Fuel Injection System Design, Analysis and Testing Using Bond Graph as an Efficient Modeling Tool

<div class="htmlview paragraph">One of the most vital factors in combustion control is Air-to-Fuel Ratio (AFR) control and estimation. Various parameters such as intake air mass flow rate, fuel injection quantity and (Exhaust Gas Recirculation) EGR flow rate are affecting the AFR magnitude. In this study a detailed mathematical, nonlinear and control oriented model of dynamic processes of turbocharged diesel engines is presented for the purpose of AFR control. It is an attempt to describe the two main subsystems of compression ignition engines called intake manifold and fuel injection systems.</div> <div class="htmlview paragraph">The intake model itself consists of compressor, intercooler, intake manifold, EGR circuit, valve section and cylinder subsystems. This model has been developed for study of the air intake system in a turbocharged diesel engine, using physical equations. Experimental data has also been used to adjust the model. The output variable of this submodel (air mass flow) is a significant parameter in calculations of engine power, emission and AFR control. Of the methods of assisted aspiration, the exhaust gas driven turbocharger is by far the most widely used. Varying the rate of gas flow through the turbine by means of Variable Geometry Turbine (VGT) is a method by which the exhaust gas flow through turbine can be limited at high engine speeds. Therefore, turbocompound in this model is considered to have VGT.</div> <div class="htmlview paragraph">Common Rail Injection (CRI) that is a fully flexible fuel injection system in which quantity, timing and pressure of injection are controllable (based on electronic control) separately is chosen in this study. Fuel injection system is comprised of solenoid, working chamber and needle subsystems. A one-dimensional, transient and compressible flow model of CRI, based on Kirchhoff's law, mass and momentum conservation equations and the equilibrium of forces is derived.</div> <div class="htmlview paragraph">AFR control of diesel engine is performed make use of fuzzy logic methodology. Fuzzy logic is a control structure which emulates the way humans arrive at decisions, given a certain set of circumstances. This method improves the control and simplifies the development process. The fuzzy logic controller achieves this by considerably reduced complexity and lack of tedious mathematical derivation associated with modern control theory methods.</div> <div class="htmlview paragraph">All above-mentioned models are programmed in Matlab/Simulink software environment. The simulation results are then compared with available data to check the accuracy of the model.</div>

<div class="section abstract"><div class="htmlview paragraph">Recently, diesel engine manufacturers have been improving the tolerance of fuel injection quantity and timing in response to the strengthening of emissions regulations and the introduction of various kinds of diesel fuels. This paper describes the Intelligent Accuracy Refinement Technology (i-ART) system, which has been developed as a way of achieving substantially improved tolerances.</div><div class="htmlview paragraph">The i-ART system consists of a fuel pressure sensor installed in the injectors. It calculates the injection quantity and timing at high speed using a dedicated microcomputer designed for pressure waveform analysis. As the injector can directly measure the fuel injection pressure waveform for each injection, it can compensate the injection quantity and timing tolerance at any time.</div><div class="htmlview paragraph">Toyota Motor Corporation has introduced this system in Brazilian market vehicles. In Brazil, the PROCONVE L6 emissions regulations will be introduced in 2012, and the market also uses various kinds of diesel fuels. The i-ART system enables diesel engines to satisfy these new regulations, and drastically improves fuel consumption by adopting a low compression ratio and 3-pilot injection control. A cetane number detection control has also been developed using the i-ART system characteristics. As a result, even if a vehicle is driven using low or high cetane number diesel fuel, the same level of combustion noise is achieved by adjusting the engine calibration based on the detected cetane number. Engines equipped with this system have successfully passed the new emissions regulations and are compatible with the various kinds of diesel fuels used in Brazil.</div></div>

