The Impact of Hole Depth on the Rotordynamic and Leakage Characteristics of Hole-Pattern-Stator Gas Annular Seals

2013 ◽  
Vol 136 (4) ◽  
Author(s):  
Dara W. Childs ◽  
Stephen Arthur ◽  
Naitik J. Mehta
Keyword(s):  
Performance Improvement ◽  
Test Data ◽  
Hole Diameter ◽  
Test Results ◽  
Running Speed ◽  
Hole Depth ◽  
Test Variable ◽  
Leakage Characteristics ◽  
Gas Seals ◽  
The Impact

Test results are presented for rotordynamic characteristics of hole-pattern-stator annular gas seals at a 70 bar supply pressures with a running speed of 20,200 rpm. Leakage results are presented for these conditions and the additional speeds: 10,200 and 15,300 rpm. Hole-depth is the principal test variable of interest. Most published annular test data for these seals have a hole diameter of 3.175 mm and a hole depth of 3.302 mm. For this work, with the 3.175 mm hole diameter, additional results are presented for shallow (1.905 mm) and deep (6.604 mm) hole depths. Test results show a pronounced dependence of leakage and rotordynamic behavior on hole depth. Test results show much better leakage performance for the shallow-hole-depth seal in both leakage and rotordynamic performance. Compressor manufacturers and users will need to decide whether this observed performance improvement is worth trying in real machines.

The Impact of Hole Depth on the Rotordynamic and Leakage Characteristics of Hole-Pattern-Stator Gas Annular Seals

2013 ◽  
Author(s):  
Dara W. Childs ◽  
Stephen Arthur ◽  
Naitik J. Mehta
Keyword(s):  
Performance Improvement ◽  
Test Data ◽  
Hole Diameter ◽  
Test Results ◽  
Hole Depth ◽  
Test Variable ◽  
Leakage Characteristics ◽  
Gas Seals ◽  
The Impact ◽  
Annular Seals

Test results are presented for rotordynamic characteristics of hole-pattern-stator annular gas seals at a 70 bar supply pressures running at 20200 rpm. Leakage results are presented for these conditions and the additional speeds: 10200, 15300 rpm. Hole-depth is the principal test variable of interest. Most published annular test data for these seals have a hole diameter of 3.175mm and a hole depth of 3.302mm. For this work, with the 3.175mm hole diameter, additional results are presented for shallow (1.905 mm) and deep (6.604 mm) hole depths. Test results show a pronounced dependence of leakage and rotordynamic behavior on hole depth. Test results show much better leakage performance for the shallow-hole-depth seal in both leakage and rotordynamic performance. Compressor manufacturers and users will need to decide whether this observed performance improvement is worth trying in real machines.

A Design to Improve the Effective Damping Characteristics of Hole-Pattern-Stator Annular Gas Seals

2006 ◽  
Author(s):  
Dara W. Childs ◽  
Yoon-Shik Shin ◽  
Brent Seifert
Keyword(s):  
Friction Factor ◽  
Flow Path ◽  
Test Results ◽  
Static Stiffness ◽  
Hole Depth ◽  
Negative Test ◽  
Damping Characteristics ◽  
Jump Phenomena ◽  
The Cross ◽  
Gas Seals

Predictions are presented for hole pattern seals for which the hole depth is varied axially, showing that various depth patterns can significantly improve damping performance in terms of both increasing the seal’s effective damping and reducing its cross-over frequency — the frequency at which effective damping changes from positive to negative. Test results are presented for the seal with the best variable hole depth (VHD) pattern showing an increase in peak damping by a factor of 1.6 over a constant hole depth (CHD) design, versus predictions of 2.7. The cross over frequency is reduced by approximately 40%. The VHD seal has a significant negative static stiffness that probably arises from a friction-factor jump phenomena, not flow path divergence. The VHD seal leaks less than a comparable CHD design.

