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Viewing 1 to 30 of 473
2017-03-28
Technical Paper
2017-01-1057
Paul Zeng, Debabrata Paul, Vincent Solferino, Mark Stickler
1. Abstract Valvetrain ticking noise is one of the key failure modes in noise vibration harshness (NVH) evaluation at idle. It affects customer satisfaction inversely. In this paper, the root cause of the valvetrain ticking noise and key parameters that impact ticking noise will be presented. A physics based math model has been developed and integrated into a parameterized multi-body dynamic model. The analytical prediction has been correlated with testing data. Valvetrain ticking noise control is discussed.
2017-03-28
Technical Paper
2017-01-1070
Da Shao, Xu Sichuan, Aimin Du
Abstract The electromagnetic valve actuator (EMVA) is considered a technological solution for decoupling between crankshaft and camshaft to improve engine performance, emissions, and fuel efficiency. Conventional EMVA consists of two electromagnets, an armature, and two springs has been proved to have the drawbacks of fixed lift, impact noise, complex control method and large power consumption. This paper proposes a new type of EMVA that uses voice coil motor (VCM) as electromagnetic valve actuator. This new camless valvetrain (VEMA) is characterized by simple structure, flexible controllable and low actuating power. VCM provides an almost flat force versus stroke curve that is very useful for high precision trajectory control to achieve soft landing within simple control algorithm.
2017-03-28
Journal Article
2017-01-0635
Guy Babbitt, Jeff Rogers, Kristina Weyer, Drew Cohen, Stephen Charlton
Abstract This paper provides an overview of the analysis and design of the DigitalAir™ camless valve train including the architecture and design of the valve and head; the details of the electric valve actuator, and the flow characteristics of the valves and resulting charge motion in a motoring engine. This valve train is a completely new approach to fully variable valve actuation (FVVA), which allows almost unlimited continuously variable control of intake and exhaust valve timing and duration without the use of a camshaft. This valve train replaces conventional poppet valves with horizontally actuated valves located above the combustion deck. As the valves move, they open and close a number of slots connecting the cylinder with the intake and exhaust ports. The valve stroke necessary to provide the full flow area is approximately 25% of the stroke of the equivalent poppet valve, thus allowing direct electrical actuation with very low power consumption.
2017-03-28
Journal Article
2017-01-1073
Robert Huber, Jan Clauberg
Abstract The object of this study is a new chain tensioner with two labyrinth seals. For the simulation of chain tensioners within the framework of multi-body dynamics, a physically orientated model to describe the fluid dynamics of the labyrinth seals is derived. The easiest way to describe labyrinth seals is to use maps obtained from measurements. As this is very time-consuming, methods of 1D and 2D fluid-mechanics are used in this work to model the labyrinth seals. The seals are characterized by physically motivated parameters e.g. coefficients of resistance or friction. As these parameters can be derived from geometric data, a very good forecast feasibility without experimental investigations is provided. For high accuracy simulations model parameters can be refined by experimental data. As many and highly complex parameters have to be identified, this refinement is very time-consuming and requires lots of experiments.
2016-10-25
Technical Paper
2016-36-0213
Éderson Claudio Andreatta, Robson Pederiva
Abstract In design of valve train systems, it is useful to predict the dynamic behavior to calculate the loads, stresses and contact losses prevention. In this paper a kinematic model was developed over the cam discrete data, building a piecewise cam curve known as Spline, from the continuous curve is possible to predict the valve train kinematic characteristics, evaluating the values of displacement, velocity and acceleration of all valve train components. Based on the kinematic model results, the values of displacement imposed by the cam rotation are applied as input data to the dynamic model, that from a multiple mass system considering stiffness and damping of the components allows to know the valve train vibration behavior calculating the loads, stresses and losses of contact.
