Browse Topic: Camshafts

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Cryogenic Cam Butterfly ValveTBMG-345966/1/2019
Typical butterfly valves cannot seal at both ambient and cryogenic temperatures. At cryogenic temperatures, valves grow and shrink, changing critical dimensions such as distance between the disc and seat. Ideally, valves would compensate. The inability of existing butterfly valves to do this led to the design of the Cryogenic Cam Butterfly Valve (CCBV) in which the disc rides on a cam shaft and is held rigid by a torsion spring that provides both axial movement of the disc in addition to the standard 90-degree rotation of a standard butterfly valve. Because the valve’s disc can rotate and translate, it can hold a tighter seal, preventing leakage despite dimensional changes caused by changing operating temperatures.
Design and Development of a Roller Follower Hydraulic Lash Adjustor to Eliminate Lash Adjustment and Reduce Noise in a Serial Production Diesel Engine2018-01-17669/10/2018
Commercial vehicles require continual improvements in order to meet fuel emission standards, improve diesel aftertreatment system performance and optimize vehicle fuel economy. Aftertreatment systems require significant space claim which makes vehicle packaging a challenge. Today’s diesel engines require valvetrain lash adjustment settings at distinct intervals to ensure proper valvetrain performance. This requires removing the engine rocker cover to access the valvetrain rocker arms for setting lash. Setting lash for compact vehicle applications sometimes requires removing the aftertreatment system to provide access to the rocker cover prior to setting lash. Then, the rocker cover is reinstalled followed by the aftertreatment system making the lash setting process time consuming and complex. This paper focuses on the design, development and validation of adapting hydraulic lash adjusters (HLAs) into a type V (camshaft in block) diesel engine thus eliminating the lash adjustment process. The flat mechanical tappets were replaced with roller follower HLAs on both the intake and exhaust valves. The roller was included to reduce valvetrain friction over flat tappets. An anti-rotation design was included to maintain alignment between the roller and the camshaft. A major advantage of using the HLA was reduced engine valvetrain noise. Minor engine block changes were required to accommodate the roller follower HLAs. The HLA design ensured reliable and repeatable valve motion from engine build thru cold start and normal engine operation over the useful life of the engine. Reliability was key for the roller follower HLA as it is embedded inside the block which makes replacement impractical. This paper highlights the major design aspects for including roller follower HLAs in a type V diesel engine.
Roberts, Leighton, McCarthy, Jr., James
Power Cylinder Friction: MechanismsJ2904_201805 (Historical)5/16/2018
This document covers the mechanisms from the power cylinder which contribute to the mechanical friction of an internal combustion engine. It will not discuss in detail the influence of other engine components or engine driven accessories on friction.
Piston and Ring Standards Committee
Influence of Miller Cycles on Engine Air Flow03-11-02-00114/18/2018
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.
Braun, Marco, Klaas, Michael, Schröder, Wolfgang
Testing and Implementation of a Turbocharged Formula SAE Vehicle2018-01-09674/3/2018
Research on turbocharging for FSAE at the University of Malta, has been ongoing for a number of years. 1D simulations were done to determine best design configuration and determine a lowered compression ratio. A decompression plate was installed on the Kawasaki 600 cc engine. Calibration of the engine was performed on the engine dynamometer. A hot-gas test stand for testing of the turbocharger was developed. The turbocharger speed was measured by a custom built hall-effect sensing setup that is compact enough to be implemented also in the FSAE vehicle. Bespoke camshafts with optimized valve timing determined through WAVE 1D simulations and designed with Valdyn® were machined. The turbocharged setup was used on the University of Malta FSAE vehicle in the FSAE Italy 2017 competition. Knock was investigated through in-cylinder pressure measurements and use of commercial knock sensor on the 600 cc engine. Benchmarking in-cylinder pressure measurement tests were carried out on a 1.4 liter naturally aspirated Ford engine for both ‘masked’ and ‘unmasked’ in-cylinder pressure sensors to assess the possibility and effect of cavity resonance in such experimental tests. High speed data acquisition was performed at 200 kHz per channel and was post-processed using LabVIEW®. Calibration of the knock detection feature on the programmable ECU required the determination of the relevant parameters namely: knock frequency, reference and knock windows and knock to reference window amplitude ratio. Calibration of the ECU knock parameters was aided by playing back recorded engine sensor data to minimize the time of engine knocking.
Azzopardi, Jean Paul, Farrugia, Jean-Paul, Caruana, Carl, Grech, Nicholas, Farrugia, Nicholas, Chircop, Marlon, Farrugia, Mario, Farrugia, Michael
Torsional Vibration Reduction for Geared Aviation Compression Ignition Engines with Power Transmission Through the Camshaft or Dedicated Internal Driveshaft A Sweep Through 2 and 4-Stroke Engines with Differing Numbers of Cylinders and Two Comparison Power Train Configurations Indicate the 4-Stroke, 6-Cylinder Engine is Ideally Suited for this Application2017-01-18086/5/2017
In a previous report, it was shown that power transmission through the camshaft reduced the first mode natural frequency of the power train and translated its convergence with dominant engine excitatory harmonics to a lower engine speed resulting in a marked reduction in torsional vibration while achieving 2/1 gear reduction for a 4-stroke 6-cylinder compression ignition (CI) engine for aviation. This report describes a sweep though 2 and 4-stroke engines with differing numbers of cylinders configured as standard gear reduction (SGRE) and with power transmission through the camshaft (CDSE) or an equivalent dedicated internal driveshaft (DISE). Four and 6-cylinder 4-stroke engines were modeled as opposed boxer engines. Four and 6-cylinder 2-stroke engines and 8, 10 and 12-cylinder 2-stroke and 4-stroke engines were modeled as 180° V-engines. All 2-stroke engines were considered to be piston ported and configured as SGRE or DISE. All 4-stroke engines were configured as SGRE or CDSE. Mass-elastic models of the different engine power train configurations were constructed and analyzed using the torsional vibration module in Shaft Designer obtained from SKF (Svenska Kullagerfabriken). Maximum torsional stress at the power train segments was used to discriminate between the different configurations. The best 4-stroke CDSE configuration was the 6-cylinder engine as described previously and provided a significant advantage over the SGRE configuration. The best 2-stroke applications with the analogous DISE configurations were the 8 and 10-cylinder engines although they were inferior to the SGRE configurations. These simulation studies suggest that the 6-cylinder 4-stroke engine is ideally suited for use with the CDSE power train configuration for reduction of torsional vibration and achieving gear reduction compared with SGRE.
Nardella, Francis
Analysis of Engine Flywheel Wobbling Vibration2017-01-10233/28/2017
Large axial displacement at the edge of a flywheel causes a clutch to fail to disengage in high-speed rotation. To find out the root cause, a numerical procedure is proposed to investigate the vibration source and to understand dynamic behavior of the crank-train system. A simulation of the whole engine system including block, crankshaft, piston, and connecting rod was performed with AVL/Excite. The resulting CAE baseline model had good correlation with measurements. A comprehensive study was conducted for a set of flywheel and crankshaft models with different materials and unbalanced masses. The contribution to flywheel wobbling of each vibration order was carefully investigated, and an optimal design was presented.
