Intake Valve Lift Research Articles

Effect of intake valve lift and binary alcohol (bioethanol+isobutanol) addition on energy, exergy, sustainability, greenhouse gas impact and cost analysis in a hydrogen/diesel dual fuel engines

Greenhouse gas emissions are a significant problem contributing to global warming and climate change and it is essential to increase the use of renewable and biomass-derived fuels in internal combustion engines to reduce greenhouse gas formation. Alcohol fuels and hydrogen have become prominent in recent years due to less harmful emission levels as a result of combustion. While there are very few studies in the literature on ternary mixture + hydrogen in terms of energy and exergy, there is a gap on the effect of the valve lift amount. The aim of this study is to investigate the effects of binary alcohol addition and variable intake valve lift (IVL) in hydrogen-diesel dual fuel mode on energy, exergy, sustainability, and greenhouse gas emissions. The experiments are conducted at variable torque conditions, involving three different IVL values (4, 4.46, and 4.9 mm) and four different fuel combinations (diesel, diesel + H2, diesel + binary alcohol, and diesel + binary alcohol + H2). The binary alcohol addition consists of 10% bioethanol and 10% isobutanol volumetrically, while in the dual-fuel mode, hydrogen is injected into the cylinder at a constant flow rate. When the results are examined, the highest energy and exergy values are obtained with the IVL-Diesel + H2 operation, providing on average 11% and 8% higher exergy efficiency compared to IVL 4-Diesel and IVL 4.46-Diesel studies, respectively. Additionally, the exergy destruction in the IVL-Diesel + H2 study shows an average decrease of 16% and 12%, respectively, compared to the IVL 4-Diesel and IVL 4.46-Diesel studies. Additionally, significant reductions in emissions are achieved. In the IVL 4.9-EB20+H2 study, HC, CO, and CO2 emissions decrease by 28%, 40%, and 28%, respectively, compared to the IVL 4.0 study. When examining the GHG emission impact, it is analysed that operating a single-cylinder engine with EB20+H2 fuels under 4.9 mm IVL conditions emits, on average, 36% and 32% less GHG impact over a one-year period compared to IVL 4-Diesel and IVL 4.46-Diesel studies, respectively.

Study on the effects of intake valve timing and lift on the combustion and emission performance of ethanol, N-butanol, and gasoline engine under stoichiometric combustion and lean burn conditions

To achieve carbon neutrality goals, renewable alcohols and new technologies are receiving increased attention. Variable valve technology can effectively improve engine efficiency. However, there is limited research on valve strategies suitable for alcohol. To further promote the efficient and clean application of alcohol, this article studies the effects of intake valve timing and lift on performance of ethanol, n-butanol, and gasoline engines under stoichiometric combustion and lean burn. It is found that the combustion process of ethanol and n-butanol is prolonged by advancing intake valve timing, while gasoline is the opposite. Meanwhile, the improvement of equivalent brake-specific fuel consumption (ESFC) is the most significant when fueled with gasoline, improving by 6.9 %. The improvement of BSNOx is the highest when fueled with ethanol, improving by 42.07 %. Adjusting intake valve lift has a weaker impact on economy than valve timing. However, when adjusting the combination of throttle, valve lift and timing, the ESFC of ethanol, n-butanol, and gasoline can be reduced by 6.79 %, 4.35 %, and 10.98 %. Furthermore, combining valve timing and lean burn can further improve economy and emissions. The ESFC of ethanol, n-butanol, and gasoline can be decreased by 12.73 %, 6.87 %, and 11.96 %, while BSNOx decrease by 93.69 %, 74.86 % and 61.65 %.

