VEHICLE NOISE AND INFLUENCE OF THE COOLING FAN

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VEHICLE NOISE AND INFLUENCE OF THE COOLING FAN

V. Tandara

To cite this version:

V. Tandara. VEHICLE NOISE AND INFLUENCE OF THE COOLING FAN. Journal de Physique

Colloques, 1990, 51 (C2), pp.C2-277-C2-280. �10.1051/jphyscol:1990267�. �jpa-00230688�

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au

ler Congrds Fran~ais ~ ' A c o u s ~ ~ ~ u ~ 1990

VEHICLE NOISE AND INFLUENCE OF THE COOLING FAN

V. TANDARA

Technical Consulting, Development and Designing. Expert Witness for Combustion Machines and Reduction Noise of vehicles, D-1000 Berlin 19, POStfach 1323, F.R.G.

Abstract

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The combustion engine i s only one of many v e h i c l e n o i s e sources. Every combustion engine has i n n e r and e x t e r n a l n o i s e sources.

The c o o l i n g f a n s can be important n o i s e sources. They a r e i n s t a l l e d t o c o o l t h e engine, encasement and t h e i n s i d e of t h e c a r . The i n f l u e n c e of f a n s a r e g r e a t i n case of h i g h ambient temperature, low t r a , v e l l i n g speed and f r e q u e n t stoppages.

1

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INTRODUCTION

Various t y p e s of v e h i c l e s a r e t h e most important n o i s e sources i n t h e dwel- l i n g surroundings and t r a f f i c . The passenger c a r s p r e v a i l i n g i n t h e road t r a f f i c and a l s o u t i l i t y v e h i c l e s . Such u t i l i t y v e h i c l e s include f o r i n s t a n - c e , t h e load-carrying and t e r r a i n v e h i c l e s and buses f o r passenger t r a n s - p o r t a t i o n . I n a l l v e h i c l e s , two t y p e s of n o i s e occur, i . e . , t h e i n t e r n a l and e x t e r n a l n o i s e . ^{A l l}persons i n t h e c l o s e v i c i n i t y of t h e road a r e exposed t o t h e v e h i c l e e x t e r n a l n o i s e . The d r i v e r and t h e passengers a r e exposed t o t h e i n t e r n a l n o i s e .

The i n f l u e n c e of t h e v e h i c l e s on t h e noise l e v e l i n t h e dwelling surroun- d i n g s was r e a l i z e d i n t h e s e v e n t i e s when t h e e x i s t i n g l e g a l p r e s c r i p t i o n s were made more severe. During t h a t p e r i o d , new and considerably lower l i m i t v a l u e s were introduced. U n t i l 1980/1982 t h e l i m i t v a l u e s f o r e x t e r n a l n o i s e l e v e l of motor v e h i c l e s were very high. Whereas l i m i t i n g v a l u e s ^a90 ~ B ( A ) were allowed t i l l 1980/1982, v a l u e s about 75-80 dB (A) a l r e a d y expected f o r t h e f u t u r e .

2

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NOISE SOURCES OF VEHICLES

The most important n o i s e sources of v e h i c l e s a r e :

-

t r a n s m i s s i o n ,

-

t h e r o l l i n g n o i s e of t y r e s connected w i t h t h e q u a l i t y of pavement and t h e road surroundings,

-

t h e d r i v i n g u n i t ,

-

n o i s e r e s u l t i n g from streamings of a i r on t h e s u r f a c e of t h e v e h i c l e and i n t h e channels,

-

v i b r a t i o n s ,

-

t h e v e h i c l e body e t c .

For a long time t h e i n t e r n a l combustion engines a s d r i v i n g u n i t s had been regarded a s t h e most important n o i s e sources of v e h i c l e s . Ilndoubtedly i n c a s e of t h e l i m i t v a l u e s u n t i l 1980/1982, t h e combustion engine and t h e i r exhaust gas conduct were g r e a t e s t noise sources on t h e u t i l i t y v e h i c l e s . On t h e v e h i c l e s f o r which t h e e x t e r n a l n o i s e l e v e l i s reduced, o t h e r n o i s e

Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:1990267

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C2-278 COLLOQUE DE PHYSIQUE

s o u r c e s become o u t s t a n d i n g , p a r t i c u l a r l y t h e t r a n s m i s s i o n and r o l l i n g n o i s e of t y r e s . T h i s i s v e r y obvious i n F i g u r e 1 which g i v e t h e e x t e r n a l n o i s e l e -

" ~ : ? I : ? o i ~ P I ! % u c t i o n ~ I

v e h i c l e n o i s e w i t h o u t e n g i n e

4 0 6 0 8 0 k m l h

V E H I C L E S P E E D v

F i g . 1

-

E x t e r n a l n o i s e of t h e t e r r a i n - v e h i c l e T7 i n motion

v e l of t e r r a i n v e h i c l e T7 w i t h and without engine d r i v i n g and t h e depedence of t h e n o i s e l e v e l of t h e engine on t h e t r a v e l l i n g speed r e s p e c t i v e l y t h e number of r e v o l u t i o n s . The n o i s e of t h e v e h i c l e w i t h t h e engine d r i v i n g r e - f e r s t h e s t a t e b e f o r e t h e n o i s e r e d u c t i o n and t h e n o i s e of t h e engine t o t h e s t a t e a f t e r n o i s e r e d u c t i o n .

