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Technical Paper

Evaluating CFD Models of Axial Fans by Comparisons with Phase-Averaged Experimental Data

2001-05-14
2001-01-1701
In order to improve the reliability of fan design and the prediction of underhood engine cooling based on CFD, Valeo Motors and Actuators and Michigan State University have teamed up to develop a comprehensive experimental and numerical database. The initial focus has been on the simulations of the isolated fan environment in two different test facilities. To understand the discrepancies observed in the comparisons of integral performances, the first detailed hot wire measurements on the MSU test facility have been collected. The data are split into mean velocity components and RMS fluctuations. The former are successfully compared to three detailed turbulent numerical simulations of the corresponding facilities.
Technical Paper

Evaluation of Turbulence Statistics from Engine Cooling Fan Velocity Measurements

2001-05-14
2001-01-1710
The present communication reports on processing and interpreting velocity measurements in the wake of a cooling fan. Velocity data are typically phase averaged to create statistics that would be observed in a rotating frame of reference. The difference between any given instantaneous measurement and the phase mean value is often referred to as the fluctuating component of velocity. These deviations can be caused by a variety of mechanisms (blade vibration for example) and do not necessarily represent “turbulence”. A different approach using an eigenfunction decomposition of the data is used on a sample data set to help distinguish between cycle-to-cycle variations and turbulence.
Technical Paper

Characterization of Crankcase Pressure Variation during the Engine Cycle of an Internal Combustion Engine

2017-03-28
2017-01-1088
High frequency variations in crankcase pressure have been observed in Inline-four cylinder (I4) engines and an understanding of the causes, frequency and magnitude of these variations is helpful in the design and effective operation of various engine systems. This paper shows through a review and explanation of the physics related to engine operation followed by comparison to measured vehicle data, the relationship between crankcase volume throughout the engine cycle and the observed pressure fluctuations. It is demonstrated that for a known or proposed engine design, through knowledge of the key engine design parameters, the frequency and amplitude of the cyclic variation in crankcase pressure can be predicted and thus utilized in the design of other engine systems.
Technical Paper

Performance Assessment of a Single Jet, Dual Diverging Jets, and Dual Converging Jets in an Auxiliary Fueled Turbulent Jet Ignition System

2018-04-03
2018-01-1135
An auxiliary fueled prechamber ignition system can be used in an IC engine environment to provide lean limit extension with minimal cyclic variability and low emissions. Geometry and distribution of the prechamber orifices form an important criterion for performance of these systems since they are responsible for transferring and distributing the ignition energy into the main chamber charge. Combustion performance of nozzles with a single jet, dual diverging jets and dual converging jets for a methane fueled prechamber ignition system is evaluated and compared in a rapid compression machine (RCM). Upon entering the main chamber, the dual diverging jets penetrate the main chamber in opposite directions creating two jet tips, while the dual converging jets, after exiting the orifices, converge into a single location within the main chamber. Both these configurations minimize jet-wall impingement compared to the single jet.
Technical Paper

Modeling of Thermophoretic Soot Deposition and Stabilization on Cooled Surfaces

2011-09-13
2011-01-2183
EGR coolers are used in combustion engines to reduce NOx emissions. However, heat transfer in these coolers also results in thermophoresis-temperature-gradient driven motion of suspended particles towards cooler regions-which leads to significant soot deposition. A simple one-dimensional model is proposed to predict the deposition velocity and soot layer thickness that compares reasonably well with experimental data. The behavior of soot deposits on cooled surfaces is complex, with the thickness of the soot layer stabilizes after around 100 hours, reaching a uniform, thickness over the entire heat-exchanger surface. An analysis of this trend and a tentative mechanism to explain this type of behavior is given, based on experimental observations.
Technical Paper

Numerical Simulation of a Direct-Injection Spark-Ignition Engine with Different Fuels

