Altitude Effects on the Performance of Small Radial Turbomachinery: Part I — Compressor Impellers

2016 ◽  
Author(s):  
Dries Verstraete ◽  
Kjersti Lunnan
Keyword(s):  
Reynolds Number ◽  
Performance Analysis ◽  
Rotational Speed ◽  
Pressure Ratio ◽  
Unmanned Aircraft ◽  
Good Match ◽  
One Dimensional ◽  
Design Changes ◽  
Current Article ◽  
The Impact

Small unmanned aircraft are currently limited to flight ceilings below 20,000 ft due to the lack of an appropriate propulsion system. One of the most critical technological hurdles for an increased flight ceiling of small platforms is the impact of reduced Reynolds number conditions at altitude on the performance of small radial turbomachinery. The current article investigates the influence of Reynolds number on the efficiency and pressure ratio of two small centrifugal compressor impellers using a one-dimensional meanline performance analysis code. The results show that the efficiency and pressure ratio of the 60 mm baseline compressor at the design rotational speed drops with 6–9% from sea-level to 70,000 ft. The impact on the smaller 20 mm compressor is slightly more pronounced and amounts to 6–10%. Off-design changes at low rotational speeds are significantly higher and can amount to up to 15%. Whereas existing correlations show a good match for the efficiency drop at the design rotational speed, they fail to predict efficiency changes with rotational speed. A modified version is therefore proposed.

Altitude Effects on the Performance of Small Radial Turbomachinery: Part II — Turbine Impellers

2016 ◽  
Author(s):  
Dries Verstraete ◽  
Kjersti Lunnan
Keyword(s):  
Reynolds Number ◽  
Performance Analysis ◽  
Laminar Flow ◽  
Sea Level ◽  
Pressure Ratio ◽  
Unmanned Aircraft ◽  
Efficiency Loss ◽  
Current Article ◽  
The Impact ◽  
Radial Turbines

Small unmanned aircraft are currently limited to flight ceilings below 20,000 ft (6.1 km) due to the lack of an appropriate propulsion system. One of the most critical technological hurdles for an increased flight ceiling of small platforms is the impact of the low Reynolds number conditions at altitude on the performance of small radial turbomachinery. The current article investigates the influence of Reynolds number on the efficiency and pressure ratio of 5 radial turbines using a 1D meanline performance analysis code. The results show that the efficiency at the design rotational speed drops by up to 30% from sea-level to 70,000 feet. However, the bulk of this efficiency loss occurs above approximately 20,000 feet where the flow in most turbines transitions to laminar flow. Existing turbine scaling correlations do not predict this efficiency loss well. However, an adapted method from compressor scaling research is shown to be fairly accurate.

Aspects of Cooled Gas Turbine Modelling for the Semi-Closed O2/CO2 Cycle With CO2 Capture

2003 ◽  
Author(s):  
Kristin Jordal ◽  
Olav Bolland ◽  
A˚ke Klang
Keyword(s):  
Gas Turbine ◽  
Rotational Speed ◽  
Pressure Ratio ◽  
Continuous Process ◽  
Cycle Performance ◽  
Inlet Temperature ◽  
Outlet Temperature ◽  
Stage Model ◽  
Detailed Model ◽  
The Impact

In order to capture the behaviour of the oxyfuel cycle operating with high combustor-outlet temperature, the impact of blade and vane cooling on cycle performance must be included in the thermodynamic model. As a basis for a future transient model, three thermodynamic models for the cooled gas turbine are described and compared. The first model, known previously from the literature, models expansion as a continuous process with simultaneous heat and work extraction. The second model is a simple stage-by-stage model and the third is a more detailed stage-by-stage model that includes velocity triangles and enables the use of advanced loss correlations. An airbreathing aeroderivative gas turbine is modelled, and the same gas turbine operating in an oxyfuel cycle is studied. The two simple models show very similar performance trends in terms of variation of pressure ratio and turbine inlet temperature in both cases. With the more detailed model, it was found that, without any change of geometry, the turbine rotational speed increases significantly and performance drops for the maintained geometry and pressure ratio. A tentative increase of blade angles or compressor pressure ratio is found to increase turbine performance and decrease rotational speed. This indicates that a turbine will require re-design for operation in the oxyfuel cycle.

