High levels of particulate emissions from Diesel engines, in tunnel construction sites, force the aftertreatment of exhaust gases with particulate traps. Sub-micron particulates are suspected to be carcinogenic. Hence, the size distribution of particulates was compared for different particulate trap systems. The two extreme types are the ceramic monolith surface filter and the typical deep-bed filter of knitted fiber. These two types have distinctly different properties. The gravimetric evaluation of both systems show comparable efficiencies around 90%. If, instead, the particle count is evaluated: the efficiency of the surface filter drops below 70%, whereas that of the deep-bed filter increases. The spectral analysis of distinct solid particulates shows that the efficiency of the surface filter deteriorates for particles smaller than 100 nm. The toxicological consequences are disquieting.
Four of these Particulate Reduction Systems (PMS) were tested on a passenger car and one of them on a HDV. Expectation of the research team was that they would reach at least a PM-reduction of 30% under all realistic operating conditions. The standard German filter test procedure for PMS was performed but moreover, the response to various operating conditions was tested including worst case situations. Besides the legislated CO, NOx and PM exhaust-gas emissions, also the particle count and NO2 were measured. The best filtration efficiency with one PMS was indeed 63%. However, under critical but realistic conditions filtration of 3 of 4 PMS was measured substantially lower than the expected 30 %, depending on operating conditions and prior history, and could even completely fail. Scatter between repeated cycles was very large and results were not reproducible. Even worse, with all 4 PMS deposited soot, stored in these systems during light load operation was intermittently blown-off.
Due to the limited energy resources as well as due to increasing CO2-emissions the importance of alternative- and biogene fuels increases continuously. Investigations of the engine operation were performed on a latest technology Liebherr engine for construction machines, which was operated using crude rapseed oil (ROR), rapseed methyl ester (RME) and synthetic Gas-To-Liquid fuel (GTL) without any change of ECU setting. On this occasion the combustion diagnostics, behaviour of the injection system and the pollutant emissions, including the unlimited nano-particles were especially assessed. For injection (with this unit pumps system) it can be stated, that ROR and a little bit less RME shorten the injection lag and increase the maximum injection pressure. At higher engine load this causes the 50% heat release a little earlier (1-2°CA) and as consequence higher NOx and lower specific energy consumption.
1 During the research programs of the Swiss Federal Office of Environment Forests and Landscape (FOEFL) - and as a contribution to to the European project ARTEMIS*) analysis of limited and nonlimited emissions of motorcycles was performed. Exhaust emissions measurements of two motorcycles without catalyst: 4-stroke 750 cc and 1100 cc have been performed in the present work. Identical driving cycles have been repeated and the influence of the cooling duration on the emissions at cold start was investigated. A cold start in the temperature range of 20 ÷ 25 °C can be regarded as a “summer cold start”. As nonlimited emissions the nanoparticulate emissions at cold and warm operating conditions were measured by means of SMPS and NanoMe**). The measurements were performed at steady state and at transient operating conditions. The present work cleared up several details about the emissions of strong motorized motorcycles.
1 Analysis of limited and nonlimited emissions of scooters was performed during several research programs of the Swiss Federal Office of Environment Forests and Landscape (FOEFL) - and as a contribution to the European project ARTEMIS*). Small scooters, which are very much used in the congested centers of the European cities are a remarkable source of air pollution. Therefore every effort to reduce the emissions is an important contribution to improve the air quality in urban centers. In the present work detailed investiga-tions of a Peugeot scooter with TSDI (Two Stroke Direct Injection) were per-formed and the emissions were compa-red to the other 2-S & 4-S scooters. As nonlimited emissions the nanopar-ticulate emissions at cold and warm operating conditions were measured by means of SMPS, ELPI and NanoMet*). The measurements were both: at steady state and at transient operating conditions.
Metallic substances, usually added to fuel as organic compounds are, as fuel additives proven to curtail particulate emissions from diesel engines and, as fuel borne catalysts (FBC), to promote regeneration of particle traps. During combustion, these substances form catalytic metal oxides and exit the combustion chamber as ultra-fine solid clusters in the mobility diameter range of 5-30 nm. Particles of this size and composition have a health impact and should not enter the respiratory air. FBC should therefore only be used together with particle traps, which can efficiently collect these metal oxide particles at all operating conditions. This and other requirements are stipulated in the VERT suitability tests for particle trap systems. The approval procedure includes a particle size-specific analysis to verify trap penetration in trace quantities.
