Theoretical and Experimental Study of Helicopter Icing Scaling Methods PDF Download
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Author: Yiqiang Han
Publisher: LAP Lambert Academic Publishing
ISBN: 9783846598290
Category :
Languages : en
Pages : 160
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Book Description
Flight into icing conditions introduces the risk of ice accretion to helicopter rotors. To understand and avoid the dangers related to rotor icing, test facilities such as the NASA Glenn Icing Research Tunnel have been developed. Due to the confined test section size of most current icing test facilities, an icing test on a full-chord helicopter rotor blade is not possible. To fulfill the research need of a novel full-scale-chord rotor icing test facility, the Adverse Environment Rotor Test Stand (AERTS) was designed and constructed at the Vertical Lift Research Center of Excellence, at the Pennsylvania State University. This book gives a comprehensive review of the current aircraft icing research. Ice accretion experiments were conducted to validate ice shape reproduction capabilities of this facility. Classical ice scaling methods were introduced and implemented to ensure experimental ice shape reproduction for varying chord-size blades. The validity of applying scaling laws to low-thrusting rotors was demonstrated. The comprehensive aircraft icing database provided in this book can be applied widely to the aircraft design and testing procedures.
Author: Yiqiang Han
Publisher: LAP Lambert Academic Publishing
ISBN: 9783846598290
Category :
Languages : en
Pages : 160
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Book Description
Flight into icing conditions introduces the risk of ice accretion to helicopter rotors. To understand and avoid the dangers related to rotor icing, test facilities such as the NASA Glenn Icing Research Tunnel have been developed. Due to the confined test section size of most current icing test facilities, an icing test on a full-chord helicopter rotor blade is not possible. To fulfill the research need of a novel full-scale-chord rotor icing test facility, the Adverse Environment Rotor Test Stand (AERTS) was designed and constructed at the Vertical Lift Research Center of Excellence, at the Pennsylvania State University. This book gives a comprehensive review of the current aircraft icing research. Ice accretion experiments were conducted to validate ice shape reproduction capabilities of this facility. Classical ice scaling methods were introduced and implemented to ensure experimental ice shape reproduction for varying chord-size blades. The validity of applying scaling laws to low-thrusting rotors was demonstrated. The comprehensive aircraft icing database provided in this book can be applied widely to the aircraft design and testing procedures.
Author: David N. Anderson
Publisher:
ISBN:
Category :
Languages : en
Pages : 22
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Author:
Publisher:
ISBN:
Category : Aeronautics
Languages : en
Pages : 220
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Author: Baofeng Cheng
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
An investigation of helicopter rotor noise during ice accretion is conducted using experimental, theoretical, and numerical methods. This research is the acoustic part of a joint helicopter rotor icing physics, modeling, and detection project at The Pennsylvania State University Vertical Lift Research Center of Excellence (VLRCOE). The current research aims to provide acoustic insight and understanding of the rotor icing physics and investigate the feasibility of detecting rotor icing through noise measurements, especially at the early stage of ice accretion. All helicopter main rotor noise source mechanisms and their change during ice accretion are discussed. Changes of the thickness noise, steady loading noise, and especially the turbulent boundary layer trailing edge (TBL-TE) noise due to ice accretion are identified and studied.The change of the discrete frequency noise (thickness noise and steady loading noise) due to ice accretion is calculated by using PSU-WOPWOP, an advanced rotorcraft acoustic prediction code. The change is noticeable, but too small to be used in icing detection. The small thickness noise change is due to the small volume of the accreted ice compared to that of the entire blade, although a large iced airfoil shape is used. For the loading noise calculation, two simplified methods are used to generate the loading on the rotor blades, which is the input for the loading noise calculation: 1) compact loading from blade element momentum theory, icing effects are considered by increasing the drag coefficient; and 2) pressure loading from the 2-D CFD simulation, icing effects are considered by using the iced airfoil shape.Comprehensive rotor broadband noise measurements are carried out on rotor blades with different roughness sizes and rotation speeds in two facilities: the Adverse Environment Rotor Test Stand (AERTS) facility at The Pennsylvania State University, and The University of Maryland Acoustic Chamber (UMAC). In both facilities the measured high-frequency broadband noise increases significantly with