<div class="section abstract"><div class="htmlview paragraph">Various sensors including throttle position sensors (TPS), manifold pressure sensors (MPS), crank angle sensors, engine temperature sensors, and oxygen sensors are mounted in electronically controlled fuel injection (FI) systems to accurately regulate the air-fuel ratio according to the operating state and operating environment. Among these vehicle-mounted sensors, TPS has functions for detecting a fully-closed throttle and estimating intake air volume by the amount of throttle opening. Currently, we have conducted a study on transferring TPS functions into the MPS (manifold pressure sensor) in order to eliminate the TPS. Here we report on detecting a fully-closed throttle for achieving fuel cut control (FCC) and idle speed control (ISC) in fuel injection systems.</div><div class="htmlview paragraph">We contrived a means for fully-closed throttle detection during ISC and controlling changes in the bypass opening during FCC in order to accurately judge each fully-closed throttle state via the manifold pressure. A factor in causing fluctuations in manifold pressure in a fully-closed throttle state are changes in the engine RPM (also referred to as engine speed) and changes in the degree of opening of the bypass (hereafter simply bypass opening). By keeping the bypass opening during FCC we limited the cause of fluctuations in manifold pressure to just the engine RPM; and by comparing the manifold pressure with an manifold pressure threshold equivalent to a fully-closed throttle detected at each engine RPM, we were able to accurately detect fully-closed throttle states. Another achievement was detecting a fully-closed throttle state during idling for performing ISC. This ISC adjusts the bypass opening in order to converge the engine RPM during idling to the target RPM. In other words, the manifold pressure during idling fluctuates due to two causes or namely the engine RPM and the bypass opening. So by comparing the manifold pressure with a manifold pressure threshold value equivalent to a fully-closed throttle state from the bypass opening and engine RPM we succeeded in contriving a method to detect a fully-closed throttle state with good accuracy. We found that this control technology accurately achieves fully-closed throttle detection by manifold pressure which is one of the TPS functions.</div></div>

<div class="htmlview paragraph">A diesel spray model has been developed and validated against experimental data obtained for different injection and surrounding gas conditions to allow investigation of the relative importance of the different physical processes occurring during the spray development. The model is based on the Eulerian-Lagrangian approximation and the Navier-Stokes equations, simulating the gas motion, are numerically solved on a collocated non-uniform curvilinear non-orthogonal grid, while the spray equation is solved numerically using a Lagrangian particle tracking method. The injection conditions are determined by another recently developed model calculating the flow in the fuel injection system, the sac volume and injection holes area which accounts for the details of the injection velocity, the fuel injection rate per injection hole and occurrence of hole cavitation. Thus, differences between the sprays from inclined multihole injectors can be simulated and analysed.</div> <div class="htmlview paragraph">Several spray sub-models have been implemented into the code, and their influence on the predicted droplet characteristics was evaluated. These models account for liquid core atomization, droplet secondary breakup, droplet collisions, droplet impingement, droplet turbulent dispersion and droplet evaporation. Aerodynamic-induced atomization, jet turbulence-induced atomization and cavitation-induced atomization introduced by a new sub-model are the three mechanisms considered to be responsible for the liquid core primary break-up; the vibrational, bag, chaotic, stripping and catastrophic break-up regimes are taken into account using different droplet secondary break-up models reported in the literature. A new sub-model based on the maximum entropy formalism is used for the calculation of the droplet size distribution. Coalescence, bouncing and separation are the mechanisms accounting for droplet-droplet interaction and a model assuming isotropic turbulence is used for the calculation of the gas turbulence effects on droplet diffusion. Evaporation has been considered assuming both uniform droplet temperature and its variation within the volume of the droplet. Effects attributed to droplet deformation, as calculated by the break-up model, frequently neglected in other existing spray models, are found to play an important role on the fuel evaporation rate; heat and mass transfer correlations for the flow around spheroids were used for these calculations. In the case of spray impingement on a wall, the rebounding, splashing and sticking regimes were considered, representing different physical assumptions adopted for the simulation of droplet-wall interactions; these models account for the effects of wall roughness, presence of wall film and wall temperature on the properties of the secondary droplets ejected from the wall.</div> <div class="htmlview paragraph">Experimental test cases used for model validation include free atmospheric sprays injected into quiescent or cross flowing air, impinging sprays and diesel sprays in engine cylinders. Extensive comparison between computational and experimental results has been performed for the temporal and spatial variation of the droplet size and droplet velocities, the spray tip penetration and the global spray structure. The results revealed that the dominant parameters influencing diesel spray development and its mixing with the surrounding air are hole cavitation, injection velocity and droplet deformation.</div>

