Analysis of the Injection Process in Direct Injected Natural Gas Engines: Part I—Study of Unconfined and In-Cylinder Plume Behavior

1994 ◽  
Vol 116 (4) ◽  
pp. 799-805 ◽  
Author(s):  
M. J. Jennings ◽  
F. R. Jeske
Keyword(s):  
Natural Gas ◽  
Near Field ◽  
Direct Injection ◽  
Three Dimensional ◽  
Natural Gas Engines ◽  
Injection Process ◽  
Constant Volume Chamber ◽  
Computational Fluid Dynamics Analysis ◽  
Heavy Duty Diesel Engine ◽  
Heavy Duty Diesel

A study of natural gas (NG) direct injection (DI) processes has been performed using multidimensional computational fluid dynamics analysis. The purpose was to improve the understanding of mixing in DI NG engines. Calculations of injection into a constant-volume chamber were performed to document unconfined plume behavior. A full three-dimensional calculation of injection into a medium heavy-duty diesel engine cylinder was also performed to study plume behavior in engine geometries. The structure of the NG plume is characterized by a core of unmixed fuel confined to the near-field of the jet. This core contains the bulk of the unmixed fuel and is mixed by the turbulence generated by the jet shear layer. The NG plume development in the engine is dominated by combustion chamber surface interactions. A Coanda effect causes plume attachment to the cylinder head, which has a detrimental impact on mixing. Unconfined plume calculations with different nozzle hole sizes demonstrate that smaller nozzle holes are more effective at mixing the fuel and air.

Analysis of the Injection Process in Direct Injected Natural Gas Engines: Part II—Effects of Injector and Combustion Chamber Design

1994 ◽  
Vol 116 (4) ◽  
pp. 806-813 ◽  
Author(s):  
M. J. Jennings ◽  
F. R. Jeske
Keyword(s):  
Natural Gas ◽  
Combustion Chamber ◽  
Negative Impact ◽  
Direct Injection ◽  
Three Dimensional ◽  
Optimal Number ◽  
Design Parameters ◽  
Piston Bowl ◽  
Injection Process ◽  
Computational Fluid Dynamics Analysis

A study of natural gas (NG) direct injection (DI) processes in engines has been performed using multidimensional computational fluid dynamics analysis. The purpose was to investigate the effects of key engine design parameters on the mixing in DI NG engines. Full three-dimensional calculations of injection into a medium heavy-duty diesel engine cylinder were performed. Perturbations on a baseline engine configuration were considered. In spite of single plume axisymmetric injection calculations that show mixing improves as nozzle hole size is reduced: plume merging caused by having too many nozzle holes has a severe negative impact on mixing; and increasing the number of injector holes strengthens plume deflection toward the cylinder head, which also adversely affects mixing. The optimal number of holes for a quiescent engine was found to be that which produces the largest number of separate NG plumes. Increasing the nozzle angle to reduce plume deflection can adversely affect mixing due to reduced jet radial penetration. Increasing the injector tip height is an effective approach to eliminating plume deflection and improving mixing. Extremely high-velocity squish flows, with penetration to the center of the piston bowl, are necessary to have a significant impact on mixing. Possible improvements in mixing can be realized by relieving the center of the piston bowl in typical “Mexican hat” bowl designs. CFD analysis can effectively be used to optimize combustion chamber geometry by fitting the geometry to computed plume shapes.

Direct Injection of Natural Gas in a Heavy-Duty Diesel Engine

2002 ◽  
Author(s):  
James Harrington ◽  
Sandeep Munshi ◽  
Costi Nedelcu ◽  
Patric Ouellette ◽  
Jeff Thompson ◽  
...  
Keyword(s):  
Diesel Engine ◽  
Natural Gas ◽  
Direct Injection ◽  
Heavy Duty ◽  
Heavy Duty Diesel Engine ◽  
Heavy Duty Diesel

Transient Behavior of Glow Plugs in Direct-Injection Natural Gas Engines

2012 ◽  
Vol 134 (9) ◽  
Author(s):  
Stewart Xu Cheng ◽  
James S. Wallace
Keyword(s):  
Heat Transfer ◽  
Natural Gas ◽  
Direct Injection ◽  
High Surface ◽  
Cold Start ◽  
Transfer Model ◽  
Ignition Process ◽  
Computational Domain ◽  
Glow Plug ◽  
Natural Gas Engines

