1、SAE AIR*4090 90 8357340 OOSLOLL 2 W INTERNATIONLw 400 Commonwealth Drive, Wanendale, PA 15096-oOo1 AEROSPACE INFORMATION REPORT Submitted for recognition as an American National Standard AIR4090 Issued 1990-08-01 IGNITER CERAMIC ARC RESISTANCE TESTS FOREWORD In surface gap or shunted surface gap spa
2、rk igniters (reference ARP484 for definitions), the ceramic material separating the electrodes is subjected during usage to intense arc discharges along the outside surface. capacl tor di scharge pul ses may contain several thousand amperes peak wi thi n a few microseconds duration. The effects of f
3、uel and elevated pressures as experienced in $et engine applications are to compress the arc discharge into the surface of the ceramic, in a local path or lttrackl. Severe thermal gradients, elevated pressures, and negative thermal coefficients of electrical resistivity (for typical ceramic material
4、s) result in tendencies for the electrical discharges to occur within the surface layers of ceramic rather than along the external surface. In either case (surface or within), ceramic deterioration in the form of cracking, chipping, puncture, tunneling, or uniform surface erosion is a . result. Each
5、 of these Procedures herein have been used primarily for surface gap igniters (no semiconductor), or shunted surface gap igniters containing a surface coating type of semi conductor. may deteriorate very rapidly with these procedures. A primary objective of component testing described herein is to p
6、rovide an indication of consistent qual i ty for ceramic material known to perform adequately in the engine application. A secondary objective is to provide a basis for comparison of different materials even though it must be recognized that superior performance in this testing does not assure succe
7、ss in the application. performance in this test, of itself, may not represent poor performance in the appl ication. Igniters contai ni ng a homogenous body type of semi conductor Poor CAE Technical Board Rules provide that: This report is published by SAE to advance the stak of technical and enginee
8、ring sciences. The use of this report is entirely voluntary, and its applicability and suitability for any particular use, including any patent infringement arising therefrom, is the sole responsibilitv of the user, - B SAE reviews each technical report at ieas every written comments and suggestions
9、. five years , at which time it may be reaff irmed, revised, or cancelled. CAE invites your Copyright i 990 Society of Automotive Engineers, Inc. All nghts resewed. Printed in U. S A. SAE AIR*K4090 90 W 83573LiO 005LOL2 K4 m *AC JT SAE AIR4090 . . 1. 1.1 2. 2.1 2.2 SCOPE: This report describes basic
10、 methods, typical results, 1 imitations, and technical variables which may provide some relative performance expectations for different lots of the same material, or comparison characteristics for different materials. This testing alone does not assure satisfactory operation in the engine, !.e., the
11、re is not a direct relationship to actual engine performance. Purpose : This report provides specific information on procedures for evaluating, on an accelerated compari son basi s , the durabi 1 i ty of cerami c materi al s under conditions of compressed electrical (capacitor) discharge, DESCRIPTIO
12、N OF TEST EQUIPMENT AND TEST PROCEDURE: The test procedures described in this report both involve sparking the test specimen immersed or submersed in a fluidic material. The fluidic material simulates compressed gases of engine applications. Three kinds of fluidic materials have been used: silicone
13、fluid, and 2) very fine mineral powders, which behave as a fluid, and 3) water. For purposes of this report, dielectric oils shall be henceforth termed Class 1, powder methodology is termed Class 2, and water usage is termed Class 3. CAUTION: 1) dielectric oils such as transformer oil or Testing sho
14、uld be conducted within a protection chamber or behind a protective shield to insure safety of testing observer(s1. The power source used to produce the sparking of the test specimens shall be a capacitor discharge exci ter and connecting lead capable of continuous duty operation. The peak cwent per
15、 di-scharge shall be at least 1300 A, and the time duration of each discharge shall be 20 to 100 ps. shall be as rapid as is compatible with discharge counting by audible or optical means, normally within a range of 1 to 5 per second. currents may accelerate.the test, but increase electrode melting.
16、 same exci ter type and same discharge parameters for comparing successive tests. The discharge rate Use the Higher peak 2.2.1 Test data for this method should describe the foregoing discharge parameters, as well as polarity of the discharge and whether unidirectional or oscillatory (reference AIR78
17、4 for terminology). 2.2.2 Output voltage of the exciter used for testing shall have some relevance to the intended application. voltage levels of at least 15 kV peak are recommended. materi al s, vol tage level s of 2000 to 5000 V are more appropriate. Particular test data should include the voltage
18、 level used. For insulators in high tension systems, For semiconductor -2- SAE AIR*b090 90 M 8357340 0051013 b E SAE AIR4090 2.3 Class 1 (Oil) Procedure: Mount the igniter with the sparking end immersed to a depth of 1/2 inch in the selected oil. It will be necessary to fashion a tight fitting inter
19、face between the igniter and the oil container, in order to prevent excessive oil , leakage. Figure 1 shows a typical installation. A container of resilient polymer is preferred, since the intense shock waves generated during testing can fracture glassl ,-IGNITER TIP INTERFERENCE FIT OR GASKETEDT AI
20、RFLOW 1 AIR L AIR VOLUME TO BE AT LEAST 50% OF FLUID VOLUME -1 - -1- - 1 UrF- H TIGHT FITTING -LID SILICONE FLUID. y 475 MILLIL MINIMUM ,ITERS &-CONTAINER, TRANSPARENT OR TRANS LUC EN T FIGURE 1 - Class 1 (Oil) Setup 2.3.1 Silicone fluids such as GE SF96, SF97, or Dow Corning 200 or 300 are preferre
