Algorithm for Accumulating Part Mating Gaps to Evaluate Solid and Fluid Performances

2020 ◽  
Vol 143 (4) ◽  
Author(s):  
Jun Ni ◽  
Rui Liu ◽  
Yu Sun
Keyword(s):  
Aerodynamic Performance ◽  
Tolerance Limit ◽  
Centrifugal Fan ◽  
Physical Domain ◽  
General Applicability ◽  
Assembly Design ◽  
Assembly Sequences ◽  
Compact Expression ◽  
Working Performance ◽  
Isentropic Efficiency

Abstract Part mating gaps need to be effectively adjusted during the assembly of products and greatly affect the working performance. This paper develops an algorithm to calculate the dimensional and aerodynamic indexes affected by part mating gaps. Mating gaps are expressed by displacements of one contact surface, and indexes are evaluated by displacements of key surface, when the surface is ready to compare with the other. A graph that denotes contacts as nodes and related paths through the physical domain as lines is proposed to express assembly sequences and hierarchies. A variable is defined to combine the time set with the displacement set. Boolean algebraic theorems are extended to derive a compact expression for the contact graph that supports the organization of accumulations at different surfaces with propagations through physical domains. Demonstrations of this method using three products exhibit the general applicability, and the application shows that the performance deviations of the centrifugal fan and axial turbine are apparent. In particular, the isentropic efficiency is good with a certain probability, despite turbines having mating gaps. The algorithm benefits both design and assembly: design can be performed through the fluid domain, which is affected by the mating gaps, and when the parts are being adjusted, the selected tolerance limit allows engineers to monitor key surfaces to ensure good aerodynamic performance.

The Comparison of Aerodynamic Performance Data Acquired From Thermal Measurements and a Torquemeter on a Compressor Impeller

2018 ◽  
Vol 141 (4) ◽  
Author(s):  
Natalie R. Smith ◽  
Timothy C. Allison ◽  
Jason C. Wilkes ◽  
Christopher Clarke ◽  
Michael Cave
Keyword(s):  
Steady State ◽  
Heat Loss ◽  
Performance Metrics ◽  
Aerodynamic Performance ◽  
Performance Data ◽  
Testing Time ◽  
Southwest Research Institute ◽  
Significant Difference ◽  
Thermal Measurements ◽  
Isentropic Efficiency

Full-thermal heat-soak of machinery is vital for acquiring accurate aerodynamic performance data, but this process often requires significant testing time to allow all facility components to reach a steady-state temperature. Even still, there is the potential for heat loss in a well-insulated facility, and this can lead to inaccurate results. The implementation of a torquemeter to calculate performance metrics, such as isentropic efficiency, has two potential advantages: (1) the method is not susceptible to effects due to thermal heat loss in the facility, and (2) a torquemeter directly measures actual torque, and thus work, input, which eliminates the need to fully heat-soak to measure the actual enthalpy rise of the gas. This paper presents a comparison of aerodynamic performance metrics calculated both from data acquired with thermal measurements as well as from a torquemeter. These tests were conducted over five speedlines for a shrouded impeller in the Southwest Research Institute Single Stage Test Rig facility. Isentropic efficiency calculated from the torquemeter was approximately 1–2 efficiency points lower than the isentropic efficiency based on thermal measurements. This corresponds to approximately 0.5–1 °C in heat loss in the discharge collector and piping. Furthermore, observations from three full-thermal heat-soak points indicate the significant difference in time required to reach steady-state performance within measurement uncertainty tolerances between the torque-based and thermal-based methods. This comparison, while largely suspected, has not yet been studied in previous publications.

The Comparison of Aerodynamic Performance Data Acquired From Thermal Measurements and a Torquemeter on a Compressor Impeller

2018 ◽  
Author(s):  
Natalie R. Smith ◽  
Christopher Clarke ◽  
Timothy C. Allison ◽  
Michael Cave ◽  
Jason C. Wilkes
Keyword(s):  
Steady State ◽  
Heat Loss ◽  
Performance Metrics ◽  
Aerodynamic Performance ◽  
Performance Data ◽  
Testing Time ◽  
Southwest Research Institute ◽  
Significant Difference ◽  
Thermal Measurements ◽  
Isentropic Efficiency

