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# OAR Box 1878 Prepped by Charmelle Mathews



## Document

Number: 

# 72 ) 11-1- 2 Docket Number: 

# A-90-1 9

Printed 11/28/20081:21:24

PM Sheet 72 of 145

## EP AAI R DOCKE T 

# Nort h America n COMBUSTIO

N HANDBOO

K

A Basi c Referenc e o n th e Ar t an dScienc e o

f Industria l Heatin g wit hGaseou s an dLiqui dFuel s

SecondEdition

Notfc * Thi s materia l mayb e protecte d ftf

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w'T f2 1 7 U.S . Code

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## NORTH AMERICA N Mfg . Co . CLEVELAND . OHI O 4410 5 US A 

# © 

# miFUEL-BURNIN GEQUIPMEN T 26 9 n g flow 0 chec k lam e g o ngerou s r unles s mtdoor s Ie nois e e nois e that'o f ; helps . 1 o f th e •ilo fue l Xr. an d istanti v e n an d te r th e movie s !s . an d kin g a t s . (Se n ; (mos t i e flow i s pro woul d • r wit h i n . bu t exces s il v th e

• h nai r 'r l fue l s doe s

•hn n th r '40 0 fp s onl H b o •viHnnrn Th e maximu msoun dleve l i s usuall y a t stoichiometri c fuel/ai r rati o o r jus t slightl y rich ; an dthi s pea k soun dleve l move s t o alowe r frequenc y (pitch ) an dlowe r

amplitud e (volume ) fo r al l othe r

fuel/ai r ratios . If

aconstan t tota l flo w rat e wer e maintaine dthroug hapremi x flame , th e nois e productio n woul db e cu t

i n hal f ( 3 d B less ) a t

th e lea n an dric hlimit s o f flammability . Fo r premi x flames , turbulenc e intensit y ca n distur b aflam e an dcaus e i t t o mak e mor e noise : s o orifices , valves , an dfitting s shoul db e locate dfa r upstrea mt o allo w th e turbulenc e t o deca y befor e th e strea menter s th e flame . Fo r nozzle-mi x flames , th e minimu mnois e an dmos t compac t

flam e ar e usuall y achieve dwhe n th e combustio n are aan dth e zon e o f maximu m turbulenc e ar e th e same , whil e usin g th e larges t possibl e ai r

an dfue l ports . I f th e availabl e momentu mi s no t use dfor

effectiv e mixin g withi n th e combus

tio n area , th e volumetri c rat e o f combustio n (intensity ) wil l b e low ; bu t if th e turbulen t

zon e exceed s th e combustio n area , exces s nois e wil l result . Th e geometr y o f

aburner' s refractor y til e ma y se t u p stron g natura l mode s o f

oscillation , amplifyin g combustio n roar , an dcausin g peak s a t th e natura l acousti c frequencie s o f th e ga s i n th e tile . Th e natura l acousti c frequenc y o f

alarge r

til e i s lower . Th e us e o f sound-absorbin g materia l fo r th e til e ma y lowe r

th e soun dleve l b v 5 o r 1 0 d B a t

frequencie s abov e 60 0 Hz . Th e basi c soun dspectru mgenerate db y aflam e ca n b e altere db y th e acousti c characteristic s o f th e flui dpipin g systems , th e furnace , and/o r th e room . Superturbulen t

combustio n nois e i s aspecia l cas e o f combustio n roa r associate dwit hunstabl e flame s an devidence db y asudde n jum p i n th e soun dpressur e level . Thi s result s fro mth e increase dturbulenc e i n th e unstabl e operatin g mode . A n exampl e o f suc ha n unstabl e mod e occur s whe n aflam e fluctuate s betwee n typ e 2 an dtyp e 3 o f Figur e 6.2 . Also , a 5 d B jum p wa s note dwhe n areductio n i n swir l o f atyp e 3 flam e cause di t t o detac hfro mth e tile . Changin g th e oi l spra y angl e relativ e t o th e burne r til e angl e ha s ha dsimila r results . Firin g aburne r beyon dit s rate drang e ma y d o likewise . Combustion-drive n osci/Jnfion s resul t whe n som e feedbac k mechanis m produce s oscillation s tha t lea dt o avariabl e hea t release , th e timin g o f whic hi s suc htha t

i t add s energ v t o subsequen t oscillations . A s a n example , apulsatin g blowe r

no t onl y generate s noise , bu t provide s amechanis mfo r combustio n drive n oscillations . Anothe r i s th e alternat e vorte x sheddin g behin dabluf

f body . Combustion-drive n oscillation s hav e ahighe r frequenc y tha n combustio n roa r an dthe y hav e narro w peak s o f frequenc y a s oppose dt o th e broa d spectru mo f

combustio n roar .