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Technical Paper

Visualization of Mixture Preparation in a Port-Fuel Injection Engine During Engine Warm-up

The fuel injection process in the port of a firing 4-valve SI engine at part load and 25°C head temperature was observed by a high speed video camera. Fuel was injected when the valve was closed. The reverse blow-down flow when the intake valve opens has been identified as an important factor in the mixture preparation process because it not only alters the thermal environment of the intake port, but also strip-atomizes the liquid film at the vicinity of the intake valve and carries the droplets away from the engine. In a series of “fuel-on” experiments, the fuel injected in the current cycle was observed to influence the fuel delivery to the engine in the subsequent cycles.
Technical Paper

Visualization of Preflame and Combustion Reactions in Engine Cylinders

In-cylinder reactions of several internal combustion engine configurations were investigated using a highspeed four-spectral infrared (IR) digital imaging device. The study was conducted with a greater emphasis on the preflame processes by mutually comparing results from different engine-fuel systems. The main features of the methods employed in the study include that the present multi-spectral IR imaging system permits us to capture progressively changing radiation emitted by new species produced in-cylinder fuel-air mixtures prior to being consumed by the heat-releasing reaction fronts. The study of the Diesel or compression-ignition (CI) engine reactions was performed by varying several parameters, e.g. injection pressures, intake air temperature, fuel air ratio, and the start of injection.
Technical Paper

Volumetric Efficiency Investigation with Anhydrous and Hydrous Ethanol on a Port Fuel Injection Spark Ignition Engine

Port fuel injection - PFI - engines are widely available and the calibrations of fuel models are well defined. Modern flex-fuel engines are designed to work with different fuels and a mix of them. However, Brazil’s ethanol is composed of anhydrous Ethanol mixed with 8% distilled water, making it distinct in relation of composition. In a PFI, the fuel mass is mixed to the air mass before entering the combustion chamber in order to keep the mixture most uniform as possible. In this process, heat exchange and partial pressure variation are present and this may lead to volumetric efficiency modification. However, measurement errors may be introduced from the indirect measurement method if it does not considers water content and combustion efficiency to determine volumetric efficiency.
Technical Paper

Wall Impingement Process of a Multi-Hole GDI Spray: Experimental and Numerical Investigation

The Direct Injection (DI) of gasoline in Spark Ignition (SI) engines is very attractive for fuel economy and performance improvements in spark ignition engines. Gasoline direct injection (GDI) offers the possibility of multi-mode operation, homogeneous and stratified charge, with benefits respect to conventional SI engines as higher compression ratio, zero pumping losses, control of the ignition process at very lean air-fuel mixture and good cold starting. The impingement of liquid fuel on the combustion chamber wall is generally one of the major drawbacks of GDI engines because its increasing of HC emissions and effects on the combustion process; in the wall guided engines an increasing attention is focusing on the fuel film deposits evolution and their role in the soot formation. Hence, the necessity of a detailed understanding of the spray-wall impingement process and its effects on the fuel distribution. The experimental results provide a fundamental data base for CFD predictions.
Technical Paper

Wall-Wetting Theories Applied to the Transient Operation of a Single Cylinder Four-Stroke Gasoline Engine

This paper reports on the preliminary investigation of the identification of a method to model the transient operation of a single cylinder four-stroke gasoline engine. During a transient the response of an engine and the actual fuel mixture delivered to the engine are significantly affected by the behaviour of the fuel injected into the inlet manifold. In the past, different wall-wetting theories have been developed to model and attempt to resolve this problem and one of the most definitive is investigated here along with two other theories developed at QUB. A steady state computer model of a single cylinder four-stroke spark-ignition research engine was written and validated. The three different wall-wetting theories were studied and each individually integrated into the steady state model. This allowed simulated transients to be performed on the computer and the results generated to be compared with firing transient tests.
Technical Paper

Warm-Up Characteristics of Surface Temperatures in an I.C. Engine Measured by Thermal Imaging Technique

