In gasoline Powertrain systems, the evaporative emission control (EVAP) system canister purge valve (CPV) can be actuated by pulse-width modulated (PWM) signals. The CPV is an electronically actuated solenoid. The PWM controlled CPV, when actuated, creates pressure pulsations in the system. This pulsation is sent back to the rest of the EVAP system. Given the right conditions, the fill limit vent valve (FLVV) inside the fuel tank can be excited. The FLVV internal components can be excited and produce noise. This noise can be objectionable to the occupants. Additional components within the EVAP system may also be excited in a similar way. This paper presents a bench test method using parts from vehicle’s EVAP system and other key fuel system components.
Abstract The following study describes an on-board fuel tailoring process based on a novel and compact catalytic fuel evaporator, capable of optimizing Homogenous Charge Compression Ignition (HCCI) combustion. Evaporation tests with conventional diesel were performed revealing a significant amount of long-chain alkane cracking. As a consequence of these cracking reactions, the presented experiments demonstrate that the produced fuel vapor has altered combustion properties as compared to the feeding diesel stream. Further tests using a constant volume chamber at 30 bar, over the temperature range 500 to 1120 K, indicated that ignition delay time and auto ignition temperature of this fuel vapor can be shifted from diesel to gasoline. Thus, by performing dynamic on-board adjustment of the fuel properties, it is possible therefore to increase HCCI combustion to high loads.
Abstract Carbon canisters are used in gasoline passenger vehicle and light duty truck applications. The component is part of the vehicle emission control system. Activated carbon (also known as charcoal) traps hydrocarbon vapors from the fuel tank and vapors created during the fuel tank refueling and venting events. Canister design, charcoal type and performance have been driven by evaporative emission regulations around the world, and evaporative emission requirements have enhanced through the years. The trend of evaporative emission requirements in Brazil indicates the use of improved carbon canisters in the near future. Carbon canisters are needed to store hydrocarbons that would otherwise pollute the environment. Wood based activated carbon is manufactured from sawdust, which is a renewable resource. The result is a healthier earth on which we live. Figure 1 illustrates the activation process of carbon. Figure 1 Activation process of carbon.
Vehicle Evaporative Emissions Characterization by Chromatographic Techniques Applied to Different Gasoline-Ethanol Blends
Abstract Currently, regulations on vehicle evaporative emissions only focus on the sum of Total Hydrocarbons (THC) without taking into account either the detailed hydrocarbon composition nor other chemicals besides hydrocarbons emitted from gasoline evaporation. As a consequence, this composition, also known as speciation, is not always noted and is even more unknown when biofuels such as ethanol are introduced in the market. Furthermore, these regulations do not differentiate the source of these emissions in the vehicle. The programme described in this paper is designed to investigate the influence of the addition of ethanol to gasoline on evaporative emissions. It has tried to go one step ahead of these directives obtaining more detailed characterization of these evaporative emissions.
Frequency Conversion Controlled Vapor Recovery System by Temperature and Flow Signals: Model Design and Parameters Optimization
Current gasoline-gas vapor recovery system is incomplete, for it cannot adjust the vapor-liquid ratio automatically due to the change of working temperature. To solve this problem, this paper intends to design a new system and optimize its parameters. In this research, variables control method is used for tests while linear regression is used for data processing. This new system moves proportion valve away and adds a DSP control module, a frequency conversion device, and a temperature sensor. With this research, it is clearly reviewed that the vapor-liquid ratio should remains 1.0 from 0 °C to 20 °C as its working temperature, be changed into 1.1 from 20 °C to 25 °C, be changed into 1.2 from 25 °C to 30 °C, and be changed into 1.3 when the working temperature is above 30 °C.
New regulations require small gasoline engine evaporative diurnal emission control. In the past, it was not possible to design a proper evaporative emission control system (it was mostly trial and error design). In this study, a mathematical model was developed for estimating activated carbon canister size and nomographs were developed for estimating canister purge air requirements and diurnal bleed emissions. The model and the nomographs can be used to design an evaporative emission control system for any SI engine fuel system.
