Multi-hole Injector Research Articles

The development of a data acquisition system for measuring the injection rate of a multihole diesel injector

In this research, two types of sensors systems (an ‘amplifier integrated sensor with a fixed measuring range’ and an ‘amplifier-sensor setup with adjustable measuring range’) are analyzed and compared with each other. From experimental results obtained simultaneously from the nozzle holes, the two sensors reliability and robustness were analyzed with regards to injection rate and cycle fuel injection quantity. Afterwards, series of different experiments were conducted using an eight holed nozzle to determine the limits or the degree of freedom within which experimental results could be deemed reliable. From the analysis, and with reference to conventional standards, the new sensor (amplifier-sensor setup with adjustable measuring range) performed better with relatively wider application limits. Also the new sensor-system setup measurement accuracy, was studied experimentally with the aid of a common-rail pump test bench, where the influence of sensor target distance and sensor target-axis angles on the measured result were determined. Sensor target distance of not more than 15mm and sensor target-axis angle within 90°±5° (85°–95°) range were the optimum settings determine to ensure reliable measurements. Validation of cycle fuel injection quantities from each nozzle hole of the eight hole nozzle was performed with the aid of an EFS injection flow meter. This research presents insight into the effective data acquisition from multihole injectors, which is essential due to the increasing popularity of multihole injectors used in internal combustion (IC) engine nowadays.

Generalizing the behavior of flash-boiling, plume interaction and spray collapse for multi-hole, direct injection

This paper presents an experimental and modeling study of direct fuel injection in a constant volume chamber (CVC). Iso-octane and propane are used as surrogates for gasoline and liquefied petroleum gas (LPG) respectively, and are injected over a wide range of conditions that are relevant to modern, spark ignition engines.Optical imaging of the liquid and vapor phases are first used to examine these sprays’ overall behavior. These experimental results and thermodynamic arguments are then used to demonstrate the limitations of some existing methods for identifying the onset of spray plume interaction and spray collapse in multi-hole injectors. Further modeling is then undertaken, leading to new criteria for both spray collapse and plume interaction due to flash-boiling. These criteria employ simple physical arguments, geometrical parameters and the fuel’s thermodynamic property data, and appear to be applicable to any fuel injector.

Experimental characterization of high pressure gasoline direct injection sprays

An experimental investigation of multihole gasoline direct injection sprays at high injection pressures in a quiescent test chamber is carried out. A multihole injector with six injection holes and 60° spray cone angle is used for this purpose. High-speed Mie-scattering and high-speed Schlieren visualisations are used to characterise vapour penetration, liquid penetration, spray angle and velocity under typical engine high load and low load conditions. Variations of chamber conditions are also investigated in order to assess the effects of chamber temperature, density and pressure on the spray characteristics. The important chamber parameters are identified which affect the performance of multihole injectors in spark ignition engines.

Influence of chamber pressure on CNG jet characteristics of a multi-hole high pressure injector

Natural Gas Direct Injection (NGDI) engines have attracted attention of engine manufacturers because of low pollutant emissions and high efficiency. The jet structure and injector properties are control parameters for optimal mixture formation and stable combustion. Here, the jet characteristics are investigated experimentally. The natural gas jet, injected through a multi-hole injector, is visualized using Schlieren photography. The effects of injection and chamber pressures on macroscopic jet characteristics are examined. New correlations for tip speed and tip penetration are presented. Results show that reducing chamber pressure is more effective than injection pressure for increasing the jet axial penetration. Moreover, the linear relation between non-dimensional tip penetration and time is dependent on the chamber-to-injected gas density ratio.