Aspects of Cooled Gas Turbine Modeling for the Semi-Closed O2/CO2 Cycle With CO2 Capture

2004 ◽  
Vol 126 (3) ◽  
pp. 507-515 ◽  
Author(s):  
Kristin Jordal ◽  
Olav Bollard ◽  
Ake Klang
Keyword(s):  
Gas Turbine ◽  
Rotational Speed ◽  
Pressure Ratio ◽  
Continuous Process ◽  
Cycle Performance ◽  
Inlet Temperature ◽  
Outlet Temperature ◽  
Stage Model ◽  
Detailed Model ◽  
The Impact

In order to capture the behavior of the oxyfuel cycle operating with high combustor-outlet temperature, the impact of blade and vane cooling on cycle performance must be included in the thermodynamic model. As a basis for a future transient model, three thermodynamic models for the cooled gas turbine are described and compared. The first model, known previously from the literature, models expansion as a continuous process with simultaneous heat and work extraction. The second model is a simple stage-by-stage model and the third is a more detailed stage-by-stage model that includes velocity triangles and enables the use of advanced loss correlations. An airbreathing aeroderivative gas turbine is modeled, and the same gas turbine operating in an oxyfuel cycle is studied. The two simple models show very similar performance trends in terms of variation of pressure ratio and turbine inlet temperature in both cases. With the more detailed model, it was found that, without any change of geometry, the turbine rotational speed increases significantly and performance drops for the maintained geometry and pressure ratio. A tentative increase of blade angles or compressor pressure ratio is found to increase turbine performance and decrease rotational speed. This indicates that a turbine will require redesign for operation in the oxyfuel cycle.

Detailed Heat Transfer Measurements of Jet Impingement on Dimpled Target Surface Under Rotation

2018 ◽  
Vol 10 (3) ◽  
Author(s):  
Prashant Singh ◽  
Srinath V. Ekkad
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Liquid Crystal ◽  
Rotational Speed ◽  
Buoyancy Force ◽  
Jet Impingement ◽  
Target Surface ◽  
Transfer Enhancement ◽  
One Dimensional ◽  
Enhancing Heat Transfer

The present study investigates the effects of Coriolis force and centrifugal buoyancy force on heat transfer due to jet impingement on dimpled target surface (DT). Detailed heat transfer measurements were carried out using transient liquid crystal (LC) thermography, where the target surface was modeled as one-dimensional (1D) semi-infinite solid. Three different configurations of DT surfaces have been studied. The flow and rotation conditions have been kept the same for all the configurations, where the average Reynolds number (based on jet hole hydraulic diameter: Rej) was 2500 and the rotational speed was 400 rpm (corresponding to Roj of 0.00274). Under nonrotating conditions, DT surface showed positive heat transfer enhancements compared to smooth target surfaces. Under rotating conditions, it was observed that rotation was helpful in enhancing heat transfer on leading and trailing sides for smooth target surface. However, for the DT surfaces, rotation proved to be detrimental to heat transfer enhancement.

Improvement of One-Dimensional Analytical Model of Rotating Long Orifice with Chamfered or Radiused Inlet

2013 ◽  
Vol 444-445 ◽  
pp. 320-331
Author(s):  
Hong Wu ◽  
Peng Li ◽  
Dong Dong Liu ◽  
Zhi Tao
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Reynolds Number ◽  
Analytical Model ◽  
Working Conditions ◽  
Low Reynolds Number ◽  
Pressure Ratio ◽  
Acceptable Error ◽  
One Dimensional ◽  
Low Reynolds

In this paper, computational fluid dynamics calculations were conducted under various kinds of complex working conditions for rotating long orifice. As one of the most important structures of throttling and pressure limiting, orifice plays a significant role in flow control of the whole system. The existing empirical correlation was improved by correction on characteristics of low Reynolds number and compressibility. Then, improved one-dimensional analytical model of rotating long orifice with chamfered or radiused inlet was developed by programming. The model was verified against the results of commercial computational fluid dynamics codes. It turns out that the model has high precision, excellent convergence, and can predict the flow parameters under working conditions of low Reynolds number, supersonic and high pressure ratio with an acceptable error. And only geometric features, rotational speed and boundary conditions are required for one-dimensional modeling. Thus, it can be applied in the one-dimensional calculation and design of secondary air system widely.

