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Technical Paper

A Turbo-Charged Four-Cylinder Engine Brand Sound Quality Development: A Wholistic Approach

2023-05-08
2023-01-1148
This paper introduces a wholistic approach for design and development of a turbo-charged four-cylinder engine system using the Quality Function Deployment (QFD) methodology for target setting. Additionally, an exhaustive comparison is conducted between the current product’s NVH performance and that of the target product to design the required countermeasures to reach the desired performance. The proposed process consists of subsequent phases; starting with the voice of customer collection and organizing customer clinic, definition of strategic target to reach, specifying the gap between the current product’s performance, and setting the desired target levels to design and develop the required enablers to close the gap. The final phase is the demonstration of the current product with emulated enablers to the stakeholders.
Journal Article

An Experimental Investigation of the Acoustic Performance of a High-Frequency Silencer for Turbocharger Compressors

2023-05-08
2023-01-1088
Conventional silencers have extensively been used to attenuate airborne pressure pulsations in the breathing system of internal combustion engines, typically at low frequencies as dictated by the crankshaft speed. With the introduction of turbocharger compressors, however, particularly those with the ported shroud recirculating casing treatment, high-frequency tones on the order of 10 kHz have become a significant contributor to noise in the induction system. The elevated frequencies promote multi-dimensional wave propagation, rendering traditional silencing design methods invalid, as well as the standard techniques to assess silencer performance. The present study features a novel high-frequency silencer designed to target blade-pass frequency (BPF) noise at the inlet of turbocharger compressors. The concept uses an acoustic straightener to promote planar wave propagation across arrays of quarter-wave resonators, achieving a broadband attenuation.
Technical Paper

Methodology for Controlling Rattle Noise in Vehicle Turbocharger Wastegate System

2023-04-11
2023-01-0409
When a turbocharger exhaust-driven turbine wheel spins fast enough to produce the desired level of boost, a wastegate is typically used to allow the excess exhaust pressure to divert around the turbine wheel. By opening the wastegate (typically boost-pressure referenced), exhaust pressure bypasses the turbo’s turbine wheel to prevent the turbo from reaching an unsafe speed. To actuate wastegate, different actuating mechanisms like pneumatic, vacuum or electric are available, which regulates poppet valve positions e.g. full close, open or partially open. In electronic wastegate valve, exhaust pressure pass through the bypass hole collides with the face of valve causing vibration. Such vibration is transmitted to the wastegate components causing rattle noise. It is challenging to design a wastegate mechanism which can sustain wastegate loads at high temperature and give quiet and robust performance within the full operating range of the engine.
Technical Paper

Thermomechanical Fatigue Crack Growth Simulation in a Turbo-Housing Model Using Nonlinear Fracture Mechanics

2023-04-11
2023-01-0596
Turbocharger housings in internal combustion engines are subjected to severe mechanical and thermal cyclic loads throughout their life-time or during engine testing. The combination of thermal transients and mechanical load cycling results in a complex evolution of damage, leading to thermo-mechanical fatigue (TMF) of the material. For the computational TMF life assessment of high temperature components, the DTMF model can provide reliable TMF life predictions. The model is based on a short fatigue crack growth law and uses local finite-element (FE) results to predict the number of cycles to failure for a technical crack. In engine applications, it is nowadays often acceptable to have short cracks as long as they do not propagate and cause loss of function of the component. Thus, it is necessary to predict not only potential crack locations and the corresponding number of cycles for a technical crack, but also to determine subsequent crack growth or even a possible crack arrest.
Technical Paper

Potential of a Hydrogen Fueled Opposed-Piston Four Stroke (OP4S) Engine

2023-04-11
2023-01-0408
The aim of this study is to develop a pathway towards Hydrogen combustoin on an opposed-piston four stroke engine (OP4S) by using 1D simulation code from Gamma Technologies. By its configuration, the OP4S engine has significant thermal efficiency benefits versus conventional ICE. The benefit of the OP4S is reduced heat losses due to elimination of the cylinder head, which increase the brake thermal efficiency. A hydrogen-fueled (H2) opposed-piston four stroke (OP4S) engine was modeled using GTPower to determine the potential on performance, thermal efficiency and emissions targets. The 1D model was first validated on E10 gasoline using experimental data and was used to explore changes to fuel type in NG and H2, fueling location (TPI and DI), fuel mixture strength (stoichiometric and lean), for an optimized plenum volume and turbocharger selection.
Technical Paper