The Impact Study of the Resistance to Ultraviolet Radiation Aging Agent on the Airport Road Surface Performance with the Modified Asphalt

2013 ◽  
Vol 723 ◽  
pp. 1068-1075 ◽  
Author(s):  
Song Ye ◽  
Xian Zhi Shao ◽  
Lie Ping Wang
Keyword(s):  
Performance Improvement ◽  
Negative Influence ◽  
Test Results ◽  
Effective Prevention ◽  
Modified Asphalt ◽  
Ultraviolet Resistance ◽  
Temperature Performance ◽  
Sbs Modified Asphalt ◽  
The Impact ◽  
Aging Performance

According to the test results of before and after the aging of asphalt performance,we analyse the dosage changes of the HALS anti ultraviolet ageing agent to improve SBS modified asphalt ultraviolet light resistance aging performance role. The test results show that GW-944 can better improve the ultraviolet resistance of asphalt aging performance, i.e., original sample asphalt have no other negative influence in a certain extent, and at the same time,also improve asphalt fatigue performance, low temperature performance and high temperature performance after the light aging, but the performance improvement needs to be in the right dosage range;Therefore,to the SBS modified asphalt we can use such ultraviolet aging agent for performance improvement,the research achievement for the airport asphalt pavement UV aging provide a technical basis for effective prevention and treatment.

Rotordynamic-Coefficient and Leakage Characteristics for Hole-Pattern-Stator Annular Gas Seals—Measurements Versus Predictions

2004 ◽  
Vol 126 (2) ◽  
pp. 326-333 ◽  
Author(s):  
Dara W. Childs ◽  
Jonathan Wade
Keyword(s):  
Flow Model ◽  
Control Volume ◽  
Test Results ◽  
Damping Coefficients ◽  
Supply Pressure ◽  
Static Data ◽  
Leakage Characteristics ◽  
Gas Seals ◽  
Stiffness And Damping ◽  
Rotordynamic Coefficient

Selected test results are presented for an annular gas seal using a smooth rotor and a hole-pattern-roughness stator for a supply pressure of 70 bar, three pressure ratios, three speeds up to 20,000 rpm, two clearances, and three preswirl ratios. Dynamic data include frequency-dependent direct and cross-coupled stiffness and damping coefficients. Static data include leakage and upstream and downstream pressures and temperatures. Very good agreements are found between measurements and predictions from a two-control-volume bulk-flow model.

The Impact of Real Gas Properties on Predictions of Static and Rotordynamic Properties of the Annular Gas Seals for Injection Compressors

2008 ◽  
Vol 130 (4) ◽  
Author(s):  
Yoon-Shik Shin ◽  
Dara W. Childs
Keyword(s):  
Energy Equation ◽  
Control Volume ◽  
Ideal Gas ◽  
Running Speed ◽  
Real Gas ◽  
Ideal Gas Law ◽  
Piston Seal ◽  
Gas Seals ◽  
The Impact ◽  
Gas Properties

Predictions are presented for an annular gas seal that is representative of the division-wall seal of a back-to-back compressor or the balance-piston seal of an in-line compressor. A two-control-volume bulk-flow model is used including the axial and circumferential momentum equations and the continuity equations. The basic model uses a constant-temperature prediction (ISOT) and an ideal gas law as an equation of state. Two variations are used: adding the energy equation with an ideal gas law (IDEAL), and adding the energy equation with real gas properties (REAL). The energy equations assume adiabatic flow. The ISOT model has been used for prior calculations. Concerning predictions of static characteristics, the calculated mass leakage rates were, respectively, 9.46 kg∕s, 9.55 kg∕s, and 7.87 kg∕s for ISOT, IDEAL, and REAL. For rotordynamic coefficients, predicted effective stiffness coefficients are comparable for the models at low excitation frequencies. At running speed, REAL predictions are roughly 40% lower than ISOT, which could result in lower predicted critical speeds. Predicted effective damping coefficients are also generally comparable. REAL and IDEAL predictions for the crossover frequency are approximately 20% lower than ISOT. REAL predictions for effective damping are modestly lower in the frequency range of 40–50% of running speed where higher damping values are desired.