Jiang, Yaqun, Hsieh, C., Festag, Georg, Ahmed, Masood, Jiang, William
Valvetrain Ticking Noise Analysis2017-01-10573/28/2017
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.
Zeng, Paul, Paul, Debabrata, Solferino, Vincent, Stickler, Mark
A Finite Element Method for Camshaft Cap Durability Analysis2017-01-03413/28/2017
In this study, a finite element analysis method is developed for simulating a camshaft cap punching bench test. Stiffness results of simulated camshaft cap component are correlated with test data and used to validate the model accuracy in terms of material and boundary conditions. Next, the method is used for verification of cap design and durability performance improvement. In order to improve the computational efficiency of the finite element analysis, the punch is replaced by equivalent trigonometric distributed loads. The sensitivity of the finite element predicted strains for different trigonometric pressure distribution functions is also investigated and compared to strain gage measured values. A number of equivalent stress criteria are also used for fatigue safety factor calculations. The severity of the loading experienced by the camshaft caps depends on whether the under study cap is on intake or exhaust camshaft side as well as the location of the associated cylinder on the engine. Design suggestions are given to meet cap durability requirements, based on engine bank and camshaft cap numbers.
Mortazavian, Seyyedvahid, Moraveji, Javid, Adimi, Reda, Chen, Xingfu
Crack Failure Mode Analysis for Cam-Housing Rocker Arm and Pin2017-01-03583/28/2017
During the extensive testing under NATO and Commercial Standards, crack is observed in camshaft housing to initiate from the eccentric shaft bore and go toward the hold down bolt hole. Hence lab test proposal is originated to induce similar failure in a controlled method and then to compare new design alternatives. CAE analysis follows the same set up as the lab test to duplicate failure mode in stress analysis and fatigue analysis with duty cycle loads, and then figures out two strategies on how to improve the design, including geometry change and material change. In geometry wise, four new design iterations are evaluated for comparison. In material wise, one new material for camshaft housing and five manufacturing effect parameters for pin and rocker arm are compared, including ground, machined, machined and decarburization, casting, as well as casting and nitride. With those comparisons, all manufacturing parameters are compared based on effectiveness to affect the fatigue life. Besides design change, manufacturing cost is also prone to be a relatively critical factor. By all means above, the new architecture is decided and successfully validated by the following testing and can meet production criteria as well. The CAE software applied in the analyses are Abaqus for stress analysis and nCode DesignLife for fatigue analysis.
Song, G
DigitalAir™ Camless FVVA System – Part 1, Valve Train Design, Capability and Performance2017-01-06353/28/2017
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. This design arrangement avoids the risk of poppet valve to piston collision, or the need for cut-outs in the piston crown, since the valves do not open into the cylinder. The results from the analytical models used to predict the performance of the valve train are presented and compared with experimental data (when available). JP SCOPE Inc. has been running engines with this valve train for several years and has successfully completed preliminary performance and durability tests. Part 2 of this paper [1] will present analytical and experimental data which confirms that the proposed FVVA system can meet the basic performance requirements of modern GTDI engines.
Babbitt, Guy, Rogers, Jeff, Weyer, Kristina, Cohen, Drew, Charlton, Stephen
Gear Whine Noise Due to Deformation- A Case Study2017-01-11223/28/2017
Vehicle noise has reduced over the years due to the customer demand for quieter vehicles. As the background noises such as combustion noise, pumping noise, etc. have reduced, mechanical noises such as gear noise have become prominent and a major cause of customer complaints. Engine timing gear train uses gears for transferring torque to cam and accessory gears. As engines have become quieter by efforts to reduce the combustion noise, as well as, by moving away from mechanical fuel pumps to common rail fuel pumps, the gear train noise has come under increased scrutiny. Gear whine could be a result of multiple factors. Gear profile distortion is one of the factors. Gear torque variation also has a significant effect on gear whine. Operation of the accessory drives such as hydraulic pumps under variable loads and speeds, is one of the major challenges for resolving a gear whine issue in the engine gear train. ISO 10064 provides guidance on the distortion due to temperature effects, but there is not much published literature about gear whine due to distortion. The work attempts to fill that gap by describing a gear whine problem due to profile distortion and load change and its resolution by changing the gear design.
Joshi, Yashodhan V.
Test Component SpecificationsJ1802/1_201607 (Current)7/27/2016
This SAE Recommended Practice contains the reference information for SAE J1802.
Truck and Bus Foundation Brake Committee
Design and Optimization of Web Fillets for Commercial Vehicle Crankshaft for Improving SCF and Theoretically Correlated2016-01-13424/5/2016
Crankshaft is one of the critical components of an engine (5C: cylinder head, connecting rod, crankshaft, camshaft and cylinder block). It is subjected to repetitive and dynamic loads due to cyclic operation of an engine and inertia forces. Due to uneven mass distribution, failure zones occur near fillets and holes in journal locations during operation of the engine. Hence, this topic was chosen because of increasing interest in higher payloads, lower weight, higher efficiency and shorter load cycles in crankshaft equipment. Calculation of Crankshaft strength consists initially in determining the nominal alternating bending and nominal alternating torsional stresses, which multiplied by the appropriate SCF (Stress Concentration Factor), result in an equivalent alternating stress. This equivalent alternating stress is then compared with the fatigue strength of the selected crankshaft material. This comparison will show whether or not the crankshaft concerned is dimensioned adequately. Hence, SCF is main focus point. The present study emphasizes on a CAE based approach for prediction of SCF for crankshaft web fillets. Using FE Solver (Optistruct), the dimensions and shape of the web fillet are optimized for Improving SCF. On the basis of the analysis various design parameters of web fillet are determined and finally the results obtained from FE analysis were theoretically validated.
Kandreegula, Suresh Kumar, Mukherjee, Sayak, Paroche, Sonu, Ayyar, Diwakar, Gupta, Umashanker
Durability and Reliability Demonstration for Switching Roller Finger Follower in Cylinder Deactivation Systems2015-01-28169/29/2015
Cylinder deactivation (CDA) is an effective method to adjust the engine displacement for maximum output and improve fuel economy by adjusting the number of active cylinders in combustion engines. A Switching Roller Finger Follower (SRFF) is an economic solution for CDA that minimizes changes and preserves the overall width, height, or length of Dual Overhead Cam (DOHC) engines. The CDA SRFF provides the flexibility of either transferring or suppressing the camshaft movement to the valves influencing the engine performance and fuel economy by reducing the pumping losses. This paper addresses the performance and durability of the CDA SRFF system to meet the reliability for gasoline passenger car engines. Extensive tests were conducted to demonstrate the dynamic stability at high engine speeds and the system capacity of switching between high and low engine displacement within one camshaft revolution. The system durability was demonstrated with high and low engine speeds, various oil temperatures, mode switching, and abuse tests, meeting the end of life criteria in wear and function. System robustness to dimensional variation was tested to understand the effect on performance and durability. Lash increase, one important metric for wear evaluation, was monitored during durability and abuse tests. Multiple life tests were performed to demonstrate the system reliability of 99.94% over the engine's useful life. Test results show a robust design for performance, durability, and reliability for passenger car applications.