Diurnal evaporative emissions from a vehicle's gasoline (petrol) tank are due to the increase in gasoline vapor pressure with ambient temperature over the course of a 24-hour period. Graphical illustrations are used to explain both the mechanism of these emissions and various control methods. The diurnal emissions can be controlled either by using either an activated carbon canister or a sealed/pressurized fuel tank. Mathematical models were developed for estimating tank vapor generation and activated carbon canister volume for storing the tank vapor. Nomographs were developed for estimating the canister purge air requirements and canister bleed emissions. The models and the nomographs can be used for designing an evaporative emission control system for a given vehicle fuel system. Another mathematical model was developed for estimating the sealed/pressurized fuel tank pressure as a function of fuel RVP (Reid Vapor Pressure) and temperature.
Study on Diffusion Behavior of Evaporative Fuel Gas from Gasoline Carbon Canister in Consideration of Temperature-Dependence
It is important to quantify the diffusion behavior of evaporative fuel gas in order to control evaporative emission from carbon canister. Especially, it is necessary to take the changes in adsorption-desorption amount and diffusion coefficients by air temperature into account to design carbon canister satisfying various conditions of air. In this study, we estimated diffusion coefficients in carbon canister for the binary system of butane and nitrogen and examined temperature-dependence of diffusion coefficients. The temperature dependence of diffusion coefficients was not clearly observed. Diffusion coefficient of gas phase increased as the temperature was higher. Amount of desorption decreased as the temperature was raised by contraries. Those effects made the complex temperature dependence of the diffusion coefficient. They caused the density increment and the flow caused by pressure simultaneously.
Evaluation of the Effect of Adding Ethanol to Gasoline at Different Percentages on Evaporative Emissions (Regulated and Non-regulated Pollutants)
Recent interest in ethanol has increased due to the promotion of its use by the authorities and because it can be combined with gasoline at different percentages: low percentages with not specially modified gasoline vehicles and up to 85% of ethanol (even up to 100%), in flexifuel vehicles. The question has arisen of whether the increase in volatility for ethanol/gasoline blends and the presence of ethanol (small molecule compared with the majority of hydrocarbons in gasoline) in the fuel have a significant influence on evaporative emissions, also taking into account permeation through materials used in the fuel system. The long-term effect on emissions of the addition of ethanol also needs to be evaluated. This paper assesses the impact of adding ethanol to gasoline on the evaporative emissions of vehicles by differentiating the sources (complete car, canister and fuel tank) and by differentiating evaporation and permeation effects.
This paper presents a purge system model developed for hybrid electric vehicle (HEV) applications. Assessment of purge capability is critical to HEV vehicles due to frequent engine off operation which limits carbon canister purging. The purge model is comprised of subsystems representing purge control strategy, carbon canister and engine plant. The paper is focused on modeling of the engine purge control feature. The purge model validation and purge capability predictions for an example HEV vehicle are presented and discussed.
VOCs evaporation rate from a poly(vinyl chloride) matrix and its impact over interior's atmospheric composition
With the increase in the market's requirement level and the incited dispute for the consumers, the automotive industry has given special attention to the customer's perceived quality. One of the aspects related to the quality perception is the "new car's smell." The trend, shown by the market, is to control this characteristic in a subjective way, by means of especially trained panel. This paper aims at analyzing this question by another point of view, leaving the subjectivity and searching to characterize the new car's smell in an analytical and concrete way. It was shown that the main VOCs contained in a poly(vinyl chloride) matrix are 2-butanone, acetic acid ethyl ester, toluene, acetic acid butyl ester, cyclohexanone and 1-hydroxycumene. The evaporation rate of the VOCs was studied and its impact in atmospheric global composition evaluated.
Development of Exhaust and Evaporative Emissions Systems for Toyota THS II Plug-in Hybrid Electric Vehicle
Exhaust and evaporative emissions systems have been developed to match the characteristics and usage of the Toyota THS II plug-in hybrid electric vehicle (PHEV). Based on the commercially available Prius, the Toyota PHEV features an additional external charging function, which allows it to be driven as an electric vehicle (EV) in urban areas, and as an hybrid electric vehicle (HEV) in high-speed/high-load and long-distance driving situations. To reduce exhaust emissions, the conventional catalyst warm up control has been enhanced to achieve emissions performance that satisfies California's Super Ultra Low Emissions Vehicle (SULEV) standards in every state of battery charge. In addition, a heat insulating fuel vapor containment system (FVS) has been developed using a plastic fuel tank based on the assumption that such a system can reduce the diffusion of vapor inside the fuel tank and the release of fuel vapor in to the atmosphere to the maximum possible extent.
