The influence of ethanol content in gasoline on speciated emissions from a direct injection stratified charge (DISC) SI engine is assessed. The engine tested is a commercial DISC one that has a wall guided combustion system. The emissions were analyzed using both Fourier transform infrared (FTIR) spectroscopy and conventional emission measurement equipment. Seven fuels were compared in the study. The first range of fuels was of alkylate type, designed to have 0, 5, 10 and 15 % ethanol in gasoline without changing the evaporation curve. European emissions certification fuel was tested, with and without 5 % ethanol, and finally a specially blended high volatility gasoline was also tested. The measurements were conducted at part-load, where the combustion is in stratified mode. The engine used a series engine control unit (ECU) that regulated the fuel injection, ignition and exhaust gas recirculation (EGR).
The fuel direct injection in SI engines is demonstrating a remarkable potential regarding the reduction of consumption and pollutant emission. Nevertheless, the management of the mixture formation “in-cylinder” - in conditions of a short duration and of a complex fluid dynamic configuration imposes both an accurate modeling and an exact control of the process. The problem gains on complexity when considering the use of alternative fuels which becomes more and more a subject of actuality. The paper presents a comparative analysis of mixture formation process and engine performances, when applying direct injection of gasoline, respectively of ethanol in a four-stroke single cylinder SI engine. The modulation of the injection rate shape is the result of a fuel high pressure wave, generated in a pressure pulse direct injection system.
The use of modularized aluminum extrusions for the block, crankcase and head in small engine systems allows a range of engines to be mass produced without resort to casting for the stationary components. The use of modern accurately dimensioned extrusions greatly reduces the machining required. The versatility and strength of extruded aluminum alloys enables the elimination of load bearing threads and most other finish machining, thus significantly reducing the labor costs of manufacture. A range of strokes and hence of different capacity engines can be produced from a single extrusion form. For extended life, bores can be coated with a variety of finishes, including simple anodizing. Extrusion technology allows cost-effective engines to be manufactured with a significantly lower investment than with other technologies.
The recent emergence of production Gasoline Direct Fuel Injection (GDFI) engines into the world markets offers the promise of both improved fuel economy and emissions for 4-stroke Spark Ignition (SI) engines. However with all new technologies there are new challenges that accompany them. The subjects of fuel and intake system and combustion chamber deposits in Port Fuel Injected (PFI) SI engines are well researched and documented. Today only a small amount of specific research exists for GDFI engines [1,2,3,4]. In any case, based on available PFI deposit literature it is possible to make a number of observations about the likely GDFI fuel and intake system deposit issues and their effect on fuel economy, exhaust emissions and performance during a lifetime of service.
Piston-wetting effects are investigated in an optical direct-injection spark-ignition (DISI) engine. Fuel spray impingement on the piston leads to the formation of fuel films, which are visualized with a laser-induced fluorescence (LIF) imaging technique. Oxygen quenching is found to reduce the fluorescence yield from liquid gasoline. Fuel films that exist during combustion of the premixed charge ignite to create piston-top pool fires. These fires are characterized using direct flame imaging. Soot produced by the pool fires is imaged using laser elastic scattering and is found to persist throughout the exhaust stroke, implying that piston-top pool fires are a likely source of engine-out particulate emissions for DISI engines.
An optical access engine was used to image the liquid film evaporation off the piston of a simulated direct injected gasoline engine. A directional injector probe was used to inject liquid fuel (gasoline, i-octane and n-pentane) directly onto the piston of an engine primarily fueled on propane. The engine was run at idle conditions (750 RPM and closed throttle) and at the Ford World Wide Mapping Point (1500 RPM and 262 kPa BMEP). Mie scattering images show the liquid exiting the injector probe as a stream and directly impacting the piston top. Schlieren imaging was used to show the fuel vaporizing off the piston top late in the expansion stroke and during the exhaust stroke. Previous emissions tests showed that the presence of liquid fuel on in-cylinder surfaces increases engine-out hydrocarbon emissions.