Glow plugs are a possible ignition source for direct injected natural gas engines. This ignition assistance application is much different than the cold start assist function for which most glow plugs have been designed. In the cold start application, the glow plug is simply heating the air in the cylinder. In the cycle-by-cycle ignition assist application, the glow plug needs to achieve high surface temperatures at specific times in the engine cycle to provide a localized source of ignition. Whereas a simple lumped heat capacitance model is a satisfactory representation of the glow plug for the air heating situation, a much more complex situation exists for hot surface ignition. Simple measurements and theoretical analysis show that the thickness of the heat penetration layer is small within the time scale of the ignition preparation period (1–2 ms). The experiments and analysis were used to develop a discretized representation of the glow plug domain. A simplified heat transfer model, incorporating both convection and radiation losses, was developed for the discretized representation to compute heat transfer to and from the surrounding gas. A scheme for coupling the glow plug model to the surrounding gas computational domain in the KIVA-3V engine simulation code was also developed. The glow plug model successfully simulates the natural gas ignition process for a direct-injection natural gas engine. As well, it can provide detailed information on the local glow plug surface temperature distribution, which can aid in the design of more reliable glow plugs.

Numerical and experimental investigations of the early injection process of Spray G in a constant volume chamber and an optically accessible DISI engine

2021 ◽  
pp. 146808742110394
Author(s):  
Andrea Pati ◽  
Davide Paredi ◽  
Cooper Welch ◽  
Marius Schmidt ◽  
Christopher Geschwindner ◽  
...  
Keyword(s):  
Direct Injection ◽  
Constant Volume ◽  
Experimental Investigations ◽  
Spark Ignition Engines ◽  
Charge Motion ◽  
Injection Process ◽  
Constant Volume Chamber ◽  
Before And After ◽  
The Individual ◽  
Intake Flow

In this work, the Engine Combustion Network Spray G injector was mounted in the Darmstadt optical-accessible engine to study phenomena typical of multi-hole, early direct-injection events in spark-ignition engines characterized by tumble flow charge motion. Dedicated experimental measurements of both in-cylinder spray morphology and flow velocities before and after the injection process were carried out to assess the adopted numerical setup under real engine conditions. A dynamic secondary breakup model from the literature was coupled with an atomization multi-motion regime model. The model was validated against state-of-the-art ECN Spray G experiments for a constant-volume chamber under low evaporating condition. Then, the simulation of the spray injection in the engine was carried out and the achieved results were compared against the experimental data. Overall, good agreement between experiments and simulations was observed for the spray morphology and velocity fields in both cases. With reference to engine calculations the intake flow was seen to induce spray asymmetry. A partial vortex generated during the intake phase on the tumble plane interacts with the spray, developing into a full vortex which induces an upward flow that stabilizes the spray. The upward flows below the intake valve increase the dilution of the plume outside the tumble plane, which therefore exhibits reduced penetration. Moreover, the intake valves protect from the energetic intake flow the recirculation vortex generated at the tip of the plumes that lie outside the tumble plane. The intake flow helps fuse the vapor fuel clouds of the individual plumes near the injector tip, obtaining a vapor fuel with a shape like that generated by a horseshoe multi-hole injector. Finally, a phenomenological model of the interaction between the multi-hole injector jets and the engine intake flow was introduced to describe the spray evolution in a typical DISI engine.

Effect of Piston Crevices on 3D Simulation of a Heavy-Duty Diesel Engine Retrofitted to Natural Gas Spark Ignition

2018 ◽  
Author(s):  
Iolanda Stocchi ◽  
Jinlong Liu ◽  
Cosmin E. Dumitrescu ◽  
Michele Battistoni ◽  
Carlo Nazareno Grimaldi
Keyword(s):  
Fuel Injection ◽  
Direct Injection ◽  
Combustion Model ◽  
Heavy Duty ◽  
Ic Engine ◽  
Pressure Trace ◽  
Heavy Duty Diesel Engine ◽  
Heavy Duty Diesel ◽  
Flame Behavior ◽  
Experimental Pressure