<div class="section abstract"><div class="htmlview paragraph">The air pollution is increasing at an alarming rate now a day mainly due to emissions coming out of automotive vehicles. The exhaust emissions gases are hazardous to human health. The increased number of vehicles on road will make the scenario even worse. In order to control the pollution level, the regulatory bodies are now implementing stringent emission norms. In India, the regulatory authorities has framed the transition of BS IV to BS VI emission norms in 2020 by skipping the BS V emission norms which makes the automotive industries to work on more advanced fuel management technologies. It is more tedious to control the tail pipe emissions beyond BS IV emission norms with the conventional carburetor system since it is operating on open loop system. It is evident that in order to meet the stringent emission norms we need to have a closed loop system which controls the Air Fuel Ratio (AFR) close to stoichiometric to increase the conversion efficiency of the catalytic converter. The vehicle with fuel injection system can able to work on closed loop system, but the fuel injection system is not cost effective.</div><div class="htmlview paragraph">This paper illustrates the development of a cost effective smart engine management system for two wheeler application to meet the upcoming emission norms with some modification from the conventional carburetor system. Instead of controlling the fuel flow to keep the AFR close to the stoichiometric as in fuel injection system, the smart engine management system has a sophisticated air control mechanism to make the AFR close to stoichiometric. The carburetor was modified to incorporate an air control solenoid which is operated on the pulse width modulation to vary the air flow according to our requirement. The lambda sensor measures the AFR from the exhaust pipe and provides information to the ECU.</div><div class="htmlview paragraph">Based on the feedback from the lambda sensor, TPS, CPS, etc., the ECU maintains the AFR stoichiometric by controlling the flow through the air control solenoid with varying duty cycles. The vehicle performance test was carried out with vehicle having smart engine management system (Electronic carburetor) and also with fuel injection equipped vehicle on the chassis dynamometer. The test results show that the air fuel ratio of the electronic carburetor vehicle was maintained close to stoichiometric as in fuel injection vehicle which in turn reduce the emission to a considerable extent. Hence the smart engine management system caters a new way for an efficient low cost fuel management system.</div></div>

<div class="htmlview paragraph">The development of a bond graph model for a self-propelled irrigation system is presented. The bond graph integrates the mechanical, electrical and hydraulic subsystems of linear moving and center pivot irrigation systems into a comprehensive simulation model. The model includes the effects of the engine used to drive the well pump and electric alternator. Simulations using ENPORT/PC are used to analyze mobile irrigation systems with variable water flow requirements. Scenarios that result in variable water flow requirements included end guns, cornering systems and the use of Global Positioning Systems (GPS) to spatially vary the amount of water applied. Under each scenario, extreme system pressure variations resulted from the variable water demand if the well pump was not properly matched to the application. In addition, systems using existing engines and pumps previously designed for high pressure applications were found to be the most susceptible to the high pressure fluctuations.</div> <div class="htmlview paragraph">To address the pressure fluctuation problems associated with variable water demand, the bond graph model was used to evaluate the potential of a control system to maintain constant system pressure as water flow requirements varied from an irrigation system. Results indicated that small changes in engine speed as flow requirements changed could prevent the large pressure variations.</div> <div class="htmlview paragraph">Using the simulation results, a prototype engine speed control system was developed and field tested over the summer of 1995. The control system varied engine throttle position to maintain a given (input) system pressure as water demand varied. The throttle controller was installed on a Caterpillar 3208 naturally aspirated engine driving a Gould ten stage deep well turbine pump originally installed for a high pressure, high flow application (a traveling gun irrigation system). The engine/pump combination was currently being used to supply a low pressure center pivot irrigation system with a high output end gun which was operated approximately 70% of the irrigation cycle. Prior to installing the engine controller, system pressure increased from 300 kPa to 1000 kPa when the 700 1/min end gun cycled off. With the engine controller, system pressure varied within the range of 300 to 360 kPa with the end gun both on and off. The field results also indicate that a savings of approximately 5% in fuel consumption was obtained with the engine control system.</div>

<div class="htmlview paragraph">Theoretical and experimental investigations were carried out for the purpose of predicting and measuring the performance which results from operation of compression ignition engines when anhydrous ammonia is used rather than diesel fuel. Predictions were that ammonia would give slightly increased output but that fuel consumption would also increase 2-1/2 fold.</div> <div class="htmlview paragraph">By equipping the engine with a spark ignition system, it was possible to operate successfully on ammonia at normal compression ratios and retain the same fuel injection system. Fuel injection and spark timing were found to be critical. Indicated power output was reduced by about 10%, which differed from prediction. The discrepancy was due to the poor combustion characteristics of ammonia. Predicted increases in fuel consumption were experienced. Because ammonia is not “smoke limited” as is diesel fuel, it was possible to increase the smoke free output from the engine by going to richer mixtures with ammonia.</div>

