Comparative studies of exhaust emission from diesel engine fuelled with diesel fuel and B 100 fuel

The article presents a comparative study of carbon monoxide, hydrocarbons, nitrogen oxides and the mass and number of particulate of diesel engine fulled with diesel and B100. B100 is a biofuel produced from vegetable oils for vehicles with compression-ignition engines. B100 fuel and diesel have similar physical-chemical characteristics which have been analyzed. The research was carried out on an engine dynamometer in four cycles: ESC, ETC, WHSC and WHTC. The article provides an analysis of the research results, preceded by a discussion of the test cycles used.


Introduction
With air pollution and increasingly restrictive requirements concerning the emission of harmful combustion substances, it is crucial to search for and use fuels from sources other than crude oil, including renewable sources, oilseeds, e.g.rape seed oil.Given the above, the self-ignition engine is suitable as it demonstrates a relatively low sensitivity to changes of fuel's physical & chemical properties.
Modern-day SI engines adapted to combust fuels derived from crude oils cannot be powered with natural rape seed oil due to problems relating to the immobilization of pressure elements, carbonisation of sprays, the occurrence of varnish in the combustion chamber and poorer lubricity properties of the engine oil [1,10].
The content of glycerides in natural rape-seed oil accounts on average for 95-98%.Glycerides together with natural substances soluble in fat form a group of compounds known as lipids [2].Large and heavy particles of rape-seed oil can be decreased by way of transesterification.
Noteworthy results of the transesterification of natural rape-seed oil include considerable decrease of particles and significant reduction of viscosity (up to 10 times), the elimination of triglycerides (and thus reducing the varnish in the combustion chamber), as well as decrease of the cloud and solidification point and improved fuel volatility [1,10].B100 (methyl esters of fatty acids) is a biofuel produced in the country based on vegetable oils, intended for vehicles with SI engines.
The offered biofuel has a beneficial effect on the operation and durability of the engine; owing to good lubricity properties it protects the injection elements against excessive wear [5].Greater content of oxygen compared to traditional diesel fuel manifests in "better" combustion, while a high cetane number ensures good engine performance.B100 biofuel meets the quality standards set forth bio-diesel according to PN-EN 14214 standard applicable on EU markets [7,10].Because of lowtemperature characteristics (CFPP), there are three types of B100 biofuel: B, D and F (corresponding to fuels of temperate climate zones) and class 2 -corresponding to the fuel for arctic or harsh winter climate [12]: − B100 type B with CFPP no greater than 0 o C, − B100 type D with CFPP no greater than -10 o C, − B100 type F with CFPP no greater than -20 o C.
The last fuel continued to be available and was subject to evaluation, and its use in comparative studies covering commercial diesel fuel, in tests of IVECO engine allowed for comparing the emission of polluting combustion substances in the use of both fuels.

The purpose and scope of research
The purpose of the research was to perform comparative tests of emission of polluting combustion gases from a CI engine IVECO N60 ENT C, fuelled with diesel and B100 biofuel, in ESC, ETC, WHSC and WHTC cycles.The starting point for the tests was to define the advantages of using environmentally-friendly B100 biofuel in terms of emission of polluting combustion gases compared to conventional diesel fuel used in the same engine.

The tested objects
The tests comprised commercial diesel fuel and B100 fuel in N60 ENT C engine by IVECO.
The parameters of the tested fuels are presented in Table 1 (for diesel fuel) and in Table 2 (for B100 fuel).The basic technical data of IVECO N60 ENT C engine are presented in Table 3, whereas the view of the engine installed in the testing unit is shown in Fig. 1.