3

-

NOISE SOTJRCBS OF INTERNAL COMBTTSTION 'ENGINES

The n o i s e l e v e l of a l l i n t e r n a l combustion e n g i n e s i s determined by p e r f o r - mance and t h e speed of engine. Vverv combustion engine has i n n e r and e x t e r - n a l n o i s e s o u r c e s . The most important i n n e r n o i s e s o u r c e s a r e : t h e combustion, s t r o k e s of p i s t o n , t h e motor c o n t r o l , t h e d r i v i n g wheels e t c .

The e x t e r n a l n o i s e s o u r c e s a r e : t h e s u c t i o n system, t h e exhaust gas conduct, t h e c o o l i n g f a n , t h e motor s u r f a c e e t c

.

Although a number of n o i s e s o u r c e s a r e mentioned, t h e i r i n f l u e n c e on t h e n o i s e l e v e l of t h e v e h i c l e s w i l l d i f - f e r . One o r a n o t h e r n o i s e source can be more prominent.

4

-

^THECOOLING FAN

The c o o l i n g f a n i s i n s t a l l e d t o c o o l t h e engine and c a p s u l e . It may become an important n o i s e s o u r c e , e s p e c i a l l y i f l i t t l e a t t e n t i o n i n i t s d e s i g n has been paid t o t h e stream c o n d i t i o n s i n i t o r i n t h e i n l e t and o u t l e t . Such a s i t u a - t i o n can a r i s e , i f t h e l a y o t speed of t h e f a n proves inadequate and has t o be i n c r e a s e d by a new gear r a t i o . Tvery i n c r e a s e of t h e numbers of r e v o l u t i o n s s i m u l t a n e o u s l y means and i n c r e a s e of t h e c i r c u m f e r e n t i a l speed of t h e f a n b l a d e s . The stream c o n d i t i o n s i n t h e i n l e t and t h e o u t l e t and t h o s e i n t h e f a n change. By an a l t e r a t i o n of t h e s e c o n d i t i o n s t h e n o i s e of t h e f a n i n c r e a - s e s t o o .

The n o i s e o r t h e frequency spectrum can be i n f l u e n c e d , b e s i d e s by c o n s t r u c - t i o n a l t e r a t i o n s of t h e f a n and t h e b l a d e s , by a l t e r i n g t h e number of b l a d e s o r t h e i r arrangement.

5

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PERFORMANCE OF COOLING FAN

The ca s u l e and combustion engine a r e a t i o n i s u r g e n t l y because a p a r t of t h e p r e s u l g i n g h e a t energy i n t h e engine r e m a i n . i n t h e c a p s u l e . I n o r d e r t o c e r - t a i n normal working c o n d i t i o n s i n t h e combustion engine and c a p s u l e i t i s ne- c e s s a r y t o remove t h a t h e a t o u t s i d e t h e c a p s u l e . The q u a n t i t y of h e a t t o be removed from t h e c a p s u l e w i l l depend on t h e engine t y p e (water o r a i r coo- l e d ) , engine o u t p u t , annual s e a s o n , d u r a t i o n of working, t y p e of engine l o a - d i n g e t c . That h e a t i s removed by a i r and a t a low a i r temperature and w i t h t h e same q u a n t i t y of h e a t a s m a l l e r q u a n t i t y of a i r w i l l be n e c e s s a r y t h a n a t a h i g h e r t e m p e r a t u r e . That can be seen from t h e e q u a t i o n f o r h e a t d i s c h a r g e

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where

c

-

s p e c i f i c a i r h e a t

f

-

s p e c i f i c g r a v i t y ( k J B 5 K) (kg/m, )

m

-

mass of a i r (kg)

AT = T2

-

T,,

-

T,,

-

a i r t e m p e r a t u r e a t t h e

e n t r a n c e i n t o t h e c a p s u l e ( K ) T2

-

a i r t e m p e r a t u r e a t t h e e x i t

from t h e c a p s u l e (K)

I n c a s e of c o n s t a n t h e a t d i s c h a r g e w i t h T = 363 K , m = I k g , c = c o n s t . (between 273

-

513 K i s c = 1 , 0 0 5 k J / k g K$ and by d i f f e r e n t o u t s i d e tempera- t u r e s PI i t i s n e c e s s a r y a i r volume V , F i g u r e 2 a .

L 0 6 0 DO K

D I F F E R E N C E I N T E M P E R A T U R E AT

0

4 0 6 0 80 K

D I F F E R E N C E I N T E M P E R A T U R E T P i g . 2 a

-

A i r v o l u ~ e a s f u n c t i o n of F i g . 2b

-

Performance P and p r e s s u r e

d i f f e r e n c e i n t e m p e r a t u r e l o s s ~p of a c o o l i n g f a n The power of t h e c o o l i n g f a n depend on t h e a i r volume and t h e p r e s s u r e l o s s . T h i s c a n be s e e n i n t h e e q u a t i o n f o r c a l c u l a t i n g t h e performance P of a c o o l i n g f a n ( 3 ) and F i g u r e 2b:

where

V

-

a i r volume

~ p

-

p r e s s u r e l o s s

-

d e g r e e e f f e c t of f a n .

