Performance of a microjet using component map scaling

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Kahraman Coban ◽  
Selcuk Ekici ◽  
Can Ozgur Colpan ◽  
Tahir Hikmet Karakoç
Keyword(s):  
Engine Performance ◽  
Cycle Performance ◽  
Real Component ◽  
Content Type ◽  
Turbojet Engine ◽  
Fluid Properties ◽  
The Difference ◽  
Comparative Results ◽  
Flight Regimes ◽  
Component Map

Purpose This paper aims to investigate the cycle performance of a small size turbojet engine used in unmanned aerial vehicles at 0–5,000 m altitude and 0–0.8 Mach flight speeds with real component maps. Design/methodology/approach The engine performance calculations were performed for both on-design and off-design conditions through an in-house code generated for simulating the performance of turbojet engines at different flight regimes. These calculations rely on input parameters in which fuel composition are obtained through laboratory elemental analysis. Findings Exemplarily, according to comparative results between in-house developed performance code and commercially available software, there is 0.25% of the difference in thrust value at on-design conditions. Practical implications Once the on-design performance parameters and fluid properties were determined, the off-design operation calculations were performed based on the compressor and turbine maps and scaling methodology. This method enables predicting component maps and fitting them to real conditions. Originality/value A method to be used easily by researchers on turbojet engine performance calculations which best fits to real conditions.

Energetic, exergetic, exergoeconomic, environmental (4E) and sustainability performances of an unmanned aerial vehicle micro turbojet engine

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Ozgur Balli ◽  
Alper Dalkıran ◽  
Tahir Hikmet Karakoç
Keyword(s):  
Environmental Sustainability ◽  
Engine Performance ◽  
Maximum Energy ◽  
Content Type ◽  
Cost Rate ◽  
Turbojet Engine ◽  
Energy And Exergy ◽  
Aerial Vehicle ◽  
Exergoeconomic Analysis ◽  
Engine Systems

Purpose This study aims to investigate the aviation, energetic, exergetic, environmental, sustainability and exergoeconomic performances of a micro turbojet engine used in unmanned aerial vehicles at four different modes. Design/methodology/approach The engine data were collected from engine test cell. The engine performance calculations were performed for four different operation modes. Findings According to the results, maximum energy and exergy efficiency were acquired as 19.19% and 18.079% at Mode 4. Total cost rate was calculated as 6.757 $/h at Mode-1, which varied to 10.131 $/h at Mode-4. Exergy cost of engine power was observed as 0.249 $/MJ at Mode-1, which decreased to 0.088 $/MJ at Mode-4 after a careful exergoeconomic analysis. Originality/value The novelty of this work is the capability to serve as a guide for similar systems with a detailed approach in the thermodynamic, thermoeconomic and environmental assessments by prioritizing efficiency, fuel consumption and cost formation. This investigation intends to establish a design of the opportunities and benefits that the thermodynamic approach provides to turbojet engine systems.

Component Map Tuning Procedure Using Adaptive Modeling

2012 ◽  
Author(s):  
Michel L. Verbist ◽  
Wilfried P. J. Visser ◽  
Rene Pecnik ◽  
Jos P. van Buijtenen
Keyword(s):  
Path Analysis ◽  
Gas Turbine ◽  
Engine Performance ◽  
Diagnostic Techniques ◽  
Reference Points ◽  
Performance Data ◽  
Adaptive Modeling ◽  
Real Component ◽  
Modeling Errors ◽  
Component Map

Performance models are effective tools for analysis of engine condition throughout the life cycle of a gas turbine engine. Component maps necessary for accurate performance modeling are typically not provided by the original equipment manufacturers. To compensate for the missing information, available maps of similar components are scaled to match component performance at one or more reference points. Although scaled maps can provide sufficiently accurate results close to the reference points, modeling errors tend to increase further away from these reference points. For applications such as gas path analysis, the resulting modeling errors can be of the same order of magnitude as the deterioration to be detected. This severely limits the application of such techniques. This article presents a component map tuning procedure that tunes maps with more detail than just scaling. The tuned maps are a closer match to real component performance. The tuning procedure combines the adaptive modeling capability of the Gas turbine Simulation Program (GSP) and on-wing measured engine performance data. On-wing measured engine performance data allows map tuning over a wider range of power settings compared to engine performance data measured in a test cell. Effects of measurement uncertainty and scatter, and effects of compressor bleed flows on the map tuning procedure are analyzed and discussed. The tuned component maps enabled more accurate component condition estimations, mainly characterized by less scatter. By improving the accuracy of gas path analysis with on-wing measured performance data, this work has enabled more effective use of performance diagnostic techniques in the aero-engine maintenance industry.

