High Speed Shadowgraphy of Transparent Nozzles as an Evaluation Tool for In-Nozzle Cavitation Behavior of GDI Injectors

Gasoline Direct Injection (GDI) systems have become a rapidly developing technology taking up a considerableand rapidly growing share in the Gasoline Engine market due to the thermodynamic advantages of direct injection. The process of spray formation and propagation from a fuel injector is very crucial in optimizing the air-fuel mixture of DI engines. Previous studies have shown that the presence of some cavitation in high-pressure fuel nozzles can lead to better atomization of the fluid. However, under some very specific circumstances, high levels of cavitation can also delay the atomization process; spray stabilization due to hydraulic flip is the most well-known example. Therefore, a better understanding of cavitation behavior is of vital importance for further optimization of next generation fuel injectors.In contrast to the abundance of investigations conducted on the inner flow and cavitation patterns of diesel injectors, corresponding in-depth research on the inner flow of gasoline direct-injection nozzles is still relatively scarce. In this study, the results of an experiment performed on real-size GDI injector nozzles made of acrylic glass are presented. The inner flow of the nozzle is visualized using a high-power pulsed laser, a long-distance microscope and a high- speed camera. The ambiguity of dark areas on the images, which may represent cavitation regions as well as ambient air drawn into the nozzle holes, is resolved by injecting the fuel both into a fuel or gas filled environment. In addition, the influence of backpressure on the transient flow characteristics of the internal flow is investigated. In good agreement with observations made in previous studies, higher backpressure levels decrease the amount of cavitation inside the nozzles. Due to the high temporal and spatial resolution of the experiment, the transient cavitation behavior during the opening, quasi-steady and closing phases of the injector needle motion can be analyzed. For example, it is found that cavitation patterns oscillate with a characteristic frequency that depends on the backpressure. The link between cavitation and air drawn into the nozzle at the beginning of injection is alsorevealed.DOI: http://dx.doi.org/10.4995/ILASS2017.2017.4639

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Economy and emission characteristics of the optimal dilution strategy in lean combustion based on GDI gasoline engine equipped with prechamber

Advances in Mechanical Engineering ◽

10.1177/16878140211038100 ◽

2021 ◽

Vol 13 (12) ◽

pp. 168781402110381

Author(s):

Li Wang ◽

Zhaoming Huang ◽

Wang Tao ◽

Kai Shen ◽

Weiguo Chen

Keyword(s):

Fuel Economy ◽

Gasoline Engine ◽

Direct Injection ◽

Engine Performance ◽

Gasoline Direct Injection ◽

Dilution Ratio ◽

Lean Combustion ◽

Excess Air ◽

Combustion Phase ◽

Hc Emissions

EGR and excess-air dilution have been investigated in a 1.5 L four cylinders gasoline direct injection (GDI) turbocharged engine equipped with prechamber. The influences of the two different dilution technologies on the engine performance are explored. The results show that at 2400 rpm and 12 bar, EGR dilution can adopt more aggressive ignition advanced angle to achieve optimal combustion phasing. However, excess-air dilution has greater fuel economy than that of EGR dilution owing to larger in-cylinder polytropic exponent. As for prechamber, when dilution ratio is greater than 37.1%, the combustion phase is advanced, resulting in fuel economy improving. Meanwhile, only when the dilution ratio is under 36.2%, the HC emissions of excess-air dilution are lower than the original engine. With the increase of dilution ratio, the CO emissions decrease continuously. The NOX emissions of both dilution technologies are 11% of those of the original engine. Excess-air dilution has better fuel economy and very low CO emissions. EGR dilution can effectively reduce NOX emissions, but increase HC emissions. Compared with spark plug ignition, the pre chamber ignition has lower HC, CO emissions, and higher NO emissions. At part load, the pre-chamber ignition reduces NOX emissions to 49 ppm.

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Numerical Simulation of Transient Flow Inside Nozzle on Gasoline Direct Injection Engine

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.466-467.1237 ◽

2012 ◽

Vol 466-467 ◽

pp. 1237-1241

Author(s):

Yan Hua Wang ◽

Shi Chun Yang ◽

Yun Qing Li

Keyword(s):