多噴孔ディーゼル噴霧の後燃え期間における燃焼と燃焼生成物濃度履歴に関する研究

多噴孔ディーゼル噴霧の後燃え期間における燃焼と燃焼生成物濃度履歴に関する研究

Development of MGE 1.8T combustion system assisted by numerical simulation

This paper describes the CFD assisted combustion system development for a 1.8 L turbo GDI engine which has been developed by SAIC Motor. The combustion system is a direct injected turbocharged system employing centre-mounted multi-hole injectors. The in-cylinder charge motion, fuel injection, air/fuel mixing and combustion processes in the combustion system were evaluated. Proposed intake port options were numerically investigated and compared. Impingement of fuel droplets on piston crown, and wetting on the walls of combustion chamber and the subsequent impacts on mixture formation and oil dilution were investigated by both CFD tool and engine test approaches. Spray targeting was optimised to minimise oil dilution, and multiple fuel injection strategies were investigated to understand its impact on injection, mixture formation and combustion process. The concentrations of pollutants including CO, NOx, HC and soot were simulated. The present simulation results agree well with the measurement data from engine testing, including cylinder gas pressure.

Application of Particle Method to Fuel Spray of Multi-hole Injector

Application of Particle Method to Fuel Spray of Multi-hole Injector

Time-dependent line-of-sight extinction tomography for multi-hole GDI injectors

Finely atomized sprays from multi-hole gasoline direct injection (GDI) fuel injectors make them an ideal choice for automobile applications. A knowledge of the factors affecting the performance of these injectors is hence important. In the study presented here, we employ statistical extinction tomography to examine the transient characteristics of two GDI fuel injectors with five and six holes. Two axial locations, 25 mm and 35 mm from the injector exit, are chosen for experimental measurements, and the dependence of injection pressure and ambient temperature on plume locations and angles is examined from these measurements. A pressure chamber with opposing windows is used which permits the nozzle to be rotated 12 times (30° each rotation) to obtain information on the complete spray structure. Additionally, the plume centroid locations are measured and compared with those obtained with a mechanical patternator. The centroid locations from the two instruments compare favorably.

Investigation of deposit effect on multi-hole injector spray characteristics and air/fuel mixing process

An optical-based experimental study of the injector deposit effect on a multi-hole GDI injector was performed first. After carefully calibrating the spray model with the experiment data, a three-dimensional computational fluid dynamics (CFD) simulation was then carried out to study the deposit effect on the air/fuel mixture preparation process in an optical research GDI engine. Six different injection timings were used for full-cycle simulations. The numerical engine condition was at stoichiometric ratio, 1200rpm and 150bar injection pressure. The experimental results showed that injector deposit would lead to lower fuel mass flow rate, with 5.4%, 5.7% and 6.1% loss at 50, 100 and 150bar respectively. Injector deposit resulted in longer penetration length and the effect displayed hole to hole difference. The maximum increment was observed for the ignition jets with 11.6% at 150bar. Injector deposit led to higher droplet velocity and larger droplet size and the difference increased with injection pressure. For the air/fuel mixing simulation, the injector deposit led to more fuel impingement on the piston and cylinder walls, as well as a lower mean equivalence ratio during late injection events. The distorted spray pattern led to higher fuel stratification level. In very late injection cases, the injector deposit led to a very lean mixture near the spark plug which could result in unstable engine performance; while the rich regions at the cylinder sides could result in higher emissions. Comparison of computed results with PLIF (planar laser induced fluorescence) images provided a satisfactory validation for the model.

Novel insights into the dynamic structure of biodiesel and conventional fuel sprays from high-pressure diesel injectors

The spray dynamics of biodiesel has not been thoroughly investigated in previous studies. Understanding the dynamic structure is important for successful modeling of biodiesel sprays and the proper use of biodiesel in modern engines. This study compares the dynamic structure of biodiesel and conventional fuel sprays from single- and multi-hole diesel injectors using a synchrotron X-ray velocimetry technique. Three fuels, biodiesel, diesel and Viscor16br, were used in this study. The results showed that the high viscosity and density of biodiesel decreased the injection velocity compared to conventional fuels. The biodiesel effect on injection velocity was less significant for the multi-hole injector. For the single-hole injector, the biodiesel slowed down the flow breakup and increased the intact core length that caused the lower velocity decay rate and turbulence intensity along the spray center. Meanwhile, in the case of the multi-hole injector, the flow breakup, and the velocity decay rate and turbulence intensity along the spray center appeared equivalent regardless of the fuel. The fuel viscosity did not play a dominant role in the spray dynamics of the multi-hole injector and the dynamic structure of the biodiesel and conventional fuel sprays can be scaled based on the momentum conserving gas jet theory.

