As part of an effort to shift focus from the emissions performance of pre-production prototypes in certification to the emissions performance of in-use vehicles, the US Environmental Protection Agency (EPA) and the California Air Resources Board (CARB) instituted the “CAP 2000” program. As part of that program, manufacturers are required to retrieve customer-operated in-use vehicles and test their emissions. The EPA and CARB rules contain specific sample size and mileage criteria. The program has been in place for over 15 model years. This paper examines the in-use performance results for 3115 refueling tests, 3844 hot soak+2-day diurnal evaporative emission tests covering five sets of regulatory emission standards, and evaluates several related regulatory issues such as in-use durability and the effectiveness of evaporative on-board diagnostic (OBD) systems.
Abstract In order to reduce tropospheric ozone level, it is necessary to reduce their precursors, including volatile organic compounds (VOC). Currently, CETESB′s mobile sources emissions inventory accounts only VOC emissions occurring in the vehicle operation. To calculate VOC emissions of vehicle powered by gasoline or ethanol during refueling, it is necessary to know the rate of evaporation of these fuels during the process. Knowing these rates, it is possible to calculate the emissions for each fuel and add this value to the previous VOC emissions. The results show that the refueling emission is significant and must be included in the annual inventory of mobile sources of SPMA, as well as it is necessary to carry out researches about refueling of fuels sold in Brazil.
Volatile Organic Compounds (VOCs) in Ambient Air - A Case Study at the Vicinity of Fuel Filling Stations in New Delhi, India
Abstract Volatile Organic Compounds (VOCs) present in ambient air are potentially toxic among the air pollutants. They are present in the urban atmosphere due to both exhaust emissions from vehicles and evaporative emissions at fuel filling stations. The present study aims to provide an indication of ambient levels of benzene, a carcinogenic VOC in the immediate vicinity of petrol filling stations in Delhi & National Capital Region (NCR). The monitoring of benzene is conducted across the vicinity of petrol stations to ascertain the effect of outside pollutant concentration on forecourt area. Continuous monitoring of benzene was achieved by an air quality monitoring facility stationed across the selected locations at four selected fuel filling stations. It was observed that the average concentrations of benzene measured during the study ranged between 2.28 ppb - 9.43 ppb.
Knowledge of the concentration field and flammability envelope from a small-scale hydrogen leak is an issue of importance for the safe use of hydrogen. A combined experimental and modeling program is being carried out by Sandia National Laboratories to characterize and predict the behavior of small-scale hydrogen releases. In contrast to the previous work performed by Sandia on large, momentum-dominated hydrogen leaks, these studies are focusing on small leaks in the Froude number range where both buoyant and inertial forces are important or, in the limit, where buoyancy dominates leak behavior. In the slow leak regime buoyant forces affect the trajectory and rate of air entrainment of the hydrogen jet leak and significant curvature can occur in the jet trajectory. Slow leaks may occur from leaky fittings or o-ring seals on hydrogen vehicles or other hydrogen-based systems where large amounts of pressure drop occur across the leak path.
The SAE Fuel Cell Vehicle (FCV) Safety Working Group has published and is developing standards for FCVs and hydrogen vehicles. SAE J2578 was the first document published by the working group. The document is written from an overall vehicle perspective and deals with the integration of fuel cell and hydrogen systems in the vehicle and the management of risks associated with these systems. Since the publishing of SAE J2578, the working group has updated SAE J1766 regarding post-crash electrical safety and is developing SAE J2579 which deals with vehicular hydrogen systems.
A study was performed by Southwest Research Institute™ for the Propane Education and Research Council, under the cooperation and management of the Texas Railroad Commission to study and evaluate current LPG vehicle refueling technology. This study focused on connection systems, over-fill protection, and pumping/dispensing systems. Information was also compiled on the new standard for LPG refueling systems created and adopted by the European Committee for Standardization (CEN). The standard was created to reduce refueling emissions, increase operator safety, and improve the general operation and consumer acceptance level for LPG vehicles. This standard involves the LPG fill nozzle, nozzle receptacle, leakage rates, and pumping systems. This project was conducted in order to establish a firm starting point for the beginning of a standardization process for LPG vehicle refueling in the United States.
