Study of Automotive Diesel Injection-System Dynamics Under Control

<div class="htmlview paragraph">A two-dimensional finite element model of the head of a rhesus monkey was built to simulate the head acceleration experiments done by Gennarelli and his colleagues. The purposes of the study were to better understand the mechanisms of traumatic subdural hematoma and to estimate its threshold of occurrence.</div> <div class="htmlview paragraph">The brain was treated as an isotropic homogeneous elastic material with and without structural damping and the skull was treated as a rigid shell. To simulate Abel et al.'s (<span class="xref">1</span>) experiments, the head was subjected to an enforced forward rotation around the neck. The loading had an initial acceleration phase followed by deceleration. During both acceleration and deceleration phases, high shear stress (and thus strain) occurred at the vertex, where the parasagittal bridging veins are located. The deformation of the bridging vein depended on its orientation relative to the direction of impact. Bridging veins that drain forward into the superior sagittal sinus would be stretched during the acceleration phase and would be compressed during deceleration. Therefore, subdural hematoma may have occurred during the acceleration phase in the primate experiments, in contrast to Gennarelli and Thibault's (<span class="xref">2</span>) belief that this phase could be neglected in analyzing the subdural hematoma data.</div> <div class="htmlview paragraph">The head motion could be reduced to equivalent rotational and translational components at the head center of mass. With a brain Poisson's ratio of 0.475, both components contributed equally to bridging vein deformation. At a Poisson's ratio of 0.49, rotational acceleration was the dominant factor. Translational acceleration, although less important, did influence deformations and should not be neglected in analyzing the tolerance data of subdural hematoma.</div> <div class="htmlview paragraph">The primate subdural hematoma data were replotted in terms of peak angular vs. peak tangential accelerations. The combined effects of tangential and angular accelerations on bridging vein deformation, as determined at the lower levels of test severity from the finite element analysis, were used to estimate tolerance thresholds for subdural hematoma in the experiments.</div>

<div class="section abstract"><div class="htmlview paragraph">To explore the production and oxidation characteristics of soot in the flame of diesel jet under the condition equivalent to the direct injection diesel engine condition, the effect of three different important parameters (including injection pressure, injection duration, and oxygen concentration) are experimentally examined. For these purposes, a small CVCC (constant volume combustion chamber) with the volume of 60cc equivalent to the volume of combustion chamber of automotive diesel engine is used.</div><div class="htmlview paragraph">To obtain the experimental data of soot production and oxidation, in experiments, the ambient condition of temperature, pressure and oxygen concentration before injection timing are prepared by the combustion of lean hydrogen mixture (with help of 8 spark plugs) at a high temperature and pressure condition around 1000K and 4.5MPa. The common rail type injector with 8 injection holes for modern diesel engine is attached to this vessel. Injection pressures are set up at 80, 100, and 120 MPa. The effects of three important factors are analyzed including: (1) different injection pressures with constant injection mass; (2) different injection pressures with constant injection duration; (3) oxygen concentrations of 21% and 17% in volume. The optical window is attached on one side of this vessel and the full image of the spray flames can be visualized and recorded through this window by a high-speed color video camera. From the visualized color image of diesel flame, the flame temperature and the amount of soot inside the flame can be quantified by the two color method. This method is based on the theoretical principle that the light emission from the soot cloud is a thermal radiation of gray body which is a function of soot temperature and the KL factor, an index of the amount of soot.</div><div class="htmlview paragraph">The obtained results show that the injection duration and the injection rate are the dominant factors for heat release rate (HRR). On the contrary, within the experimental condition, the heat release rate is affected by both of the injection pressure and the oxygen concentration of ambient mainly at late combustion phase. The injection pressure and the injection duration give small effect on the level of flame temperature; however, the ambient oxygen concentration gives a large effect on the flame temperature.</div><div class="htmlview paragraph">Concerning the soot production and oxidation, all of the considered parameters have large effect. The interesting result is that the effect of injection pressure and ambient oxygen concentration on the maximum value of total KL factor is not so large. However, the soot production rate becomes lower as the decrease of injection pressure and as the decrease of ambient oxygen concentration, and results in the delayed arrival of the maximum total KL factor. Comparing with the HRR curve, it is revealed that the soot oxidation reaction is occurred under the very low HRR combustion in the case of low injection pressure and oxygen concentration condition.</div></div>

