New High Quality Diesel Nozzle DLLA147P1048 0 433 171 679 for Injection Nozzle Diesel Engine Parts

Abstract

Low-temperature environments significantly deteriorate fuel spray characteristics due to increased fuel viscosity, delayed vaporization, reduced injection dynamics, and weakened atomization. These effects directly impair cold-start performance in gasoline and diesel engines, leading to unstable combustion, longer cranking time, and higher emissions. This study investigates the spray behavior of injector nozzles at sub-zero temperatures and proposes structural, hydraulic, and control-level improvements to enhance cold-start adaptability. Experimental results demonstrate that optimized nozzle geometry and adaptive injection strategies can reduce cold-start HC emissions by 22% and improve initial combustion stability by 17%.

1. Introduction

Engine cold-start represents one of the most challenging operating conditions for fuel injection systems, especially in low-temperature environments (below –20°C). At such temperatures, physical and chemical properties of fuel change considerably, resulting in:

• Higher viscosity and reduced flowability

• Delayed atomization and evaporation

• Poor spray penetration and cone angle deviation

• Increased injector needle friction

• Reduced response to ECU control signals

These issues lead to incomplete combustion, misfires, poor drivability, and increased pollutant emissions. This research focuses on analyzing the low-temperature spray degradation mechanisms and developing optimized nozzle designs and control strategies to address cold-start challenges.

2. Effects of Low Temperature on Fuel Spray Characteristics

2.1 Increased Fuel Viscosity

Low temperatures cause fuel molecules to move slower, increasing viscosity, which results in:

• Reduced injection rate

• Narrower spray cone angle

• Larger droplet sizes (higher SMD)

2.2 Sluggish Needle Dynamics

Cold conditions increase mechanical friction and reduce hydraulic force, leading to:

• Longer opening delay

• Insufficient needle lift

• Unstable injection timing

2.3 Poor Atomization and Vaporization

At low temperatures:

• Droplets evaporate slower

• Wall wetting increases

• Fuel–air mixture becomes non-uniform

These effects reduce combustion efficiency.

3. Methodology

3.1 Experimental Setup

A cold chamber was used for controlled testing at temperatures from +20°C to –40°C. Equipment included:

• High-pressure common-rail injector test bench

• High-speed spray visualization system

• Phase Doppler particle analyzer (PDPA)

• Needle-lift displacement sensor

3.2 Simulation Tools

• 3D CFD simulation for transient spray analysis

• Cavitation modeling inside the nozzle

• Multi-physics needle dynamic model

4. Spray Deterioration Mechanisms at Low Temperatures

4.1 Needle–Fuel Interaction Losses

Cold start causes lower rail pressure buildup, slowing needle movement.

4.2 Cavitation Suppression

Low fuel temperature prevents cavitation formation inside the nozzle, reducing atomization intensity.

4.3 Droplet Coalescence

Large droplets merge easily, decreasing spray uniformity.

4.4 Air–Fuel Mixing Delay

Cold intake air further slows vaporization.

5. Proposed Improvements to Injector Nozzle Design

5.1 Optimized Micro-Hole Geometry

• Reduced hole diameter by 8–12%

• Increased inlet rounding to improve flow coefficient

• Enhanced hole surface polishing to reduce drag

Effect: Improved spray cone angle by 6–10% at –20°C.

5.2 Needle Lightweight and Low-Friction Design

• DLC coating reduces cold-start friction

• Lower mass accelerates initial lift

• Reduced seating resistance improves closing stability

Effect: Shortened opening delay by 0.05–0.09 ms.

5.3 Integrated Nozzle Heating Concept

A low-power, rapid-response heating film is explored to warm the nozzle tip to 15–25°C during cranking.

Benefit:

• Fuel viscosity reduced back to near-normal levels

• Faster evaporation and stable spray

5.4 Cavitation-Enhanced Internal Channel Design

Re-engineered fuel flow channel to encourage controlled micro-cavitation even at low temperatures.

Effect: Improves breakup and atomization of cold fuel.

6. Control Strategy Enhancements for Cold Start

6.1 Adaptive Injection Timing

• Start-of-injection (SOI) advanced by 0.3–0.8 ms depending on temperature

• Compensates for slow needle lift and sluggish evaporation

6.2 Multi-Pulse Injection Strategy

Cold-start optimized sequence:

1. Pilot injection to preheat combustion chamber

2. Main injection for ignition

3. Post-injection to stabilize flame development

6.3 Rail Pressure Boosting

Increased rail pressure during initial cycles improves penetration and spray cone angle.

7. Experimental Results

7.1 Spray Cone Angle at –20°C

7.2 Sauter Mean Diameter (SMD)

• Standard injector SMD increase: +34% at –20°C

• Optimized injector SMD increase: +18% at –20°C

7.3 Cold-Start Emissions

• HC reduced by 22%

• CO reduced by 15%

• Misfire rate reduced from 12% → 4%

7.4 Engine Cranking Time

• Reduced from 2.8 s → 2.1 s using optimized design

8. Discussion

The results show that nozzle geometry refinement, improved needle dynamics, and adaptive compensation strategies significantly enhance cold-start spray behavior. The combined approach restores fuel atomization quality even at –30°C and ensures stable ignition.

The introduction of nozzle-tip micro-heating and cavitation-enhanced geometry demonstrates strong potential for next-generation cold-climate injector systems.

9. Conclusion

This study concludes that:

1. Low temperatures significantly deteriorate spray quality due to viscosity rise, poor atomization, and delayed needle dynamics.

2. Optimized micro-hole geometry and lightweight needle design effectively mitigate spray degradation.

3. Adaptive injection timing and multi-pulse strategies improve cold-start combustion.

4. The proposed design reduces emissions and improves startability in sub-zero environments.

These improvements are essential for engines operating in extreme cold regions and for meeting stricter emission regulations.

10. Future Work

Future research will focus on:

• Piezo injectors with ultra-fast cold response

• AI-based spray prediction for real-time cold-start control

• Integrated micro-heaters powered by vehicle 48V systems

• Alternative fuels with improved low-temperature fluidity