Wyniki wyszukiwania - BazTech

1

The control of the course of combustion in a DI SI engine through matching of the multiple injection strategy

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

Silniki Spalinowe

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2011

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R. 50, nr 3

EN

The paper presents the results of the investigations of the dependence of the basic energy related indexes of the engine process on the strategy of direct multiple fuel injection. The tests were performed on a model engine - a Rapid Compression Machine. In the subsequent measuring cycles the injection strategy control (number of injected fuel doses, their size and dwell times) was modified. The courses of the combustion were observed through optical access and the possibility of recording of individual images of high spatial and time resolution. While processing the footage the velocity of flame formation and its development were determined as well as the main conditions of the flame propagation. Additionally, based on the observations and analysis of the spectral luminance distribution performed through a two-color method the temperature distribution was determined in the flame area. The investigations were performed for different injection strategies (multiple injection). It has been observed that the division of the injected fuel dose leads to the process of combustion, reduction of its duration and a reduction of the maximum flame temperatures. The fuel dose division is advantageous for the improvement of the efficiency of the oxidation process at lower temperatures approximating the phenomenon of low temperature combustion).

PL

W pracy przedstawiono wyniki badania zależności podstawowych wskaźników energetycznych procesu silnikowego od strategii sterowania bezpośrednim wtryskiem wieloczęściowym. Badania przeprowadzono na silniku modelowym, tzw. Maszynie Pojedynczego Cyklu. W kolejnych cyklach pomiarowych zmieniano strategię sterowania określoną przez liczbę wtryskiwanych dawek częściowych, ich wielkość oraz czasy między nimi. Przebiegi procesu spalania obserwowano wykorzystując dostęp optyczny do komory spalania i możliwość rejestracji poszczególnych obrazów z dużą rozdzielczością czasową i przestrzenną. W trakcie obróbki materiału filmowego określano prędkość powstawania i rozwoju płomienia oraz główne kierunki jego propagacji. Dodatkowo, na podstawie obserwacji i analizy spektralnego rozkładu luminancji przeprowadzonej z zastosowaniem metody dwubarwowej określano rozkład temperatury w obszarze płomienia. Badania zrealizowania dla różnych strategii wtrysku (wtrysk wielofazowy). Stwierdzono, że podział dawki wtryskiwanego paliwa prowadzi do procesu spalania, skrócenia jego czasu i zmniejszenia maksymalnych temperatur płomienia. Podział dawki sprzyja więc poprawie skuteczności procesu utleniania przy niższych temperaturach, zbliżając proces do tzw. spalania niskotemperaturowego.

2

Ocena możliwości pomiaru przebiegu i dawki wtrysku za pomocą indykatora z komorą o powiększonej objętości

Knefel T.

Pomiary Automatyka Kontrola

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2010

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R. 56, nr 3

229-232

PL

Artykuł jest poświęcony pomiarom: natężenia wypływu paliwa z rozpylacza oraz dawki, podawanych przez wtryskiwacz silnika o zapłonie samoczynnym. Oceniono możliwości wyznaczania przebiegu wtrysku pojedynczej i dzielonej dawki przy wtrysku do komory indykatora o powiększonej objętości. W pomiarach wykorzystano wtryskiwacz samochodu ciężarowego średniej ładowności. Przy ocenie wyników przyjęto, że różnice między wartościami zmierzonymi a obliczonymi nie powinny przekraczać š 4%. Tak wyznaczony zakres stosowania indykatora obejmuje dawki o objętościach od 10 do ok. 52 mm3/wtrysk. Poza nim występują przypadki objęte dopuszczalnym przedziałem błędu, jednak istnieje prawdopodobieństwo wystąpienia pomiarów, których wynik nie będzie się mieścił w przyjętym przedziale.

EN

The paper deals with measurements of the fuel dose and injection rate for a diesel engine injector. Possibility of measuring the single and multiple fuel injection rate was estimated. The investigations were performed for an electromagnetic common rail injector during fuel injection to the indicator chamber of enlarged volume. Such injectors are usually used in engines of medium carrying capacity trucks. The amplified pressure signal from the indicator was recorded by means of a digital oscilloscope. The equation for calculation of the injection rate results from the mass conservation law (2). For each measurement point (Tab. 1) the relative difference between the injection dose measured and calculated was determined (3) (Figs. 4, 6 and 10) for both single and multiple injection. The relative approximation errors were determined, too (Figs. 1 and 2). Comparison of the measured and calculated injection dose as a function of the rail pressure for both single and multiple injection is presented in Figs. 3 and 5. Fig. 7 shows the measured and calculated injection dose as a function of the dwell time for multiple injection. It was assumed that the differences between the measured and calculated values should not exceed š 4%. Hence, the indicator should be used within the range of fuel supply from 10 for 52 mm3/cycle. Outside the assumed range, the error can be less than or equal to š 4%, but it also it can be greater.

3

Określanie rzeczywistych czasów wtrysku dzielonej dawki w silniku o zapłonie samoczynnym

Knefel T.

Silniki Spalinowe

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2009

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R. 48, SC2

386--391

PL

W pracy wyznaczono różnice między zadanymi i realizowanymi czasami wtrysku oraz czasy opóźnienia pomiędzy początkiem/końcem sygnału sterującego, a otwarciem/zamknięciem wtryskiwacza dla dzielonej dawki wtrysku. Dla stałych wartości zadanego czasu otwarcia wtryskiwacza wyznaczono rzeczywiste czasy wypływu paliwa z rozpylacza. Pomiary przeprowadzono dla różnych wartości ciśnień paliwa w zasobniku i różnych wielkości dawek wtrysku.

EN

In the paper the difference between the requested and implemented injection delay time between the onset/end of signal and the opening/closing of the injector for the divided injection dose were presented. For fixed values of the time allocated to actual injector opening set the real time flow of fuel spray. The measurements were carried out for different values of fuel pressure in the rail and different values of injection doses.

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.