3D CFD IC engine simulations that use a simplified combustion model based on the flamelets concept can provide acceptable results with minimum computational costs and reasonable running times. More, the simulation can neglect small combustion chamber details such as valve crevices, valve recesses and piston crevices volume. The missing volumes are usually compensated by changes in the squish volume (i.e., by increasing the clearance height of the model compared to the real engine). This paper documents some of the effects that such an approach would have on the simulated results of the combustion phenomena inside a conventional heavy-duty direct-injection CI engine, which was converted to port-fuel injection SI operation. 3D IC engine simulations with or without crevice volumes were run using the G-equation combustion model. A proper parameter choice ensured that the simulation results agreed well with the experimental pressure trace. The results show that including the crevice volume affected the mass of unburned mixture inside the squish region, which in turn influenced the flame behavior and heat release during late-combustion stages.

scholarly journals Numerical investigation of natural gas direct injection properties and mixture formation in a spark ignition engine

2014 ◽  
Vol 18 (1) ◽  
pp. 39-52
Author(s):  
Bijan Yadollahi ◽  
Masoud Boroomand
Keyword(s):  
Numerical Model ◽  
Natural Gas ◽  
Internal Combustion Engines ◽  
Gasoline Engine ◽  
Direct Injection ◽  
Spark Ignition ◽  
Computational Effort ◽  
Spark Ignition Engine ◽  
Validity Of Results ◽  
Injection Process

In this study, a numerical model has been developed in AVL FIRE software to perform investigation of Direct Natural Gas Injection into the cylinder of Spark Ignition Internal Combustion Engines. In this regard two main parts have been taken into consideration, aiming to convert an MPFI gasoline engine to direct injection NG engine. In the first part of study multi-dimensional numerical simulation of transient injection process, mixing and flow field have been performed via three different validation cases in order to assure the numerical model validity of results. Adaption of such a modeling was found to be a challenging task because of required computational effort and numerical instabilities. In all cases present results were found to have excellent agreement with experimental and numerical results from literature. In the second part, using the moving mesh capability the validated model has been applied to methane Injection into the cylinder of a Direct Injection engine. Five different piston head shapes along with two injector types have been taken into consideration in investigations. A centrally mounted injector location has been adapted to all cases. The effects of injection parameters, combustion chamber geometry, injector type and engine RPM have been studied on mixing of air-fuel inside cylinder. Based on the results, suitable geometrical configuration for a NG DI Engine has been discussed.

Modeling of Ignition and Combustion for Glow Plug Assisted Direct Injection Natural Gas Engines

2012 ◽  
Author(s):  
Stewart Xu Cheng ◽  
James S. Wallace
Keyword(s):  
Natural Gas ◽  
Heated Surface ◽  
Direct Injection ◽  
Cfd Modeling ◽  
Spontaneous Ignition ◽  
Layer Model ◽  
Glow Plug ◽  
Natural Gas Engines ◽  
Gas Ignition ◽  
Ignition And Combustion

Direct injection natural gas (DING) engines offer the advantages of high thermal efficiency and high power output compared to spark ignition natural gas engines. Injected natural gas requires some form of ignition assist in order to ignite in the time available in a diesel engine combustion chamber. A glow plug — a heated surface — is one form of ignition assist. Simple experiments show that the thickness of the heat penetration layer of a glow plug is very small (≈10−5 m) within the time scale of the ignition preparation period (1–2 ms). Meanwhile, the theoretical analyses reveal that only a very thin layer of the surrounding gases (in micrometer scale) can be heated to high temperature to achieve spontaneous ignition. A discretized glow plug model and virtual gas sub-layer model have been developed for CFD modeling of glow plug ignition and combustion for DING diesel engines. In this paper, CFD modeling results are presented. The results were obtained using a KIVA3 code modified to include the above mentioned new developed models. Natural gas ignition over a bare glow plug was simulated. The results were validated against experiments. Simulation of natural gas ignition over a shielded glow plug was also carried out and the results illustrate the necessity of using a shield. This paper shows the success of the discretized glow plug model working together with the virtual gas sub-layer model for modeling glow plug assisted natural gas direct injection engines. The modeling can aid in the design of injection and ignition systems for glow plug assisted DING engines.

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