Tailpipe Exhaust Research Articles

The Policy Relevance of Wear Emissions from Road Transport, Now and in the Future—An International Workshop Report and Consensus Statement

Road transport emissions are a major contributor to ambient particulate matter concentrations and have been associated with adverse health effects. Therefore, these emissions are targeted through increasingly stringent European emission standards. These policies succeed in reducing exhaust emissions, but do not address “nonexhaust” emissions from brake wear, tire wear, road wear, and suspension in air of road dust. Is this a problem? To what extent do nonexhaust emissions contribute to ambient concentrations of PM10 or PM2.5? In the near future, wear emissions may dominate the remaining traffic-related PM10 emissions in Europe, mostly due to the steep decrease in PM exhaust emissions. This underlines the need to determine the relevance of the wear emissions as a contribution to the existing ambient PM concentrations, and the need to assess the health risks related to wear particles, which has not yet received much attention. During a workshop in 2011, available knowledge was reported and evaluated so as to draw conclusions on the relevance of traffic-related wear emissions for air quality policy development. On the basis of available evidence, which is briefly presented in this paper, it was concluded that nonexhaust emissions and in particular suspension in air of road dust are major contributors to exceedances at street locations of the PM10 air quality standards in various European cities. Furthermore, wear-related PM emissions that contain high concentrations of metals may (despite their limited contribution to the mass of nonexhaust emissions) cause significant health risks for the population, especially those living near intensely trafficked locations. To quantify the existing health risks, targeted research is required on wear emissions, their dispersion in urban areas, population exposure, and its effects on health. Such information will be crucial for environmental policymakers as an input for discussions on the need to develop control strategies. Implications: Road transport particulate matter (PM) emissions are associated with adverse health effects. Stringent policies succeed in reducing the exhaust PM emissions, but do not address “nonexhaust” emissions from brake wear, tire wear, road wear, and suspension in air of road dust. In the near future the nonexhaust emissions will dominate the road transport PM emissions. Based on the limited available evidence, it is argued that dedicated research is required on nonexhaust emissions and dispersion to urban areas from both an air quality and a public health perspective. The implicated message to regulators and policy makers is that road transport emissions continue to be an issue for health and air quality, despite the encouraging rapid decrease of tailpipe exhaust emissions. Supplemental Materials: Supplemental materials are available for this paper. Go to the publisher's online edition of the Journal of the Air & Waste Management Association.

Control of diesel engines using NOx-emission feedback

Variations of engine-out emissions due to ageing, component drift or production tolerances pose serious problems to meet legislative restrictions on exhaust tailpipe pollutant emissions. This paper addresses feedback of the raw emissions for improved control of diesel engines. A discussion of issues regarding the inclusion of raw-emission feedback into the engine control structure is provided, and a novel control structure for combined feedback control of the air-path variables boost pressure and exhaust gas recirculation rate and of the NOx emissions is presented. The proposed control structure basically consists of an optimal linear output feedback controller and a setpoint-adaption loop on the exhaust gas recirculation rate. With this approach, a simple control structure is available requiring a marginal calibration effort to meet desired NOx-emission values. Unfavourable injection timing in connection with NOx control is minimized by adapting the exhaust gas recirculation rate setpoint. The performance of the proposed approach is demonstrated by experimental results.

Three-Dimensional Simulation of Exhaust Particle Dispersion and Concentration Fields in the Near-Wake Region of the Studied Ground Vehicle

In the present study, the interaction effects of different vehicle speeds and exhaust tailpipe exit velocity and temperature conditions on the three-dimensional flow structure, exhaust particle dynamic behavior, formation and evolution processes (i.e., nucleation, coagulation, condensation, and dispersion), number and volume concentration, and nucleation rate fields in the near-wake region behind the studied ground vehicle in urban road microenvironment were comprehensively simulated using large-eddy simulation (LES) with the aerosol dynamics and dispersion model based on our recently established direct quadrature method of moments (DQMOM) approach. The numerical results show that the particles are drawn up into the recirculation region and then moved toward the upper vortex by its lower vortex accordingly. The particle nucleation rate is much more associated with the distribution of the root mean square (RMS) temperature than with that of the temperature itself. Some of the sulfuric acid concentration em...

