Electro-Impulse De-Icing Testing Analysis and Design, Exams of Design

Download Electro-Impulse De-Icing Testing Analysis and Design and more Exams Design in PDF only on Docsity!

OIC

HII

TABLE OF CONTENTS

CHAPTER I PAGE

THE EIDI DEVELOPMENT PROJECT

iii

TABLE OF CONTENTS

 - II. The Basic Principles I. Introduction I - III. Prior History - IV. The NASA/WSUIIndustry Project - A. Initial Feasibility Demonstration - B. The Industry Consortium - C. Objectives - V. References - CHAPTER - I. Introduction ELECTRODYNAMIC STUDIES AND TESTS - II. Approximate Characteristics of the Discharged Circuit - III. Ballistics Pendulum Studies - IV. Magnetic Field Diagnostics Experiment - B.A. Experimentalk_agnetic Field Apparatus Measurements - C. Eddy Currents - D. Pressure on the Target - E. Total Normal Force and Impulse - F. Radial Forces in the Target - V. Electrody namic Modeling - A. Summary of Modeling Approaches - B. Details and Results of Henderson's Model - C. Details and Results of the Bernhart-Schrag Model - VI. Coil Impedance Data - A. Skin Effect Within the Coil - B. Coil Impedance Tables and Graphs 

• VII. Design Examples
  • VIII. References
  • CHAPTER TABLEOF CONTENTS - I. Introduction STRUCTURAL DYNAMIC TESTS AND STUDIES - II. Strain Measurements Near EIDI Coils
  • III. Boeing (BCAC) 767 Leading Edge Slat Strain - IV. Semi-Cylinder Leading Edge Investigations - A. Experimental Results - B. Analytical Studies (Idealized Boundary Conditions) - C. Analytical and Experimental Results - V. Observations and Conclusions
    • VI. Referenoes
  • CHAPTER - I. Coil Wire Rolling FABRICATION TECHNIQUES - II. Coil Making - III. Coil Mounts - IV. Electrical Leads - V. Measuring System Performance
    • VII. Weight Estimates VI. Outline of Method 27_
• VIII. Coil Attachment - IX. Icing Tunnel Models - X. Test Model Instrumentation - I. Oct. 25 - Nov. 5, 1982 Tests CHAPTERICING TUNNEL 5 TESTS - A. Two Models Tested - B. Test Descriptions - C.D. MajorParticipants Results ......................and Conclusions
  • II. April 18-22, 1983 Tests - A. Two Models Tested - B. Test Descriptions - C.D. MajorParticipants Results ......................and Conclusions
• III. August 15-18, 1983 Tests - A. One Model Tested - B. Test Descriptions - C. Results and Major Conclusions - D. Participants - IV. November 7-9, 1983 Tests - A. Two Models Tested - B. Test Descriptions - C.D. _jorParticipants Results ......................and Conclusions - V. May 14-23, 1984 Tests - A. Four Models Tested - B. Test Descriptions - C.D. MajorParticipants Results ......................and Conclusions - VI. August 13-17, 1984 ' • - A. Three Models Tested - B' Test Descriptions - C. Major Results and Conclusions - D. Participants - VII. Sept. 17-21, 1982 Tests TABLE OF CONTENTS - A. Two Models Tested - B. Test Descriptions - C. Major Results and Conclusions - D. Participants
• VIII. Nov. 26 - Dec. 4, 1984 Test - A. Six Models Tested - B. Test Descriptions - C. Major Results and Conclusions - D. Participants - IX. June 12-19, 1985 Test - A. Three Models Tested - B. Test Descriptions - C. Major Results and Conclusions - D. Participants 3! - X. Sept. 10-16, 1985 Tests - XI. References
  • CHAPTER - I. NASA Icing Research Aircraft FLIGHT TESTS - B.A. EquipmentTest Procedures Used - C. Results - D. Conclusions - II. Cessna TV 206 Flights (1984) - A. Equipment Used - B. Test Procedures - C. Tanker Ice - D. Natural Ice - E. EMI-RFI - F. Noise
    • III. Other Flight Experience G. Conclusions 33! - A. Cessna - B. Boeing - IV. References

