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Technical Paper

Dimethyl Ether (DME) - Assessment of Viscosity Using the New Volatile Fuel Viscometer (VFVM)

2001-05-07
2001-01-2013
This paper describes the development and test of a viscometer capable of handling dimethyl Ether (DME) and other volatile fuels. DME has excellent combustion characteristics in diesel engines but the injection equipment can break down prematurely due to extensive wear when handling this fuel. It was established, in earlier work, that the wear in the pumps is substantial even if the lubricity of DME is raised to a believed acceptable level using anti-wear additives. An influence of the viscosity on the wear in the pumps was suspected. The problem, up to now, was that the viscosity of DME has only been estimated or calculated but never actually measured. In the present work a volatile fuel viscometer (VFVM) was developed. It is of the capillary type and it was designed to handle DME, neat or additised. The kinematic and dynamic viscosities of pure DME were measured at 0.185 cSt and 0.122 cP at 25 °C respectively.
Technical Paper

Effect of Gas Density and Temperature on Air Entrainment in a Transient Diesel Spray

1996-02-01
960862
The air entrainment in a transient diesel spray was studied using laser Doppler anemometry to provide information on the effect of gas density and temperature. The spray was injected vertically into a confined quiescent atmosphere and the entrained mass flow rate was evaluated by measuring the air velocity component normal to a cylindrical geometric surface surrounding the spray, and extending to about 200 nozzle diameters (50 mm). The experimental results, relative to a density range from 0.84 to 7.02 kg/m3 and a temperature range from 293 to 473 K, indicate that the non dimensional entrainment rate, averaged in time over the main injection period, depends on the distance from the nozzle and both gas density and temperature. A first analysis, based on the available data, allowed to quantify the dependence and provided a correlation with such variables.
Technical Paper

Mutagenic Activity of the Soluble Organic Fraction of Exhaust Gas Particulate from a Direct Injection Diesel Engine

1996-10-01
961977
The main purpose of this study was to investigate the influence of diesel engine conditions on the mutagenic activity of the exhaust. Special emphasis was put on investigation of the influence of nitrogen oxides content. Experiments with a diesel engine have been carried out in the laboratory and the emissions of carbon monoxide (CO), carbon dioxide (CO2), nitrogen oxides (NOx) and particulate matter (PM) have been measured at different engine conditions. The particulate matter was extracted in order to obtain the soluble organic fraction (SOF), and this fraction was analyzed for mutagenic activity in the Salmonella/microsome assay (AMES test). It was found that the mutagenic activity evidently depended on the PAH content (PAH = Polycyclic Aromatic Hydrocarbons) of the exhaust gas rather than the NOx content. However, the percentage of the direct mutagenic activity of the total mutagenic activity increased as the NOx content in the exhaust gas increased.
Technical Paper

A 2-Dimensional Simulation Model for a Diesel Particulate Filter

1997-02-24
970471
The paper presents a 2-dimensional model for the calculation of the regeneration process in a wall flow diesel particulate filter. The model includes heat transfer by conduction and convection, a model for particle combustion based on diffusive burning of individual particles, and flow through the channels and across the filter walls. It was found that only the pressure drop across the walls need be considered for normal regeneration conditions. Comparisons between model predictions and experimental results for spatial dependent temperature time histories, and integrated degree of regeneration are used to validate the model. The validations were carried out for a series of severe regenerations, where there are large changes in flow and temperature throughout the process. Relative magnitudes of energy flows due to combustion, convection, and conduction are presented, as well as parametric studies of the effects of temperature, oxygen concentration and soot loading.
Technical Paper

Wideband SI Engine Lambda Control

1998-02-23
981065
Long term control of the AFR (Air/Fuel Ratio) of spark ignition engines is currently accomplished with a selvoscillating PI control loop. Because of the intake/exhaust time delay, the oscillation frequency and hence bandwidth of this loop is small. This paper describes a new approach to the design of this control loop using a novel observer system. In this way the bandwidth of this important loop is increased by a factor of 2 - 6 times, leading to more accurate overall AFR control. Moreover the observer approach is so robust and allows such feedback levels that it reduces significantly the accuracy required in the calibration of the base fuel control system with which it is be used. It can be used with either conventional- or advanced observer based- base fuel strategies.
Technical Paper

