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1

Effect of biodiesel on the development of split injection characteristics

Slavinskas Stasys, Labeckas Gvidonas, Mickevičius Tomas

Combustion Engines

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2019

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R. 58, nr 2

103--107

EN

The paper presents the experimental test results of a common rail injection system operating with biodiesel and the diesel fuel. The three fuel split injection strategies were implemented to investigate the effects made by biodiesel and a fossil diesel fuel on the history of injector inlet pressure and the injection rate. In addition, the three intervals between split injections and the different injection pressures were used to obtain more information about the studied subjects. The obtained results showed that the peak mass injection rates of the main injection phase were slightly higher when using biodiesel than the respective values measured with the normal diesel fuel. Because the first injection phase activated the fuel pressure fluctuations along the high-pressure line and in front of the injector, the time-span between injections has an impact on the injector inlet pressure and thus the fuel injection rate during the second injection phase. Since the nozzle closes little later for biodiesel, the injector inlet pressure also occurred latter in the cycle.

2

The influence of injection timing on the combustion characteristics for the heterogeneous combustion field using impinging injection

Kawakami T.

Journal of KONES

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2018

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Vol. 25, No. 3

283--288

EN

It is very important to achieve the low particulate and low emissions under high power operation conditions in practical industrial engine and turbine combustion. Several techniques for reducing the emissions have been proposed and a large amount of experimental data has been published. It is well known that the combustion field in practical industrial diesel engine are strongly influenced by the behaviour of injection, distribution of droplets and the premixed ratio of the combustion chamber. As the first step of this study, experiments have been carried out to examine the combustion characteristics of heterogeneous combustion field by using impinging injection and Split injection in a closed chamber. The combustion chamber is equipped with pintle type injection nozzles on each of the opposite walls along the length of the bomb. In this study, we call it “impinging injection” when the injection is performed at same time by two nozzles facing each other and “split injection” when the impinging injection is performed at two different timing. The main conclusions are as follows: 1) the most suitable conditions of injection timing exists for improving the maximum burning pressure and total burning time by using impinging injection; 2) the flame speed can be possible to control by using impinging injection timing from the ignition; 3) the heat release rate for Split injection is larger than that of standard impinging injection.

3

Numeryczna symulacja wpływu podziału dawki paliwa na jego rozpylenie w układzie wysokociśnieniowego wtrysku benzyny

Pielecha I., Maslennikov D., Czajka J., Wisłocki K.

Logistyka

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2011

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nr 6

PL

Artykuł dotyczy badań wtrysku benzyny w aspekcie wpływu czasu przerwy między kolejnymi dawkami paliwa na ich interakcje. Przeprowadzono badania zasięgu strugi paliwa z wtryskiem dwuczęściowym w różnych odstępach czasu, takich aby wtrysk kolejnej porcji paliwa swoim zasięgiem obejmował porcję pierwszą. W tym celu określono zasięg oraz powierzchnię zajmowaną przez strugi paliwa. Przeprowadzono analizę koncentracji paliwa w przekrojach strugi: pojedynczej oraz tzw. kumulowanej, wynikającej z wtrysku dodatkowej porcji paliwa. Badania przeprowadzono dla zróżnicowanych wartości: wielkości dawki paliwa, ciśnienia paliwa oraz odstępów czasowych między kolejnymi porcjami paliwa. Wykorzystanie metod optycznych pozwoliło na określenie mechanizmów działających w strudze paliwa podczas wtrysku wieloczęściowego.

EN

The experimental and numerical investigations of a multiple gasoline injection in the aspect of the influence of the injection dwell time on the interactions between the fuel doses have been discussed in the paper. The fuel spray penetration has been analyzed at a two-stage injection of different dwell times ensuring that the injection of the second fuel dose covered the area already occupied by the first one. To this end, the fuel spray penetration and area occupied by the spray were determined. The analysis of the fuel concentration in the fuel spray cross section has been performed (single and cumulative fuel spray the latter resulting from the overlapping injection of an additional fuel portion). The utilization of optical methods in the investigations allowed determining of the mechanisms governing inside the fuel spray during a multiple injection.

4

Split Injection Strategy for Diesel Sprays: Experiment and Modelling

Karimi K., Crua C., Heikal M. R., Sazhina E. M.

Silniki Spalinowe

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2007

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R. 46, nr SC2

181-191

EN

An experimental programme to characterise Diesel fuel sprays was conducted in a Proteus high-pressure rapid compression machine (RCM), at Sir Harry Ricardo Laboratories at University of Brighton. The Proteus experiments aimed to simulate realistic Diesel engine working conditions whilst allowing visualisation of in-cylinder processes by various optical and laser diagnostics techniques. The spray penetration was explored by laser diagnostics methods such as Laser Induced Fluorescence (LIF) and the Mie scattering techniques. High-speed video (HSV) images of the spray were also recorded to show the temporal evolution of the spray. Both liquid and vapour phases of the spray were captured by the LIF technique whilst Mie scattering only recorded the liquid part of the spray. In the current study, a 7-hole injector of the solenoid type was injecting 20mm³ of Diesel fuel each cycle at an injection pressure of 100MPa and in-cylinder pressures 2MPa and 6MPa. The fuel was injected in a split mode with various dwells between the 10mm³ + 10mm³ splits (or individual fuel injections). The instantaneous injection rate was measured by the long-tube rate technique. These data were taken as an input to the numerical model tracking the centre-of-mass (CoM) of the injected fuel. The modelling is based on the conservation of momentum of injected fuel mass in the presence of a realistic drag force acting on the whole spray as a physical body. This approach is particularly suitable for the dense sprays near the nozzle as an asymptotic case for the strong interaction between the spray droplets. Hence the CoM approach is seen as complementary to the traditional Lagrangian modelling for dispersed sprays widely employed by Computational Fluid Dynamics (CFD) codes. Air entrainment was modelled by the exponential decay of liquid fraction in the spray with a characteristic time τ. Under the conventional assumption of the conical shape of the spray, the penetration of spray tip was associated with the height of the cone. This allowed the calculation of the frontal area A required in the expression for the drag force. The numerical CoM model was validated against the experimental CoM data in the range of in-cylinder pressures and dwells between two consecutive injections (or splits). The following four cases were calculated and validated against the experimental data: in-cylinder pressures (ICP) 2MPa and 6MPa, split injection strategy with dwells 0.425ms and 0.625ms between injections. In all cases, the injection pressure was 100MPa; under cold intake conditions of ambient air. For validation purposes the image processing software was extended to characterise the position of the centre-of-mass of injected fuel. The ratio of tip penetration to the position of the centre-of-mass, β was assessed from LIF images for ICP = 2MPa and dwells 0.425ms and 0.625ms. An average value of the ratio with a corresponding standard deviation β =1.85 ± 0.3 was accepted for the validation of the model calculations versus experiment for all cases under consideration. An uncertainty corridor was constructed for the model validation against the HSV experiment. The corridor was formed by the curves corresponding to β = 2.15 and β =1.55 with the curve for β =1.85 in the middle. A good agreement was observed between the calculated and experimental CoM penetration. The same set of modelling parameters including spray dispersion time τ = 0.15ms was taken by the model for all the cases under consideration.