Modeling and Performance Analysis of a Dual-Shaft Counter-Rotating Gas Turbine

2018 ◽  
Author(s):  
Qiao Zhou ◽  
Zhao Yin ◽  
Chun-qing Tan ◽  
Qing Gao ◽  
Yong-sheng Tian
Keyword(s):  
High Pressure ◽  
Performance Analysis ◽  
Gas Turbine ◽  
Rotational Speed ◽  
Pressure Ratio ◽  
Low Pressure ◽  
Modeling Method ◽  
Speed Ratio ◽  
Shaft Speed ◽  
Wide Range

This paper proposes a modeling method for the 1+1/2 vaneless counter rotating turbine (VCRT) and carries out performance analysis of a micro gas turbine (MGT) with VCRT at off design conditions. The first task of this paper is to obtain performance characteristics maps and develop a characteristics modeling method of VCRT. The VCRT characteristics maps are obtained through 3-D CFD calculation. High pressure turbine (HPT) corrected rotational speed, shaft rotating speed ratio defined as the high pressure (HP) shaft rotational speed divided by low pressure (LP) shaft rotational speed, and the VCRT total expansion pressure ratio are selected to model a 3-D low pressure turbine (LPT) characteristics maps. However, the HPT characteristics map modeling method remains the same as the conventional one. An overall performance simulation model is established in Matlab/Simulink and validated by software GasTurb. The VCRT engine consumes fuel at a higher rate when delivering same power compared with the conventional gas turbine due to LPT performance degradation. When the relative LP shaft speed ranges from 100% to 96%, the performance of the VCRT engine and conventional engine is almost equivalent. As the LP shaft speed continues to drop off, however, the VCRT engine performance degrades considerably. The results indicate that it is crucial to design VCRT with a wide range of efficiency, especially the LPT. The VCRT engine control law also must be effectively optimized to ensure the engine performs well at part load working conditions.

HOME VISITS DURING THE FIRST MONTH OF DELIVERY FOR RECENTLY DELIVERED WOMEN IN UTTAR PRADESH, INDIA

2020 ◽  
Vol 6 (5) ◽  
pp. 1183-1189
Author(s):  
Dr. Tridibesh Tripathy ◽  
Dr. Umakant Prusty ◽  
Dr. Chintamani Nayak ◽  
Dr. Rakesh Dwivedi ◽  
Dr. Mohini Gautam
Keyword(s):  
Large Scale ◽  
National Level ◽  
Uttar Pradesh ◽  
Life Time ◽  
Structured Interview ◽  
The Other ◽  
Registration System ◽  
Action Group ◽  
Current Article ◽  
The Impact