Cyclic Analysis of In-Cylinder Vortex Interactions Based on Data-Driven Detection and Characterization Framework

Abstract The complex vortex flow interactions are critical to affect the fuel–air mixing and combustion stability in direct-injection engine. However, due to the strong cyclic variations inside engine, the multiscale swirl flow characteristics with cyclic details are difficult to be sufficiently revealed. Therefore, a vortex detection and characterization framework, including physical and data-driven methods, is implemented to elucidate the cyclic vortex interaction process. In this study, a high-speed time-resolved particle image velocimetry is applied to record the spatiotemporal flow behavior under three different swirl ratio conditions. First, the presence of vortex motion is detected at each crank angle for each engine cycle. Results show that the vortex interaction processes under different swirl ratio conditions exhibit distinctive characteristics. The presence of multiple vortices and their interactions are found to trigger dramatic changes and variations in swirl flow behavior. Then, the individual-cycle analysis of the vortex interaction effects on flow characteristics is conducted. The vortex characteristics including vortex location, strength, and size are examined with cyclic detail using data-driven unsupervised clustering. Results indicate that the vortex merging is the main source inducing the vortex characteristics variations. Furthermore, the occurrence and duration of the vortex merging process are found to be closely related to the intake swirl ratio and valve lift profile. Increased swirl ratio and valve lift cause vortex to merge earlier and reduce the merging duration. This finding provides a potential idea to alleviate the cyclic variation issue by controlling the vortex merging process.

Investigation of the effects of hydrogen energy ratio and valve lift amount on performance and emissions in a hydrogen-diesel dual-fuel compression ignition engine

The inadequacy of internal combustion engines using diesel fuel to meet emission standards has made it necessary to make radical innovations in these engines. With the use of hydrogen-diesel dual fuel mode, it is possible to increase the performance of these engines and reduce their emissions. However, there are many obstacles to the use of dual fuels. The most important of these obstacles is the decrease in the volumetric efficiency with the increase of the hydrogen energy ratio. To solve this problem, more air must be taken into the cylinder at the suction stroke. In this study, the effects of hydrogen energy ratio and intake valve lift amount on performance and emissions in hydrogen-diesel dual fuel mode were experimentally investigated. Experiments; constant speed (1850 rpm), different load (3, 4.5, 6, 7.5, 9 Nm), different hydrogen energy ratios (7, 9, 11, 13, 15) and made in different intake valve lift (4.0, 4.46, 4.9 mm) amounts. Compared to pure diesel and standard valve lift at 9 Nm load, 40% reduction in soot emissions and 33% reduction in CO emissions was determined when the hydrogen energy ratio was adjusted to 7% and the valve lift amount was increased by 10%.

Intake Valve Profile Optimization for a Piston-Type Expander Based on Load

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.

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

In order to cope with the increasingly severe energy and environmental problems, the development of new technologies and alternative fuels have gradually become a hot spot. The effects of different valve lift adjustment strategies on engine performance under stoichiometric combustion and lean burn were studied when fueled with methanol/gasoline blending. The results showed that when fueled with M100, M50 and M0 under stoichiometric combustion, compared with the original throttle condition, reducing valve lift resulted in a longer combustion process. Economy performance and BSNOx, BSCO emissions all can be improved in varying degrees by adjusting intake or/and exhaust valve lifts, but BSHC emissions showed no obvious variations. The optimal valve strategy for economy performance was different for different fuel. Combined adjusting intake and exhaust valve lifts with fully opened throttle was suitable for M100, the strategy combined throttle with intake and exhaust valve lifts was optimal for M50 and M0. The ESFC was improved at most 5.6%, 4.7% and 6.8% when fueled with M100, M50 and M0 under the optimal strategy respectively. Regardless methanol additional rate, lean burn controlled by intake valve lift with fully opened throttle had more potential on improving engine economy performance. Blending methanol with gasoline could extend the lean burn limitation and further improve economy and emissions performance. The optimal ESFC improved by 1.7% and 2.4% more than that of original throttle engine when fueled with M0 and M100 respectively, and the lean burn limitation was expanded from 1.3 to at least 1.45.

