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Since 2013, Euro VI heavy-duty on-road vehicles have been on the market in the Europe. Regulated exhaust emissions, including nitrogen oxides and particulate matter, have been cut down to a very low level, independent of fuel (diesel or natural gas). Multiple research papers have shown that the regulated emissions from the Euro VI and US 2010 heavy-duty on-road vehicles tested on chassis dynamometers really deliver emission levels which correspond the type approval requirements, independent of the test cycle used. In-service conformity (ISC), which is included in the Euro VI legislation, requires heavy-duty on-road engine manufacturers to test and prove their engines to comply with the emission legislation during the engine in-use period. The measurements are carried out in the field using PEMS (Portable Emission Measurement System) equipment. This kind of testing, depicting real-world emissions is the final stage to confirm low real-life emissions. Although there is evidence that the exhaust aftertreatment systems of Euro VI heavy-duty on-road engines work well on an average, there is only a limited data of city buses covering their functionality over longer operation periods, especially not at lower ambient temperatures. Especially reduction of nitrogen oxides in the SCR-system (Selective Catalytic Reduction) is sensitive to SCR catalyst operation temperature, and also to impurities transferred from engine oil or fuel. This paper present results of a unique combination of chassis dynamometer measurements, on-road PEMS measurements and continuous NOx-emission monitoring during operation in winter condition from four Euro VI diesel city buses operating in the Helsinki metropolitan area. Based on the research done, four Euro VI city buses monitored and measured during the project showed decreased NOx conversion rate and increased tailpipe NOx emissions when operating in ambient temperatures below 0 °C. Especially in ambient temperatures below -10 °C, the continuous monitoring showed dramatically increased tailpipe NOx concentrations.

The CFD simulation of diesel combustion needs as accurate initial values as possible to be reliable. In this paper the effect of spatial distribution of state and turbulence values at intake valve closure to those distributions prior to SOI is studied. Totally five cases of intake and compression stroke simulations are run. The only change between cases is the intake boundary condition of turbulence. In the last case the average values of p, T, k, ε and swirl number at intake valve closure are used as initial values to compression simulation. The turbulence in the engine cylinder is mainly generated in the very fast flow over the intake valves. In this paper the effect of boundary conditions of turbulence to its level at intake valve closure is studied. Several cases are simulated with different boundary conditions of turbulence. Also the swirl number is compared to experimental value. The discharge coefficients over the valves calculated from simulation results are compared to measured values. Simulated engine is a single-cylinder research engine is based on a commercial 6-cylinder off-road common rail diesel engine.

Over the years, natural gas has been promoted as a clean-burning fuel, especially for transit buses. A decade ago one could claim that natural gas buses deliver significant emission benefits over diesel buses, especially regarding particulate emissions. The spread in nitrogen oxide emissions has always been significant for natural gas engines, high for lean-burn engines and low for three-way catalyst equipped stoichiometric engines. With the introduction of US 2010 and Euro VI (effective as of 2014) exhaust emission regulations, independent of the fuel, the regulated emissions of all engines have been brought close to zero level. This means that the advantage of natural gas as a clean fuel is diminishing, especially in a situation in which electric transit buses are also entering the market. The motivation to use natural gas could still be diesel fuel substitution and to some extent, also reduction of greenhouse gas emissions. However, looking at the full fuel cycle and also taking into account methane leakages in various part of the fuel cycle, natural gas is, at its best, comparable to diesel regarding greenhouse gas emissions, not better. One of the reasons for this is the low fuel efficiency of spark-ignited gas engines compared to diesel engines. To deliver an advantage regarding greenhouse gas emissions, the efficiency of the gas engines should be significantly improved. Alternatively natural gas should be replaced with biogas. The paper presents a comparison of diesel and natural gas buses for regulated emissions, selected unregulated emission components, greenhouse gas emissions and energy efficiency.

Helsinki Region Transport, Neste Oil, Proventia Emission Control and VTT Technical Research Centre of Finland carried out a 3.5 year PPP venture "OPTIBIO" to demonstrate the use of paraffinic renewable diesel (hydrotreated vegetable oil HVO) in city buses. The fleet test in Metropolitan Helsinki involving some 300 buses is the largest one in the world to demonstrate this new fuel. The fuels were a 30 % blend of renewable diesel and 100 % renewable diesel. This paper describes the overall set-up of the project, gives an overview of the emission results as well as presents experience from the field.

