Author: Vanessa 11 Apr. 2025 Category: Applications
Ⅰ. Multi-physics coupling mechanism of oil mist formation
The generation of oil mist in metal cutting is the result of the synergistic effect of multiple physical mechanisms, which mainly includes three key stages:
(1) Primary atomization stage: When the cutting speed exceeds the critical value (usually 120m/min for turning and 90m/min for milling), an unstable viscous shear layer is formed between the tool rake face and the chip. According to the Reynolds number (Re>2300), the fluid enters a turbulent state, resulting in capillary breakage of the liquid film. Experimental data show that the particle size of the oil droplets produced at this time is mainly distributed in the range of 50-200μm.
(2) Secondary atomization stage: The high-speed rotating workpiece and tool (usually with a speed exceeding 8000rpm) exert a strong centrifugal effect on the primary oil droplets, with an acceleration of up to 3000g. In this process, the oil droplets are further broken into fine particles of 10-50μm. Computational fluid dynamics (CFD) simulation shows that the atomization efficiency at this stage is negatively correlated with the dynamic viscosity of the cutting fluid. When the viscosity drops from 46cSt to 32cSt, the atomization amount increases by about 40%.
(3) Thermal evaporation-condensation stage: The temperature in the cutting zone can reach 600-800℃, causing about 5-15% of the cutting fluid to flash. Subsequently, in a cooler workshop environment, these vapors recondense into ultrafine particles of 0.1-1μm. Mass spectrometry analysis shows that these particles contain higher concentrations of polycyclic aromatic hydrocarbons (PAHs), and their equivalent concentration of benzo[a]pyrene can reach 3-5 times that of conventional particles.
Ⅱ. Classification system and technical characteristics of metal processing oil mist
Oil mist in industrial environments can be classified in multiple dimensions according to its formation mechanism, physical properties and chemical composition. Different types of oil mist require targeted control strategies. Based on ISO 18757 and ASTM E2516 standards, the systematic classification of oil mist is as follows:
(1) Classification by formation mechanism
- Formation conditions: cutting speed>80m/min, fluid Reynolds number Re>2500
- Particle size distribution: 10-100μm (modal diameter about 35μm)
Typical characteristics:
- Droplets are spherical, and surface tension dominates the morphology
- Contains the original components of the cutting fluid (base oil + additives)
- Accounts for 65-75% of the total oil mist
- Formation conditions: cutting zone temperature>400℃
- Particle size distribution: 0.1-1μm (modal diameter 0.3μm)
Typical characteristics:
- Particles are mostly in irregular aggregates
- Rich in thermal decomposition products (PAHs, aldehydes)
- 15-25% of the total oil mist
- Formation conditions: local temperature > 650℃ and lack of oxygen
- Particle size distribution: 50-300nm (modal diameter 80nm)
Typical characteristics:
- Organic layer coated on the carbon core
- Contains metal oxides (Fe3O4, Cr2O3, etc.)
- 5-10% of the total oil mist
(2) Classification by fluid type
- Base oil: mineral oil (C20-C50 hydrocarbons)
- Typical viscosity: 32-68cSt@40℃
- Health risks:
- • Benzo[a]pyrene content: 0.8-3.2μg/m³
- • Respiratory deposition rate: 35-45%
Emulsion oil mist Mist
- Composition: 30-50% mineral oil + water + emulsifier
- Conductivity: 2-5mS/cm
- Special issues:
- • Microbial growth (>10⁶ CFU/mL)
- • Formaldehyde release: 0.2-0.8mg/m³
Synthetic Fluid Aerosol
- Main ingredients: polyether, ester compounds
- Volatile organic compounds (VOC): 150-400ppm
- Environmental behavior:
- • Ozone generation potential: 0.4-0.7
- • Biodegradability (BOD5/COD): 0.3-0.6
(3) Classification by particle size distribution (according to ISO12103-1)
| Category | Particle size range | Mass percentage | Main hazard mechanism |
| Inhalable particles | 0.1-5μm | 55-65% | Alveolar deposition (deposition rate>30%) |
| Chest particles | 5-10μm | 25-35% | Bronchial retention |
| Head particles | >10μm | 10-15% | Upper respiratory tract irritation |
III. Comparison of oil mist characteristics measurement technology
| Detection method | Applicable particle size range | Accuracy | International standard |
| Laser diffraction method | 0.1-1000μm | ±3% | ISO 13320 |
| Electrostatic low-pressure impactor | 0.01-10μm | ±15% | ASTM D6832 |
| Optical particle counter | 0.3-10μm | ±10% | ISO 21501-4 |
| Weighing method | >1μm | ±5μg | NIOSH 0500 |
Different types of oil mist require different control strategies:
- For mechanical atomization oil mist: centrifugal separation is recommended (efficiency>85%)
- For thermal evaporation oil mist: HEPA filtration is required (efficiency>99.97%)
- For MQL aerosol: electrostatically enhanced coalescence technology is recommended
IV. In the context of the green transformation of the global manufacturing industry, Trenntech’s innovative affinity coalescence technology redefines the standard paradigm of oil mist treatment. Its core value is reflected in three dimensions:
- Technological advancement: ultra-efficient capture of oil mist particles (99.97%@0.1μm) is achieved through molecular-level surface engineering design
- Economic sustainability: 42% lower energy consumption and 60% lower maintenance costs than traditional solutions, with a payback period of <2 years
- Environmental friendliness: meets the most stringent ISO 14000 environmental management system requirements and helps companies achieve carbon neutrality goals
With the application of intelligent monitoring systems and new nanocomposites, Trenntech solutions are gaining wider recognition around the world. In the future, with the in-depth development of Industry 4.0, Trenntech will continue to lead the evolution of oil mist control technology towards intelligence and precision, and provide key technical support for the sustainable development of the global manufacturing industry.