<div class="section abstract"><div class="htmlview paragraph">In the quest for reduced cost and shorter development times for fuel cell systems in industrial applications, two major issues arise. First, the electrochemical behavior of fuel cell systems is inherently difficult to predict. Second, testing fuel cell systems is resource intensive. These issues compound: Setting up an accurate model of a fuel cell system incurs long testing periods for model validation. Further, it does not guarantee acceptable results outside the tested range or for other membrane electrode assembly compositions.</div><div class="htmlview paragraph">To mitigate these two major issues an X in the Loop concept is proposed. Essentially, this is the direct integration of the test sample, here a single fuel cell, into the modelling environment of the whole system. In practice, two strategies with different levels of integration are defined.</div><div class="htmlview paragraph">The first strategy consists of initially deducing the operating parameters of the sample cell from the fuel cell system model. Then, setting them to the sample cell in the test bench. The response of the test sample is finally used to validate the designed system or update the parameters of the fuel cell model.</div><div class="htmlview paragraph">The second strategy is a step further towards the integration of the test sample into the model. Here, the core model of the fuel cell inside the fuel cell system model is completely replaced with the test sample, reducing the need for an accurate electrochemical model while improving the prediction of the behavior of the fuel cell system.</div><div class="htmlview paragraph">Compared to previously proposed testing concepts, here the balance of plants is directly integrated through a digital emulator, leading to a closer representation of the complete system. Furthermore, the test bench results are looped back to the model at run-time leading to a closer match between testing conditions and the real world as well a reduced impact of inaccuracies in the modelling of the fuel cell.</div><div class="htmlview paragraph">On the way to realizing this goal, an experimental test bench capable of showcasing working prototypes of the proposed operating strategies has been built.</div></div>

<div class="htmlview paragraph">The objective of the Project is to develop an optimized lead-acid battery solution for HEVs based on a novel, individual, spirally wound valve-regulated lead-acid 2V cell optimized for HEV use and low variability. This cell will be used as a building block for the development of a complete battery pack that is managed at the cell level. Following bench testing, this battery pack will be thoroughly evaluated by substituting it for the NiMH pack in a Honda Insight.</div> <div class="htmlview paragraph">The paper covers the first half of the 3-year project and will describe work carried out in the following areas:</div> <div class="htmlview paragraph"> <ul class="list disc"> <li class="list-item"><div class="htmlview paragraph">Development of cell and battery testing facilities and identification of mechanisms causing cell lifetime scatter.</div> </li> <li class="list-item"><div class="htmlview paragraph">The design and development of the prototype double-ended cell.</div> </li> <li class="list-item"><div class="htmlview paragraph">The development of the battery pack specification and pack design.</div> </li> <li class="list-item"><div class="htmlview paragraph">The development of the battery management system.</div> </li> </ul> </div> <div class="htmlview paragraph">The paper will also give details of the test results obtained on the demonstration vehicle with its original NiMH battery. Arising from these tests, there will be discussion of the merits of bench testing with a cycle derived from ‘real vehicle’ data as compared with the PNGV or Eucar power assist life cycle tests.</div>

<div class="section abstract"><div class="htmlview paragraph">Honda has developed the 2018 model CLARITY PLUG-IN HYBRID. Honda’s new plug-in hybrid is a midsize sedan and shares a body platform with the CLARITY FUEL CELL and the CLARITY ELECTRIC. The vehicle’s electric powertrain boosts driving performance as an electric vehicle (EV) over Honda’s previous plug-in hybrid.</div><div class="htmlview paragraph">The CLARITY PLUG-IN HYBRID’s electric powertrain consists of a traction motor and generator built into the transmission, a Power Control Unit (PCU) positioned above the transmission, an Intelligent Power Unit (IPU) fitted under the floor, and an onboard charger fitted below the rear trunk.</div><div class="htmlview paragraph">The PCU integrates an inverter that drives the traction motor, an inverter that drives the generator, and a DC-DC converter to boost battery voltage (referred to as a “Voltage Control Unit (VCU)” below). The VCU employs an interleaved circuit configuration and a coupled inductor and realizes approximately three times the rated continuous power and approximately three times the power density of a standard unit employed in a hybrid vehicle.</div><div class="htmlview paragraph">The IPU contains 17 kWh high-capacity battery modules and a 12 V DC-DC converter. A coolant-cooling method has been adopted to respond to the increased power of the battery, boosting cooling performance. The battery modules are positioned below the front and rear seats, and the high-voltage wiring is positioned between the modules, in the center of the vehicle. This layout has made it possible to fit the IPU below the floor of the vehicle, helping to enable the realization of a spacious and comfortable cabin seating five passengers, as well as a useful amount of trunk space.</div><div class="htmlview paragraph">The use of a high-power VCU and a high-capacity IPU has made it possible to realize EV operation in the high-speed range with no need to start the engine, giving the vehicle an adequate all-electric range (AER) for everyday use. During hybrid operation, increasing both the VCU power and the battery power helps ensure quietness while also allowing the engine to be downsized from 2.0 to 1.5 liters. The developed electric powertrain realizes a long AER of 47 miles and extremely quiet hybrid operation with a high level of fuel economy at 42 mpg.</div></div>