2016-10-17
Technical Paper
2016-01-2346
Wolfram Gottschalk, Rene Fink, Matthias Schultalbers
Abstract Advanced SI engines for passenger cars often use the cylinder deactivation technology for dethrottling and thus achieving a reduction of fuel consumption. The gas exchange valves of the deactivated cylinders are closed permanently by a zero lift of the cams. The solutions for cylinder deactivation can vary in the kind of gas composition included in the deactivated cylinders: charge air, exhaust gas or vacuum. All these strategies have in common the frequent loss of captured charge mass from cycle to cycle. Their two-stroke compression-expansion cycle additionally intensifies this phenomenon. Thus, a significant decrease of the minimum cylinder pressure can cause an undesired entry of lubricant into the combustion chamber. The idea was to ventilate the generally deactivated cylinders frequently to compensate the loss of captured cylinder charge mass. The task was to keep the minimum cylinder pressure above a certain limit to prevent the piston rings from a failure.
2016-09-27
Journal Article
2016-01-8063
David Ferreira, Thomas Howell, Peter Jo
Abstract Current heavy duty diesel valvetrains are not able to utilize hydraulic lash adjusters (HLA) in conjunction with an engine brake. During a braking event the engine brake introduces substantial lash into the vehicle valvetrain. The HLA reacts by pumping out to take up the lash encountered during braking, thereby preventing the valves from properly seating at the end of the cycle. Jacobs Vehicle Systems has developed a new mechanism to allow the inclusion of an engine brake into a valvetrain equipped with hydraulic lash adjusters. The fulcrum system maintains a load on the hydraulic lash adjuster during engine brake operation preventing the HLA from extending. HLA are appealing to engine manufacturers because they allow for simpler manufacturing, less maintenance, reduced NVH and valve motion enhancements. This paper describes the design, simulation and testing of the lashless valvetrain with engine brake including the next steps in the development of the valvetrain.
2016-09-27
Technical Paper
2016-01-8102
Rıfat Kohen Yanarocak, Yavuz Can Ozkaptan
Abstract The intake and exhaust valve spring of a 12.7L heavy duty diesel engine was instrumented with torque/shear rosette type strain gages to measure torsional stresses applied on the springs under different engine operating conditions. The engine was tested with no load, partial load and full load conditions and the effect of engine brake switch loading operation on the springs is investigated. Additional measurement of the valve lift motion and the peak fire pressure values from exactly the same cylinder were conducted to better understand the exact timing of the forces applied on the spring. This study gave an insight to the design engineer to determine the dynamic safety margin of the spring under permissible torsional stress values and optimize the material type of the spring accordingly. Another achievement is to measure any possible unpredictable torsional stress values occurred during engine operation when the engine brake is turned on/off and correlate the CAE model.
2016-04-05
Technical Paper
2016-01-0483
Honglu Wang, Bogdan Nitu, Jaspal Sandhu, Lurun Zhong, Bruce K. Geist, William F. Resh
Abstract Valvetrain dynamics modeling and engine combustion modeling are often carried out independently. As a result, the interaction between these two physical responses may not be accurately assessed. The objective of this work is to understand the impact that robust valve timing simulations, implemented using a fully coupled valve train dynamics and engine performance model, have on engine performance prediction. The integrated simulation and detailed technical approach are discussed through the presentation of an example implementation. An I4 engine model is developed in which engine performance and valvetrain dynamics modeling are coupled. A benefit of this multi-physics approach is that it reduces reliance on empirically derived estimates of valve lash in favor of physical modeling of engine valvetrain dynamics that predicts lash during engine performance modeling.
2016-04-05
Technical Paper
2016-01-1075
Jonathan Plail, Petr Grinac, Helen Ballard
Abstract In this paper, a mathematical model for simulating the 3D dynamic response of a valve spring is described. The 3D model employs a ‘geometrically exact’ 3D beam connected between each mass of the discretised mass-elastic system. Shear deformations within the beam are also considered, which makes it a Timoshenko type finite element. Results from the 3D model are compared with results from a more conventional 1D model. To validate the results further, some results are compared with real test data that was gathered during a technical consulting project. In this project, a prototype valvetrain that was originally giving acceptable durability began to wear the spring seats when a new batch of springs were procured and tested. 1D and 3D simulation results were used to help understand the cause of the failure and to make recommendations to resolve the issue. Results showed that the 3D model was able to predict the spring seat loads with greater precision than the 1D spring could.