As t h e i n t e r n a l combustion e n g i n e must be good o r d e r t r o u g h h o u t t h e whole p e a r t h e e n g i n e a e r a t i o n system w i l l be d e s i g n e d f o r t h e most u n f a v o u r a b l e

o p e r a t i n g c o n d i t i o n s , i . e . , f o r t h e h i g h e s t o u t s i d e t e m p e r a t u r e . The a i r s u p p l y and d i s c h a r g e o p e n i n g s and c h a n n e l s w i l l be p r o p o r t i o n e d a c c o r d i n g l y . A s t h e c h a n n e l o p e n i n g s end on t h e o u t e r s i d e of c a p s u l e , t h e n o i s e w i l l pe- n e t r a t e outwards a l s o t h r o u g h them.

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C2-280 COLLOQUE DE PHYSIQUE

A n o i s e r e d u c t i o n on a v e h i c l e and a combustion engine can be achieved by a r e d u c t i o n of t h e i n f l u e n c e s of d i f f e r e n t n o i s e s o u r c e s without o r w i t h an encasement of t h e a g g r e g a t e s .

An encasement of a g g r e g a t e s i s not a t e c h n i c a l s o l u t i o n because it c a u s e s many o t h e r problems which must be solved w i t h h a r d l y a s m a l l e r expence. Bs- p e c i a l l ~ disadvantageous i s t h e f a c t t h a t only t h e i n f l u e n c e of some n o i s e s o u r c e s i s reduced and work on o t h e r n o i s e s o u r c e s must s t i l l be done.

An encasement can only reduce t h e i n f l u e n c e of t h e i n n e r n o i s e sources and s u r f a c e o f t h e engine. It does not a f f e c t t h e e x t e r n a l n o i s e s o u r c e s , t h e s u c t i o n and exhaust system, c o o l i n g of combustion engine and encasement, e t c . , remain a s t h e y were and must be worked on a d d i t i o n a l l y .

The e x t e r n a l n o i s e of t h e v e h i c l e , p a r t i c u l a r l y , i f i t s engine i s encased should be measured a t a n ambient temperature of 303-308 K and n o t perhaps a t a temperature of

-

²⁷³^K and w i t h t h e engine s l i g h t l y heated.

7

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INFLTJENCF OF FAN IN PASSBNGZR CAR

Usually, t h e d r i v i n g combustion engine of t h e passenger c a r s i s l o c a t e d a t t h e f r o n t s i d e . Temperature of t h e engine and of t h e space i n which t h e en- g i n e i s i n s t a l l e d i s h i g h e r , i f t h e engine i s encased, t h a n i f i t i s not encased. The s i t u a t i o n i s most c r i t i c a l , when t h e v e h i c l e moves i n a column a t a low speed and w i t h f r e q u e n t stoppages and i t i s s t i l l aggravated i f t h e ambient temperature i s h i g h . I n t h i s way, n o t only t h e f u e l consumption i s

i n c r e a s e d , b u t a l s o t h e q u a n t i t y of harmful s u b s t a n c e s i n t h e exhaust gases.

T h i s can be seen i n F i g u r e 3 showing f u e l consumption of p e t r o l engines f o r d i f f e r e n t engine work c y c l e s .

CONSTANT 90 k n l h

U-

F i g . 3

-

Consumption of f u e l by pas

senger c a r s

-

F i g

30

6

2 0 1 11 111 1v

FAN S P E E D

.

⁴

-

Noise of c o o l i n g f a n s i n Das- senger c a r s A ,B,

c

^,D,

FREOUENZ f FREQUENZ f

F i g . 5

-

Noise of c o o l i n g f a n s i n F i g . 6

-

Noise of c o o l i n g f a n and

t h r e e passenger c a r s combustion engine i n a c a r

A l l t h e passenger c a r s a r e equipped w i t h multiple-speed f a n s , whose n o i s e l e v e l i n most c a s e s i s v e r y h i g h s o t h a t it i s n e c e s s a r y t o d i s c o n n e c t i t . The f a n n o i s e l e v e l exceeds t h e n o i s e l e v e l of t h e d r i v i n g engine and o t h e r v e h i c l e n o i s e s o u r c e s . F i g u r e 4 g i v e s n o i s e l e v e l of t h e c o o l i n g f a n w i t h t h r e e and f o u r speeds i n t h e i n s i d e of f o u r passenger c a r s .

F i g u r e s

5

and 6 give t h e frequency a n a l y s i s of t h r e e f a n s f o r cooling t h e i n t e r i o r of t h r e e passenger c a r s . For comparison, t h e n o i s e l e v e l of t h e combustion engine a t i d l i n g i s g i v e n , F i g u r e 6.