Influence of the Sweep Stacking on the Performance of an Axial Fan

2015 ◽  
Vol 137 (6) ◽  
Author(s):  
Ayhan Nazmi Ilikan ◽  
Erkan Ayder
Keyword(s):  
Pressure Rise ◽  
Secondary Flows ◽  
Axial Fan ◽  
Negative Effects ◽  
Blade Loading ◽  
Stall Margin ◽  
Negative Effect ◽  
Aerodynamic Parameters ◽  
Overall Performance ◽  
Positive Effect

In modern turbomachinery blade design, nonradial stacking of the profiles is often assumed to be one of the ways to improve the performance of a machine. Instead of stacking the profiles radially, the stacking line is changed by several modifications such as sweep, dihedral, lean, or a combination of these. Nonradial stacking influences secondary flows that have effects on the aerodynamic parameters such as efficiency, pressure rise, blade loading, and stall margin. However, many of the studies in literature are limited by the comparison of two or three cases. This situation leads to conflicting results because a modification may cause a positive effect in one study while in another one, the same modification may have a negative effect. In this study, a modified free vortex axial fan (named as base fan (BF) for this study) is designed first and the profiles of the blades are stacked radially by joining the centroids of the profiles. Second, 45 deg, 30 deg forward sweep (FS) and backward sweep (BS) modifications are applied. The effects of these modifications on aerodynamic performance of the fans are investigated by means of numerical calculations. The results show that FS and BS do not significantly affect the overall performance of the fan at the design flowrate in spite of the occurring modifications of the local blade pressure distribution. However, at low flowrates, FS and BS have positive and negative effects on the fan performance, respectively.

Effect of Axial Sweep and Tip Extension on Performance of an Axial Fan

2016 ◽  
Author(s):  
Ankit Bhai Patel ◽  
K. Viswanath ◽  
Dhyanjyoti Deb Nath
Keyword(s):  
Performance Improvement ◽  
Flow Direction ◽  
Pressure Rise ◽  
Aerodynamic Performance ◽  
Secondary Flows ◽  
Tip Vortex ◽  
Low Flow ◽  
Pressure Probe ◽  
Axial Fan ◽  
Stall Margin

Performance enhancement in terms of stall margin increment, increased pressure rise coefficient and increased efficiency is of great need for low speed axial fans. Stacking line modifications in terms of sweep, skew, dihedral or combination of these, as well as blade tip geometry modifications are assumed to be one of the ways to achieve finite performance improvement. Non radial stacking of blade profiles modifies secondary flows, tip vortex effects, hub passage vortex and thus affects aerodynamic performance parameters such as stall margin, efficiency, pressure rise, blade loading. In literature many studies have confined to comparison of few cases which led to conflicting results as modification of stacking line may have different effects in different cases. In the present work, comparison of performance of axial fan rotor with three different blade configurations BSL (baseline), SWP (swept blade) and EXTN (swept blade with extended tip) are considered. The BSL configuration is designed on basis of non-free vortex design. The SWP configuration is obtained by shifting radial stacking line of the BSL in axial flow direction by 10° (Forward sweep). The EXTN configuration is obtained by extending tip profile on pressure surface as well as suction surface by 3% locally. Experiments have been conducted on these three configurations to study effects of these modifications on aerodynamic performance. The flow field has been surveyed using Kiel probe, Three hole pressure probe at many flow rates starting from fully open to fully closed. Unsteady flow analysis at exit of rotors of all configurations is carried out using fast response pressure probe. Experimental results show slight performance improvement in terms of increased stall margin, efficiency, as well as total pressure rise for SWP rotor as well as EXTN rotor compared to BSL rotor at low flow coefficients.

scholarly journals Lagged Effect of Macroeconomic Variables on Stock Returns: A Case of Firm Size

2021 ◽  
Vol 19 (1) ◽  
Keyword(s):  
Stock Returns ◽  
Firm Size ◽  
Small Firms ◽  
Size Group ◽  
Negative Effects ◽  
Macroeconomic Factors ◽  
Large Size ◽  
Negative Effect ◽  
Positive Effect ◽  
Lagged Effect