Testing unit
The tests were conducted in the Motor Transport Institute in a testing unit equipped with an engine test bench, consisting of (Fig. 2, Fig. 3

Measuring cycles
The studies of emission of combustion pollutants generated by IVECO N60 ENTC engine fuelled with diesel and B100 were carried out with the engine test bench.The tests were performed in four cycles: ESC, ETC and WHSC and WHTC (Fig. 4, Fig. 5, Fig. 6, Fig. 7).However, Review 06 describing the approval tests for engines with a bi-fuel system applies to engines that fulfil the limit of Euro VI requirements, thus engines tested in completely different cycles than Euro V engines.Euro V engines were tested in ESC and ETC cycles, whereas Euro VI engines are tested in WHSC and WHTC cycles.
Due to the above reasons, this study -which aimed at comparing the emissions of pollutants generated by the engine when fuelled with diesel and B100 compliant with Euro V regulations, in its basic versions fuelled with diesel -was based on methods described in Directive 2005/55/EC [4] and UN Vehicle Regulations -Rev.05, making only necessary adjustments in the bi-fuel engine calculations, in accordance with UN Vehicle Regulations -Rev.06, where required.
The tests were carried out in ESC, ETC in accordance with Directive 2005/55/EC, with the use of two different types of fuel.In the first case the engine was fuelled with diesel only, whereas in the second case with B100.

Analysis of test results
Table 4 presents results of tests of emission of combustion pollutants in the tested engine fuelled with diesel and B100, in different testing cycles applied in engine approval tests.According to Table 4 and Fig. 8 the unit emission of CO is lower when B100 fuel is used, compared to diesel fuel, in all test cycles.
THC emissions are practically analogous in ESC, ETC, WHSC and WHTC cycles when the engine is fuelled with diesel and B100, except for WHTC Cold, where the emission for diesel fuel is definitely greater (Fig. 9).
The level of particulate matter is clearly lower in ESC, ETC, WHSC and WHTC Cold cycles when fuelled with B100, except for WHTC (Fig. 11).The unit emission of NOx is clearly greater in ESC, ETC, WHSC and WHTC cycles when fuelled with B100, except for WHTC Cold (Fig. 10).

Summary
The tests lead to the following conclusions: − the use of B100 to fuel a combustion engine in general has a positive impact on PM emission levels; − the tendency to a lower emission is also noticeable in case of carbon oxide (CO) and to a lesser degree -also in the case of hydrocarbons (THC); − the use of B100 to fuel a combustion CI engine affects the emission of nitrogen oxides (NOx); − respective test cycles differ considerably in terms of emission levels with regard to all harmful substances.

Fig. 1 .
Fig. 1.IVECO N60 ENTC engine installed in the testing unit ): − an asynchronous electrical machine (capable of operating as an engine-generator) of AVL type AFA 100 4Z4/4 with a current frequency transformer; the unit allows for recreating dynamic tests and can be used for measuring the emission of combustion pollutants in line with the regulations currently in force; − a digital rotation speed metering device Heidenham ROD 426 1024 27S12-03, − a torque measuring shaft T10F 063230022 HBM installed on the shaft linking the engine with the brakes, which allows to eliminate -in dynamic position of the engine's operation -the impact of breakaway torque of the brake's rotor on temporary torque developed by the engine; − a flow meter to measure fuel consumption -AVL 735, compatible with AVL 753, ensuring constancy of fuel's temperature during the measurement; − a set of combustion analysers AMA i60 adapted to analyse undiluted combustions, consisting of a double set of analysers to gauge emission before and behind the combustion purification unit; − an air flow-meter Sensyflow P to measure air consumption in the engine, effected by measuring the resistance of the heated wire; − a set of thermometers and manometers to measure temperature and pressure of various media inside the engine (air, oil, coolant and combustion gases).

Fig. 8 .
Fig. 8.Comparison of CO emission in an engine fuelled with diesel and B100, depending on the type of test

Fig. 10 .
Fig. 10.Comparison of NOx emission with engine fuelled by diesel and B100, depending on the type of test

Table 4 .
Emission test results in different cycles[g/kWh] The lowest emissions have been achieved in ESC cycle and tend to increase in ETC, WHSC, WHTC and WHTC Cold cycles.