PROC
CEEDINGS of the23rd Internationa
al Congresss on Acousttics
1 Septembber 2019 in Aachen,AGerrmany
9 to 13

Noise andavibra
ation of self-adju
sst valve
namic focau
used by hydrody
horce
Liaang Xiangdoong; Chen Booreng; Zhu Bing
B
China ship Develoopment and Deesign Center, China

ABSTRA
ACT
Liquid viibration is thee source of duuct noise and is main reaso
on of pipe connnector to be loosen and leeaking out
working medium fromm the connector also. Besiides machinee linked to thee pipe line, vvalve in the piipe line isuid passing thhrough the vaalve can cause valve toalso one kind of vibraation source too the pipe line because liqua radiate nooise. Thermoostat control valvev
is a kinnd of self-adj
djust valve ussed in oil pip
pe line forvibrate andprotectinng machines. To control thhe oil temperaature in selectted range the thermostat coontrol valve canc adjust
the oil floows to the heeating branch pipe and coooling branch pipe
p as the oill temperaturee is changed. But whenit adjustss flow of oil, vibration andd noise will beb taken placce in the valvee. And this kkind of liquid vibration
may dammage the therm
mal rod of thee thermostat control
cvalve. The mechanism of how thhis kind of vaalve liquidvibrationn taken place will be shownn in this papeer. Some of su
uggestion aboout decreasingg or avoiding
g this kindof vibratiion on the oill pipe line will be given inn this paper baased on the coonclusion of investigationn.
Keywordds: Valve, Vibbration, Noisee, Pipe line, TemperatureT

1. INTTRODUCTION
Oil can deduce thhe friction beetween moviing parts of thet machine. It can cleann the parts off machine
nly should beb easy to fllow for cleaaning andand coo l down the temperature of machinee. Oil not on
cooling down but al so has abilitty to adhere to the surfacce of machinne parts as ooil film to prrotect thef
It is not allowedd that the tem
mperature of oilo gets too llow or too high. If themachinee parts from friction.
oil temperature weree to be too loow, oil mighht be difficultt to flow beccause of the high viscosiity of oil.
osity of oil is. If the oil teemperature werew
to be
Because the lower thhe temperatuure is the highher the visco
mbe easyy to be destrooyed and thee machine paarts might
too high , oil film on machine parrt surfaces might
be damaaged by fricttion. So therre are auxiliary cooling equipment anda heating equipment ini the oilsystem. The thermosstat control valvevin the oilo system caan play an immportant rolee to decide cooling ort oil autom
matically acccording to thhe practical oilo temperatuure.
heating theThe key
k part of thhermostat coontrol valve is a slide vallve 1 linked with the theermal rod 3, asa shownin figuree 1. To controol the oil tem
mperature of channel A, thet slide valvve could be m
moved up or down by
thermal rod and pre--pressed spring 2. Expannding with heat
hand conttracting withh cold of theermal rod
and pushh-back of the spring cann decide the place of the slide valve to adjust th e opening deegrees ofheating channelc
B annd cooling chhannel C for heating oil whenw
oil is cold or coolinng oil when oil
o is hot.
But at thhe beginningg of change statesfrom heeating to cooling, valve anda pipe nearr the valve may
m oftenbe exciteed to vibratee. We shall discussdthe mechanismmoff this kind off vibration inn this paper.