This paper proposes methods for measuring dispenser nozzle characteristics considered to be potential inputs to the On-Board Refueling Vapor Recovery (ORVR) design process. In fact, these characteristics are potential design inputs to all refueling design processes. Experiments were conducted to develop test procedures and equipment that provide consistent measurements for the broadest possible range of dispenser nozzles. The feasibility of the proposed methods is demonstrated with some simple measurements conducted on common nozzles.
Methods to quantify the gasoline vapors displaced from a tank when refilling an ORVR vehicle are presented. Three predictive modeling techniques that approximate refueling vapor mass and composition are summarized. Some of these modeling techniques provide a convenient and reasonable approximation of real-life fueling events as demonstrated by testing conducted on production fuel system components. The application of the models to vehicle engineering is demonstrated in examples.
Comparison of Fluorosilicone and Fluorocarbon Elastomers in Onboard Refueling Vapor Recovery Systems
The drive to control airborne automobile emissions will soon encompass sealed systems for onboard capture and reuse of fuel vapors resulting from refueling. In contrast to current systems that are based in the fuel dispensing pump, onboard refueling vapor recovery (ORVR) systems are intended to capture fuel vapor in a filler-neck sealing system, feed it to a holding canister, and bleed it off into the fuel injection system for combustion in the engine. For these systems to be effective, specialized elastomers will be required for collars, seals, and valve components. Not only must these materials resist degradation caused by fuel and fuel vapors, including those of methanol-containing fuels, they must also function over a wide temperature range. This paper discusses performance characteristics of fluorosilicone and fluorocarbon materials in an ORVR environment.
Six European vehicles fitted with carbon canisters have been tested under severe conditions to establish if evaporative losses of volatile organic compounds occur under European driving conditions - so-called “running losses”. The programme entailed the development of a point source measurement technique which has a number of advantages over other methods currently in use. Following the development and validation of the measurement technique, the six vehicles were tested at 28C over a range of driving cycles on a gasoline with a Reid vapour pressure of 90 kPa. None of the vehicles exhibited classical running losses, i.e. losses during higher-speed driving. This was due to the effectiveness of canister purging in these conditions. However, significant volatile organic compound (VOC) losses were observed for several vehicles during idle after a period of driving had heated the fuel. Substantial car-to-car variation was observed in the losses obtained.
Onboard refueling control technology has been successfully applied to two vehicles with 98+% efficiency in tests with 10.5 RVP fuel at 84° F. The Onboard system, which controls exhaust, evaporative, refueling, and so called “running losses”, was constructed out of components found in current automotive evaporative control systems. During refueling, the tank vapors are forced into the enhanced charcoal canister by a flowing liquid seal in the fillpipe. The canister was removed from the engine compartment and mounted within the vehicle frame close to the fuel tank. Each vehicle demonstrates a different possible safe location from a crash worthiness viewpoint. In order to further improve safety by preventing the expulsion of liquid gasoline upon gas cap removal, the orifices in the production tank vent lines were removed so that the fuel tank is at atmospheric pressure at all times. As modified, no significant driveability differences from production vehicles were found.
Refueling emissions from a 1986 Pontiac Grand Am were characterized using 3 test fuels, including a winter, summer and intermediate blend gasoline under a variety of seasonal temperature conditions. The effects of varying fuel volatility (10.1 to 13.3 psi RVP), dispensed fuel temperature (50 to 88°F), and vehicle tank fuel temperature (40 to 108°F), were investigated. Hydrocarbon (HC) emissions ranged from 2.90 to 7.41 grams per gallon of delivered fuel. Detailed hydrocarbon analyses were completed for both the test fuels (dispensed fuel and tank fuel) and the refueling emissions. The average (all test fuels and temperature scenarios) test gasoline composition was 46.1% paraffins, 6.3% olefins, 45.2% aromatics, with an average carbon number of 7.42; the average HC emission rate was 4.69 g/gal; and the average emissions composition was 81.4% paraffins, 12.2% olefins, 5.4% aromatics, with an average carbon number of 4.79.