2016-04-05
Technical Paper
2016-01-0906
Robert J. Middleton, Omnaath Guptha Harihara Gupta, Han-Yuan Chang, George Lavoie, Jason Martz
Abstract This study evaluates powertrain technologies capable of reducing light duty vehicle fuel consumption for compliance with 2025 CAFE standards. A fully integrated GT-Power engine model with physics based sub-models was developed to capture any positive or negative synergies between the technologies. The two zone multi-cylinder engine model included typical thermodynamic subroutines, with predictive combustion, flame quench and knock models, along with map-based turbocharger models to capture key combustion and efficiency behaviors. The engine model was calibrated to data from a boosted GDI engine and exercised through one series of current and production viable technology configurations for 2025 regulations.
2016-04-05
Technical Paper
2016-01-0891
Teri D. Kowalski, Satoshi Hirano, William A. Buscher, Eric Liu, Jerry C. Wang, James L. Linden
Abstract The study described in this paper covers the development of the Sequence IVB low-temperature valvetrain wear test as a replacement test platform for the existing ASTM D6891 Sequence IVA for the new engine oil category, ILSAC GF-6. The Sequence IVB Test uses a Toyota engine with dual overhead camshafts, direct-acting mechanical lifter valvetrain system. The original intent for the new test was to be a direct replacement for the Sequence IVA. Due to inherent differences in valvetrain system design between the Sequence IVA and IVB engines, it was necessary to alter existing test conditions to ensure adequate wear was produced on the valvetrain components to allow discrimination among the different lubricant formulations. A variety of test conditions and wear parameters were evaluated in the test development. Radioactive tracer technique (RATT) was used to determine the wear response of the test platform to various test conditions.
2015-11-17
Technical Paper
2015-32-0701
Takayuki Sugita
An existing 4 stroke-cycle gasoline engine has been partially modified without dynamically changing its mechanism for the purpose to utilize the compressed air as an alternative energy source. The principle is to mechanically control the compressed air flow through the intake and exhaust valve every revolution of a crankshaft by modifying the camshaft cam's lobes, which changes the engine operation from 4 strokes to 2 strokes cycle mode. In the previous investigation the principle was verified with a current 50 cc motorcycle modified engine and the pressure behavior inside the cylinder of the compressed air engine was evaluated. It turned out as a most promising result that the back pressure, which is defined as the positive pressure left in an expansion chamber while a piston is moving back from BDC to TDC, has a high influence on the performance of the compressed air reciprocating engine.
2015-11-17
Technical Paper
2015-32-0713
Denis Neher, Fino Scholl, Matthias Deinert, Maurice Kettner, Danny Schwarz, Markus Klaissle, Blanca Giménez Olavarría
Lean burn operation allows small cogeneration engines to achieve both high efficiency and low NOx emissions. While further mixture dilution enables future emission standards to be met, it leads to retarded combustion phasing and losses in indicated engine efficiency. In the case of naturally aspirated engines, IMEP drops due to lower fuel fraction, increasing brake specific fuel consumption. In this work, an alternative engine configuration was investigated that improves the trade-off between engine efficiency, NOx emissions and IMEP. It combines well-established means such as Miller/Atkinson valve timing and optimised intake system for a single-cylinder cogeneration engine, operating with homogenous lean air-natural gas mixture. First, the engine configuration was analysed using a detailed 1D CFD model, implying a significant potential in reaching the project target.
2015-09-22
Technical Paper
2015-36-0104
Fernanda Pinheiro Martins, Rogério H. Onoda, Henedino Gutierrez
Abstract This paper deals with the study of different design configurations for intake valves and valve seats on a current production cylinder head and their effect on airflow behavior and optimization, under steady flow condition. The analysis was performed trough a Design for Six-Sigma methodology (DFSS). The cases were simulated through computational fluid dynamics (CFD) software and a prototype considering the best configuration was built and tested at flow bench. Correlation between simulation and experimental data was performed in order to validate the results for current, as well as, for future studies. The goal is to determine how geometric design variations on intake valve profiles and valve seats affect airflow on the particular cylinder head.