Component Map Generation of a Gas Turbine Using Genetic Algorithms

2004 ◽  
Author(s):  
Changduk Kong ◽  
Seonghee Kho ◽  
Jayoung Ki
Keyword(s):  
Genetic Algorithms ◽  
Performance Analysis ◽  
Gas Turbine ◽  
Pressure Ratio ◽  
Engine Performance ◽  
Experimental Tests ◽  
Real Component ◽  
Map Generation ◽  
Turboshaft Engine ◽  
Component Map

In order to estimate the precise performance of the existing gas turbine engine, the component maps with more realistic performance characteristics are needed. Because the components maps are engine manufacturer’s propriety obtained from very expensive experimental tests, they are not provided to the customers, generally. Therefore, because the engineers, who are working the performance simulation, have been mostly relying on component maps scaled from the similar existing maps, the accuracy of the performance analysis using the scaled maps may be relatively lower than that using the real component maps. Therefore, a component map generation method using experimental data and the genetic algorithms are newly proposed in this study. The engine test unit to be used for map generation has a free power turbine type small turboshaft engine. In order to generate the performance map for components of this engine, after obtaining engine performance data through many experimental tests, and then the third order equations, which have relationships the mass flow function, the pressure ratio and the isentropic efficiency as to the engine rotational speed were derived by using the genetic algorithm. A steady-state performance analysis was performed with the generated maps of the compressor by the commercial gas turbine performance analysis program GASTURB (Kruzke, 2001). In order to verify predominance of the proposed scheme, the performance analysis results using the maps obtained by this study were compared with those using the compressor map provided by the engine manufacturer and the scaled turbine maps obtained from the GASTURB, as well as experimental results. In comparison, it was found that the component maps can be generated from the experimental test data by using the genetic algorithms, and it was confirmed that the analysis results using the generated maps were very similar to those using the scaled maps from the GASTURB.

Component Map Generation of a Gas Turbine Using Genetic Algorithms

2004 ◽  
Vol 128 (1) ◽  
pp. 92-96 ◽  
Author(s):  
Changduk Kong ◽  
Seonghee Kho ◽  
Jayoung Ki
Keyword(s):  
Experimental Data ◽  
Genetic Algorithms ◽  
Performance Analysis ◽  
Gas Turbine ◽  
Pressure Ratio ◽  
Engine Performance ◽  
Experimental Tests ◽  
Real Component ◽  
Map Generation ◽  
Component Map

In order to estimate the precise performance of the existing gas turbine engine, the component maps with more realistic performance characteristics are needed. Because the component maps are the engine manufacturer’s propriety obtained from very expensive experimental tests, they are not provided to the customers, generally. Therefore, because the engineers, who are working the performance simulation, have been mostly relying on component maps scaled from the similar existing maps, the accuracy of the performance analysis using the scaled maps may be relatively lower than that using the real component maps. Therefore, a component map generation method using experimental data and the genetic algorithms are newly proposed in this study. The engine test unit to be used for map generation has a free power turbine type small turboshaft engine. In order to generate the performance map for compressor of this engine, after obtaining engine performance data through experimental tests, and then the third order equations, which have relationships with the mass flow function, the pressure ratio, and the isentropic efficiency as to the engine rotational speed, were derived by using the genetic algorithms. A steady-state performance analysis was performed with the generated maps of the compressor by the commercial gas turbine performance analysis program GASTURB (Kurzke, 2001). In order to verify the proposed scheme, the experimental data for verification were compared with performance analysis results using traditional scaled component maps and performance analysis results using a generated compressor map by genetic algorithms (GAs). In comparison, it was found that the analysis results using the generated map by GAs were well agreed with experimental data. Therefore, it was confirmed that the component maps can be generated from the experimental data by using GAs and it may be considered that the more realistic component maps can be obtained if more various conditions and accurate sensors would be used.

Performance monitoring and analysis of various parameters for a small UAV turbojet engine

2018 ◽  
Vol 90 (5) ◽  
pp. 779-787 ◽  
Author(s):  
Emre Kiyak ◽  
Gulay Unal ◽  
Nilgun Fazilet Ozer
Keyword(s):  
Performance Monitoring ◽  
Engine Performance ◽  
Real Data ◽  
Point Of View ◽  
Performance Parameters ◽  
Engine Operation ◽  
Content Type ◽  
Turbojet Engine ◽  
Engine Industry ◽  
Aerial Vehicle

Purpose This paper aims to discuss engine health monitoring for unmanned aerial vehicles. It is intended to make consistent predictions about the future status of the engine performance parameters by using their current states. Design/methodology/approach The aim is to minimize risks before they turn into problems. In accordance with these objectives, temporal and financial savings are planned to be achieved by contributing processes such as extending the engine life, preventing early disassembly-reassembly and mechanical wears and reducing the maintenance costs. Based on this point of view, a data-based software is developed in MATLAB (Matrix Laboratory) program for the so-called process. Findings The software is operated for the performance parameters of the turbojet engine that is used in a small unmanned aerial vehicle of Tusas Engine Industry. The obtained results are compared with the real data of the engine. As a result of this comparison, a fault that may occur in the engine can be detected before being determined. Originality/value It is clearly demonstrated that the engine operation in adverse conditions can be prevented. This situation means that the software developed operates successfully.

