Effects of intake flow on the spray structure of a multi-hole injector in a DISI engine

The spray characteristics of a 6-hole injector were examined in a single cylinder optical direct injection spark ignition engine. The effects of injection timing, in-cylinder charge motion, fuel injection pressure, and coolant temperature were investigated using the 2-dimensional Mie scattering technique. It was confirmed that the in-cylinder charge motion played a major role in the fuel spray distribution during the induction stroke while injection timing had to be carefully considered at high injection pressures during the compression stroke to prevent spray impingement on the piston

Influence of cavitation on near nozzle exit spray

The importance of cavitation inside multi-hole injectors for direct injection internal combustion (IC) engineshas been addressed in many previous investigations. Still, the effect of cavitation on jet spray, its stability and liquid breakup and atomisation is not yet fully understood. The current experimental work aims to address some of these issues. It focuses on the initiation and development of cavitation inside a 7x enlarged transparent model of a symmetric 6-hole spark ignition direct injection (SIDI) injector and quantifies the effect of cavitation on near-nozzle spray cone angle and stability utilising high speed Mie scattering visualisation. The regions studied include the full length of the nozzle and its exitjet spray wherethe primary breakup takes place

Actions for Vacuum Einstein's Equation with a Killing Symmetry

In a space-time $M$ with a Killing vector field $\xi^a$ which is either everywhere timelike or everywhere spacelike, the collection of all trajectories of $\xi^a$ gives a 3-dimension space $S$. Besides the symmetry-reduced action from that of Einstein-Hilbert, an alternative action of the fields on $S$ is also proposed, which gives the same fields equations as those reduced from the vacuum Einstein equation on $M$.Comment: 8 pages, the difference between the action we proposed and the symmetry-reduced action is clarifie

Internal flow and cavitation in a multi-hole injector for gasoline direct-injection engines

A transparent enlarged model of a six-hole injector used in the development of emerging gasoline direct-injection engines was manufactured with full optical access. The working fluid was water circulating through the injector nozzle under steady-state flow conditions at different flow rates, pressures and needle positions. Simultaneous matching of the Reynolds and cavitation numbers has allowed direct comparison between the cavitation regimes present in real-size and enlarged nozzles. The experimental results from the model injector, as part of a research programme into second-generation direct-injection spark-ignition engines, are presented and discussed. The main objective of this investigation was to characterise the cavitation process in the sac volume and nozzle holes under different operating conditions. This has been achieved by visualizing the nozzle cavitation structures in two planes simultaneously using two synchronised high-speed cameras. Imaging of the flow inside the injector nozzle identified the formation of three different types of cavitation as a function of the cavitation number, CN. The first is needle cavitation, formed randomly at low CN (0.5-0.7) in the vicinity of the needle, which penetrates into the opposite hole when it is fully developed. The second is the well known geometric cavitation originating at the entrance of the nozzle hole due to the local pressure drop induced by the nozzle inlet hole geometry with its onset at around CN=0.75. Finally, and at the same time as the onset of geometric cavitation, string type cavitation can be formed inside the nozzle sac and hole volume having a strong swirl component as a result of the large vortical flow structures present there; these become stronger with increasing CN. Its link with geometric cavitation creates a very complex two-phase flow structure in the nozzle holes which seems to be responsible for hole-to-hole and cycle-to-cycle spray variations

Internal flow and spray characteristics of a pintle-type outward opening piezo-injector

The near nozzle exit flow and spray structure generated by an enlarged model of a second generation pintle type outwards opening injector have been investigated under steady flow conditions as a function of flow-rate and needle lift. A high resolution CCD camera and high-speed video camera have been employed in this study to obtain high-magnification images of the internal nozzle exit flow in order to identify the origin of string ligaments/droplets formation at the nozzle exit. The images of the flow around the nozzle seat area showed clearly that air was entrained from outside into the nozzle seat area under certain flow operating conditions (low cavitation number, CN); the formed air pockets inside the annular nozzle proved to be the main cause of the breaking of the fuel liquid film into strings as it emerged from the nozzle with a structure consisting of alternating thin and thick liquid filaments. As the flow rate increased, the air pockets were suppressed, reduced in size and pushed towards the exit of the nozzle resulting in a smoother spray. The results showed that the number of strings increased linearly, within the measured range, with liquid exit velocity and that the spray cone angle was smaller or larger than the nominal value depending on the attachment of air pockets to the cartridge or needle surfaces, respectively; these two distinct small and large cone angles were found to be dominant at low and high lifts. Increasing the flow rate further so that CN exceeds the critical value, gave rise to pockets of vapour that started to emerge in the nozzle seat region and disintegrated rapidly as they were convected towards the nozzle exit. The analysis of the near nozzle flow visualizations has shown the existence of air entrainment and cavitation as two different phenomena occurring under different operating condition

Link between in-nozzle cavitation and jet spray in a gasoline multi-hole injector

The importance of cavitation inside multi-hole injectors has been addressed in many previous investigations where the cavitation formation and its development, fuel spray characteristics and atomisation have quantified. Different types of geometrical and vortex cavitations have been previously reported inside the nozzles of multi-hole injectors with good indication of their influences on the emerging spray. However, the effect of cavitation on jet spray, its stability and liquid breakup and atomisation is not yet fully understood. The current research work is aimed to address some of the above issues. As the initial phase, the current experimental work focuses on the initiation and development of different type of cavitation inside a 15-times enlarged model of a symmetric 6-hole SIDI injector and tries to quantify the effects of the cavitation on the near nozzle jet spray in terms of jet cone angle and its stability. To achieve this, a high speed camera has been used to visualise the innozzle flow and emerging spray simultaneously