A Design to Improve the Effective Damping Characteristics of Hole-Pattern-Stator Annular Gas Seals

2008 ◽  
Vol 130 (1) ◽  
Author(s):  
Dara W. Childs ◽  
Yoon-Shik Shin ◽  
Brent Seifert
Keyword(s):  
Friction Factor ◽  
Flow Path ◽  
Crossover Frequency ◽  
Test Results ◽  
Static Stiffness ◽  
Jump Phenomenon ◽  
Hole Depth ◽  
Negative Test ◽  
Damping Characteristics ◽  
Gas Seals

Predictions are presented for hole-pattern-stator seals for which the hole depth is varied axially, showing that various depth patterns can significantly improve damping performance in terms of both increasing the seal’s effective damping and reducing its crossover frequency—the frequency at which effective damping changes from positive to negative. Test results are presented for the seal with the best variable hole depth (VHD) pattern showing an increase in peak damping by a factor of 1.6 over a constant hole depth (CHD) design versus predictions of 2.7. The crossover frequency is reduced by approximately 40%. The VHD seal has a significant negative static stiffness that probably arises from a friction-factor-jump phenomenon, not flow path divergence. The VHD seal leaks less than a comparable CHD design.

Pemberian Umpan Balik Dalam Meningkatkan Hasil Belajar dan Minat Belajar Mahasiswa

2015 ◽  
Vol 4 (3) ◽  
Author(s):  
Seruni Seruni ◽  
Nurul Hikmah
Keyword(s):  
Information Technology ◽  
Learning Outcomes ◽  
Test Data ◽  
Random Sampling ◽  
Covariance Matrices ◽  
Test Results ◽  
Immediate Feedback ◽  
Statistics Course ◽  
Independent Variable ◽  
Descriptive Statistical Analysis

<p>The purpose of this study is to find and analyze the effect of feedback on <br />learning outcomes in mathematics and an interest in basic statistics course. The <br />population in this study are affordable Information Technology Student cademic Year 2012/2013 Semester II Indraprasta PGRI University of South Jakarta. Sample The study sample was obtained through random sampling. This study used an experimental method to the analysis using the MANOVA test. This study has three variables, consisting of: one independent variable, namely the provision of feedback (immediate and delayed), and two dependent variable is the result of interest in the study of mathematics and basic statistics course. The data was collected for the test results to learn mathematics, and a questionnaire for the interest in basic statistics course. Collected data were analyzed using the MANOVA test. Before the data were analyzed, first performed descriptive statistical analysis and test data analysis requirements (test data normality and homogeneity of covariance matrices). The results show that the learning outcomes of interest in mathematics and basic statistics course for students who are given immediate feedback higher than students given feedback delayed. <br /><br /></p>

Model estimates of the results of diabetes patients using modern glucometers with tri-color technology for displaying test results

2019 ◽  
pp. 81-89
Author(s):  
Larisa Dmitrievna Popovich ◽  
Svetlana Valentinovna Svetlichnaya ◽  
Aleksandr Alekseevich Moiseev
Keyword(s):  
Diabetes Mellitus ◽  
Type 2 Diabetes ◽  
Type 1 Diabetes ◽  
Economic Benefits ◽  
Test Results ◽  
Self Monitoring ◽  
Patients With Diabetes ◽  
The Impact

