS method, show excellent agreement with the correlation. Blade tip vortex strength predominantly depends on the amount of work performed in the rotor, which in turn is described by the non-dimensional loading coefficient. The flow coefficient influences mainly the orientation of the vortex, which affects the interaction between vortex and boundary layer. The induced velocity field accelerates the boundary layer, essentially reducing the thickness of the separated layer or even locally preventing separation.

Adjoint Based Aerodynamic Optimization of a Multi-Splitter Turbine Vane Frame

2019 ◽  
Author(s):  
Vincenzo Russo ◽  
Simone Orsenigo ◽  
Lasse Mueller ◽  
Tom Verstraete ◽  
Sergio Lavagnoli
Keyword(s):  
Total Pressure ◽  
Low Pressure ◽  
Design Parameters ◽  
Structural Constraints ◽  
Aerodynamic Optimization ◽  
Pressure Losses ◽  
Turbine Vane ◽  
Gradient Based ◽  
Adjoint Approach ◽  
Multi Body

Abstract This work presents a 2D optimization of a multi-body turbine vane frame (TVF), a particular configuration that can lead to considerable shortening of the aero-engine shaft as well as weight reduction. Traditionally, the turbine vane frame is used to guide the flow from the high pressure (HP) turbine to the low pressure (LP) turbine. Current designs have a mid turbine frame equipped with non lifting bodies that have structural and servicing functions, while multi-body configurations are characterized by the fact that, in order to shorten the duct length, the mid turbine struts are merged with the LP stator vanes, traditionally located downstream. This design architecture consists therefore of a multi-body vane row, where lifting long-chord struts replace some of the low pressure vane airfoils. However, the bulky struts cause significant aerodynamics losses and penalize the aerodynamics of the small vanes. The objective of the present work is to numerically optimize a TVF geometry with multi-body architecture using a gradient based algorithm coupled with the adjoint approach, enabling the use of a rich design space. Steady-state CFD simulations have been used to this end. The aim of this study is to reduce the total pressure losses of the TVF, while imposing several aerodynamic and structural constraints. The parametrization of the TVF geometry represents the airfoil shapes and their relative pitch-wise positions. The outcome of the optimization is to evaluate the potential improvements introduced by the optimized TVF geometry and to quantify the influence of the different design parameters on the total pressure losses.

Exergy Analysis of Carryover Leakage Irreversibilities of a Power Plant Regenerative Air Heater

2002 ◽  
Author(s):  
Rahim K. Jassim ◽  
Badr A. Habeebullah ◽  
Abdulraof S. Habeebullah
Keyword(s):  
Power Plant ◽  
Exergy Analysis ◽  
Process Efficiency ◽  
Design Parameters ◽  
Mixing Processes ◽  
Substantial Impact ◽  
Conservation Of Energy ◽  
Pressure Losses ◽  
Total Process ◽  
Chemical Exergy

Energy recovery devices can have substantial impact on process efficiency and their relevance to the problem of conservation of energy resources is generally recognised to be beyond dispute. One type of such a device, which is commonly used in fossil fired and air conditioning systems, is the rotary regenerator in which a stream of hot waste gas exchanges heat with fresh atmospheric air through the intermediate agency of a rotating matrix. As there are gas streams involved in the heat transfer and mixing processes, then there are irreversibilities, or exergy destruction, due to chemical reaction, pressure losses I˙ΔP and due to temperature gradients I˙ΔT . These principle components of total process irreversibility are not independent and there is a trade-off between them. Therefore the purpose of this research paper is to demonstrate the importance of the use of exergy analysis in the minimisation of carryover leakage irreversibilities of a symmetric balanced rotary regenerator. The chemical exergy E˙o and physical exergy E˙ph are calculated and the ratio of chemical and physical irreversibilities has been evaluated for a rotary regenerator used for air preheating in a coal-fired power plant. A numerical finite difference technique has been used to calculate the fluid and matrix temperature distributions effect on the regenerator performance. The effects of variation of the principal design parameters on the irreversibilities and on the regenerator effectiveness are examined and recommendations are made for the selection of the most appropriate parameters.

Transition Modelling for Vortex Generating Jets on Low-Pressure Turbine Profiles

2011 ◽  
Author(s):  
Florian Herbst ◽  
Dragan Kozˇulovic´ ◽  
Joerg R. Seume
Keyword(s):  
Total Pressure ◽  
Reynolds Numbers ◽  
Low Pressure ◽  
Quantitative Prediction ◽  
Design Parameters ◽  
Transition Model ◽  
Pressure Losses ◽  
Low Pressure Turbine ◽  
Wide Range ◽  
Local Transition

Steady blowing vortex generating jets (VGJ) on highly-loaded low-pressure turbine profiles have shown to be a promising way to decrease total pressure losses at low Reynolds-numbers by reducing laminar separation. In the present paper, the state of the art turbomachinery design code TRACE with RANS turbulence closure and coupled γ-ReΘ transition model is applied to the prediction of typical aerodynamic design parameters of various VGJ configurations in steady simulations. High-speed cascade wind tunnel experiments for a wide range of Reynolds-numbers, two VGJ positions, and three jet blowing ratios are used for validation. Since the original transition model overpredicts separation and losses at Re2is ≤ 100·103 an extra mode for VGJ induced transition is introduced. Whereas the criterion for transition is modelled by a filtered Q vortex criterion the transition development itself is modelled by a reduction of the local transition-onset momentum-thickness Reynolds number. The new model significantly improves the quality of the computational results by capturing the corresponding local transition process in a physically reasonable way. This is shown to yield an improved quantitative prediction of surface pressure distributions and total pressure losses.