a) At fulll heating positionb) Att full coolingg position

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Figure 1 - Sketch of thermostat control valve
Many investigators have studied the objector of vibration and noise from valve and pipeline. SunDanfeng et al. (1) have investigated the pipe line resonance property with flow. The result shows thatnatural frequency of the pipe line would increase slightly because of the action of fluid-structureinteraction. Liu Li et al. (2) have developed mechanism of pipe line vibration caused by flow andfound that the main excitation is the plus from fluid behind the valve. Fang Chao et al. (3) have studied
the sea valve noise caused by flow and compared the quantity of flow noise to that of vibration noise
induced by flow. They described the reason of sea valve noise based on the principle of soundgeneration. Chen Guiqing et al. (4) have investigated the relationship between parameters of flow inthe pipe and vibration of the pipe. He obtained the conclusion that pipe vibration is linked with thevelocity of flow in the pipe directly. Yin Jianwu et al. (5) have finished some experiments about
control air pipe vibration and developed some methods about deducing air column impulse, optimal
designing pipe line and deducing vibration by balance. In order to investigate the phenomena of valve
dynamic property, Lu Liang et al. (6) have shown some examples and methods about watching,measurement and simulation. All of above studies describe a fact that the main excitation of valve
vibration is flow which passing through it because of the relaxation property of fluid. But there isdifferent valve vibration characteristic excited by flow to different valves. If you want to control thevalve vibration noise you must take a special analysis to the particular valve. The best way to control
vibration noise is deal with the vibration noise source based on the mechanism of vibration noisegeneration. In this paper, we shall analysis the mechanism of thermostat control valve noise in the oilsystem and give some suggestions based on the analysis.

2. How the thermostat control valve controls the oil temperature and when thenoise is obvious detected
The key part of thermostat control valve is a slid valve component, as shown in figure 1. The
component consisted of slide valve 1 and thermal rod 3 is touched with compressed spring 2 and thehand adjusting shank 4. When the oil temperature is lower and need to be heated, the thermal rod gets
shorter because of low temperature. Then the slide valve moves to open the heating channel until fullopen and to close the cooling channel until close off with the spring stretching, as shown in figure 1 a).
When the oil temperature is higher and need to be cooled. The thermal rod gets longer because of hightemperature and the spring is compressed. Then the slide valve moves to open the cooling channel until
full open and to close the heating channel until close off, as shown in figure 1 b). If the thermal rod
fails in function, the hand adjusting shank can be turned to adjust the position of the slide valve tocontrol the oil temperature.
When oil system which serves for machine starts to work, the oil temperature is lower in general, so
the heating channel of the thermostat valve is always full opened and cooling channel is closed. Aftermachine and oil system running for a while, as the oil temperature gets higher, the heating channel will
be closed little by little and cooling channel will be opened little by little. At that time when channels
start to change, an obvious vibration noise would appear at the thermostat control valve and the pipenear the thermostat control valve. But as the time goes by, the vibration noise would disappear. Thiskind of vibration noise is harmful to the safety and reliability of operation of oil system. The reason ofthis vibration noise generation must be investigated and the phenomenon should be avoided as far aspossible.

3. Investigation
3.1 Forces on the slide valve
When thermostat control valve adjusts the oil temperature by moving slide valve there are three
forces on the slide valve: Spring force FS of spring, thermal force FT of thermal rod caused byexpanding with heat and contracting with cold and hydrodynamic force FH of oil flow. Thethermostat control valve can be used in oil system in two ways, shown in figure 2. One is confluence
type, as shown in figure 2 a). This type is fit to control the input oil temperature of machine. The otheris shunt type, as shown in figure 2 b). This type is fit to control the output oil temperature of machine.

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a) Confluence typeb) Shunt typeFigure 2 - How to apply thermostat control valve
Linked with sketch of thermostat control valve, figure 1, the spring force FS always tends to closethe cooling channel. But the direction of thermal force FT is always opposite to that of spring force.
Either in confluence type or shunt type, spring force and thermal force can’t make thermostat control
valve vibrate because these forces are all semi-static force, their quantities can only change very
slowly. The excitation must be fluctuating hydrodynamic force FH .
3.2 Mechanism of self-excited vibration of thermostat valve
According to the Bernoulli equation, formula (1) (regardless of the difference of highness),pressure P will be changed by the variation of velocity v of flow. When opening area of channel isincreased, the resistance of flow would be decreased, the velocity of flow would be increased and thepressure of fluid would be decreased; but when opening area of channel is decreased, the resistance offlow would be increased, the velocity of flow would be decreased and the pressure of fluid would beincreased.