Performance and Emissions of a 0.273 Liter Direct Injection Diesel Engine Fuelled with Neat Dimethyl Ether

1995-02-01
950064
An experimental study is presented in which the use of neat dimethyl ether (DME) in a small non-turbo-charged diesel engine is demonstrated. It was found that with only minor fuel system modifications, DME gave very satisfactory combustion, performance and emissions. Engine operation with thermal efficiency equivalent to diesel fuel was achieved with much lower NOx emissions and with extremely low smoke and less engine noise. Additional NO, reductions were obtained by the use of EGR, without visible smoke and without deterioration in thermal efficiency, A limited durability study showed that the diesel fuel injection pump could operate on DME for more than 500 hours. A comparison of pure and technical grade DME was conducted.
Technical Paper

Modelling of the Intake Manifold Filling Dynamics

1996-02-01
960037
Mean Value Engine Models (MVEMs) are dynamic models which describe dynamic engine variable (or state) responses as mean rather than instantaneous values on time scales slightly longer than an engine event. Such engine variables are the independent variables in nonlinear differential (or state) equations which can be quite compact but nevertheless quite accurate. One of the most important of the differential equations for a spark ignition (SI) engine is the intake manifold filling (often manifold pressure) state equation. This equation is commonly used to estimate the air mass flow to an SI engine during fast throttle angle transients to insure proper engine fueling. The purpose of this paper is to derive a modified manifold pressure state equation which is simpler and more physical than those currently found in the literature. This new formulation makes it easier to calibrate a MVEM for different engines and provides new insights into dynamic SI engine operation.
Technical Paper

Mean Value Modelling of Turbocharged Spark Ignition Engines

1998-02-23
980784
An important paradigm for the modelling of naturally aspirated (NA) spark ignition (SI) engines for control purposes is the Mean Value Engine Model (MVEM). Such models have a time resolution which is just sufficient to capture the main details of the dynamic performance of NA SI engines but not the cycle-by-cycle behavior. In principle such models are also physically based, are very compact in a mathematical sense but nevertheless can have reasonable prediction accuracy. Presently no MVEMs have been constructed for intercooled turbocharged SI engines because their complexity confounds the simple physical understanding and description of such engines. This paper presents a newly constructed MVEM for a turbocharged SI engine which contains the details of the compressor and turbine characteristics in a compact way. The model has been tested against the responses of an experimental engine and has reasonable accuracy for realistic operating scenarios.
Technical Paper

Flow Characteristics of SiC Diesel Particulate Filter Materials

1994-03-01
940236
Recent studies have shown that SiC provides substantial advantages for use as the material for wall flow diesel particulate filters. In addition to very advantageous thermal properties, it has been shown that SiC based filter material has higher permeability than Cordierite. This paper presents a comparison of the basic flow characteristics of SiC based and Cordierite based wall flow filter material, expressed in terms of parameters which are basic materials properties that are independent of filter geometry. In addition, the flow characteristics of the particulate matter collected on the filter during engine operation are presented. The results show that the advantageous flow characteristics observed with the basic filter material are retained for loaded filters, up to very high loadings.
Technical Paper

Event Based Engine Control: Practical Problems and Solutions

1995-02-01
950008
In an earlier paper, some of the authors of this paper pointed out some of the difficulties involved in event based engine control. In particular it was shown that event based (or constant crank angle) sampling is very difficult to carry out without running into aliasing and sensor signal averaging problems. This leads to errors in reading the air mass flow related sensors and hence inaccurate air/fuel ratio control. The purpose of this paper is first to demonstrate that the conjectures about the operator input spectrum in a vehicle do actually obtain during vehicle operation in realistic road situations. A second purpose is to extend earlier modelling work and to present an approximate physical method of predicting the level of engine pumping fluctuations at any given operating point. The physical method given is based on a modification of the Mean Value Engine Model (MVEM) of a Spark Ignition (SI) engine presented previously.
Technical Paper