Cold operating environment has many kinds of negative effects on the use of automobiles. Low ambient temperature degrades start-up performance and increases fuel consumption. Hence, the amounts of exhaust emissions are also elevated. In particular, high concentrations of CO and HC are present in the exhaust. Cold-start derates especially the performance of a TWC type of emission reduction. Therefore, an increasing emphasis has been set to the testing of exhaust emissions even at sub-ambient temperatures, For this reason, US-EPA has recently revised US emission regulations by comprising an additional low ambient temperature (20°F = -7°C) test for CO emissions. Apart from the regulated components, other poisonous compounds have been detected from the exhausts, although usually in very small quantities, A cold-start may have an increasingly strong effect even to the emission of these substances. Therefore, as many as possible of these compounds should be included into the low temeperature emissions analysis. Current methods for detecting these components are primarily based on ‘wet chemistry’. Therefore, they are very laborous and allow no real-time analysis of transient phenomena. However, recent R&D efforts have made fast FTIR-technology available also to the engine exhaust analysis applications. The paper lists some preliminary results for this type of work.

Over the past decade significant research and development activities have been invested in alternative fuels in order to reduce our dependency on fossil fuel sources and reduce CO2 and local emissions from traffic. One result of these R&D efforts is paraffinic diesel fuels, which can be used with existing vehicle fleets and infrastructures. Paraffinic diesels also have other benefits compared to conventional diesels, for example a very high cetane number and the lack of sulfur and aromatic compounds. These characteristics are beneficial in terms of exhaust gas emissions, something which has been demonstrated in numerous studies. The objective of this study was to develop low-emission combustion technologies for paraffinic renewable diesel in a compression ignition engine, and to study the possible benefits of oxygenated paraffinic diesel. Hydrotreated vegetable oil (HVO), which is a commercial example of paraffinic, renewable diesel, was used with and without oxygenate in comparison with conventional diesel. Exhaust emissions were measured in three steady state conditions. The adjusted engine parameters, such as inlet valve closure and injection timing, injection pressure and amount of exhaust gas recirculation (EGR) were optimized for HVO. The results demonstrate that significant reductions of particulate matter (48-61%), polyaromatic hydrocarbon (75-87%) and NOx (31-54%) emissions can be achieved simultaneously by using HVO with adjusted engine parameters.

A new tool for SCR (selective catalytic reduction) testing is developed. This side stream test bench has an advantage to test smaller catalysts with a proper exhaust. The exhaust mass flow and temperature are adjustable. A control program is developed to adjust and save the needed parameters. NOx sensors are utilized in the test bench to measure the levels upstream and downstream of SCR reactor. In this study one SCR with a volume of 40.5 dm 3 is tested with exhaust flows ranging from 400 to 600 kg/h and exhaust temperatures from 280 to 360 °C. The tests are conducted using exhaust gas from a medium speed diesel engine running on heavy fuel oil. A decrease from 75% to 99% (depending on test conditions) was observed in NO x over the catalyst. In addition HC and PM were found to decrease while CO was increased over the catalyst. The controlling of exhaust flow and temperature with the test bench succeeded with only minor errors. The measured value of exhaust flow deviated from the set value in the order of 1% and temperature in the order of 0.1%. The results of NOx sensors correlated well with the standardized NOx measurement results with an exception being the case when ammonia slip was formed. When ammonia was found in the exhaust the NOx sensors were observed to misleadingly measure the ammonia as NOx. The results with different exhaust flow rates revealed that SCR was performing better when the flow was lower i.e. the space velocity was lower. At higher temperatures higher NOx conversions were observed. At 360 °C the NOx conversion was near 95% while at 280 °C the conversion was 75%. Copyright © 2012 SAE International.