increasing surface roughness heights, which indicates that it is feasible to quantify helicopter rotor ice-induced surface roughness through acoustic measurements. Comprehensive broadband noise measurements based on different accreted ice roughness at AERTS are then used to form the data base from which a correlation between the ice-induced surface roughness and the broadband noise level is developed. Two parameters, the arithmetic average roughness height, R_a, and the averaged roughness height, based on the integrated ice thickness at the blade tip, are introduced to describe the ice-induced surface roughness at the early stage of the ice accretion. The ice roughness measurements are correlated to the measured broadband noise level. Strong correlations (absolute mean deviations of 9.3% and 11.2% for correlation using R_a and the averaged roughness height respectively) between the ice roughness and the broadband noise level are obtained, which can be used as a tool to determine the accreted ice roughness in the AERTS facility through acoustic measurement. It might be possible to use a similar approach to develop an early ice accretion detection tool for helicopters, as well as to quantify the ice-induced roughness at the early stage of rotor ice accretion. Rotor broadband noise source identification is conducted and the broadband noise related to ice accretion is argued to be turbulent boundary layer trailing edge (TBL-TE) noise. Theory suggests TBL-TE noise scales with Mach number to the fifth power, which is also observed in the experimental data. The trailing edge noise theories developed by Ffowcs Williams and Hall, and Howe both identify two important parameters: boundary layer thickness and turbulence intensity. Numerical studies of 2-D airfoils with different ice-induced surface roughness heights are conducted to investigate the extent that surface roughness impacts the boundary layer thickness and turbulence intensity (and ultimately the TBL-TE noise). The results show that boundary layer thickness and turbulence intensity at the trailing edge increase with the increased roughness height. Using Howes trailing edge noise model, the increased sound pressure level (SPL) of the trailing edge noise due to the increased displacement thickness and normalized integrated turbulence intensity are 6.2 dB and 1.6 dB for large and small accreted ice roughness heights, respectively. The estimated increased SPL values agree well with the experimental results, which are 5.8 dB and 2.6 dB for large and small roughness height, respectively.Finally a detailed broadband noise spectral scaling for all measured broadband noise in both AERTS and UMAC facilities is conducted. The magnitude and the frequency spectrum of the measured broadband noise are scaled on characteristic velocity and length. The peak of the laminar boundary layer vortex shedding (LBL-VS) noise coalesces well on the Strouhal scaling in those cases. For the measured broadband noise from a rotor with relatively large roughness heights, no contribution of the LBL-VS noise is observed. The velocity scaling shows that the TBL-TE noise, which is the dominant source mechanism, scales with Mach number to the fifth power based on the absolute frequency. The length scaling shows that the TBL-TE noise scales well on the absolute roughness height based on Howes TE noise theory.
Author:
Publisher:
ISBN:
Category : Aeronautics
Languages : en
Pages : 704
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Author: Wade H. Shafer
Publisher: Springer Science & Business Media
ISBN: 1461573912
Category : Science
Languages : en
Pages : 386
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Book Description
Masters Theses in the Pure and Applied Sciences was first conceived, published, and disseminated by the Center for Information and Numerical Data Analysis and Synthesis (CINDAS) * at Purdue University in 1957, starting its coverage of theses with the academic year 1955. Beginning with Volume 13, the printing and dissemination phases of the activity were transferred to University Microfilms/Xerox of Ann Arbor, Michigan, with the thougtit that such an arrangement would be more beneficial to the academic and general scientific and technical community. After five years of this joint undertaking we had concluded that it was in the interest of all con cerned if the printing and distribution of the volumes were handled by an interna tional publishing house to assure improved service and broader dissemination. Hence, starting with Volume 18, Masters Theses in the Pure and Applied Sciences has been disseminated on a worldwide basis by Plenum Publishing Cor poration of New York, and in the same year the coverage was broadened to include Canadian universities. All back issues can also be ordered from Plenum. We have reported in Volume 31 (thesis year 1986) a total of 11 ,480 theses titles trom 24 Canadian and 182 United States universities. We are sure that this broader base tor these titles reported will greatly enhance the value ot this important annual reterence work. While Volume 31 reports theses submitted in 1986, on occasion, certain univer sities do re port theses submitted in previousyears but not reported at the time.
