Performance Optimization Using ANN-SA Approach for VVA System in Diesel Engine

Effects of different valve lift adjustment strategies on stoichiometric combustion and lean burn of engine fueled with methanol/gasoline blending

<div class="section abstract"><div class="htmlview paragraph">Many efforts have been invested to improve the fuel efficiency of vehicles mainly for the local consumers. One of the main techniques to have better fuel efficiency is cylinder deactivation system. In this paper, the main research area is focus on the investigation of cylinder deactivation (CDA) technology on common engine part load conditions within common Malaysian driving condition. CDA mostly being applied on multi cylinders engines. It has the advantage in improving fuel consumption by reducing pumping losses at part load engine conditions. Here, the application of CDA on 1.6 liter four cylinders gasoline engine is studied. One-dimensional (1-D) engine modeling is performed to investigate the effect of intake and exhaust valve strategy on engine performance with CDA. The 1-D engine model is constructed starts from the air-box cleaner up to exhaust system according to the 1.6 liter actual engine geometries. The model is simulated at various engine speeds with full load condition. The simulated results show that the constructed model is well correlated to measured data. This correlated model is then used to investigate the effect of valves timing configurations on engine performance. The model is then used to determine the optimum intake and exhaust valve lift and timing for CDA application at part load conditions. Also, the effects on the in-cylinder combustion as well as pumping losses are presented. The study shows that the effects of valves strategies are very significant on the engine performance. Pumping losses is found to be reduced, thus improving fuel consumption and engine thermal efficiency.</div></div>

<div class="section abstract"><div class="htmlview paragraph">Combustion simulations and single cylinder engine tests show a clear potential when coupling the Variable Compression Ratio (VCR) engine with the Variable Valve Actuation (VVA) technologies.</div><div class="htmlview paragraph">Simulations demonstrate the thermodynamic benefit from increasing the geometric Compression Ratio (CR>18:1) in combination with VVA compared to VVT strategies, thanks to the use of Atkinson / Miller Cycles. 3D combustion simulations of high compression ratio combustion chamber geometries used with Early or Late Intake Valve Closing strategies have been carried out with IFP-C3D™. They show an indicated efficiency increase up to 12 or 13% between compression ratio 10:1 and 18-20:1 at low loads (BMEP < 8 bar).</div><div class="htmlview paragraph">Single cylinder engine tests have been performed with specific combustion chambers up to CR 23:1 and have confirmed the simulation results.</div><div class="htmlview paragraph">0D GT-POWER™ simulations have been correlated to the engine tests and used to extrapolate them to a 3 cylinders 1.1L TGDI VCR-VVA engine, for both EIVC and LIVC intake valve lift strategies.</div><div class="htmlview paragraph">Finally, simulations and tests show correlated thermodynamic benefits of the association of VCR and VVA, improving fuel consumption on driving cycles between 8 and 11% compared to a 10.5:1 fixed compression ratio engine equipped with 2 VVT. Combining the VCR and VVA optimizes each potential far more than when separated (alone). Furthermore, the fuel consumption benefit is robust through driving cycles and downsizing level. </div></div>

<div class="section abstract"><div class="htmlview paragraph">Natural gas high pressure direct injection (HPDI) engines represent a technology with the potential for lower engine-out emissions and reduced fuel costs over a diesel engine. This combustion process uses a direct injection of natural gas, into the combustion chamber of a high compression ratio engine, to maintain diesel engine performance. As natural gas will not auto-ignite at typical engine conditions, a small quantity of diesel pilot fuel is used to initiate the combustion event.</div><div class="htmlview paragraph">One potential technique to improve engine performance is the optimization of the intake and exhaust valve timings. To experimentally investigate these effects, tests were performed on a single cylinder engine based on Westport Innovation's 15L HD engine. The intake valve closing time was varied both before and after the standard closing (EIVC and LIVC). Early closing of the exhaust valve was also tested (EEVC). This work aimed to control in-cylinder residual content, equivalence ratio, and temperature to maximize performance and minimize emissions.</div><div class="htmlview paragraph">The results showed that, due to pressure pulsations in the intake manifold and valve flow restrictions, LIVC was marginally effective at reducing charge mass. EIVC provided a larger reduction in charge mass under equivalent conditions. At loads below 50%, up to a 70% reduction in CH<sub>4</sub> emissions is measured at fixed intake pressures. At high load (75%) a 19% reduction in NOx is measured due to reduced in-cylinder temperatures resulting from lower effective compression ratios. At 10% load, EEVC cams can simultaneously reduce NOx, CH<sub>4</sub> and CO along with generating higher exhaust temperatures.</div></div>

