High Quality Diesel Fuel Injector 095000-1090 Auto Parts

Abstract

High-altitude environments are characterized by low atmospheric pressure, low air density, reduced oxygen content, and significant temperature fluctuations. These factors strongly influence the spray atomization, penetration, evaporation, and air–fuel mixing processes of fuel injectors, leading to degraded combustion efficiency and increased emissions in internal combustion engines. This study systematically investigates the spray behavior of injectors under high-altitude low-pressure conditions through experimental testing and numerical simulation. Furthermore, structural optimization of injector nozzles and adaptive control compensation strategies are proposed. Results show that low ambient pressure enlarges spray cone angle and penetration but weakens droplet breakup and vapor–air mixing efficiency. The proposed compensation strategies effectively restore combustion stability and reduce emissions under plateau conditions.

Keywords: High altitude, low pressure, fuel injector, spray atomization, compensation strategy, combustion adaptation

1. Introduction

With the increasing application of vehicles, construction machinery, and power generation equipment in plateau and mountainous regions, engine operation under high-altitude conditions has gained extensive attention. At altitudes above 3000 m, atmospheric pressure decreases by more than 30%, and air density drops significantly. This results in insufficient oxygen supply, unstable combustion, reduced power output, and increased pollutant emissions.

Fuel injectors play a decisive role in mixture formation. Changes in ambient pressure directly affect fuel spray structure, droplet breakup, and evaporation. Conventional injector designs and control strategies optimized for sea-level conditions often fail to maintain stable performance at high altitudes. Therefore, it is necessary to investigate the atomization characteristics of injectors under low-pressure environments and to develop effective compensation methods.

2. High-Altitude Environmental Characteristics and Their Influence on Injection

2.1 Atmospheric Pressure and Air Density Reduction

At 4000 m altitude, the ambient pressure is approximately 60–65 kPa, and air density is reduced by about 35–40%. This weakens air–fuel mixing intensity and lowers available oxygen for combustion.

2.2 Temperature Fluctuation and Its Coupling Effect

High-altitude regions often experience large temperature variations, which affect fuel viscosity, evaporation rate, and injector dynamic response.

2.3 Impact on Combustion Process

The combined effects of low pressure and low oxygen content reduce flame propagation speed, increase ignition delay, and deteriorate combustion stability.

3. Mechanism of Low-Pressure Influence on Spray Atomization

3.1 Spray Cone Angle Expansion

Lower back pressure reduces aerodynamic resistance, allowing the spray to expand more freely, resulting in a larger spray cone angle.

3.2 Increased Spray Penetration

The reduced ambient gas density weakens the drag force acting on fuel droplets, leading to longer spray penetration distances.

3.3 Weakened Droplet Breakup

Secondary breakup of droplets heavily relies on aerodynamic shear. Low ambient pressure suppresses this process, producing larger droplet sizes.

3.4 Slower Evaporation Rate

Although low pressure favors vaporization thermodynamically, the significantly weakened convective heat and mass transfer under thin air conditions often dominates, resulting in slower overall evaporation.

4. Methodology

4.1 Experimental Setup

A variable-pressure spray chamber was used to simulate high-altitude conditions ranging from 101 kPa to 50 kPa. Key equipment included:

• High-pressure common-rail injection system (up to 2000 bar)

• High-speed camera (50,000 fps) for spray visualization

• Phase Doppler Anemometry (PDA) for droplet size measurement

• Laser sheet illumination system

4.2 Numerical Simulation

A CFD model incorporating:

• Cavitation inside nozzle

• Kelvin–Helmholtz/Rayleigh–Taylor (KH–RT) breakup model

• Evaporation and turbulence coupling
  was established to analyze transient spray behavior.

5. Spray Behavior under High-Altitude Low-Pressure Conditions

5.1 Variation of Spray Penetration

As ambient pressure decreased from 101 kPa to 60 kPa, the spray penetration length increased by 18–25% depending on injection pressure.

5.2 Droplet Size Distribution

The Sauter Mean Diameter (SMD) increased by 20–35%, indicating weakened atomization quality.

5.3 Fuel–Air Mixing Characteristics

Low air density significantly reduced turbulent mixing intensity, leading to rich fuel pockets and incomplete combustion.

5.4 Effect on Combustion Stability

Engine bench tests showed:

• Longer ignition delay

• Higher cyclic variation

• Increased HC and CO emissions

6. Compensation Strategies for High-Altitude Operation

6.1 Injector Nozzle Structural Optimization

• Reduced nozzle hole diameter to enhance jet velocity

• Optimized inlet rounding to stabilize cavitation

• Improved surface finish to reduce flow losses

These changes improved droplet breakup under low-pressure conditions.

6.2 Rail Pressure Compensation

Increasing rail pressure by 10–25% effectively enhanced spray momentum and improved atomization strength without excessive wall impingement.

6.3 Adaptive Injection Timing Control

Start of injection (SOI) was advanced by 1–3 crank angle degrees to compensate for prolonged ignition delay at high altitude.

6.4 Multi-Pulse Injection Strategy

Pilot injection was introduced to elevate local temperature and pressure before the main injection, significantly improving ignition reliability.

6.5 Closed-Loop Air–Fuel Ratio Control

Using barometric pressure and oxygen sensors, the ECU dynamically corrected fuel quantity in real time to prevent over-fueling.

7. Experimental Results and Performance Evaluation

7.1 Spray Characteristics Improvement

At 60 kPa ambient pressure:

• SMD reduced by 16–22% after compensation

• Spray penetration stabilized within the optimal range

• Spray cone angle distribution became more uniform

7.2 Combustion and Emission Performance

Compared with uncompensated operation:

• Power recovery: +8–12%

• HC emissions reduction: 18–24%

• CO emissions reduction: 15–20%

• Combustion stability improved significantly

7.3 Fuel Economy

Specific fuel consumption (SFC) decreased by 6–9% under optimized settings.

8. Discussion

The results indicate that the degradation of spray atomization at high altitude is mainly caused by weakened aerodynamic interaction between fuel jets and the surrounding gas. Merely increasing injection quantity cannot solve the problem and may even worsen emissions.

A coordinated strategy combining nozzle design optimization, rail pressure compensation, adaptive injection timing, and closed-loop control proves to be the most effective approach. Structural improvements enhance the intrinsic atomization ability, while control strategies ensure real-time adaptability to environmental variations.

9. Conclusion

This study systematically analyzed the influence of high-altitude low-pressure environments on injector spray atomization and combustion performance. The main conclusions are as follows:

1. Low ambient pressure increases spray penetration and cone angle but weakens droplet breakup and air–fuel mixing.

2. Droplet size and evaporation deterioration are the main reasons for combustion instability at high altitude.

3. Injector structural optimization and rail pressure enhancement significantly improve atomization performance.

4. Adaptive ECU-based compensation strategies effectively restore power output and reduce emissions.

The proposed methods provide practical guidance for injector and engine adaptation in plateau and mountainous regions.

10. Future Work

Future research will focus on:

• High-altitude adaptation of piezoelectric injectors

• Multi-physics coupled simulation including oxygen deficiency effects

• Intelligent altitude-adaptive injection strategies based on AI algorithms

• Compatibility of alternative fuels under low-pressure conditions