Lub Hwj Chim Ntawm Lub Hwj Chim Ua Li Cas (Pulse-Width Modulation Ntawm 1 Hz Vs. 100 Hz) Rau Titanium Sheath Heater Hloov Thermomechanical Fatigue Life Of Resistance Wire Thiab Tube?
Tso lus
Hauv hluav taws xob titanium sheath heaters, lub zog feem ntau yog hloov kho siv mem tes -width modulation (PWM) los tswj qhov kub thiab txias. Qhov zaus ntawm PWM teeb liab txiav txim siab sai npaum li cas lub rhaub cua sov mus rau thiab tawm. Ntawm qhov tsawg zaus (1 Hz), txhua lub voj voog ua rau qhov kub thiab txias ntawm 10-30℃hauv cov hlau tsis kam thiab cov titanium sheath. Thaum lub siab zaus (100 Hz), lub thermal loj ntawm lub rhaub dej smooths tawm cov pulses, uas ua rau kub viav vias tsuas yog 1-5 degree. Cov kev hloov pauv kub no ua rau muaj kev ntxhov siab nyob rau hauv ob qho tib si hauv cov hlau tsis muaj zog (feem ntau yog npib tsib xee{11}}chromium alloy) thiab titanium sheath. Thermomechanical qaug zog lub neej nce los ntawm qhov tseem ceeb ntawm 5-10 thaum ua haujlwm ntawm 100 Hz piv rau 1 Hz vim qhov txo qis kev ntxhov siab rau ib lub voj voog.
Lub Mechanism ntawm Thermomechanical Fatigue los ntawm Fais Fab Modulation
Txhua lub zog- ntawm lub voj voog ua kom sov cov hlau tiv thaiv, uas nthuav dav. Qhov kev nthuav dav ntxiv dag zog rau ib puag ncig magnesium oxide rwb thaiv tsev thiab titanium sheath. Txhua lub zog- tawm lub voj voog tso cai kom txias thiab sib zog. Qhov kev ntxhov siab amplitude (Δσ) yog proportional rau qhov kub thiab txias viav vias (ΔT) zaus coefficient ntawm thermal expansion. Rau NiCr hlau,=14 × 10⁻⁶ /℃; rau titanium,=8.6 × 10⁻⁶ /℃. Ntawm 1 Hz modulation nrog 30℃kub viav vias, NiCr xaim muaj kev cuam tshuam txog kev sib tw ntawm kwv yees li 0.04%, txaus los ua kom qis - voj voog qaug zog ntau tshaj lab lub voj voog. Ntawm 100 Hz modulation nrog 5℃viav vias, qhov strain tsuas yog 0.007%, uas yog qis dua qhov qaug zog txwv rau ob qho khoom siv, ua rau ze rau - lub neej tsis kawg.
Quantitative Fatigue Life as a Function of PWM Frequency
Kev tswj xyuas ntawm Qib 2 titanium sheath heaters nrog NiCr tsis kam xaim ntawm 15 W / cm² lub zog ntom ntom tau tsim cov kev qaug zog hauv qab no rau ntau zaus PWM. Thaum lub sijhawm ua haujlwm tas mus li (tsis muaj kev hloov kho, lub hauv paus), qhov kev tiv thaiv hlau lub neej ntev tshaj 100,000 teev, thiab titanium sheath qhia tsis muaj thermal qaug zog. Ntawm 0.1 Hz PWM (ib lub voj voog txhua 10 vib nas this) nrog 40℃kub viav vias, lub neej tiv thaiv hlau yog 2,000-5,000 teev, thiab titanium sheath qhia cov kab nrib pleb tom qab 10,000-20,000 cycles. Ntawm 1 Hz PWM nrog lub viav vias 30 degree, qhov kev tiv thaiv hlau lub neej yog 5,000-15,000 teev, thiab titanium sheath qhia cov kab nrib pleb tom qab 20,000-50,000 cycles. Ntawm 10 Hz PWM nrog lub viav vias 15 degree, qhov kev tiv thaiv hlau lub neej yog 20,000-50,000 teev, thiab titanium sheath qhia tsis muaj kab nrib pleb hauv 100,000 cycles. Ntawm 100 Hz PWM nrog lub 5℃viav vias, lub zog tiv thaiv hlau lub neej tshaj 100,000 xuab moos, thiab titanium sheath qhia tsis muaj thermal qaug zog. Ntawm 1,000 Hz PWM, qhov kub ntawm lub viav vias yog qis dua 2 degree, thiab kev ua tau zoo sib npaug rau kev ua haujlwm tas mus li.