Radulescu, Andrei, Roberts, Leighton, Yankovic, Eric
Synergy between Boost and Valve Timings in a Highly Boosted Direct Injection Gasoline Engine Operating with Miller Cycle2015-01-12624/14/2015
Gasoline engine downsizing has become a popular and effective approach to reduce CO2 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. 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. 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.
Li, Yuanping, Zhao, Hua, Stansfield, Phil, Freeland, Paul
A Model Based Design Analysis for a Gasoline Direct Injection Pump2015-01-12674/14/2015
A high-pressure fuel pump in a GDI (Gasoline Direct Injection) engine has been increasingly applied on passenger vehicles because of its high fuel efficiency and reduction of exhaust emissions. The design specifications of principal components of GDI high-pressure pump should be validated prior to the manufacturing. This study presents the analytical results of the specifications for the design of a GDI pump of Motonic Co. by using computational model based simulation. The results are largely divided into two parts. First, cam-follower dynamics with the proper design of cam profile, and second, the discharge flow performance of the pump in consideration of the characteristics of inlet control valve.
Lee, Jae-Cheon, Liu, Hao, Noh, Yoo-Jeong, Shin, Hyun Myung, Shin, Yong Nam, Kang, Myung Kweon
MMLV: Carbon Fiber Composite Engine Parts2015-01-12394/14/2015
While weight reduction in automotive design and manufacturing has been on-going for several years, in the area of powertrain technology lightweighting has been a difficult challenge to overcome due to functional requirements, as well as material and manufacturing constraints. The Multi Material Lightweight Vehicle (MMLV) developed by Magna International and Ford Motor Company is a result of US Department of Energy project DE-EE0005574. The project demonstrates the lightweighting potential of a five passenger sedan, while maintaining vehicle performance and occupant safety. Prototype vehicles were manufactured and limited full vehicle testing was conducted. The Mach-I vehicle design, comprised of commercially available materials and production processes, achieved a 364kg (23.5%) full vehicle mass reduction, enabling the application of a 1.0-liter three-cylinder engine resulting in a significant environmental benefit and fuel reduction. Ford Motor Company worked with material supplier, BASF Corporation, plus Montaplast GmbH, Hexion Inc., and WGS Global Services LC to design and develop the carbon fiber composite Front Cover, Oil Pan and Cam Carrier based off the production Ford 1.0L I3 EcoBoost engine. The reduced mass Front Cover and Oil Pan were both structurally strong enough to support the engine mount attachment and to meet all the powertrain bending stress targets present in the production engine. The final parts achieved a significant weight reduction of 24% for the Front Cover and 33% for the Oil Pan. The Cam Carrier uses a carbon fiber composite material with an innovative split cylinder head design that allows the upper cylinder head section referred to as the cam carrier to support the camshafts and valvetrain components independently from the lower section of the cylinder head. The splitting of the cylinder head facilitates the use of two different materials that meet the functional design requirements. The upper section or the cam carrier provides a 15% mass reduction and the lower section of the cylinder head is cast from aluminum material that will support the high peak cylinder pressures that occur in a GTDI engine.
Corey, Neal J., Madin, Mark, Williams, Rick L.
Experimental Investigation of Variable Geometry Compressor for Highly Boosted Gasoline Engines2015-01-12894/14/2015
A key technology for further improving the efficiency of gasoline engines lies in downsizing in combination with turbocharging. Decreasing the engine displacement greatly increases the demands on the turbocharging system. The charging of the engine with a single-stage turbocharger leads to a compromise to fulfill the requirements of the nominal power of the engine and the low-end torque. To avoid the use of complex two-stage boosting systems, it is necessary to increase the pressure ratio and the air flow rate at the same time. The wide speed and airflow range of gasoline engines intensify this trade-off. The use of a variable geometry turbine (VGT), additionally equipped with a wastegate bypass, offers great potential to meet the requirements on the turbine side. The range of stable operation of the compressor is limited by choke at high mass flow rates and surge at low mass flow rates. The variable geometry compressor (VGC) is one promising approach to extend the compressor map. A variable charging system consisting of VGC and VGT offers great potential to meet the future requirement for highly boosted engines. The present paper shows experimental investigations of the potential of a variable geometry turbine with an additional wastegate on a small sized gasoline engine. To reach the torque and nominal power characteristic of a 2-stage boosted reference engine, the test engine is additionally equipped with a camshaft phasing system on the exhaust side. In addition two different variable geometry compressors are investigated.
Herbst, Fabian, Eilts, Peter
Development of the Combustion System for General Motors' High-Efficiency Range Extender Ecotec Small Gas Engine2015-01-12724/14/2015
General Motors has developed an all-new Ecotec 1.5 L range extender engine for use in the 2016 next generation Voltec propulsion system. This engine is part of a new Ecotec family of small displacement gasoline engines introduced in the 2015 model year. Major enhancements over the range extender engine in the current generation Voltec propulsion system include the adoption of direct injection (DI), cooled external exhaust gas recirculation (EGR), and a high 12.5:1 geometric compression ratio (CR). Additional enhancements include the adoption of high-authority phasers on both the intake and exhaust camshafts, and an integrated exhaust manifold (IEM). The combination of DI with cooled EGR has enabled significant thermal efficiency gains over the 1.4 L range extender engine in the current generation Voltec propulsion system at high engine loads. The addition of a high geometric CR and high-authority camshaft phasers for extended late intake valve closing (LIVC) operation has enabled improved low- and mid-load engine efficiency. The combination of DI and high-authority camshaft phasers has minimized the full-load engine torque loss inherent with traditional high CR and LIVC implementations. The combustion system was developed with extensive use of computational fluid dynamics (CFD) simulation for optimization of in-cylinder mixing and combustion. These tools aided in the sorting and selection of the combustion chamber, ports, piston, and fuel injector. Extensive single- and multi-cylinder engine testing and development was also employed to refine and optimize the engine combustion system.
Jocsak, Jeffrey, White, David, Armand, Cedric, Davis, Richard S.
Improvement of the Startability with Reverse Stroke Intake Devices for a Motorcycle Engine2014-32-010711/11/2014
This paper proposes a novel engine starter system composed of a small-power electric motor and a simple mechanical valve train. The system makes it possible to design more efficient starters than conventional systems, and it is especially effective to restart engines equipped with idling stop systems. Recently, several idling stop systems, having intelligent start-up functions and highly-efficient generate capabilities have been proposed for motorcycles. One of challenges of the idling stop systems is the downsizing of electric motors for starting-up. However, there are many limitations to downsize the electric motors in the conventional idling stop systems, since the systems utilize the forward-rotational torque of the electric motors to compress the air-fuel mixture gas in the cylinders. Our studies exceeded the limitations of downsizing the electric motors by mainly using the engine combustion energy instead of the electric energy to go over the first compression top dead center. The starter system described in this paper consists of (A) an electric motor which can rotate an engine crank shaft in normal or reverse directions, (B) a valve train to initiate the intake valve during the exhaust stroke in the reverse rotation, and (C) a control unit to inject and ignite at arbitrary timing. Then, this engine starts-up with the following: (1) the electric motor rotates the crank shaft in the reverse direction, (2) a fuel is injected to the intake port, (3) a generated air-fuel mixture gas is led to the cylinder from the intake port during the exhaust stroke, and (4) the air-fuel mixture gas is ignited in the expansion stroke. Since the ignition generates the combustion energy to push back the piston, the piston is forced to be fallen down and the crank shaft is driven in the normal direction. At last the piston goes over the first compression top dead center by the normal-direction without the torque of the starter motor. After that it begins the normal operation. The mechanism above can decrease the required time and the required torque to start-up the engine, and it leads to the downsizing of the starter motor, as well as a reduction in the battery consumption. When the mechanism is applied to starter-generator systems for motorcycles, the excess capability of the electric generation can be suppressed because it is not necessary to install the large-power starter-generators.