The current article of Uttar Pradesh (UP) is about the ASHAs who are the daughters-in-law of a family that resides in the same community that they serve as the grassroots health worker since 2005 when the NRHM was introduced in the Empowered Action Group (EAG) states. UP is one such Empowered Action Group (EAG) state. The current study explores the actual responses of Recently Delivered Women (RDW) on their visits during the first month of their recent delivery. From the catchment area of each of the 250 ASHAs, two RDWs were selected who had a child in the age group of 3 to 6 months during the survey. The response profiles of the RDWs on the post- delivery first month visits are dwelled upon to evolve a picture representing the entire state of UP. The relevance of the study assumes significance as detailed data on the modalities of postnatal visits are available but not exclusively for the first month period of their recent delivery. The details of the post-delivery first month period related visits are not available even in large scale surveys like National Family Health Survey 4 done in 2015-16. The current study gives an insight in to these visits with a five-point approach i.e. type of personnel doing the visit, frequency of the visits, visits done in a particular week from among those four weeks separately for the three visits separately. The current study is basically regarding the summary of this Penta approach for the post- delivery one-month period.     The first month period after each delivery deals with 70% of the time of the postnatal period & the entire neonatal period. Therefore, it does impact the Maternal Mortality Rate & Ratio (MMR) & the Neonatal Mortality Rates (NMR) in India and especially in UP through the unsafe Maternal & Neonatal practices in the first month period after delivery. The current MM Rate of UP is 20.1 & MM Ratio is 216 whereas the MM ratio is 122 in India (SRS, 2019). The Sample Registration System (SRS) report also mentions that the Life Time Risk (LTR) of a woman in pregnancy is 0.7% which is the highest in the nation (SRS, 2019). This means it is very risky to give birth in UP in comparison to other regions in the country (SRS, 2019). This risk is at the peak in the first month period after each delivery. Similarly, the current NMR in India is 23 per 1000 livebirths (UNIGME,2018). As NMR data is not available separately for states, the national level data also hold good for the states and that’s how for the state of UP as well. These mortalities are the impact indicators and such indicators can be reduced through long drawn processes that includes effective and timely visits to RDWs especially in the first month period after delivery. This would help in making their post-natal & neonatal stage safe. This is the area of post-delivery first month visit profile detailing that the current article helps in popping out in relation to the recent delivery of the respondents.   A total of four districts of Uttar Pradesh were selected purposively for the study and the data collection was conducted in the villages of the respective districts with the help of a pre-tested structured interview schedule with both close-ended and open-ended questions.  The current article deals with five close ended questions with options, two for the type of personnel & frequency while the other three are for each of the three visits in the first month after the recent delivery of respondents. In addition, in-depth interviews were also conducted amongst the RDWs and a total 500 respondents had participated in the study.   Among the districts related to this article, the results showed that ASHA was the type of personnel who did the majority of visits in all the four districts. On the other hand, 25-40% of RDWs in all the 4 districts replied that they did not receive any visit within the first month of their recent delivery. Regarding frequency, most of the RDWs in all the 4 districts received 1-2 times visits by ASHAs.   Regarding the first visit, it was found that the ASHAs of Barabanki and Gonda visited less percentage of RDWs in the first week after delivery. Similarly, the second visit revealed that about 1.2% RDWs in Banda district could not recall about the visit. Further on the second visit, the RDWs responded that most of them in 3 districts except Gonda district did receive the second postnatal visit in 7-15 days after their recent delivery. Less than half of RDWs in Barabanki district & just more than half of RDWs in Gonda district received the third visit in 15-21 days period after delivery. For the same period, the majority of RDWs in the rest two districts responded that they had been entertained through a home visit.

scholarly journals Performance Analysis and Design Considerations of the Shallow Underwater Optical Wireless Communication System with Solar Noises Utilizing a Photon Tracing-Based Simulation Platform

Electronics ◽  
2021 ◽  
Vol 10 (5) ◽  
pp. 632
Author(s):  
Xiaozheng Wang ◽  
Minglun Zhang ◽  
Hongyu Zhou ◽  
Xiaomin Ren
Keyword(s):  
Performance Analysis ◽  
Wireless Communication ◽  
Ambient Noise ◽  
Large Scale ◽  
Delay Spread ◽  
Simulation Platform ◽  
Optical Wireless Communication ◽  
Optical Wireless ◽  
Analysis And Design ◽  
The Impact

The performance of the underwater optical wireless communication (UOWC) system is highly affected by seawater´s inherent optical properties and the solar radiation from sunlight, especially for a shallow environment. The multipath effect and degradations in signal-to-noise ratio (SNR) due to absorption, scattering, and ambient noises can significantly limit the viable communication range, which poses key challenges to its large-scale commercial applications. To this end, this paper proposes a unified model for underwater channel characterization and system performance analysis in the presence of solar noises utilizing a photon tracing algorithm. Besides, we developed a generic simulation platform with configurable parameters and self-defined scenarios via MATLAB. Based on this platform, a comprehensive investigation of underwater channel impairments was conducted including temporal and spatial dispersion, illumination distribution pattern, and statistical attenuation with various oceanic types. The impact of ambient noise at different operation depths on the bit error rate (BER) performance of the shallow UOWC system was evaluated under typical specifications. Simulation results revealed that the multipath dispersion is tied closely to the multiple scattering phenomenon. The delay spread and ambient noise effect can be mitigated by considering a narrow field of view (FOV) and it also enables the system to exhibit optimal performance on combining with a wide aperture.