A Modeling Tool for Particulate Emissions in GDI Engines with Emphasis on the Injector Zone

2023-04-11
2023-01-0182
Fuel film deposits on combustion chamber walls are understood to be the main source of particle emissions in GDI engines under homogenous charge operation. More precisely, the liquid film that remains on the injector tip after the end of injection is a fuel rich zone that undergoes pyrolysis reactions leading to the formation of poly-aromatic hydrocarbons (PAH) known to be the precursors of soot. The physical phenomena accompanying the fuel film deposit, evaporation, and the chemical reactions associated to the injector film are not yet fully understood and require high fidelity CFD simulations and controlled experimental campaigns in optically accessible engines. To this end, a simplified model based on physical principles is developed in this work, which couples an analytical model for liquid film formation and evaporation on the injector tip with a stochastic particle dynamics model for particle formation.
Technical Paper

Investigation of Compressor Deposit in Turbocharger for Gasoline Engines (Part 2: Practical Application to Turbocharger)

2023-04-11
2023-01-0412
Contribution to carbon neutrality is one of the most important challenges for the automotive industry. Though CO2 emission has been reduced through electrification, internal combustion engines equipped in vehicles such as Hybrid Electric Vehicle (HEV) and Plug-in Hybrid Electric Vehicle (PHEV) are still necessary for the foreseeable future, and continuous efforts to improve fuel economy are demanded. To improve powertrain thermal efficiency, direct-injection turbocharged gasoline engines have been widely utilized in recent years. Super lean-burn combustion engine has been being researched as the next generation of turbocharged gasoline engines. It is known that an increase of the boost pressure causes deposit formation, which decrease the turbocharger efficiency, in the turbocharger compressor housing. To avoid the efficiency loss due to deposit, air temperature at compressor outlet has to be limited low.
Technical Paper

Heat Transfer Correction Model for Turbocharger Compressor Performance Maps

2023-04-11
2023-01-0179
Turbochargers are still one of the most common solutions to improve internal combustion engines performance. The correct evaluation of turbochargers characteristic maps is one of the main issues to achieve a good matching with internal combustion engines. In a 1D procedure the accuracy of performance maps constitutes the basis of the turbocharger matching with the engine. The classical quasi-steady approach assumes that compressor and turbine characteristic maps are evaluated under the hypothesis of adiabatic turbocharger behavior. The aim of the paper is the investigation of the effect of heat transfer phenomena on the measured turbocharger maps. A model to correct compressor efficiency evaluated starting from measured data, thus removing the heat transfer effects, is proposed. The compressor steady flow behavior has been analyzed through specific tests performed at the test rig for components of propulsion systems of the University of Genoa, under various heat transfer conditions.
Technical Paper

Freevalve: Control and Optimization of Fully Variable Valvetrain-Enabled Combustion Strategies for Steady-State Part Load Performance and Transient Rise Times

2023-04-11
2023-01-0294
In passenger car development, extreme ICE downsizing trends have been observed over the past decade. While this comes with fuel economy benefits, they are often obtained at the expense of Brake Mean Effective Pressure (BMEP) rise time in transient engine response. Through advanced control strategies, the use of Fully Variable Valvetrain (FVVT) technologies has the potential to completely mitigate the associated drivability-penalizing constraints. Adopting a statistical approach, key part load performance engine parameters are analyzed. Design-of-Experiment data is generated using a validated GT-Power model for a Freevalve-converted turbocharged Ultraboost engine. Subsequently, MathWorks' Model Based Calibration (MBC) toolbox is utilized to interpret the data through model fitments using neural network models of optimized architectures.
Technical Paper

Hydrogen Hybrid ICE Powertrains with Ultra-Low NOx Emissions in Non-Road Mobile Machinery

2023-04-11
2023-01-0471
In this paper, we will show the potentials of reducing NOx emissions of an H2-ICE to an ultra-low level by hybridizing the H2-ICE in an NRMM powertrain. Real-world measurement data of NRMM together with a simulated hybrid powertrain and operating strategy form the input data for the H2-ICE on the test bench. We have modified a turbocharged four-cylinder in-line gasoline engine for use with directly injected hydrogen. Within several iteration loops, we obtained measurement data that shows that, depending on the operating strategy, ultra-low NOx emissions are reachable. The combination of hybridization, which implies the possibility of recuperation, and the CO2 emission-free H2-ICE leads to a highly efficient, robust, and economic drivetrain with the lowest emissions, perfectly suitable for Non-Road Machinery. Additionally, we will discuss the overall coupled measurement and simulation setup and the reachable NOx emission levels in our tested setup.
Technical Paper