Masuda, Takahiro, Sakai, Kouji, Yamaguchi, Yuki, Kaku, Jun-ichi, Nagasaka, Hirobumi
Development of New Cam-Shower for Oil Flow Optimization2014-01-285110/13/2014
On internal combustion engines, the intake and exhaust valves are reciprocated by the cam mechanism. ‘Cam-shower’ is oil supplying device for each cam of a camshaft. The conventional cam-shower is simple pipe shape with several same size outlets for each cam. Oil from cylinder head is supplied in the middle point of cam-shower pipe. The oil flow of outlets near the oil supplied point is large amount, and outlet far from supplied point is small. The distribution of oil flow from each outlet is uneven. A new structure of cam-shower has been developed, and it has two important features. First, it has branched oil passage like cereoid cactus. Second, supplied oil flow from cylinder head to a cam-shower is intermittent by using throughhole passage in a camshaft journal. The new developed cam-shower properly distributes oil flow to each cam evenly and reduces wasted oil flow, so that total amount of oil flow of the cam-shower can be remarkably reduced by 90%. Then small discharge rate of the oil pump for engine can be set up and its driving torque gets lower. Eventually, that achieves low fuel consumption of engine.
Hikita, Yasuhiro, Kawahara, Masahiro, Noguchi, Naoto
Evaluation and Comparative Study of ValveTrain Layouts with Different Rocker Ratio2014-01-287710/13/2014
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. The effect of the addition of stiffer springs to the base valvetrain layout to counter the decrease in its dynamic stability because of the larger cam (which was provided to produce the required 8mm valvelift) is studied. Also the outcome of increasing the Rocker Arm Ratio (RAR) and how it alters the dynamic behavior of the valve train was understood. RAR is the ratio of the length of the valve side of the rocker arm to the pivot and the length of the follower-roller to the rocker pivot. Increasing the RAR is an effective way of increasing the valvelift of the engine (hence it's breathing capacity) with the same cam profile. Also because of the increased RAR, undesirable valve dynamic phenomenon such as valve float would occur later in the rpm range, hence aiding in the dynamic stability of high speed engine valvetrain. But by increasing the RAR, the forces and Hertz stress generated at the cam/follower interface will also increase. In this paper Valvetrain layouts with three different rocker ratios i.e. 1.2, 1.5 and 1.8 were studied. Also two spring designs were evaluated on these rocker designs. How the change of RAR and the spring stiffness affects the valve dynamic phenomenon like valve bounce, valve float and how it alters the valve train forces and stresses were understood. From this study an optimized rocker ratio with suitable spring design is suggested for the considered engine.
John, Ajay Paul, Agarwal, Vikas Kumar
Evaluation of Camshaft Control Strategies for a GDI Engine using a Multidisciplinary Optimisation Framework2014-01-258110/13/2014
This paper presents a calibration optimization study for a Gasoline Direct Injection engine based on a multidisciplinary design optimization (MDO) framework. The paper presents the experimental framework used for the GDI engine mapping, followed by an analysis of the calibration optimization problem. The merits of the MDO approach to calibration optimization are discussed in comparison with a conventional two-stage approach based on local trade-off optimization analysis, focused on a representative emissions drive cycle (NEDC) and limited part load engine operation. The benefits from using the MDO optimisation framework are further illustrated with a study of relative effectiveness of different camshaft timing control strategies (twin independent Versus fixed timing, exhaust only, inlet only and fixed overlap / dual equal) for the reference GDI engine based on the part load test data. The main conclusion is that the MDO structure offers an effective framework for the GDI steady state calibration optimization analysis.
Kianifar, Mohammed Reza, Campean, Felician, Richardson, David
Online Oil Dilution Measurement at GDI Engines2014-01-259110/13/2014
In coming years a special focus in the field of GDI engines will be on downsized concepts and highly-charged gasoline direct injection engines. This is due to stricter emission laws, higher customer requirements, greater environmental awareness as well as high demands on materials and resources. Especially at cold start, catalyst heating and warm up operation GDI engines have an issue with oil dilution. Fuel gets into the oil pan and is mixed with the engine oil so that the physical and chemical properties of the engine oil are changed. Adjusting engine operating points to higher mean effective pressures in downsizing concepts also an additional increase of the fuel input into the engine oil occurs. At the University of Applied Sciences Regensburg measurements were carried out at a direct injected gasoline engine with lateral injector position. This engine with 1.8 l displacement disposes e.g. a common rail injection system up to 20 MPa, a variable camshaft regulation and a variable tumble system. For the following investigations a new measurement technique has been used that realizes the online analysis of the fuel quantity in the engine oil. In order to study the oil dilution mechanisms and the influence of different adjustment parameters investigations were carried out especially at engine operating conditions with high oil dilution risk. Besides the studies on steady-state operating points, it is possible to investigate transient engine operation referring to its issue on oil dilution. Due to its high precision and low detection limit the used online measurement technique provides quantitative information about the fuel sorption and desorption rates at short measurement times. Defining a generic measurement procedure in order to receive a representative value of oil dilution for one specific engine operating parameter was the basic principle for further investigations. Operating parameters such as injection pressure and injection timing, charge motion, cooling temperature and different cam timings have been explored regarding their influence on oil dilution. Thus an optimized oil diluting calibration could be developed at each critical engine operation point.
Kleiner, Florian, Kaspar, Marcel, Artmann, Christina, Rabl, Hans-Peter
Valve Spring Compression Testing System2014-36-02309/30/2014
The compression springs of the valves of automotive engines are key elements in the dynamic behavior of the engine. Its wear is slow, gradual and progressive; so the driver of the vehicle eventually get used to the decrease in the engine performance. The compressive force losses cause the valves to close slower than expected and, consequently, the engines lose their efficiency. Professionals in the area of automotive maintenance apply empirical tests with varying criteria to evaluate and to determine the life cycle end at which the springs must be replaced. This article describes the development of a workbench for compression springs based on existing models on the market and the main premise is the low cost. Correspondent loads involved were determined and the components were modeled in CAD, allowing to develop a robust device able to handle the loads generated by the compression spring. The load is applied by means of a lever and the spring deflection is measured by a digital caliper and the load by a load cell. This information is sent to an embedded system that instantly shows the information on a display. The spring load is evaluated on its mounting position (compression height) and also at the point of maximum lift of the camshaft.
Vandresen, Marcelo, Lencina, Diovani C., Fernandes, Carolina P., Silva, Luana N., Feliciano, Lucas D. P., Cazangi, Humberto R.
Power Cylinder Blow-by: Problem SolvingJ2798_201408 (Historical)8/5/2014
This document describes methodologies to determine the causes blow-by oil consumption caused by the power cylinder.