Effects of intake flow and coolant temperature on the spatial fuel distribution in a direct-injection gasoline engine by PLIF technique

The spatial fuel distributions of the homogeneous and stratified charge of a high pressure 6-hole injector were examined in a single cylinder optical direct injection spark ignition (DISI) engine. The effects of in-cylinder charge motion, fuel injection pressure and coolant temperature were investigated using a planar laser induced fluorescence (PLIF) technique. It was found that in the case of homogeneous charge mode, early injection in the intake stroke generated similar fuel distributions at the crank angle of 12° BTDC regardless of the in-cylinder air motion at the coolant temperature of 90 °C. In the case of stratified charge mode, the in-cylinder tumble flow played more effective role in mixture preparation than the swirl flow during the compression stroke; and the increase of the coolant temperature improved fuel evaporation; but the increase of the fuel supplying pressure could not change the pattern of the fuel vapour distribution against the expectation

PIV Investigation on Flows Induced by Fuel Sprays from an Outwards Opening Pintle Injector for GDI engines

Pintle-type outwards opening injectors actuated by piezoelectric technique have demonstrated the ability to meet the challenging requirements in spray-guided gasoline direct injection engines. Previous studies carried out by spray visualisation showed that the spray had a stable spray cone angle against elevated in-cylinder back pressures, which have been be determined by the integral spray images using continuous or flash white light illumination. However the fuel cloud structure at the end of injection was not well defined when the injection was completed in the white light Mie scattering visualisation. In order to show the details of the spray cloud structure, two dimensional flow visualisation illuminated by a laser sheet was used under the atmospheric condition. The results showed complex multiple vortices forming a recirculation zone inside the fuel cloud. To further study the structure of such vortices, a double pulsed laser sheet illumination was employed to obtain the instantaneous velocity fields of fuel droplets using the Particle Image Velocimetry (PIV) technique. The PIV system was also used to study air motion induced by the spray near the injector nozzle; a good agreement was found in the air entrainment velocities when compared to the LDV measurements

Extended mixed integer quadratic programming for simultaneous distributed generation location and network reconfiguration

Introduction. To minimise power loss, maintain the voltage within the acceptable range, and improve power quality in power distribution networks, reconfiguration and optimal distributed generation placement are presented. Power flow analysis and advanced optimization techniques that can handle significant combinatorial problems must be used in distribution network reconfiguration investigations. The optimization approach to be used depends on the size of the distribution network. Our methodology simultaneously addresses two nonlinear discrete optimization problems to construct an intelligent algorithm to identify the best solution. The proposed work is novel in that it the Extended Mixed-Integer Quadratic Programming (EMIQP) technique, a deterministic approach for determining the topology that will effectively minimize power losses in the distribution system by strategically sizing and positioning Distributed Generation (DG) while taking network reconfiguration into account. Using an efficient Quadratic Mixed Integer Programming (QMIP) solver (IBM ®), the resulting optimization problem has a quadratic form. To ascertain the range and impact of various variables, our methodology outperforms cutting-edge algorithms described in the literature in terms of the obtained power loss reduction, according to extensive numerical validation carried out on typical IEEE 33- and 69-bus systems at three different load factors. Practical value. Examining the effectiveness of concurrent reconfiguration and DG allocation versus sole reconfiguration is done using test cases. According to the findings, network reconfiguration along with the installation of a distributed generator in the proper location, at the proper size, with the proper loss level, and with a higher profile, is effective.  Вступ. Для мінімізації втрат потужності, підтримки напруги в допустимому діапазоні та покращення якості електроенергії у розподільчих мережах представлена реконфігурація та оптимальне розміщення розподіленої генерації. При дослідженнях реконфігурації розподільної мережі необхідно використовувати аналіз потоку потужності та передові методи оптимізації, які можуть вирішувати серйозні комбінаторні проблеми. Підхід до оптимізації, що використовується, залежить від розміру розподільної мережі. Наша методологія одночасно вирішує дві задачі нелінійної дискретної оптимізації, щоби побудувати інтелектуальний алгоритм для визначення найкращого рішення. Пропонована робота є новою, оскільки вона використовує метод розширеного змішано-цілочисельного квадратичного програмування (EMIQP), детермінований підхід до визначення топології, що ефективно мінімізує втрати потужності в системі розподілу за рахунок стратегічного визначення розмірів та позиціонування розподіленої генерації (DG) з урахуванням реконфігурації мережі. При використанні ефективного солвера Quadratic Mixed Integer Programming (QMIP) (IBM®) результуюча задача оптимізації має квадратичну форму. Щоб з'ясувати діапазон та вплив різних змінних, наша методологія перевершує передові алгоритми, описані в літературі, з точки зору одержаного зниження втрат потужності, згідно з великою числовою перевіркою, проведеною на типових системах з шинами IEEE 33 і 69 при трьох різних коефіцієнтах навантаження. Практична цінність. Вивчення ефективності одночасної реконфігурації та розподілу DG у порівнянні з єдиною реконфігурацією проводиться з використанням тестових прикладів. Відповідно до результатів, реконфігурація мережі разом із установкою розподіленого генератора в потрібному місці, належного розміру, з належним рівнем втрат і з більш високим профілем є ефективною

Simulation of Acoustic Black Hole in a Laval Nozzle

A numerical simulation of fluid flows in a Laval nozzle is performed to observe formations of acoustic black holes and the classical counterpart to Hawking radiation under a realistic setting of the laboratory experiment. We determined the Hawking temperature of the acoustic black hole from obtained numerical data. Some noteworthy points in analyzing the experimental data are clarified through our numerical simulation.Comment: 26 pages, published versio