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Technical Paper

A 3D Eulerian Model to Improve the Primary Breakup of Atomizing Jet

2003-03-03
2003-01-0005
A 3D Eulerian model has been developed to improve the primary break-up of an atomizing jet. The model is divided in three parts and is implemented in a modified version of KIVA II. The first part focuses mainly on the liquid dispersion, the second on the atomizing process itself, and the third on the adaptation of the model's mathematical formulation to the physics of the flow. Since the spray close to the injector is dense, an Eulerian formulation is thus chosen. However, when the spray is diluted, a Lagrangian formulation should then be applied. Different computations have been carried out using this new model and will be thoroughly discussed in this paper. The first calculation serves as a validation of the model. Those which follow demonstrate the importance of the internal liquid flow inside the injector on the spray development. They also manifest an influence of the air-co-flow, which assists the atomization of the spray.
Technical Paper

A 3D-CFD Methodology for Combustion Modeling in Active Prechamber SI Engines Operating with Natural Gas

2022-03-29
2022-01-0470
Active prechamber combustion systems for SI engines represent a feasible and effective solution in reducing fuel consumption and pollutant emissions for both marine and ground heavy-duty engines. However, reliable and low-cost numerical approaches need to be developed to support and speed-up their industrial design considering their geometry complexity and the involved multiple flow length scales. This work presents a CFD methodology based on the RANS approach for the simulation of active prechamber spark-ignition engines. To reduce the computational time, the gas exchange process is computed only in the prechamber region to correctly describe the flow and mixture distributions, while the whole cylinder geometry is considered only for the power-cycle (compression, combustion and expansion). Outside the prechamber the in-cylinder flow field at IVC is estimated from the measured swirl ratio.
Technical Paper

A 3D-Simulation with Detailed Chemical Kinetics of Combustion and Quenching in an HCCI Engine

2008-06-23
2008-01-1655
A 3D-CFD model with detailed chemical kinetics was developed to investigate the combustion characteristics of HCCI engines, especially those fueled with hydrogen and n-heptane. The effects of changes in some of the key important variables that included compression ratio and chamber surface temperature on the combustion processes were investigated. Particular attention was given, while using a finer 3-D mesh, to the development of combustion within the chamber crevices between the piston top-land and cylinder wall. It is shown that changes in the combustion chamber wall surface temperature values influence greatly the autoignition timing and location of its first occurrence within the chamber. With high chamber wall temperatures, autoignition takes place first at regions near the cylinder wall while with low surface temperatures; autoignition takes place closer to the central region of the mixture charge.
Technical Paper

A 400HP Truck Engine Operating on Natural Gas

1991-11-01
912476
A 14 litre turbo charged intercooled diesel engine has been re-engineered to operate as a spark ignition engine fuelled with natural gas. The design targets were for an efficient engine with low emissions using the lean burn capability of natural gas but without sacrificing power output. The resulting ultra lean burn spark ignition engine achieves diesel engine thermal efficiency, with a much reduced NOx emissions though higher NMHC emissions. The engine changes included revised compression ratio, and combustion chamber shape, inlet system modifications to increase turbulence during combustion, i.e., a “smart burn” system, and a new engine management strategy using a “drive by wire” computer control of fuel and throttle and spark timing. The engine has begun duty in an articulated truck in a short haul parts delivery operation, and monitoring of the in service performance has begun.
Technical Paper

A 50cc Two-Stroke DI Compression Ignition Engine Fuelled by DME

2008-06-23
2008-01-1535
The low auto-ignition temperature, rapid evaporation and high cetane number of dimethyl ether (DME) enables the use of low-pressure direct injection in compression ignition engines, thus potentially bringing the cost of the injection system down. This in turn holds the promise of bringing CI efficiency to even the smallest engines. A 50cc crankcase scavenged two-stroke CI engine was built based on moped parts. The major alterations were a new cylinder head and a 100 bar DI system using a GDI-type injector. Power is limited by carbon monoxide emission but smoke-free operation and NOx < 200ppm is achieved at all points of operation.
Technical Paper