Author:
Publisher:
ISBN:
Category : Aeronautics
Languages : en
Pages : 654
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Author: National Aeronautics and Space Administration (NASA)
Publisher: Createspace Independent Publishing Platform
ISBN: 9781722388706
Category :
Languages : en
Pages : 64
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Book Description
The Helicopter Icing Consortium (HIC) conducted one of the first U.S. tests of a heavily instrumented model in the controlled environment of a refrigerated tunnel. In the Icing Research Tunnel (IRT) at NASA LeRC, ice was accreted on the main rotor blade of the BMTR-1 Sikorsky model helicopter under a variety of environmental conditions, such that liquid water content (LWC) and volume mean droplet diameter (VMD) ranges reflected the Federal Aviation Agency and Department of Defence icing condition envelopes. This report gives the correlated results of the data provided by NASA LeRC. The method of statistical analysis is discussed. Lift, thrust, and torque coefficients are presented as a function of icing time, as correlated with changes in ambient temperature, LWC, and VMD. The physical significance of these forces is discussed. Korkan, Kenneth Unspecified Center...
Author: Robert J Flemming
Publisher: SAE International
ISBN: 0768081890
Category : Technology & Engineering
Languages : en
Pages : 122
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Book Description
The effects of inflight atmospheric icing can be devastating to aircraft. Universities and industry have been hard at work to respond to the challenge of maintaining flight safety in all weather conditions. Proposed changes in the regulations for operation in icing conditions are sure to keep this type of research and development at its highest level. This is especially true for the effects of ice crystals in the atmosphere, and for the threat associated with supercooled large drop (SLD) icing. This collection of ten SAE International technical papers brings together vital contributions to the subject. Icing on aircraft surfaces would not be a problem if a material were discovered that prevented the freezing and accretion of supercooled drops. Many options that appeared to have promising icephobic properties have had serious shortfalls in durability. This title addresses, among other topics, the measurement techniques and the drop physics that apply to icing, certification for flight through ice crystal clouds and in supercooled large drops, improvements in predictive techniques, scaling methods, test facilities and techniques, and rotorcraft icing.
Author: Edward Rocco
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
The simulation of icing conditions is sought for potential aircraft certification,and therefore test facilities that can generate conditions able to reproduce theice accretion phenomena are necessary. The icing conditions that aircraft endureare outlined in The Federal Aviation Administration regulations for airframe icingas described in Federal Aviation Regulation (FAR) 14 Part 25 Appendix C andPart 33 Appendix O. Multiple icing facilities exist for FAR 14 Part 25 AppendixC conditions, however developing facilities that can replicate super-cooled largedroplet (SLD) clouds and bi-modal SLD clouds (cloud with concentrations ofAppendix C and SLD conditions often observed in flight test) related to AppendixO is difficult due to the shortcomings of horizontal wind tunnels when generatingSLD particles (gravity effects on the large droplets). In the presented research effort,The Adverse Environment Rotor Test State (AERTS) at Penn State is assessedas a low-cost alternative to horizontal wind tunnels for the reproduction of SLDconditions. Current ice modeling techniques are also investigated for SLD regimes,existing Appendix C ice scaling techniques are evaluated in the SLD regime, andbi-modal SLD cloud impingement limits and ice shapes are investigated. Mentionedevaluation of ice accretion modeling tools is conducted via ice shape correlationsbetween experimental result and predictions.Firstly, the AERTS facility was calibrated in the SLD regime. Median VolumeDiameter (MVD) and Liquid Water Content (LWC) are the test parametersnecessary to calibrate for the