Piston and Ring Standards Committee
Augmenting Light Weighting Horizon in Automotive2014-28-00234/28/2014
Better ride and comfort, enhanced safety, reliability and durability, lower running cost as well as cost of ownership continue to be challenges for automotive OEMs. Higher fuel efficiency is considered as USP not only for lower running cost but also is hygiene factor from sustainability point of view. This has necessitated the need for Augmenting Light weighting horizon in automotive OEMs. Augmenting this leads to invention of innovative materials and processes for emerging cost competitive market. This paper focuses on technology efforts towards augmenting light weighting Horizon in Automotive. Light weighting concepts being explored by OEMs with the help of automotive component manufacturers from Powertrain - Engines & Transmission, Chassis and Suspension are discussed. The Innovative concepts and case studies covered include Hollow Crankshaft and Camshafts, PM gears, composite / bimetallic brake drum, steering knuckle & leaf spring, hollow Anti Roll Bar (ARB) & Front Axle Beams (FAB), high strength polymers for fuel tank etc.
Raghvendra, G, Shende, Deodatta, Pathak, Udayan
F2E - Ultra High Pressure Distributed Pump Common Rail System2014-01-14404/1/2014
Delphi Diesel Systems' 2700bar Proven F2E Distributed Pump Common Rail System (DPCRS) has been developed to meet the requirements of Euro VI and future emissions legislation and is now in volume production in Heavy Duty Vehicles. Incorporating a number of ground breaking new technologies, the system offers numerous performance advantages. F2E provides full common rail functionality for camshaft driven Fuel Injection Equipment (FIE) engines with minimum modification. By delivering precise and accurate control of multiple injections at maximum rail pressure across all engine operating conditions, the system minimizes the demands on exhaust after treatment systems. Additionally F2E provides real time flexible capacity by employing a unique method of pump fuel metering, enabling the most efficient and accurate transient control of rail pressure combined with the low NVH and optimised efficiency.
Meek, George A., Williams, Ryan, Thornton, Dan, Knapp, Patrick, Cosser, Stephen
Valve Lift Profile Development and Optimization Using Matlab2013-01-17224/8/2013
The focus of this paper is the development and modelling of a reverse-poppet valve train assembly, placing a major emphasis on the optimization routine used to develop a short-duration camshaft profile. A user-programmable script, known as the penalty function, was written to assign weighted numeric values to certain parameters associated with the valve lift profile and its derivatives. These design parameters include maximum acceleration, peak lift, area under the lift curve and minimization of jerk. Optimization tools built into Matlab were then used to generate a profile which minimizes the overall ‘penalty’ associated with each parameter as it deviates from a user-defined ideal. A commercially available multi-body dynamics software package was used to evaluate the dynamic performance of the valve train incorporating the generated cam profile. A flexible-body spring element provided insight into spring surge and coil contact. Comparisons of the designed and simulated lift, velocity and acceleration profiles are given.
Cameron, Iain, Minaker, Bruce
A Study on the Dynamic Characteristics of a Single-body Hydraulic Lash Adjuster under Aeration2013-01-17234/8/2013
To accurately simulate valve behavior in an engine employing a Hydraulic Lash Adjuster (HLA), it is necessary to reflect in the simulation model the dynamic characteristics of the HLA when feeding aerated engine oil. Traditionally HLA behavior was measured by agitating oil to aerate it inside an actual engine. With this technique, however, the aeration rate cannot be controlled to allow an examination of the relationship between aeration rate and HLA behavior. This study aims to establish a technique for obtaining HLA dynamic characteristics when oil contains air. We created an aeration device that allows free control of the oil aeration rate and, by applying excitation input to the plunger, revealed the relationship between oil aeration rate and the changes in HLA stiffness. Because of the small clearance between the HLA plunger and its housing, it is difficult for air to escape from low-temperature oil inside the HLA high-pressure chamber, which greatly affects HLA behavior.
Yoshii, Kenta, Kawano, Masaru, Yanagisawa, Nagao
Kinematic Modeling and Analysis of a Cam Based CVT2013-01-13714/8/2013
Continuously variable transmission (CVT) offers many advantages to vehicle performance over traditional transmission technologies. A novel cam based CVT was proposed in US patent # 4,603,240, by J. Klovstad and J. Fortune [1], which has a cam input to drive an angle dependent, clutch actuated output shaft. Based on the patented CVT, a kinematic simulation, utilizing three dimensional CAD software was performed, creating a visualization and analysis model to ascertain system performance and feasibility. This article describes the mechanism created, limitation of the modeling software and the approach utilized to overcome these limitations. The resultant motion is then analyzed to ascertain the performance of the mechanism and determine the viability of the design concept. Key improvements to the system are proposed to the design, based on system performance through this analysis.
Hickman, Gregory Fitzpatrick, Gu, Randy, Chang, Yin-Ping
Compressed Air as a Quality and Pollution Free Fuel Substitute in Reciprocating Engines - an Effect of the Cam Profile on the Engine Performance2012-32-006010/23/2012
An existing 4 stroke-cycle gasoline engine has been partially modified without dynamically changing its mechanism for the purpose to utilize compressed air as an alternative energy source. The principle is to mechanically control the compressed air flow through the intake and exhaust valves every revolution of the 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 the expansion chamber while the piston is moving back from BDC to TDC, has high influence on the performance of the compressed air reciprocating engine. Therefore, the pressure measurement was conducted for the modified engine assembled the cylinder with side holes drilled to relieve the back pressure so as to verify an effect on the performance. In this investigation the same pressure measurement was conducted for the same engine assembled the camshaft of different cam profile, thus confirming an effect on the back pressure reduction to evaluate the performance of the compressed air reciprocating engine.
Sugita, Takayuki
Dynamic Analysis of a Valvetrain System2012-36-012610/2/2012
The mathematical modeling of the dynamics of a mechanical system is a powerful tool for the engineer predicts the behavior of the system. In the design of intake and exhaust valvetrains of diesel engine, the dynamic analysis of the system is essential for the proper sizing of the components. Through dynamic analysis of a 1D model using the Simulink software, this paper will describe the behavior of a valvetrain system that uses an exhaust rocker with hydraulic lifter.
Tomoyose, Rodrigo
Analysis of Ticking Noise from Cam Bearing of a Diesel Engine2012-01-16259/10/2012
Improving idle sound quality as well as reducing idle noise level is increasingly demanded for diesel engines. Therefore, unusual noise occurrence at idle is a serious problem, and the noise must be removed. This paper describes the characteristics and mechanism of ticking noise that is unusual noise radiated from the journal bearing of the camshaft at low idle speeds, based on the mechanism of cavitation in oil film existing between the journal and bearing.