The warm-up characteristics of a spark-ignition engine significantly affect fuel consumption and emissions from cars. A thermal imaging technique has been applied to measure the cylinder head surface temperature and piston surface temperature of an internal combustion engine simultaneously. The two-dimensional thermal images of the cylinder head surface temperature were viewed through an infra-red transmitting window mounted in the piston. The piston surface temperature was measured by painting black two small areas of the window's top surface. The similar thermal characteristics of the window material (silicon) to those of a normal piston and good heat transfer between the window and the piston provided realistic operation conditions. The mean and extreme values of the inlet valve, exhaust valve, two other areas of the cylinder head surface and window surface temperatures were measured from the thermal images during the first two minutes of the engine start.
Technical Paper

Warmup Characteristics of a Spark Ignition Engine as a Function of Speed and Load

The warmup characteristics of an engine have an important impact on a variety of design issues such as performance, emissions and durability. A computer simulation has been developed which permits a detailed transient simulation of the engine warmup period from initial ambient conditions to a fully warmed up state. The simulation combines a detailed crankangle-by-crankangle calculation of in-cylinder processes and of engine air flow, with finite element heat conduction calculations of heat transfer from the gases, through the structure to the coolant. The paper describes one particular application of the simulation to the warmup of a 2.5ℓ spark ignited engine from cold start to a fully warmed up state at several speeds ranging from 1600 to 5200 rpm and loads ranging from 25% to 100% at each speed. The response of structure temperatures, charge temperature at IVC and of the exhaust temperature has been calculated and is documented in terms of characteristic warmup times.
Technical Paper

Waste Cooking Oil Conversion to Biodiesel in Presence of Solid K3PO4 as Catalyst

Biodiesel obtained from the transesterification of vegetable oil or animal fat is a promising renewable green alternative fuel for compression ignition engines. Compression ignition engines are particularly suitable for medium-to-large road, rail and marine use. This is due to their excellent efficiency and longer operation life which is about twice as much as that for spark ignition engines. The replacement of conventional diesel fuel with biodiesel fuel is an attractive solution since the latter is regarded as a renewable, biodegradable, non-poisonous, and oxygenated fuel. However, existing production technologies offer less competitive prices than petroleum-derived diesel due to high input feed and biodiesel purification costs. Non-edible vegetable oils such as waste cooking oils may be used as cheaper substitutes to virgin edible vegetable oils in the feed stream.
Technical Paper

Waste Heat Recovery In Truck Engines

Truck engines currently reject up to 40% of the total fuel energy in the exhaust. Because of increasing petroleum costs there is growing interest in techniques that can utilize this waste heat to improve overall system efficiency. This paper examines and compares improvement in fuel economy for a broad spectrum of truck engines and waste heat utilization concepts. The engines considered are the Diesel, spark ignition, gas turbine, and Stirling. Principal emphasis is placed on the turbocharged four-stroke Diesel engine. Because of increased exhaust energy and a large potential improvement in performance, the still-to-be-developed “adiabatic” Diesel is also examined. The waste heat utilization concepts include preheating, regeneration, turbocharging, turbocompounding, and Rankine engine compounding. Predictions are based on fuel-air cycle analyses, computer simulation, and engine test data. All options are compared on the basis of maximum theoretical improvement.
Technical Paper

Waste-Gate Turbocharging Control in Automotive SI Engines: Effect on Steady and Unsteady Turbine Performance

Turbocharging is becoming a key technology for automotive spark ignition engines (fed with both liquid and gaseous fuel) as a support to the downsizing concept in order to reduce fuel consumption and exhaust emissions. A waste-gate valve is usually fitted as turbocharger control system in these applications, due to its ability to work at very high exhaust gas temperatures. However, not much information is generally available on turbine behaviour in the opened waste-gate area. This paper presents the results of an experimental study developed on a waste-gated turbocharger for downsized SI automotive engines, performed on the test rig operating at the University of Genoa (Italy), extended both to steady and unsteady flow operation. Mass flow through the by-pass valve and turbine impeller was measured at different waste-gate settings in steady flow conditions.
Technical Paper