Low-speed performance compensation of a turbocharged natural gas engine by intake strategy optimization

Power output at the low engine speed is limited for natural gas engines, even though the turbocharging technology is used. In this paper, the intake system of a turbocharged spark-ignition natural gas engine with 4 valves (2 intake valves and 2 exhaust valves) was optimized by considering the intake strategy effects on the engine torque output and fuel economy improvement. Firstly, a 1D numerical model with hierarchical 1D/3D approach based on GT-SUITE was developed and validated against the experimental data of engine torque and fuel consumption rate. This approach combined detailed analysis of in-cylinder flow, charge movement and combustion. Secondly, different intake strategies were designed and their effects on the intake mass flow rate and in-cylinder mass during the intake process, the swirl flow, tumble ratio and the turbulent kinetic energy during the compression process, the flame propagation and temperature distribution evolution after the spark ignition, and the pressure and heat release rate were numerically investigated. The results showed that compared with the original intake strategy, the asynchronized intake strategy (the intake valves close earlier and the intake valve lifts are reduced, while two intake valves have different intake strategy) reduces the backflow in the end of intake stroke, improves the in-cylinder swirl flow, increases the maximum heat release rate and shortens the combustion duration, and it is believed to be the optimized intake strategy. Finally, different cam profiles corresponding to the numerically designed intake strategies were applied to the bench test engine and the dyno experiments showed that the optimized intake strategy improves the torque and reduces the brake specific fuel consumption by 41.42% and 8.1% respectively at a low engine speed of 1200 rpm.

A Hybrid Approach Using Design of Experiment and Artificial Neural Network in a Camless Heavy-Duty Engine

Abstract Increasingly stricter emission regulations and fleet CO2 targets drive the engine development toward clean combustion and high efficiency. To achieve this goal, planning and conducting experiments in a time- and cost-effective way play a vital role in finding the optimal combinations of all selectable parameters. This study investigated the effects of five engine parameters on two engine-out responses in a camless variable valve actuation (VVA) heavy-duty engine. Five engine parameters were intake valve lift (IVL), inlet valve closing (IVC), injection pressure, start of injection (SOI), and exhaust gas recirculation (EGR). Initially, a design of experiment (DoE) model was generated to predict both engine-out responses: brake-specific fuel consumption (BSFC) and BSNOx emissions. Due to a poor fit of the BSFC regression model from DoE analysis, an artificial neural network (ANN) model was developed to predict BSFC instead. A d-optimal design with five engine parameters at five levels was used to design the experiment. Extra test points together with d-optimal design points were utilized to train the ANN model. The well-trained ANN model for BSFC and DoE model for BSNOx were combined with a genetic algorithm (GA) to generate the Pareto-optimal front. The results proved the concept of using a hybrid statistical approach (DoE + ANN) with GA as an effective tool to generate a range of compromise design solutions. By extracting designs along the Pareto-optimal front, the impact of engine parameters on the system can be explained.

Effects of swirl enhancement on in-cylinder flow and mixture characteristics in a high-compression-ratio, spray-guided, gasoline direct injection engine

In this study, the flow enhancement effects of applying a swirl control valve were investigated with particle image velocimetry and simulation using CONVERGE v2.4 program in a high compression ratio, spray-guided, gasoline direct injection engine. This was followed by analysis of varying the spray structure and the mixture preparation process for different swirl control valve angles. The flow intensity was strengthened in the order of swirl control valve angle 45°, 30°, and 0°, and spark plug gap velocities near TDC were increased 1.89, 4.40, and 6.69 m/s in that order. However, the effect was not significant when it was increased to more than 45°. Also, the swirl-dominant flow and the tumble-dominant flow were differentiated based on the relationship between maximum swirl and tumble ratios. In the swirl dominant flow (swirl control valve angle of 0°), more retarded injection timing produced mixture formation in the order of homogenous to mal-distributed to stratified, whereas in the tumble dominant flow (swirl control valve angle of 45°), the order was homogenous to stratified to mal-distributed. It was determined by characteristic period to which the injection timing belonged, and the characteristic period was defined based on the relationship between the intake valve lift and the piston velocity.

