Search Results

Cycle resolved fuel droplet dynamics measurements in the inlet port of an S.I. engine were performed under firing conditions in order to study real dynamic effects in the fuel flow to the engine. A Phase Doppler Particle Analyzer (PDPA) was used to detect the droplet size and velocity. The optical access was through a glass window in the bottom of the intake channel. The PDPA was synchronised with the engine combustion cycle in order to study the results in the engine frequency domain. The measurements were performed over the cross section of the channel. Different injection timing and engine running conditions were investigated, using standard unleaded gasoline. The results show that, during the camshaft's overlap period, there exists a “push-back” droplets effect, due to the pressure difference between the inlet manifold and the cylinder, that transports droplets far back in the inlet manifold.

The droplet velocity, size and distributions of iso-octane fuel from single hole and twin jet air-assist injectors have been measured by phase Doppler velocimetry in the pent-roof for two cylinder head designs of firing four-valve engines running at 1500 rpm, together with the airflow during induction and compression. The use of the twin jet air-assist injector together with the introduction of a transfer-passage between the two intake ports of a Honda VTEC-E valve train arrangement resulted in reduction in ISNOx and COV-1mep of the order of half of those with the single hole injector design without a transfer passage. Droplets, for both heads and injectors, having passed the inlet valves, impinged directly onto the sleeve opposite to their entry without striking the exhaust valves and had velocities up to 30 m/s and Sauter mean diameters which varied from 20 to 50pm.

An experimental study was made to investigate the spray characteristics of high pressure fuel injectors for direct-injection gasoline engines. The global spray development process was visualized using two-dimensional laser Mie scattering technique. The spray atomization process was characterized by Phase Doppler particle analyzer. The transient spray development process was investigated under different fuel injection conditions as a function of the time after the fuel injection start. The effects of injector design, fuel injection pressure, injection duration, ambient pressure, and fuel property on the spray breakup and atomization characteristics were studied in details. Two clear counter-rotating recirculation zones are observed at the later stage or after the end of fuel injection inside the fuel sprays with a small momentum. The circumferential distribution of the spray from the large-angle injector is quite irregular and looks like a star with several wings projected out.

The conversion of spark ignited and compression ignited engines to run on natural gas is established technology Engines have also been designed and built specifically for natural gas These engines have been used primarily in stationary applications with relatively constant operating conditions More recently, environmental pressures and economic considerations have made the use of natural gas attractive for transportation applications The urban transit bus population is particularly well suited to compressed natural gas fueling The basic engine designs for stationary natural gas service and conventionally fueled (diesel and gasoline) transportation service are similar Differences in operating conditions and maintenance practices have resulted in two distinct lubricant product groups Stationary natural gas engine lubricants tend to be high viscosity monograde formulations with a low ash content Lubricants for conventionally-fueled transportation applications are frequently multigrades with considerably higher ash content The lubricant needs for natural gas in transportation applications may not be adequately met with the lubricant product groups widely usable for stationary natural gas or conventionally fueled transportation Lubricant products have been designed to combine features identified as desirable for natural gas fueling and the needs of transportation usage The performance of these products is supported by laboratory engine data

The concept of long drain super high performance diesel engine oil [SHPDO] though European in origin has emerged as a trend of relevance in the Indian context. This is not only due to the demands of commercial fleets for extended drain periods but also because of close similarities between Indian and European diesel engine designs. This has necessitated the development of an SHPDO with minimum performance conforming to CCMC D5 DB 228 3 and additional features to address the requirements of typical Indian operating conditions. This paper describes the selection of a superior SHPDO formulation using laboratory bench and performance engine tests, followed by field trials. Safe drain period of ∼ 40 000 kms has been established by statistical analysis of the field data generated in services typical of city and sub-urban operations.

This paper presents a special optical fiber technique which allows to measure temperatures in SI engines using the emission bands or respectively emission lines of the temperature radiation of diatomic molecules. The measurement technique enables the detection of average temperature in a small volume element. These temperatures are used to determine the local NO concentrations using the extended Zeldovich-mechanism. First, theoretical background of both temperature and NO-determination and measurement technique including optical fiber sensors are described. Finally, the temperature and NO dependence versus crank angle are presented and discussed at different combustion chamber locations for different engine operating conditions.

The object of this paper is to present a new way of analyzing in-cylinder velocity measurements. The technique is called Discrete Wavelet Transform (DWT) and it is similar to Fast Fourier Transform (FFT) with one important difference it is possible to obtain both time localized and frequency resolved information. This paper demonstrates the use of DWT calculations on in-cylinder LDV flow measurements for different combustion geometries in a natural gas converted truck engine. It will furthermore provide some information about how DWT can be used with in-cylinder measurements in the future.