Analysis of Droplets Evaporation Process of Diesel Spray at Ignition Delay Period using Dual Nano-spark Shadowgraph Photography Method
Evolution of evaporating diesel spray is complex phenomena; however, it is important process for ignition, combustion and emission formation in diesel combustion. In this research, droplets evaporation process at spray boundary was experimentally investigated focusing on the behavior of evaporating droplets during ignition delay period. In the experiment, nano-spark shadowgraph photography technique was applied to a rapid compression machine. This study developed a new optical system to observe spray evaporation process. The existing systems can hardly analyze transitional behavior of vapor phase of spray and droplets behavior in high number-density region. The new technology that is named dual nano-spark shadowgraph photography method can record both macro-scale and micro-scale continuous spray images clearly at very short time interval of 15µsec on normal photographic black and white film.
Renewable Biodiesel/Reference Diesel Fuel Mixtures Distribution in Non-Evaporating and Evaporating Conditions for Diesel Engines
In spite of the recent trend, voted toward the reduction of renewable energy sources deriving from crops, the EC Commission proposes that the proportion of energy from renewable sources in the transportation sector should be at least 20 % of its final energy consumption by the year 2020. In this framework, the activities aiming to study the effects on engine performances, emissions and fuel consumption of alternative diesel fuel receive continue stimulations and supports. In this paper, results of the different behavior of biodiesel fuels in the injection process and their impact on the air-fuel mixture preparation are reported. The injection process characterization has been carried out in a non-evaporative high-density ambient in order to measure the fuel injection rate and the spatial and temporal distribution of the fuel.
A large share of hydrocarbon emissions from vehicles comes from evaporation from vehicles fuel system. Modern vehicles with positive ignition engines have therefore for more than 15 years in Europe been equipped with systems for evaporative control. During the Swedish in service surveillance testing program evaporative emissions were measured on positive ignition vehicles already in operation on road. Results of this program imply a failure rate of more than 30 percent on evaporative emissions. These results differ from a parallel in service surveillance testing program conducted in Germany, where less than 10 percent of the tested vehicles exceeded the limit for evaporative emissions. Based on these results further investigations were started to analyze the evaporative emission of vehicles driven on Swedish roads. One of the major differences between Sweden and Germany that could explain the results was the fuel quality.
The SAE Fuel Cell Vehicle (FCV) Safety Working Group has been addressing FCV safety for over 9 years. The initial document, SAE J2578, was published in 2002. SAE J2578 has been valuable as a Recommended Practice for FCV development with regard to the identification of hazards and the definition of countermeasures to mitigate these hazards such that FCVs can be operated in the same manner as conventional gasoline internal combustion engine (ICE)-powered vehicles. SAE J2578 is currently being revised so that it will continue to be relevant as FCV development moves forward. For example, test methods were refined to verify the acceptability of hydrogen discharges when parking in residential garages and commercial structures and after crash tests prescribed by government regulation, and electrical requirements were updated to reflect the complexities of modern electrical circuits which interconnect both AC and DC circuits to improve efficiency and reduce cost.
Cost Effective Emissions Control Based on Optimized Flex Fuel Electronic Injection for PROCONVE-L5 in Brazil
From January 2009 the new PROCONVE L5 emissions legislation will be in place in Brazil, reducing significantly the current emissions levels. In order to comply with this new legislation, all automakers have to take actions on hardware and electronic fuel injection calibration to meet these new standards. Hardware changes can be efficient, such as increasing the amount of precious metals in the catalyst; however, the cost penalty may turn it unfeasible. The objective of this text is to introduce how an efficient electronic fuel injection calibration, focused on emissions control can be a decisive way to reduce overall product cost. The influence of electronic fuel injection becomes more evident in the current Brazilian reality, where the overwhelming majority of vehicle sales are flexible fuel powered, increasing the challenge and difficulty to correctly control emissions.