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

<div class="section abstract"><div class="htmlview paragraph">Diesel engine is vital in the industry for its characteristics of low fuel consumption, high-torque, reliability, and durability. Existing diesel engine technology has reached the upper limit. It is difficult to break through the fuel consumption and emission of diesel engines. VVA (Variable Valve Actuation) is a new technology in the field of the diesel engines. In this paper, GT-Suite and ANN (artificial neural network) model are established based on engine experimental data and DoE simulation results. By inputting Intake Valve Opening crake angle (IVO), Intake Valve Angle Multiplier (IVAM) and Exhaust Valve Angle Multiplier (EVAM) into the ANN Model, and by using SA (simulated annealing algorithm), the optimized results of intake and exhaust valve lift under the target conditions are obtained. According to the optimized results, the fuel consumption of BSFC (brake specific fuel consumption) can be saved by 3.9%, 0.9%, and 7.3% at three different target working conditions, respectively (1000r/min with 50% load, 2000 r/min with 35% load, and 3000r/min with 20% load. Under the three conditions, the intake valve lifts are 1.10, 0.96, 1.10 times as the original respectively and the exhaust valve lifts are 0.98,0.94 and 1.10 times respectively. In addition, by adding the secondary opening strategy of the exhaust valve lift, internal exhaust gas recycling (IEGR) can be achieved. The exhaust gas temperature increased by 9.55% (66.64K) under low-speed working condition, and fuel consumption increased slightly by 6.15%, which is also important for exhaust thermal management and external emission control in the cold start phase of diesel engines. By changing the intake and exhaust valve control, there are obvious differences in the optimal valve lift under different working conditions. Therefore, the application of the VVA system in the diesel engine is of great significance.</div></div>

Thermodynamic analysis of improving fuel consumption of natural gas engine by combining Miller cycle with high geometric compression ratio

The goal of this work is to solve the problem of low thermal efficiency of stoichiometric natural gas engines by combining the Miller cycle with a high geometric compression ratio (GCR). A one-dimensional thermodynamic model of a stoichiometric natural gas engine with turbocharger is established, and its effectiveness is verified by experimental data. On this basis, the influence of the high GCR combined with the Miller cycle achieved by early intake valve closing (EIVC) or late intake valve closing (LIVC) on the fuel consumption is studied in detail. The results show that the reasonable matching of the GCR and intake valve lift profile is beneficial to improve fuel consumption. The upper limit of fuel consumption improvement is determined by the performance of the turbocharger. The EIVC50 + GCR14 and LIVC75 + GCR13.5 solutions can not only ensure that the load and knock level are consistent with the baseline engine (IVC558 + GCR11.5), but also obtain the optimal fuel economy. Thermodynamic analysis further reveals the fuel-saving mechanism. The fuel consumption can be improved by 4.1%, mainly thanks to a good balance between theoretical efficiency and combustion loss. In addition, the reduction in gas exchange loss further improves fuel consumption. Unfortunately, the increase in heat transfer loss and friction loss limits the further improvement in fuel consumption.

Design and Dynamic Analysis of an Innovative Axial Shift Valvetrain System (ASVS) for Variable Stroke Engine

A variable valvetrain system is the key part of the variable stroke engine (VSE), which could achieve higher power performance and low-speed torque. An innovative axial shift valvetrain system (ASVS) was put forward to meet the air-charging requirements of a 2/4-stroke engine and complete a changeover within one working cycle. Two sets of intake and exhaust cam profiles for both intake and exhaust sides in the 2/4-stoke mode were designed for 2/4-stoke modes. Furthermore, a simulation model based on ADAMS was established to evaluate the dynamic valve motion and the contact force at different engine speeds. The dynamic simulation results show that the valve motion characteristics meet the challenges at the target engine speed of 3000 r/min. In two-stroke mode, the maximum intake valve lift could achieve 7.3 mm within 78°CaA, and the maximum exhaust valve lift could achieve 7.5 within 82°CaA on the exhaust side. In four-stroke mode, the maximum intake valve lift can achieve 8.8 mm within 140°CaA, and the maximum exhaust valve lift can achieve 8.4 mm within 140°CaA. The valve seating speeds are less than 0.3 m/s in both modes, and the fullness coefficients are more than 0.5 and 0.6 in the 2-stroke and 4-stroke mode, respectively. At the engine speed of 3000 r/min, the contact force on each component is acceptable, and the stress between cam and roller can meet the material requirement.