Feature Extraction from a Crankshaft Instantaneous Speed Signal of an Automotive Power Unit using Cepstrum Analysis

2023-04-11
2023-01-0214
Internal combustion (IC) engines are the most common power unit technology found in road vehicles. The process of combustion within IC engines is linked to the output torque and overall powertrain performance. This work presents a method of analysing the parameters of cylinder pressure and crankshaft instantaneous speed signals obtained from a turbocharged, 4-stroke, 4-cylinder, 1.6 Litre, spark ignition, gasoline direct injection engine at various speed and load operating conditions. Whereas cepstrum analysis is used in the present work to extract critical features characterising the combustion process. Cepstrum analysis showed that the location of maximum heat release can be directly obtained from the quefrency of the instantaneous crank speed. This paper presents a systematic scheme for applying cepstrum for obtaining combustion features from the instantaneous crank speed signal.
Technical Paper

Combined Physical and ANN-Based Engine Model of a Turbo-Charged DI Gasoline Engine with Variable Valve Timing

2023-04-11
2023-01-0194
High-efficient simulations are mandatory to manage the ever-increasing complexity of automotive powertrain system and reduce development time and costs. Integrating AI methods into the development process provides an ideal solution thanks to massive increase in computational power. Based on an 1D physical engine model of a turbo-charged direct injection gasoline engine with variable valve timing (VVT), a high-performance hybrid simulation model has been developed for increasing computing performance. The newly developed model is made of a physics-based low-pressure part including intake and exhaust peripheries and a neural-network-based high-pressure part for combustion chamber calculations. For the training and validation of the combustion chamber neural networks, a data set with 10.5 million operating points was generated in a short time thanks to the parallelizable combustion chamber simulations in stand-alone mode.
Journal Article

Numerical Assessment and Performance Maps Generation of a Turbocharger Attempted to Be Matched with an Automotive Engine

2022-10-27
Abstract The present article aims to propose an efficient methodology to match aerodynamically a 1.5 L, three-cylinder downsized diesel engine with a suitable turbocharger (TC) to boost its performance based on a selection procedure and computational fluid dynamics (CFD) simulation. First, a radial turbine stage was sized and designed applying one-dimensional (1D) preliminary design in-house codes and then followed by a numerical simulation to investigate the flow fields and to predict its performance. Based on the simulation results, a global turbine performance map was generated. On the other hand, following a meticulous selection approach, a suitable TC compressor was chosen from a database. Therefore, performance maps of the designed turbine and the selected compressor were matched with the engine simulation model.
Technical Paper

Powertrain Optimization Strategy for Downsizing and NVH Refinement

2022-10-05
2022-28-0112
The prime target of IEA (international energy association) to reduce global average emission by 50% in 2030 has prompted focused R&D on automotive emission reduction as well as NEV (new energy vehicles). Of these strategies, engine downsizing constitutes the group of strategies employed to meet lower emission and fuel consumption targets in IC engines. Downsizing strategies have been proved successful in reducing emissions. There is widespread trend of downsizing existing engines with a goal to produce lower emissions along with equal or better performance. To achieve the stated goals downsized engines are usually charged or employ higher compression ratios. This raises NVH as well as structural issues that need further analysis. While the concept of downsizing has been studied in deep, its structural effects and NVH related issues are of concern. This paper throws light into different engine downsizing strategies and their effect on NVH.
Technical Paper

Realistic Steady State Performance of an Electric Turbo-Compound Engine for Hybrid Propulsion System

2022-09-16
2022-24-0015
The efficiency of Hybrid Electric Vehicles (HEVs) may be substantially increased if the unexpanded exhaust gas energy is efficiently recovered and employed for vehicle propulsion. This can be accomplished employing a properly designed exhaust gas turbine connected to a suitable generator whose output electric energy is stored in the vehicle storage system; a new hybrid propulsion system is hence delineated, where the power delivered by the main engine is combined to the power produced by the exhaust gas turbo-generator: previous studies, carried out under some simplifying assumptions, showed potential vehicle efficiency increments up to 15% with respect to a traditional turbocharged engine. Given the power target of the required exhaust gas turbo-generator, no commercial or reference product could be considered: on account of this, in the preliminary evaluations, the turbine efficiency was assumed constant.
Technical Paper

Supercharging with Turbo-Compounding - A Novel Strategy to Boost Single Cylinder Diesel Engines