Fuel spray impingement and the formation of a fuel film in the intake port of port-injected engines or on the piston crown of direct-injected engines have been shown to result in increased pollutant emissions and reduced engine performance. While models that predict the nature of fuel film evaporation exist, little experimental data on the evaporation characteristics of fuel films have been published. This paper discusses the use of two closely related imaging techniques, shadowgraphy and schlieren photography, to measure the transient evaporation rate, surface area, and thickness of evaporating films, as well as the thickness and concentration distribution of the vapor layer that forms directly above the films. The measurements were conducted in order to better understand the interdependent transport phenomena that control the evaporation process.
This paper describes an innovative dual-layer polymer system comprised of high-density polyethylene (HDPE) and Ixef® polyarylamide that meets EPA (Environmental Protection Agency) and CARB (California Air Resource Board) evaporative emission control standards without the use of multiple layers required in other co-extrusion processed options.
The paper presents the main results obtained by developing and critically comparing different evaporative emissions leak detection diagnostic systems. Three different leak detection methods have been analyzed and developed by using a model-based approach: depressurization, air and fuel vapor compression, and natural vacuum pressure evolution. The methods have been developed to comply with the latest OBD II requirement for 0.5 mm leak detection. Detailed grey-box models of both the system (fuel tank, connecting pipes, canister module, engine intake system) and the components needed to perform the diagnostic test (air compressor or vacuum pump) have been used to analyze in a simulation environment the critical aspects of each of the three methods, and to develop “optimal” diagnostic model-based algorithms.
Reducing evaporation emission is one of the most important targets during vehicle development nowadays. Apart from the emissions while the vehicle is in operation, evaporation emissions occur after the engine is turned off. Up to 30 % of these emissions can originate from the Air Intake System (AIS). Today, Hydro Carbon Adsorbers (HCA) are already used as a part of the AIS to reduce evaporation emissions , . Usually the HCA contains activated carbon or zeolite. HC emissions are adsorbed by the HCA during and after the engine shut down. When the engine is running, the HCA is purged with the intake air. The HC storage principle is well known for carbon canisters . HCAs were initially designed for existing AIS. So far, the pressure drop of the system was considered to be the most important design parameter while designing the AIS. Due to government regulations, more advanced requirements are established and hence sophistication in design is needed to meet new targets.
This paper presents how Computational Fluid Dynamics tool can be used for the numerical evaluation of n-butane adsorption and desorption performance in carbon canister. Formula of material balance within activated carbon particles and formula of material/heat balance within activated carbon packed beds for n-butane as a single component were used in the simulation. These formulas were derived after experiments proved that water vapor in the air do not inhibit the adsorption of n-butane. The experiments and the formulas are described and the significance of the simulation is investigated.
Because of domestic production from renewable sources and their clean burning nature, alcohols, especially ethanol, have seen growing use as a blending agent and replacement for basic hydrocarbons in gasoline. The increasing use of alcohol in fuels raises questions on the safety of these fuels under certain non-operational situations. Modern vehicles use evaporative emission control systems to minimize environmental emissions of fuel. These systems must be relatively leak-free to function properly and are self-diagnosed by the vehicle On-Board Diagnostic system. When service is required, the service leak testing procedures may involve forcing test gases into the “evap” system and also exposure of the fuel vapors normally contained in the system to atmosphere. Previous work has discussed the hazards involved when performing shop leak testing activities for vehicles fuelled with conventional hydrocarbon gasoline [1, 2].
This paper describes the impact of the new evaporative emissions requirements (Euro III/IV) on automotive fuel systems. Fuel system components like carbon canister, fuel tank, filler pipes, fuel lines, vapor management system were reviewed to assure that the design of each component will achieve the new requirements.