Influence of Power Density and Heater Geometry on PWM Sensitivity
Cov nyhuv ntawm PWM zaus yog nyob ntawm lub zog ceev thiab thermal loj ntawm lub rhaub. Ntawm qhov tsawg zog ceev (5 W / cm²), qhov kub ntawm lub viav vias yog me me rau txhua zaus, yog li 1 Hz PWM teeb liab tsuas yog 10℃viav vias, thiab lub neej hlau yog 20,000-50,000 teev. Ntawm lub zog siab ceev (25 W / cm²), 1 Hz PWM teeb liab ua rau 50℃viav vias, txo cov xaim lub neej mus rau 1,000-3,000 teev. Rau nyias- phab ntsa raj (0.9 mm), lub thermal huab hwm coj qis dua, thiab qhov kub ntawm lub viav vias loj dua. Rau cov tuab- phab ntsa raj (2.0 hli), qhov cua sov yog siab dua, thiab qhov kub hloov pauv tau txo los ntawm 30-50%. Rau lub cua sov ntev (2 m), lub thermal loj kuj dampens kub viav vias ntawm qhov kawg.
PWM Zaus Xaiv Phau Ntawv Qhia rau Titanium Sheath Heaters
The following table provides recommendations for PWM frequency based on power density, desired heater life, and temperature control requirements.
| Lub zog ceev (W / cm²) | Desired Heater Life (teev) | Yuav tsum tau Temperature Control Precision (± degree) | Pom zoo PWM zaus (Hz) | Cia siab tias kub viav vias (degree) |
|---|---|---|---|---|
| <10 | >50,000 | 2 | 1 | 10–15 |
| <10 | >50,000 | 0.5 | 100 | 2–5 |
| 10–20 | >50,000 | 2 | 10 | 8–12 |
| 10–20 | >50,000 | 0.5 | 1,000 | 1–3 |
| 20–30 | >20,000 | 2 | 100 | 3–6 |
| 20–30 | >50,000 | 1 | 1,000 | 1–2 |
| >30 | >10,000 | Ib qho | 1,000+ | <2 |
Engineering Beyond PWM Frequency Selection
Qib titanium tsis cuam tshuam rau thermal qaug zog ntawm cov hlau tsis kam, tab sis Qib 7 titanium muaj cov thermal expansion zoo sib xws rau Qib 2. Cov khoom siv hlau kuj cuam tshuam rau lub neej qaug zog; NiCr 80/20 xaim muaj thermal qaug zog zoo dua li FeCrAl hlau. magnesium oxide rwb thaiv tsev zoo teeb meem; zoo-Compacted MgO hloov cov cua sov zoo dua, txo qhov kub ntawm qhov sib txawv ntawm cov hlau thiab cov ntaub. Mos- pib tswj fais fab (sib npaug zog nce ntau dua li tag nrho ntawm -tawm pulses) tuaj yeem txo qhov kev ntxhov siab ntxiv. Rau cov ntawv thov uas xav tau kev tswj qhov kub thiab txias, qhov siab dua PWM zaus (100-1,000 Hz) yog ib txwm nyiam.
Ua ib qho kev qhia tshwj xeeb
Rau lub tshuab hluav taws xob titanium sheath nrog lub zog hloov kho, qhia txog PWM zaus ntawm 100 Hz lossis siab dua kom txo qis cov thermomechanical qaug zog. Rau siab - fais fab - daim ntawv thov ceev tshaj 20 W / cm², qhia 1,000 Hz PWM los yog siv ib theem - lub kaum sab xis tswj (sib npaug zog tswj) es tsis txhob ntawm - tawm kev hloov kho. Rau cov cua sov uas twb muaj lawm ua haujlwm ntawm qhov tsawg zaus (1 Hz), ntxiv cov inductor smoothing lossis hloov tus maub los rau siab - zaus PWM. Yog tias qhov ntsuas kub tswj qhov tseeb ntawm ± 2℃tau txais, qhov zaus ntawm 10 Hz muab lub neej thermal qaug zog txaus rau feem ntau daim ntawv thov. Los ntawm kev khiav hauj lwm ntawm 100 Hz PWM es tsis txhob 1 Hz, tus engineer txo qhov kub ntawm lub viav vias ntawm 30℃mus rau 5 degree, ncua lub neej qaug zog ntawm cov hlau tsis kam thiab cov titanium sheath los ntawm qhov zoo ntawm 5-10.