2009-04-20
2009-01-0325
This paper focuses on the numerical investigation of the mixing and combustion of ethanol and gasoline in a single-cylinder 3-valve direct-injection spark-ignition engine. The numerical simulations are conducted with the KIVA code with global reaction models. However, an ignition delay model mitigates some of the deficiencies of the global one-step reaction model and is implemented via a two-dimensional look-up table, which was created using available detailed kinetics models. Simulations demonstrate the problems faced by ethanol operated engines and indicate that some of the strategies used for emission control and downsizing of gasoline engines can be employed for enhancing the combustion efficiency of ethanol operated engines.
Technical Paper

Establishment of a Database by Conducting Intake Manifold and In-Cylinder Flow Measurements inside an Internal Combustion Engine Assembly

2013-04-08
2013-01-0565
An experimental study has been conducted to quantify the velocity and pressure inside an idealized intake manifold of a motored internal combustion engine assembly. The aim of this work is to provide the real-time boundary conditions for more accurate multi-dimensional numerical simulations of complex in-cylinder flows in an internal combustion engine as well as the resultant in-cylinder flow patterns. The geometry of the intake manifold is simplified for this purpose. A hot-wire anemometer and a piezoresistive absolute pressure transducer are used to measure the velocity and pressure, respectively, over a plane inside the circular section of the intake manifold. In addition, pressure measurements are performed over an elliptical section near the intake port. Phase-averaged velocity and pressure profiles are then calculated from the instantaneous measurements. Experiments were performed at 900 and 1200 rpm engine speeds with wide open throttle.
Technical Paper

Large Eddy Simulation of Evaporating Spray with a Stochastic Breakup Model

2013-04-08
2013-01-1101
Large Eddy Simulations of atomization and evaporation of liquid fuel sprays in diesel engine conditions are performed with stochastic breakup and non-equilibrium droplet heat and mass transfer models. The size and number density of the droplets generated by the breakup model are assumed to be governed by a Fokker-Planck equation, describing the evolution of the PDF of droplet radii. The fragmentation intensity spectrum is considered to be Gaussian and the scale of Lagrangian relative velocity fluctuations is included in the breakup frequency calculations. The aerodynamic interactions of droplets in the dense part of the spray are modeled by correcting the relative velocity of droplets in the wake of other droplets. The stochastic breakup model is employed together with the wake interaction model for simulations of non-evaporating and evaporating sprays in various gas temperature and pressure conditions.
Technical Paper

Knock Detection for a Large Displacement Air-Cooled V-Twin Motorcycle Engine Using In-Cylinder Ionization Signals

2008-09-09
2008-32-0028
To obtain the maximum output power and fuel economy from an internal combustion engine, it is often necessary to detect engine knock and operate the engine at its knock limit. This paper presents the ability to detect knock using in-cylinder ionization signals on a large displacement, air-cooled, “V” twin motorcycle engine over the engine operational map. The knock detection ability of three different sensors is compared: production knock (accelerometer) sensor, in-cylinder pressure sensor, and ionization sensor. The test data shows that the ionization sensor is able to detect knock better than the production knock sensor when there is high mechanical noise present in the engine.
Technical Paper

Combustion Characteristics of a Single-Cylinder Engine Equipped with Gasoline and Ethanol Dual-Fuel Systems

2008-06-23
2008-01-1767
The requirement of reduced emissions and improved fuel economy led the introduction of direct-injection (DI) spark-ignited (SI) engines. Dual-fuel injection system (direct-injection and port-fuel-injection (PFI)) was also used to improve engine performance at high load and speed. Ethanol is one of the several alternative transportation fuels considered for replacing fossil fuels such as gasoline and diesel. Ethanol offers high octane quality but with lower energy density than fossil fuels. This paper presents the combustion characteristics of a single cylinder dual-fuel injection SI engine with the following fueling cases: a) gasoline for PFI and DI, b) PFI gasoline and DI ethanol, and c) PFI ethanol and DI gasoline. For this study, the DI fueling portion varied from 0 to 100 percentage of the total fueling over different engine operational conditions while the engine air-to-fuel ratio remained at a constant level.
Technical Paper

Optical Diagnostic Combustion Comparisons of Pump Diesel with Bio-Derived Diesel Blends in an Optical DI Diesel Engine

