Taşıt egzoz emisyonları ve İTÜ motorlar ve taşıtlar laboratuarında 1993-1995 yılları arasında yapılan ölçümlerin değerlendirilmesi

Abstract

Bu çalışma temelde iki ana bölümden oluşmaktadır. Birinci bölümünde motorlu taşıtlardan kaynaklanan egzoz kirleticilerinin oluşumu insan sağlığı üzerindeki etkileri önleme yöntemleri ve bu konuda getirilen yasal önlemler ile bunların güncel uygulamaları hakkında bilgi verilmiştir. Birinci ana bölüm çalışmanın 1. ila 5. maddeleri arasında anlatılmıştır. İkinci ana bölümde ise önce İ.T.Ü. Motorlar ve Taşıtlar Laboratuarındaki deney düzeneği anlatılmış ve yapılan ölçüm ve deney sonuçlarının hesaplanması hakkında bilgi verilmiştir. Bu bölümün en sonunda 1993 - 95 tarihleri arasında yapılan deney sonuçlan toplu halde değerlendirilmiş ve çeşitli tablo ve grafikler ile taşıt motoru emisyon özellikleri irdelenmeye çalışılmıştır. Deneysel çalışmanın sonuçlan toplu halde çeşitli parametrelere göre incelendiğinde daha önceden beklenen bazı anlamlı ilişkiler gözlenmiştir.

