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1

NOx emission using biodiesel

100%

Kegl B.

Journal of KONES

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2006

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tom Vol. 13, No. 4

497-506

EN

Most investigations show that the use of biodiesel results in lower emissions of HC, CO and smoke whereas the emission of NOx increases. For this reason attention in this paper is focused on the possibility to reduce NOx emission when using biodiesel fuel. The experiments are performed on an NA diesel bus engine with direct injection M system. The tested fuels are mineral diesel and domestic biodiesel fuel produced from rapeseed. At first the influences of different fuels on NOx emission are investigated. The analysis of experimentally obtained results is performed at different engine operating regimes with the injection timing prescribed by the engine producer for mineral diesel fuel. The NOx emissions and other engine characteristics with biodiesel are compared against those obtained using mineral diesel. In this way the influences of fuel properties on engine harmful emissions, specific fuel consumption, brake thermal efficiency and engine power are investigated. Furthermore the possibility for reduction of NOx emission without expensive engine modifications is investigated. Keeping this in mind, the optimal injection pump timing is determined. The experimental results show that the retarded injection pump timing is necessary when using biodiesel in order to reduce harmful NOx emission without worsening other engine characteristics. During the experiments, the engine was monitored for possible operation problems and carefully examined after the tests.

2

Optimal design of the intake system

63%

Pogorevc P. , Kegl B.

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tom Vol. 10, No. 1-2

213-219

EN

The intake system geometry of the internal combustion engine has a major effect on the gas exchange process. Therefore it affects the performance of the engine and its emissions. In order to improve engine performance, it must assure uniform distribution of fresh air among the cylinders and minimal pressure losses along the channels. The optimisation of the intake systems is of an interest to the engine designers sińce the beginning of the 20th century. The paper deals with the optimal design of the intake system for the four-stroke four-valve internal combustion engine with the intention of increasing its power. Special geometry demands and constraints had to be taken into consideration. Optimisation was carried out using the optimisation program iGO based on a gradient-based approximation method. For the response calculation the computational fluid dynamics program BOOST was used. The connection between iGO and BOOST was established by simple wrapper programs that took car e for the correct data exchange. The results comparison confirmed the adequacy of the program BOOST in our example.

3

Design of intake system with special demands

63%

Pogorevc P. , Kegl B.

Journal of KONES

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2002

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tom Vol. 9, No. 1-2

217-224

EN

The intake system provides the internal combustion engine with fresh air and it has a major effect on engine performance and emissions. Therefore great attention has to be focused on the design of the intake system. Many investigations are related to the improvement of the breathing capacity of the engine, to the minimization of pressure losses along the pipes and to the distribution uniformity of air among the cylinders of the engine. This paper deals with the design of the intake system of the racing car engine with special demands. The imposed constraint is a single circular restrictor in the intake system, positioned between the throttle and the engine. All engine airflow passes through this restrictor of 20 mm diameter for gasoline-fuelled cars. The only allowed sequence consists of a throttle, restrictor and engine. Keeping these requires in mind, the flow and pressure loss reduction in the engine intake region are investigated with computational fluid dynamics software. On the basis of numerically obtained results, the intake system is designed and practically manufactured in our racing car engine.

4

Experimental and numerical analysis of fuel flow in the diesel engine injection nozzle

63%

Volmajer M. , Kegl B.

Journal of KONES

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2001

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tom Vol. 8, No. 1-2

9-16

EN

The geometry of the diesel fuel injection nozzle and fuel flow characteristics in the nozzle significantly affects the processes of fuel atomisation, combustion and formation of pollutants emissions in a diesel engine. In this paper numerical and experimental results of the nozzle fuel flow analysis for a four-hole injection nozzle Bosch DLLA 148 S 311376 are presented. To describe the nozzle fuel flow, a three-dimensional computational fluid dynamics (CFD) model is employed. The CFD package FIRE (AVL Graz) is used for computation. The results represent the fuel flow characteristics for steady state flow conditions at different needle opening. For this purpose several three-dimensional models representing different needle lifts are made. The experimental results are obtained by measuring the fuel flow coefficients at steady state conditions on the nozzle flow tester made in Engine research laboratory (ERL) at the Faculty of mechanical engineering in Maribor. The fuel injection pump is driven by an electric motor, the pressure control valve regulates the pressure at 100 bar and the calibration fluid is injected through the nozzle into the measuring Plexiglas cylinder. The fuel flow coefficients obtained from the experimental results at steady flow conditions in the nozzle are compared with the results of the CFD analysis.