The process of autoignition in an internal combustion engine cylinder produces large amplitude high frequency gas pressure waves accompanied by significant increases in gas temperature and velocity, and as a consequence large convective heat fluxes to piston and cylinder surfaces. Extended exposure of these surfaces to autoignition, results in their damage through thermal fatigue, particularly in regions where small clearances between the piston and cylinder or cylinder head, lie in the path of the oscillatory gas pressure waves. The ability to predict spatial and temporal' variations in cylinder gas pressure, temperature and velocity during autoignition and hence obtain reasonable estimates of surface heat flux, makes it possible to assess levels of surface fatigue at critical zones of the piston and cylinder head, and hence improve their tolerance to autoignition.

The SI engine combustion model LI-CFM introduced by Boudier et, al. (1992) [8] is extended to deal with actual engines. New models are proposed to simulate ignition with convection at the spark and flame-wall interaction. The scalar properties of the unburnt gases within the combustion zone are computed. This allows for the computation of flame propagation in temperature, fuel and residual gas stratified charges. A model for NO and CO formation is introduced. It is based on a conditional burnt/unburnt averaging of the reaction rates. Pollutants are created at the flamelet level and evolve in the burnt, gases using a mixed equilibrium/kinetic scheme. All these physical models are implemented in a multi-block version of the Kiva 2 code, KMB. This code is used to simulate a 4-valve engine including intake ports. Initial and boundary conditions are obtained from a ID acoustic code.

A newly developed piece-wise method for calculating the effects of near-wall turbulence on the transport of enthalpy and hence the thermal boundary layer temperature profile in “motored” spark ignition engines has been compared with methods that have previously been employed in the development of expressions for the gas-wall interface heat flux. Near-wall temperature profiles resulting from the inclusion of the respective expressions in a “quasi-dimensional” thermodynamic engine simulation have been compared and in one case show considerable differences throughout the compression and expansion strokes of the “motored” engine cycle. However, the corresponding heat fluxes calculated from the simulated temperature profiles all show good agreement with measured results.

In previous work the KIVA-II code has been modified to model modem DI diesel engines and their emissions of particulate soot and oxides of nitrogen (NOx). This work presents results from a program to further validate the NOx emissions models against engine experiments with a well characterized modern engine. To facilitate a simplified comparison with experiments, a single cylinder research version of the Caterpillar 3406 heavy duty DI diesel engine was retrofitted to run as a naturally-aspirated, propane-fueled, spark-ignited engine. The retrofit includes installing a low compression ratio piston with bowl, adding a gas mixer, replacing the fuel injector assembly with a spark plug assembly and adding spark and fuel stoichiometry control hardware. Cylinder pressure and engine-out NOx emissions were measured for a range of speeds, exhaust gas residual (EGR) fractions, and spark timing settings.

Because only the unburned gases in the crevices can contribute to hydrocarbon emissions, a model was developed that can be used to determine the temporal and spatial histories of both burned gas and unburned gas flow into and out of the piston-liner crevices. The burned fraction in the top-land is primarily a function of engine design. Burned gases continue to get packed into the inter-ring volume until well after the end of combustion and the unburned fuel returned to the chamber from this source depends upon both the position of the top ring end gap relative to the spark plug and of the relative positions of the end gaps of the compression rings with respect to each other. Because the rings rotate, and because the fuel that returns to the chamber from the inter-ring crevice dominates the sources between BDC and IVO when conditions are unfavorable to in-cylinder oxidation, these represent two sources of variability in the HC emissions.

Unregulated emissions of reformulated diesel fuels (sulfur < 50 ppm, aromatics < 20 vol-%) were compared to the European EN590 specification fuel (sulfur < 500 ppm, aromatics < 35 vol-%) in three IDI passenger cars and one DI van using FTP and/or ECE/EUDC emission test procedures. The effect of reformulated diesel fuels on the mutagenicity of particulate soluble organic fraction (SOF) was studied. Fuel reformulation reduced particulate emissions in IDI cars. Reformulating fuel by decreasing heavier aromatics - without decreasing final boiling point - reduced particulate mutagenicity on emission basis. At low ambient temperature (-7°C) particulate PAH and mutagenic emissions increased compared to the standard ambient temperature (+22°C) with all fuels.

Unburned hydrocarbons from SI engine exhaust are a primary component of smog. At present they are attributed to several sources, one of which is the gap between piston and cylinder wall. Unburned charge is pushed into this crevice during the compression stroke. The crevice is narrow enough to quench the flame front, leaving unburnt crevice gases, so that during the power stroke, as the piston descends and the exhaust valve opens, these unburnt gases re-emerge. We have used reactive and non-reactive CFD simulations to study piston crevice outflow of unburnt fuel for a propane-fueled engine. We investigate the time and spatial dependence of the crevice outflows and the degree to which they either ignite or remain unburnt when they emerge into a time-varying, engine-like environment. We calculate rate of fuel consumption and depict fluid flows and plume shapes of the emerging gases.