Full-thermal heat-soak of machinery is vital to acquiring accurate aerodynamic performance data, but this process often requires significant testing time to allow for all facility components to reach a steady state temperature. Even still, there is the potential for heat loss in a well-insulated facility, and this can lead to inaccurate results. The implementation of a torquemeter to calculate performance metrics, such as isentropic efficiency, has two potential advantages: 1) the method is not susceptible to effects due to thermal heat loss in the facility, and 2) a torquemeter directly measures actual torque, and thus work, input, which eliminates the need to fully heat-soak to measure the actual enthalpy rise of the gas. This paper presents a comparison of aerodynamic performance metrics calculated both from data acquired with thermal measurements as well as from a torquemeter. These tests were conducted over five speedlines for a shrouded impeller in the Southwest Research Institute Single Stage Test Rig facility. Isentropic efficiency calculated from the torquemeter was approximately 1–2 efficiency points lower than the isentropic efficiency based on thermal measurements. This corresponds to approximately 0.5–1°C in heat loss in the discharge collector and piping. Furthermore, observations from three full-thermal heat-soak points indicate the significant difference in time required to reach steady state performance within measurement uncertainty tolerances between the torque-based and thermal-based methods. This comparison, while largely suspected, has not yet been studied in previous publications.

scholarly journals A Numerical Study of Aerodynamic Performance and Noise of a Bionic Airfoil Based on Owl Wing

2014 ◽  
Vol 6 ◽  
pp. 859308 ◽  
Author(s):  
Xiaomin Liu ◽  
Xiang Liu
Keyword(s):  
Reynolds Number ◽  
Unsteady Flow ◽  
Noise Reduction ◽  
Numerical Study ◽  
Aerodynamic Performance ◽  
Centrifugal Fan ◽  
Surface Geometry ◽  
Airfoil Surface ◽  
Acoustic Sources ◽  
Bionic Airfoil

Noise reduction and efficiency enhancement are the two important directions in the development of the multiblade centrifugal fan. In this study, we attempt to develop a bionic airfoil based on the owl wing and investigate its aerodynamic performance and noise-reduction mechanism at the relatively low Reynolds number. Firstly, according to the geometric characteristics of the owl wing, a bionic airfoil is constructed as the object of study at Reynolds number of 12,300. Secondly, the large eddy simulation (LES) with the Smagorinsky model is adopted to numerically simulate the unsteady flow fields around the bionic airfoil and the standard NACA0006 airfoil. And then, the acoustic sources are extracted from the unsteady flow field data, and the Ffowcs Williams-Hawkings (FW-H) equation based on Lighthill's acoustic theory is solved to predict the propagation of these acoustic sources. The numerical results show that the lift-to-drag ratio of bionic airfoil is higher than that of the traditional NACA 0006 airfoil because of its deeply concave lower surface geometry. Finally, the sound field of the bionic airfoil is analyzed in detail. The distribution of the A-weighted sound pressure levels, the scaled directivity of the sound, and the distribution of dP/dt on the airfoil surface are provided so that the characteristics of the acoustic sources could be revealed.

The Datum Flow Chain: A Systematic Approach to Assembly Design and Modeling

1998 ◽  
Author(s):  
R. Mantripragada ◽  
D. E. Whitney
Keyword(s):  
Design Process ◽  
Systematic Approach ◽  
Assembly Planning ◽  
Assembly Process ◽  
Top Down ◽  
Assembly Design ◽  
Key Characteristics ◽  
Assembly Sequences

Abstract In order to be able to lay out, analyze, outsource, assemble, and debug complex assemblies, we need ways to capture their fundamental structure in a top-down design process, including the designer’s strategy for kinematically constraining and locating the parts accurately with respect to each other. We describe a concept called the “Datum Flow Chain” to capture this logic. The DFC relates the datum logic explicitly to the product’s key characteristics, assembly sequences, and choice of mating features, and provides the information needed for tolerance analyses. Two types of assemblies are addressed: Type-1 where the assembly process puts parts together at their prefabricated mating features, and Type-2 where the assembly process can incorporate in-process adjustments to redistribute variation. Two types of assembly joints are defined: mates that pass dimensional constraint from part to part, and contacts that merely provide support. The scope of DFC in assembly planning is presented using several examples. Analysis tools to evaluate different DFCs and select the ones of interest are also presented.

scholarly journals Air sampling by pumping through a filter: effects of air flow rate, concentration, and decay of airborne substances