Aerosol Behavior in the near Wake Region of the Vehicle

In the present study, the interaction effects of different vehicle speeds and vehicular exhaust tailpipe exit velocity conditions on the exhaust particle dynamic behaviors in the near-wake region behind the studied vehicle were numerically investigated. The results showed that the particles were drawn up into the recirculation region and then moved toward into the upper vortex by its lower vortex. A lower particle number concentration behind the studied vehicle is observed for a higher vehicle speed because of the rapidly increasing dilution ratio and the nucleation rate. The particle volume concentration is the highest in the recirculation region behind the studied vehicle and is diluted gradually beyond the recirculation region in the downstream.

Diesel engine dynamometer testing of impedancemetric NO x sensors

Prototype solid-state electrochemical sensors using a dense gold sensing electrode, porous yttria-stabilized zirconia (YSZ) electrolyte, and a platinum counter electrode (Au/YSZ/Pt) were evaluated for measuring NO x (NO and NO 2) in diesel exhaust. Both electrodes were exposed to the test gas (i.e., there was no reference gas for the counter electrode). An impedancemetric method was used for NO x measurements, where the phase angle was used as the response signal. A portion of the tailpipe exhaust from the dynamometer test stand was extracted and fed into a furnace containing the experimental sensor. The prototype sensor was tested along with a commercially available NO x sensor. Simultaneous measurements for NO x , O 2, CO 2, H 2O, CO, and CH 4 in a separate feed stream were made using Fourier transform infrared (FTIR) spectroscopy and an oxygen paramagnetic analyzer. The experimental sensor showed very good measurement capability for NO in the range of 25–250 ppm, with a response paralleling that of the FTIR and commercial sensor. The prototype sensor showed better sensitivity to NO x at the lower concentration ranges. O 2 is an interferent for the experimental sensor, resulting in decreased sensitivity for measurement of NO x . Methods to overcome this interference are discussed.

Particulate Emissions Hazards Associated with Fueling Heat Engines

All hydrocarbon- (HC-) fueled heat engine exhaust (tailpipe) emissions (<10 to 140 nm) contribute as health hazards, including emissions from transportation vehicles (e.g., aircraft) and other HC-fueled power systems. CO2emissions are tracked and, when mapped, show outlines of major transportation routes and cities. Particulate pollution affects living tissue and is found to be detrimental to cardiovascular and respiratory systems where ultrafine particulates directly translocate to promote vascular system diseases potentially detectable as organic vapors. This paper discusses aviation emissions, fueling, and certification issues, including heat engine emissions hazards, detection at low levels and tracking of emissions, and alternate energy sources for general aviation.

Direct quadrature method of moments for the exhaust particle formation and evolution in the wake of the studied ground vehicle

In the present study, the particle formation and evolution processes, and concentration field in the wake region of the studied ground vehicle for stationary (i.e., low idling mode) and moving (i.e., 10 and 30 km/h modes) conditions in a typical high densely urban road microenvironment were investigated numerically using large eddy simulation (LES) with the aerosol dynamics and dispersion model based on the direct quadrature method of moments (DQMOM) approach. The turbulent dilution and dispersion characteristics, and the complex formation and growth dynamics of exhaust particles behind the studied ground vehicle to the atmosphere were taken into consideration. The results show that the processes of nucleation and coagulation are completed in a short distance away from the vehicular exhaust tailpipe exit of the studied ground vehicle. Due to the nucleation, coagulation and strong dilution by the turbulent exhaust plume that take place behind the studied ground vehicle, the characteristics and behavior of the average diameter, and the number and volume concentration of the particles are quite different with respect to the studied driving conditions.

