New High Quality Diesel Nozzle DLLA155P1514 0 433 171 935 for Injection Nozzle Diesel Engine Parts

Abstract

Accurate characterization of fuel injector nozzle spray behavior is essential for optimizing mixture formation, combustion efficiency, and emission performance of internal combustion engines. Conventional spray test methods based on single imaging or indirect measurement techniques cannot simultaneously capture macroscopic spray morphology and microscopic droplet size distribution with high temporal resolution. To address this limitation, a comprehensive injector spray testing system integrating high-speed photography and laser particle size analysis is developed in this study. The system enables synchronized visualization of transient spray evolution and real-time measurement of droplet size distribution under various injection pressures and ambient conditions. Experimental results demonstrate that the proposed system provides high repeatability, strong adaptability, and superior diagnostic capability for injector performance evaluation.

Keywords: Fuel injector, spray characteristics, high-speed photography, laser particle size analyzer, droplet size distribution, test system

1. Introduction

Fuel injection and atomization quality directly determine mixture formation, combustion stability, fuel economy, and exhaust emissions in modern gasoline and diesel engines. As emission regulations become increasingly stringent and engine technologies evolve toward high pressure and multi-injection strategies, precise measurement of injector spray characteristics has become a critical requirement for both fundamental research and industrial development.

Spray behavior exhibits strong transient and multi-scale characteristics, including macroscopic parameters such as penetration length, spray cone angle, and spatial distribution, as well as microscopic parameters such as droplet size, velocity, and number density. Traditional optical visualization techniques can only provide macroscopic spray information, while laser particle analyzers focus mainly on statistical droplet size distribution at fixed locations. A single measurement method cannot fully reflect the complex spray process.

Therefore, this study develops an integrated spray test system based on the synchronized application of high-speed photography and a laser particle size analyzer, achieving comprehensive measurement of injector spray characteristics across multiple time and spatial scales.

2. Measurement Principles

2.1 High-Speed Photography for Spray Visualization

High-speed photography captures transient spray evolution by recording images at frame rates up to tens of thousands of frames per second. Key spray parameters obtained include:

• Spray penetration length

• Spray cone angle

• Spray boundary and shape

• Spray breakup and dispersion process

Combined with backlight or Schlieren illumination, high-speed imaging can clearly show the jet breakup process, shock wave structures, and vapor–liquid interface dynamics.

2.2 Laser Particle Size Analysis

The laser particle size analyzer is based on laser diffraction and scattering theory. As fuel droplets pass through the laser beam:

• Larger droplets scatter light at small angles

• Smaller droplets scatter light at larger angles

By analyzing the scattered light intensity distribution, the droplet size distribution and statistical parameters can be obtained, including:

• Sauter Mean Diameter (SMD)

• D10, D50, D90

• Droplet number density

This method enables rapid, non-contact, and high-accuracy measurement of spray microstructure.

2.3 Integrated Measurement Concept

The proposed system synchronizes:

• Injection signal

• High-speed camera triggering

• Laser particle size analyzer data acquisition

Thus, macroscopic spray evolution and microscopic droplet characteristics can be measured simultaneously under identical operating conditions.

3. System Architecture

3.1 Overall Layout

The integrated spray test system consists of:

1. High-pressure fuel supply and control unit

2. Injector driving and triggering module

3. Constant-volume spray chamber

4. High-speed photography subsystem

5. Laser particle size analysis subsystem

6. Synchronization and data acquisition system

7. Data processing and analysis software

All subsystems are centrally controlled to ensure time-synchronized operation.

3.2 High-Speed Photography Subsystem

Main components include:

• High-speed CMOS camera (up to 50,000 fps)

• Pulsed LED or xenon strobe light source

• Optical lenses with adjustable focal length

• Optical window-equipped spray chamber

The camera is triggered by the injector control signal to ensure accurate timing between injection start and image acquisition.

3.3 Laser Particle Size Analysis Subsystem

This subsystem includes:

• High-coherence laser emitter

• Multi-angle photodetector array

• Beam expander and alignment optics

• Signal acquisition and inversion algorithm module

The laser measurement volume is aligned with the main spray axis at a specified downstream distance from the nozzle exit.

