Hybridization offers great potential for decreasing pollutant and carbon dioxide emissions of die... more Hybridization offers great potential for decreasing pollutant and carbon dioxide emissions of diesel cars. However, an assessment of the real-world emissions performance of modern diesel hybrids is missing. Here, we test three diesel-hybrid cars on the road and benchmark our findings with two cars against tests on the chassis dynamometer and model simulations. The pollutant emissions of the two cars tested on the chassis dynamometer were in compliance with the relevant Euro standards over the New European Driving Cycle and Worldwide harmonized Light vehicles Test Procedure. On the road, all three diesel-hybrids exceeded the regulatory NOx limits (average exceedance for all trips: +150% for the Volvo, +510% for the Peugeot, and +550% for the Mercedes-Benz) and also showed elevated on-road CO2 emissions (average exceedance of certification values: +178, +77, and +52%, respectively). These findings point to a wide discrepancy between certified and on-road CO2 and suggest that hybridiza...
Since the introduction of first generation biodiesel (Fatty Acid Methyl Esters, FAME) at blending... more Since the introduction of first generation biodiesel (Fatty Acid Methyl Esters, FAME) at blending rates in diesel of up to 7% vol., concerns were raised regarding engine component durability. The deposition rate on engine components appears to be related to specific biodiesel characteristics, not included in the EN14214 standard. This paper describes a test method developed that is able to predict the effects of specific fuels on engine components that are not possible to be revealed by initial fuel properties as tested according to fuel standards EN590 and EN14214. The method is able to simulate long engine operation within a feasible test duration with controllable acceleration of involved phenomena and in a cost effective manner including the use of limited amount of fuel and only engine components affected by the fuel degradation. The paper presents the developed method, the experimental setup configuration, fuel treatment, key operating conditions and operating protocol of the main test. Test results are being presented for both current market fuels of different characteristics as regards FAME content and presence of detergent additives as well as for experimental and reference fuel blends developed for the assessment of possible future fuels and fuel injection system configurations. The paper concludes that the specific method is able to provide information on the applicability and possible durability issues associated with the use of alternative fuels and advanced fuel injection system technologies under consideration and is a candidate to be implemented as a future fuel standard.
This is undoubtedly the largest and best October Peach yet produced. The parent tree was found gr... more This is undoubtedly the largest and best October Peach yet produced. The parent tree was found growing in an old orchard in this Parish and is believed to be 25 or 30 years old, and is yet bearing very fine Fruit. Description-Large and round with suture; a beautiful yellow, cling, very tender and juicy, and in flavor unstirpassed ; a fine shipper and extra for canning. The following certificates speak for themselves :
Airborne urban particulate and gaseous pollutants measurements were conducted at the kerbside of ... more Airborne urban particulate and gaseous pollutants measurements were conducted at the kerbside of a busy road and at a nearby urban background site of Thessaloniki, Greece, during a winter and a summer period. The main objective was to observe how the financial crisis has affected the air quality in the city, compared to previous measurements. Compared to a study conducted in 2006, the current work suggests that although average concentrations at the traffic affected site remain higher that in the urban background station, the differences are much smaller than in the past. A number of observations suggest a scenario of decrease in traffic activity and increase in biomass burning for residential heating. On this basis, the results suggest that traffic may be less important as an air quality contributor in a financially hit city. On the contrary, domestic heating appears as a significant contributor and affects areas of the city that were earlier not being of environmental concern. Because of the impact of biomass burning in residential areas, exposure calculations are required to estimate whether traffic or biomass burning is the overall highest contributors to daily PM dosages that citizens of the city are exposed to.