A 7 -Cylinder IVD Compressor for Automotive Air Conditioning

1989-02-01
890309
A 7-cylinder, wobble plate type, infinitely variable displacement, (IVD), compressor has been developed to meet the following requirements as set forth by the world automotive manufacturers: 1 Wide range of capacity control to eliminate clutch cycling which causes temperature and humidity fluctuations of louver outlet air and unexpected engine load variations 2 Near perfect protection of the evaporator against icing 3 Reliability under all field operating conditions 4 Quiet operation in a compact and lightweight package to suit the new trends in automotive design. A simpler mechanism has been applied to the variable angle cam drive and wobble plate rotation prevention method than with the conventional IVD compressor. The 7-cylinder design, with fewer parts for the piston drive mechanism, enables a quiet compressor of 161.3 cc displacement in a 118 mm diameter casing. An internal control valve is integrated in the center of the valve plate assembly.
Technical Paper

A BASIC AIRBAG MODEL

1972-02-01
720426
A mathematical simulation of the operation of a compressed-gas airbag system is developed. A system was built and tested, and the analysis is evaluated on the basis of these tests. Included in the study are nonideal gas effects, manifold and diffuser effects, bag stretch, bag leakage, and overpressurization of the passenger compartment. Interaction between a single rigid object and the bag is also considered. A correlation between bag pressure and the force it generates is obtained. This allows the development of an analytic model for determining the motion of a single rigid mass interacting with a dynamically inflating airbag mounted in a moving vehicle. An application of the model to study rebound of the occupant from the airbag is presented.
Technical Paper

A BRIEF SURVEY of the PRINCIPLES of PRESSURE WATER COOLING

1943-01-01
430122
AS speeds and operational altitudes of modern aircraft continue to increase, it is becoming more and more important that the total drag of the airplane be reduced while the rate of heat dissipation per unit frontal area of radiator be kept as high as possible. The standard method of increasing the temperature difference between cooling medium and coolant has been to use ethylene glycol as a coolant, because its boiling point is much higher than that of water; however, in its pure state glycol has various disadvantages that are not present when a pressure water system is used. This is a sealed system for making use of the physical characteristics of the increase in boiling temperature with pressure. When the radiator receives more heat from the engine than it is dissipating, a small quantity of steam is generated inside the cylinder jackets. The resulting increase in pressure will cause the temperature to rise until a balance is restored between heat rejection and radiator dissipation.
Technical Paper

A Basic Study on Reduction of Cylinder Block Vibrations for Small Diesel Cars

2000-03-06
2000-01-0527
The production unit number of small diesel engine cars tends to decline except recreational vehicles in Japanese market in recent years, while the production unit number in Europe market keeps on increasing owing to the merits of the durability and the fuel consumption. The small diesel engines will have to be improved in the near future by solving major problems such as noise and vibration pollution, environmental pollution, improvement in performance of diesel engines, in order to expand the production of the engines. This paper refers to a basic study on the experimental and analytical methods for the reduction of resonant vibration in each vibration mode on some cylinder blocks of small high-speed diesel engines in rated engine speed range. Hammering test method, which is easy and useful for measuring frequency response functions, is carried out in the experiments.
Technical Paper

A Bench Test Procedure for Evaluating the Cylinder Liner Pitting Protection Performance of Engine Coolant Additives for Heavy Duty Diesel Engine Applications

1996-02-01
960879
Evaluations of the liner pitting protection performance provided by engine coolant corrosion inhibitors and supplemental coolant additives have presented many problems. Current practice involves the use of full scale engine tests to show that engine coolant inhibitors provide sufficient liner pitting protection. These are too time-consuming and expensive to use as the basis for industry-wide specifications. Ultrasonic vibratory test rigs have been used for screening purposes in individual labs, but these have suffered from poor reproducibility and insufficient additive differentiation. A new test procedure has been developed that reduces these problems. The new procedure compares candidate formulations against a good and bad reference fluid to reduce the concern for problems with calibration and equipment variability. Cast iron test coupons with well-defined microstructure and processing requirements significantly reduce test variability.
Technical Paper