Hydrotreated vegetable oil (HVO) named NExBTL is a 2nd generation renewable diesel fuel made by a refinery-based process converting vegetable oils to paraffins. Also animal fats are suitable for feedstocks. Properties of this non-ester type biobased fuel are very similar to GTL. It contains no sulfur, oxygen, nitrogen or aromatics. Cetane number is very high (∼90). Cloud point can be adjusted by severity of the process from -5 to -30°C, heating value is similar to diesel fuel, storage stability is good, and water solubility is low. Emissions of two heavy duty engines and two city buses are presented with HVO and sulfur free EN 590 diesel fuel. The effect of HVO on regulated emissions compared to EN 590 fuel was: NOx -7 % ⋯ -14 % PM -28 % ⋯ -46 % CO -5 % ⋯ -78 % HC 0 % ⋯ -48 % Aldehydes, PAHs, mutagenicity and particulate size were also measured.

The effect of after-treatment on size distribution of heavy duty diesel exhaust is studied with a measurement system sampling directly from the tailpipe. After-treatment systems studied are diesel particulate filter (DPF), oxidation catalyst, and selective catalytic reduction (SCR) technique. Only low level sulfur fuels are used. DPF effectively reduces accumulation mode particles but the formation of ultrafine particles was observed at high load. Oxidation catalyst and SCR system slightly reduce accumulation mode in low load, probably because of the higher volatile fraction of the particles at low load. At high load, ultrafine particles are formed with both catalyst systems resulting most probably from SO3 formation over the oxidation catalyst. With SCR, possible ammonia slip may also contribute to particle formation.

The effect of total olefin content on ozone forming potential has been widely studied. As a result a stringent limit for olefins is already given in California Specification for “Phase 2” gasoline and the 18 vol% limitation of olefins is expected to tighten also in Europe. However, it is not clear how determining the light olefins are and what is the role of heavy olefins regarding ozone forming potential.Ethanol is widely used as gasoline component in many countries, but not extensively in Europe. The biofuels have the potential to provide a renewable source of energy and contribute to lower global CO2 emissions. The unregulated emissions, especially particulates and their quality have not been studied extensively with ethanol containing gasoline using European test fleet.The objective was to study the applicability of heavy olefins in non-oxygenated and ethanol oxygenated gasolines. Alkylates in gasoline were replaced by isooctene. Exhaust emission were measured and ozone forming potential was estimated.Adding heavy olefins in the form of isooctene showed no major changes in the tailpipe exhaust emissions: regulated emissions, particulate matter, carbon dioxide emission, fuel consumption or unregulated emissions. However some changes for individual hydrocarbons were seen. The preliminary work and estimations indicated that adding isooctene would not increase the ozone forming potential. Thus no real environmental benefit is expected, if the total content of olefins is limited. The limitation should cover only the amount of light olefins (C5 and lighter).According to our measurements it is also possible to replace ethers to ethanol with same volumetric content without degrading exhaust emissions.

Major part of the research work on particulate emissions has been carried out at normal ambient temperature (about +23 °C). In real life, the average day temperatures, especially in the winter season, are far below the “normal” temperature of the exhaust emission test procedures. For many years, it has been obvious that the knowledge of the total particulate mass emissions is not enough. Quality of these particles, e.g. polyaromatic hydrocarbon content and mutagenicity, has been studied. Now there is also a need to gain more information on fine particles, which can penetrate lungs more easily. International Energy Agency's Committee on Advanced Motor Fuels sponsored this study of the possible effect of ambient temperature on particle emissions. Also aldehydes and speciated hydrocarbons were studied.Several different engine and fuel technologies were covered, including gaseous fuels and biodiesel. Research work focused on light-duty technologies. Test vehicles were as follows: two diesel cars (direct and indirect-injection), stoichiometric gasoline fuelled car (multi-port-fuel-injection), direct-injection gasoline car, Flexible Fuel Vehicle running with E85 fuel, CNG and LPG cars. Four diesel fuel qualities were studied: European grade diesel fuel (EU2000), a blend of this fuel and 30% rape seed methyl ester (RME30), Swedish Environmental Class 1 fuel (RFD) and a blend of this fuel and 30% RME (RFD/RME).The effect of temperature was dependent on the engine technology. Significant increase in particle mass and number emissions was seen with some technologies when -7 °C temperature was compared to normal test temperature. Some engine technologies were rather insensitive to ambient temperature, e.g. CNG car did not show any significant particle emission at normal or low temperatures. If an increase in particle emissions was seen, it typically appeared immediately after the cold start. With the warmed-up engine the particle emissions were mainly at the same level at normal and low temperatures. In some cases RME indicated more particles and/or a shift to lower mean diameter at low temperatures after the cold start than in the tests at normal temperature.