RETRACTED: Investigation on the spray characteristics of standard gasoline, n-pentane, iso-octane and ethnaol with a novel heated tip SIDI injector

This article has been retracted: please see Elsevier Policy on Article Withdrawal ( http://www.elsevier.com/locate/withdrawalpolicy ). This article has been retracted at the request of the Editor-in-Chief. The corresponding author published this article without the prior consent or knowledge of the listed co-authors. Furthermore, some data included in this paper has been taken from previously published papers without acknowledgement. Aleiferis PG, van Romunde ZR. An Analysis of Spray Development with iso-Octane, n-Pentane, Gasoline, Ethanol and n-Butanol from a Multi-Hole Injector Under Hot Fuel Conditions Fuel, 2013, Vol: 105, Pages: 143–168. Aleiferis PG, van Romunde ZR, Cracknell RF, Walmsley HL. Effect of Fuel Properties on Spray Development from a Multi-Hole DISI Engine Injector SAE Transactions, Journal of Engines, 2007, Vol: 116, Pages: 1313-1331, Paper No 2007-01-4032. van Romunde, ZR. Factors affecting the development of sprays produced by Multihole injectors for Direct-Injection Engine Applications PhD Thesis, 2011, University College London (UCL) http://discovery.ucl.ac.uk/1318146/1/1318146.pdf . The corresponding author would like to apologize to all affected parties.

Near-nozzle spray and spray collapse characteristics of spark-ignition direct-injection fuel injectors under sub-cooled and superheated conditions

There is limited literature available regarding the spray collapse process and the characteristics of flash boiling spray near the critical location of the nozzle exit, even though flash boiling has been proven to produce finer fuel spray with much improved vaporizing quality, and liquid fuel atomizes quickly soon after it is discharged from the nozzle. In this study, the near-nozzle fuel spray of various types of spark-ignition direct-injection prototype multi-hole injectors was investigated under a wide range of sub-cooled and superheated conditions using a high-speed backlit imaging technique. The effects of fuel temperature, ambient pressure, nozzle L/D ratio, and nozzle number, as well as near-nozzle spray characteristics and spray collapse phenomenon under superheated conditions, were studied. Experimental results revealed that both increasing fuel temperature and decreasing ambient pressure resulted in faster fuel jet disintegration and wider fuel plume due to flash boiling. In-nozzle fuel evaporation and outside-nozzle fuel boiling were the primary influences governing flash boiling spray atomization under superheated conditions. Spray collapse length increased with decreasing Pa/Ps ratio; it also increased with the elapse of injection time. Flash boiling spray also has the potential to resolve injector deposit issues with significantly improved end-of-injection performance.

Numerical investigation of stratified air/fuel preparation in a GDI engine

A numerical study has been performed to study atomization and preparation of air/fuel mixture under Gasoline Direct Injection (GDI) conditions. Performance of a single-hole injector was initially investigated and effects of ambient pressure, temperature and temperature of the injected fuel on liquid and vapour penetration lengths were analysed. Subsequently, air/fuel mixture preparation for a multi-hole injector in a simplified GDI engine was investigated. To simulate part load engine conditions, fuel spray and mixing was studied during the compression stroke of the engine. Effect of charge stratification, wall wettability and droplet statics on engine operating conditions like start of injection, injection pulse width, charge inlet temperature, engine RPM and overall equivalence ratio was studied. The droplet phase was tracked using Lagrangian framework and the continuous phase was simulated within the Eulerian framework. Turbulence modelling was performed using the standard k−ε model and ideal gas law was assumed while performing vapour-liquid equilibrium calculations.

