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2.Theprocessofenergytransformationinhydraulicgearmachines
DrivingpowerN
g,whichshouldbesuppliedfromthemotor,canbedefinedknow-
ingrealtorqueM
g,whichoughttobeappliedontheshaftofthepump,aswellas
theangularvelocityω
goftheshaft:
N
g±M
glω
g
(2.10)
EffectivepowerN
e,whichcanbeutilizedinahydraulicsystem,isdetermined
basedontheknowledgeofrealdeliveryQ
g,andloadp
gofthepump,namely:
N
e±Q
glp
g
(2.11)
BycomparingeffectivepowerN
etodrivingpowerN
g,thetotalefficiencyn
gof
thepumpcanbedefinedas:
K1
g
N
N
g
e
(2.12)
Byimplementingdependencies(2.10),(2.11)andthen(2.7),(2.9)and(2.5)in
theformula,thefollowingequationisobtained:
n
g±n
vgln
hmg
(2.13)
Itmeansthatthetotalefficiencyofthepumpisaproductofthevolumetriceffi-
ciencyn
vgandthehydraulic-mechanicalefficiencyn
hmg.
Thecurvesn
hmgofallthethree,namelyofefficiencyn
vg,n
hmg,n
grelatingto
loadp
gofthepump,arepresentedinFigure2.5c.
2.2.2.Characteristicsofamotor
AsFigure2.2presents,inthemotorhydraulicenergyE
hydraccumulatedinthework-
ingfluidistransformedintomechanicalenergyE
mechtransferredontotheshaftof
theworkingunit.Itisareversetransformationthantheoneobservedinthepump.
Inanidealmotor,thereisnoenergyloss,andbasedontheenergyconservationlaw
thefollowingequationiscreated:
M
stlω
s±Q
stlp
s
(2.14)
where:
M
st-theoreticaltorqueontheshaftofthemotor(torqueofthemotor),
ω
s-angularvelocityoftheshaftofthemotor,
Q
st-flowrateoftheworkingfluidthroughthemotor,namelythetheoretical
capacityofthemotor,
p
s±p
I-p
o-pressuredifferenceontheinletandtheoutlet(supplyand
dischargepressuredifference).
TheoreticalcapacityQ
stofthemotorregardlessofthevolumetriclossisdeter-
minedbythedependency:
Q
st±q
sn
s
(2.15)