<div class="htmlview paragraph">The magnitudes and compositions of in-cylinder tumble ratio generated by each velocity components were computed at different intake valve lifts and distances along the direction of valve axis in this paper, based on the three-dimensional velocity data measured by hot-wire anemometry at intake valve periphery of typical SI engine intake ports (horizontal and sloping directed ports) in a steady flow rig. The effect of velocity profiles at above two intake ports exit on in-cylinder tumble generation was studied, and a microscopic analytical method of evaluating tumble-generating capability of intake ports was developed according to the velocity profiles at intake valve exit area.</div>

<div>The influence of the intake valve lift of two Miller cycles on the in-cylinder flow field inside a DISI engine is studied experimentally since changes of the engine flow field directly affect the turbulent mixing and the combustion process. For the analysis of the impact of the valve timing on the general flow field topology and on the large-scale flow structures, high-speed stereo-scopic particle-image velocimetry measurements are conducted in the tumble plane and the cross-tumble plane. The direct comparison to a standard Otto intake valve lift curve reveals evidently different impacts on the flow field for both Miller cam shafts. A Miller cycle that features late intake valve closing shows a flow field comparable to the standard Otto valve timing and a tumble vortex of strong intensity can be identified. Hence, turbulent mixing is as sufficient as for the standard Otto valve timing, although the Miller cycle intake valve timing leads to a pressure reduction of approximately 20%. In contrast, a Miller cycle with early intake valve closing and reduced valve lift leads to an alteration of the in-cylinder flow field. The kinetic energy inside the cylinder as well as the vorticity decay to almost zero towards the end of combustion. In conjunction with an early dissolving tumble vortex of low intensity, turbulent mixing becomes insufficient for clean, efficient combustion.</div>

<div class="htmlview paragraph">This paper deals with the design and manufacturing of a mechanical variable valve actuation system, developed as part of the MUR financed research project concerning the realization of a high performance motorcycle engine, through a partnership of Moto Morini S.P.A. (BO), Dell’Orto S.P.A. (MI), Istituto Motori - CNR (NA), and DIME - Università di Napoli Federico II.</div> <div class="htmlview paragraph">After a synthetic description of the main variable valve actuation methods currently employed (timing, duration and lift variation, cyclic cylinder deactivation), the paper presents the results of our mechanical variable valve actuation system, consisting of three main elements: cam, main rocker arm with fixed fulcrum and secondary rocker arm with mobile fulcrum. It enables valve lift variation through a simple translation of the intermediate element (system 1).</div> <div class="htmlview paragraph">The study has been conducted implementing a numerical procedure specifically designed to determine cam profile and the kinematic and dynamic characteristics of the whole system, starting from the following input data: rocker arm geometry, relative positions and inertial data of elements, spring stiffness and preloading, camshaft speed and valve lift law. The model has been validated against the conventional timing system using kinematic simulations.</div> <div class="htmlview paragraph">Results of the numerical procedure verify the validity of the variable valve actuation system, capable of a valve lift variation from 30% to 100% of the maximum lift, with a limited acceleration (lower than maximum values). Based on the numerical results, we are developing a new mechanical variable valve actuation system. The new system consists of the same three elements used previously, but they are connected in a different way (system 2). The newer system enables more general lift profile distributions with a similar geometric complexity.</div> <div class="htmlview paragraph">A maximum closing limited to 30% does not enable cyclic deactivation of some cylinders (strategy feasible on multicylinder engines) or exclusion of one or more valves (strategy feasible on multivalve engines).</div> <div class="htmlview paragraph">The activity was extended to research for a new solution (always a mechanical system), capable to allow inlet valves complete closing and timing and duration variation (system 3).</div> <div class="htmlview paragraph">This paper reports results reachable with the simplest system 1. This new system gives better perspectives of use for a new two-wheel vehicle engine.</div>

<div class="section abstract"><div class="htmlview paragraph">Gasoline engine downsizing has become a popular and effective approach to reduce CO<sub>2</sub> emissions from passenger cars. This is typically achieved in the form of a boosted direct injection gasoline engine, which are typically equipped with variable valve timing (VVT) devices on the intake and/or exhaust valves.</div><div class="htmlview paragraph">This paper describes the synergies between valve timings and boost based on experimental investigations in a single cylinder gasoline direct injection spark ignited (DISI) engine with variable cam phasing on both the intake and exhaust cams. Two cam profiles have been tested to realize Miller cycle and compared with the standard camshaft. One cam features a long opening duration and standard valve lift for Late Intake Valve Closing (LIVC) and the other cam has a short opening duration and low valve lift for Early Intake Valve Closing (EIVC). An external boost rig was used to provide adjustable pressurized air charge, allowing conditions of up to 4000rpm and 25.6 bar NIMEP to be studied.</div><div class="htmlview paragraph">Results have shown that the EIVC cam produced the best net Indicated Specific Fuel Consumption (ISFC) among the three cam profiles, with up to 11% improvement in net ISFC relative to the standard cam profile. The benefits of late split injections have also been studied to overcome the issue of low combustion speed when using low valve lift.</div></div>

