A gasoline atomizer divides liquid fuel into droplets so that it can evaporate and mix with air. The pressure-swirl arrangement shown here sends liquid tangentially into a chamber and releases it as a hollow cone. Use the animation to follow that path and the calculator to compare ideal liquid-flow scales and cone geometry. Neither the drawing nor those calculations predicts combustion quality.
Gasoline Atomizers Interactive Calculator
Compare pressure difference, discharge-hole diameter and an assumed cone half-angle. The outputs are lossless velocity, circular area, ideal full-bore flow and cone radius 50 mm from a virtual apex. They are not measured injector performance.
Equation Used
Pressure is the difference between upstream liquid and the receiving environment, not rail gauge pressure alone. Ideal full-bore flow assumes the whole hole carries liquid at the lossless speed. Swirl, an air core, contraction, friction and injector timing reduce or alter actual delivery. The cone angle is entered independently; pressure does not calculate it. No droplet-size, evaporation-time or wall-wetting result is provided.
From tangential entry to a hollow cone
The plan view shows liquid entering near the edge of a circular chamber. Tangential entry gives the stream angular motion. The liquid leaves through an axial opening; the side view shows a hollow conical sheet that breaks into droplets farther downstream.
The chamber and outlet remain fixed. Moving markers illustrate the liquid path, while the empty center distinguishes a hollow cone from a solid filled cone. The simplified spiral is a guide to direction, not a computed internal flow field.
The hole symbol changes with the entered diameter and the cone widens with its entered half-angle. Pressure changes the marker pace in proportion to the ideal velocity, at a slowed display scale. Markers have arbitrary sizes and do not represent measured droplets. The orifice and cone are enlarged independently so both remain visible; the picture is not a dimensioned nozzle.
Atomization depends on the complete nozzle
Fuel systems can use air-assisted atomization, pressure-swirl nozzles, pintle injectors or multi-hole injectors. They do not share one universal droplet-size equation. A swirl chamber illustrates one arrangement, rather than every automotive injector.
Industrial hollow-cone nozzle references establish the tangential-entry principle and annular spray pattern. Their water-flow ratings and material options are not gasoline approvals. Fuel compatibility, pressure rating, electrical actuation and installation suitability belong to the actual component specification.
Separate ideal flow from spray geometry
For a liquid starting with negligible velocity, negligible elevation change and no losses, Bernoulli’s equation gives v = √(2ΔP/ρ). Here ΔP is converted from bar to pascals and density is held at an assumed 740 kg/m³. This is a velocity scale, not a measured exit-speed distribution.
The circular hole area is A = πd²/4. Multiplying its full area by v gives the ideal full-bore flow. With A in mm² and v in m/s, Q in mL/min equals 60Av. An actual hollow-cone nozzle has internal losses and may discharge an annular liquid sheet around an air core, so this full-area value is a comparison rather than an injector rating.
At a fixed axial distance L = 50 mm from a virtual cone apex, radius is r = L tan α. The full cone angle is 2α. This geometric calculation ignores the finite nozzle exit, sheet curvature, gravity, air motion and breakup. The radius is not an impact-coverage guarantee.
Example: 3 bar and a 0.20 mm hole
At ΔP = 3 bar and ρ = 740 kg/m³, the lossless velocity is 28.47 m/s. A 0.20 mm diameter circle has area 0.03142 mm², giving ideal full-bore flow 53.67 mL/min. No discharge coefficient, air-core area or pulse duty is applied.
For a 30° half-angle, the full cone angle is 60°. At L = 50 mm, the geometric radius is 28.87 mm. Increasing the half-angle to 45° changes this radius to 50 mm while leaving the ideal-flow calculation unchanged.
Increasing pressure difference from 3 to 6 bar multiplies ideal velocity and flow by √2. Increasing diameter from 0.20 to 0.25 mm multiplies area and ideal flow by 1.5625. These comparisons do not establish how droplet size or combustion would change.
What a real spray assessment also needs
Droplet distributions depend on nozzle construction, pressure, liquid properties, surrounding gas and operating conditions. Sauter mean diameter describes a spray’s volume-to-surface-area relationship; it cannot be inferred here from three geometric and pressure inputs.
Evaporation also depends on temperature, composition and the surrounding gas. Wall wetting depends on spray targeting, airflow and surface conditions. Use component-specific measurements or a validated model for those questions. A pressure or diameter setting in this comparison is not a recommendation to modify a fuel system.
Frequently asked questions
Is the pressure input fuel-rail gauge pressure?
It is the pressure difference driving liquid discharge. Rail gauge pressure alone is insufficient when the receiving environment is above or below atmospheric pressure.
Is ideal full-bore flow the actual injector flow?
No. It assumes the entire circular hole carries liquid at the lossless velocity. Swirl, air-core area, contraction, friction and pulsed operation are not included.
Does the half-angle input change the liquid-flow calculation?
No. It controls the separate geometric cone-radius calculation. Real nozzle angle and flow can be coupled, but that relationship requires nozzle-specific data.
Are the moving dots scaled droplets?
No. They illustrate direction at a slowed pace. Their size and spacing do not represent a droplet distribution or a measured flow field.
Can this predict evaporation time or puddling?
No. It has no fuel-composition, thermal, airflow, surface or breakup model.
Does the drawing represent a particular automotive injector?
No. It is a simplified tangential-entry hollow-cone nozzle. The cited industrial references explain that arrangement, not gasoline compatibility or automotive performance.
Mechanism references
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