2015-09-22
Technical Paper
2015-36-0477
Carmine Maria Di Sanctis, Waldyr Luiz Ribeiro Gallo
Abstract New devices and control techniques have been adopted to take advantage of variable valve timing properties to improve engine performance or load control. This paper presents a study focused on engine load control strategies associated with early intake valve closing or late intake valve closing. It can be shown that these load control modes can improve the indicated thermal efficiency of the engine as compared with the conventional throttle control. These strategies are sometime called Miller cycle or Atkinson cycle, since the real compression ratio becomes smaller than the expansion ratio. A thermodynamic spark-ignition engine simulation model was employed. The advantage of a simulation model is to conduct parametric studies without the need of complex experimental apparatus. In this way, a deep understanding of the physical phenomena can be achieved and the sole effect of the desired parameter can be shown.
2015-09-06
Journal Article
2015-24-2532
Reinhard Ratzberger, Thomas Kraxner, Jochen Pramhas, Klaus Hadl, Helmut Eichlseder, Ludwig Buergler
Abstract The continuously decreasing emission limits lead to a growing importance of exhaust aftertreatment in Diesel engines. Hence, methods for achieving a rapid catalyst light-off after engine cold start and for maintaining the catalyst temperature during low load operation will become more and more necessary. The present work evaluates several valve timing strategies concerning their ability for doing so. For this purpose, simulations as well as experimental investigations were conducted. A special focus of simulation was on pointing out the relevance of exhaust temperature, mass flow and enthalpy for these thermomanagement tasks. An increase of exhaust temperature is beneficial for both catalyst heat-up and maintaining catalyst temperature. In case of the exhaust mass flow, high values are advantageous only in case of a catalyst heat-up process, while maintaining catalyst temperature is supported by a low mass flow.
2015-09-01
Technical Paper
2015-01-1974
Lucas D Pugnali, Rui Chen
Abstract A 2-stroke combustion cycle has higher power output densities compared to a 4-stroke cycle counterpart. The modern down-sized 4-stroke engine design can greatly benefit from this attribute of the 2-stroke cycle. By using appropriate variable valvetrain, boosting, and direct fuel injection systems, both cycles can be feasibly implemented on the same engine platform. In this research study, two valve strategies for achieving a two-stroke cycle in a four-stroke engine have been studied. The first strategy is based on balanced compression and expansion strokes, while the gas exchange is done through two different strokes. The second approach is a novel 2-stroke combustion strategy - here referred to as 2-stroke Miller - which maintains the expansion as achieved in a 4-stroke cycle but suppresses the gas exchange into the compression stroke.
2015-04-14
Journal Article
2015-01-0677
Marcin Marek Okarmus, Rifat Keribar, Rob Zdrodowski, Arup Gangopadhyay
Abstract Valvetrain friction can represent a substantial portion of overall engine friction, especially at low operating speed. This paper describes the methodology for predictive modeling of frictional losses in the direct-acting mechanical bucket tappet-type valvetrain. The proposed modeling technique combines advanced mathematical models based on established theories of Hertzian contact, hydrodynamic and elastohydrodynamic lubrication (EHL), asperity contact of rough surfaces, flash temperature, and lubricant rheology with detailed measurements of lubricant properties and surface finish, driven by a detailed analysis of valvetrain system kinematics and dynamics. The contributions of individual friction components to the overall valvetrain frictional loss were identified and quantified. Calculated valvetrain friction was validated against motored valvetrain friction torque measurements on two engines.
2015-04-14
Technical Paper
2015-01-0323
Jörn Getzlaff, Tobias Dost, Thomas Lambert, Erik Lenk
Abstract The global development of oil prices and ongoing discussions with regard to meet future CO2-emission commitments necessitate new technologies and concepts in individual motor car traffic. While hybridization and electrification become more and more important on a small scale, the improvement in efficiency of conventional drive, especially in respect of SI engines, currently offers the highest potential in reducing fuel consumption and exhaust emissions. Thereby valve trains play a key role in the optimization of SI engines e. g. in connection with technologies and processes such as in-cylinder air-fuel mixing, combustion, HCCI, gas exchange, lean operation etc. Modern valve train systems entering mass production are despite of the fact of being called fully variable, yet cam-actuated systems. Thus variability and application are limited compared to direct (non-cam-actuated) engine control systems.