The evidence of lagged effect regarding firm size between macroeconomic factors and stock returns is found with GARCH model for the UAE firms. More precisely, exchange rate showed a significant effect on stock returns irrespective of size group and lag level. However, a positive effect is observed at lag four and a negative effect is observed on lag five and two for small and large size firms respectively. For majority of the firms in small size, the risk-free rate showed a negative lagged effect on stock returns; however, for the majority of the firms in large size, it showed a positive lagged effect on stock returns. Inflation also showed a significant effect on stock returns on each lag level except for large firms where at lag five it is insignificant. Moreover, as the lags increase from 1- 4 and size from small to large, the negative effect of inflation converts to positive effect on stock returns. The lag effect of real activity showed both positive and negative effects on relatively larger stock returns of small firms than big firms. Money supply showed positive significant effect on stock returns of all firms irrespective of the size group; however, this relationship is even more prominent at lag five. Finally, the oil prices showed a positive effect on stock returns (large size) which further maximizes at lag two; whereas, a negative maximization takes place at lag three. Hence, investors can make informed and effective decisions and UAE policymakers developed effective measures to control and promote macroeconomic growth and stability.

scholarly journals People’s attitudes towards deadwood in forest: evidence from the Ukrainian Carpathians

2019 ◽  
Vol 65 (No. 5) ◽  
pp. 171-182 ◽  
Author(s):  
Oksana Pelyukh ◽  
Alessandro Paletto ◽  
Lyudmyla Zahvoyska
Keyword(s):  
Local Community ◽  
Sustainable Forest Management ◽  
Managed Forests ◽  
Negative Effects ◽  
Face To Face ◽  
The Face ◽  
Negative Effect ◽  
Intensively Managed ◽  
People’S Attitudes ◽  
Positive Effect

People’s attitudes towards forest stand characteristics including deadwood are becoming increasingly relevant in sustainable forest management. The aim of this study is to investigate people’s attitudes towards deadwood in forest. The study was carried out in the Rakhiv region (Ukraine) characterized by high importance of forest resources for the local community and economy. People’s opinions were collected through the face-to-face administration of a questionnaire to 308 respondents. The survey investigated three aspects: importance of deadwood in forest; people’s perceptions of positive and negative effects of deadwood in forest; effects of presence and amount of deadwood in different types of forest on people’s aesthetical preferences. The results show that the majority of respondents consider deadwood as an important component of the forest, but generally they prefer intensively managed forests without deadwood. According to the respondents’ opinions, the most important positive effect of deadwood is a contribution to stand dynamics, while the most important negative effect is an increasing risk of insects and diseases.

scholarly journals Recessed Casing Treatment Effects on Fan Performance and Flow Field

1995 ◽  
Author(s):  
C. S. Kang ◽  
A. B. McKenzie ◽  
R. L. Elder
Keyword(s):  
Flow Field ◽  
Axial Flow ◽  
Pressure Rise ◽  
Operating Efficiency ◽  
Flow Measurements ◽  
Blade Loading ◽  
Stall Margin ◽  
Casing Treatment ◽  
Stall Margin Improvement ◽  
Blade Tip

An experimental investigation to examine the influence of the vaned recess casing treatment on stall margin, operating efficiency and the flow field of a low speed axial flow fan with aerospace type blade loading is presented. Different geometrical designs of the vaned passages were examined. The best configuration resulted in a stall margin improvement of 67%, a significantly higher pressure rise in the stall region and insignificant change in peak efficiency. Detailed 3-D flow measurements in the endwall region and in the casing recess were carried out with a slanted hot-wire, providing some insight to the operation of the device. The results revealed that the stall margin improvement was largely due to the removal of flow from the blade tip to the recess, and the elimination of the growth of the stall region at the tip, which occurs at stall in the solid casing build.