This paper investigates the effects of the variations of turbulence characteristics and initial flame kernel center position on the cyclic combustion variations by means of quasi-dimensional turbulent entrainment combustion model. The turbulence intensity and turbulence integral length scale at spark ignition time in the model are determined by maximizing the agreement between the predicted and measured results such as pressure diagrams, mass fraction burned etc. With different values of the turbulence intensity and turbulence integral length scale at spark ignition time, the calculation of the cyclic combustion variations for the engine is carried out. In addition, the prediction of the effect of different flame kernel center positions on the cyclic combustion variations is also studied. Finally, some conclusions are drawn out about the importance of turbulence and initial flame kernel center position on the cyclic combustion variations for spark-ignition engine.

Because of their relatively low particulate make, lean burn natural gas vehicles (NGV's) are a viable approach to meeting the ULEV particulate standards in urban environments where NGV's are substituted for diesel powered buses and other fleet vehicles. Our experience with oxidation catalyst technology for natural gas vehicle emissions abatement has been consistent: that palladium based catalysts maintain excellent NMHC activity and particulate reduction, but methane activity, while initially very high, decreases within the first 50 hours of operation. This paper will show that sulfur oxides at sub-ppm concentrations diminish catalyst methane activity, and that inorganic ash components from the lubricating oil (P, Zn, Ca) do not significantly contribute to the initial catalyst deactivation. Using laboratory simulations, we explore systems approaches to increasing catalyst life.

This paper reports some results of a research carried out under part sponsorship of the Commission of the European Communities in the framework of the Joule II program. A twelve fuels matrix, derived from very different formulation techniques like hydrotreatment, Fisher Tropsch process, oligomerization and addition of oxygenated compounds to the straight run was tested. Istituto Motori performed tests on a turbocharged, after-cooled, direct injection diesel engine of two liter total displacement. It was equipped with an electronic E.G.R. system. Tests were performed in steady state conditions, representative of transient European schedules. Regulated and unregulated emissions was measured. Further tests were performed in cold conditions, the coolant temperature at the engine outlet was kept below 10°C in order to enhance the behavior of different fuels in producing regulated and unregulated emissions.

The Environmental Protection Agency (EPA) recently tested a clean diesel fuel developed by Dion & Sons for use in stationary sources. This fuel is known as Amber 363 in Southern California and its technology is licensed outside of the Southern California area to Shell Oil Products Company for use as a stationary source fuel. The fuel, hereafter referred to as “Shell LOW NOX Fuel,” was tested in a 1990 model year heavy heavy-duty diesel engine using both the transient Federal Test Procedure (FTP) for on-highway heavy-duty engines, the steady-state FTP for nonroad heavy-duty engines, and the steady-state generator set test cycle. For each test, EPA measured hydrocarbon (HC), carbon monoxide (CO), nitrogen oxides (NOx) and particulate matter (PM) emissions. Transient testing showed that the Shell LOW NOX Fuel lowers NOx, HC and PM emissions with no statistically significant change in CO emissions for both cold-starts and hot-starts when compared to diesel certification test fuel.

The influence of fuel density on exhaust emissions from diesel engines has been investigated in a number of studies and these have generally concluded that particulate emissions rise with increasing density This paper reviews recent work in this area, including the European Programme on Emissions, Fuels and Engine Technologies (EPEFE) and reports on a complementary study conducted by CONCAWE, in cooperation with AVL List GmbH The project was carried out with a passenger car equipped with an advanced technology high speed direct injection turbocharged / intercooled diesel engine fitted with a complex engine management system which was referenced to a specific fuel density This production model featured electronic diesel control, closed loop exhaust gas recirculation and an exhaust oxidation catalyst Tests were carried out with two EPEFE fuels which excluded the influence of key fuel properties other than density (828 8 and 855 1 kg/m3) Engine operation was adjusted for changes in fuel density by resetting the electronic programmable, read-only memory to obtain the same energy output from the two test fuels In chassis dynamometer tests over the ECE15 + EUDC test cycle the major impact of fuel density on particulate emissions for advanced engine technology/engine management systems was established A large proportion of the density effect on particulate and NOx emissions was due to physical interaction between fuel density and the electronic engine management system Limited bench engine testing of the basic engine showed that nearly complete compensation of the density effect on smoke (particulate) emissions could be achieved when no advanced technology was applied

Methane emissions from lean-burn natural gas engines can be relatively high. As natural gas fueled vehicles become more prevalent, future regulations may restrict these emissions. Preliminary reports indicated that conventional, precious metal oxidation catalysts rapidly deactivate (in less than 50 hours) in lean-burn natural gas engine exhaust. This investigation is directed at quantifying this catalyst deactivation and understanding its cause. The results may also be relevant to oxidation of lean-burn propane and gasoline engine exhaust. A platinum/palladium on alumina catalyst and a palladium on alumina catalyst were aged in the exhaust of a lean-burn natural gas engine (Cummins B5.9G). The engine was fueled with compressed natural gas. Catalyst aging was accomplished through a series of steady state cycles and heavy-duty transient tests (CFR 40 Part 86 Subpart N) lasting 10 hours. Hydrocarbons in the exhaust were speciated by gas chromatography.