2022-08-30
2022-01-1113
Mass-production single-cylinder engines are generally not turbocharged due to pulsated exhaust flow. Hence, about one-third of the fuel chemical energy is wasted in the engine exhaust. To extract the exhaust energy and boost the single-cylinder engines, a novel supercharging with a turbo-compounding strategy is proposed in the present work, wherein an impulse turbine extracts energy from the pulsated exhaust gas flow. Employing an impulse turbine for a vehicular application, especially on a single-cylinder engine, has never been commercially attempted. Hence, the design of the impulse turbine assumes higher importance. A nozzle, designed as a stator part of the impulse turbine and placed at the exhaust port to accelerate the flow velocity, was included as part of the layout in the present work. The layout was analyzed using the commercial software AVL BOOST. Different nozzle exit diameters were considered to analyze their effect on the exhaust back pressure and engine performance.
Technical Paper

Investigations on a Novel Supercharging and Impulse Turbo-Compounding of a Single Cylinder Diesel Engine

2022-08-30
2022-01-1111
Single-cylinder engines in mass production are generally not turbocharged due to the pulsated and intermittent exhaust gas flow into the turbocharger and the phase lag between the intake and exhaust stroke. The present work proposes a novel approach of decoupling the turbine and the compressor and coupling them separately to the engine to address these limitations. An impulse turbine is chosen for this application to extract energy during the pulsated exhaust flow. Commercially available AVL BOOST software was used to estimate the overall engine performance improvement of the proposed novel approach compared to the base naturally aspirated (NA) engine. Two different impulse turbine layouts were analyzed, one without an exhaust plenum and the second layout having an exhaust plenum before the power turbine. The merits and limitations of both layouts are compared in the present study.
Technical Paper

A Model-Based Investigation of Electrically Split Turbocharger Systems Capabilities to Overcome the Drawbacks of High-Boost Downsized Engines

2022-07-20
2022-01-5052
Engine downsizing is one the most common methods of coping with strict emission regulations. However, it must be coupled with complementary systems so that the engine performance would meet the standards. That is why new efficient solutions can pave the way toward this goal. The electric forced-induction system (EFIS) is the emerging replacement for conventional forced-induction systems (FIS), namely, turbochargers and superchargers. The reason behind this replacement is the drawbacks associated with FIS, among them are turbo lag and inefficiency in exhaust gas energy recycling. Electrically split turbocharger (EST) is a form of EFIS which offers a great potential for engine downsizing. In this paper, a new approach to EST utilization for lowering the fuel consumption (FC) without compromising performance has been introduced, through which the augmented degree of freedom enabled by an EST is used to optimize the air-charge boosting.
Journal Article

Effects of Boundary Layer and Local Volumetric Cells Refinements on Compressor Direct Noise Computation

2022-06-15
2022-01-0934
The use of turbochargers with downsized internal combustion engines improves road vehicles’ energy efficiency but introduces additional sound sources of strong acoustic annoyance on the turbocharger’s compressor side. In the present study, direct noise computations (DNC) are carried out on a passenger vehicle turbocharger compressor. The work focuses on assessing the influence of grid parameters on the acoustic predictions, to further advance the maturity of the acoustic modelling of such machines with complex three-dimensional features. The effect of the boundary layer mesh structure, and of the spatial resolution of the mesh, on the simulated acoustic signatures is investigated on detached eddy simulations (DES). Refinements in the core mesh are applied in areas of major acoustic production, to generate cells with sizes proportional to the local Taylor microscale values.
Technical Paper

Direct Water Injection Strategies for Performance Improvement of a Turbocharged Spark-Ignition Engine at High Load Operation

2022-06-14
2022-37-0007
Water injection (WI) could be a viable tool for the reduction of CO2 emissions of spark-ignition engines. At high loads, the performances of this kind of engines are constrained by knock phenomena, thermal limits of engine components and maximum tolerable in-cylinder pressure. Water injection, mainly due to its cooling effect, helps mitigating knock and reducing the exhaust gas temperature. Furthermore, it allows to obtain greater spark advances, better combustion phasing and leaner mixtures with a consequent improvement in terms of engine efficiency. In this work, the authors investigated the effects of a particular direct water injection (DWI) strategy on the performance of a turbocharged PFI spark-ignition engine at high load operation. The analysis has been carried out using a validated 1D model that reproduces the entire engine layout. A knock model allows to identify the knock-limited parameters in the various operating points analyzed.
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