reproduction of flight conditions. Phase DopplerInterferometer (PDI) data of cloud MVD was used to demonstrate that the existingnozzle spray system can provide relative MVD control of an SLD cloud. LWCcalibration is generally achieved in an icing facility utilizing a rime ice shape toensure freezing fractions close to unity (all encountered droplets freeze on impactwithout splashing or flowing aft). A rime shape in the SLD regime is unachievabledue to large particle splashing, and thus the effect splashing has on effective collectionefficiency must be considered in the LWC calculation. LEWICE, the nationsstandard ice prediction software, contains a droplet splashing model based on lowspeed test data (20 m/s). The LEWICE splashing model, coupled with a literaturebased empirical LWC adjustment, necessary due to test speeds beyond the 20 m/slimit, was utilized to effectively calibrate the LWC in the AERTS facility within16%.Secondly, ice shape modeling software known to be valid in Appendix C conditionswere assessed in the SLD regime. LEWICE, with and without an improvedheat transfer model (known as the AERTS prediction) was compared to six (6)AERTS test cases, three (3) of which had literature reference shapes. Overall, theAERTS test cases and literature reference case shapes were similar, but differencesin horn formation were observed. Overall, the ice prediction modeling tools werein agreement with the AERTS test cases, and the AERTS prediction providedimprovements in shape prediction when compared to LEWICE. When comparingthe deviation of the generated ice shapes to the prediction models, the AERTSprediction, on average, provided a 28.4% ice stagnation thickness prediction improvementsand 24.1% horn angle prediction improvements to LEWICE predictions.This is consistent with the prediction performance of LEWICE when including theheat transfer model improvements that were observed in previous, Appendix Ccondition, research efforts.Thirdly, ice condition scaling laws known to be valid in the Appendix C regimewere evaluated in SLD conditions. The modified Ruff scaling method was previouslytested at the NASA Glenn Icing Research Tunnel for SLD, but investigation of thescaling laws in other test facilities was requested to further understand SLD scaling.The results of this research, comparing six (6) scaling tests with the six (6) SLDtests previously mentioned, suggests that the ice scaling laws apply in the SLDregime as previously discussed in the literature. The mean deviation of stagnationthickness, horn angle, and horn protrusion of scale to reference test cases wereobserved to be 1.60%, 4.45%, and 1.46%, respectively. Furthermore, scalabilitydid not appear to degrade despite a large range of MVD, LWC, temperature, andspeed tested.Finally, a bi-modal cloud was studied in the SLD regime. The AERTS facilitywas modified with two independent cloud spray systems to generate a bi-modalcloud. In an SLD cloud, ice impingement limits are farther aft than in Appendix Cconditions, which is of concern for de-icing system design. Therefore, impingementlimit behavior of bi-modal clouds often observed in nature, must be understood.Impingement limits are defined by collection efficiency; a function of particletrajectory and thus MVD. Therefore, the impingement limit of a bi-modal SLD cloud should be that of a unimodal SLD cloud of the same MVD. To assess theimpingement limit trend, four (4) conditions resulting in sixteen (16) tests and fortyeight(48) data points were executed. The SLD impingement limit being that of thebi-modal cloud was observed experimentally, with a -1.58% 8.44% mean deviationof the upper impingement limit to the LEWICE prediction of the SLD impingementlimit, and a -11.0% 8.41% mean deviation of the lower impingement limit to theLEWICE prediction. When observing shape trends in the bi-modal scenario, the iceshape qualities transitioned from the 0% SLD to the 100% SLD shape consistentlyas SLD cloud content was increased. When comparing the deviation of four(4)generated ice shapes to the prediction models, the AERTS prediction forecast, onaverage, 21.4% ice stagnation thickness prediction improvements, and 18.5% hornangle prediction improvements when compared to LEWICE prediction deviations.vi.