<div class="htmlview paragraph">The specific aim is to validate an engineering model for direct injection (DI) Diesel engine emissions. Characteristic times describing the controlling fluid mechanics and chemical kinetics will be employed in the model to correlate both NOx and particulate emissions. Because the model equations are algebraic, they are suitable for implementation in a phenomenological cycle simulation program, or as an emissions model option in a computational fluid dynamics code.</div> <div class="htmlview paragraph">An original premise was that earlier work on global NO chemistry based on pollutant emissions dominated by diffusion flame contributions had adequately elucidated the kinetic aspects of the model. It is shown here that this approach is not valid for modern engines. Rather, an improved two-zone flame model for NO formation/decomposition is required. Mellor et al. [<span class="xref">1</span>] propose such a model, but include only qualitative preliminary model validation. Here we further test the model using measurements from a high speed direct injection (HSDI) Diesel engine with a common rail fuel injection system. Exhaust gas recirculation variations from zero to maximum level possible are reported and correlated for parametric variations of engine speed, injection pressure, and load.</div> <div class="htmlview paragraph">The two-zone NOx HSDI Diesel characteristic time model (CTM) involves a skeletal mechanism consisting of seven elementary reactions [<span class="xref">1</span>]. A surrogate stoichiometric flame temperature around a spray plume at start of combustion conditions represents the environment for NO-forming eddies in the first zone. The second zone surrounds the stoichiometric region, and NO decomposition may occur depending on a surrogate flame temperature at the end of combustion computed from fuel/air dual (i.e., limited-pressure) cycle analysis. Both Zeldovich and nitrous oxide mechanisms are considered in each zone.</div> <div class="htmlview paragraph">Two objectives are accomplished in the present paper. First, in Mellor et al. [<span class="xref">1</span>] the N<sub>2</sub>O mechanism was postulated to be important to the NO formation kinetics under Diesel engine in-cylinder conditions. In addition, it was suggested that NO decomposition reactions may occur at high engine loads through the reverse N<sub>2</sub>O and Zeldovich mechanisms. These hypotheses are validated using the measured engine data. Second, we extend the previous work through preliminary development of the fluid mechanic aspects of the model. A characteristic mixing time that is a function of Reynolds number, Weber number, and engine geometry is developed. When used in combination with the kinetic time for NO formation as a Damköhler number, correlations of NOx emissions for the above parametric variations are obtained for conditions where NO decomposition does not occur.</div>

