During two entries in late 1989, a heavily instrumented sub-scale model of a helicopter main rotor was tested in the NASA Lewis Research Center (LeRC) Icing Research Tunnel (IRT). The results of this series of tunnel tests have been published previously. After studying the results from the 1989 test and comparing them to predictions, it became clear that certain test conditions still needed investigation. Therefore, a re-entry of the Sikorsky Aircraft Powered Force Model (PFM) in the IRT was instituted in order to expand upon the current rotorcraft sub-scale model experimental database. The major areas of interest included expansion of the test matrix to include a larger number of points in the FAA AC 29-2 icing envelope, inclusion of a number of high power rotor perfonnance points, close examination of wann temperature operations, operation of the model in constant lift mode, and testing for conditions for icing test points in the full scale helicopter database. The expanded database will allow further and more detailed examination and comparison with analytical models. Participants in the test were NASA LeRC, the U.S . Anny Vehicle Propulsion Directorate based at LeRC, and Sikorsky Aircraft. The model rotor was exposed to a range of icing conditions (temperature, liquid water content, median droplet diameter) and was operated over ranges of shaft angle, rotor tip speed, advance ratio, and rotor lift. The data taken included blade strain gage and balance data, as well as still photography, video, ice profile tracings, and ice molds. A discussion of the details of the test is given herein. Also, a brief examination of a subset of the data taken is also given. The results of this series of tunnel tests have been published previously. After studying the results from the 1989 test and comparing them to predictions, it became clear that certain test conditions still needed investigation. Therefore, a re-entry of the Sikorsky Aircraft Powered Force Model (PFM) in the IRT was instituted in order to expand upon the current rotorcraft sub-scale model experimental database. The major areas of interest included expansion of the test matrix to include a larger number of points in the FAA AC 29-2 icing envelope, inclusion of a number of high power rotor perfonnance points, close examination of wann temperature operations, operation of the model in constant lift mode, and testing for conditions for icing test points in the full scale helicopter database. The expanded database will allow further and more detailed examination and comparison with analytical models. Participants in the test were NASA LeRC, the U.S . Anny Vehicle Propulsion Directorate based at LeRC, and Sikorsky Aircraft. The model rotor was exposed to a range of icing conditions (temperature, liquid water content, median droplet diameter) and was operated over ranges of shaft angle, rotor tip speed, advance ratio, and rotor lift. The data taken included blade strain gage and balance data, as well as still photography, video, ice profile tracings, and ic...
A heavily instrumented sub-scale model of a helicopter main rotor was tested in the NASA Lewis Research Center Icing Research Tunnel (IRT) in September and November 1989. The four-bladed main rotor had a diameter of 1.83 m (6.00 ft) and the 0.124 in in) chord rotor blades were specially fabricated for this experiment. The instrumented rotor was mounted on a Sikorsky Aircraft Powered Force Model, which enclosed a rotor balance and other measurement systems. The model rotor was exposed to a range of icing conditions that included variations in temperature, liquid water content, and median droplet diameter, and was operated over ranges of advance ratio, shaft angle, tip Mach number (rotor speed) and weight coefficient to determine the effect of these parameters on ice accretion. In addition to strain gage and balance data, the test was documented with still, video, and high speed photography, ice profile tracings, and ice molds. This paper presents the sensitivity of the model rotor to the test parameters, and compares the results to theoretical predictions. Test data quality was excellent, and ice accretion prediction methods and rotor performance prediction methods (using published icing lift and drag relationships) reproduced the performance trends observed in the test. Adjustments to the correlation coefficients to improve the level of correlation are suggested in this paper.
Currently, an effort is being made by the NASA Lewis Research Center to develop an analytical procedure for calculating the performance degradation a helicopter experiences while operating in an icing encounter. A short discussion is given of the possibilities for performing such a calculation and reasons given for choosing the present approach. A complete description of the jobstream is given. Data taken from the NASA Lewis model rotor icing test program is used as a data base for comparison.Comparisons are also made between this method and the more traditional method based on empirical correlation.Conclusions are drawn as to how well results compare with experiment. Guidelines for calculation procedures are given. Limitations of this type of jobstream are pointed out and recommendations are made for future improvements. A complete analysis of the effects of an icing condition on the performance of a helicopter rotor includes prediction of the ice accretion, the aerodynamic penalties associated with the ice accretion, and ice shedding. The main thrust of this paper is the investigation of an analytical means of predicting the aerodynamic penalties associated with a given icing condition.In the past, aerodynamic penalties on the rotor have been predicted using an empirical relationship developed by Flemming.:The correlation has shown reasonable agreement with experimental data taken in the NASA Lewis Icing Research Tunnel 0RT). The Flemming correlation also has the advantage of being very simple.However, because it is a correlation derived from an empirical set of data, it may have some limitations in terms of general application to full scale rotors.Recent developments in areas of efficiency and grid generation have made Navier-Stokes analysis a viable option for the calculation of performance of iced airfoils. 2 However, in the present analysis, application of a Navier-Stokes code would be extremely unwieldy in terms of CPU time. This aspect will be discussed in more detail later. The Interactive Boundary Layer 0BL) analysis developed by Cebeci 3 shows a great deal of promise.It has an advantage over the Navier-Stokes analysis in that it requires no grid and is not computationany intensive. Thus, the IBL scheme was selected for investigation in the current work. Method of AnalysisPredicting the effects of an icing condition on the performance of a helicopter main rotor is a complicated task with several steps of calculation.A general outline of the required steps is given in flowchart form in Figure 1. Initially, the clean performance of the rotor is needed as a stariing point. Then, the ice accretion along the radius of the rotor is calculated.A check is done to see where and when, if any, natural shedding has taken place.Once the new geometry of the iced rotor is known, aerodynamic performance coefficients are calculated. Then, finally the new performance of the overall rotor is determined based on this information.In th e current analysis the various steps are performed by three major codes. Rotor ...
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