Most particulate traps efficiently retain soot of diesel engine exhaust but the potential hazard to form secondary emissions has to be controlled. The Diesel Particle Filter (DPF) regeneration is mainly supported by metal additives or metallic coatings. Certain noble or transition metals can support the formation of toxic secondary emissions such as Dioxins, Polycyclic Aromatic Hydrocarbons (PAH), Nitro-PAH or other volatile components. Furthermore, particulate trap associated with additive metals can penetrate through the filter system or coating metals can be released from coated systems. The VERT test procedure was especially developed to assess the potential risks of a formation of secondary pollutants in the trap. The present study gives an overview to the VERT test procedure. Aspects of suitability of different fuel additives and coating metals will be discussed and examples of trap and additive induced formation of toxic secondary emissions will be presented.
Based on the emission inventory Fig. 1, the Swiss 1998 Ordinance on Air Pollution Control (OAPC) mandates curtailment of carcinogenic diesel particle emissions at type B construction sites . Moreover, particle traps are compulsory at underground workplaces . In compliance, more than 6,000 Diesel engines were retrofitted with various particle trap systems. Many traps surpassed 99% filtration efficiency and secondary emissions were mostly prevented. However, trap failure due to mechanical and thermal damage was initially rather high at about 10%. By the year 2000 the failure rate was halved to about 6%. Thanks to focussed improvements, the year 2003 statistics show yearly failures of “only” about 2%. The Swiss target is to retrofit 15,000 construction machines with traps, fully compliant with environmental directives, having 5,000 operating hours durability and failure rates below 1%. Traps must pass the VERT suitability test before deployment.
Particulate traps are mechanical devices for trapping soot, ash and mineral particles, to curtail emissions from Diesel engines. The filtration effectiveness of traps can be defined, independent of the pertinent engine, as a function of the particle size, space velocity and operating temperature. This method of assessment lowers cost of certifying traps for large-scale retrofitting projects [1,2]. VERT  is a joint project of several European environmental and occupational health agencies. The project established a trap-verification protocol that adapts industrial filtration standards  to include the influence of soot burden and trap regeneration phenomena. Moreover, it verifies possible catalytic effects from coating substrates and deposited catalytic active material from engine wear or fuel/ lubricant additives.
1 The VERT project aimed at curtailing the construction site diesel emissions of ultra-fine particles to 1% of the raw emissions. Thus, compliance with occupational health legislation should be achieved. Particulate traps have attained this target. In contrast, engine tuning, reformulated fuels and oxidation catalytic converters are almost ineffective. This paper reports on the concluding project stage in which 10 traps were field tested during 2 years. Subsequent detailed measurements confirmed the excellent results: > 99% filtration rate was achieved in the nano-particulate range. The PAH, too, were very efficiently eliminated. Trap deployment becomes therefore imperative to fulfill VERT-targets.
Increasing concern, about the health risk due to solid aerosols from engine combustion, has provoked more stringent imission limits, for soot particles in the range of pulmonary intrusion, at critical work-places (e.g. tunnel sites, see Table 1). Within the scope of the joint European project VERT, these emissions were characterized and their effective curtailment through exhaust gas after-treatment investigated. Diesel engines, irrespective of design and operating point, emit solid particulates in the range of 100 nm, at concentrations above 10 million particulates per cm3. Engine tests showed that a drastic curtailment of pulmonary intruding particulates seems not feasible by further development of the engine combustion, nor by reformulation of fuels, nor by deployment of oxidation catalytic converters. Particulate traps, however, can curtail the total solid particulate count, in the fine particulate range 15-500 nm, by more than two orders of magnitude.
1 Occupational Health Authorities in Germany and Switzerland require the use of particulate traps (PT) on construction machines used in underground and in tunneling since 1994. Swiss EPA has extended this requirement 1998 to all construction sites which are in or close to cities. During the VERT*-project, [1, 2, 3, 4, 5]**, traps systems were evaluated for this purpose and only those providing efficiencies over 95% for ultrafine particles < 200 nm have received official recommendation. 10 trap-systems are very popular now for these application, most of them for retrofitting existing engines. Efficiency data will be given as well as experience during a 2-years authority-controlled field test. LIEBHERR, producing their own Diesel engines in Switzerland and construction machines in Germany is the first company worldwide supplying particulate traps as OEM-feature (Original Equipment Manufacturing) on customers request.
1 Switzerland is enforcing the use of particulate traps for offroad applications like construction as well as for occupational health applications like tunneling. This decision is based on the results of the VERT-project (1994-1999), which included basic aerosol research, bench screening and field testing of promising solutions as well as the development of implementation tools like trap specification, certification scheems and field control measures. On the other hand there is no corresponding regulation for city-buses yet although PM 10 is about 2× above limit in most Swiss cities. Public pressure however is growing and city transport authorities have reacted by retrofitting Diesel city-buses instead of waiting for cleaner engine technology or CNG-conversions. The favored trap system with about 200 retrofits so far is the CRT.