Kimura, Jouji, Kasai, Ayumi, Saitoh, Shuji, Yamamoto, Atsushi, Takeshige, Naoya
Improvements in Fuel Efficiency through Improvements in Cord Reinforcements for Timing Belts2012-01-17509/10/2012
The overhead camshaft engine efficiency can be improved by control of the rotation and phase of the cam shaft rotation. The aim of this paper is to show the improvements that have been made to the cam shaft rotation through the improvements in the timing belt, and in particular the reinforcing cords within the timing belt. The current state of the art of timing belt reinforcement is presented, and an independent study of the fuel efficiency of a modern timing belt compared to the efficiency of a fully optimised gasoline engine with a timing chain. This considers the power losses due to friction as the timing belt (or chain) transmits power from crank to cam, the power losses expressed as vibrations and noise, the variations in speed of cam rotation for different designs of timing belt, and also consistency of cam rotation through the life of the timing belt (or chain). The improvements have been quantified from engine studies of engine efficiency, engine dynamics, engine friction measurements, accelerometer studies for NVH behaviour and from these the benefits in fuel economy and CO2 emissions were quantified. Novel systems that use a timing belt running within the engine immersed in oil are discussed. These have been adopted on two engines to date, with significant interest and development projects under way. Of concern to the motorist are not only fuel efficiency but also the cost and frequency of changing a timing belt. The historical mechanisms will be discussed of the changes in timing belts that control the belt durability. The improvements in reinforcing cord design and performance that contribute to life-of-engine belts will be presented, together with cord and belt developments that increase the durability and reliability of the timing belt even further.
Stevens, Chris A., Hayes, Craig H.
HCCI-Combustion in the Z Engine - Part II2012-01-15739/10/2012
The most common car engine is a 4-cylinder 4-stroke engine. The car manufacturers have a great pressure to lower the cost of the cars and this deal also with the engines. The challenges are the coming new emission norms (for example EURO-6) and also the customer acceptance, because of the fact that the car drives are used to the 4-cylinder engine and they want to have the same driving fun also from the new engines. A 2-cylinder 2-stroke engine has the same power output and torque as a 4-cylinder 4-stroke engine and thus it offers the same driving fun. Equal balancing is easy to make without some big additional costs, if the gas exchange of the engine is made by using poppet valves and camshafts. As there are only about 70% of the moving parts in the engine, its acceleration is even better than by a 4-cylinder engine. One of the latest developments in 2-stroke engines is the Z-engine, having the compression partially transferred outside of the working cylinders. This offers new thermo dynamical possibilities to adjust the working cycle and the combustion. As there are methods to control the temperature at TDC, a HCCI combustion is possible in the Z-engine at all loads. This lowers significantly the cost of the engine, as no urea injection, or NOx catalyst is needed to pass the coming EU-6 emission norm. The cost of the Z-engine is lower also because of the fact that it has only 2 working cylinders instead of 4. In 1999, Aumet Oy began to research this 2-stroke car diesel engine, called the Z-engine, in co-operation with the Internal Combustion Engine Laboratory at the Helsinki University of Technology (HUT) and the Energy Technology Department at the Lappeenranta University of Technology (LUT). So far, four master's theses, two SAE Papers and four Fisita Papers have been completed on the subject. Modern simulation tools, such as Star CD, GT-Power, Diesel RK and Chemkin have been used. The prototype engine made its first start in December 2004 and testing of the engine has been made two years in a testbench. In the HCCI combustion simulation of the Z-engine, a 4-dimensional ignition delay map, calculated with Chemkin and integrated in Diesel RK, has been used. The simulations and tests with the test engine show that the Z-engine has a very good efficiency, especially at part load. A HCCI combustion at all loads is possible in the Z-engine, with lambda about 1,8-2,3 and EGR-rate 10-40%, depending of the load. The TDC temperature at part load is about 800 K and at full load (BMEP 27 bar) about 700 K. The HCCI ignition, triggered with a pre chamber spark plug or small amount of fuel injection, occurs between 0°-20° ATDC and this limits the pressure and maximal temperature. No knock is present, as the ignition occurs always at the right side of the NTC (negative temperature coefficient) regime. NOx values are very low as the maximal temperature at full load is about 1900 K, because of the low starting temperature of the combustion, intern EGR and the expansion during the combustion. Intern EGR and active radicals stabilize the combustion and lower the activation energy needed for the ignition.
Janhunen, Timo T.
Dynamic Engine Control for HCCI Combustion2012-01-11334/16/2012
One of the factors preventing widespread use of Homogeneous Charge Compression Ignition or HCCI is the challenge of controlling the process under transient conditions. Current engine control technology does not have the ability to accurately control the individual cylinder states needed for consistent HCCI combustion. The material presented here is a new approach to engine control using a physics-based individual cylinder real time model to calculate the engine states and then controlling the engine with this state information. The model parameters and engine state information calculated within the engine controller can be used to calculate the required actuator positions so that the desired mass of air, fuel, and residual exhaust gas are achieved for each cylinder event. This approach offers a solution to the transient control problem that works with existing sensors and actuators. The initial goal of this project was to develop a physics-based approach to controlling engines with a cam-less or fully flexible valvetrain system. The model and control strategies that were developed can be applied to many internal combustion engine applications. The HCCI application in particular benefits the most from this technology because of the improved control of cylinder air mass and mixture composition. The real time one-dimensional flow model and the individual cylinder model developed during this project are explained. A single cylinder spark ignition research engine with cam-phasing and interchangeable camshafts was used for evaluating model parameter estimation and engine control performance. Test data is shown comparing estimated and measured pressures in the intake manifold and cylinder. The applicability of this control strategy to HCCI is discussed.
Lahti, John, Moskwa, John
Valve Profile Adaptation, Stratification, Boosting and 2-Stroke Strategies for Raising Loads of Gasoline HCCI Engines2012-01-11084/16/2012
The development of high efficiency powertrains is a key objective for car manufacturers. One approach for improving the efficiency of gasoline engines is based on homogeneous charge compression ignition, HCCI, which provides higher efficiency than conventional strategies. However, HCCI is only currently viable at relatively low loads, primarily because at high loads it involves rapid combustion that generates pressure oscillations in the cylinder (ringing), and partly because it gives rise to relatively high NOX emissions. This paper describes studies aimed at increasing the viability of HCCI combustion at higher loads by using fully flexible valve trains, direct injection with charge stratification (SCCI), and intake air boosting. These approaches were complemented by using EGR to control NOX emissions by stoichiometric operation, which enables the use of a three-way catalyst. Experiments were carried out using a single-cylinder engine of passenger car size running on gasoline and controlled with negative valve overlap. By adapting the valve profiles (lift, duration and phasing) for high loads, a fuel saving of 3% at constant load or a load increase of 6% could be achieved for lean HCCI compared to those obtained using camshafts that were not adapted for high load operation. Further, using intake pressures up to 180 kPa provided almost linear increases in load for lean HCCI, stoichiometric HCCI and stoichiometric SCCI. However, lean SCCI did not profit from boosting because the charge became too lean and stratification lost its effect as a ringing inhibitor. At intake pressures exceeding 140 kPa, stoichiometric HCCI operation becomes redundant since NOX ceases to be a limiting factor. Additionally, promising results were obtained in initial tests of two-stroke operation, which yielded higher maximum loads, lower fuel consumption and lower NOX emissions than the other strategies.
