Environmental Engineering Reference
In-Depth Information
every. 10. m,. the. elevation. creates. atmospheric. pressure. of. 1,. so. if. the. high.
elevation.reaches.1,000.ft.,.then.the.acting.atmospheric.pressure.is.100..A.new.
measurement. technique. for. the. regime. of. transonic. compressors. with. PSP.
was.applied.in.a.transonic.compressor.stage. 31
6.4.2 
Measurement Concept
Thermal,.or.infrared.energy,.is.light.that.is.not.visible.because.its.wavelength.
is.too.long.(800-1,200.nm).to.be.detected.by.the.human.eye;.it's.the.part.of.the.
electromagnetic.spectrum.that.we.perceive.as.heat..Infrared.thermography.
cameras. produce. images. of. invisible. infrared. or. “heat”. radiation. and. pro-
vide.precise.noncontact.temperature.measurement.capabilities.
The.coating.is.illuminated.with.the.light.of.the.appropriate.energy.(color,.
frequency.-f ex ).to.excite.the.coating-entrapped.probe.molecules..The.result-
ing.luminescence.output.(frequency.-f em ).is.inversely.proportional.to.the.sur-
face.pressure.or.temperature.of.the.test.model.
The.PSP/TSP.measurement.technique.is.based.on.the.deactivation.of.pho-
tochemically.exited.molecules,.luminophores,.and.by.the.presence.of.oxygen.
molecules.. When. luminophores. absorb. light. with. the. correct. wavelength,.
they.are.promoted.from.their.base.energy.state.to.a.higher.state..These.mol-
ecules.can.lose.the.extra.energy.either.through.emission.of.light.(lumines-
cence). or. even. without. radiation.. The. interaction. of. excited. luminophores.
with. oxygen. molecules,. i.e.,. quenching. increases. the. probability. of. lumi-
nosity,.which.is.recognizable.on.the.surface.of.the.blade..Such.a.luorescent.
image. arising. under. the. low. conditions. can. be. recorded. using. a. detector.
with.the.same.properties.as.a.covering.paint.or.CCD.camera.with.an.opti-
cal.ilter..For.the.purpose.of.increasing.adhesive.properties,.we.added.to.the.
composition.silicon.carbide.paint..We.also.must.be.conident.that.this.com-
position.will.be.stable.under.vibration.and.shocks.
6.4.3 
Application of the PSP/TSP Technique
In.an.operational.test,.the.wind.turbine.blade.model.was.coated.with.oxy-
gen-sensitive.probe.molecules/polymeric.formulation.and.illuminated.with.
the.light.of.appropriate.energy.(color)..The.resulting.luminescence.from.the.
model. is. imaged. using. a. charge-couple. device. (CCD). camera.. Pressure. is.
correlated.with.the.ratio.of.PSP.images.acquired.at.a.reference.condition.of.
known. pressure. and. temperature. and. at. a. condition. through. a. modiied.
form.of.the.Stern-Volmer.relationship.
Iref
Ip = A + B
P
Pref .
.
(6.35)
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