Water Injection Applicability to Gasoline Engines: Thermodynamic Analysis

The vehicle WLTP and RDE homologation test cycles are pushing the engine technology toward the implementation of different solutions aimed to the exhaust gases emission reduction. The tightening of the policy on the Auxiliary Emission Strategy (A.E.S.), including those for the engine component protection, faces the Spark Ignited (S.I.) engines with the need to replace the fuel enrichment as a means to cool down both unburnt mixture and exhaust gases to accomplish with the inlet temperature turbine (TiT) limit. Among the whole technology solutions conceived to make SI engine operating at lambda 1.0 on the whole operation map, the water injection is one of the valuable candidates. Despite the fact that the water injection has been exploited in the past, the renewed interest in it requires a deep investigation in order to outcome its potential as well as its limits.
Journal Article

Water Injection Benefits in a 3-Cylinder Downsized SI-Engine

With progressing electrification of automotive powertrains and demands to meet increasingly stringent emission regulations, a combination of an electric motor and downsized turbocharged spark-ignited engine has been recognized as a viable solution. The SI engine must be optimized, and preferentially downsized, to reduce tailpipe CO2 and other emissions. However, drives to increase BMEP (Brake Mean Effective Pressure) and compression ratio/thermal efficiency increase propensities of knocking (auto-ignition of residual unburnt charge before the propagating flame reaches it) in downsized engines. Currently, knock is mitigated by retarding the ignition timing, but this has several limitations. Another option identified in the last decade (following trials of similar technology in aircraft combustion engines) is water injection, which suppresses knocking largely by reducing local in-cylinder mixture temperatures due to its latent heat of vaporization.
Technical Paper

Water Injection Effects In A Single-Cylinder CFR Engine

Though analysed by a few researches, the practice of water injection in Spark Ignition Engines (SI-ICE) does not yield homogeneous results, owing to various typologies of engines used for experiments. In this paper the effects of water injection in the intake pipe are investigated from both a theoretical and experimental viewpoint. Pressure vs. time diagrams were recorded on a single-cylinder CFR engine at AGIP PETROLI, Priolo (CT). Tests were performed according to Research and Motor Method (ASTM). Water was supplied by a continuous injection system inclusive of comparatively high pressure pump. The engine was fed with low O.N. base gasoline (cheap products, intermediate of refinery processes). The water to fuel mass flow rate ratio was varied in the range 0 to 1.5. The NOx emissions measurements confirm the tremendous effectiveness of water injection in reducing the engine environmental impact.
Journal Article

Water Injection as an Enabler for Increased Efficiency at High-Load in a Direct Injected, Boosted, SI Engine

In a Spark-Ignited engine, there will come a point, as load is increased, where the unburned air-fuel mixture undergoes auto-ignition (knock). The onset of knock represents the upper limit of engine output, and limits the extent of engine downsizing / boosting that can be implemented for a given application. Although effective at mitigating knock, requiring high octane fuel is not an option for most markets. Retarding spark timing can extend the high load limit incrementally, but is still bounded by limits for exhaust gas temperature, and spark retard results in a notable loss of efficiency. Likewise, enriching the air-fuel mixture also decreases efficiency, and has profound negative impacts on engine out emissions. In this current work, a Direct-Injected, Boosted, Spark-Ignited engine with Variable Valve Timing was tested under steady state high load operation. Comparisons were made among three fuels; an 87 AKI, a 91 AKI, and a 110 AKI off-road only race fuel.
Technical Paper

Water Injection in IC - SI Engines to Control Detonation and to Reduce Pollutant Emissions

In this paper the effects of water injection in the intake pipe of a single-cylinder standard CFR engine are investigated from an experimental viewpoint. Research was carried out at AGIP Petroli and ISAB ERG Refineries of Priolo Gargallo (SR). Tests were performed according to ASTM Research and Motor Method. Water was supplied by a continuous and pulsed injection system. The engine was fed with low Octane Number (O.N.) base gasoline (cheap products, intermediate of refinery processes). The water to fuel mass flow rate ratio was varied in the range 0 to 2. Measurements of O.N. have shown that water injection virtually increases the water/fuel mixture O.N. and that it is possible to obtain a correct run feeding the engine with a low octane number fuel. The pollutant emissions measurements confirm the effectiveness of water injection in reducing the engine environmental impact.
Journal Article