Piston wetting can be isolated from the other sources of HC emissions from DISI engines by operating the engine predominantly on a gaseous fuel and using an injector probe to impact a small amount of liquid fuel on the piston top. This results in a marked increase in HC emissions. All of our prior tests with the injector probe used California Phase 2 reformulated gasoline as the liquid fuel. In the present study, a variety of pure liquid hydrocarbon fuels are used to examine the influence of fuel volatility and structure. Additionally, the exhaust hydrocarbons are speciated to differentiate between the emissions resulting from the gaseous fuel and those resulting from the liquid fuel. It is shown that the HC emissions correspond to the Leidenfrost effect: fuels with very low boiling points yield high HCs and those with a boiling point near or above the piston temperature produce much lower HCs.
The exploitation of full load capabilities of DI gasoline engines requires at least the same degree of effort as in MPFI engine development. An optics based sensor and sensing technique is presented, which together with conventional pressure indicating provides identification of self ignition centers as the engine is operated under knock or borderline knock conditions. The knock location sensor is configured as a spark plug providing the relevant spark plug properties together with the multichannel optical access into the upper part of the combustion chamber. Functionality and sensitivity of this sensing technique are demonstrated and results for combustion system development are shown.
Using methanol as a fuel, this study examines the chemical-kinetics mechanism responsible for the enhancement of combustion in I.C. engines due to intermediate and radical chemical species produced in micro-chambers of Sonex Combustion System (SCS) pistons. This homogeneous combustion enhancement was first shown experimentally (in 1991) to be capable of enabling an IC engine to operate stably and smoke free on methanol over an entire engine map while using a compression ratio of only 17:1 and without a spark or other assists. The distinction is made between thermally induced variants of homogeneous combustion: HCCI and ATAC; and intermediate species/radical induced homogeneous combustion: LAG and SCRl (Stratified Charge Radical Ignition).
In the field of automotive gasoline engines, new products aiming at greater fuel economy and cleaner exhaust gases are under development with the aim of preventing environmental destruction. Severe ignition environments such as lean combustion, stronger charge motion, and large quantities of EGR require ever greater combustion stability. In an effort to meet these requirements, an iridium plug has been developed that achieves high ignitability and long service life through reduction of its diameter, using a highly wear-resistant iridium alloy as the center electrode.(1)(2) Recently, direct injection engines have attracted attention. In stratified combustion, a feature of the direct injection engine, the introduction of rich air-fuel mixtures in the vicinity of the plug ignition region tends to cause carbon fouling. This necessitates plug carbon fouling resistance.
A systematic experimental investigation was undertaken to compare the fuel consumption and exhaust emissions of a production SI engine fueled by either gasoline or compressed natural gas (CNG). The investigation was carried out on a two-liter four-cylinder engine featuring a fast-burn pent-roof chamber, one centrally located spark plug, four valves per cylinder and variable intake-system geometry. The engine was originally designed at Fiat to operate with unleaded gasoline and was then converted at Politecnico di Torino to run on CNG. A Magneti Marelli IAW electronic module for injection-duration and spark-advance setting was used to obtain a carefully controlled multipoint sequential injection for both fuels.
A fuel fractionating system is designed and commissioned to separate standard gasoline fuel into two components by evaporation. The system is installed on a Ricardo E6 single cylinder research engine for testing purposes. Laboratory tests are carried out to determine the Research Octane Number (RON) and Motoring Octane Number (MON) of both fuel fractions. Further tests are carried out to characterize Spark-Ignition (SI) and Controlled Auto-Ignition (CAI) combustion under borderline knock conditions, and these are related to results from some primary reference fuels. SI results indicate that an increase in compression ratio of up to 1.0 may be achieved, along with better charge ignitability if this system is used with a stratified charge combustion regime. CAI results show that the two fuels exhibit similar knock-resistances over a range of operating conditions.
A predictive technique aimed at investigating the behaviour of intake and exhaust systems of internal combustion engine and at evaluating their influence on engine breathing and radiated noise is herewith presented. Such a technique is based on coupling a time domain gas dynamic model (composed of zero-dimensional, one-dimensional and three-dimensional methods) with a frequency domain linear acoustic analysis (transfer matrix method); thus a realistic prediction of complete engine systems is realised by adopting in each region the most appropriate method, according to the main features of the phenomena involved. The whole procedure has been applied to the intake system of an automotive engine and the results regarding different operative conditions are presented.