A dissimilar FCS based on fluidic technology, integrated with a redundant electronic FCS, promises to increase the mission reliability and survivability of high performance aircraft by providing protection from common mode and potential EMI/EMP induced failures. Current emphasis is on developing critical hydrofluidic servoactuation systems and components which will meet demanding requirements for performance, size, weight, reliability and power consumption.
In this study, the refueling habits of customers at service stations were analyzed to determine the amount of gasoline dispensed during refueling, the vehicle fuel tank level prior to and after the refueling event, and the percentage of refueling events which are complete fills. Analysis of a General Motors service station survey conducted in the Detroit, Ml area during the summer of 1986 showed that the average amount of gasoline dispensed is 9.8 gallons. The results also demonstrated that 60.6% of all refueling events were complete fills, and that 73.2% of all gasoline dispensed during refueling is used for complete fills. The average indicated fuel tank level prior to refueling is 18% full and the average indicated fuel tank level after refueling is 84% full. Assuming that fuel usage is linear with time and using the above mentioned fuel tank levels, the average fuel tank level is calculated to be 51% full.
Two technologies for controlling vehicle refueling emissions have been under consideration by the U. S. Environmental Protection Agency. They are vehicle onboard systems and Stage II service station vapor recovery. A 1978 program showed that onboard systems are very effective in controlling refueling emissions with no significant effect on exhaust emissions. The work reported herein shows that vehicle onboard technology can be applied equally well to a car meeting more stringent 1985 exhaust and evaporative emission standards with the latest engine and emission control technology. This work also shows that a vehicle onboard refueling control system can provide substantially improved control of evaporative emissions. Refueling emissions were controlled with 98+% efficiency in tests with 9-to 11.5-psi RVP fuel at 88°F, using a procedure proposed by EPA for possible use in certification testing of vehicle onboard systems.
An investigation was conducted to determine the change in Reid vapor pressure (RVP) which results when gasoline and various gasoline-alcohol blends are mixed. Such mixing occurs in vehicle fuel tanks when a motorist buys gasolines and blends alternately. When mixing a gasoline with a gasoline-alcohol blend of the same RVP, the resulting mixture always had a higher RVP, due to the non-linear effect of alcohol concentration in gasoline on RVP. Even when a blend had a much lower RVP than gasoline, some mixtures of the two still had higher RVP's than the gasoline. When two common commercial blends, 10 percent ethanol and 10 percent Oxinol™ 50, both having the same RVP, were mixed in various proportions there was essentially no change in RVP. The results of this study suggest that the presence of both gasolines and blends in the marketplace can lead to higher in-use evaporative emissions from vehicles, even if the blends meet the same volatility standards as gasoline.
This paper describes the results of a study to examine the effects of various experimental variables on the quantity and composition of emissions associated with motor vehicle refueling. Problems related to accurate laboratory simulation of vehicle refueling are discussed. Preliminary results include emission rates for total hydrocarbons, benzene and 82 other hydrocarbon compounds for a single test vehicle under a variety of temperature and test conditions.
Propane powered vehicles require a method of ensuring that the tank is not filled beyond the 80% volume level. Devices available to control the fuel level were analyzed in regards to basic design and effect of operating environment. Vehicle and lab testing supported the valve analysis. The lack of a reliable and fail safe system resulted in the recommendation to pursue a shutoff system that incorporates a liquid fuel level sensor in the tank and a shutoff mechanism on the fuel dispenser.
This report presents the results of an EPA test program designed to characterize benzene refueling emissions. It also examines several other available benzene refueling emission studies to form a combined data base. The combined data base is used to develop a prediction equation which estimates benzene refueling emissions using the following three parameters: 1) dispensed fuel temperature, 2) difference between fuel tank temperature and dispensed fuel temperature, and 3) benzene concentration in the liquid fuel. The prediction equation then uses information on national average gasoline benzene content and pertinent temperature information to estimate a national average benzene refueling emission factor of 0.048 grams benzene/gallon. This refueling emission factor is combined with the latest nationwide gasoline consumption figures to estimate a national benzene refueling emission inventory.