Thermal Loading in SiC Particle Filters

1995-02-01
950151
Silicon Carbide (SiC) has been shown to have a high melting/decomposition temperature, good mechanical strength, and high thermal conductivity, which make it well suited for use as a material for diesel particulate filters. The high thermal conductivity of the material tends to reduce the temperature gradients and maximum temperature which arise during regeneration. The purpose of this paper is to experimentally investigate the thermal loading which arise under regenerations of varying severity. An experimental study is presented, in which regenerations of varying severity are conducted for uncoated SiC and Cordierite filters. The severity is varied through changes in the particle loading on the filters and by changing the flow conditions during the regeneration process itself. Temperature distributions throughout the filters are measured during these regeneration.
Technical Paper

Advanced Nonlinear Engine Idle Speed Control Systems

1994-03-01
940974
One of the most important operating modes for SI engines is in the idle speed region. This is because SI engines spend a large part of their time operating in this mode. Moreover, a large measure of operator satisfaction is dependent on an engine operating smoothly and reliably in and around idle. In particular the operator expects that the idle speed will remain constant in spite of the engine loads due to power steering pumps and air conditioning compressors. In the idle speed region an SI engine is thought to be quite nonlinear because the engine loading can be quite significant, thus forcing the engine to be driven through a reasonably large portion of its lower operating range. Many of the earlier studies of idle speed control systems have dealt with linearized models which in principle have limited validity for the problem at hand. In order to improve this situation, it is necessary to deal with the more general nonlinear control problem.
Technical Paper

PAH-Transport in Diesel Engines

1997-10-01
972960
Engine experiments were carried out on a six cylinder DI-diesel engine using synthetic fuel and lubricant containing no PAH (Polycyclic Aromatic Hydrocarbons) [1]. By selectively doping the fuel and oil with pyrene, the effect of fuel and oil originating PAH on the exhaust emissions could be investigated. The experimental results are analyzed in a new way by suggesting a general transport model for PAH. By estimating as many transport quantities as possible it is attempted to gain knowledge about the most dominant mechanisms. The main finding is not surprisingly that for commercial fuels containing substantial concentrations of PAH, the by far major contributor to exhaust PAH is unburned fuel PAH. The concentration of PAH in the oil sump affects only weakly the PAH concentration in the exhaust for engines operating on commercial fuels. The PAH desorbing from the liner are getting burned efficiently, thereby being insignificant.
Technical Paper

Dynamic Tests of Racing Seats and Simulation with Vedyac Code

1998-11-16
983059
Dynamic tests have been performed on carbon fiber racing seats following the FIA regulations. The tests have shown, in rear impact tests, a relatively strong rebound leading to large forward bending of neck, and, in side impact tests, very large lateral displacement of the head, the latter protruding dangerously towards hard portions of the car structure. Stiffening the seat back by steel struts results in reducing strongly both the motion and the acceleration of the head. Simulations of the dynamics of the tests have been done with multi-body models, including the Hybrid III dummy and seat deflection, by means of the program VEDYAC. It has been found that computer simulation can predict very accurately the result of a test, provided the numerical models have been carefully calibrated to match the dummy tolerance bands. Once they have been calibrated and validated with a number of tests, the computer models can be very useful to extend the test results to different test conditions.
Technical Paper

Engine Operation on Dimethyl Ether in a Naturally Aspirated, Dl Diesel Engine

1997-05-01
971665
A naturally aspirated, direct injection diesel engine was modified in order to be run on dimethyl ether (DME), with a conventional pump-line-nozzle system. The effects of various modifications to engine timing and the injection system as well as EGR were experimentally determined. Compared to the original diesel engine, the NOx emissions were reduced by over 70% through the use of suitable timing, lowered injector opening pressure and EGR. Particulate emissions were very low, and represent over a 90% reduction as compared to the original diesel version. The original pump-line-nozzle injection system was found to be not well suited to DME operation, CO and HC emissions were substantially higher due to secondary injections, caused by high pressure oscillations and residual pressure with the DME.
Technical Paper