Life cycle emissions and energy study of biodiesel derived from waste cooking oil and diesel in Singapore

Biodiesel derived from Waste Cooking Oil (WCO) is considered highly environmentally sustainable since WCO is a waste product from domestic and commercial cooking processes and then recycled to a transportation fuel in Singapore. In addition, it avoids the conversion of land use for crop production. This is a strong advantage for Singapore which has relatively smaller land space than other countries. The import of virgin oil as feedstock into Singapore is also avoided. Therefore, the more appropriate feedstock to produce biodiesel in Singapore context is WCO. According to the National Environment Agency, diesel vehicles in Singapore contribute 50% of the total particulate matter smaller than 2.5 μm (PM0.25) emissions to air ambient. Hence, the aim of this life cycle assessment study was to compare the environmental performances of biodiesel derived from WCO and low sulphur diesel in terms of global warming potential, life cycle energy efficiency (LCEE) and fossil energy ratio (FER) using the life cycle inventory. The results of this study would serve as a reference for energy policy makers and environmental agencies. ISO14040 and ISO14044 (ISO14040 2006; ISO 14044 2006) are used as the method for implementing this study. This comparative study between biodiesel derived from WCO and low sulphur diesel is done by comparing the life cycle inventory results. The tailpipe emission tests were done using a gas analyser. Biodiesel production data are collected from a local facility. The production of main ingredients, types of transportation, conversion of WCO to biodiesel and the usage of biodiesel were considered within the dataset. Production of low sulphur diesel was modelled according to several references. The phases include foreign crude oil production, refining, transporting of diesel to station and finally the usage of diesel. The testing vehicle for both transportation fuels is an ISUZU pickup truck with engine capacity of 3,059 cc and in direct injection combustion chamber type. The functional unit in this study is output of 1 transportation-km. In this section, two types of emissions are discussed. First is the net life cycle emission. The second is the exhaust tailpipe emissions. Highest amount of reduction on a life cycle basis is PM2.5 and PM10 with a significant reduction of 99.99%. On the exhaust tailpipe emission basis, the reduction for total particulate matter is 94.80%. The LCEE of biodiesel produced from WCO is calculated as 86.93%. This is higher than biodiesel reported from US studies (using soybean as feedstock) which is 80.55%. The low LCEE value of 71.09% for low sulphur diesel could be attributed by the fact that Singapore depends greatly on foreign crude oil production and imports. The FER is calculated to be 9.39. The life cycle of biodiesel produced from the recycling of WCO produces more than nine times as much energy in its final fuel product as it uses in fossil energy. This is three times higher than biodiesel derived from soya oil in the USA. The emission results and the life cycle energy efficiencies have indicated that the replacement of low sulphur diesel with biodiesel derived from WCO as a transportation fuel is favourable. In Singapore, the potential substitution percentage of diesel by biodiesel if all of the WCO can be collected and processed to biodiesel is 1.42%. There is a need for recyclers to convince the food establishments and users of cooking oil of the benefits of recycling cooking oil, which in turn obtains a steady source of WCO as feedstock for biodiesel production. In addition, as the biodiesel life cycle defined is very much dependent on WCO as a feedstock, it is recommended to optimise the WCO collection network.

Diurnal and Seasonal Variability of Gasoline-Related Volatile Organic Compound Emissions in Riverside, California

On- and off-road mobile sources are the dominant contributors to urban anthropogenic volatile organic compound (AVOC) emissions. Analyses of gasoline samples from California for both summer and winter indicate significant differences in liquid fuel and vapor chemical composition due to intentional seasonal adjustments. Ambient concentrations of 55 VOCs were measured via in situ gas chromatography in the 2005 Study of Organic Aerosols at Riverside (SOAR) during both summer and fall. A chemical mass balance analysis was used to differentiate vapor pressure-driven VOC emissions from other motor vehicle-related emissions such as tailpipe exhaust. Overall, fuel vapor emissions accounted for 31 +/- 2% of gasoline-related VOC in Riverside; California's emission factor model similarly estimates 31% of gasoline-related VOC emissions are fuel vapor. The diurnal pattern of vapor pressure-driven VOC source contributions is relatively stable around 10 microg/m3, while whole gasoline (i.e., tailpipe) contributions peak at approximately 60 microg/m3 during the morning commute. There is no peak in whole gasoline source contributions during the afternoon, due to rapid dilution associated with high mixing heights and wind speeds in the Riverside area. The relationship between estimated gasoline-related VOC and observed carbon monoxide concentrations in this study is similar to California's 2005 emission inventory; we calculated a VOC to CO mass ratio of 0.086 +/- 0.006 (95% CI) compared to 0.097 in the emission inventory for all gasoline-related sources.