<div class="section abstract"><div class="htmlview paragraph">CO2 emission constraints taking effect from 2020 lead to further investigations of technologies to lower knock sensitivity of gasoline engines, main limiting factor to increase engine efficiency and thus reduce fuel consumption. Moreover the RDE cycle demands for higher power operation, where fuel enrichment is needed for component protection. To achieve high efficiency, the engine should be run at stoichiometric conditions in order to have better emission control and reduce fuel consumption. Among others, water injection is a promising technology to improve engine combustion efficiency, by mainly reducing knock sensitivity and to keep high conversion rates of the TWC over the whole engine map.</div><div class="htmlview paragraph">The comprehension of multiple thermodynamic effects of water injection through 3D-CFD simulations and their exploitation to enhance the engine combustion efficiency is the main purpose of the analysis. As basis for the research a single cylinder engine derived from a 1l turbocharged 3-cylinders engine is used to evaluate indirect and direct water injection. The entire engine flow field is reproduced and analyzed with 3D-CFD simulations and numerical models are employed to separate the influence of chemical and thermodynamic properties. Measurements are performed with different injectors for indirect/direct water injection in the single-cylinder engine in order to assess water break-up, wall wetting, spray interaction and penetration. Several injection strategies, such as varying start of injection, injection pressure, and water to fuel ratio, are tested at the single-cylinder engine test bench. Detailed gas phase chemistry is employed to link flame front speed with water concentration and knocking occurrence. These results are correlated with the 3D-CFD simulation of mixture formation, in-cylinder flow and water distribution for two different operating points (part load and maximum power) in order to study water behavior, with focus on the evaporation process, in-cylinder pressure and temperature profile, as well as the combustion development, during multiple engine cycles.</div></div>

<div class="section abstract"><div class="htmlview paragraph">In recent years the 2-wheelers engines companies have been focused on increasing the overall engine efficiency, that can be achieved amongst other by engine down-speeding, engine down-sizing and by reducing the frictions; however, to maintain or improve vehicle performance, it is necessary to provide a corresponding increase in specific power.</div><div class="htmlview paragraph">In accordance with these trends, the studied approaches and methodologies have been exploited, during the development of the new Piaggio small scooter engine.</div><div class="htmlview paragraph">In this work a multi-objective analysis has been applied to the valve train system design, in order to optimize the engine performance in terms of friction reduction, power curve and timing system response. Along with this optimization methodology, a robust design has been studied to make the peak cranking compression pressure insensitive to the engine starting device working. These calculation methodologies have been followed using commercial software as GT-SUITE® code and the modeFRONTIER® platform for the multi-objective optimization analysis.</div><div class="htmlview paragraph">The several configurations investigated have allowed to reach the desired trade-off between the appropriate and efficient valve train behavior and the engine performances.</div><div class="htmlview paragraph">The global engine friction reduction has been obtained thanks to low resisting cam torque profiles, a specific valve springs set and a new compression releaser device (during engine starting phase).</div><div class="htmlview paragraph">The results have been further validated by an experimental campaign carried out on the test bench for engine performance and on the specific cold test bench to evaluate friction losses.</div></div>

<div class="section abstract"><div class="htmlview paragraph">The main objective of this work is to describe the approach used and the results achieved on test bench, specifically for the piston design and development, which supports efficiency demonstration for a new class of internal combustion engine.</div><div class="htmlview paragraph">In this era of ICE revolution rather than evolution, although the piston function remains the same, the working boundary conditions are drastically changing, and the development time is often compressed in favor of a shorter time to market.</div><div class="htmlview paragraph">In this paper, piston requirements, functions, design and testing results from a development program on a Heavy Duty Recuperated Split Cycle Engine are reported. This includes the strategy for a fast and cost-efficient modification of the compression/expansion ratio, the technology and the materials used for reduction of heat losses, and a thermal expansion study, which supports material selection for the structure and the thermal barrier coating, to optimize piston function.</div><div class="htmlview paragraph">This work is based on available information, requirements, hypothesis & problem simplification, supported by virtual validation, FEM analysis, spreadsheet calculation, component specifications and performance leading to the final piston design.</div><div class="htmlview paragraph">This work includes the development done on suppliers’ side in order to fulfil the project requirements, the tradeoff between technology selection and the pressing need to respect an extremely short time frame for parts procurement.</div><div class="htmlview paragraph">This work is referring to a specific component, but the methodology described in this paper has been generally developed for the new class of ICE and can be successfully applied to other base engine components about the common key points (time to market, fuel efficiency, development costs).</div></div>

