Secondary Air Injection System Design for Cold Start

Overview of Technical Issues:

The secondary air injection system faces insufficient air delivery capacity during the critical cold start period (first 20-60 seconds), preventing the catalytic converter from reaching light-off temperature quickly enough, resulting in excessive hydrocarbon and carbon monoxide emissions when 60-80% of total trip emissions occur; the goal is to achieve rapid converter heating to operating temperature (300-400°C) within 30 seconds of engine start.

Solution directions generated for this problem

Problem Direction 1 :

ImproveSecondary air mass flow rate
VS
ConstraintSystem power consumption

Inspiration 1 : Cross-domain reference

Application Principle: #19 Periodic action
Cross-domain applicability Assess applicability
Flow path sensing for flow therapy apparatus
Innovative Solution Refine solution

Breath-synchronized pulsed air injection for cold-start emission control

Synchronize air pump with engine cycle
How to solve :
  • Operate air pump in synchronized pulses matching engine exhaust strokes (2s on at 85% duty, 0.8s off) to deliver required oxygen mass while reducing average power draw by 35-40%
  • Install pressure accumulator tank (0.8L, 2.5 bar pre-charge) upstream of injection valve to buffer pulsed flow into steady catalyst delivery, maintaining oxidation reaction continuity
  • Implement ECU-controlled variable frequency drive (switching frequency 0.5 Hz, phase-locked to crankshaft position sensor) to modulate pump motor current between 12A peak and 2A idle, smoothing electrical load on cold-start battery system
Expected Effect : 30s light-off achieved; power draw reduced 38%; emissions cut 55%
Risk Control :
  • accumulator pressure decay over temperature cycles
  • pulse timing drift from sensor lag
  • motor thermal stress from rapid cycling

Problem Direction 2 :

ImproveAir pump delivery capacity
VS
ConstraintSystem packaging volume

Inspiration 1 : Cross-domain reference

Application Principle: #1 Segmentation
Cross-domain applicability Assess applicability
Engine aftertreatment system and vehicle
Innovative Solution Refine solution

Dual-stage micro-pump array with sequential activation for cold-start air injection

Replace single pump with distributed micro-pump array
How to solve :
  • Deploy four micro-vane pumps (each 18-22 cm³ displacement) in unused interstices around intake manifold and valve cover perimeter, total capacity 72-88 cm³ vs single 65 cm³ pump — 11-35% capacity gain with zero net volume increase
  • Activate pumps in sequential pairs: pumps 1+2 operate seconds 0-15, pumps 3+4 operate seconds 15-30, maintaining continuous 144-176 L/min flow while distributing thermal and electrical load across four units (each drawing 180-220W vs 650W single pump)
  • Install Y-junction manifold segments (ID 12mm, wall thickness 1.2mm) at each pump pair outlet, converging to main 20mm feed line with integrated check valves (cracking pressure 15 mbar) to prevent backflow — total piping adds <180 cm³ within existing air gap volumes
  • Each micro-pump uses brushless DC motor (12V, 15A peak) with sintered bronze bearings (tolerance ±0.02mm), carbon fiber reinforced nylon housing (operating range -40 to 120°C), and hall-effect speed sensor for closed-loop control at 8000±200 RPM during active phase
Expected Effect : Capacity +25%, volume neutral, power per unit -65%
Risk Control :
  • pump synchronization timing drift
  • check valve leakage under vibration
  • micro-pump bearing wear acceleration

Problem Direction 3 :

ImproveConverter heating rate
VS
ConstraintSystem power consumption

Inspiration 1 : Cross-domain reference

Application Principle: #21 Skipping
Cross-domain applicability Assess applicability
Devices and methods for manipulating user interfaces using a stylus.
Innovative Solution Refine solution

Ultra-short pulse air injection with maximum intensity front-loading for rapid catalyst light-off

Concentrate air delivery into ultra-short maximum-intensity bursts during critical thermal window
How to solve :
  • Operate air pump at peak overload capacity (150-180% rated power, 800-1200W) for only the first 12-15 seconds, delivering 75-85% of total required oxygen mass when catalyst is coldest and oxidation heat release is most effective
  • then reduce to minimal sustaining flow (100-150W) for remaining 15-18 seconds, exploiting catalyst thermal inertia to carry temperature rise through to light-off
  • Install thermal management controller monitoring real-time catalyst temperature via embedded thermocouple (±5°C accuracy, 50ms response), dynamically terminating high-power phase once 280°C threshold reached
  • Use brushless DC pump motor with active liquid cooling jacket (ethylene glycol circuit, 60-80°C operating range) enabling brief thermal overload without damage, paired with supercapacitor buffer (10-15F, 14V rated) pre-charged during previous shutdown to supply peak current without battery voltage sag below 11.5V
Expected Effect : Total energy consumption -35 to -42% vs continuous operation; light-off time 28-32s; peak power duration reduced from 30s to 12-15s; catalyst reaches 320-380°C with same emissions performance
Risk Control :
  • pump motor thermal runaway during extended overload
  • supercapacitor charge retention loss over multi-day park periods
  • catalyst thermal shock from rapid temperature ramp

Problem Direction 4 :

ImproveSystem power consumption
VS
ConstraintMust not deteriorate

Inspiration 1 : Cross-domain reference

Application Principle: #10 Preliminary action
Cross-domain applicability Assess applicability
Providing assistance to a base station from user equipment
Innovative Solution Refine solution

Pre-shutdown capacitor bank energy storage for cold-start air injection

Store energy before engine shutdown to power air pump during next cold start
How to solve :
  • Install ultracapacitor bank (150-200F, 48V) charged to full capacity during final 8-10 seconds of previous engine shutdown using available alternator power (300-400W charging rate)
  • Deploy dedicated DC-DC converter and relay circuit that isolates capacitor from vehicle electrical system during cranking (0-4s), then releases stored energy to drive air pump at 800-1000W during seconds 4-34 of cold start
  • Integrate state-of-charge monitoring circuit with temperature compensation (−40°C to +85°C operating range) ensuring minimum 25kJ stored energy available, sufficient for 30-second high-flow air injection cycle delivering 15-20g oxygen mass to catalyst
Expected Effect : Catalyst light-off in 28-32s; zero cold-start electrical load; 65-75% emission reduction
Risk Control :
  • capacitor degradation below −20°C reducing available energy
  • charge circuit failure preventing pre-charge completion
  • relay contact resistance causing voltage drop during discharge
Patsnap Eureka Solution