This paper discusses an evaporative emissions control system which significantly reduces diurnal evaporative emissions in walk behind lawnmower engines equipped with float carburetors. The system also maintains engine startability, run quality, and a simplistic user interface. The system consists of low-permeation fuel line and a multi-layer fuel tank using an EVOH barrier as well as a carbon canister integrated in the lawnmower's push-handle and an Automatic Bowl Drain System (ABDS). A prototype of the system resulted in a 90% reduction in diurnal evaporative emissions when compared to a pre-regulation walk behind lawnmower using the CARB TP-902 sealed housing for evaporative determination test. This paper demonstrates a practical solution to reduce diurnal evaporative emissions and hydrocarbon running losses below the level emitted from a state of the art, float carbureted, walk behind lawnmower engine.
Effects of Ethanol or ETBE Blending in Gasoline on Evaporative Emissions for Japanese In-Use Passenger Vehicles
Biomass derived ethanol is thought to be a promising gasoline blend stock to reduce carbon dioxide (CO2) emissions from vehicles, and its practical use is under discussion. In Japan, the maximum permissible limit of ethanol content in gasoline is 3 vol%, which almost corresponds to 1.3 mass% of oxygen content, which is defined by gasoline quality standards at present. In addition to ethanol, the use of Ethyl tert-Butyl Ether (ETBE), which is synthesized from biomass ethanol and isobutene, is under discussion as a kind of biomass fuels in Japan. This study examines and discusses the effects of ethanol- and ETBE-blended gasolines on evaporative emissions, especially on refueling loss and diurnal breathing loss (DBL) emissions, from in-use passenger cars in Japan. This study shows that refueling loss emissions don't increase with ethanol- or ETBE-blended gasoline as long as Reid Vapor Pressure (RVP) is adjusted.
The new version of TEE model (Transport Energy Environment) has been developed in the frame of the FP5 ISHTAR and HEARTS Projects with several features for better analyzing transport related direct impacts, taking into account vehicles kinematics, cold start emissions distribution and parking processes. Specific efforts were dedicated to the modeling of the effects of vehicles kinematics on hot emissions, where the software calculates link emissions by adopting average speed based functions, instantaneous emissions, or the innovative ‘kinematics correction functions’ model, and the modeling of parking processes which are relevant for cold start and evaporative emissions.
The barrier properties of fluoropolymers exposed to ethanol-containing fuel blends were investigated using the permeation cup, weight loss method. More specifically, permeation constant data for Fuel C, CE10, CE15, CE22, CE50, CE85 and ethanol through fluoropolymers; THV, PVDF and FEP were measured at 20, 40 and 60°C. Additional techniques such as the measurement of vapor pressure of fuel-ethanol blends using a permeation cup equipped with a pressure transducer are discussed. Vapor pressures for fuel blends were also derived using equations of state such as UNIQUAC, NRTL and Peng-Robinson models. The weight changes and volume changes of fluoropolymers in ethanol-containing fuels were measured. Finally, the crystallinity index and glass transition temperature of fluoropolymers were also measured.
Diesel spray evaporation in a high pressure and high ambient temperature close to actual diesel engine condition was investigated in this study. A nano-spark shadowgraph photography technique and a rapid compression machine were applied in this experiment. By using this method, relatively clear image of liquid phase, vapor phase and droplets was obtained. In order to quantify the spray characteristics in the spray liquid area and vapor phase area, an image analysis method was applied. An algorithm was developed to quantify the droplets size and number of the droplets characteristic in the vapor phase. Experimental results have revealed that the injection pressure and the ambient temperature do not affect the spray penetration length apparently. In the case of ambient temperature Ti = 700K, the liquid core is observed in the region near the spray axis. Meanwhile, the vapor exists mostly in the outer region in the middle of the spray.
Effects of Low-Purge Vehicle Applications and Ethanol-Containing Fuels on Evaporative Emissions Canister Performance
The California Air Resources Board (CARB) LEV II regulations require less than 500 mg of vehicle evaporative emissions which, typically requires canister emissions of less than 200 mg. PZEV regulations require less than 350 mg vehicle emissions and zero emissions (< 54 mg) from the fuel system. Activated carbon canister emissions of less than 20 mg are typically required in order to meet PZEV regulations. LEV II canister emissions levels can typically be achieved through a combination of canister design, sufficient purge volumes, use of the appropriate activated carbon or combination of carbons, and in some cases an activated carbon honeycomb.