CHAPTERI. THEEIDI DEVELOPMENTPROJECT

I___.Introduction Ice accumulation on aircraft wings in flight has been a danger since the earliest days of flight. The total accumulation needs not be large to be fatal. Although ice normally is accrued on frontward facing surfaces only, giving a few centimeters thickness on the front 2 percent of the wing chord, this is enough to cause flow separation and destroy lift, particularly if the aircraft slows or maneuvers. Also, drag may increase enough to exhaust fuel reserves or destabilize the flight. Helicopter rotors are even more vulnerable to the detrimental effects of ice, and engine inlet diffusers require icing protection to a greater degree than lifting surfaces. This need brought the NASA Lewis Research Center into aircraft icing research almost from its start.

Although several methods of de-icing or anti-icing are available, all have some undesirable aspects in regard to energy requirements or effective- ness. A method suggested (Ref. I-I) as early as 1937 offers an alternative which has not been adequately developed. The electro-magnetic impulse phenomenon has been used for metals forming, and holds the promise of ice removing with very low energy, minimal maintenance (no moving parts), great reliability, and weight and cost competitive with existing methods. This report summarizes work done under a NASA-Lewis grant to develop the Electro-Impulse De-Icing (EIDI) system. Wichita State University has been the grant recipient, charged with researching the phenomena to provide the underlying technology, and also with coordinating the efforts of a team of participating industries. The program has consisted of basic analyses, laboratory tests, icing tunnel tests and flight tests. After five years,

The coils are connected by low resistance, low inductance cables to a high voltage capacitor bank, and energy is discharged through the coil by a remote signal to a silicon-controlled-rectifier ("thyristor"). Discharge of the capacitor through the coils creates a rapidly forming and collapsing electro-magnetic field which induces eddy currents in the metal skin. The fields resulting from current flow in the coil and skin create a repulsive force of several hundred pounds magnitude, but a duration only a fraction of a millisecond. A small amplitude, high acceleration movementof the skin acts to shatter, debond and expel the ice. Two or three such "hits" are performed sequentially, separated by the time required to recharge the capacitors, then ice is permitted to accumulate until it again approaches an undesirable thickness.

Figure I-I also shows "doublers," unalloyed aluminum discs, slightly larger than the coils, bondedto the skin opposite the coil. These are used when the skin thickness is less than the minimum required to provide adequate conductance for the eddy currents. Composite, non-metallic, leading edges require a similar special treatment. A fundamental study of the phenomenaand parameters for electro-impulse was undertaken to provide a basis for such geometric and electrical design choices. Prof. R. L. Schrag of Wichita State University has led this study which is presented in Chapter

2. Ref. I-2 reported initial results of this work, and Ref. 1-11 summarizes the final form of the computer modeling and its validations.

3

ENERGY STORAGE__ CAPACITOR

TRIGGER

THYRISTOR

DIODE CLAMP IMPULSE COIL

Fig. I-2 Basic Circuit In Figure I-2, the basic circuit is illustrated. An electro-impulse is initiated by supplying a trigger pulse to the thyristor, allowing the capac- itor to discharge through the coil. A typical current waveform is shown in Figure I-3. Since a thyristor has diode properties, the current follows the first positive loop of the RLC response, after which the thyristor re-opens the circuit. This leaves the capacitor reverse-charged. Such reverse charging reduces capacitor llfe substantially. For that reason a clamping diode is placed across the capacitor. A typical current and resulting skin displacement are shown in Figure I-3.

MAGNETIC

FIELD _ EDDY

tt 1..... ®

t COIL

Fig. I-4 Coil Magnetic Field Pattern and Resulting Eddy Currents When the aircraft skin moves in response to the electro-impulse force the coil-to-skin gap changes and that modifies the magnitude of the proximity influence. In addition, the skin's movement relative to the coil's magnetic field further modifies (by motional induction) the electro- motive forces that drive the eddy currents. These influences due to skin motion are, however relatively small because of the time delay involved in the motion, and appear to be negligible when the skin is ice loaded. The assertion is, in effect, that the coil current and the strength of the force impulse may be calculated without the need to also analyze the complex structural response. This is discussed in detail in Chapter 2.