1 Small scooters are very much used in the congested centers of the European cities. Even if there is a continuous technical progress, the small two-wheelers are a remarkable source of air pollution. During the research programs of the Swiss Federal Office of Environment Forests and Landscape (FOEFL) - and as a contribution to the European project ARTEMIS *) analysis of limited and nonlimited emissions of scooters was performed. Exhaust emissions measurements of two Scooters: 4-stroke 125 cc and 2-stroke 50 cc have been performed with and without catalyst. Identical driving cycles have been repeated and the influence of the cooling duration on limited the emissions at cold start was investigated. A cold start in the temperature range of 20 - 25 °C can be regarded as a “summer cold start”. As nonlimited emissions the nanoparticulate emissions at cold and warm operating conditions were measured by means of SMPS, ELPI and NanoMet *).
Due to increasing concern about health effects of fine and ultra-fine particles (nanoparticles) from combustion engines, the diesel particle filter technology (DPF) *) was extensively introduced to heavy duty and passenger cars in the last years. In this respect, a very important parameter is the irreversible plugging of the DPF with non-combustible ashes. The quality of lubrication oil, especially the ash content has a certain influence on regeneration intervals of diesel particle filters. In the present study, the effects of different lubrication oils on particle mass and nano-particle size distribution were investigated. The test engine was a modern diesel engine without particle filter system. A main goal was to find out, how different lubrication oils influence the particulate emissions and the contribution of oil to total particle emissions. Moreover, first results of a tracing study will be discussed.
Limited and nonlimited emissions of scooters were analysed during several annual research programs of the Swiss Agency of Environment Forests and Landscape (SAEFL, BUWAL)*). Small scooters, which are very much used in the congested centers of several cities are a remarkable source of air pollution. Therefore every effort to reduce the emissions is an important contribution to improve the air quality in urban centers. In the present work detailed investigations of particle emissions of a Peugeot scooter with TSDI (Two Stroke Direct Injection) were performed. The nanoparticulate emissions with different lube oils and fuels were measured by means of SMPS, (CPC) and NanoMet *). Also the particle mass emission (PM) was measured with the same method as for Diesel engines. It can be stated, that the oil and fuel quality have a considerable influence on the particle emissions, which are mainly oil condensates.
1 Analysis of limited and nonlimited emissions of scooters was performed during several research programs of the Swiss Federal Office of Environment Forests and Landscape (FOEFL) - and as a contribution to the European project ARTEMIS *). Small scooters, which are very much used in the congested centers of the European cities are a remarkable source of air pollution. Therefore every effort to reduce the emissions is an important contribution to improve the air quality in urban centers. In the present work detailed investigations of a Peugeot scooter with TSDI (Two Stroke Direct Injection) were performed and the emissions were compared to the other 2-S & 4-S scooters. As nonlimited emissions the nanoparticulate emissions at cold and warm operating conditions were measured by means of SMPS, ELPI and NanoMet *). The measurements were both: at steady state and at transient operating conditions.
Fine pored hot gas traps have filtration efficiencies exceeding 99% of the solid particles in the diesel exhaust gas. There is a favorable trend to deploy this technology ex-factory and retrofitting on-road and off-road engines. The trap system however functions as a chemical reactor. The filter has a large effective area and the engine exhaust gas has plenty of reactants, which can promote undesirable chemical reactions that release toxic secondary emissions. These effects may be amplified when traps have catalytic influence, e.g. due to surface coatings or fuel-borne catalysts. The VERT suitability tests for particle trap systems therefore include a detailed test procedure for verifying the presence of over 200 toxic substances. These include PAH, nitro-PAH, chlorinated dioxins, furans as well as metals. The paper describes test procedures, test reporting, sample extraction and analysis.
1 Small off-road 4-stroke SI-engines have extraordinarily high pollutant emissions. These must be curtailed to comply with the new Swiss clean air act LRV 98. The Swiss environmental protection agency (BUWAL) investigated the state of the technology. The aim was a cleaner agricultural walk behind mower with a 10kW 4-stroke SI-engine. Two engine designs were compared: side-valve and OHV. A commercially available 3-way catalytic converter system substantially curtailed emissions: In the ISO 8178 G test-cycle-average, HC was minimized to 8% and CO to 5% of raw emissions. At part load points, the residual emission was < 1%. Simultaneously, fuel consumption improved 10%. Using a special gasoline (Swiss standard SN 181 163), the aromatic hydrocarbons were curtailed, e.g. Benzene < 1%, and fuel consumption further improved. Those results were confirmed in field tests. The engine is approved for retrofitting.