2016 ◽  
Vol 67 (4) ◽  
pp. 326-331
Author(s):  
Marko Šoštarić ◽  
Branko Petrinec ◽  
Dinko Babić
Keyword(s):  
Time Dependence ◽  
Flow Rate ◽  
Particle Concentration ◽  
Air Flow ◽  
Airborne Particles ◽  
Air Flow Rate ◽  
General Applicability ◽  
Compact Expression ◽  
Filter Effects ◽  
Over Time

Abstract This paper tackles the issue of interpreting the number of airborne particles adsorbed on a filter through which a certain volume of sampled air has been pumped. This number is equal to the product of the pumped volume and particle concentration in air, but only if the concentration is constant over time and if there is no substance decomposition on the filter during sampling. If this is not the case, one must take into account the inconstancy of the concentration and the decay law for a given substance, which is complicated even further if the flow rate through the filter is not constant. In this paper, we develop a formalism which considers all of these factors, resulting in a single, compact expression of general applicability. The use of this expression is exemplified by addressing a case of sampling airborne radioactive matter, where the decay law is already well known. This law is combined with three experimentally observed time dependence of the flow rate and two models for the time dependence of the particle concentration. We also discuss the implications of these calculations for certain other situations of interest to environmental studies.

Effects of Labyrinth Fin Wear on Aerodynamic Performance of Turbine Stages: Part II — Mushrooming Damages

2019 ◽  
Author(s):  
Xinbo Dai ◽  
Xin Yan
Keyword(s):  
Experimental Studies ◽  
Axial Direction ◽  
Labyrinth Seal ◽  
Aerodynamic Performance ◽  
Leakage Rate ◽  
Secondary Flows ◽  
Main Function ◽  
Aerodynamic Loss ◽  
Solution Methods ◽  
Isentropic Efficiency

Abstract The main function of labyrinth seal is to control leakage flow in clearance that involves with rotating and stationary parts. Therefore, the effective of clearance gap in labyrinth seal is critical to sealing, heat transfer and vibration characteristics. However, due to the mechanical expansions, vibrations, thermal stress, misalignment of seal components in transient periods of startup, shutdown and hot restart, the stationary and rotating parts of the labyrinth seal are likely to contact each other, causing wear damages in labyrinth fin. Mushrooming damages are often occurred in the rubbing events when labyrinth fin is made of soft material compared with the opposite component. To investigate how mushrooming damage affects the leakage performance of labyrinth seal, many numerical and experimental studies have been carried out in last decades. However, little attention has been paid on the influence of labyrinth fin mushrooming on aerodynamic performance of turbine stages. In this study, using the RANS equations solution methods, the effect of labyrinth fin mushrooming on isentropic efficiency, leakage rates, outlet flow angles, reaction degrees, profile static pressure distributions and flow fields in turbine stages were investigated at three different mushrooming radii and three effective clearances. It shows the leakage rate is increased with increasing the mushroom radius and effective clearance. At the same effective clearance, as the mushrooming radius increases from 0.2mm to 0.4mm, the leakage rate is increased by about 0.19–0.32%, and the overall isentropic efficiency is decreased by 0.78%. At the same mushrooming radius, as the effective clearance increases from 1mm to 1.4mm, the leakage rate is increased by 0.21–0.31%, and the overall isentropic efficiency is decreased by 0.65%. As mushroom radius and effective clearance increase, the secondary flows near hub and shroud are intensified and developed along axial direction, causing pronounced aerodynamic loss in turbine stages.

Effects of Labyrinth Fin Wear on Aerodynamic Performance of Turbine Stages: Part I — Bending Damages

2019 ◽  
Author(s):  
Xin Yan ◽  
Xinbo Dai
Keyword(s):  
Labyrinth Seal ◽  
Flow Fields ◽  
Aerodynamic Performance ◽  
Leakage Flow ◽  
Original Design ◽  
Labyrinth Seals ◽  
Sealing Performance ◽  
Forward Bending ◽  
Design Case ◽  
Isentropic Efficiency

