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Instrumentation and Techniques for Vehicle Refueling Emissions Measurement
The SAE J1045 Recommended Practice provides a standardized procedure for measuring hydrocarbon emissions during the refueling of passenger cars and light trucks. This method, utilizing a Sealed Housing for Evaporative Determinations (SHED), allows engineers to investigate the impact of temperature, fuel volatility, and control system effectiveness on refueling emissions. Below, we explore the key components of this standard and provide practical insights for implementation.
Understanding Refueling Emissions
Refueling losses comprise four primary sources: displaced fuel tank vapor, entrained fuel droplets in the displaced vapor, liquid spillage, and nozzle drip. Displaced vapor typically accounts for over 90% of total losses. The SHED technique measures the aggregate hydrocarbon emissions from these sources in a single test. Fuel properties such as Reid Vapor Pressure (RVP) and distillation characteristics significantly influence emission levels. For standard tests, an RVP of 62 kPa ± 2 kPa is specified.
| Property Group | ASTM Test Method |
|---|---|
| Distillation (IBP, 5%, 10%, 15%, 20%, 30%, 40%, 50%, 90%, FBP) | D 86 |
| Reid Vapor Pressure | D 323 |
| Hydrogen-Carbon Ratio (vapor and liquid) | D 3343 |
Key Temperature Conditions
Ambient: 27°C ± 1.7°C
Fuel delivery: 19.4°C ± 0.8°C
Residual fuel: 27°C ± 1.7°C at test start
Ambient: 27°C ± 1.7°C
Fuel delivery: 19.4°C ± 0.8°C
Residual fuel: 27°C ± 1.7°C at test start
Test Facility and Equipment Setup 🛠️
Proper facility setup is critical for accurate measurements. The SHED must have internal dimensions of at least 3.1 × 6.7 × 2.6 m and be constructed with hydrocarbon-impermeable surfaces. A refueling hose and nozzle penetrate the enclosure wall with a gas-tight seal, and sealed armholes allow operator access from outside.
The fuel conditioning unit must deliver fuel at 19.4°C ± 0.8°C and a flow rate between 15.9 and 37.1 L/min. Thermocouples (type J, fast response) are placed in the residual fuel, vapor space, fuel conditioner, dispensed fuel nozzle, displaced vapor location, and enclosure. A multichannel recorder with 0.5°C accuracy and 1-second resolution is required.
Fuel tank preparation includes draining to the residual level, adding 10% of tank capacity for standard tests, and heating the tank to 27°C ± 1.7°C. Heating can be achieved by a 6- to 24-hour vehicle soak or an electric heating pad covering at least 50% of the wetted area. Engineers must avoid hot spots and never apply heat directly to the vapor space; vapor temperature should not exceed liquid temperature by more than 3°C.
The evaporative canister must be loaded and purged according to CFR 40 Part 86, 88, and 600 prior to testing. A pressure test of the entire fuel system (14.4 psig ± 0.5 psig for 20 minutes) ensures integrity.
⚠️ Common Mistakes
Avoid applying heat directly to the vapor space in the fuel tank, as this can cause local overheating and inaccurate results. Always use proper fuel sampling procedures (prechilled container, bottom fill, minimum headspace) to retain volatile components.
Avoid applying heat directly to the vapor space in the fuel tank, as this can cause local overheating and inaccurate results. Always use proper fuel sampling procedures (prechilled container, bottom fill, minimum headspace) to retain volatile components.
Measurement Methodology and Best Practices 🔍
The measurement procedure begins with sealing the vehicle inside the SHED at the specified ambient condition. Initial hydrocarbon concentration is recorded. The refueling operation is then performed using conditioned fuel, and final hydrocarbon concentration is measured. Total refueling emissions are calculated from the concentration change, accounting for the SHED volume.
Fuel sampling for inspection must be done at the start of the test using a 1 L container prechilled to 4°C. The container is bottom-filled to overflow and then emptied to 80% capacity before sealing and storage. For alcohol-blended fuels, note that flame ionization detector sensitivity is reduced, so alternative analytical techniques may be needed.
Throughout the test, ambient temperature must be maintained within 27°C ± 1.7°C, and the fuel delivery temperature must be held at 19.4°C ± 0.8°C. These conditions ensure repeatable results that can be compared across different vehicles and control systems.
Frequently Asked Questions
- What is the purpose of the SHED in refueling emissions measurement? The SHED provides a sealed environment to capture all refueling-related hydrocarbon emissions, allowing accurate quantification of displaced vapor, entrained droplets, spillage, and nozzle drip.
- What are the standard fuel temperature and pressure conditions? For standard tests, fuel should have a Reid Vapor Pressure of 62 kPa ± 2 kPa. The fuel delivery temperature is 19.4°C ± 0.8°C, and the residual fuel temperature before refueling is 27°C ± 1.7°C.
- How should the fuel tank be heated prior to testing? The vehicle can be soaked at 27°C ± 1.7°C for 6–24 hours, or a heating pad covering at least 50% of the wetted area can be used. Avoid heating the vapor space directly.
- Why is fast-response thermocouple placement important? Vapor temperature changes quickly during refueling. Fast-response thermocouples provide accurate temperature measurements for calculating vapor loss and ensuring proper thermal conditioning.
Adhering to SAE J1045 ensures reliable and repeatable measurement of refueling emissions, supporting the development of effective evaporative control systems and compliance with regulatory requirements.