Study on the Operating Process of an Underwater Diesel Engine

A steady state and transient simulation model for an underwater diesel engine system, including governor, diesel engine, and pipe systems after turbine, is developed and verified. A two-phase flow of exhaust gas and water at the tail pipe is studied with three-dimensional fluid dynamics calculation. A water flooding criterion for an underwater engine is also given by these models and related experiments. Safe operation ranges of the engine are also studied. The histories of relative engine speed, pressure, and Froude number of the tail pipe exhaust gas under starting and stopping processes are studied. The Froude number of the tail pipe exhaust gas is an oscillating phenomena when the engine is starting, which is likely to cause sea water to flow backward into the tail pipe. The opening of the tongue valve must be controlled according to engine back pressure during the stopping process to prevent sea water flooding on the one hand and high back pressure on the other. The underwater diesel engine operating control strategy can be given on the basis of the research work.

Effect of rear slant angle on flow structures, and pollutant dispersion and concentration fields in the wake of the studied model vehicle

Experimental investigations of the interaction effect of rear slant angle (i.e., α = 25° and 60°) and heated air exhaust jet condition (i.e., U j and T j ) on flow structures, and pollutant (i.e., scalar) dispersion and concentration fields in the near-wake region of two simplified scale-model vehicles at Reynolds number Re h = 5.8 × 10 4 were performed in a closed-circuit wind tunnel using laser Doppler anemometry (LDA) and the cold wire thermometry. The results show that the behaviors of flow structures and pollutant dispersion in the near-wake region of the studied model vehicles are highly dependent on the interaction effect of U j / U ∞ and α. For the low value of U j / U ∞ (i.e., the driving mode from 30 km h −1 to 70 km h −1), the wake structure of the two studied model vehicles is almost similar to the case without introducing the vehicular exhaust jet flow, U j / U ∞ = 0, but the scalar concentration is neither sent straight to the wake region nor trapped by the recirculation zone. For higher value of U j / U ∞ (i.e., the driving mode of 10 km h −1), the jet flow perturbation along the central plane of the vehicular exhaust tailpipe causes the disappearance of the lower vortex in the recirculation zone for the studied model vehicle A ( α = 25°) while it causes the stretching of the recirculation zone for the studied model vehicle B ( α = 60°). The contaminant is mainly straight trajectory along its jet exhaust flow axis. Outside the recirculation zone, the flow field becomes symmetrical and its flow structure depends only on the rear slant angle of the studied model vehicle. The scalar concentration field of the studied model vehicle B is characterized by a two-dimensional flow structure whatever the studied driving modes are. The distribution of the mean normalized temperature excess field (i.e., scalar concentration field) conforms to the velocity vector field for both studied model vehicles. For the studied model vehicle A, the scalar concentration is drawn to the edge of the trailing vortex at the vehicular exhaust jet side. This phenomenon causes a significant reduction of the scalar concentration level whatever the studied driving modes are.

Influence of Pre Turbo Catalyst Design on Diesel Engine Performance, Emissions and Fuel Economy

Influence of Pre Turbo Catalyst Design on Diesel Engine Performance, Emissions and Fuel Economy

Real-Time Estimation of Elemental Carbon Emitted from a Diesel Engine

New Mining Safety and Health Administration (MSHA) regulations limit the mass concentration of airborne diesel particulate matter (DPM) or, more specifically, the concentration of elemental carbon (EC), in underground mines. The mine operators are responding by introducing a variety of controls to reduce DPM in the mines, potentially including the evaluation of new maintenance procedures to reduce underground mine vehicle emissions. There is currently a lack of an inexpensive and dependable method to directly measure the DPM concentration emitted from the vehicle tailpipe. To that end, this work demonstrated a simple field portable method for estimating the mass concentration of elemental carbon exiting the tailpipe of a diesel engine using a direct reading photometer. Simultaneous measurements of tailpipe exhaust were made with a Thermo Electron Personal DataRAM 1200 photometer (particulate mass concentration based on light scattering) and by analyzing PM2.5 and PM1.0 samples collected on quartz fiber filters using the National Institute of Occupational Safety and Health (NIOSH) method 5040 (mass concentration of EC via thermal-optical method). Results indicate surprisingly good correlation (R2 = 0.97) of the two methods when the data are adjusted for relative humidity (RH) and corrected using an empirically generated calibration factor. Although preliminary, it may be possible to implement this method in maintenance shops to monitor emission trends and to compare emissions of various vehicles in a fleet. Such data will be useful for fleet planning to meet new air quality standards.