Optimizing Effectiveness of Double Pipe Heat Exchanger Using Nanofluid and Different Porous Fins Arrangement

2021 ◽  
Author(s):  
Avinash Kumar ◽  
Vinay Arya ◽  
Chirodeep Bakli
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Design Parameters ◽  
Heat Transfer Characteristics ◽  
Pressure Losses ◽  
Porous Fin ◽  
Transfer Characteristics ◽  
Porous Fins ◽  
Double Pipe ◽  
Pipe Heat

Abstract A numerical study is carried out to investigate the effect of porous fins in counter-flow Double Pipe Heat Exchanger (DPHE). Four DPHE with different porous fin arrangements is simulated for varying Darcy number, fin height, and the number of fins and compared with the conventional DPHE with no porous fins. The Darcy-Brinkman-Forchheimer equation is employed to model the flow in the porous fins considering fixed Re = 100. Al2O3-H2O nanofluid and water are used as hot and cold fluids respectively. Stainless steel is used as porous material with a porosity of 0.65. Results are evaluated in terms of effectiveness and Performance Evaluation Criterion (PEC). The effectiveness of the heat exchanger is used to analyze the heat transfer characteristics whereas the PEC is used to analyze the heat transfer characteristics considering pressure losses also. We evaluated maximum enhancement in thermal performance using effectiveness analysis and through PEC study we evaluated optimal effectiveness and corresponding design parameters. It is shown that utilizing porous fins in DPHE enhances the heat transfer by 134.3%. However, along with enhancement in heat transfer, the pressure losses also enhance which makes the application of porous fin non-viable. Therefore, using the PEC study we obtained optimal design parameters (Da = 10−3, hf = 4 cm, and n = 30) which adapts porous fin viable with enhancement in heat transfer by 66.38%.

scholarly journals Effect of Relative Velocity Distribution on Efficiency and Exit Flow of Centrifugal Impellers

1983 ◽  
Author(s):  
H. Mishina ◽  
H. Nishida
Keyword(s):  
Total Pressure ◽  
Flow Behavior ◽  
Design Parameters ◽  
One Dimensional ◽  
Pressure Losses ◽  
Loss Analysis ◽  
High Stage ◽  
The Relationship ◽  
Stage Efficiency ◽  
Wide Operating

The major problem for designing centrifugal compressors is to attain high stage efficiency as well as a wide operating range. High stage efficiency is customarily attained by the optimization of design parameters using a one-dimensional loss analysis including the relationship between the flow behavior and total pressure losses for limited types of compressors.

scholarly journals Throughput of Customised ZigBee Stack- A Mathematical Modelling

2019 ◽  
Vol 8 (4) ◽  
pp. 5250-5255
Keyword(s):  
Mathematical Modelling ◽  
Resource Sharing ◽  
Research Work ◽  
Middle Layer ◽  
Design Parameters ◽  
Area Network ◽  
Protocol Stack ◽  
Zigbee Protocol ◽  
Internet Support ◽  
Wireless Communication Protocols

Research work is being done in the field of wireless communication protocols in order to find the desired applicability suitable to the end user. ZigBee protocol is chosen due to its reliable, long range and robust communication. In this direction there is need of designing a common communication protocol to realize a virtual control network by customizing the existing ZigBee protocol stack. It is also required to embed internet support protocols in different layers of the proposed stack so as to enable the entire network with internet connectivity. The proposed application aims at interoperating different devices under user personal area network, this fact has led to propose a new protocol stack with which every device of the network can be easily operated or controlled with enhanced network capabilities like resource sharing, additional middle layer for realising the proposed application using WPAN christened as ZigBee IP [ZI] stack. ZI stack is designed and the corresponding mathematical modelling is done in order to find better stack than ZigBee. This paper presents the design and modelling of throughput which is one of the important design parameters. Both the stacks viz., ZI and ZigBee are also compared w.r.t throughput

scholarly journals Computational Design Optimization for S-Ducts

Designs ◽  
2018 ◽  
Vol 2 (4) ◽  
pp. 36 ◽  
Author(s):  
Alessio D’Ambros ◽  
Timoleon Kipouros ◽  
Pavlos Zachos ◽  
Mark Savill ◽  
Ernesto Benini
Keyword(s):  
Design Space ◽  
Computational Design ◽  
Free Form ◽  
Design Parameters ◽  
Heuristic Optimization ◽  
Objective Functions ◽  
Pressure Losses ◽  
Optimization Study ◽  
Free Form Deformation ◽  
Computational Fluid Dynamics Cfd

In this work, we investigate the computational design of a typical S-Duct that is found in the literature. We model the design problem as a shape optimization study. The design parameters describe the 3D geometrical changes to the shape of the S-Duct and we assess the improvements to the aerodynamic behavior by considering two objective functions: the pressure losses and the swirl. The geometry management is controlled with the Free-Form Deformation (FFD) technique, the analysis of the flow is performed using steady-state computational fluid dynamics (CFD), and the exploration of the design space is achieved using the heuristic optimization algorithm Tabu Search (MOTS). The results reveal potential improvements by 14% with respect to the pressure losses and by 71% with respect to the swirl of the flow. These findings exceed by a large margin the optimality level that was achieved by other approaches in the literature. Further investigation of a range of optimum geometries is performed and reported with a detailed discussion.

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