Onboard refueling control technology has been successfully applied to two vehicles with 98+% efficiency without a vapor seal in tests with 11.8 RVP fuel at 88°F. The elements of the onboard system were constructed out of components similar to those found in current automotive evaporative control systems. The entire system was designed for minimum pressure drop so that a mechanical or liquid seal is not necessary. The flow of fuel into the tank provides enough pressure to force the tank vapors into the canister. Control of evaporative emissions was improved to the extent that the 2 grams/test standard for a 9 RVP fuel was met with a fuel of 11.8 RVP. Effects on tailpipe emissions, and canister size are also discussed.
The concentration of gasoline vapors was measured in the breathing zone of a person. refueling automobiles in both summer and winter. The concentrations of total hydrocarbons ranged from 5 to 1220 ppmC in summer and from 4 to 3210 ppmC in winter. Individual values were affected by wind speed and direction, as well as by body shielding caused by the refueler. Compared to the dispensed gasoline, the refueling vapors were enriched in hydrocarbons with normal boiling points below about 125°F, so that five light paraffins (n-butane, isopentane, iso-butane, n-pentane, and propane) constituted more than 70% of the total carbon in the vapors. The combination of the resulting low concentration of the heavier hydrocarbons in the vapor and the rapid dispersal and dilution of the vapor plume minimizes the brief exposure of refuelers to benzene and the C7, and C8 isoparaffins.
An experimental test program was conducted to determine the detailed hydrocarbon composition of the vapor emitted from a vehicle fuel tank during refueling with gasoline. The composition of the equilibrium vapor in the tank was strongly dependent on the composition of the liquid gasoline, but, as expected, the vapor was composed primarily of the more volatile components of the gasoline. The composition of the vapor could be calculated satisfactorily from the liquid composition, using ideal solution theory. In the refueling tests in which the tank fuel and dispensed fuel were the same, there was little difference in the composition of the equilibrium vapor in the tank before refueling and the vapor expelled during refueling. When the tank fuel and dispensed fuel had different compositions, the vapor expelled during refueling was composed of about two-thirds dispensed fuel vapor and about one-third tank fuel vapor.
Mathematical Prediction of Effects of Gasoline Composition on Reid Vapor Pressure, Refueling Emissions and their Reactivity
Concern over the impacts of changes in gasoline composition on refueling emissions stimulated a search for a simple technique to provide estimates of related fuel parameters. Accordingly, a mathematical computer model was developed based on the assumption that gasoline liquid-vapor equilibria can be predicted with reasonable accuracy from Raoult's law for ideal mixtures. Gasoline fuel parameters such as vapor pressure (including Reid Vapor Pressure, RVP), refueling loss, OH reactivity in forming atmospheric ozone pollution, and other fuel characteristics were addressed. The assumptions made and model results were validated by comparison to measured fuel parameters from 9 unleaded gasoline fuels. Extrapolations were made to illustrate fuel temperature and vapor/liquid ratio effects. Calculated RVP levels were found to be within 5% of measured values for the fuels evaluated.
Information from the literature and from on-going test programs (government and industry) was analyzed with regard to the effect of gasoline Reid vapor pressure (RVP) on total vehicle hydrocarbon (HC) emissions, including evaporative, refueling, and exhaust emissions. A reduction in the average RVP of summer gasolines from present commercial levels to 9 psi was estimated to decrease total vehicle hydrocarbon emissions by 9-25 percent. With such reductions, hydrocarbon emission inventories for three major cities (Detroit, New York, and Dallas) would be decreased by 3-7 percent and, consequently, local ambient ozone levels would be reduced as much as 9 ppb. Accordingly, in many areas of the country, RVP reduction could make an important contribution toward achievement of the National Ambient Air Quality Standard (NAAQS) of 120 ppb ozone.