Flow Field Parametric Interpolation Using a Proper Orthogonal Decomposition: Application to the Variable Valve Timing Effect on a Tumble In-cylinder Miller Engine Mean Flow

The current article presents a method to reconstruct the mean velocity field of a cyclic flow for an input parameter value that has not been measured, allowing for the number of tests to be reduced. It is applied to the tumble flow of a gasoline engine following a Miller cycle. New engines often include variable valve timing (VVT) systems to maximize the efficiency of such over-expanded cycles for different operating points. The reconstruction was thus carried out using different offset values of the intake valve lift timing. Experimental data were collected from a transparent engine in an early intake valve closing (EIVC) configuration using particle image velocimetry (PIV). The mean velocity field reconstruction was based on the interpolation of the proper orthogonal decomposition (POD) coefficients. The accuracy of the method was evaluated at different points by comparing the interpolated and the measured flow fields. The accuracy was estimated by calculating the error in the rotation rate of the tumble and the position of its center of rotation. The new mean velocity field set allowed for the position of the tumble’s center of rotation to be closely tracked according to the input parameter and a rotation rate map to be made. Some results on Miller’s cycle could thus be found and the data generated could guide future developments.

Effects of Intake Valve Lift Form Modulation on Exhaust Temperature and Fuel Economy of a Low-loaded Automotive Diesel Engine

Exhaust after-treatment (EAT) systems on automotive vehicles cannot perform effectively at low loads due to low exhaust temperatures (Texhaust < 250oC). Con-ventional late intake valve closure (LIVC) technique - a proven method to im-prove diesel exhaust temperatures - generally requires the modulation of the whole valve lift profile. However, an alternative method - boot-shaped LIVC - only needs partial lift form modulation and can rise exhaust temperatures signif-icantly. Therefore, this study attempts to demonstrate that boot-shaped LIVC can be an alternative solution to improve exhaust temperatures above 250oC at low-loaded operations of automotive vehicles.A 1-D engine simulation program is used to model the diesel engine system operating at 1200 RPM engine speed and at 2.5 bar brake mean effective pres-sure (BMEP) engine load. Boot-shaped LIVC is achieved via keeping the valve lift constant (at 4.0 mm) for a while during closure and then closing it at different closure angles. The method results in up to 55oC exhaust temperature rise through reduced in-cylinder airflow and thus, is adequate to keep EAT system above 250oC at low loads. The longer the boot is kept during closure, the lower the air-to-fuel ratio is reduced and the higher the exhaust temperature flows at turbine exit. Similar to conventional LIVC, boot-shaped LIVC improves fuel con-sumption as pumping losses are decreased in the system. Despite aforementioned improvements, EAT warm-up is affected negatively due to the significant drop-off on exhaust mass flow rates. The need to modify only some parts of the lift profile is a technical advantage and can reduce production costs.

Controls and Hardware Development of Multi-Level Miller Cycle Dynamic Skip Fire (mDSF) Technology