The role of spray-enhanced swirl flow for combustion stabilization in a stratified-charge DISI engine

Implementation of spray-guided stratified-charge direct-injection spark-ignited (DISI) engines is inhibited by the occurrence of misfire and partial burns. Engine-performance tests demonstrate that increasing engine speed induces combustion instability, but this deterioration can be prevented by generating swirling flow during the intake stroke. In-cylinder pressure-based heat-release analysis reveals that the appearance of poor-burn cycles is not solely dependent on the variability of early flame-kernel growth. Cycles can experience burning-rate regression during later combustion stages and may or may not recover before the end of the cycle. Thermodynamic analysis and optical diagnostics are used here to clarify why swirl improves the combustion repeatability from cycle to cycle.The fluid dynamics of swirl/spray interaction was previously demonstrated using high-speed PIV measurements of in-cylinder motored flow. It was found that the sprays of the multi-hole injector redistribute the intake-generated swirl flow momentum, thereby creating a better-centered higher angular-momentum vortex with reduced variability. The engine operation with high swirl was found to have significant improvement in cycle-to-cycle variations of both flow pattern and flow momentum.This paper is an extension of the previous work. Here, PIV measurements and flame imaging are applied to fired operation for studying how the swirl flow affects variability of ignition and subsequent combustion phases. PIV results for fired operation are consistent with the measurements made of motored flow. They demonstrate that the spark-plasma motion is highly correlated with the direction of the gas flow in the vicinity of the spark-plug gap. Without swirl, the plasma is randomly stretched towards either side of the spark plug, causing variability in the ignition of the two spray plumes that are straddling the spark plug. In contrast, swirl flow always convects the spark plasma towards one spray plume, causing a more repeatable ignition. The swirl decreases local RMS velocity, consistent with an observed reduction of early-burn variability. Broadband flame imaging demonstrates that with swirl, the flame consistently propagates in multiple directions to consume fuel–air mixtures within the piston bowl. In contrast, operation without swirl displays higher variability of flame-spread patterns, occasionally causing the appearance of partial-burn cycles.

Effect of fuel and nozzle geometry on the off-axis oscillation of needle in diesel injectors using high-speed X-ray phase contrast imaging

The diesel spray characteristics are strongly influenced by the flow dynamics inside the injector nozzle. Moreover, the off-axis oscillation of needle could lead to variation of orifice flow in the nozzle. In this paper, the needle oscillation was investigated using high-speed X-ray phase contrast imaging and quantitative image processing. The effects of fuel, injection pressure and nozzle geometry on the needle oscillation were analyzed. The results showed that the vertical and horizontal oscillation of needle was independent on the injection pressure. The maximum oscillation range of 14μ m was found. Biodiesel application slightly decreased the needle oscillation due to high viscosity. The needle oscillation range increased generally with increasing hole number. The larger needle oscillation in multi-hole injectors was dominated by the geometry problem or production issue at lower needle lift. In addition, the influence of needle oscillation on the spray morphology was also discussed.

Multi-Physical Fields Coupling Simulation and Performances Analysis of a Novel Heated-Tip Injector

A novel heated-tip multihole spark-ignition direct-injection injector was designed and manufactured to investigate its coupling mechanism of the multiphysical fields and comprehensive performances. The coupling relationship and formation among the electromagnetic, thermal, fluid flow, and spray fields was analyzed based on coupling theories. A data information interface platform was established based on the commercial software, which was used to explore how the key parameters impact the novel spark-ignition direct-injection injector. According to the relationship among the different physical fields, coupling models were established based on the finite element method, and the comprehensive performances of the spark-ignition direct-injection injector were analyzed systematically. Systematic experiments were used to validate and verify the coupling mechanism and the accuracy of the simulation model. The comparisons of the conventional spark-ignition direct-injection injector and novel heated-tip multihole injector indicated that the novel heated-tip spark-ignition direct-injection injector has the ability to heat the fuel to a high temperature in a short time. The high temperature is the key factor that changes the electromagnetic characteristics, dynamic response, cavitation structure, and spray characteristics.