5

Analysing in-nozzle flows using partial nozzle models

63%

Volmajer M. , Kegl B.

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tom Vol. 10, No. 1-2

289--296

EN

The geometry of the diesel fuel injection nozzle and fuel flow characteristics in the nozzle significantly affects the processes of fuel atomisation, combustion and formation of pollutant emissions in a diesel engine. To improve the processes of fuel injection and spray formation CFD packages are commonly used. Since CPU times are often high, partial models are used for analysis. The results of the analysis by using partial models are model dependent, so the differences between the results using different models can occur. In this paper CFD analysis for different partial models of a 4-hole nozzle were made. The objective of the research was to find the proper model to be used for fast analysis of existing nozzle geometry. Several partial models of the nozzle were made. The results were compared with the results of measurements at steady state conditions.

6

Cavitation phenomena in the injection nozzle: theoretical and numerical analysis

63%

Volmajer M. , Kegl B.

Journal of KONES

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2004

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tom Vol. 11, No. 3-4

295-303

7

Intake and exhaust influence on engine performance

63%

Pogorevc P. , Kegl B.

Journal of KONES

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2004

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tom Vol. 11, No. 3-4

125-132

EN

The intake and exhaust system shapes are very important factors in the gas exchange process of the combustion engines. That's why many investigations are related to the improvement of their geometry in order to maximize engine's performances or lower its emission values of the exhaust. Modern approach in such researches means use of numerical simulation codes, which give us individual geometry of several engine parts. the production of numerically improved part, they must be tested and evaluated with the experiments. The paper deals with the influence of the intake and the exhaust characteristic (diameters, lengths, shapes) on engine power, fuel consumption and emissions. The optimisation procedure together with the optimized measurements for the intake and the exhaust are also shown. For the simulations the AVL's program BOOST was used. It proved to be accurate enough for the four-stroke internal combustion engines in the course of our previous work

8

Injection characteristics of an in-line fuel injection system using the alternative fuels

51%

Volmajer M. , Kegl B. , Pogorevc P.

Journal of KONES

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2002

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tom Vol. 9, No. 1-2

259-267

EN

The ever increasing ecological requirements encourage the use of alternative fuels. Some alternative fuels have advantages in production, some in transport and some in excellent injection as well as engine characteristics. Till today several alternative fuels for compression ignition engines have been investigated. This paper deals with the bio-diesel and with the wasted cooking oil. Biodiesel is produced from different plants (rape, Canola, Soya beans, palm tree...), while the wasted cooking oil is received from the catering industry. In this paper attention is focused on the fuel injection as well as fuel spray characteristics using diesel, bio-diesel and wasted cooking oil. The analysis of the fuel injection characteristics is obtained using the one-dimensional mathematical model for numerical simulation of injection process. In this model the influence of the snubber valve, the cavitation phenomena as well as variable fuel properties are taken into account. The influence of alternative fuels on spray characteristics is investigated using some empirical models. Furthermore, a computational fluid dynamics package is used for some analyses of the nozzle flow characteristics. Finally, on the basis of the numerically and experimentally obtained results, the harmful emissions using alternative fuels are predicted to some extent.

9

Analysing the cavitation phenomena in in-nozzle flows

51%

Vajda B. , Žunič Z. , Kegl B.

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tom Vol. 17, No. 2

475-482

EN

The geometry of the diesel fuel injection nozzle and fuel flow characteristics in the nozzle significantly affects the processes of fuel atomization, combustion and formation of pollutant emissions in diesel engine. To improve the process of fuel injection, CFD packages are used. Since CPU times are often high, partial models are used for the analysis. In presented paper the influence ,of different density of mesh on the cavitation phenomena is being analysed. The theoretical backgrounds of the cavitation occurrence presented in the first part of the paper are followed by the numerical analyses of two-phase flow in same simplified nozzle models. The numerical analyses are made using computation fluid dynamic (CFD) program Fire. The numerical analysis is made for two different types of fluid, diesel (D2) and biodiesel (B 100). Numerical analysis also includes various densities of meshes and their influence on results. The two-phase flow is analysed using a two-equation approach, where all conservation equations are solved for every phase. Numerical analysis results are compared to the experimental observations of the two-phase flow available from the literature. The results are compared for various meshes and various fluid types. The results show that higher pressure yields mode cavitation and point out the importance of mesh densities.