P0P

1 2Uv2

㸦1㸧

After machine start to work for a while, the temperature of oil will be increased, the thermal rodwill be extended and the spring will be compressed more. So the slide valve would be moved to open
cooling channel and to close heating channel for decreasing the oil temperature. When opening area ofcooling channel is increased then opening area of heating channel is decreased, the velocity of coolingchannel would be increased and the pressure would be decreased but the velocity of heating channel
would be decreased and pressure would be increased. The sum of hydrodynamic force generated bychanging opening areas of channels would tend to decrease cooling channel opening area and increase
heating channel opening area. If cooling channel opening area was decreased and heating channel
opening area was increased, there would be a hydrodynamic force on the valve to change both twochannel opening areas in opposite direction. It will cause the valve to vibrate that the hydrodynamicforce opposite the direction of movement of slide valve is forced to the valve continuously. In the sameway, if the oil temperature was decreased, the slide valve would be forced to vibrate by thehydrodynamic force which is tended to the opposite direction of movement of slide valve. When theslide valve is forced to vibrate, the oil pressure will be fluctuated. The pipe line noise would begenerated by the slide valve vibration and oil pressure fluctuation. The thermal rod linked with theslide valve would be damaged because of fatigue and lose effectiveness early by this kind of vibration.
Based on the characteristic curve of thermostat valve (7), as shown in figure 3, for the same
quantity change of flow, the larger the original flow is, the higher the change of oil pressure is. Sowhen slide valve is at one of positions as figure 1, i.e. heating channel opening area starts to bedecreased from full open or cooling channel opening area starts to be decreased from full open, thehydrodynamic force on the slide valve will get the largest quantity. After machine starts to work for awhile, the oil would be cooled from heating process as the oil temperature gets higher. So the heating
channel open area would be decreased from full open state and the vibration would be taken placeintensely. After the oil system continuous works for a while, the phenomena of vibration would get
weekly as the oil temperature gets lower and the quantity of flow gets lower with the heating channel

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area gets smaller. Because oil system can’t be allowed to work in setting highest temperature, coolingchannel open area can’t get full open position, as shown in figure 1 b). So intensely vibration will nottake place when oil system turn to heat from full cooling state. It just takes place when oil system turnto cool from full heating state.

Figure 3 - Flow and pressure difference characteristic curve of thermostat valve
Based on the above outline we can know that the self vibration will be taken place on the slide valvecaused by variable hydrodynamic force when the slide valve is moved to change the channel open area.
Heavy noise and vibration will be excited on the oil system pipe line and thermostat valve by thevibration of slide valve.

4. Conclusion and improvement
Due to the property that change of velocity is opposite to the change of pressure in the fluid. Self
excited vibration may easily be taken place on the valve when its channel opening area is changed.
Because of the randomness of this kind self excited vibration, it is difficult to predict at the design
stage. In this paper, based on the hydrodynamics basic principle, we have outlined the mechanism ofknown self excited vibration of thermostat valve which key part is a slide valve. According to the flow
and pressure variation characteristic of this thermostat valve, the result of analyze is fit as same as thepractical phenomenon.
It is not very difficult to solve this self excited vibration problem based on the flow and pressure
variation characteristic of the thermostat valve. Because this vibration noise phenomenon is often
taken place at the moment of channel opening area starting to be decreased from full open. If thisprocedure can be passed quickly by hand the obvious vibration noise would be avoided. It is thesuggestion that turn the hand adjusting shank of thermostat valve when the heating channel opening
area starts to be decreased. Let the procedure of closing heating channel and opening cooling channel
pass the time of intense vibration noise quickly.

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flow rate, Cryo Engineering, 2016;4: 50-55.
3. Fang Chao, Ma Shihu, Cai Biaohua, Yu Jian. Numerical Simulation Contrastive study on flow noise andflow induced vibration noise of sea valve based on BEM, Ship Science and Technology, 2018;3: 30-34.
4. Chen Guiqing, Hao Tingyue, Qi Zhendang, Influence of Physical Parameters on Vibrating NaturalFrequency of Pressure Pipeline, Journal of Tangshan College,2005; 4: 96-99.
5. Yi Jianwu, Yang Weiqun, Yuan Qinglu, E Weibo, Vibration Cause and Anti-vibration Method of Gas

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Piping of a Compressor, Compressor Technology, 2002; 4: 38-39.
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Visualization Methods in Hydraulic Valves, Chinese Hydraulics & Pneumatics, 2018;4: 1-7.
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