Secondary Air Injection System Manifold Crack Detection Methods

Overview of Technical Issues:

The secondary air injection manifold experiences thermal cycling between ambient and 400-800°C from exhaust gases, causing stress-induced crack formation at weld joints and thin-wall sections; these cracks create harmful air leakage that reduces injection efficiency and emissions control performance. Current detection methods provide insufficient early-stage crack identification capability—visual inspection only reveals cracks after significant propagation has occurred, missing the optimal intervention window. The goal is to develop detection methods capable of identifying micro-cracks before they cause measurable air loss and system performance degradation.

Solution directions generated for this problem

Problem Direction 1 :

ImproveCrack detection resolution
VS
ConstraintMeasurement system complexity

Inspiration 1 : Cross-domain reference

Application Principle: #26 Copying
Cross-domain applicability Assess applicability
Method of condition monitoring one or more wind turbines and parts thereof and performing instant alarm when needed
Innovative Solution Refine solution

Infrared thermal signature mapping for micro-crack detection

Thermal imaging replaces contact scanning
How to solve :
  • Apply controlled thermal excitation (heat gun at 150-200°C, 30s pulse) to weld joints and thin-wall sections during inspection cycles
  • micro-cracks create localized thermal discontinuities visible in infrared spectrum
  • Capture full-field thermal images using handheld infrared camera (resolution ≥320×240 pixels, thermal sensitivity ≤50mK) during cooling phase (5-15s post-heating)
  • cracks <0.1mm appear as 2-5°C temperature differentials against baseline
  • Process thermal maps with edge detection algorithms (Sobel or Canny filters, threshold ±1.5°C) to automatically identify anomaly patterns indicating crack initiation
  • compare against baseline thermal fingerprints from defect-free reference manifolds
Expected Effect : Detect <0.1mm cracks; equipment cost <$5000; inspection time 5-10 min per manifold
Risk Control :
  • ambient temperature variation affecting thermal contrast
  • surface oxidation or coating interference
  • operator training for thermal pattern interpretation

Problem Direction 2 :

ImproveCrack detection resolution
VS
ConstraintInspection operation duration

Inspiration 1 : Cross-domain reference

Application Principle: #10 Preliminary action
Cross-domain applicability Assess applicability
Apparatus and method for transmitting content in portable terminal
Innovative Solution Refine solution

Baseline thermal signature mapping for targeted micro-crack inspection

Map stress and thermal signatures during manufacturing for rapid focused inspection
How to solve :
  • During initial manifold fabrication, conduct full-field thermography under simulated thermal cycling (400-800°C) and record baseline thermal distribution maps with 0.05°C resolution
  • identify and digitally mark high-stress zones (weld joints, thin-wall sections) showing temperature gradients >5°C/cm as priority inspection areas
  • In subsequent quality control and maintenance, apply targeted inspection protocol — scan only pre-identified high-risk zones (typically 15-25% of total surface area) using handheld infrared camera at 30 Hz frame rate, detecting micro-cracks as 0.3-0.8°C thermal anomalies within 3-5 minutes
  • Establish deviation threshold criteria — flag any zone showing >1.2°C temperature change from baseline map under identical thermal load
  • validate flagged areas with fluorescent penetrant testing (acceptance: no crack indication under 365nm UV light at 1000 μW/cm²)
Expected Effect : Inspection time reduced to 3-5 min vs 60+ min full-surface scan; <0.1mm crack detection maintained; 80% reduction in scan area
Risk Control :
  • baseline map accuracy degradation over service life
  • thermal camera calibration drift beyond ±0.5°C
  • high-risk zone prediction false negatives

Problem Direction 3 :

ImproveDetection timing capability
VS
ConstraintInspection operation duration

Inspiration 1 : Cross-domain reference

Application Principle: #10 Preliminary action
Cross-domain applicability Assess applicability
Apparatus, system and method of communicating non-cellular access network information over a cellular network
Innovative Solution Refine solution

Baseline thermal signature mapping for targeted micro-crack inspection

Map thermal stress zones during manufacturing to enable rapid focused inspection
How to solve :
  • Perform infrared thermography mapping during initial manifold thermal cycling (3 cycles, 25-800°C) to establish baseline thermal signature and identify high-stress zones at weld joints
  • archive thermal distribution data with temperature gradient thresholds (>15°C/cm indicates crack-susceptible zones) and assign priority inspection coordinates
  • during service inspections, scan only pre-identified high-risk zones (typically 8-12 locations covering <20% of total surface area) using portable IR camera (resolution ≥0.1°C, frame rate 30Hz) under 60-second thermal pulse, detecting micro-cracks as 2-5°C localized anomalies
Expected Effect : Inspection time reduced from 120min full-scan to 15min targeted scan; micro-crack detection <0.1mm at formation stage; false positive rate <5%
Risk Control :
  • baseline mapping accuracy degradation over service life
  • thermal signature drift due to surface oxidation
  • operator training for anomaly interpretation
Patsnap Eureka Solution