We present an overview of the modelling of particle number concentrations (PNC's) in five maj... more We present an overview of the modelling of particle number concentrations (PNC's) in five major European cities, namely Helsinki, Oslo, London, Rotterdam and Athens, in 2008. Novel emission inventories of particle numbers have been compiled both on urban and European scales. We use atmospheric dispersion modelling for PNC's in the five target cities and on a European scale, and evaluate the predicted results against available measured concentrations. The concentrations of PN in the selected cities were mostly influenced by the emissions originated from local vehicular traffic; however, in some of the cities, also harbour and airport activities were significant. The highest values of the predicted PNC's were higher in the megacities, London and Athens, and also in Rotterdam, whereas these were lower in Helsinki and Oslo. It was numerically evaluated that the influence of coagulation and dry deposition on the predicted PNC's was substantial for urban background in Oslo...
ABSTRACT This paper reviews the state of liquid biofuels in Greece and presents the current situa... more ABSTRACT This paper reviews the state of liquid biofuels in Greece and presents the current situation in production and research. The first part presents the production potential in terms of cultivated crops along with the industrial activity on biofuels and their distribution in the country. In the second part, the research activities are discussed. It is shown that the Greek biofuel potential is significant, although some problems in the allocation of the fuel resulted in severe constraints to efficiency. Research on the optimization of biodiesel properties and on the development of 2nd generation biofuels as well on the assessment of their impacts on engine performance and emissions is remarkable and promising.
Journal of the Air and Waste Management Association, 2009
To improve the accuracy, reliability, and representativeness of emission factors, 10 European lab... more To improve the accuracy, reliability, and representativeness of emission factors, 10 European laboratories worked together to study the influence of 20 parameters on the measurement of light-vehicle emission factors on chassis dynamometer of 4 main categories: driving patterns, vehiclerelated parameters, vehicle sampling, and laboratory-related parameters. The results are based on (1) literature synthesis, (2) approximately 2700 specific tests with 183 vehicles, and (3) the reprocessing of more than 900 tests. These tests concern the regulated atmospheric pollutants and pre-Euro to Euro 4 vehicles. Of the 20 parameters analyzed, 7 seemed to have no effect, 7 were qualitatively influential, and 6 were highly influential (gearshift strategy, vehicle mileage, ambient temperature, humidity, dilution ratio, and driving cycle). The first four of the six were able to have correction factors developed for them. The results IMPLICATIONS The accuracy of most air pollution modeling and the efficiency of emission standard reinforcement depend on the accuracy of emission factor measurements. The understanding of the role of various emission parameters allows for the improvement of the standard emission measurement method and the quality of the emission calculations at the local, regional, or national levels.
PM emission reductions brought by more stringent emission standards and associated technologies m... more PM emission reductions brought by more stringent emission standards and associated technologies may not lead to equivalent (eco-)toxicity reductions.
A modelling approach which applies fundamental mechanisms of aerosol formation and dynamics to si... more A modelling approach which applies fundamental mechanisms of aerosol formation and dynamics to simulate the effect of sampling conditions on exhaust particle distributions is presented. The model examines the evolution of exhaust aerosol immediately after its mixing with dilution air, which is assumed to occur adiabatically and instantaneously. Particle number and mass balances are expressed separately for two aerosol modes: the nucleation mode (mean diameter o30 nm) and the accumulation mode (430 nm). The number and mass balances include homogeneous nucleation, condensation on existing particles, intra-and inter-mode coagulation and diffusional losses to the walls. The model takes into account the sulphuric acid-water system and a heavy (C 16) hydrocarbon in diesel exhaust. First, it is shown that the number concentration of the nucleation mode can be described if a barrierless nucleation is assumed for the sulphuric acid. At a second step, it is computationally demonstrated that the measured volume concentration in the nucleation mode can only be reached, if hydrocarbon condensation occurs on the sulphuric acid-water nuclei. Finally, it is shown that the nucleation mode is significantly suppressed by the presence of soot mode, due to the high surface area of the latter, which consumes volatile species. The model may be used to estimate the effect of sampling conditions on exhaust particle size distributions, with emphasis on the nucleation mode profiles.
Transport activities contribute significantly to air pollutant emissions in Europe and the impact... more Transport activities contribute significantly to air pollutant emissions in Europe and the impact on emissions is a key element in the evaluation of any transport policy or plan. Calculation of emissions has therefore gained institutional importance in the European Community, particularly with the development of the CAFÉ (EC, 2005a) and ECCP (EC, 2005b) programmes. Reliable and credible emission estimates are a central prerequisite, but comparisons of the results from emission models such as COPERT (Ntziachristos & ...