Dahl, Daniel, Denbratt, Ingemar
Recycling of Used Up Crankshaft Grinding Wheels2012-01-10604/16/2012
For sustainability in automobile manufacturing, recycle, reuse, and repair of used up cutting tools is now an established process. Although many types of tools were designed for one time use and then throw, an increasing awareness of the impact on the natural resources have made manufacturers to put some of these back to use or sell it back to suppliers who have put up a mechanism to extract the elements e.g. Tungsten and use it for manufacturing of new tools. There are many ways in which cutting tools can be recycled. Be it by reshaping a used up throwaway type tool [1], by redesigning of a tool holder for the use of unused cutting edges [2] or reusing short length drills that are used in making of long oil holes in crank case, cylinder head, cam shaft or connecting rods [3]. This paper demonstrates successful use of used up crankshaft grinding wheels. These used up grinding wheels can be reformed and used for grinding of many other automobile parts that require a new grinding wheel of size 600 mm to 750 mm on diameter depending on the machine on which grinding is being done. This has helped us in avoiding the purchase of new grinding wheels and has thus reduced our demand on natural resources.
Datar, Surendra
Comparison Between Journal and Rolling Element Bearings in a Camshaft Application2012-01-13244/16/2012
Concerns over greenhouse gas emissions are driving governments and the automotive industry to seek out ways of reducing vehicle CO₂ emissions. Engine friction reduction is one means of reducing CO₂ emissions, through fuel consumption improvements. One area where it is felt that friction reduction is possible is in connection with the camshaft bearings. The use of rolling element bearings is generally considered to provide friction reductions by two means: 1. As a direct substitution of the journal bearings by rolling element bearings and 2. As an enabling opportunity to reduce the oil flow requirement of the engine. MAHLE has undertaken a motored friction-testing program on a 2.5-liter gasoline engine, comparing the drive torques associated with the standard camshaft bearings and also with camshafts supported by rolling element bearings. The test engine incorporated a direct-acting valve train design. For manufacturing reasons, the camshaft supported in rolling element bearings incorporated sintered camshaft lobes whilst the standard engine employed a chill cast camshaft supported in conventional journal bearings. Contrary to previously reported results, the direct substitution tests demonstrated that the camshaft supported on journal bearings had a lower level of friction than the camshaft supported by rolling element bearings. The test engine configuration fitted with rolling element bearings showed a lack of sensitivity to variations in oil flowrates applied both to the rolling element bearings and also to the tappet/cam lobe interface This paper considers the approach to the testing, the test results obtained and some further discussion, including a possible basis for the results obtained.
Mackay, Stewart
Study on Reduction of Timing Chain Friction Using Multi-Body Dynamics2012-01-04124/16/2012
A method for reducing friction loss in the engine timing chain was investigated using multi-body dynamics simulation. The method known as the link-by-link model was employed in the simulation to enable representation of the behavior of each single link of the chain and its friction due to contact. In order to predict the friction under actual engine operating conditions, a model that takes camshaft torque fluctuation and crankshaft rotational speed fluctuation into account was created. This simulation was used to verify the detailed distribution of friction in each part of the chain system as well as the changes of friction in the time domain. As a result, it was found that the sliding friction in the chain tensioner guide and chain guide was larger than in other locations. Based on this result, a method of reducing friction entirely by measures in mechanisms and structures without relying on low-friction materials was investigated. Simulation was used to verify the predicted effects of these measures, with the result that reducing the moment of inertia of the camshaft and reducing the initial load on the chain tensioner were confirmed to reduce friction loss.
Sakaguchi, Motoyasu, Yamada, Shinji, Seki, Masao, Koiwa, Yojiro, Yamauchi, Takahiro, Wakabayashi, Tomohiro
An Efficient Multi-Body Approach Modeling Elastohydrodynamic Friction in Drive Systems2012-01-09174/16/2012
Chain drives are used in powertrains for the kinematic coupling of the cam shaft, the ancillary units and the balancing shafts with the crank shaft. Advantages of chain drives are their high load carrying capacity along with increased durability whilst simultaneously being maintenance-free. A crucial issue in the drive is the optimization in regard of friction, further improving efficiency, reducing exhaust emission and abrasive wear. Modeling friction in drive systems requires precise description of the whole system dynamics. High-frequency oscillations occurring in the chain strands cause numerical problems in the friction computation. As a remedy, regularized friction curves are often used, being however not able to correctly determine all friction configurations and requiring a tradeoff between accuracy and computational efficiency. Another challenge is the sensitivity of the coefficient of friction to many factors among which are kinematic and kinetic quantities, lubricant, material and surface properties. This contribution presents an approach for multi-body simulation of structure-variant chain drives, including bush, roller and silent chains. It describes the kinematic quantities of the bodies. Special focus is laid on modeling friction at its different points of origin. For the oscillation in the strands, a physically motivated elasto-plastic friction model is applied in the multi-body simulation and proven for its accuracy and computational efficiency. Also presented is an elastohydrodynamic model for computation of the friction coefficient, accounting for the before-mentioned factors. The presented approach was implemented in an in-house Fortran-based simulation tool. The paper reviews results of the friction simulation pointing out the efficiency of the approach.
Filippi, Markus, Ulbrich, Heinz
Design of an Electric Variable CAM Phaser Controller2012-01-04334/16/2012
As the emissions and fuel economy standards for internal combustion engines become ever more stringent, a variety of valvetrain control methods have been developed to improve engine performance. One of these is camshaft (CAM) phasing, which controls the angular position of the CAM relative to the crankshaft allowing changes to the timing of valve lift events. This method has demonstrated advantages including broadening the engine torque curve, increasing peak power at higher RPM, reducing hydrocarbon and NOx emissions, and improving fuel economy. In addition, external EGR systems can be eliminated because internal cylinder dilution control can be achieved by varying CAM timing. Current implementations of CAM phasing use oil-pressure-based electro-mechanical systems. While these systems are relatively low cost and have proven to be robust, they have disadvantages at low oil temperatures and pressures (such as during cranking events). To overcome performance issues of oil based systems, Delphi has created a CAM phasing system using a brushless DC (BLDC) motor to drive the phasing mechanism. This approach provides full control independent of oil conditions and demonstrates increased phasing authority. This paper will describe the electronics and algorithms required to control the three-phase BLDC motor which is part of the electric variable CAM phasing (eVCP) system. This controller takes desired CAM phase angle as an input, calculates the phase angle error, and closes the loop on the resultant motor current command. The electronics are packaged in a production-style case suitable for use in customer development applications. From a software perspective, this paper will discuss architecture considerations, including provisions for model-based rapid algorithm development and low-level motor control functions. Hardware component selection criteria and electromagnetic compatibility (EMC) design considerations will also be included. Finally, motor performance test data will be presented.
Cheever Jr, Gordon, Sullivan, Charles, Schten, Karl, Punater, Ash, Erickson, Clinton
A Friction Comparison between Chain and Belt-Drive Systems2012-01-04274/16/2012
Concerns over greenhouse gas emissions are driving governments and the automotive industry to seek out ways of reducing vehicle CO₂ emissions. Engine friction reduction is one means of reducing CO₂ emissions, through fuel consumption improvements. Of the different systems within the engine, the camshaft timing drive can contribute around 5 to 10% of the overall engine friction. It is therefore a system that can benefit from careful optimization. MAHLE has undertaken a motored friction-testing program on a 2.2-liter turbocharged diesel engine with the following different types of camshaft timing drive: - Chain drive with hydraulic tensioner. This is the standard configuration for this engine. - Chain drive with friction tensioner. - Wet belt drive. - Dry belt drive. Testing was conducted to allow the differences in friction between the different drive configurations to be calculated, by comparing each camshaft drive against the standard chain drive system. Using the frictional differences as a basis, the changes in fuel consumption from the standard configuration were predicted for a drive cycle. Changes in CO₂ emissions were then calculated. Experimental uncertainty levels were assessed during the analysis of the results. This paper considers the approach to the testing, the testing process and the test results.