scholarly journals Numerical analysis of high-lift configurations with oscillating flaps

2021 ◽  
Author(s):  
Johannes Ruhland ◽  
Christian Breitsamter
Keyword(s):  
Reynolds Number ◽  
Flow Separation ◽  
Separated Flow ◽  
Navier Stokes ◽  
Rotational Axis ◽  
High Lift ◽  
Hinge Point ◽  
Reduced Frequency ◽  
Flap Deflection ◽  
The Impact

AbstractThis study presents two-dimensional aerodynamic investigations of various high-lift configuration settings concerning the deflection angles of droop nose, spoiler and flap in the context of enhancing the high-lift performance by dynamic flap movement. The investigations highlight the impact of a periodically oscillating trailing edge flap on lift, drag and flow separation of the high-lift configuration by numerical simulations. The computations are conducted with regard to the variation of the parameters reduced frequency and the position of the rotational axis. The numerical flow simulations are conducted on a block-structured grid using Reynolds Averaged Navier Stokes simulations employing the shear stress transport $$k-\omega $$ k - ω turbulence model. The feature Dynamic Mesh Motion implements the motion of the oscillating flap. Regarding low-speed wind tunnel testing for a Reynolds number of $$0.5 \times 10^{6}$$ 0.5 × 10 6 the flap movement around a dropped hinge point, which is located outside the flap, offers benefits with regard to additional lift and delayed flow separation at the flap compared to a flap movement around a hinge point, which is located at 15 % of the flap chord length. Flow separation can be suppressed beyond the maximum static flap deflection angle. By means of an oscillating flap around the dropped hinge point, it is possible to reattach a separated flow at the flap and to keep it attached further on. For a Reynolds number of $$20 \times 10^6$$ 20 × 10 6 , reflecting full scale flight conditions, additional lift is generated for both rotational axis positions.

Impact of UAS with Low Size, Weight, and Power Sensors on Air Traffic Controllers’ Performance and Acceptability Ratings

2020 ◽  
Vol 64 (1) ◽  
pp. 154-158
Author(s):  
Kim-Phuong L. Vu ◽  
Jonathan VanLuven ◽  
Timothy Diep ◽  
Vernol Battiste ◽  
Summer Brandt ◽  
...  
Keyword(s):  
Air Traffic ◽  
Unmanned Aircraft ◽  
Unmanned Aircraft Systems ◽  
Subjective Ratings ◽  
Detection Range ◽  
Human In The Loop ◽  
Air Traffic Controllers ◽  
Low Altitude ◽  
Sector Performance ◽  
The Impact

A human-in-the-loop simulation was conducted to evaluate the impact of Unmanned Aircraft Systems (UAS) with low size, weight, and power (SWaP) sensors operating in a busy, low-altitude sector. Use of low SWaP sensors allow for UAS to perform detect-and-avoid (DAA) maneuvers against non-transponding traffic in the sector. Depending upon the detection range of the low SWaP sensor, the UAS pilot may or may not have time to coordinate with air traffic controllers (ATCos) prior to performing the DAA maneuver. ATCo’s sector performance and subjective ratings of acceptability were obtained in four conditions that varied in UAS-ATCo coordination (all or none) prior to the DAA maneuver and workload (higher or lower). For performance, ATCos committed more losses of separation in high than low workload conditions. They also had to make more flight plan changes to manage the UAS when the UAS pilot did not coordinate DAA maneuvers compared to when they did coordinate the maneuvers prior to execution. Although the ATCos found the DAA procedures used by the UAS in the study to be acceptable, most preferred the UAS pilot to coordinate their DAA maneuvers with ATCos prior to executing them.

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