<div class="section abstract"><div class="htmlview paragraph">mDSF is a novel cylinder deactivation technology developed at Tula Technology, which combines the torque control of Dynamic Skip Fire (DSF) with Miller cycle engines to optimize fuel efficiency at minimal cost. mDSF employs a valvetrain with variable valve lift plus deactivation and novel control algorithms founded on Tula’s proven DSF technology. This allows cylinders to dynamically alternate among 3 potential states designated as: High Fire, Low Fire, and Skip (deactivation). The Low Fire state is achieved through an aggressive Miller cycle with Early Intake Valve Closing (EIVC). The three operating states in mDSF can be used to simultaneously optimize engine efficiency and driveline vibrations. Acceleration performance is retained using the all-cylinder, High Fire mode. mDSF can be implemented cost-effectively using an asymmetric intake valve lift strategy, with one high-flow power charging port and one high-efficiency Miller port.</div><div class="htmlview paragraph">Prototype mDSF cylinder heads were based on the EA888 Gen 3B engine by retrofitting the valvetrain with asymmetric intake cams, deactivatable roller finger followers and two oil control valves per cylinder. Event-based engine controls were developed to enable for each cylinder dynamic selection of the three mDSF operating modes: High Fire, Low Fire and Skip. Appropriate air estimation, fuel control and ignition control techniques were employed to ensure acceptable torque delivery and tailpipe emissions.</div><div class="htmlview paragraph">Engine dynamometer tests showed a 23% reduction in engine fuel consumption at 1500 rpm, 2 bar NMEP. Maximum torque and power from the baseline production engine up to 5000 rpm were also achieved. mDSF vehicle tests on the WLTC demonstrated a 6% reduction in CO<sub>2</sub> from Miller 2-step. Euro 6d compliant emissions were also reported. Further improvements in fuel economy, drivability and NVH may be possible by leveraging mixed firing densities more extensively.</div></div>

Analysis of intake swirl in a compression ignition engine at different intake valve lifts

In the present work, analysis of intake swirl is carried out on a single cylinder, direct injection diesel engine to determine the effect of swirl ratio on engine performance. A two dimensional CAD model was built to predict the pressure, temperature and velocity variation of air entering the cylinder during the suction and compression strokes of a cycle and the swirl ratio was calculated. Later, a three-dimensional model of the cylinder and a valve was made to carry out simulations at different valve lifts to identify and obtain the optimized swirl. Here, the maximum swirl ratio was obtained at 1 mm of valve lift whereas minimum at 6 mm of valve lift. The simulated results are validated with experimental data and good agreement was found between them. In addition to this, guide vanes were introduced in the intake manifold increasing the overall swirl ratio and hence leading to better engine performance.

Numerical Study of Intake Flow Optimization using Genetic Algorithm and Artificial Neural Networks

An easy way to comply with the conference paper formatting requirements is to use this document as a template and simply type your text into it. The increase in the performance of internal combustion engines for diesel engines has driven to follow alternative ways in order to improve the flow characteristics. This paper presents the computational fluid dynamics (CFD) modeling to study the effect of intake flow condition on the swirl ratio and volumetirc efficiency of a direct injection (DI) diesel engine. A single cylinder direct injection diesel engine with two directed intake ports whose outlet is tangential to the wall of the cylinder has been considered. The numerical results from this geometry are validated with the experimental results and published in the literature. In order to enhance the swirl ratio, intake flow in different components are adjusted instead of modifying the intake manifold shape and profile. The experiments are designed by full factorial approach for 3 variables (three components of intake velocity) to study the turbulent flows in a computational way and accomplished using OpenFOAM software. The induced swirl and tumble at the end of compression stroke are also computed and visualized. Numerous computations have been performed in this work during maximum intake valve lift and closed exhaust valve positions. To estimate the reliable data for predicted results, machine learning techniques such as artificial neural network is employed. Information is gathered for different combinations of intake velocity on swirl ratio and volumetric efficiency. Genetic algorithm is applied to fund the fittest data-set for several generations thereby the best optimal flow components are determined. The results from design of experiments approach and neural network techniques are compared.

Effect of the Intake Valve Lift and Closing Angle on Part Load Efficiency of a Spark Ignition Engine

This study provides an experimental evaluation of the effectiveness of Miller cycles with various combinations of lift and intake valve closing angle for a passenger car engine with premixed combustion in naturally aspirated operation. A fully variable electro-hydraulic valve train provided different valve lift profiles. Six load points, from 1.5 up to 5 bar brake mean effective pressure at a constant engine speed of 2000 min−1, were tested with 6 different intake valve lift/intake valve closing angle combinations. The intake valve closing angle was always set before bottom dead center to achieve the desired load with unthrottled operations. Experimental comparison with throttled operation outlines an indicated efficiency increase of up to 10% using high intake lift with early valve closing angle. Furthermore, this analysis outlines the influences that early intake valve closing angle has on fuel energy disposition. Longer combustion duration occurs using early intake valve closing angle because of turbulence dissipation effects, leading to slight reductions in the heat-to-work efficiency. However, overall pressure and temperature levels decrease and consequently heat losses and losses due to incomplete combustion decrease as well. Overall, we found that combustion deterioration is compensated/mitigated by the reduction of the heat losses so that reductions of pumping losses using early intake valve closing can be fully exploited to increase the engine’s efficiency.