<div class="htmlview paragraph"> </div> <div class="htmlview paragraph"> </div> <div class="htmlview paragraph">Five systems, fuel injection, ignition modulation, intake port flow control, exhaust after-treatment, and electric propulsion systems, are discussed here in terms of engine design modifications and new systems retrofitted to the motorcycle to reduce the exhaust emission.</div> <div class="htmlview paragraph"> </div> <div class="htmlview paragraph">A fuel injection system has been implemented to a 125cc air-cool four-stroke engine, and the results show that the improvement on the fuel economy, reduction of emission on HC and CO, and the fuel economy are 20%, 68%, and 10% respectively. By implementing the electrical ignition system into the target engine, the fuel economy and emission have slightly improved. The application of the inlet air flow control to a target engine also obtains 75% on CO reduction. The effectiveness of the exhaust after-treatment on a 80cc 2-stroke engine has demonstrated that the emission can be reduced up to 75%. The last emission reduction development is the electric propulsion system development which provide a zero emission and better energy efficiency solutions for the future motorcycle usage in the urban areas.</div> <div class="htmlview paragraph"> </div> <div class="htmlview paragraph">The authors will overview the development methodologies of the mentioned systems and the effectiveness of emission and fuel economy improvement from these engineering efforts in this article.</div> <div class="htmlview paragraph"> </div>

<div class="htmlview paragraph">Hino Motors has developed the new K13C, a 12.9 liter six cylinder in-line, heavy duty diesel engine that provides superior fuel consumption, extra low noise and excellent driveability together with a lower exhaust emissions. The initial K13C engine, whose production began in 1986 and about 30,000 units have been produced, is recognized all over the world for its good reliability and fuel economy. The new K13C is using the basic design and manufacturing/assembly processes of the previous one but includes a common-rail type fuel injection system with enhanced electronic controls to meet future regulation and customer requirements. Major design changes consist of a new cylinder head, a new front gear train, a new air intake system, a new turbocharger, a new compression brake system and electronic control module.</div> <div class="htmlview paragraph">The optimization of the intake system includes a new intake port and an electronically controlled inertia charging system. The highly effective turbocharger in conjunction with the electronically controlled common-rail system leads to better fuel consumption and lower exhaust emissions.</div> <div class="htmlview paragraph">In order to reduce engine noise, the following measures were taken: reduction of the mechanical noise by a newly designed gear train, reduction of air-bone noise from the cylinder head cover and intake system by using isolating rubber, and the reduction of combustion noise especially at engine idle speed by means of pilot injection.</div> <div class="htmlview paragraph">For safer driving and better driveability on both expressways and normal roads, braking performance and starting ability have been improved. The braking performance has been increased by adopting a new compression brake system with an electronically controlled waste gate valve in addition to an existent exhaust brake. The starting ability at clutch engagement is also improved by the increased injection pressure obtained by the common-rail fuel system. Moreover, the new starting assist system was developed. The vehicle equipped with the new K13C has almost the same starting ability as a 20 liter naturally aspirated engine which is the most popular for dump trucks in Japan.</div>

<div class="htmlview paragraph">A finite difference scheme comprising of two step Lax-Wendroff and Leap-frog techniques used to solve the continuity and momentum equations for a fuel injection system, is described in this paper in addition to the method of characteristics. Newton-Raphson method and Becchi's techniques have been tried to solve the boundary condition equations. A limited comparison with the well known Runge-Kutta scheme showed that the Newton-Raphson method is much simpler to apply and needs lass computational time. The validation of the above model has been carried out by comparing the predicted and experimental data of the fuel injection pressures and rates. This comparison showed that the present model could be utilized to predict the performance of the injection system with a reasonable degree of accuracy.</div>

<div class="htmlview paragraph">Experiments have been conducted in a firing single-cylinder spark-ignition engine employing a Ford Zetec cylinder head that has been modified to operate with either standard port-fuel-injection, air-forced port-fuel-injection or direct-injection. The engine utilizes a fused silica cylinder and therefore provides extensive optical access to the combustion chamber. Tests were conducted using a constant speed simulated cold start procedure, which is composed of an initial start-up transient and a quasi-steady-state idle period. In this procedure, the engine is briefly motored at 889 rpm and then combustion commences shortly after the start of fuel injection. Measurements which were performed include in-cylinder pressure as well as intake valve, exhaust valve, piston, cylinder, head, and intake air temperature throughout each cycle of the test period. The engine-out total hydrocarbon emissions were also measured. Engine start quality is quantified by the length of the initial start-up period and the stability of the quasi-steady-state idle. Based on these two parameters, the influence of three fuel injection systems, operating temperature, ignition timing, and injection timing on the engine performance during cold start are presented and discussed. In addition, the pre-combustion fuel distribution is measured using two-dimensional laser-induced fluorescence. The pre-combustion fuel distribution images of the three injection systems at different crank angles and times during the test are presented and discussed relative to engine performance.</div>