Diabetes – a disease in which the effect of the treatment substantially depends on the patient. Known a study showed that the use of glucometers with the technology of three-color display of test results facilitates self-monitoring of blood sugar and leads to a decrease in glycated hemoglobin (HbAlc). Purpose of the study: to modeling the impact of using of a glucometer with a color-coded display on the clinical outcomes of diabetes mellitus and calculating, the potential economic benefits of reducing the hospitalization rate of patients with diabetes. Material and methods. Based on data from two studies (O. Schnell et al. and M. Baxter et al.) simulation of the reduction in the number of complications with the use of a glucometer with a color indication. In a study by O. Schnell et al. a decrease of HbA1c by 0.69 percent is shown when using the considered type of glucometers, which was the basis of the model. Results. In the model, the use of a glucometer with a color-coded display for type 1 diabetes led to a decrease in the total number of complications by 9.2 thousand over 5 years per a cohort of 40 thousand patients with different initial levels of HbA1c. In a cohort of 40 thousand patients with type 2 diabetes, the simulated number of prevented complications was 1.7 thousand over 5 years. When extrapolating these data to all patients with diabetes included in the federal register of diabetes mellitus (FRD), the number of prevented complications was 55.4 thousand cases for type 1 diabetes and 67.1 thousand cases for type 2 diabetes. The possible economic effect from the use of the device by all patients with a diagnosis of diabetes, which are included in the FRD, estimated at 1.5 billion rubles for a cohort of patients with type 1 diabetes and 5.3 billion rubles for patients with type 2 diabetes. Conclusion. Improving the effectiveness of self-monitoring, which is the result of the use of glucometers with color indicators, can potentially significantly reduce the incidence of complications in diabetes and thereby provide significant economic benefits to society.

Do hotel industry operations deteriorate air quality?

2021 ◽  
pp. 135481662110224
Author(s):  
Liang-Ju Wang ◽  
Ming-Hsiang Chen ◽  
Zhandong Yang ◽  
Ching-Hui (Joan) Su
Keyword(s):  
Air Quality ◽  
Hotel Industry ◽  
Second Step ◽  
Test Results ◽  
Sales Revenue ◽  
Key Indicator ◽  
Regression Test ◽  
Rolling Regression ◽  
The Impact ◽  
Regression Tests

This study proposes and tests two hypotheses concerning the effects of hotel industry operations on air quality based on data of 26 major tourist cities in China from 2002 to 2017. The empirical analyses take two steps. In the first step, panel regression test results reveal that hotel industry operations (measured by hotel sales revenue) significantly raise the value of particulate matter (PM)2.5 (the key indicator of air quality), supporting the first hypothesis that hotel industry operations deteriorate air quality and providing empirical evidence of the adverse impact of the hotel industry on air quality. In the second step, subsample analyses support the second hypothesis that the impact of hotel sales revenue on air quality diminishes over time. The results from the rolling regression tests validate the existence of a diminishing effect of hotel industry operations on air quality.

scholarly journals The Impact of Mergers and Acquisitions and Sustainability on Company Performance in the Pharmaceutical Sector

2021 ◽  
Vol 13 (12) ◽  
pp. 6525
Author(s):  
Diana Marieta Mihaiu ◽  
Radu-Alexandru Șerban ◽  
Alin Opreana ◽  
Mihai Țichindelean ◽  
Vasile Brătian ◽  
...  
Keyword(s):  
Stock Market ◽  
Mergers And Acquisitions ◽  
Performance Improvement ◽  
Score Function ◽  
Pharmaceutical Companies ◽  
Company Performance ◽  
Direct Impact ◽  
Pharmaceutical Sector ◽  
Financial Measures ◽  
The Impact

The primary goal of this study was to determine the impact of mergers and acquisitions (M&A) and the environmental, social, and governance (ESG) sustainability scores of companies. In this regard, efforts to measure and analyze the evolution of a company’s performance, taking into account financial and non-financial measures using a score function, are adapted to the pharmaceutical sector. The sample consisted of 100 leading pharmaceutical companies, ranked by stock market capitalization, who registered 30% (n = 492) of the total M&A transactions over the study period (2010–2020). There was a direct and positive link between the M&A process and the evolution of company performance. The ESG score, as an indicator for measuring sustainability, has a positive and direct impact on company performance, indicating that a high ESG score determines an increase in company performance. A similar impact is identified for companies involved in M&A processes, meaning that companies in the pharmaceutical sector tend to register a performance improvement.

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