The demand for fossil fuel in the transport sector is constantly increasing and transportation is... more The demand for fossil fuel in the transport sector is constantly increasing and transportation is ranked amongst the highest greenhouse emitting sectors globally. Today, tackling CO 2 emissions from road transport a widely discussed topic and constitutes a milestone towards reaching a sustainable, carbon neutral economy. This challenge is being described in various initiatives adopted in the European Union and other parts of the world. So far several measures have been proposed and adopted for reversing the increasing greenhouse gas emissions trends. This paper attempts an overview of the existing policy framework in various countries focusing on European Union. In addition, the main technical measures proposed and promoted in this direction are presented and evaluated with respect to their greenhouse reduction potential. Special attention is paid to emerging technologies, such as hybrid vehicles and biofuels. The main factors differentiating the officially reported CO 2 emissions f...
To meet the upcoming CO2 reduction challenges, the further electrification of vehicle powertrains... more To meet the upcoming CO2 reduction challenges, the further electrification of vehicle powertrains is indispensable. In combination with the post-Euro 6 requirements for criteria pollutants, the exhaust system is expected to be more complex to allow for extremely low emissions under all driving conditions, potentially involving technologies such as electrical heating and phase-change materials. The longer ‘zero-flow’ operation of the exhaust system in hybrid applications and the associated light-out risk have demanding accuracy requirements for heat loss calculations and require additional thermal management strategies. This paper discusses the additional challenges posed with regard to catalyst modeling in the boundary conditions of electrified vehicles and the necessary improvements that go beyond the state-of-the-art techniques. Most of the necessary improvements are linked to advanced 3D modeling of the exhaust system components accounting for free convection and radiative heat t...
The paper presents the results of the effect of various fuel economy technologies on the certifie... more The paper presents the results of the effect of various fuel economy technologies on the certified CO2 emissions of light duty vehicles. The vehicles operate under two different driving cycles, namely the New European Driving Cycle (NEDC) and the Worldwide harmonized Light duty Test Procedure (WLTP), which is considered closer to real world driving and is going to be the new type approval test in the near future. The study focuses on the comparative evaluation of the effect of each technology on CO2 emissions under these two driving cycles. To this aim, simulation models for a number of passenger cars were developed and validated against test data, generated via a specifically developed test protocol. In order to cover a large share of the market, the European fleet was divided into a number of segments based on specific vehicle characteristics and technologies, and representative vehicles for each segment were chosen. In order to minimize flexibilities and sources of uncertainty, the models were developed according to a standardized modelling procedure, based on the development of a reference "template model". AVL's Cruise was used as simulation platform. The various components and modules for each vehicle model, as well as the respective input parameters, were defined with the support of the respective OEMs. After gaining confidence in the simulation models for all the vehicles considered in the present work, additional technologies, such as start-stop, brake energy recuperation and different drivetrain configurations, were implemented in each model. Specific strategies have been defined for the implementation of individual technologies and, where needed, additional algorithms were developed in Cruise. The results show that the effect of each technology on CO2 emissions is different between NEDC and WLTP, owing to the different characteristics of each cycle. For example, the effect of start-stop on CO2 emissions is larger in NEDC, due to longer idling periods compared to
ABSTRACT The successful design and especially the control of the SCR system is a challenging proc... more ABSTRACT The successful design and especially the control of the SCR system is a challenging process that can be supported by the application of simulation tools. As a first step, we employ physico-chemically informed ‘off-line’ models that are calibrated with the help of targeted small- and full-scale tests. Despite their high level of sophistication, this SCR model is able to be integrated in a control-oriented simulation software platform and connected to other powertrain simulation blocks. The target is to use this simulation platform as a virtual environment for the development and optimization of SCR control strategies. The above process is demonstrated in the case of a passenger car SCR. The model is calibrated at both fresh and aged catalyst condition and validated using experimental data from the engine bench under a wide variety of operating conditions. Next, the calibrated model was coupled with embedded control models, developed for Euro 6 passenger car powertrains. The final simulation platform enabled the precalibration and optimization of dosing control strategies, saving significant experimental effort and costs. Finally, it allowed the realization of the sensitivity analysis of the embedded control strategies, a procedure which guaranties the controlled system's robustness to engine dispersion and drift.