Fuel Additive Effects on Particulate Emissions from a Diesel Engine

1997-02-24
970181
Studies were performed with three commonly used additive metals, cerium copper, and iron, with a conventional and a low sulfur fuel in order to investigate fuel additive effects on engine particulate emissions before a particulate filter. Measurements were made on a 4 cylinder direct injection diesel engine and included total particulate mass, soluble organic fraction for both fuels, and polynuclear aromatic hydrocarbon emissions for the low sulfur fuel. The cerium based additive reduced the emissions with both fuels, with the largest effect being on the non-SOF fraction. With the other additives and the high sulfur fuel, non-SOF emissions were increased, increasing total particulate emissions. Copper was found to reduce the polynuclear aromatic hydrocarbons, and cerium was found to have the least effect. The use of an SiC wall flow filter reduced particulate and polynuclear aromatic emissions by over 90%.
Technical Paper

Toothed Couplings for Diesel Engines: An Example of Steel Substitution With Fiber Reinforced Plastics

1996-04-01
91A100
The replacement with plastic of an important component, formerly in steel, in the timing drive of a heavily duty diesel engine has been studied and realized. The substituted part is the toothed coupling connecting the injection pump to the timing drive. Torque that stresses the coupling has been measured with laboratory tests. The tooth stresses have been calculated with FEM analysis. Finally, fatigue tests have been carried out directly on the engine at different loadings. The test results are consistent with the predicted behavior of this component.
Technical Paper

Modelling of the Dynamic Processes in an Electronic Diesel Fuel Injection System

1992-02-01
920240
The new generation of electronic Diesel fuel injection systems with special solenoid valves presents a complicated mechanical/electrical system. It involves a combination of mechanical motion, hydraulic pressure wave propagation, and the transient magnetic and electrical processes which interact with other. In this paper, the coupled dynamic behavior of the new system is studied based on a research type electronic pump-pipe-injector system developed by authors. A general physical model is established, which includes other structure types such as the electronic unit injector and the electronic distributor pump system. Traditional mathematical models for conventional mechanical injection system or conventional solenoid valves, alone or simply connected, are not suitable for the new type of injection system. Therefore, a new comprehensive mathematical model is formulated.
Technical Paper

Nonlinear Transient Fuel Film Compensation (NTFC)

1993-03-01
930767
A very important component of an accurate steady state and transient air/fuel (A/F) ratio control strategy is the transient fuel compensation (TFC) substrategy. This is the part of an engine control algorithm which cancels the fuel film dynamics and makes it possible to place injected fuel into the intake manifold (or close to the intake ports or valves) of a spark ignition (SI) engine at the correct time and location. This paper presents the results of a very large series of experiments conducted with the same engine with either a throttle body (TBI) (or central fuel injection (CFI)) manifold or with a multi-point port injection (MPI) (or electronic fuel injection (EFI)) manifold. These experiments have shown that in some practical applications it may be necessary to model the intake manifold as a two time constant dynamic system rather than as a single differential equation system.
Technical Paper

Advanced Nonlinear Observer Control of SI Engines

1993-03-01
930768
In earlier work it has been shown that a nearly ideal solution to the problem of accurate estimation of the air mass flow to a central fuel injection (CFI) (or throttle body (TBI)) or EFI (or multi-point (MPI)) equipped engine is provided by using a closed loop nonlinear observer for the engine. With proper design this observer was shown to be both accurate and robust with respect to modelling end measurement errors. It is based on a Constant Gain Extended Kalman Filter (CGEKF). Since the publication of this work, another type of observer has emerged in the literature for which claims of great robustness have been made. This observer is based on new developments in the area of nonlinear control theory and is called a Sliding Mode Observer (SMO). In this paper these two types of observers are compared theoretically and experimentally on an engine mounted on a dynamometer. A very aggressive driving scenario is assumed for these tests.
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