Kinetic Energy ◽

Transient Flow ◽

Direct Injection ◽

Flow Characteristics ◽

Internal Flow ◽

Turbulence Kinetic Energy ◽

Gasoline Direct Injection ◽

Injection Hole ◽

Gasoline Direct Injection Engine ◽

Nozzle Configuration

To achieve transient flow characteristics at exit of nozzle orifice on gasoline direct injection engine, two phase Euler-Euler schemes was used to simulate the internal flow of the swirl nozzle. Different flow characteristics were calculated in the simulation. Different kinds of nozzle configuration were studied. Cavitaion and swirl flow occured in the nozzles. Injection hole configuration matters more than area variation of swirl tangential slot to discharge coefficient of the studied nozzle. Discharge coefficient changes a little along the injection hole length. The area of the swirl tangrntial slot plays an important throttling action in nozzle internal flow. Smaller area of swirl tangential slot generates larger degree cavitation but smaller mean injection velocity. Turbulence kinetic energy changes with the time of cavitation and swirl field occurring and the nozzle configuration. Before the appearance of cavitation, smaller inclination angle of orifice can generate more turbulence kinetic energy. After that moment, turbulence kinetic energy varies with different configuration. Along injection hole length, turbulence kinetic energy obviously varies. These flow characteristics affect primary atomization and will be as input for next spray simulation. They are also applied to design reference for injection nozzle.

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Predicting Cycle-to-Cycle Variation With Concurrent Cycles in a Gasoline Direct Injected Engine With Large Eddy Simulations

Volume 2: Emissions Control Systems; Instrumentation, Controls, and Hybrids; Numerical Simulation; Engine Design and Mechanical Development ◽

10.1115/icef2018-9722 ◽

2018 ◽

Cited By ~ 1

Author(s):

Daniel Probst ◽

Sameera Wijeyakulasuriya ◽

Eric Pomraning ◽

Janardhan Kodavasal ◽

Riccardo Scarcelli ◽

...

Keyword(s):

Gasoline Engine ◽

Direct Injection ◽

Engine Performance ◽

Turnaround Time ◽

Operating Conditions ◽

Gasoline Direct Injection ◽

Cycle Variation ◽

Spark Timing ◽

Large Eddy ◽

Operating Points

High cycle-to-cycle variation (CCV) is detrimental to engine performance, as it leads to poor combustion and high noise and vibration. In this work, CCV in a gasoline engine is studied using large eddy simulation (LES). The engine chosen as the basis of this work is a single-cylinder gasoline direct injection (GDI) research engine. Two stoichiometric part-load engine operating points (6 BMEP, 2000 RPM) were evaluated: a non-dilute (0% EGR) case and a dilute (18% EGR) case. The experimental data for both operating conditions had 500 cycles. The measured CCV in IMEP was 1.40% for the non-dilute case and 7.78% for the dilute case. To estimate CCV from simulation, perturbed concurrent cycles of engine simulations were compared to consecutively obtained engine cycles. The motivation behind this is that running consecutive cycles to estimate CCV is quite time-consuming. For example, running 100 consecutive cycles requires 2–3 months (on a typical cluster), however, by running concurrently one can potentially run all 100 cycles at the same time and reduce the overall turnaround time for 100 cycles to the time taken for a single cycle (2 days). The goal of this paper is to statistically determine if concurrent cycles, with a perturbation applied to each individual cycle at the start, can be representative of consecutively obtained cycles and accurately estimate CCV. 100 cycles were run for each case to obtain statistically valid results. The concurrent cycles began at different timings before the combustion event, with the motivation to identify the closest time before spark to minimize the run time. Only a single combustion cycle was run for each concurrent case. The calculated standard deviation of peak pressure and coefficient of variance (COV) of indicated mean effective pressure (IMEP) were compared between the consecutive and concurrent methods to quantify CCV. It was found that the concurrent method could be used to predict CCV with either a velocity or numerical perturbation. A large and small velocity perturbation were compared and both produced correct predictions, implying that the type of perturbation is not important to yield a valid realization. Starting the simulation too close to the combustion event, at intake valve close (IVC) or at spark timing, under-predicted the CCV. When concurrent simulations were initiated during or before the intake even, at start of injection (SOI) or earlier, distinct and valid realizations were obtained to accurately predict CCV for both operating points. By simulating CCV with concurrent cycles, the required wall clock time can be reduced from 2–3 months to 1–2 days. Additionally, the required core-hours can be reduced up to 41%, since only a portion of each cycle needs to be simulated.

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Numerical simulation of internal and near-nozzle flow of a gasoline direct injection fuel injector

Journal of Physics Conference Series ◽

10.1088/1742-6596/656/1/012100 ◽

2015 ◽

Vol 656 ◽

pp. 012100 ◽

Cited By ~ 8

Author(s):

Kaushik Saha ◽

Sibendu Som ◽

Michele Battistoni ◽

Yanheng Li ◽

Shaoping Quan ◽

...