Electrical low pressure impactor ELPI was modified to measure particles below 30 nanometers in aerodynamic diameter. This was accomplished by adding a filter stage to collect and measure nanoparticles. The charging unit of the instrument was modified to increase the charging efficiency of the smallest, nanometer sized, particles. The modified charging unit was calibrated and the new construction of the ELPI was tested in laboratory and in vehicle dynamometer test cell. Measurements performed in the engine test cell showed that modifications improve the size range and measurement capability of the ELPI for engine emissions.

Effect of lubricant on particle emissions was studied using two heavy-duty diesel engines. Both particulate mass and particle number distribution were measured. Differences between lubricants were studied by dosing two percent of each lubricant (diesel engine oil) to diesel fuel. This arrangement was seen necessary to get clear differences between lubricants. The lubricant had a clear effect on particulate mass emissions. Two of the lubricants gave about the same emission as pure diesel fuel. The worst result was more than two times higher than without oil added to the fuel. The lubricants were all diesel engine oils with different base oils/additive package. Lubricant ash content presumably affects particulate mass. However, the difference in ash content between lubricants was no higher than 30%. Therefore, ash content can only partly explain the differences. The combustion characteristics and the sulphur content of the base oil are essential, too. All fuels containing lubricant produced higher number of small particles than pure diesel fuel. The lubricant, which gave the lowest particulate mass result, produced the highest number of particles. The reason might be that when the number of large particles decreases (also particle mass decreases), the small particles cannot agglomerate to the surfaces of larger particles. It is also possible that, for example, oxidation of catalyst could reduce the number of small particles.

The main purpose of this investigation was to develop the virtual prototype of the whole log forwarder by using ADAMS dynamic system simulation software. The virtual prototype contains hydraulic systems of the loader (except the grapple), mechanisms (steering, bogie axles), tire-terrain interaction, the log loader with structural flexibility and the control systems of the loader. Then the virtual prototype was validated with a simple procedure describing loading dynamics.

In a diesel engine, both physical and chemical properties of the fuel affect exhaust emissions. This study focused on the separation of some physical and chemical effects of the fuel on the NOx emission. The tests were conducted with a bus engine using four diesel fuels with different density and aromatics levels. The measurements were performed using five injection timing settings to screen the effects of changes in actual injection timing. When conventional diesel fuel was replaced by reformulated diesel, NOx was reduced 7-13 %. Changes in the injection timing due to differences in the physical properties accounted only for a minor part (10-25 % relative) of the total reduction of NOx, whereas the greater part of the reduction (75-90 % relative) was due to other reasons, mainly fuel chemical properties.

Future fuel formulations including classic refining schemes (hydrotreatment) and synthetic blending stocks like Fischer-Tropsch, oligomerate and high cetane linear ethers were tested for their impact on diesel emissions in various engine conditions (transient and cold operations). CO, HC, Aldehyde, Particulate and PAH emissions are highly sensitive to fuel quality whereas NOx emissions are only slightly modified. Very low level of pollutants is obtained with the Fischer-Tropsch fuel. Oligomerisation fuel induces an increase in CO, HC, aldehyde emissions due to its very low cetane number but presents low emissions of particulates and smoke because of its paraffinic composition. Pentyl ether behaves essentially as a high cetane paraffinic hydrocarbon. The relationships between fuel parameters and emissions were also assessed: CO, HC and aldehyde emissions depend on the cetane number. Particulates, IOF, smoke and PAHs are controlled by aromatic content and density. Density also controlled NOx emissions but with far less variation. Fuel quality can also help to reach a better NOx/particulates trade-off with EGR. Tall-oil methyl ester containing fuel offers a good potential for low emissions because of the beneficial effect of oxygen on particulates.

