Professional Manufacture 0 445 110 081 Diesel Injector Common Rail Injector Engine Parts Vehicle Parts 0445110081

1. Introduction

In extremely cold regions such as Northern Canada, Siberia, and high-altitude areas, diesel engines must often start and operate at temperatures as low as −40°C. Under these conditions, the fuel injector faces issues such as increased fuel viscosity, freezing of micro water droplets, needle-valve sticking, and nozzle-hole ice blockage. These problems lead to injection failure or significant deviation from calibrated injection parameters, resulting in poor cold-start performance and compromised engine reliability.

This study analyzes the ice-formation mechanisms inside injectors at extremely low temperatures and proposes engineering measures to ensure reliable fuel injection under harsh cold-start conditions.

2. Ice-Formation Mechanisms in Injectors at Low Temperatures

2.1 Freezing of Water Microdroplets Inside the Nozzle

Fuel inevitably contains trace amounts of water. When the temperature drops below 0°C, water microdroplets may:

• Crystallize and form ice membranes around the nozzle inlet

• Adhere to the needle-valve guide surface

• Block nozzle holes by forming ice bridges

Result: Reduced injection quantity, deteriorated atomization, misfire, and failure to start.

2.2 Mechanical Sticking Caused by Low-Temperature Contraction

Extreme cold leads to:

• Thickened lubrication film between the needle valve and guide

• Reduced material clearance due to thermal contraction

• Mismatched thermal expansion between steel and copper alloys

These result in:

• Needle-valve sticking

• Delayed response

• Increased injection lag

2.3 Deterioration of Atomization Quality

At low temperatures:

• Fuel viscosity increases dramatically

• Spray droplets become larger

• Spray cone angle narrows

• Air–fuel mixing becomes insufficient

Poor atomization worsens combustion, increases white smoke, and makes cold starting more difficult.

3. Performance Degradation of Injectors at −40°C

4. Engineering Measures for Ice-Blocking Prevention

4.1 Structural Improvements to the Injector

(1) Hydrophobic Micro-Structured Nozzle Inlet

• Hydrophobic coating (e.g., DLC, TiN)

• Contact angle >120°

• Prevents ice adhesion and crystallization

(2) Optimized Needle–Guide Clearance

• Maintains clearance even under thermal contraction

• Incorporates micro-lubrication grooves for cold conditions

(3) Local Thermal Management

• Integrated micro heating film (used in some advanced injectors)

• 1–2 seconds of rapid de-icing via resistive heating

4.2 Fuel System Improvements

(1) Low-Temperature Flow Improvers

Enhance low-temperature operability by:

• Reducing viscosity

• Preventing wax crystal growth

• Lowering cold filter plugging point (CFPP)

(2) Advanced Water Management

• High-efficiency water separator

• Real-time water-in-fuel (WIF) sensor

• Water scavenger additives

4.3 ECU-Based Compensation Strategies at −40°C

(1) Preheating Injection (Pilot Heating Injection)

A very small pre-injection is used to:

• Warm the nozzle tip

• Increase fuel temperature locally

• Reduce ice-blocking tendency

(2) Increased Drive Current

To overcome additional resistance caused by ice and thickened fuel film.

(3) Adaptive Rail-Pressure Control

• Higher pressure → improves atomization

• Lower pressure → reduces injector mechanical load when ice-blocking is suspected

ECU uses real-time signals to switch modes intelligently.

(4) Injector Self-Diagnosis and De-Icing Mode

ECU detects abnormalities in return flow and activates:

• High-frequency needle vibration

• Intermittent heating (if heating element exists)

• Controlled pressure pulsing

5. Reliability Verification Methods

5.1 Low-Temperature Chamber Testing

Simulated tests at −20°C / −30°C / −40°C:

• Repeated cold starts

• Rail-pressure response evaluation

• Spray imaging and injection waveform analysis

5.2 Ice-Blocking Sensitivity Testing

Fuel is conditioned with controlled water content (50–200 ppm) to evaluate freezing effects.

5.3 Needle-Valve Dynamics Testing

Using laser displacement sensors and high-speed imaging to measure:

• Needle response delay

• Sticking probability

• Motion attenuation at low temperatures

6. Conclusion

At −40°C, injectors suffer from ice formation, increased viscosity, and mechanical contraction effects. These issues cause injection-quantity deficits, delayed response, and poor atomization. Through structural anti-icing design, fuel-treatment methods, and intelligent ECU compensation, the injection reliability under extreme cold-start conditions can be significantly improved. This provides strong technical support for diesel engines operating in severe winter environments.