2012-04-16
2012-01-0868
Combustion studies were completed using an International VT275-based, optical DI Diesel engine fueled with Diesel fuel, a Canola-derived FAMES biodiesel, as well as with a blend of the Canola-derived biodiesel and a cetane-reducing, oxygenated fuel, Di-Butyl Succinate. Three engine operating conditions were tested to examine the combustion of the fuels across a range of loads and combustion schemes. Pressure data and instantaneous images were recorded using a high-speed visible imaging, infrared imaging, and high-speed OH imaging techniques. The recorded images were post processed to analyze different metrics, such as projected areas of in-cylinder soot, OH, and combustion volumes. A substantially reduced in-cylinder area of soot formation is observed for the Canola-DBS blended fuel with a slight reduction from the pure FAMES biodiesel compared to pump Diesel fuel.
Technical Paper

Spark Ignition and Pre-Chamber Turbulent Jet Ignition Combustion Visualization

2012-04-16
2012-01-0823
Natural gas is a promising alternative fuel as it is affordable, available worldwide, has high knock resistance and low carbon content. This study focuses on the combustion visualization of spark ignition combustion in an optical single cylinder engine using natural gas at several air to fuel ratios and speed-load operating points. In addition, Turbulent Jet Ignition optical images are compared to the baseline spark ignition images at the world-wide mapping point (1500 rev/min, 3.3 bar IMEPn) in order to provide insight into the relatively unknown phenomenon of Turbulent Jet Ignition combustion. Turbulent Jet Ignition is an advanced spark initiated pre-chamber combustion system for otherwise standard spark ignition engines found in current passenger vehicles. This next generation pre-chamber design simply replaces the spark plug in a conventional spark ignition engine.
Technical Paper

In-cylinder Combustion Visualization of a Direct-injection Spark-ignition Engine with Different Operating Conditions and Fuels

2012-09-10
2012-01-1644
A direct-injection and spark-ignition single-cylinder engine with optical access to the cylinder was used for the combustion visualization study. Gasoline and ethanol-gasoline blended fuels were used in this investigation. Experiments were conducted to investigate the effects of fuel injection pressure, injection timing and the number of injections on the in-cylinder combustion process. Two types of direct fuel injectors were used; (i) high-pressure production injector with fuel pressures of 5 and 10 MPa, and (ii) low-pressure production-intent injector with fuel pressure of 3 MPa. Experiments were performed at 1500 rpm engine speed with partial load. In-cylinder pressure signals were recorded for the combustion analyses and synchronized with the high-speed combustion imaging recording. Visualization results show that the flame growth is faster with the increment of fuel injection pressure.
Technical Paper

Computational Study of a Turbulent Jet Ignition System for Lean Burn Operation in a Rapid Compression Machine

2015-04-14
2015-01-0396
Fully three-dimensional computational fluid dynamic simulations with detailed chemistry of a single-orifice turbulent jet ignition device installed in a rapid compression machine are presented. The simulations were performed using the computational fluid dynamics software CONVERGE and its RANS turbulence models. Simulations of propane fueled combustion are compared to data collected in the optically accessible rapid compression machine that the model's geometry is based on to establish the validity and limitations of the simulations and to compare the behavior of the different air-fuel ratios that are used in the simulations.
Technical Paper

Modeling of Piston Ring-Cylinder Bore-Piston Groove Contact

2015-04-14
2015-01-1724
A three-dimensional piston ring model has been developed using finite element method with eight-node hexahedral elements. The model predicts the piston ring conformability with the cylinder wall as well as the separation gap between the interfaces if existing in the radial direction. In addition to the radial interaction between the ring front face and the cylinder wall, the model also predicts the contact between the ring and groove sides in the axial direction. This means, the ring axial lift, ring twist, contact forces with the groove sides along the circumferential direction are all calculated simultaneously with the radial conformability prediction. The ring/groove side contact can be found for scraper ring at static condition, which is widely used as the second compression ring in a ring pack. Thermal load is believed having significant influence on the ring pack performance.
Technical Paper

A Computational Study of the Effects of Spark Location on the Performance of a Turbulent Jet Ignition System