What makes the difference? Employee social media brand engagement

2019 ◽  
Vol 34 (7) ◽  
pp. 1459-1467 ◽  
Author(s):  
Sherese Y. Duncan ◽  
Raeesah Chohan ◽  
João José Ferreira
Keyword(s):  
Social Media ◽  
Brand Equity ◽  
Positive Emotions ◽  
Content Type ◽  
Word Use ◽  
Brand Engagement ◽  
Analytical Thinking ◽  
Industry Competition ◽  
The Difference ◽  
Business To Business

Purpose This paper aims to explore, using the employee lens of business-to-business firms, word use through brand engagement and social media interaction to understand the difference between employees who rate their employer brands highly on social media and those who don't. Design/methodology/approach We conducted a textual content analysis of posts published on the social media job evaluation site glassdoor.com. LIWC software package was used to analyze 30 of the top 200 business-to-business brands listed on Brandwatch using four variables, namely, analytical thinking, clout, authenticity and emotional tone. Findings The results show that employees who rate their employer’s brand low use significantly more words, are significantly less analytic and write with significantly more clout because they focus more on others than themselves. Employees who rate their employer’s brand highly, write with significantly more authenticity, exhibit a significantly higher tone and display far more positive emotions in their reviews. Practical implications Brand managers should treat social media data disseminated by individual stakeholders, like the variables used in this study (tone, word count, frequency), as a valuable tool for brand insight on their industry, competition and their own brand equity, now and especially over time. Originality/value This study provides acknowledgement that social media is a significant source of marketing intelligence that may improve brand equity by better understanding and managing brand engagement.

Disposition effect at the market level: evidence from Indian stock market

2019 ◽  
Vol 12 (2) ◽  
pp. 69-82
Author(s):  
Sravani Bharandev ◽  
Sapar Narayan Rao
Keyword(s):  
Trading Volume ◽  
Stock Exchange ◽  
Reference Points ◽  
Disposition Effect ◽  
Content Type ◽  
Ex Post ◽  
Abnormal Trading Volume ◽  
The Difference ◽  
Trading Volumes ◽  
Indian Stock Market

Purpose The purpose of this paper is to test the disposition effect at market level and propose an appropriate reference point for testing disposition at market level. Design/methodology/approach This is an empirical study conducted on 500 index stocks of NSE500 (National Stock Exchange). Winning and losing days for each stock are calculated using 52-week high and low prices as reference points. To test disposition effect, abnormal trading volumes of stocks are regressed on their percentage of winning (losing) days. Further using ANOVA, the difference between mean of percentage of winning (losing) days of high abnormal trading volume deciles and low abnormal trading volume deciles is tested. Findings Results show that a stock’s abnormal trading volume is positively influenced by the percentage of winning days whereas percentage of losing days show no such effect. Findings are consistent even after controlling for volatility and liquidity. ANOVA results show the presence of high percentage of winning days in higher deciles of abnormal trading volumes and no such pattern in case of losing days confirms the presence of disposition effect. Further an ex post analysis indicates that disposition prone investors accumulate losses. Originality/value This is the first study, which proposes the use of 52-week high and low prices as reference points to test the market-level disposition effect. Findings of this study enhance the limited literature available on disposition effect in emerging markets by providing evidence from Indian stock markets.

Workspace, dexterity and dimensional optimization of microhexapod

2015 ◽  
Vol 35 (4) ◽  
pp. 341-347 ◽  
Author(s):  
E. Rouhani ◽  
M. J. Nategh
Keyword(s):  
Degrees Of Freedom ◽  
Optimization Problem ◽  
Screw Theory ◽  
Design Parameters ◽  
Dimensional Synthesis ◽  
Content Type ◽  
Workspace Analysis ◽  
The Difference ◽  
Flexure Joints ◽  
6 Degrees Of Freedom