Water Injection to Enhance Performance and Emissions of a Turbocharged Gasoline Engine under High Load Condition

The potential benefits of water injection on performance and emissions were investigated on a downsized PFI twin-cylinder turbocharged spark ignition engine. Experiments were carried out at high load condition (~15.5 bar IMEP) within the engine speed range from 3500 to 4500rpm with a step of 500 rpm. For each test case the effect of the injected water quantity on combustion and exhaust emissions was investigated by sweeping from 10%w to 30%w the water to gasoline ratio. The water was injected at the same timing as the gasoline by a low pressure injection system external controlled. Tests were performed at WOT conditions exploring, for each operating condition, a spark sweep from knock-free up to knock-limited operation. Compared to the full gasoline reference case, the water injection allowed to advance extensively the spark timing without knock occurrence. The 20% water to gasoline mass fraction gave the best improvements in terms of IMEP.
Technical Paper

Water Injection to Improve Direct Injection Spark Ignition Engine Efficiency

The increasing use of downsized turbocharged gasoline engines for passengers cars and the new European homologation cycles (WLTC and RDE) both impose an optimization of the whole engine map. More weight is given to mid and high loads, thus enhancing knock and overfueling limitations. At low and moderate engine speeds, knock mitigation is one of the main issues, generally addressed by retarding spark advance thereby penalizing the combustion efficiency. At high engine speeds, knock still occurs but is less problematic. However, in order to comply with thermo-mechanical properties of the turbine, excess fuel is injected to limit the exhaust gas temperature while maximizing engine power, even with cooled exhaust manifolds. This also implies a decrease of the combustion efficiency and an increase in pollutant emissions. Water injection is one way to overcome both limitations.
Journal Article

Water Injection: a Technology to Improve Performance and Emissions of Downsized Turbocharged Spark Ignited Engines

Knock occurrence and fuel enrichment, which is required at high engine speed and load to limit the turbine inlet temperature, are the major obstacles to further increase performance and efficiency of down-sized turbocharged spark ignited engines. A technique that has the potential to overcome these restrictions is based on the injection of a precise amount of water within the mixture charge that can allow to achieve important benefits on knock mitigation, engine efficiency, gaseous and noise emissions. One of the main objectives of this investigation is to demonstrate that water injection (WI) could be a reliable solution to advance the spark timing and make the engine run at leaner mixture ratios with strong benefits on knock tendency and important improvement on fuel efficiency.
Technical Paper

Water Tolerability of Methanol-Gasoline Blends (Phase Separation and SI Engine Performances)

The most important problem arizing from methanol-gasoline is the phase separation caused by the presence of very small quantities of water. Two or three layers showing cloud points were observed after the addition of a small quantity of water, and their separation ratio could not be ascribed to their original blends ratio of methanol and gasoline. The greater the increase methanol content, the greater the increase in the amount of the lower layer and the limit of water absorption. Engine dynamometer tests were conducted on a 0.33L, 4-stroke spark ignition engine to get the effects of supplying the phase separation fuels on engine performances. The results of the separation behavior and the engine dynamometer tests are presented here and discussed.
Technical Paper

Water-Gasoline Fuels-Their Effect on Spark Ignition Engine Emissions and Performance

Single-cylinder engine tests, an analytical engine cycle simulation, and automobile tests were employed to study the effects of supplementing gasoline with water for use in spark ignition engines. Factors examined include: the method of water addition (both water-in-gasoline emulsions and direct manifold water addition), antiknock characteristics with water addition, MBT spark requirement, indicated engine efficiency, engine cooling requirement, exhaust emissions, volumetric efficiency, lean operating limit, smoke level, exhaust temperature, and vehicle driveability. Among the negative aspects of water addition were increased hydrocarbon emissions and decreased vehicle driveability. Also, the polyoxyethylene type of emulsifier used in the water-in-gasoline emulsions, gave poor fuel stability and caused a rapid buildup of engine deposits. However on the positive side, water-gasoline fuels have higher octane ratings and decrease nitric oxide emissions.