The design of an air intake system has to be a compromise between several system targets. In the past these conflicts were solved with experimental test on the first prototype parts. To shorten the development times more and more computational programs in the concept phase are used. 1D simulation programs are based on the transfer matrix method or use the output of gas exchange programs to simulate the acoustic behavior of air intake systems. These tools do usually neglect the coupled fluid/structure modes. Measurements on a simple air cleaner design have shown that these coupling can not be ignored on typical air cleaner designs. The difference between internal and external pressure leads to an increase of the air cleaner volume which shifts the first resonance to a lower engine speed. This paper shows a method which can be used in 1D simulation programs to allow the prediction of orifice noise of air intake systems.
The spark ignition engine is a prime source of vibration energy. NVH disturbances generated by the engine ultimately reach the customer in the form of objectionable noise or NVH. Exhaust Manifolds are one of the many sources of noise contributors among the engine components. Often, the exhaust manifold is identified as a source of objectionable NVH late in the design and development process. Due to the lack of an upfront NVH analysis tool, a new CAE NVH methodology for evaluating new exhaust manifold designs has been investigated and developed by the Ford Motor Company's V-Engine CAE and Exhaust Manifold Design Sections. This new CAE methodology has been developed to compare the NVH performance of current production exhaust manifolds to new design levels. Mechanical induced radiated shell noise is the predominate cause of objectionable NVH in exhaust manifolds.
Silencers are a very effective way to reduce two of the most severe kinds of turbocharger noises, called “pulsation” noise and “blow” noise. PSA has developed its own silencer design based on a combination of a Herschel-Quincke tube and two quarter-wave resonators. The new device has a transmission loss of over 15 dB from 1600 to 3400 Hz. It will be first applied on the 2001 Peugeot 406 and Citroën C5.
A newly developed OHC (Over-Head Camshaft) prototype of a six-cylinder in-line diesel engine (with bore size: 114mm, stroke size: 130mm) was studied, comparing with the previous version of OHV (Over-Head Valve) type engine (with bore size: 110mm, stroke size: 130mm). It was found that the new type of cylinder block (with 130.8 kg of mass) has significantly lower natural frequencies than those for the previous type of cylinder block (with 133.2 kg of mass). Furthermore, slightly more predominant engine noise and vibration were induced in the new engine. The vibration behavior and the excitation force transmission characteristics were investigated by EMA (Experimental Modal Analysis). We performed a series of impact tests for (1) free-free cylinder block, (2) free-free crankshaft substructure with torsional damper and flywheel attached, and (3) the case where (1) and (2) are assembled together.
The dynamic behaviors of power-plant have much effect on interior noises and vibrations of passenger cars, especially, in the frequency range below 1000 Hz. So it is very important to estimate the vibrations of power-plant at the design stage. To predict the dynamic behaviors of power-plant including the rotating elastic crankshaft system, the time domain dynamic simulation methods have been applied, however such analyses require much time and resource of computer. In this report, the exciting forces to the cylinder block are derived in the frequency domain from both the dynamic stiffness of bearing oil films and the dynamic displacements of crankshaft journals, so that the computation time is reduced considerably. To estimate the displacements of the crankshaft journals, the vibrations of an engine crankshaft system including crank journal oil films under firing conditions are calculated using the dynamic stiffness matrix method in the frequency domain.
Serpentine belt system has been widely used during past years to drive automotive accessories like power steering, alternator, and A/C compressor from a crankshaft pulley. Instead of using multiple belt drives, the serpentine belt system uses a multi-rib flat belt, which wraps around several idlers and accessory pulleys. This design requires the use of a tensioning device to maintain adequate belt tension for preventing slip. Crankshaft torsional vibrations can lead to excessive rotational vibrations in poorly designed accessory systems. This can lead to undesirable noise and excessive slip, which can hamper the belt and bearing life. The value of these rotational frequencies and system response is of utmost interest to the accessory drive designer. While it is not practical to shift these rotational frequencies out of the operating range of an engine, a belt layout with these frequencies at non-dwell engine speed is highly desirable.