2015-01-14
Technical Paper
2015-26-0132
Ajay Paul John, Vikas Kumar Agarwal, Prashant Bhavsar
Abstract High fuel efficiency, low ownership/ maintenance cost and favorable driving climate are the major reasons for the increasing demand for low-power commuter motorcycles and scooters, particularly in developing countries like India, Brazil and China. Noise Vibration and Harshness (NVH) has now become a new subject for the battle between competing manufacturers in attracting customers. Valvetrain noise is quite significant in the engines of these cost gasoline vehicles as they don't incorporate a Hydraulic Lash Adjuster (HLA) to keep the manufacturing costs less. The aim of this study was to understand how the cam ramp velocity and height affects the noise generated by the engine and what effect they have on its performance.For this study, a small scooter gasoline engine with an Over Head Camshaft (OHC) and a rocker arrangement with a roller-follower was considered.
2015-01-14
Technical Paper
2015-26-0022
Rakesh Mulik, Sushil S Ramdasi
Abstract In the pursuit of design and development of efficient, reliable and durable system and components for modern engines, there is a need to understand complications involved in building mathematical models for simulation. Valve train and timing drive systems are having higher rankings for addressing these attributes. Hence, a new comprehensive multi body dynamics model is built and equations are solved by state-variable approach. Model developed is validated and in order to probe into details of Hydraulic Lash Adjuster (HLA) behavior and coupled analysis of timing chain drive systems for valve train system, simulation is carried out to freeze design options. Engine timing drives used in engines are one of the most critical systems. Timing chains are preferred widely in modern high speed engines as compared to timing belts and gear drives. In spite of advantages of chain drive systems, their complex dynamic behavior is not well researched.
2015-01-14
Technical Paper
2015-26-0189
Aniket Basu, Nitin Gokhale, Kedar Kanase, Yogesh Aghav, M N Kumar
Valve trains are highly burdened powertrain subsystem which has to undergo high fatigue cycles during its service lifespan. Wear enhances valve lash thus depreciating the performance drastically. Analytical advances have helped engineers to predict parameters such as wear, contact stresses, lubrication etc. to uphold the durability of valve train components. Most of the genset and industrial engines running at medium speed use type 5 valve train. In this paper, our study involves about crack induced “wear” due to Hertzian stress on rocker toe and the process followed to resolve the problem for a medium speed diesel engine We experienced the problem of rocker toe crack resulting in toe wear in field and on test bed. Our investigations led us to evaluate the life of a rocker toe by specifically developing a test cycle to reproduce the wear due to induced cracks as well as to assess the durability.
2014-10-13
Technical Paper
2014-01-2877
Ajay Paul John, Vikas Kumar Agarwal
Abstract The Valve Train system is an integral part of any engine and the impact of its design is very crucial, particularly in high speed engines. Maintaining the required valve timing throught the engine operating speed and longer component life are the two important parameters which drive current valvetrain designs. An engine ValveTrain system designed for a valve lift of 7mm is to be modified for an increased valve lift of 8mm. A study was conducted to understand which design parameters are to be changed /modified to make this possible. For this study, the valvetrain of an air-cooled motorcycle engine is taken up. The valvetrain arrangement was an Over Head Camshaft (OHC) design with a Roller-Follower. A 1D commercially available numerical code was used to simulate the kinematics and dynamics of the system.
2014-10-13
Journal Article
2014-01-2879
Wenjie Qin, Lunjing Duan
In order to predict cam wear in valve trains of engines quantitatively, multi-body system dynamic analysis, finite element quasi-statics contact analysis and numerical calculation of elastohydrodynamic lubrication are applied to obtain the dynamic loads, the time histories of contact pressure and the oil film thicknesses in a cam-tappet pair. Using this methodology, the wear depth of the cam in the valve train of a heavy load diesel engine is calculated, which is in good agreement with the measured value in the practical tests. The results show that the cam-tappet is operated in a mixed lubricant or a boundary lubricant regime and the wear depths on both the sides of the cam have been found to be the greatest.