A Big Size Rapid Compression Machine for Fundamental Studies of Diesel Combustion

1981-09-01
811004
As a basic tool for fundamental studies on combustion and heat transfer in diesel engines, a new rapid compression machine with a cylinder bore of 200 mm was developed which can realize in it a free diesel flame in a quiescent atmosphere, a diesel flame in a swirl, and a diesel flame impinging on the wall. The piston of this machine is driven by high pressure nitrogen, and its speed is controlled by a sophisticated hydraulic system. This paper describes the details of the mechanism and performances of the machine, and presents some examples of studies conducted with this machine.
Technical Paper

A Broad-Spectrum, Non-Metallic Additive for Gasoline and Diesel Fuels: Performance in Gasoline Engines

1989-02-01
890214
This paper describes the performance of a single, multifunctional additive that alleviates many of the common gasoline and Diesel fuel problems. The additive has been deemed “substantially similar” by the EPA and thus may be used for bulk treatment of unleaded gasoline. Test data obtained from several independent laboratories are presented. The results show that the additive limits octane requirement increase (ORI) to an average of about 30% of that experienced when using untreated gasolines; reduces hydrocarbon emissions by the order of 10% or more; improves fuel economy approximately 1.5% - and often much more - in a variety of engines; and also reduces exhaust valve recession and combustion chamber deposits. The additive effects on Diesel engine performance and on combustion modification in both gasoline and Diesel engines will be reported later.
Technical Paper

A CFD APPROACH TO DIESEL ENGINE COMBUSTION CHAMBER RESONANCE

2007-09-16
2007-24-0043
The resonance due to the oscillation of burned gases in the combustion chamber is particularly important in DI diesel engines. This effect can be an important excitation source of the engine block during the combustion process. Experimental studies have many limitations. Among them, the difficulty of placing different pressure transducers in the combustion chamber and the high cost of operating and mounting in an experimental room, are the most relevant. Therefore additional methodologies can be of interest. In this paper a computational fluid dynamics (CFD) approach for the study of DI automotive Diesel engine resonance is presented. With this methodology it is possible to simulate the resonance phenomenon due to the auto-ignition and the combustion process by means of energy sources. During the calculation the pressure evolution is registered in different points of the domain, and this provides the relevant information about the effects of the bowl geometry on the resonance.
Technical Paper

A CFD Investigation into the Effects of Intake Valves Events on Airflow Characteristics in a Motored 4-Valve Engine Cylinder with Negative Valve Overlapping

2007-09-16
2007-24-0032
This paper presents a computational study of the airflow features within a motored 4-valve direct injection engine cylinder. An unconventional intake valve strategy was investigated; whereby each valve on the pair of intake valves was assumed to be actuated with different lifts and duration. One of the intake valves was assumed to follow a high-lift long duration valve-lift profile while the other was assumed to follow a low-lift short duration valve-lift profile. The pair of exhaust valves was assumed to be actuated with two identical low-lift short duration valve-lift profiles in order to generate the so-called negative valve overlapping (NVO). The in-cylinder flow fields developed with such intake valve strategy were compared to those produced in the same engine cylinder but with the application of identical low-lift short duration intake valve events.
Journal Article

A CFD Study of Fuel Evaporation and Related Thermo-fluid Dynamics in the Inlet Manifold, Port and Cylinder of the CFR Octane Engine