<div class="htmlview paragraph">More and more sophysticated electronic controls are going to be installed on cars, industrial vehicles and other means of transport, whose performances strictly depend on the accuracy and reliability of the sensors used to detect the operating conditions of the vehicle they shall manage.</div> <div class="htmlview paragraph">In particular as far as the pressure sensors concerns, the introduction of the monolithic devices (based either on silicon and on ceramic) has practically solved the problems of the pressure measurements at the intake manifold of the engine needed for the ignition and fuel injection systems. These pressures are usually ranging between 0 and 2 bar.</div> <div class="htmlview paragraph">However brakes and gear box electronic controls require sensors for much higher pressures (up to 50 bar for the gear box) and much more severe environmental conditions. Operating temperatures up to 130°, overpressures 5 times the nominal ones, high vibration levels, poisoning media faced to the membrane of the sensor are parameters which greatly affect the design of the device.</div> <div class="htmlview paragraph">Taking advantage of 5 years of experience with the sensors utilized for the Digiplex ignition and IAW fuel injection systems, and of the outstanding features of the thick films and alumina, on which they are based, our Company has carried out a work to develop a high pressure device able to meet the tightest specifications still maintaining a reasonable cost.</div>

<div class="htmlview paragraph">In the diesel field, innovative technology development has been desired for fuel injection system from the points of severe emission reduction to meet increasingly stringent emission regulation year by year respecting environmental protection and product improvement for various customer requirements including fuel consumption improvement.</div> <div class="htmlview paragraph">We have been pursuing the ideal fuel injection system which is called “ECD-U2” to meet above expectations.</div> <div class="htmlview paragraph">“ECD-U2” is the injection system of highly pressurized fuel with optimum injection timing by using of the injector controlled by high speed response magnetic valve. This system also has the fuel injection pattern controllability in one injection ( injection rate ) as one of the greatest asset.</div> <div class="htmlview paragraph">This report focuses on the new injector structure development to achieve desirable injection rate shaping for diesel engine combustion.</div>

<div class="htmlview paragraph">Year 2000 emission norms for Indian passenger cars, which have been notified requires major changes in the existing technologies being used in the passenger car vehicles on roads. Electronic fuel injection systems and catalytic converters are being used extensively abroad to meet stringent emission regulations. Even in India, major joint ventures in passenger car segment have introduced vehicles with single-point / multi-point fuel injection systems. It has become difficult to meet the mandated emission regulations with the conventional mechanical carburetted vehicles.</div> <div class="htmlview paragraph">Automotive Research Association of India alongwith M/s UCAL Fuel Systems has developed an electronic feedback carburettor system to use alongwith catalytic converter for a passenger car to meet the year 2000 emission norms. A closed loop system has been designed and developed which takes the input from a λ-sensor output and controls the additional air added in the intake manifold of the engine through a stepper motor. The carburettor has been tuned to the richer side initially to allow the air to be added so as to maintain the air-fuel ratio near stoichiometry throughout the driving cycle to get the maximum catalytic converter efficiency.</div> <div class="htmlview paragraph">The various advantages of this system include simple system configuration, minimum modifications of the existing carburetted engine and low cost.</div> <div class="htmlview paragraph">The present paper describes the design philosophy, the development of various systems, modifications carried out in the vehicle and testing of the vehicle for mass emissions results. The results indicate that the passenger car developed with the electronic carburettor could meet year 2000 emission norms with a margin of over 30%.</div>

<div class="htmlview paragraph">In a diesel engine, the combustion and emissions formation are governed by the spray formation and mixing processes. To meet the stringent emission legislations of the future, which will demand substantial reductions of NO<sub>X</sub> and particulate emissions from diesel engines, the spray and mixing processes play a major roll. Different fuel injection systems and injection strategies have been developed to achieve better performance and lower emissions from the diesel engine almost without investigating the influence of the injector nozzle orifices.</div> <div class="htmlview paragraph">A reduction in the nozzle orifice diameter is important for an increased mixing rate and formation of smaller droplets which is beneficial from emissions and fuel consumption point of view, as long as the local air-to-fuel ratio (AFR) is kept at a sufficiently lean level. A drawback with decreased orifice diameter is a shorter liquid fuel spray penetration length, which can lead to a worse air utilization and increased emissions, but this negative effect can be reduced by the use of a more compact piston bowl.</div> <div class="htmlview paragraph">In this study, the effects of reduced orifice diameters, arranged in both single and multi rows, were investigated using two different piston bowl designs at constant compression ratio. The injection rate was also varied by using two different injection pressures. The experiments were performed on a single cylinder, heavy duty, direct injection engine. The results show that a multirow nozzle with optimized umbrella angle and smaller piston bowl diameter can, at constant fuel consumption, obtain lower levels of NO<sub>X</sub> and soot than the reference engine configuration.</div>