2016-04-05
2016-01-0608
In this purely computational study, fluid dynamic simulations with active combustion are performed for a Turbulent Jet Ignition (TJI) system installed in a rapid compression machine. The simulations compare the effects that the location of the TJI system’s spark ignition source inside the TJI’s prechamber have on the combustion within the system through the use of four simulations, which are all identically setup with the same initial and boundary conditions except for the location of their respective ignition sources. The four ignition sources are located along the centerline of the axisymmetric prechamber and at varied distances from the orifice exit of the prechamber. Comparison of the simulations demonstrate that the locations furthest from the orifice produce better main chamber ignition as reflected in shorter 0-10% mass fraction burn times. Meanwhile all three of the test cases that were not closest to the orifice all produced similar 10-90% mass fraction burn times.
Technical Paper

CFD Modeling of an Auxiliary Fueled Turbulent Jet Ignition System in a Rapid Compression Machine

2016-04-05
2016-01-0599
Three-dimensional numerical simulation of the turbulent jet ignition combustion process of a premixed methane-air mixture in a Rapid Compression Machine (RCM) was performed using the Converge computational software. Turbulent jet ignition is a prechamber initiated combustion system that can replace the spark plug in a spark ignition engine. The prechamber is a small volume chamber where an injector and spark plug are located and is connected to the main combustion chamber via one or multiple small orifices. Turbulent jet ignition is capable of enabling low temperature combustion, through either lean or dilute combustion. A RANS model, which included a k-ε turbulence model to solve the mean flow and the SAGE chemistry solver with a reduced methane mechanism to solve the chemistry, was used to model the turbulent jet ignition system.
Technical Paper

Analysis of Variations in Fuel Spray, Combustion, and Soot Production in an Optical Diesel Engine Operating Under High Simulated Exhaust Gas Recirculation Operating Conditions

2016-04-05
2016-01-0727
In-cylinder visualization experiments were completed using an International VT275-based optical DI Diesel engine operating under high simulated exhaust gas recirculation combustion conditions. Experiments were run at four load conditions to examine variations in fuel spray, combustion, and soot production. Mass fraction burned analyses of pressure data were used to investigate the combustion processes of the various operating conditions. An infrared camera was used to visualize fuel spray events and exothermic combustion gases. A visible, high-speed camera was used to image natural luminosity produced by soot. The recorded images were post-processed to analyze the fuel spray, the projected exothermic areas produced by combustion, as well as soot production of different load conditions. Probability maps of combustion and fuel spray occurrence in the cylinder are presented for insight into the combustion processes of the different conditions.
Technical Paper

CFD Modeling and Experimental Analysis of a Homogeneously Charged Turbulent Jet Ignition System in a Rapid Compression Machine

2017-03-28
2017-01-0557
Three dimensional numerical simulation of the transient turbulent jet and ignition processes of a premixed methane-air mixture of a turbulent jet ignition (TJI) system is performed using Converge computational software. The prechamber initiated combustion enhancement technique that is utilized in a TJI system enables low temperature combustion by increasing the flame propagation rate and therefore decreasing the burn duration. Two important components of the TJI system are the prechamber where the spark plug and injectors are located and the nozzle which connects the prechamber to the main chamber. In order to model the turbulent jet of the TJI system, RANS k-ε and LES turbulent models and the SAGE chemistry solver with a reduced mechanism for methane are used.
Technical Paper

Model Reference Adaptive Control of a Pneumatic Valve Actuator for Infinitely Variable Valve Timing and Lift

2007-04-16
2007-01-1297
Electro-pneumatic valve actuators are used to eliminate the cam shaft of a traditional internal combustion engine. They are used to control the opening timing, duration, and lift of both intake and exhaust valves. A physics based nonlinear mathematical model called the level one model was built using Newton's law, mass conservation and thermodynamic principles. A control oriented model, the level two model, was created by partially linearizing the level one model for model reference parameter identification. This model reduces computational throughput and enables real-time implementation. A model reference adaptive control system was used to identify the nonlinear parameters that were needed for generating a feedforward control signal. The closed-loop valve lift tracking, valve opening and closing timing control strategies were proposed.
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