<div class="htmlview paragraph">The present work concerns the study of the potentialities of high-boost small-displacement C.R. (Common Rail) diesel engines where the compressor and the expander are mechanically disengaged for the purpose of power cogeneration from the exhaust gas. This objective can be achieved by means of advanced concept electrical devices capable of delivering the energy produced by the expander either to the drivetrain transmission or to the even more power-demanding auxiliary equipment of both the engine and the vehicle.</div> <div class="htmlview paragraph">The performance of a small-displacement boosted diesel engine with a common-rail injection system has been predicted by means of a computational code obtained by integrating different in-house non-commercial codes that simulate the intake, combustion and exhaust processes.</div> <div class="htmlview paragraph">The model validation has been carried out by means of the experimental data obtained at Fiat Research Center on a commercial small-displacement C.R. turbocharged diesel engine. The data related to: in-cylinder pressure time-histories, injection-rate distributions, air- and fuel-flow rates, EGR (Exhaust Gas Recirculation) mass fraction, discharge flow coefficients of the intake and exhaust valves, intake- and exhaust-gas pressures as well as engine performance at different speeds and loads. The computational code requires the heat-release distribution and the heat-transfer coefficients as inputs for the simulation of the engine cycle. Therefore, a heat release analysis of the measured in-cylinder pressure was performed and the heat-transfer coefficients in the model were adjusted so that the computed in-cylinder pressure matched the measured one.</div> <div class="htmlview paragraph">After calibration, the model was applied to the analysis of the engine performance at <b>A/F</b><sup><span class="xref">1</span></sup> of approximately 19 for different boosting and exhaust pressures as well as for different engine speeds and loads. The compressor and the expander were taken as mechanically disengaged and the maximum boost pressure was chosen so as to comply with an in-cylinder pressure limit of ≈ 180 bar. The engine performance were characterized in terms of the following main parameters: engine torque, power and fuel consumption, expander power output and overall system efficiency. This latter was evaluated as the ratio between the available net power of the whole system, including the supercharger, and the energy supplied by the fuel. It was ascertained that an overall efficiency of the system higher than 45% can be achieved. Moreover, an insight was given into the CO2 and pollutant exhaust emissions.</div>

Intake valve parameters significantly affect the performance of the piston-type expander (PTE). To improve compressed energy utilization efficiency, intake valve parameters need to be regulated according to load. In this paper, an electro-pneumatic variable valve actuation (EPVVA) system was proposed for independent control distributing valve parameters. The trajectory planning for the intake valve was proposed to obtain good mechanical properties. Then, the intake valve duration angle was optimized, and the optimum intake valve lift curves were obtained at different rotational speeds. Results show that the energy efficiency decreased with the intake valve duration angle increasing. The output power ascended sharply with increasing intake valve duration angle, but the amplitude of power growth decreased. The output power had a maximum value at a specific intake valve duration angle. The gray relation analysis (GRA) method was applied to obtain the optimum intake duration angle based on output power and energy efficiency. Finally, the optimum intake valve trajectories were presented under different rotational speeds. Results are helpful for the future control of the piston-type expander.

<div class="htmlview paragraph">The paper presents an original review and extension of existing mathematical models for on-line residual gas fraction estimation. The resulting model has first of all been extended to take into account also the presence of externally recirculated exhaust gas (external EGR), and then critically analyzed to highlight the importance of a correct Intake Valve Opening and Exhaust Valve Closing effective position identification. As shown in the paper, such quantities may be evaluated by using experimental data, either acquired in the test-cell or on a valve flow bench.</div> <div class="htmlview paragraph">The main objective is to obtain a simple and reliable model (that could be run in real time within the engine control unit) also in presence of Variable Valve Timing (VVT, both on intake and exhaust valves) and external Exhaust Gas Recirculation (EGR) systems. In fact, the two main contributions to residual gas fraction (backflow of the burned gas during the valve overlap period, and amount of gas trapped within the cylinder) are strongly affected by intake and exhaust valves timing, and EGR flow should be taken into account in order to determine the total exhaust gas mass within the cylinder at IVC. Therefore, real time estimation of residual gas mass and composition is crucial for designing VVT and EGR management strategies that allow an optimal control of the combustion process.</div> <div class="htmlview paragraph">The new model has been applied to experimental data acquired on a 3.2 liter V6 GDI engine, equipped with intake and exhaust Variable Valve Timing systems. Tests were performed throughout the engine operating range for different combinations of intake and exhaust valve timings, while varying EGR flow. Model results are in good agreement with other measured quantities (such as Spark Advance angle and NO<sub>x</sub> emissions), and the proposed approach therefore represents a powerful tool for on-board optimal combustion control.</div>