A time-lagged study on the moderating role of overall satisfaction in perceived politics: Job outcomes relationships

2016 ◽  
Vol 23 (3) ◽  
pp. 321-336 ◽  
Author(s):  
Farooq Ahmed Jam ◽  
Magda B L Donia ◽  
Usman Raja ◽  
Chong Hui Ling
Keyword(s):  
Job Performance ◽  
Job Stress ◽  
Interpersonal Conflict ◽  
High Stress ◽  
Interactive Effects ◽  
Negative Effects ◽  
Negative Effect ◽  
Time Lagged ◽  
Positive Effect ◽  
High Politics

AbstractIn a time-lagged study with independent measures (N=115, paired responses), we examined the interactive effects of perceived organizational politics and overall satisfaction on job stress, interpersonal conflict, job performance, and creativity. The data were collected from a diverse sample of employees from various workplaces in Pakistan. The findings showed that perceived politics had a positive effect on job stress, while overall satisfaction had a negative effect on interpersonal conflict and a positive effect on creative performance. The results also revealed that in the face of high politics, highly satisfied individuals demonstrated higher levels of creativity and job performance. However, in this context of high politics negative effects were also observed, namely that highly satisfied individuals participated in interpersonal conflict and experienced high stress.

scholarly journals Optimizing the seismic effects of blasting in quarries by timing

2019 ◽  
pp. 48-62
Author(s):  
Ján Baulovič ◽  
Blažej Pandula ◽  
Julián Kondela ◽  
Marta Prekopová
Keyword(s):  
Natural Environment ◽  
Technical Problem ◽  
The Other ◽  
Negative Effects ◽  
Seismic Effects ◽  
Seismic Safety ◽  
Blasting Operation ◽  
Negative Effect ◽  
The Impact ◽  
Positive Effect

Recently, negative effects of the blasting operations and quantification of the seismic safety are regarded as very important technical problem in quarries. The impact of blasting operations is accompanied by both positive and negative seismic effects. For example, vibrations generated by explosion create very positive effect − when help to break the rocks, but, on the other hand, also result in negative effect − when affect constructions and natural environment in the vicinity of a blasting works site. If the vibrations are large enough, then the nearby objects could be damaged or destroyed. This article highlights the results of the blasting operation monitoring in limestone Lopušné Pažite quarry on Slovakia, which based on the rule that the negative effects depend on their range and strength. This method is applied in all quarries in Slovakia, which are close to settlements.

scholarly journals Designing for Packaging Sustainability. The Effects of Appearance and a Better Eco-Label on Consumers’ Evaluations and Choice

2019 ◽  
Vol 1 (1) ◽  
pp. 3251-3260 ◽  
Author(s):  
Sophie Krah ◽  
Tea Todorovic ◽  
Lise Magnier
Keyword(s):  
Negative Impact ◽  
Traffic Light ◽  
Negative Effects ◽  
User Perspective ◽  
Policy Makers ◽  
Negative Effect ◽  
Typical Appearance ◽  
Perceived Usability ◽  
Choice Intentions ◽  
Positive Effect

AbstractThe environmental burden of packaging is huge. However, redesigning packaging to make it more sustainable without damaging its other functions is not always easy and can have a negative impact on consumers’ choice. In this paper, we adopt a user-perspective and test the effects of packaging appearance and a better eco-label on consumers’ responses. Based on the literature, we designed an eco- label using a traffic light system with an objective sustainability score enabling to compare the sustainability of different packages. The results of our experimental study (N=120) show that while a sustainable (vs. typical) appearance in packaging has a positive effect on perceived sustainability, it has a negative effect on perceived usability. However, we demonstrate that the presence of a high score on the eco-label positively impacts the perceived sustainability of both the sustainable and the typical packages and the choice intentions. This eco-label also enabled to mitigate the negative effects of the sustainable appearance on perceived usability. Designers and policy-makers can use the results of this paper to positively influence evaluations of and choice for sustainable packaging.