In the first part of this study, an improved model for the calculation of pressure drop in partic... more In the first part of this study, an improved model for the calculation of pressure drop in particulate filters was presented with special emphasis on the soot permeability properties and its dependence on temperature and pressure. With the assumption of uniform wall flow distribution throughout the channel length, it was also possible to derive an analytical expression that was validated against experimental data on an engine bench. Using the results of pressure drop modelling, it is possible to carry out ‘inverse’ calculations of the soot mass in the filter based on the measurements of flowrate, temperature and backpressure, which forms the main subject of the present work. This approach is tested successfully against experimental data in filters of different geometry and material, yielding promising results. Such computations may be very helpful for the interpretation of experimental results in engine testing. In this paper, typical applications in the field of reaction rate asses...
Hybridization offers great potential for decreasing pollutant and carbon dioxide emissions of die... more Hybridization offers great potential for decreasing pollutant and carbon dioxide emissions of diesel cars. However, an assessment of the real-world emissions performance of modern diesel hybrids is missing. Here, we test three diesel-hybrid cars on the road and benchmark our findings with two cars against tests on the chassis dynamometer and model simulations. The pollutant emissions of the two cars tested on the chassis dynamometer were in compliance with the relevant Euro standards over the New European Driving Cycle and Worldwide harmonized Light vehicles Test Procedure. On the road, all three diesel-hybrids exceeded the regulatory NOx limits (average exceedance for all trips: +150% for the Volvo, +510% for the Peugeot, and +550% for the Mercedes-Benz) and also showed elevated on-road CO2 emissions (average exceedance of certification values: +178, +77, and +52%, respectively). These findings point to a wide discrepancy between certified and on-road CO2 and suggest that hybridiza...
Since the introduction of first generation biodiesel (Fatty Acid Methyl Esters, FAME) at blending... more Since the introduction of first generation biodiesel (Fatty Acid Methyl Esters, FAME) at blending rates in diesel of up to 7% vol., concerns were raised regarding engine component durability. The deposition rate on engine components appears to be related to specific biodiesel characteristics, not included in the EN14214 standard. This paper describes a test method developed that is able to predict the effects of specific fuels on engine components that are not possible to be revealed by initial fuel properties as tested according to fuel standards EN590 and EN14214. The method is able to simulate long engine operation within a feasible test duration with controllable acceleration of involved phenomena and in a cost effective manner including the use of limited amount of fuel and only engine components affected by the fuel degradation. The paper presents the developed method, the experimental setup configuration, fuel treatment, key operating conditions and operating protocol of the main test. Test results are being presented for both current market fuels of different characteristics as regards FAME content and presence of detergent additives as well as for experimental and reference fuel blends developed for the assessment of possible future fuels and fuel injection system configurations. The paper concludes that the specific method is able to provide information on the applicability and possible durability issues associated with the use of alternative fuels and advanced fuel injection system technologies under consideration and is a candidate to be implemented as a future fuel standard.