Alternative fuel research has been gaining more attention by many engine researchers for the past few decades because of the tremendous increase in the demand for the fuel as well as the price of the fuel. Many alternative fuels have been synthesized for diesel engine from sources such as bio feed stocks, waste oils, waste tier scraps, and waste plastics. Most researchers have carried out their research on analyzing the performance, emission, and combustion characteristics of the engine fueled with different alternative fuels. Depending on the characteristics study for a particular alternative fuel, some alterations have been attempted in injection timing, injection pressure, compression ratio, and allowing exhaust gas recirculation (EGR). Moreover, those studies were carried out for only a few times of engine runs. Beyond this, very few researchers conducted experiments on engine parts durability while the engine is powered alternative fuels. This review mainly focuses on tribological study on different engine parts and metals contamination in lubricating crank case oil after the engine has been run for particular hours with alternative fuels. Most of the long durability tests concluded that viscosity of lubricating oil reduced as much earliest, there were increased metal particles in the lubricating oil, slight increased wear in crank case bearing, and increased accumulation of lacquer and carbon on piston compared to diesel operations. Unusual wear could be noticed in pistons, cylinder head, and intake and exhaust valves with alternative fuels. Also, it had induced more dry deposits on fuel injector tip, intake valves, and exhaust valves. In this review, no technical issues have been identified in engine operations, but duration of effective usage of lubricating oil has been reduced by 2/4th time, while reliability of engine parts has been reduced by 1/4th time.

Comparative study using RSM and ANN modelling for performance-emission prediction of CI engine fuelled with bio-diesohol blends: A fuzzy optimization approach

<div class="htmlview paragraph">Diesel engine fuel consumption is mainly a function of engine component design and power requirements. However, fuel consumption can also be affected by the environment in which the engine operates. This paper considers two controlling parameters of the engine's thermal environment, oil temperature and coolant temperature. The effects of oil and coolant temperatures on Brake Specific Fuel Consumption (BSFC) are established for a turbocharged diesel engine. Data are also presented for a direct injection, naturally aspirated diesel engine.</div> <div class="htmlview paragraph">A matrix of test conditions was run on a Cummins VT-903 diesel engine to evaluate the effects of oil and coolant temperatures on BSFC for several loads and speeds. Loads and speeds were selected based on where a typical semi-tractor engine would operate over the road on a hills and curves route. Oil temperature was monitored and controlled between the oil cooler and the engine. Coolant temperature was monitored and controlled at the engine outlet. The BSFC data were fit to a regression equation as a function of load, speed, oil temperature and coolant temperature for the matrix of test conditions. The test results showed that BSFC decreases as both oil and coolant temperatures increase. The results also indicate that BSFC was more sensitive to changes in oil temperature than to changes in coolant temperature over the range of the test data.</div>

<div class="htmlview paragraph">Variable Valve Timing (VVT) strategy on both intake and exhaust valves has a pivotal influence on the specific fuel consumptions and engine performance. In addition to this, fuel economy can also be enhanced by the application of Variable Compression Ratio (VCR) strategy.</div> <div class="htmlview paragraph">This paper presents three possible strategies to enhance fuel economy improvement:</div> <div class="htmlview paragraph"> <ul class="list disc"> <li class="list-item"><div class="htmlview paragraph">A possible VVT strategy Early Intake Valve Opening (EIVO) and Late Exhaust Valve Closure (LEVC) that alters the valve overlap to reduce fuel consumption</div> </li> <li class="list-item"><div class="htmlview paragraph">A two-position VCR system that improves fuel conversion factor to realize fuel economy</div> </li> <li class="list-item"><div class="htmlview paragraph">A strategy that combines above two technologies to produce a complementary effect on fuel economy</div> </li> </ul> </div> <div class="htmlview paragraph">All three strategies have been tested on a 1.8L DOHC four cylinder PFI engine. AVL BOOST a 1D engine gas exchange and cycle simulation code was used to model this engine to get fuel economy gains at part-load points. Therefore, the simulation provided essential information to understand engine thermodynamic process and VVT system development.</div>