Assessment of vehicular and non-vehicular contributions to hydrocarbons using exclusive vehicular indicators

This study investigates suitable non-methane hydrocarbon (NMHC) species to be used as motor vehicle indicators, and examines their possible applications and limitations. Suitable indicators are employed to assess vehicular and non-vehicular contributions of individual NMHCs in a given environment. The concept involves using concentration ratios of individual NMHCs to the indicators characteristic of vehicular emissions to reveal the excess concentration contributed by non-vehicular sources. By comparing the correlation between NMHCs and methyl tert-butyl ether (MTBE), a proven good motor vehicle indicator, in metropolitan Kaohsiung, Taiwan known for its heavy traffic and variety of heavy industries, it was found that 2,2-dimethylbutane (22DMC4A), 3-methylpentane (3MC5A), methylcyclopentane (McC5A), 2-methylhexane (2MC6A) and 3-methylhexane (3MC6A) revealed good concentration correlation with MTBE. The result implies these species in Kaohsiung have the same source as MTBE originated primarily from motor vehicle sources consisting of tailpipe exhaust and gasoline evaporation. 22DMC4A, 3MC5A, McC5A, 2MC6A and 3MC6A are common components in nearly all gasoline evaporation and tailpipe exhaust world-wide, and more exclusive to motor vehicle emissions. Moreover, they can be easily analyzed by the popular gas chromatography/flame ionization detection (GC/FID) and, thus can be the potential indicators to be applied generally in many regions of the world. Possible chemical and physical removals affecting the NMHCs/indicator ratios in the atmosphere are discussed. The ethylbenzene/ m,p-xylene ratios could be used as an effective indicator of photochemical removal degree to test and sift out the data affected by excessive photochemical reaction to enhance the accuracy of NMHC source apportionment.

Development of a Heavy-Duty Engine Test Cycle Representative of On-Highway Not-To-Exceed Operation

This paper describes the development of an engine test cycle that is representative of the real-world heavy-duty engine activity in the not-to-exceed (NTE) zone of operation. The test cycle is intended to provide an in-laboratory verification capability to determine if an engine exceeds the in-use emissions standards. By simulating the real-world driving pattern of the vehicle the test cycles provide the most realistic estimation of emission levels in the NTE zone of operation. It is well recognized that traditional laboratory test cycles do not provide an accurate representation of a vehicle's operation on the road under present-day driving conditions. This cycle was developed by collecting and analysing engine activity data and statistical information on heavy-duty vehicle use for different applications under real-world conditions. A test vehicle instrumented with the West Virginia University mobile emissions measurement system (MEMS), a portable on-board tailpipe exhaust emissions measurement system, was used to obtain engine operating conditions, vehicle speed, and in-use brake-specific emissions of CO2 and NO x. The vehicle was tested on specific routes, which included a mix of highway and city driving patterns. The speed and torque points were normalized according to procedures described in the Code of Federal Regulations (CFR) Title 40, Part 1065. A representative transient cycle that was developed has been used to conduct emissions tests on heavy-duty diesel engines, and serves to characterize NO x emissions during the NTE operation. This characterization will aid in-laboratory testing and provide a better understanding of the emissions behaviour during on-road NTE operation, electronic control module calibrations, and engine development. The results indicate that the on-highway NTE cycle called the ‘WVU NTE cycle’ produced emissions results that were within ±1 per cent of those produced during an on-road test.