Abstract Labyrinth seals are widely applied in turbo machines because of their geometrical simplicity, convenient installation, reliable operation and excellent sealing performance. However, in realistic operation process, they usually encounter transient conditions (starting-up, shutting down, etc.) and unavoidable vibrations, which may cause wear in the labyrinth fins. After rubbing, the sealing performance of labyrinth seal will be varied in contrast to the original design. Correspondingly, the aerodynamic efficiency of the turbine stage will be affected by the variation of leakage flow in rubbing process. However, in published literature with respect to the labyrinth seal wear, most of the attention has been paid on revealing sealing performance degradation of labyrinth seal itself. Few studies have been concentrated on the influence of labyrinth seal wear on aerodynamic performance of turbine stages. In such background, the present paper utilizes the numerical methods to investigate the effects of labyrinth seal bending damages on aerodynamic performance of turbine stages. Firstly, under several assumptions, the bending geometrical model was established to describe different degrees of bending damages. Secondly, using three-dimensional RANS simulations, the effects of effective clearance variation due to bending on leakage flow and flow fields in turbine stages were investigated. The overall performance of the turbine stages with teeth-bending damages was also compared with the original design case. The influence of the forward bending and backward bending of labyrinth seals were analyzed and compared with each other. The total-total isentropic efficiency of turbine stages, leakage rates, outlet flow angles, reaction degrees and profile static pressure distributions, entropic distributions and flow fields in seals were obtained and compared to the original design case. The results indicate that the leakage rates in the worn labyrinth seal are quite relevant to the effective clearance, especially for the backward bending damages. As the effective clearances in backward bending cases are increased by 0.2–0.6mm, the isentropic efficiency of turbine stages is decreased by about 1–2%. However, for the forward bending damages, the aerodynamic performance and leakage rates in turbine stages are not sensitive to the effective clearance.

scholarly journals Decomposition-Based Assembly Synthesis for In-Process Dimensional Adjustability

2002 ◽  
Author(s):  
Byungwoo Lee ◽  
Kazuhiro Saitou
Keyword(s):  
Design Process ◽  
Early Stage ◽  
Product Configuration ◽  
Two Dimensional ◽  
Design Phase ◽  
Assembly Design ◽  
Component Design ◽  
Assembly Sequences ◽  
Simple Rules ◽  
Final Design

This paper presents a method of assembly synthesis focused on the in-process adjustability, where assembly synthesis is defined as the decomposition of the end product design prior to the detailed component design phase. Focusing on the effect of joint configurations on dimensional integrity of complex assemblies, the method recursively decomposes a product configuration and assigns joint configurations according to simple rules, in order to achieve a designed dimensional adjustability and non-forced fit. The rules employed during the decomposition process are drawn from the previous works of assembly design. An augmented AND/OR graph is utilized to represent a process of assembly synthesis with the corresponding assembly sequences, and the algorithm for generating the AND/OR graph is discussed. The method is applied to two dimensional skeletons of product designs at very early stage of the design process. The relation of the assembly synthesis to Datum Flow Chain (Mantripragada and Whitney, 1998) is discussed. It is also shown that each final design from the assembly synthesis defines its own Datum Flow Chain.

scholarly journals Decomposition-Based Assembly Synthesis for In-Process Dimensional Adjustability

2003 ◽  
Vol 125 (3) ◽  
pp. 464-473 ◽  
Author(s):  
Byungwoo Lee ◽  
Kazuhiro Saitou
Keyword(s):  
Design Process ◽  
Early Stage ◽  
Product Configuration ◽  
Two Dimensional ◽  
Design Phase ◽  
Assembly Design ◽  
Component Design ◽  
Assembly Sequences ◽  
Simple Rules ◽  
Final Design

This paper presents a method of assembly synthesis focused on the in-process adjustability, where assembly synthesis is defined as the decomposition of the end product design prior to the detailed component design phase. Focusing on the effect of joint configurations on dimensional integrity of complex assemblies, the method recursively decomposes a product configuration and assigns joint configurations according to simple rules, in order to achieve a designed dimensional adjustability and non-forced fit. The rules employed during the decomposition process are drawn from the previous works of assembly design. An augmented AND/OR graph is utilized to represent a process of assembly synthesis with the corresponding assembly sequences, and the algorithm for generating the AND/OR graph is discussed. The method is applied to two dimensional skeletons of products without moving parts at very early stage of the design process. The relation of the assembly synthesis to Datum Flow Chain [1] is discussed. It is also shown that each final design from the assembly synthesis defines its own Datum Flow Chain.

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