Figure I-5 shows a wing with coils placed spanwise, separated by about 0.4 meters. These are all supplied by a single power unit. A more effec- tive modified version is shown in Fig. I-6. Energy requirements are small,

being comparable to those typical of landing lights for the same size air- craft. De-icing has been accompliahed in the icing wind tunnel and in

flight for typical general aviation and transport wings under a wide range of velocities, angles of attack, icing rates and temperatures.

TRANS_I

PROGRAMMED8WITCHING -_

Fig. I-5 Electro-Impulse Coils Installed in a Wing

COILSt /

SEQUENCE CONTROLLER^ FIRING -i^ %.- -^ '

-THYRISTERS CAPACITOR TRANSFORMER _ HIGH VOLTAGE, HIGH CURRENT LI:;ES .... HIgH VOLTAGE, LOW CURRE_;T LI_!S ........ LOW VOLTAGE, LOW CURRENT LINE Fig. I-6 EIDI("Odds with andSeries-Connected Evens") Coils

Eleven sets of icing tunnel tests have been essential to the system development. The unique capabilities of the NASA-Lewis Icing Research Tunnel (IRT) provide testing conditions for confident evaluation of the system in flight. Chapter 5 summarizes the IRT tests and results. Reference I-4 reports in more detail the engine nacelle and large wing testing. Reference I-9 give additional engine nacelle work. Chapter 6 gives a brief account of the two flight test programs. These were earlier reported in References I-5 and I-6. Finally, Chapter 7 describes systems tests for fatigue of skin or EIDI components and electro- magnetic interference with other aircraft systems." Design methodology was summarized in Reference 1-10.

Ill. Prior History The use of electro-magnetic impulse force to remove ice was first suggested by Rudolf Goldschmidt, a German national residing in London before World War II. He was granted a patent (Ref. I-I) and a series of patent extensions in 1937 through 1939. His patents, now expired, anticipated most of the applications now being used or considered. However, there is no evidence that Goldschmidt ever attempted to build the devices he imagined. During the 1950's and 1960's, electro-impulse methods were used for metals forming in various industrial processes, but no record can be found of the use for de-lclng until researchers in the USSR either discovered Goldschmidt's patents or rediscovered this application independently. In 1965, I._ Levin in the Soviet Ministry of Power and Electrification, seeking methods for cleaning frozen and sticky materials from surfaces (coal bunkers, transformer boxes, towers, etc.) published work on electro-impulse possibilities. He immediately received inquiries from other ministries

(aviation, fisheries, dairy, housing) regarding de-icing of vehicles, build- ings, ships, and for cleaning of dry milk from hoppers (Ref. I-7 and I-8). Responding to their requests involved him in bureaucratic territorial struggles and he was fired. Eventually, however, he was set up in his own laboratory u_der the State Committee for Meteorology and Environmental Monitoring, and apparently made some installations in aircraft; the Ii- has been cited as having been the first, but confirmation by Western observers is difficult to obtain.

In any case, in the early 1970's, Russian representatives were granted EIDI patents in several Western nations, including the USA, and USSR sales- men began calling on American and European aircraft companies offering to sell their design and construction services for an EIDI system. Their lack of candor discouraged most customers, but interest was stirred and during the 1970's, work was done on this method in France (Air-Equipment division of DBA), Great Britain (Lucas Aerospace and B.A.C.), and the United States (Lockheed and McDonnell-Douglas). For various reasons, the development stopped short of full implementatior_ The system still lacked a well developed underlying technology and known design parameters.

IV. Th___eeNA_A/WSU/Industry Project

A. Initial Feasibility Demozstration In mid-1982, NASA Lewis Research Center funded a six-month grant to Wichita State University to work with two small plane makers, Beech and Cessna, and an aircraft electrical system manufacturer, the Engine Systems Division of Simmonds-Precision, to do a feasibility study resulting in an icing tunnel demonstration in Oct.-Nov. 1982. Two wing sections were tested, mid-wing portions from a Beech Bonanza and a Cessna 206. These 10