The effects of the antecedents of service purchase intention in the context of monetary sales promotion

2014 ◽  
Vol 64 (Supplement-2) ◽  
pp. 177-197
Author(s):  
Cheng-Chen Chiang
Keyword(s):  
Perceived Risk ◽  
Purchase Intention ◽  
Positive Impact ◽  
Perceived Value ◽  
Perceived Quality ◽  
Sales Promotion ◽  
Negative Effects ◽  
Perceived Price ◽  
Negative Effect ◽  
Positive Effect

This study investigated the correlations among variables for credence service in the context of monetary sales promotion. The findings suggested that perceived price directly affected perceived quality, with a negative effect. Perceived price had a positive effect directly on perceived value. Perceived quality directly affected perceived value. Perceived value was found as a key predictor of purchase intention. In addition, perceived quality had indirect and positive impact on purchase intention via value. The results of this study also suggested that there was a negative effect of perceived price on perceived risk. Moreover, it was also noted that perceived risk had negative effects on perceived value and purchase intention.

Understanding the Flow Behavior in a Low Hub-Tip Ratio, High Aspect Ratio Contra-Rotating Axial Fan Stage

2012 ◽  
Author(s):  
Chetan S. Mistry ◽  
A. M. Pradeep
Keyword(s):  
Aspect Ratio ◽  
Total Pressure ◽  
Numerical Study ◽  
Flow Behavior ◽  
Experimental Studies ◽  
Pressure Rise ◽  
Operating Conditions ◽  
Speed Ratio ◽  
Axial Fan ◽  
Stall Margin

This paper discusses the results of a parametric study of a pair of contra-rotating axial fan rotors. The rotors were designed to deliver a mass flow of 6 kg/s at 2400 rpm. The blades were designed with a low hub-tip ratio of 0.35 and an aspect ratio of 3.0. Numerical and experimental studies were carried out on these contra-rotating rotors operating at a Reynolds number of 1.25 × 105 (based on blade chord). The axial spacing between the rotors was varied between 50 to 120 % of the chord of rotor 1. The performance of the rotors was evaluated at each of these spacing at design and off-design speeds. The results from the numerical study (using ANSYS CFX) were validated using experimental data. In spite of certain limitations of CFD under certain operating conditions, it was observed that the results agreed well with those from the experiments. The performance of the fan was evaluated based on the variations of total pressure, velocity components and flow angles at design and off-design operating conditions. The measurement of total pressure, flow angles etc. are taken upstream of the first rotor, between the two rotors and downstream of the second rotor. It was observed that the aerodynamics of the flow through a contra rotating stage is significantly influenced by the axial spacing between the rotors and the speed ratio of the rotors. With increasing speed ratios, the strong suction generated by the second rotor, improves the stage pressure rise and the stall margin. Lower axial spacing on the other hand, changes the flow incidence to the second rotor and thereby improves the overall performance of the stage. The performance is investigated at different speed ratios of the rotors at varying axial spacing.

Positive and negative effects of allochthonous dissolved organic matter and inorganic nutrients on phytoplankton growth

2002 ◽  
Vol 59 (1) ◽  
pp. 85-95 ◽  
Author(s):  
Jennifer L Klug
Keyword(s):  
Organic Matter ◽  
Dissolved Organic Matter ◽  
Phytoplankton Community ◽  
Phytoplankton Growth ◽  
Inorganic Nutrients ◽  
Physiological Status ◽  
Negative Effects ◽  
Positive Effects ◽  
Negative Effect ◽  
Positive Effect

Dissolved organic matter (DOM) can have both positive and negative effects on phytoplankton growth. The magnitude of these effects may vary depending on the source of DOM and the composition of the phytoplankton community. Here, I address the relative importance of the positive and negative effects of DOM extracts on phytoplankton growth. In short-term experiments with phytoplankton from West Long Lake, a small, moderately coloured lake in northern Michigan, U.S.A., the net effect of doubling ambient DOM on phytoplankton growth was positive. Increasing DOM concentrations from ~10 mg C·L–1 to ~20 mg C·L–1 had a negative effect on total phytoplankton growth by reducing irradiance and thus reducing the depth to which growth was positive. However, inorganic nutrients in the DOM extracts increased growth at each irradiance level. The positive effect on phytoplankton growth owing to the nutrients associated with DOM was greater than the negative effect caused by shading. Although the positive effects of allochthonous DOM inputs outweighed the negative effects for the nutrient-limited phytoplankton in these experiments, the net effect depends on the concentration and availability of nutrients associated with allochthonous DOM as well as the physiological status of the phytoplankton community.

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