<div class="section abstract"><div class="htmlview paragraph">An experimental study on effects of high-pressure injections in conjunction with split fuel injections were conducted on an AVL single cylinder DI diesel engine. Various injection schemes were studied through the use of an electronically controlled, common rail injection system capable of injection pressures up to 200 MPa and a maximum of six injections per combustion event.</div><div class="htmlview paragraph">Up to 100 MPa of the fuel injection pressure, the higher injection pressures create faster combustion rates that result in the higher in-cylinder gas temperatures as compared to conventional low-pressure fuel injection systems. When applying high-pressure injections, particulate emission reductions of up to 50% were observed with no change in hydrocarbon emissions, reductions of CO emissions and only slightly higher NOx emissions.</div><div class="htmlview paragraph">Over 100 MPa, on the other hand, the higher injection pressures still reduced up to almost zero-level of particulate emission, at the same time that the NO emission is reduced greatly. Under these high-pressure injection conditions, strong correlations between soot and CO emissions were observed, which compete for the oxidizing OH species.</div><div class="htmlview paragraph">Multiple or split high-pressure injections also investigated as a means to decrease particulate emissions. As a result, a four-split injection strategy resulted in a 55% reduction in particulates and with little or no penalty on NOx emissions. The high pressure split injection strategy with EGR was more effective in reducing particulate and CO emissions simultaneously.</div></div>

<div class="section abstract"><div class="htmlview paragraph">The microcellular foam injection molding process for thermoplastic materials provides design flexibility and cost savings opportunities not found in conventional injection molding. This process allows for plastic part design with material wall thickness optimized for functionality.</div><div class="htmlview paragraph">The combination of density reduction and design for functionality can result in material and weight savings of up to 20%. With the correct equipment configuration, mold design, and processing conditions, these microcellular voids are uniform in size and distribution. The use of microcellular foam molding provides significant reductions in cycle time, material consumption, injection pressure, and clamp tonnage.</div><div class="htmlview paragraph">In this work, a physical foam molding process, MuCell, is applied to a polypropylene (PP) composite. The MuCell injection molding process involves the highly controlled use of gas in supercritical state, as the physical blowing agent, to create millions of micron-sized voids in thin wall molded parts (less than 3mm).</div><div class="htmlview paragraph">The results show that a weight reduction can be achieved without significant degradation in mechanical properties, such as stiffness and impact resistance. MuCell also contributes to faster cooling from the melt as well as the elimination of pack and hold phase, which both result in shorter injection molding cycle times and reduced warpage.</div><div class="htmlview paragraph">Once material tests have been completed, final part tests will also be performed, to validate established design specifications. These results presented here indicate that microcellular foam molding technology has good potential to be applied to interior parts of vehicles, contributing to weight reduction and productivity increase.</div></div>

<div class="section abstract"><div class="htmlview paragraph">A gasoline compression-ignition combustion system is being developed for full-time operation over the speed-load map. Low-temperature combustion was achieved using multiple late injection (MLI), intake boost, and moderate EGR for high efficiency, low NOx, and low particulate emissions. The relatively long ignition delay and high volatility of RON 91 pump gasoline combined with an advanced injection system and variable valve actuation provided controlled mixture stratification for low combustion noise.</div><div class="htmlview paragraph">Tests were conducted on a single-cylinder research engine. Design of Experiments and response surface models were used to evaluate injection strategies, injector designs, and various valve lift profiles across the speed-load operating range. At light loads, an exhaust rebreathing strategy was used to promote autoignition and maintain exhaust temperatures. At medium loads, a triple injection strategy produced the best results with high thermal efficiency. Detailed heat release analysis indicated that heat losses were significantly reduced. At higher loads, a late-intake-valve-closing strategy was used to reduce the effective compression ratio. For all tests, intake air temperature was 50 C.</div><div class="htmlview paragraph">3D CFD simulations of fuel injection, mixing, and combustion were important to understand the emissions formation processes. With multiple late injections and low-to-moderate fuel pressure, spray penetration was low, mixing was fast, and wall wetting could be avoided. Fuel sprays were characterized in a spray chamber. Injection rate was measured using a rate tube.</div><div class="htmlview paragraph">Results showed that ISFC was very low. Minimum ISFC of 181 g/kWh was measured at 2000 rpm-11 bar IMEP. For IMEP from 2 to 18 bar, engine-out NOx and PM emissions were below targets of 0.2 g/kWh and 0.1 FSN, respectively, indicating that aftertreatment for these species may be reduced or eliminated. It was found that combustion noise levels, characterized by several noise metrics, could be effectively controlled by the injection process. Measurements of exhaust particulate size distribution indicated very low particle count, especially for a preferred injector with low levels of in-cylinder swirl.</div><div class="htmlview paragraph">Collectively, these results demonstrate the potential feasibility of full-time GDCI using RON 91 gasoline at low-to-moderate injection pressures with high fuel efficiency. While more development work is needed, there is good potential for a practical GDCI powertrain system based on these concepts.</div></div>