This is undoubtedly the largest and best October Peach yet produced. The parent tree was found gr... more This is undoubtedly the largest and best October Peach yet produced. The parent tree was found growing in an old orchard in this Parish and is believed to be 25 or 30 years old, and is yet bearing very fine Fruit. Description-Large and round with suture; a beautiful yellow, cling, very tender and juicy, and in flavor unstirpassed ; a fine shipper and extra for canning. The following certificates speak for themselves :
Airborne urban particulate and gaseous pollutants measurements were conducted at the kerbside of ... more Airborne urban particulate and gaseous pollutants measurements were conducted at the kerbside of a busy road and at a nearby urban background site of Thessaloniki, Greece, during a winter and a summer period. The main objective was to observe how the financial crisis has affected the air quality in the city, compared to previous measurements. Compared to a study conducted in 2006, the current work suggests that although average concentrations at the traffic affected site remain higher that in the urban background station, the differences are much smaller than in the past. A number of observations suggest a scenario of decrease in traffic activity and increase in biomass burning for residential heating. On this basis, the results suggest that traffic may be less important as an air quality contributor in a financially hit city. On the contrary, domestic heating appears as a significant contributor and affects areas of the city that were earlier not being of environmental concern. Because of the impact of biomass burning in residential areas, exposure calculations are required to estimate whether traffic or biomass burning is the overall highest contributors to daily PM dosages that citizens of the city are exposed to.
We present an overview of the modelling of particle number concentrations (PNC's) in five maj... more We present an overview of the modelling of particle number concentrations (PNC's) in five major European cities, namely Helsinki, Oslo, London, Rotterdam and Athens, in 2008. Novel emission inventories of particle numbers have been compiled both on urban and European scales. We use atmospheric dispersion modelling for PNC's in the five target cities and on a European scale, and evaluate the predicted results against available measured concentrations. The concentrations of PN in the selected cities were mostly influenced by the emissions originated from local vehicular traffic; however, in some of the cities, also harbour and airport activities were significant. The highest values of the predicted PNC's were higher in the megacities, London and Athens, and also in Rotterdam, whereas these were lower in Helsinki and Oslo. It was numerically evaluated that the influence of coagulation and dry deposition on the predicted PNC's was substantial for urban background in Oslo...
ABSTRACT This paper reviews the state of liquid biofuels in Greece and presents the current situa... more ABSTRACT This paper reviews the state of liquid biofuels in Greece and presents the current situation in production and research. The first part presents the production potential in terms of cultivated crops along with the industrial activity on biofuels and their distribution in the country. In the second part, the research activities are discussed. It is shown that the Greek biofuel potential is significant, although some problems in the allocation of the fuel resulted in severe constraints to efficiency. Research on the optimization of biodiesel properties and on the development of 2nd generation biofuels as well on the assessment of their impacts on engine performance and emissions is remarkable and promising.
Journal of the Air and Waste Management Association, 2009
To improve the accuracy, reliability, and representativeness of emission factors, 10 European lab... more To improve the accuracy, reliability, and representativeness of emission factors, 10 European laboratories worked together to study the influence of 20 parameters on the measurement of light-vehicle emission factors on chassis dynamometer of 4 main categories: driving patterns, vehiclerelated parameters, vehicle sampling, and laboratory-related parameters. The results are based on (1) literature synthesis, (2) approximately 2700 specific tests with 183 vehicles, and (3) the reprocessing of more than 900 tests. These tests concern the regulated atmospheric pollutants and pre-Euro to Euro 4 vehicles. Of the 20 parameters analyzed, 7 seemed to have no effect, 7 were qualitatively influential, and 6 were highly influential (gearshift strategy, vehicle mileage, ambient temperature, humidity, dilution ratio, and driving cycle). The first four of the six were able to have correction factors developed for them. The results IMPLICATIONS The accuracy of most air pollution modeling and the efficiency of emission standard reinforcement depend on the accuracy of emission factor measurements. The understanding of the role of various emission parameters allows for the improvement of the standard emission measurement method and the quality of the emission calculations at the local, regional, or national levels.
PM emission reductions brought by more stringent emission standards and associated technologies m... more PM emission reductions brought by more stringent emission standards and associated technologies may not lead to equivalent (eco-)toxicity reductions.