2012-09-10
2012-01-1715
Knock in Spark Ignited (SI) engines has received significant research attention historically since this phenomenon effectively restricts the compression ratio and hence the thermal efficiency of the engine. The latent heat of vaporization (LHV) of a fuel affects its knock resistance in production engines as well as affecting its Research Octane Number (RON) rating. The reason for this is that evaporative cooling of the fuel lowers in-cylinder gas temperatures resulting in reduced tendency for end-gas auto-ignition. Controlling of the fuel-air mixture temperature to 422 K at the inlet port as per the Motor Octane Number (MON) test method ensures full evaporation of the liquid fuel, and hence LHV is assumed to have little effect during this procedure. LHV therefore has a strong influence on a fuel's Octane Sensitivity (OS) - the difference between its RON and MON values.
Technical Paper

A CFD Study of Losses in a Straight-Six Diesel Engine

1999-03-01
1999-01-0230
Using a previously validated and documented CFD methodology, this research simulated the flow field in the intake region (inlet duct, plenum, ports, valves, and cylinder) involving the four cylinders (#1, #3, #4, #6) of a straight-six IC engine. Each cylinder was studied with its intake valves set at high, medium and low valve lifts. All twelve viscous 3-D turbulent flow simulation models had high density, high quality computational grids and complete domains. Extremely fine grid density were applied for every simulation up to 1,000,000 finite volume cells. Results for all the cases presented here were declared “fully converged” and “grid independent”. The relative magnitude of total pressure losses in the entire intake region and loss mechanisms were documented here. It was found that the total pressure losses were caused by a number of flow mechanisms.
Technical Paper

A CFD Study of a 4-Valved, Fuel Injected Two-Stroke Spark Ignition Engine

1993-03-01
930070
The CFD code KIVA is used in conjunction with a one-dimensional wave action program to simulate exhaust blowdown, in a study of the scavenging and combustion at different loads and constant engine speed, in a single cylinder 4 valved 2-stroke engine configuration, using in-cylinder fuel injection. Two combustion chamber geometries -- a stepped head and a pentroof, were used in this study. The stepped head geometry has a combustion chamber recessed in the cylinder head, and contains the intake valves. The vertical intake port configuration provides a well developed reversed loop flow in the engine cylinder. The pentroof combustion chamber is similar to those used in current 4 stroke engines(1)*. The computational study focuses on the effects of injector orientation, and the subsequent interaction between the fuel spray and ‘loop swirl’ of air in the engine cylinder, and on the resulting combustion characteristics and exhaust emissions.
Technical Paper

A COHERENCE MODEL FOR PISTON-IMPACT GENERATED NOISE

1979-02-01
790274
An experimental study was conducted to investigate piston-impact generated noise in diesel engines. A coherence model was used to represent the noise generating mechanisms of the engine. The model was applied to an in-line turbo-charged diesel engine. Frequency response functions were measured between the cylinder liner vibration and the engine noise, and between the combustion pressure and the engine noise. The noise coherent with piston impacts was separated from the noise coherent with combustion. Guidelines are presented showing how the results of the coherence model may be used for engine design and noise prediction.
Technical Paper

A COMPARISON OF EXPERIMENTAL AND ANALYTICAL STEADY STATE INTAKE PORT FLOW DATA USING DIGITAL PHYSICS

1999-03-01
1999-01-1183
A steady-state flowbench measures the mass and angular momentum flux (swirl and tumble) for a given cylinder head intake port design over varying valve lifts and pressure drops. From these two measurements, enhancements in volumetric efficiency and burnrate can be determined. This methodology, however, requires the production and experimental testing of multiple cylinder head castings or soft-prototypes. To help reduce the number of hardware design iterations, an analytical methodology has been developed which uses a new computational fluid dynamics (CFD) simulation tools called PowerFLOW. From a solid model of the cylinder head, PowerFLOW uses automeshing which produces a 10 million Cartesian volume mesh in 4 CPU hrs. The lattice Boltzmann technique used by PowerFLOW is inherently parallel resulting in steady-state results on this mesh in 36 CPU hrs. This paper present a comparison of numerically obtained mass flow rates from PowerFLOW to experimental flowbench data.
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