An investigation into the passive acoustic effect of the turbine in an automotive turbocharger

The turbine of an automotive turbocharger is one of many elements in the exhaust line which lie between the primary noise source, namely the gas pulsations through the exhaust valves, and the primary noise radiation element, the exhaust tailpipe orifice. Like every other element of the exhaust system, it has a passive acoustic effect on the propagation of the primary exhaust noise. Thus knowledge of the passive acoustic effect of the turbine is essential to an understanding of the overall acoustic effectiveness of an exhaust system. In particular, if a comprehensive model of the acoustic propagation through the entire exhaust system of a turbocharged engine is sought, an acoustic model of the turbine is a prerequisite. This paper presents such a model as well as an experimental technique from which measured data can be obtained to verify the model and to characterise the acoustic behaviour of the turbine in a more general sense. In the first instance, the one-dimensional nonlinear equations of the fluid flow are solved for steady flow, to determine the background conditions for acoustic propagation including the mean convective flow distribution. The nonlinear time-domain flow equations are then linearised and solved for a single frequency of sound. At low frequencies, there is good agreement between measured and predicted results. System resonances that are observed at high frequencies can also be explained by the model.

Automated design of exhaust systems

For some years, a significant proportion of the functional development of exhaust systems has been carried out by means of simulation programs. Nonetheless, the development process does not differ markedly from the traditional approach involving trial and error. Efficiency can only be further increased by combining the known mathematical simulation methods with modern optimisation processes. This paper presents the development methodology used at Eberspacher to optimise exhaust tailpipe noise and exhaust emission control. The capabilities and reliability of this optimisation program are illustrated by means of examples.

Traffic-generated emissions of ultrafine particles from pavement–tire interface

In a road simulator study, a significant source of sub-micrometer fine particles produced by the road–tire interface was observed. Since the particle size distribution and source strength is dependent on the type of tire used, it is likely that these particles largely originate from the tires, and not the road pavement. The particles consisted most likely of mineral oils from the softening filler and fragments of the carbon-reinforcing filler material (soot agglomerates). This identification was based on transmission electron microscopy studies of collected ultrafine wear particles and on-line thermal treatment using a thermodesorber. The mean particle number diameters were between 15–50 nm, similar to those found in light duty vehicle (LDV) tail-pipe exhaust. A simple box model approach was used to estimate emission factors in the size interval 15–700 nm. The emission factors increased with increasing vehicle speed, and varied between 3.7×10 11 and 3.2×10 12 particles vehicle −1 km −1 at speeds of 50 and 70 km h −1. This corresponds to between 0.1–1% of tail-pipe emissions in real-world emission studies at similar speeds from a fleet of LDV with 95% gasoline and 5% diesel-fueled cars. The emission factors for particles originating from the road–tire interface were, however, similar in magnitude to particle number emission factors from liquefied petroleum gas-powered vehicles derived in test bench studies in Australia 2005. Thus the road–tire interface may be a significant contributor to particle emissions from ultraclean vehicles.

엔진 배기단 적용을 위한 Time Resolved Laser Induced Icandescence (TIRE-LII) 신호의 보정 : 카본 입자 이용

엔진 배기단 적용을 위한 Time Resolved Laser Induced Icandescence (TIRE-LII) 신호의 보정 : 카본 입자 이용

Estimation of petrol and diesel adulteration with kerosene and assessment of usefulness of selected automobile fuel quality test parameters

Kerosene is common adulterant utilized for mixing with diesel. Five fuel-adulterant mixtures in different proportions by volume were prepared and individually tested for density and kinematic viscosity. The mixtures were administered to six light cargo vehicles and the tail pipe exhaust emission was tested for opacity value. No appreciable density variation at different levels of adulteration was observed. Density was within the prescribed value even at higher adulteration. Considerable decrease in kinematic viscosity, a departure from prescribed viscosity, was noted at higher adulteration level. The percent opacity value decreased sharply even at small level of adulteration. The probable amount of kerosene present as an adulterant in diesel dispensed at filling stations in Kathmandu city ranged between 35% and 50%. The observations suggest density test is not a good indicator of diesel adulteration. Kinematic viscosity and opacity value are useful diesel adulteration test parameters. Existing diesel adulteration warrants initiation of strict compliance regulation.