Purpose – The purpose of this paper is to study the workspace and dexterity of a microhexapod which is a 6-degrees of freedom (DOF) parallel compliant manipulator, and also to investigate its dimensional synthesis to maximize the workspace and the global dexterity index at the same time. Microassembly is so essential in the current industry for manufacturing complicated structures. Most of the micromanipulators suffer from their restricted workspace because of using flexure joints compared to the conventional ones. In addition, the controllability of micromanipulators inside the whole workspace is very vital. Thus, it is very important to select the design parameters in a way that not only maximize the workspace but also its global dexterity index. Design/methodology/approach – Microassembly is so essential in the current industry for manufacturing complicated structures. Most of the micromanipulators suffer from their restricted workspace because of using flexure joints compared to the conventional ones. In addition, the controllability of micromanipulators inside the whole workspace is very vital. Thus, it is very important to select the design parameters in a way that not only maximize the workspace but also its global dexterity index. Findings – It has been shown that the proposed procedure for the workspace calculation can considerably speed the required calculations. The optimization results show that a converged-diverged configuration of pods and an increase in the difference between the moving and the stationary platforms’ radii cause the global dexterity index to increase and the workspace to decrease. Originality/value – The proposed algorithm for the workspace analysis is very important, especially when it is an objective function of an optimization problem based on the search method. In addition, using screw theory can simply construct the homogeneous Jacobian matrix. The proposed methodology can be used for any other micromanipulator.

Parental leave length, social norms, and female labor market re-entry frictions

2018 ◽  
Vol 39 (4) ◽  
pp. 600-620 ◽  
Author(s):  
Vojtech Bartoš ◽  
Barbara Pertold-Gebicka
Keyword(s):  
Labor Market ◽  
Social Norms ◽  
Job Search ◽  
Social Norm ◽  
Parental Leave ◽  
Human Resource Managers ◽  
Content Type ◽  
Job Applicant ◽  
Employment Gaps ◽  
The Difference

Purpose The purpose of this paper is to identify the role of employers in creating employment gaps among women returning to the labor market after parental leaves of different durations. Design/methodology/approach The authors use a controlled correspondence field experiment that orthogonally manipulates parental leave length and the quality of fictitious female job candidates. The experiment is complemented with a survey among human resource managers. Findings High-quality candidates receive more interview invitations when applying after a short parental leave, while low-quality (LQ) candidates receive more interview invitations when applying after a typical three years long parental leave. Survey results suggest that the difference in invitations between short and typical leave treatments is driven by a social norm that mothers should stay home with children younger than three. Productivity gains from employing a LQ job applicant with a shorter career break might not be high enough to outweigh the adverse social norm effect. Social implications The presented results point toward the strong effect of prevailing social norms on job search prospects of women returning to the labor market after parental leave. Originality/value A correspondence experiment has not been used before to study the relationship between time spent on leave and the labor market prospects of mothers. It also extends research on social norms to the domain of hiring decisions.

Associated change in plantar temperature and sweating after transthoracic endoscopic T2–3 sympathectomy for palmar hyperhidrosis

2001 ◽  
Vol 95 (1) ◽  
pp. 58-63 ◽  
Author(s):  
Han-Jung Chen ◽  
Cheng-Loong Liang ◽  
Kang Lu
Keyword(s):  
Skin Temperature ◽  
Temperature Change ◽  
The Body ◽  
Palmar Hyperhidrosis ◽  
Compensatory Sweating ◽  
Content Type ◽  
Postoperative Changes ◽  
The Face ◽  
The Difference ◽  
Fine Print

Object. Transthoracic endoscopic T2–3 sympathectomy is currently the treatment of choice for palmar hyperhidrosis. Compensatory sweating of the face, trunk, thigh, and sole of the foot was found in more than 50% of patients who underwent this procedure. The authors conducted this study to investigate the associated intraoperative changes in plantar skin temperature and postoperative plantar sweating. Methods. One hundred patients with palmar hyperhidrosis underwent bilateral transthoracic endoscopic T2–3 sympathectomy. There were 60 female and 40 male patients who ranged in age from 13 to 40 years (mean age 21.6 years). Characteristics studied included changes in palmar and plantar skin temperature measured intraoperatively, as well as pre- and postoperative changes in plantar sweating and sympathetic skin responses (SSRs). In 59 patients (59%) elevation of plantar temperature was demonstrated at the end of the surgical procedure. In this group, plantar sweating was found to be exacerbated in three patients (5%); plantar sweating was improved in 52 patients (88.1%); and no change was demonstrated in four patients (6.8%). In the other group of patients in whom no temperature change occurred, increased plantar sweating was demonstrated in three patients (7.3%); plantar sweating was improved in 20 patients (48.8%); and no change was shown in 18 patients (43.9%). The difference between temperature and sweating change was significant (p = 0.001). Compared with the presympathectomy rate, the rate of absent SSR also significantly increased after sympathectomy: from 20 to 76% after electrical stimulation and 36 to 64% after deep inspiration stimulation, respectively (p < 0.05). Conclusions. In contrast to compensatory sweating in other parts of the body after T2–3 sympathetomy, improvement in plantar sweating was shown in 72% and worsened symptoms in 6% of patients. The intraoperative plantar skin temperature change and perioperative SSR demonstrated a correlation between these changes.

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