Keyword(s):

Numerical Simulation ◽

Direct Injection ◽

Gasoline Direct Injection ◽

Nozzle Flow ◽

Fuel Injector

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Experimental and numerical analyses of the combustion process in a direct injection gasoline engine

International Journal of Engine Research ◽

10.1243/1468087001545100 ◽

2000 ◽

Vol 1 (2) ◽

pp. 147-161 ◽

Cited By ~ 4

Author(s):

J Reissing ◽

H Peters ◽

J. M. Kech ◽

U Spicher

Keyword(s):

Numerical Investigation ◽

Gasoline Engine ◽

Numerical Models ◽

Direct Injection ◽

Combustion Process ◽

Experimental Methods ◽

Spark Ignition Engine ◽

Gasoline Direct Injection ◽

Direct Injection Gasoline Engine ◽

Gdi Engines

Gasoline direct injection (GDI) spark ignition engine technology is advancing at a rapid rate. The development and optimization of GDI engines requires new experimental methods and numerical models to analyse the in-cylinder processes. Therefore the objective of this paper is to present numerical and experimental methods to analyse the combustion process in GDI engines. The numerical investigation of a four-stroke three-valve GDI engine was performed with the code KIVA-3V [1]. For the calculation of the turbulent combustion a model for partially premixed combustion, developed and implemented by Kech [4], was used. The results of the numerical investigation are compared to experimental results, obtained using an optical fibre technique in combination with spectroscopic temperature measurements under different engine conditions. This comparison shows good agreement in temporal progression of pressure. Both the numerical simulation and the experimental investigation predicted comparable combustion phenomena.

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Combustion Ionization for Detection of Misfire, Knock, and Sporadic Preignition in a Gasoline Direct Injection Engine

Journal of Energy Resources Technology ◽

10.1115/1.4043789 ◽

2019 ◽

Vol 141 (11) ◽

Cited By ~ 1

Author(s):

Samuel Ayad ◽

Swapnil Sharma ◽

Rohan Verma ◽

Naeim Henein

Keyword(s):

Pressure Transducer ◽

Direct Injection ◽

Operating Conditions ◽

Gasoline Direct Injection ◽

Ion Current ◽

Fuel Injector ◽

Direct Injection Engine ◽

Gasoline Direct Injection Engine ◽

Spark Plug ◽

Knock Sensor

Detection of combustion-related phenomena such as misfire, knock, and sporadic preignition is very important for the development of electronic controls needed for the gasoline direct injection engines to meet the production goals in power, fuel economy, and low emissions. This paper applies several types of combustion ionization sensors, and a pressure transducer that directly senses the in-cylinder combustion, and the knock sensor which is an accelerometer that detects the impact of combustion on engine structure vibration. Experimental investigations were conducted on a turbocharged four-cylinder gasoline direct injection engine under operating conditions that produce the above phenomena. One of the cylinders is instrumented with a piezo quartz pressure transducer, MSFI (multi-sensing fuel injector), a stand-alone ion current probe, and a spark plug applied to act as an ion current sensor. A comparison is made between the capabilities of the pressure transducer, ion current sensors, and the knock sensor in detecting the above phenomena. The signals from in-cylinder combustion sensors give more accurate information about combustion than the knock sensor. As far as the feasibility and cost of their application in production vehicles, the spark plug sensor and MSFI appear to be the most favorable, followed by the stand-alone mounted sensor which is an addition to the engine.

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Effect of Spark Timing on Performance of a Hydrogen Gasoline Engine

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.713-715.239 ◽

2015 ◽

Vol 713-715 ◽

pp. 239-242 ◽

Cited By ~ 1

Author(s):

Wei Bo Shi ◽

Xiu Min Yu ◽

Ping Sun

Keyword(s):

Gasoline Engine ◽

Direct Injection ◽

Engine Performance ◽

Spark Ignition Engine ◽

Gasoline Direct Injection ◽

Hydrogen Energy ◽

Energy Fraction ◽

Direct Injection Engine ◽

Excess Air ◽

Spark Timing

Hydrogen-gasoline blends is an effective way to improving the performance of spark ignition engine at stoichiometric and lean conditions. Spark timing is one of the important parameters affect the engine performance. This paper investigated the effect of spark timing on performance of a hydrogen-gasoline engine. A four cylinder, gasoline direct injection engine was modified to be a gasoline port injection, hydrogen direct injection engine. The hydrogen energy fraction was set as 0% and 30%. For a specified hydrogen addition, the engine was operated at four excess air ratios of 0.8, 1.0, 1.2 and 1.5. Under the specified excess air ratio condition, the spark timing was varied from 4 to 19°CA before top dead center (BTDC) with an interval of 3°CA. The test result showed that the indicated mean effective pressure (IMEP) climb up and then decline with the increase of spark advance. For hydrogen-gasoline engine, the optimum spark timing for the max IMEP was retarded at a specified excess air ratio. The max thermal efficiency appeared at the optimum spark timing.