<div class="htmlview paragraph">The investigation of pumping efficiencies of classic FIE lead to the development of an hydraulic unit injector (HUI). In the HUI the pump plunger is not directly driven by a camshaft but by a distributor-type fuel-injection pump (VE-pump) which simultaneously operates the control.</div> <div class="htmlview paragraph">The HUI was designed with a computer model. The differential piston increases the pressure by the multiplier 4. The VE-pump produces only 30 MPa for an injection pressure of 100 MPa. The high pressure chamber is filled through a small check valve.</div> <div class="htmlview paragraph">Cavitation in the pipe is eliminated by a specially designed delivery valve and a preloaded spring for the differential piston.</div> <div class="htmlview paragraph">A reduced needle shaft (3 mm diameter) leads to a very fast opening and closing of the nozzle, thus allowing to set the opening pressure to 40 MPa.</div> <div class="htmlview paragraph">The HUI's were driven on the pump test bench up to the engine speed of 5000 rpm and reached a peak injection pressure of 120 MPa. On the engine test bench a bmep of 0.8 MPa at a smoke number 4 was reached with a 1.7 l naturally-aspirated engine. The minimum specific fuel consumption was 225 g/kWh. The ignition delays are 2-4°CA shorter than usual due to the small 0.17 mm nozzle holes. This results in a considerably lower NO<sub>x</sub> concentration in the exhaust gas. On the other hand there is still a high smoke emission at part load which cannot be explained:Smoke number = 2 at bmep = 0.3 MPa and n = 3000 rpm.</div>

<div class="section abstract"><div class="htmlview paragraph">Cavitation plays a significant role in high pressure diesel injectors. However, cavitation is difficult to measure under realistic conditions. X-ray phase contrast imaging has been used in the past to study the internal geometry of fuel injectors and the structure of diesel sprays. In this paper we extend the technique to make in-situ measurements of cavitation inside unmodified diesel injectors at pressures of up to 1200 bar through the steel nozzle wall. A cerium contrast agent was added to a diesel surrogate, and the changes in x-ray intensity caused by changes in the fluid density due to cavitation were measured. Without the need to modify the injector for optical access, realistic injection and ambient pressures can be obtained and the effects of realistic nozzle geometries can be investigated. A range of single and multi-hole injectors were studied, both sharp-edged and hydro-ground. Cavitation was observed to increase with higher rail pressures. Comparative analysis of several injectors indicates that rounding the nozzle inlet delays the onset of cavitation due to reduced separation, but does not always suppress it. Tapering the nozzle hole is an effective means of suppressing cavitation. A single-hole injector mesh was designed based on x-ray imaging, and high resolution three dimensional large eddy simulations were performed using a homogeneous relaxation model. A two-phase submerged simulation was compared against a three-phase compressible solver modeling both non-condensible ambient gas and cavitation. Projections showed good agreement between the three-phase solution and x-ray experiments.</div></div>

<div class="htmlview paragraph">From september 1988 a fleet test started in Italy on urban buses equipped with a single ceramic monolith filter plus a by-pass and Diesel fuel burners for regeneration. The operation of the particulate trap, during the normal bus running in the city, has been assessed in three different ways:</div> <div class="htmlview paragraph"> <ol class="list nostyle"> <li class="list-item"><span class="li-label">1.</span> <div class="htmlview paragraph">Continuous control, by means of a data acquisition system purposely designed, of the main parameters affecting regeneration (i.e. time between consecutive regenerations, temperature in three selected zones in the filter during regeneration,filter loading);</div> </li> <li class="list-item"> <span class="li-label">2.</span> <div class="htmlview paragraph">Periodic control of smoke opacity of the bus measured, with and without the filter, under free acceleration and when bus is accelerating from 50 to 65 km/h on proving ground;</div> </li> <li class="list-item"> <span class="li-label">3.</span> <div class="htmlview paragraph">Particulate collection efficiency of the trap by using a dilution tunnel with the engine operated at the test bench.</div> </li> </ol> </div> <div class="htmlview paragraph">Information carried out from the fleet tests and additional information deriving from laboratory results were used for the system improvement.</div>