Engine Valvetrain Lift Prediction Using a Physic-based Model for The Electronic Control Unit Calibration

The electronic control has an increasingly important role in the evolution of the internal combustion engine (ICE) and the vehicle. Research in the automotive sector, in this historical period, is dictated by three main guidelines: reducing polluting emissions and fuel consumption while maintaining high performance. The Electronic Control Unit (ECU) has made it possible, complicating the engine both in terms of architecture and in terms of strategies, controlling, through simplified functions, physical phenomena in an ever more precise way. The ECU functions are experimentally calibrated, reducing the error between the quantity estimated by the function and the experimental quantity over the entire operating range of the engine, developing extensive experimental campaigns. The calibration process of the ECU functions is one of the longest and most expensive processes in the development of a new vehicle. Some lines of research have been explored to reduce the experimental tests to be carried out on the test bench. The use of neural networks (NN) has proven to be effective, leading to a reduction in experimental tests from 40 to 60%. Another methodology consists in the use of 1D/0D Thermo-fluid dynamic models of the ICE. These models are used as virtual test benches and through them it is possible to carry out the experimental campaigns necessary for the calibration of the control unit functions. At the real test bench, only the few experimental tests necessary for the validation of the model must be carried out. One of the simplifications that is usually made in the 1D/0D ICE models consists in assigning a single intake and exhaust valve lift, without taking into account the effect of the engine speed on the valve lift in early intake valve closure (EIVC) mode for engines equipped with VVA. This phenomenon has a not negligible effect on engine performance, especially at high engine speeds. In the case of engine models equipped with VVA, the valve lift cannot be imposed, since it is unique for each closing angle at each engine speed. Indeed, in order to assign the correct valve lift for a given engine speed and EIVC, numerous experimental tests should be carried out, making vain the beneficial effects of the method. In this work, the authors propose the use of a 0D/1D CFD model of the entire electro-hydraulic valvetrain VVA module, coupled with 1D lumped mass for reproducing the linear displacements of the intake valve, and for simulating the interactions between flow and mechanical systems of the solenoid hydro-mechanical valve. Thus, model simulations allow to predict the valve lift in all the necessary conditions in the experimental campaigns for the calibration of the control unit functions. Starting from geometric valvetrain data, the model has been validated with a parametric analysis of some variables on which there was greater uncertainty, by comparing the valve lift obtained by the model with the experimental ones in certain engine speeds. Subsequently, the authors have obtained the valve lifts in conditions not used for model validation, comparing them with their respective experimental lifts. The model has proven to be sensitive to the effect of the variation of the engine speed, reproducing the valve lift with a low error. In this way it is possible to reduce the experimental effort aimed to the calibration process considering that the virtual experimental campaign has proven to be reliable.

Thermal Damage of Intake Valves in ICE with Variable Timing

The article provides the study on causes of damage to ICE intake valves, in the course of which the intake valve heads have been overheated and deformed as a result of material creep. On the example of the failure detected in the analysed engine, it has been established that the traditionally known reasons such as the combustion process failure cannot cause the damage described. For the purpose of determining the real causes of damage to the intake valves the authors simulated the thermal state of the intake valve in the heatingcooling conditions with the impact of gas in the cylinder and the impact of air in the intake pipe as well as the contact heat exchange with the seat with regard to thermal conductivity along the stem. The calculations have shown that with the increase of rotation frequency the failure of the control system that causes the engine to run at high rotation frequencies with a small intake valve lift leads to the temperature increase higher than it is recommended for the materials used, which causes the described overheating. Based on the conducted research the authors have developed recommendations for improving the reliability of the intake valves performance in the ICEs with variable valve timing.