Gagg, James
Optical Analysis and Measurement of Crankcase Lubricant Oil Atomisation2012-01-08824/16/2012
Crankcase emissions are a complex mixture of combustion products and, specifically Particulate Matter (PM) from lubricant oil. Crankcase emissions contribute substantially to the particle mass and particle number (PN) emitted from an internal combustion engine. Environmental legislation demands that the combustion and crankcase emissions are either combined to give a total measurement or the crankcase gases are re-circulated back into the engine, both strategies require particle filtration. There is a lack of understanding regarding the physical processes that generate crankcase emissions of lubricant oil, specifically how the bulk lubricant oil is atomised into droplets. In this paper the crankcase of a motored compression ignition engine, has been optically accessed to visualise the lubricant oil distribution. The oil distribution was analysed in detail using high speed laser diagnostics, at engine speeds up to 2000 rpm and oil temperatures of 90°C. High resolution calibrated images show the passive behavior of lubricant oil once it has been supplied to critical engine components. The major mechanisms of oil atomisation have been identified and quantified from high speed images, the generation of oil droplets dp = 10 μm - 3 mm has been captured. The most significant generation mechanism was atomisation of oil films present on the surface of rotating components. The isolated contribution of the crank and camshafts to the atomised oil droplets present in the top of the engine has been recorded. Further breakup, evaporation and condensation from the surface of the atomised oil droplets will generate coarse and fine PM. Results from imaging data show good correlation with sub-micron PN sampling measurements captured in a previous study [1]; namely an increase in particle number concentration with increasing engine speed.
Johnson, Benjamin T., Hargrave, Graham K., Reid, Benjamin A., Page, Vivian J., wagstaff, Stuart
HCCI-Combustion in the Z Engine2012-01-11324/16/2012
The most common car engine is a 4-cylinder 4-stroke engine. The car manufacturers have a great pressure to lower the cost of the cars and this deal also with the engines. The challenges are the coming new emission norms (for example EURO-6) and also the custom acceptance, because of the fact, that the car drives are used to the 4-cylinder engine and they want to have the same driving fun also from the new engines. A 2-cylinder 2-stroke engine has the same power output and torque as a 4-cylinder 4-stroke engine and thus it offers the same driving fun. Equal balancing is easy to make without some big additional costs, if the gas exchange of the engine is made by using poppet valves and camshafts. As there are only about 70% of the moving parts in the engine, its acceleration is even better than by a 4-cylinder engine. One of the latest development in 2-stroke engines is the Z-engine, having the compression partially transferred outside of the working cylinders. This offers new thermo dynamical possibilities to adjust the working cycle and the combustion. As there are methods to control the temperature at TDC, a HCCI-combustion is possible in the Z-engine at all loads. This lowers significantly the cost of the engine, as no urea injection, or NOx catalyst is needed to pass the coming EU-6 emission norm. The cost of the Z-engine is lower also because of the fact that it has only 2 working cylinders instead of 4. In 1999, Aumet Oy began to research this 2-stroke car diesel engine, called the Z-engine, in co-operation with the Internal Combustion Engine Laboratory at the Helsinki University of Technology (HUT) and the Energy Technology Department at the Lappeenranta University of Technology (LUT). So far, four master's theses, two SAE Papers and four Fisita Papers have been completed on the subject. Modern simulation tools, such as Star CD, GT-Power, Diesel RK and Chemkin have been used. The prototype engine made its first start in December 2004 and testing of the engine has been made two years in a testbench. In the HCCI combustion simulation of the Z-engine, a 4-dimensional ignition delay map, calculated with Chemkin and integrated in Diesel RK, has been used. The simulations and tests with the test engine show that the Z-engine has a very good efficiency, especially at part load. A HCCI combustion at all loads is possible in the Z-engine, with lambda about 1,8-2,3 and EGR-rate 10-40%, depending of the load. The TDC temperature at part load is about 800 K and at full load (bmep 27 bar) about 700 K. The HCCI ignition, triggered with a pre chamber spark plug or small amount of fuel injection, occurs between 0°- 20° ATDC and this limits the pressure and maximal temperature. No knock is present, as the ignition occurs always at the right side of the NTC (negative temperature coefficient) regime. NOx values are very low as the maximal temperature at full load is about 1900 K, because of the low starting temperature of the combustion, intern EGR and the expansion during the combustion. Intern EGR and active radicals stabilize the combustion and lower the activation energy needed for the ignition.
Janhunen, Timo T.
Modeling of Variable Valve Timing on High Performance Engine using Power-Oriented Graphs Method2011-24-01509/11/2011
Engine efficiency is one of the key aspects to reduce CO2 emissions. In order to improve the emission maintaining high performance capabilities several devices are introduced in the system; variable valve timing technology allows more flexibility for modern engines to meet peak performance, fuel economy and low emissions targets [7] while providing good driveability. This paper describes the Lamborghini continuously-variable cam phaser model using a graphical technique, called Power Oriented Graphs (POG), this uses an energetic approach for representing the physical systems. The generally accepted approach is to calibrate an engine on a dynamometer and to adjust the operation of the engine to meet performance targets. With the current build and test approach, these adjustments may not be made until well into the development program, and this calibration is a costly and time consuming step in the engine development process: the main purpose of this works is showing how was described the model in order to get more easy and fast the calibrating operations. Furthermore the usefulness to model the system consists of analyzing in simulation many more system configurations than those available for real experiments so it's important using a simple methodology that is able to analyze the whole system's dynamic in order to reach the performance expectations. The results obtained were validated demonstrating the effectiveness of the POG technique.
Corvino, Cristian, Calabretta, Michele, Zanasi, Roberto
Test Component SpecificationsJ1802/1_201105 (Historical)5/16/2011
This SAE Recommended Practice contains the reference information for SAE J1802.
Truck and Bus Foundation Brake Committee
Flexible Multi-body Dynamic Analysis of Multi-Cylinder Engine Valve Train2011-26-00861/19/2011
In this paper, valve spring parameters are optimized based on an iterative logic with constraint on space availability, stress limit, stiffness and natural frequency of the system. The optimized valve spring configuration is used in the push rod type valve train and the valve train dynamics for different engine speed is studied using commercially available multi-body dynamic ADMAS software. The valve train components such as cam, tappet, push rod, rocker arm, valve retainers and valve are modelled as rigid bodies and the valve springs (inner and outer valve springs) are modelled as flexible bodies. Each coil of the springs is modelled as separate flexible body and contact between these coils are established. A comparative valve train dynamics analysis is also carried out with the existing and optimized valve spring combinations. It is observed that valve jump engine speed with respect to optimized valve spring is enhanced to considerable amount when compared to the existing valve spring configuration.
Prabakar, R. S., Mangalaramanan, S. P.
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