One of the greatest problems which must be solved urgently today is the atmospheric pollution caused by motor vehicles. To the solution of this problem can be reached not only with government legislation's, but with participation of everyone of us who like life and our beautiful globe. From 1993 in our Motor and Vehicles Laboratories in İ.T.Ü. we measure the exhaust emissions of the vehicles imported or produced in Türkiye and give reports about their conformity with standards ECE 15.04 and EURO 93 (from 1995). I am glad that I also take place in this staff which carries these measurements and conclusions. So I am feeling also that I am responsible to transfer my knowledge and experiences to everyone who want or who would be interested of them. This work I began with answering the questions what is the atmospheric pollution and how it effects our health. Then I wrote about contribution of internal combustion motor vehicles to this pollution. After that I included the test having made in our laboratory and made conclusion about a hundred vehicles testing results. In the second chapter I wrote about toxicity of exhaust gases emitted by vehicles. Although this may seem unnecessary for engineers, there are very good reasons for accentuating its importance. First, the engineer must be able to play his part in formulating regulations as much time and vast resources are at stake. Secondly, in designing engines and conducting research into pollution XVIII control he should know which pollutants are dangerous. These gases are mainly combustion products of internal combustion engines. Complete combustion produces carbon dioxide ( C02 ) and water. ( H2Q )? Incomplete combustion products are. unburned hydrocarbons: CnHm ( paraffins, olefins, aromatic hydrocarbons). partially burned hydrocarbons: CnHm.CHO (aldehydes), CmHm.CO (ketones), C"Hm.COOH (carboxylic acids), CO (carbon monoxide)thermally cracked products: C2H2, C2H4, H2 (acetylene, ethylene, hydrogen etc.), C (soot), polycyclic hydrocarbons Byproducts of combustion are. from atmospheric nitrogen: NO, N02 (oxides of nitrogen); from fuel additives: lead oxides, lead halogenides; from fuel impurities: sulfur oxides Oxidants: sunlight acts on exhaust-gas constituents to produce the following oxidants: organic peroxides, ozone and peroxy-acetyl-nitrates. In the third chapter I have described where are from and how are formed emissions in transport vehicles. Mechanisms of pollutant formation in SI (spark ignition) and briefly in DE (diesel engines) is explained and discussed. Separately is brought out the influence of structural factors to formation of pollutants. These are the shape of combustion chamber, compression ratio, the shape of intake manifold, valve timing, ignition timing, injection type, turbo charging etc. so on. Influences of exploitation factors running condition is explained. Transient operating conditions are described separately. At the time the engine is started the manifold and cylinder walls are cold. In order to form a combustible mixture enough fuel must be vaporized so that the vapor- air mixture entering the cylinder is in the ignitable range. Since only part of the fuel is vaporized the fuel-air ratio formed in the carburetor must be made fuel-rich by choking. The mixture that enters the combustion chamber under this choked-carburetor condition is liquid fuel plus air-vapor mixture. During this period the exhaust will have high concentrations of HC and CO with some of the HC coming from fuel vaporized from the piston and walls late in the combustion process or during the exhaust XIX stroke. NOx should be low since the combustion temperature is low due to the vaporization of some of the raw fuel as well as the fairly low temperature of the mixture at time of ignition. After the cold start and during the warm-up period the HC and CO will gradually decrease as the engine parts get warmer. The period of time it takes an engine to "warm up" depends upon the design of the engine and inlet air system, the ambient temperature and the volatility of the gasoline, but this period is about from two to five minutes. Emission control technologies take place in the fourth chapter. First the emission control spark ignition engines. The composition of exhaust gases can be controlled in two ways: by engine design and by after-treatment. Engine design measures are: fuel metering mixture preparation uniform distribution exhaust gas recirculation (EGR) valve timing compression ratio combustion chamber design ignition system crankcase ventilation (blowby) fuel evaporation Exhaust gas after-treatment can be:. thermal afterburning: these systems include all devices which delay the passage of exhaust gases for a period of time while maintaining high temperatures, which enables subsequent reactions in the engine exhaust. In general, such systems work by oxidation with air injection.. catalytic afterburning: catalytic converters comprise an actively coated substrate enclosed in a vibration-proof and heat-insulated manner in a housing. XX Granulate and sintered A1203 monoliths are used as the substrate. Oxidation catalyst are operated either with the engine fuel mixture set to lean or by adding air for the purpose of oxidizing CO and HC. Reduction catalysts work without the addition of air such that the excess-air factor is < 1 and oxides of nitrogen are thereby reduced. The incorporation of oxidizing and reducing catalysts in the same housing or "bed" is called a dual-bed catalyst system. The three-way or selective catalyst with lambda closed loop control has proven to be a highly efficient method of spark-ignition-engine exhaust gas aftertreatment. In the fifth chapter, the exhaust emission regulations are summarised. The current status of emission-control legislation in the country concerned determines which emission- control measures are to be taken. In future will be possible to distinguish between three groups of countries:. European countries (ECE). Australia, EEC countries (countries with moderately stringent legislation). USA, Japan, Switzerland, Austria, Sweden, Canada (countries with very stringent legislation). Vehicle manufacturers have to meet these regulations, which have a considerable influence on engine design. In 1970 Regulation ECE R15 was adopted by the European Community (EEC) and published as a Community Directive (70/220/EEC). Initially these directives applied to carbon monoxide and hydrocarbons only. Several amendments followed, increasing the severity, including the addition of oxides of nitrogen in 1977 (ECE 15.02). In the fourth amendment (ECE 15.04) severity was again increased, but hydrocarbon emissions and nitric oxide were added together to give motor manufacturers extra scope with their pollution control devices and in tuning their engines. Pollution regulations must be related to a standard driving pattern. Three major patterns have been defined for Europe, the USA and Japan. The ECE has indeed been criticized for its low speed profile (averaging 18.7 km/h). The distance is 1.01 km and a complete test comprises four cycles, the first being from cold. To ascertain the quantity of pollutants the vehicle are run on a chassis dynamometer to XXI the appropriate driving cycle and the polluteents from the exhaust are diluted and subsequently measured. As indicated above, it is usual for the ECE (Geneva) to recommend regulations and the Community to adopt them. This applied to regulations up to 15-04 (1984). However the European Community overtaked the ECE with Directive 88/76/EEC (often referred to as the Luxemburg Accord), based on engine size and not on vehicle weight; namely vehicles with engines (i) over 2 litres, (ii) between 1.4 and 2.0 litres, and (iii) below 1.4 litres. In the regulation EURO-93 is added an extra urban driving cycle emision result from which are in g/km not in g/test as previous regulation. In this situation in vehicles must be added catalitic coverters, because without them it is already imposible to meet the standards applying this regulation. This regulation is based on engine size, not on vehicle weight as previous regulation. From 1996 in Europian countries the regulation EURO-96 is in the use. From 1993 the regulation ECE. 15-04 was in use in our country Türkiye. Today from 1995 the regulation ECE. 15-04 is applied and measurments according to this standard are made in our laboratory. In the last chapter I analyzed the test results from a hudred vehicles below 3500 kg tested in accordance to the regulation ECE. 15-04 (Standards in Türkiye TS-4236 and TS-5648) taken in our laboratory. First I organized the vehicles information with the applications form of the firms importing them in individual folders. Then I displayed these informationns with calculated test results in the EXCEL program. After that I organized these data in separate tables in accordance of different charakteristics and test results of the vehicles. Finaly from various tables I obtained grphics which are suitable to make conclusions. Test results are in values and treds as theoretically expected and meet the standard ECE 15.04 ( TSE 4236 ).