21、d due to noncombustibility of the liquid (electrical arcing in the fluid does create combustible gases), high dielectric strength, compressibility, and minimal carbon forming characteristics. Even with silicone fluids, however, the liquid will quickly become blackened with carbon-like particulates s
22、uspended in solution. Maintenance of the test fluid should take into consideration changes in electrical conductivity as measured at 1000 V DC, as well as possible yellowish flame indications which may develop in the airspace within the test chamber during the course of testing. Any detectable chang
23、e in fluid conductivity at 1000 V DC and 0.050 in gap electrodes is a basis for fluid changes. I -3- SAE AIR*4090 90 8357340 005LOL4 8 a SAE AIR4090 2.3.2 Due to the high dielectric strength of the test oils, it may be necessary to induce sparking during testing of insulator materials by initial and
24、 periodic addition of graphite (pencil lead) or graphite petrolatum to the sparking surface of the ceramic. All such operations should be recorded. 2.3.3 Due to creation of oil vapors or decomposed gaseous products of sparking which may be combustible, the sparking should be closely observed, and fl
25、uld replaced in event of increases in shock wave pressures (see Figure 11, or, in event OP noticeable increases in yellowish flame attend1 ng each spark. CAUTION: Electrical arcing in the silicone Pluld produces combustible gases, which may ignite if not properly vented during testing. It is mandato
26、ry that the air in the test contalner or the fluid be changed as required to prevent an explosion, 2.4 Class 2 (Powder) Procedure: Mount the igniter with the sparking end facing up arid inserted in the base OP a tight fitting funnel, with any cooling holes masked. Pour in sufficient powder to cover
27、the electrodes to a depth such that some powder Is displaced on the surface by each discharge, but just short of the point where no surface disturbance is observed per each discharge. a typical setup. Figure 2 shows -I- .II- FIGURE 2 - Class 2 (Powder) Setup SAE AIR*qOSO 90 W 8357340 005LOL5 T P SAE
28、 AIR4090 2.4.1 AL203 of a purity at least 96% and particle size of 50 to 100 vm is recommended, due to similarity to most igniter insulator material. must be free flowing. 2.4.2 Powder replacement shall be performed after completion of each test. 2.4.3 Use of powders other than AL2O3, or blends of o
29、ther powders with AL203 is an available option. It has been found that semiconductive powder such as silicon carbide, even in small portions of a blend, tends to increase the sparking at one particular location, which promotes electrode melting. Powder 2.4.4 Additional mechanical agitation during Cl
30、ass 2 testing may be desired, in which case vibration of the entire igniterlcontainer assembly is permissible. An alternative agitation setup can involve immersion of the igniter test part in a fluidized bed apparatus. If agitation other than that from sparking is employed, results of the testing sh
31、all contain sufficient description so as to permit repeatability in another setup. 2.5 2.6 Class 3 (Water) Procedure: Mount the igniter to a depth of 112 inch in the water selected (see Figure 3). The test equipment is basically the same as the oil setup. It has been found that distilled water or de
32、ionized water may contribute to ionizing difficulty for particular systems. Tap water produces the most consistent spark action. greatly, it is recommended that the water used be distilled water to which drop or two of ascetic acid be added so as to result in an electrical conductivity in the range
33、of 500 to 5000 prlcrn, However, since tap water composition may vary Choice of Procedure (Class 1 versus Class 2 versus Class 3) involves consideration of advantages and disadvantages of each as well as possible application variables. The foll.owing list summarizes some for each: a. Class 1 (Oil) Ad
34、vantages 1. 2. Oil continually clears away arcing debris More even distribution of sparking b. Class 1 (Oil) Disadvantages 1, May require graphite or graphite-petrolatum addition to t spec1 men. t 2. Messy. May lastingly impregnate test specimen. 3, Reducing atmosphere may not match application. 4.
35、Caution is needed with respect to gases generated by spark decomposition of the oil. While the oil itself may not burn, the gases generated can reach an explosive concentration. SAE AIR*4030 90 a 8357340 005L016 L SA AIR4090 AIR VOLUME TO BE AT LEAST 50% OF FLUID VOLUME 2.6 (Continued): IGNITER TIP
36、VENT TIGHT FITTING -+- LID J WATER - - (CONTROLLED .- CONDUCTIVITY) 475 MILLI LITERS MINIMUM - - NONBRITTLE c CONTAINER, TRANSPARENT OR TRANSLUCENT FIGURE 3 - Class 3 (Water) Setup c, Class 2 (Powder) Advantages 1, Allows exposure to air (oxygen) during testing. 2. Convenient 30 Does not require add
37、ition of semiconducting material. do Class 2 (Powder) Disadvantages 1. Tends to concentrate arcing in smaller location(s). 2, May require more cleaning to expose tested surface. e. Class 3 (Water) Advantages 1. 2, No special cleaning required after test. Easiest to set up and maintain f. Class 3 (Wa
38、ter) Disadvantages 1, More careful controls needed on fluid conductivity. -b- SAE AIR4090 3. INTERPRETATION OF RESULTS: 3.1 The testing objective is the amount (number of pulses) of discharge-caused deterioration prior to reaching an unacceptable condi tion. conditions include cracking, chipping, or
39、 localized erosion or changes in by ultrasonic procedure for Class 1 or by abrasive particle blast for Class 2, prior to surface examination. semiconductor type materials. Unacceptable . material resistivity. It may be necessary to clean the test surface such as Do not use abrasive cleaning on 3.2 Another possible objective is to assess the degree of discharge-caused deterioration for a given number of pulses, or pulse time, for comparison of several ceramic materials or several lots of the same material. PREPARED BY SAE COMMITTEE E-30, PROPULSION IGNITION SYSTEMS -7-