A modelling approach which applies fundamental mechanisms of aerosol formation and dynamics to si... more A modelling approach which applies fundamental mechanisms of aerosol formation and dynamics to simulate the effect of sampling conditions on exhaust particle distributions is presented. The model examines the evolution of exhaust aerosol immediately after its mixing with dilution air, which is assumed to occur adiabatically and instantaneously. Particle number and mass balances are expressed separately for two aerosol modes: the nucleation mode (mean diameter o30 nm) and the accumulation mode (430 nm). The number and mass balances include homogeneous nucleation, condensation on existing particles, intra-and inter-mode coagulation and diffusional losses to the walls. The model takes into account the sulphuric acid-water system and a heavy (C 16) hydrocarbon in diesel exhaust. First, it is shown that the number concentration of the nucleation mode can be described if a barrierless nucleation is assumed for the sulphuric acid. At a second step, it is computationally demonstrated that the measured volume concentration in the nucleation mode can only be reached, if hydrocarbon condensation occurs on the sulphuric acid-water nuclei. Finally, it is shown that the nucleation mode is significantly suppressed by the presence of soot mode, due to the high surface area of the latter, which consumes volatile species. The model may be used to estimate the effect of sampling conditions on exhaust particle size distributions, with emphasis on the nucleation mode profiles.
Transport activities contribute significantly to air pollutant emissions in Europe and the impact... more Transport activities contribute significantly to air pollutant emissions in Europe and the impact on emissions is a key element in the evaluation of any transport policy or plan. Calculation of emissions has therefore gained institutional importance in the European Community, particularly with the development of the CAFÉ (EC, 2005a) and ECCP (EC, 2005b) programmes. Reliable and credible emission estimates are a central prerequisite, but comparisons of the results from emission models such as COPERT (Ntziachristos & ...
The demand for fossil fuel in the transport sector is constantly increasing and transportation is... more The demand for fossil fuel in the transport sector is constantly increasing and transportation is ranked amongst the highest greenhouse emitting sectors globally. Today, tackling CO 2 emissions from road transport a widely discussed topic and constitutes a milestone towards reaching a sustainable, carbon neutral economy. This challenge is being described in various initiatives adopted in the European Union and other parts of the world. So far several measures have been proposed and adopted for reversing the increasing greenhouse gas emissions trends. This paper attempts an overview of the existing policy framework in various countries focusing on European Union. In addition, the main technical measures proposed and promoted in this direction are presented and evaluated with respect to their greenhouse reduction potential. Special attention is paid to emerging technologies, such as hybrid vehicles and biofuels. The main factors differentiating the officially reported CO 2 emissions f...
To meet the upcoming CO2 reduction challenges, the further electrification of vehicle powertrains... more To meet the upcoming CO2 reduction challenges, the further electrification of vehicle powertrains is indispensable. In combination with the post-Euro 6 requirements for criteria pollutants, the exhaust system is expected to be more complex to allow for extremely low emissions under all driving conditions, potentially involving technologies such as electrical heating and phase-change materials. The longer ‘zero-flow’ operation of the exhaust system in hybrid applications and the associated light-out risk have demanding accuracy requirements for heat loss calculations and require additional thermal management strategies. This paper discusses the additional challenges posed with regard to catalyst modeling in the boundary conditions of electrified vehicles and the necessary improvements that go beyond the state-of-the-art techniques. Most of the necessary improvements are linked to advanced 3D modeling of the exhaust system components accounting for free convection and radiative heat t...