3.4 Synchronization and Control System

A programmable timing controller ensures:

• Synchronous triggering of injector pulse

• High-speed camera exposure timing

• Laser particle analyzer sampling

Time synchronization accuracy reaches microsecond level, enabling precise correlation between spray images and droplet size data.

4. Experimental Methodology

4.1 Test Conditions

Tests were conducted under the following conditions:

• Injection pressure: 40–200 MPa

• Injection duration: 0.4–2.0 ms

• Ambient pressure: 0.1–1.0 MPa

• Ambient temperature: 20–120 °C

• Test medium: ISO calibration oil and diesel fuel

4.2 Data Acquisition Procedure

1. Set injection pressure and pulse width.

2. Trigger injector, camera, and laser analyzer simultaneously.

3. Record spray images and droplet size data for multiple injection cycles.

4. Perform ensemble averaging for statistical reliability.

4.3 Data Processing

• Spray penetration length extracted using image threshold segmentation.

• Spray cone angle calculated based on boundary fitting.

• Droplet size distribution obtained from laser scattering inversion.

• Time-resolved macroscopic and microscopic data are synchronized using a unified time stamp.

5. System Performance Evaluation

5.1 Temporal Resolution

• High-speed image interval: 20 μs

• Laser particle sampling frequency: up to 10 kHz

• Synchronization error: < 2 μs

5.2 Measurement Accuracy

• Penetration measurement uncertainty: ±1.5%

• Cone angle uncertainty: ±1.2°

• SMD measurement repeatability: ±2.0%

5.3 System Stability and Repeatability

Repeated tests under identical conditions showed:

• Less than ±2.5% variation in penetration length

• Less than ±3% variation in SMD

This demonstrates excellent system stability and repeatability.

6. Comprehensive Spray Characteristic Analysis

6.1 Transient Spray Evolution

High-speed imaging revealed three typical stages:

1. Initial jet formation

2. Ligament breakup and atomization

3. Spray plume development and dispersion

The time-resolved penetration curve showed rapid growth within the first 0.3 ms followed by a gradual stabilization.

6.2 Droplet Size Distribution Characteristics

Laser particle size analysis showed:

• SMD decreased with increasing injection pressure

• High ambient pressure led to smaller droplet sizes

• Multi-injection reduced SMD and narrowed droplet size distribution

6.3 Correlation between Macro and Micro Parameters

By synchronizing macroscopic and microscopic data:

• Faster penetration growth correlated with larger initial droplet sizes

• Stronger spray dispersion corresponded to smaller SMD values

• High cavitation intensity inside the nozzle resulted in finer droplets

These correlations provide important insight into the atomization mechanism.

7. Application Case Study

The integrated system was applied to evaluate two common-rail diesel injector nozzles with different hole geometries. Results showed:

• Nozzle A exhibited stronger penetration but larger SMD

• Nozzle B showed wider cone angle and finer droplets

• Nozzle B demonstrated superior combustion adaptability based on comprehensive spray evaluation

This confirms the effectiveness of the system for injector design optimization and quality evaluation.

8. Discussion

Compared with traditional single-method spray test systems, the proposed integrated system offers the following advantages:

1. Multi-scale measurement capability combining macro spray shape and micro droplet size.

2. High temporal synchronization, enabling accurate transient analysis.

3. Strong adaptability to different fuels, pressures, and ambient conditions.

4. High diagnostic capability for injector design evaluation, fault detection, and performance optimization.

The main limitations include higher system cost and strict optical alignment requirements, which will be optimized in future work through modularization and automated calibration.

9. Conclusion

A comprehensive injector nozzle spray testing system based on high-speed photography and laser particle size analysis was successfully developed and validated. The system enables synchronized acquisition of transient spray morphology and droplet size distribution with high accuracy and repeatability. Experimental results demonstrate that the system can effectively characterize injection and atomization performance under various operating conditions and provide reliable technical support for injector design optimization and engine combustion research.

10. Future Work

Future research will focus on:

• Integration with Schlieren and PIV (Particle Image Velocimetry) techniques

• Application to alternative fuels such as hydrogen, ammonia, and alcohol fuels

• Real-time AI-based spray pattern recognition

• Closed-loop spray control and adaptive injection optimization