The purpose of our study was to investigate the effects of TAME and heavier ethers on reformulated gasoline. The research work focused on the comparison of Californian Phase 2 gasoline (CARB), current Finnish reformulated gasoline containing MTBE (RFG1), or MTBE+TAME+heavier ethers (RFG2) with non-oxygenated Eurograde gasoline (EN228). Significant reductions in exhaust emissions were achieved with all reformulated fuels when compared to the Eurograde fuel. For instance, benzene emissions were reduced as much as 40 to 50 % for all cars at two temperatures and the emissions of total toxics were reduced by 14 to 45 % depending on vehicle type and temperature. The lowest 1,3-butadiene emissions were achieved with CARB gasoline. The amount of PAH compounds in the particulate matter from the non-catalyst vehicle was lower with the reformulated fuels than with the Eurograde fuel. The amount of volatile PAH compounds in semivolatile phase of particles seemed to be reduced with reformulated gasoline as well. As gasoline blending components TAME and heavier ethers proved to be as good as MTBE. Additionally they improved the octane number distribution of reformulated gasolines.

Unregulated emissions of reformulated diesel fuels (sulfur < 50 ppm, aromatics < 20 vol-%) were compared to the European EN590 specification fuel (sulfur < 500 ppm, aromatics < 35 vol-%) in three IDI passenger cars and one DI van using FTP and/or ECE/EUDC emission test procedures. The effect of reformulated diesel fuels on the mutagenicity of particulate soluble organic fraction (SOF) was studied. Fuel reformulation reduced particulate emissions in IDI cars. Reformulating fuel by decreasing heavier aromatics-without decreasing final boiling point-reduced particulate mutagenicity on emission basis. At low ambient temperature (-7°C) particulate PAH and mutagenic emissions increased compared to the standard ambient temperature (+22°C) with all fuels.

Propane is considered to be a viable fuel alternative for low-emission heavy-duty vehicles in Finland. Natural gas and propane have roughly the same potential for reduced exhaust emissions. Since natural gas and propane are both imported fuels in Finland, there is no preference between these two fuels. Propane, however, is much more easy to distribute, refuel and store onboard the vehicle. This is why propane has received more attention than natural gas as an automotive fuel.Work to develop a low-emission propane fueled truck started back in 1988 with engine tests. The first prototype, a 17-ton SISU truck was built in 1990, and was operated until September 1992. This truck was equipped with a 7.4-liter Valmet-engine, a closed-loop controlled IMPCO-fuel system and a three-way catalytic converter (TWC).The experience with this propane fueled truck was good. The driveability was excellent, and both noise level and exhaust emissions were low. The following emission results were obtained in the European 13-mode (ECE R49) emission test with a three-way catalyst aged for 30.000 km: CO 1.8, THC 0.5 and NOx 0.5 g/kWh.Encouraged by these good results the Finnish truck manufacturer Oy Sisu-Auto Ab decided to build a test fleet of seven propane fueled trucks. These trucks were built in late 1992/early 1993. One of these trucks is used for test and demonstration purposes, and six trucks have been delivered to five different operators for various applications like municipal waste collection, distribution work and street maintenance. A surveillance program concerning these trucks is currently under way.In the years 1990-1993 a surveillance project on a propane fueled MAN-citybus was carried out concurrent with the truck operations. This vehicle also uses TWC technology. The surveillance work included both weekly checkups on the fuel system and catalysts. Furthermore, altogether six measurements were carried out on a chassis dynamometer according to a modified ECE R49 procedure.In April 1993 the total accumulated driving distance was some 200.000 km and the bus has worked relatively well, although some minor technical problems have occurred. Judged by the emission test, the original catalyst had lost 50% of its efficiency at 80.000 km. This catalyst was then replaced with a converter from the Finnish company Kemira Oy. With this new catalyst, extremely low emission values were obtained.

Using fast FTIR-technology (Fourier Transform Infra-Red) to complement the normal regulated emission analysis, VTT Energy has performed exhaust emission measurements for several light-duty motor vehicles (passenger cars) representing a variety of current level technologies, mostly employing a three-way catalytic converter. Tests have been performed using standardized test procedures and driving cycles (U.S.EPA and ECE/EEC). Apart from the basic technology of the vehicle, ambient temperature has also been varied. Most of the tests are run at +20 to +22 °C ambient temperature, but additional tests have been carried out at ±0°C, -7 °C and even at -20 °C.Test results suggest that nitrous oxide output varies largely from vehicle to vehicle, and its is also dependent on the ambient temperature. Most significant factor, however, seems to be vehicle mileage, or rather catalyst activity, as already suggested in previous studies. Furthermore, the detailed time resolved analysis supports the theory presented in the literature, that nitrous oxide is formed in a three-way catalytic converter within certain temperature range below the normal operating temperature.