2014-10-13
Technical Paper
2014-01-2873
Zhongmin Liu
Abstract As the key parameters, stiffness and damping coefficient significantly influence on dynamic simulation result, which is the mean method of valve train design. This research aims to investigate the relation between landing velocity (vL), contact duration (Δt), contact force (FN), friction force (FK), loss of valve kinetic energy (ΔWV) on the landing impact between valve and seat insert. Tests were carried out on Over-Head-Cam Valve-train (OHC). Firstly, valve and seat insert contact stiffness in static state was measured, nonlinear increasing of stiffness was observed, because of contact area changing with load. Secondly, valve and seat dynamic impact tests were carried out in different landing velocities. Based on valve contact model, contact force (FN), friction force (FK) and sliding distance (SL) were got by test data. As the result, contact stiffness and damping coefficient in dynamic state were analyzed.
2014-10-13
Technical Paper
2014-01-2876
Krzysztof Jan Siczek, Andrzej Stefanski
Abstract The scope of the study is limited to the period of closing valve, but phenomena existing in the antecedent phase influence conditions in the contact between seats. Friction type in such contact varies from mixed to boundary or even dry one, depending on the amount of oil and wear debris wherein. The operational conditions for inlet and outlet valve are different because of temperature in contact and deposition of carbon deposits. The complexity the phenomena in contact zone, including valve rotation makes difficult the modeling of friction. The valve rotation is considered only in macro scale and the other displacements of seats in micro and macro scale. The initial shape of seats resulted from grinding and lapping process varies during impacting and abrasion wear.
2014-10-13
Technical Paper
2014-01-2874
Sunyu Tong, Xianjing Li, Shuai Liu, Jun Deng, Zongjie Hu, Gong Li, Liguang Li
Abstract Reducing the pumping loss, and thus, the fuel consumption of gasoline engine at part load, a two-stage intake valve lift system was implanted into a PFI engine. A corresponding engine model was set up with GT-power as well, which can simulate the effect of two-stage intake valve lift and different EGR rates on fuel economy performance and on combustion condition of a gasoline engine. Based on simulation results, the valve lift control strategy and EGR control strategy was studied in this paper. Results showed that at low engine speed, when SMALL LIFT was used, the tumble flow and the combustion process in cylinder was improved and burn time duration became shorter, resulting in higher indicated efficiency and lower fuel consumption than by LARGE LIFT. With the introduction of the exhaust gas recirculation (EGR), lower fuel consumption was acquired.
2014-09-30
Technical Paper
2014-36-0286
Evandro de Almeida Leme, Alfons R. Wagner, Anderson Gutierres, Gilson Santos, Henrico Gouvea da Silva
Abstract A significant percentage of energy is lost in internal combustion engines due to valve train friction. The reduction of friction losses of a valve train is an important factor to improve significantly fuel efficiency and consequently emissions reduction. The friction loss of valve train includes the losses of the individual components and factors, such as spring load, temperature, lubricant type, mass of components, operating conditions and others. The breakdown of the friction within the valve train is necessary for the implementation of effective optimization measures. This paper presents an analysis of some influence factors associated to friction loss, utilizing the Design of Experiments approach. The results are based on dynamic measurements on a single overhead camshaft (OHC) engine valve train, performed on a test rig developed for friction torque measurements.
2014-09-30
Technical Paper
2014-36-0231
Rubens Gonçalves Salsa Junior, Robson Pederiva
Abstract Over the years, internal combustion engines have been researched and improved in the search for more power and for lower fuel consumption. An automotive subsystem that directly affects the performance of the engine is the valve train system. This system allows for the control of the admittance and release of gases from the combustion chamber. This system operates in all phases, ensuring that the valves open and close properly and ensuring the sealing of the cylinder. Several researchers have studied the kinematics and dynamics of the valve actuation system to improve engine performance. As the actuation of the valves occurs usually by cams, every movement and timing of the system is dictated by the design characteristics of the profile of the cams: it has a predominant action on the dynamics of the system.
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