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Modeling of Internal and Near-Nozzle Flow for a Gasoline Direct Injection Fuel Injector

Journal of Energy Resources Technology ◽

10.1115/1.4032979 ◽

2016 ◽

Vol 138 (5) ◽

Cited By ~ 8

Author(s):

Kaushik Saha ◽

Sibendu Som ◽

Michele Battistoni ◽

Yanheng Li ◽

Shaoping Quan ◽

...

Keyword(s):

Liquid Fuel ◽

Numerical Study ◽

Direct Injection ◽

Computational Cost ◽

Volume Averaging ◽

Operating Conditions ◽

Gasoline Direct Injection ◽

Superheated Liquid ◽

Fuel Injector ◽

Flash Boiling

A numerical study of two-phase flow inside the nozzle holes and the issuing spray jets for a multihole direct injection gasoline injector has been presented in this work. The injector geometry is representative of the Spray G nozzle, an eight-hole counterbore injector, from the engine combustion network (ECN). Simulations have been carried out for a fixed needle lift. The effects of turbulence, compressibility, and noncondensable gases have been considered in this work. Standard k–ε turbulence model has been used to model the turbulence. Homogeneous relaxation model (HRM) coupled with volume of fluid (VOF) approach has been utilized to capture the phase-change phenomena inside and outside the injector nozzle. Three different boundary conditions for the outlet domain have been imposed to examine nonflashing and evaporative, nonflashing and nonevaporative, and flashing conditions. Noticeable hole-to-hole variations have been observed in terms of mass flow rates for all the holes under all the operating conditions considered in this study. Inside the nozzle holes mild cavitationlike and in the near-nozzle region flash-boiling phenomena have been predicted when liquid fuel is subjected to superheated ambiance. Under favorable conditions, considerable flashing has been observed in the near-nozzle regions. An enormous volume is occupied by the gasoline vapor, formed by the flash boiling of superheated liquid fuel. Large outlet domain connecting the exits of the holes and the pressure outlet boundary appeared to be necessary leading to substantial computational cost. Volume-averaging instead of mass-averaging is observed to be more effective, especially for finer mesh resolutions.

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Effect of ultra-high injection pressure up to 50 MPa on macroscopic spray characteristics of a multi-hole gasoline direct injection injector fueled with ethanol

Proceedings of the Institution of Mechanical Engineers Part D Journal of Automobile Engineering ◽

10.1177/0954407017726720 ◽

2017 ◽

Vol 232 (8) ◽

pp. 1092-1104 ◽

Cited By ~ 6

Author(s):

Xiang Li ◽

Yi-qiang Pei ◽

Jing Qin ◽

Dan Zhang ◽

Kun Wang ◽

...

Keyword(s):

High Speed ◽

Direct Injection ◽

Cone Angle ◽

Injection Pressure ◽

Fuel Mixture ◽

Gasoline Direct Injection ◽

Spray Characteristics ◽

High Injection ◽

High Injection Pressure ◽

Wall Impingement

This research systematically studied the effect of injection pressure on macroscopic spray characteristics of a five-hole gasoline direct injection (GDI) injector fueled with ethanol, especially under ultra-high injection pressure up to 50 MPa. The front and side views of sprays were photographed by the schlieren method using a high-speed camera. Various parameters, including spray development stages, cone angle, penetration, area and irregular ratio, were fully analyzed to evaluate macroscopic characteristics of the whole spray and spray core with varying injection pressure. The results demonstrated that the effect of ultra-high injection pressure on macroscopic spray characteristics was significant. As injection pressure increased from 10 MPa to 50 MPa, the occurrence time of branch-like structure decreased; the cone angle increased little; the area increased significantly; the area ratio dropped by 6.4 and 5.8 percentage points on average for the front view and side view spray, respectively. There was a significant increase in the trend for penetration as the injection pressure rose from 10 MPa to 30 MPa. However, this trend became weak when the injection pressure further increased. The penetration ratio under ultra-high injection pressure was slightly higher than it was under 10 or 20 MPa. Ultra-high injection pressure would not obviously raise the possibility of spray/wall impingement, but led to the impingement quantity increasing to some extent. Increasing injection pressure could enhance the vortex scale, finally resulting in better air/fuel mixing quality. Ultra-high injection pressure was a potential way to improve air/fuel mixture homogeneity for a GDI injector fueled with ethanol.

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