Large Eddy Simulation of GDI Single-hole and Multi-hole Injector Sprays with Comparison of Numerical Break-up Models and Coefficients

In the present study the fuel spray of a gasoline direct injected engine with multi-hole injector is simulated. Simulation inputs data, injection flow rate and spray cone angle are obtained from previous experimental studies. Log-normal distribution with different standard deviation is used for initial droplet size as the primary break-up model in order to reach the agreement between experimental and calculated spray tip penetration. As the first step, only one plume of spray injected into a quiescent air environment is simulated and validated by varying break-up model and standard deviation. Then, with coefficient obtained from the single jet simulation all six spray jets are simulated based on the injector nozzles geometry. The comparison between single-jet simulation and multi-jet simulation shows that validated model coefficients for the single-jet spray cannot be used for multi-jet spray simulation without significant modifications due to adjacent jet interaction and pressure drag. A set of new coefficients for the multi-jet spray is presented

Differential infrared thermography of gasoline direct injection sprays

Advances in experimental techniques and simulations are necessary building blocks for the overall effort to reduce the CO2 and pollutant emissions of future gasoline direct injection engines. Wall wetting and inhomogeneous fuel distribution are two known causes of particulate emissions whose prediction within three dimensional computational fluid dynamics can be made more reliable based on accurate spray temperature data. Results from differential infrared thermography (DIT) of a hollow cone and multi-hole gasoline direct injector are presented. Compared to previous applications of DIT, the data processing and temperature calculation methods have been refined. Interpretation of the results is supported by simulations based on the light scattering and absorption properties of small droplets given by Mie theory.

Spray and evaporation characteristics of ethanol and gasoline direct injection in non-evaporating, transition and flash-boiling conditions

Ethanol direct injection plus gasoline port injection (EDI+GPI) represents a more efficient and flexible way to utilize ethanol fuel in spark ignition engines. To exploit the potentials of EDI, the mixture formation characteristics need to be investigated. In this study, the spray and evaporation characteristics of ethanol and gasoline fuels injected from a multi-hole injector were investigated by high speed Shadowgraphy imaging technique in a constant volume chamber. The experiments covered a wide range of fuel temperature from 275K (non-evaporating) to 400K (flash-boiling) which corresponded to cold start and running conditions in an engine. The spray transition process from normal-evaporating to flash-boiling was investigated in greater details than the existed studies. Results showed that ethanol and gasoline sprays demonstrated the same patterns in non-evaporating conditions. The sprays could be considered as non-evaporating when vapour pressure was lower than 30kPa. Ethanol evaporated more slowly than gasoline did in low temperature environment, but they reached the similar evaporation rates when temperature was higher than 375K. This suggested that EDI should only be applied in high temperature engine environment. For both ethanol and gasoline sprays, when the excess temperature was smaller than 4K, the sprays behaved the same as the subcooled sprays did. The sprays collapsed when the excess temperature was 9K. Flash-boiling did not occur until the excess temperature reached 14K. The fuel temperature changed not only the spray evaporation modes but also the breakup mechanisms.

Diesel ignition delay and lift-off length through different methodologies using a multi-hole injector

In this paper, lift-off length has been measured via both broadband luminosity and OH chemiluminescence. In addition, ignition delay has also been measured via broadband chemiluminescence and Schlieren imaging. A 3 orifice injector from the Engine Combustion Network (ECN) set, referred to as Spray B, and a single component fuel (n-dodecane) was used. Experiments were carried out in a constant flow and pressure facility, that allowed to reproduce engine-like thermodynamic conditions, and enabled the study to be performed over a wide range of test conditions with a very high repetition rate. Data obtained was also compared with results from a single orifice injector also from the Engine Combustion Network, with analog orifice characteristics (90μm outlet diameter and convergent shape) and technology as the injector used. Results showed that there is good correlation between the ignition delay measured through both methodologies, that oxygen concentration and injection pressure plays a minor role in the ignition delay, being ambient temperature and density the parameters with the highest influence. Lift-off length measurements showed significant differences between methodologies. Minor deviation was observed between injectors with different nozzle geometry (seat inclination angle), due to temperature variations along the chamber, highlighting the importance of temperature distribution along combustion vessels. Empirical correlations for lift-off and ignition delay were calculated, underlining the effect of the conditions on the parameters studied. Coefficients of the correlations were compared with results for the single orifice injector, this showed that variations of test conditions have the same impact on ignition delay and lift-off length regardless the nozzle orifice configuration.