Compuestos

NASA T E C H N I C A L N O T E

NASA TN D-4730
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M-1 INJECTOR DEVELOPMENT -

PHILOSOPHY AND IMPLEMENTATION
by Walter F. Dankhofi Iruing A. Johnsen, E. William Colzrad, and William A. Tomazic
Lewis Research Center Cleveland, Ohio

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NATIONAL AERONAUTICS A N D SPACE A D M I N I S T R A T I O N

W AS H I N G T O N , D. C.

AUGUST 1 9 6 8

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TECH LIBRARY KAFB, NM

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M-1 INJECTOR DEVELOPMENT

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PHILOSOPHY AND IMPLEMENTATION

By W a l t e r F. Dankhoff, Irving A. Johnsen, E. William Conrad, and William A. Tomazic Lewis Research Center Cleveland, Ohio

NATIONAL AERONAUT ICs AND SPACE ADMINISTRATION
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For s a l e by the Clearinghouse for F ed e r a l Scientific and T e c h n i c a l lnformotion Springfield, V i r g i n i a 22151 CFSTl p r i c e $3.00

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ABSTRACT
T h e M-1 injector design was a cooperative effort between Aerojet-General Corpora­ tion and Lewis R e s e a r c h Center to achieve high performance with completely stable op­ eration. T h e approach was based on the technology already established inthe RL-10 and 5-2 engine development programs, supplemented with the latest data obtained a t NASALewis. Scall-scale t e s t s were conducted to verify design concepts p r i o r to incorporation into the full-scale hardware. Full-scale injector testing demonstrated that the design goals were achieved.

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M-1 INJECTOR DEVELOPMENT - PHILOSOPHY AND IMPLEMENTATION

by Walter F. Dankhoff,Irving A. Johnsen, E. William Conrad, and William A. Tomazic
Lewis Research Center SUMMARY
The M-1 injector was designed with the intent of circumventing the normal "cut-and try" development route by using all pertinent technology to design a satisfactory end product, that is, a n injector that combines high performance, stable operation, and dura­ bility. The approach employed was to make full useof all existing information and ex­ perience, to provide additional data (as required) through subscale testing, to employ analytical simulations t o provide guidance, and to utilize the highest level of technical competence available to a r r i v e at final design decisions. Full-scale injector testing demonstrated that the design goals were achieved. Com­ bustion efficiency was 96 percent atrated conditions. Vacuum specific impulse, ex­ trapolated from the basic test data was 429.5 pounds force second p e r pound m a s s (4212 N-sec/kg), which is equivalent to the PFRT engine specification. The injector was highly resistant to both hydraulic and acoustic instabilities. No instabilities of any s o r t were encountered at rated conditions. Low-level chugging occurred during the starttransient only. Acoustic instability was encountered only when the hydrogen inlet tem­ perature was dropped significantly below the engine operating value. The injector, the baffle, and the ablative chamber showed excellent integrity. Prolonged testing was pos­ sible without equipment repair o r replacement.

INTR0D UCT IO N
Injector development has historically been a prolonged, iterative process.The basic difficulty has been one of avoiding combustion instability, while at the s a m e time obtain­ ing high combustion performance. The problem has become more severe as engine size has increased. Lack of basic knowledge on instability, its prevention, and cure has gen-

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erally forced injector development along the tortuous path of cut-and-try, with its asso­ciated long delays and high costs. The injector becomes the pacing item in the engine de­ velopment and the remainder of the program m a r k s time and accrues costs until the injector problem is solved. In some engine programs, as many as 100 full-scale injector configurations have been investigated before a satisfactory design was achieved. Although the initial efforts on the M-1 program...