The paper presents the results of the effect of various fuel economy technologies on the certifie... more The paper presents the results of the effect of various fuel economy technologies on the certified CO2 emissions of light duty vehicles. The vehicles operate under two different driving cycles, namely the New European Driving Cycle (NEDC) and the Worldwide harmonized Light duty Test Procedure (WLTP), which is considered closer to real world driving and is going to be the new type approval test in the near future. The study focuses on the comparative evaluation of the effect of each technology on CO2 emissions under these two driving cycles. To this aim, simulation models for a number of passenger cars were developed and validated against test data, generated via a specifically developed test protocol. In order to cover a large share of the market, the European fleet was divided into a number of segments based on specific vehicle characteristics and technologies, and representative vehicles for each segment were chosen. In order to minimize flexibilities and sources of uncertainty, the models were developed according to a standardized modelling procedure, based on the development of a reference "template model". AVL's Cruise was used as simulation platform. The various components and modules for each vehicle model, as well as the respective input parameters, were defined with the support of the respective OEMs. After gaining confidence in the simulation models for all the vehicles considered in the present work, additional technologies, such as start-stop, brake energy recuperation and different drivetrain configurations, were implemented in each model. Specific strategies have been defined for the implementation of individual technologies and, where needed, additional algorithms were developed in Cruise. The results show that the effect of each technology on CO2 emissions is different between NEDC and WLTP, owing to the different characteristics of each cycle. For example, the effect of start-stop on CO2 emissions is larger in NEDC, due to longer idling periods compared to
ABSTRACT The successful design and especially the control of the SCR system is a challenging proc... more ABSTRACT The successful design and especially the control of the SCR system is a challenging process that can be supported by the application of simulation tools. As a first step, we employ physico-chemically informed ‘off-line’ models that are calibrated with the help of targeted small- and full-scale tests. Despite their high level of sophistication, this SCR model is able to be integrated in a control-oriented simulation software platform and connected to other powertrain simulation blocks. The target is to use this simulation platform as a virtual environment for the development and optimization of SCR control strategies. The above process is demonstrated in the case of a passenger car SCR. The model is calibrated at both fresh and aged catalyst condition and validated using experimental data from the engine bench under a wide variety of operating conditions. Next, the calibrated model was coupled with embedded control models, developed for Euro 6 passenger car powertrains. The final simulation platform enabled the precalibration and optimization of dosing control strategies, saving significant experimental effort and costs. Finally, it allowed the realization of the sensitivity analysis of the embedded control strategies, a procedure which guaranties the controlled system's robustness to engine dispersion and drift.
In the first part of this study, an improved model for the calculation of pressure drop in partic... more In the first part of this study, an improved model for the calculation of pressure drop in particulate filters was presented with special emphasis on the soot permeability properties and its dependence on temperature and pressure. With the assumption of uniform wall flow distribution throughout the channel length, it was also possible to derive an analytical expression that was validated against experimental data on an engine bench. Using the results of pressure drop modelling, it is possible to carry out ‘inverse’ calculations of the soot mass in the filter based on the measurements of flowrate, temperature and backpressure, which forms the main subject of the present work. This approach is tested successfully against experimental data in filters of different geometry and material, yielding promising results. Such computations may be very helpful for the interpretation of experimental results in engine testing. In this paper, typical applications in the field of reaction rate asses...
This paper presents the emission characteristics of a diesel passenger car operated on low sulphu... more This paper presents the emission characteristics of a diesel passenger car operated on low sulphur fuels (8 and 38ppm) when fitted with either a catalysed diesel particle filter (DPF) or a non-catalysed one combined with a fuel-borne catalyst. Measurements were conducted ...
The importance of traffic on air quality has dropped in a financial crisis hit city. Biomass for ... more The importance of traffic on air quality has dropped in a financial crisis hit city. Biomass for domestic heating has significantly worsened the air in residential areas. Better control of biomass burning needed to alleviate air quality impacts. a b s t r a c t Airborne urban particulate and gaseous pollutants measurements were conducted at the kerbside of a busy road and at a nearby urban background site of Thessaloniki, Greece, during a winter and a summer period. The main objective was to observe how the financial crisis has affected the air quality in the city, compared to previous measurements. Compared to a study conducted in 2006, the current work suggests that although average concentrations at the traffic affected site remain higher that in the urban background station, the differences are much smaller than in the past. A number of observations suggest a scenario of decrease in traffic activity and increase in biomass burning for residential heating. On this basis, the results suggest that traffic may be less important as an air quality contributor in a financially hit city. On the contrary, domestic heating appears as a significant contributor and affects areas of the city that were earlier not being of environmental concern. Because of the impact of biomass burning in residential areas, exposure calculations are required to estimate whether traffic or biomass burning is the overall highest contributors to daily PM dosages that citizens of the city are exposed to.
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Papers by Zissis Samaras