Übersicht der VVT-Systementwicklung bei Hilite. Overview of VVT System development at Hilite

Transcription

1 Übersicht der VVT-Systementwicklung bei Hilite Overview of VVT System development at Hilite M.Sc. Mustafa Mohammed Simulation Engineer Business Unit Engine / Simulation Frei verwendbar

2 Contents Company profile Product portfolio Variable valve timing (VVT) and its requirements Simulations in Hilite product development process VVT simulations using Simcenter Amesim 2

3 Company Profile Hilite International is a global supplier for the automotive industry since 1930 with the focus on the development and production of systems and components to improve fuel consumption and reduce emissions. With its headquarters in Marktheidenfeld, Bavaria, Germany, the company has approx employees at eight locations in Europe, North America and Asia. 3

4 Product Portfolio Hilite International product portfolio is broadly divided into two groups Engine Application and Transmission Application Engine Application Transmission Application VVT (Variable Valve Timing) System 4

5 VVT and its requirements VVT is used to shift the cam shaft angle in advance or retard direction with respect to crank angle. Some of the requirements from VVT are: Higher phasing speed or shifting speed of cam phaser Good controllability Fast unlocking and locking of cam phaser Lower VVT leakages Higher oil flow through oil control valve Balanced hydraulic forces in oil control valve Lower oil consumption from engine lubrication system Robust performance Weight, cost, etc. 5

6 Simulations in Hilite product development process Being engine in development phase, it is difficult to measure the performance of a system on different boundary conditions with hardware. A need develops here to understand the engine behavior virtually on different possible boundary conditions and define the VVT concept suitable for particular engine in very initial stages of development. Hilite uses various simulation techniques and tools to analyze all the possible physics involved in VVT system. Simulation department at Hilite consist of 17 engineers and is broadly classified into different groups (see below). Simulation Design/Idea Structural mechanics Tests/Measurements Electromagnetic Fluid dynamics Multi physics system simulation 6

7 VVT simulation using Simcenter Amesim VVT apart from its own parameters also depends on different engine parameters. A multi physical system simulation tool is needed to analyze the functional performance of individual VVT components and whole system. Hilite uses AMESim for this task. Internal parameters influencing VVT performance Phaser size, Oil control valve flow and forces, leakages, friction, etc. VVT System (Cam phaser + Oil control valve) Engine lubrication system Camshaft torque Oil pump Engine speed Hydraulic Mechanical External parameters influencing VVT performance 7

8 VVT simulation using Amesim Oil control valve modelling Oil control valve is the most important system, which connects the engine lubrication system with cam phaser and which control the direction of phasing. Oil control valve 3D model With the help of Amesim, it is possible to build a detailed model of oil control valve by implementing the inputs from CFD software as well as developing customized submodels, where needed. Oil control valve AMESim model (partly shown) 8

9 Oil flow rate in L/min Oil control valve displacement in mm VVT simulation using Amesim Oil control valve validation To improve the performance of oil control valve, first it is very important to predict correctly the hydraulic flow rate and forces acting on oil control valve by complete operating range. Pictures below shows an example of measured and simulated oil flow rate through OCV and hydraulic forces acting on OCV at its complete operating range or displacement. The Amesim curves are in good correlation with measured curves. Measured AMESim Oil control valve displacement in mm Force required to displace the oil control valve in N 9

10 Oil flow rate in L/min Oil flow rate in L/min VVT simulation using Amesim Oil control valve parameter analysis Hilite apart from specialized DOE tools, also uses Amesim DOE tool to analyze the limits of its systems. Picture in the right shows a Amesim DOE tolerance analysis and measurements done with two different parts of same design. Both measured curves differ from each other due to difference in tolerances. Measured curves lie in between simulated curves (between min. and max. tolerances). Measurement - 1 Measurement -2 AMESim DOE (all colored lines) Design optimization will be carried out in Amesim and accurate dimension will be given as feedback to design and test teams. Picture in the right shows an improvement in maximum oil flow rate compared to the original system. Oil control valve displacement in mm Original design Improved design Oil control valve displacement in mm 10

11 VVT simulation using Amesim Engine lubrication VVT system is hydraulically connected to engine lubrication system. Any change in lubrication system will influence the VVT performance. In static conditions, it is enough to consider the pressure drop in oil gallery and can be modelled simple. In dynamic conditions, it is important to consider the oil inertia, oil pump time constant, etc. apart from pressure drop to predict the correct performance of VVT. This is why there is a need of simulating the oil path from oil pump to cam phaser. Engine lubrication system in AMESim 11

12 VVT simulation using Amesim Engine lubrication Hilite uses CFD methods to make sure the validity of Amesim models. Below table shows a comparison of oil flow rates in lubrication system between CFD and AMESim. 0W30 Oil temperature in C Flow rate at intake VVT inlet from engine lubrication system in L/min Flow rate at exhaust VVT inlet from engine lubrication system In L/min CFD AMESim Difference [%] CFD AMESim Difference [%] Customer satisfaction is a top priority for Hilite. Apart from improving VVT performance, on customers request Hilite also takes efforts to analyze the engine lubrication flow path and give improvement suggestions that can help in increasing VVT performance. A table at right shows an example where pressure drop in lubrication system is reduced. Original lubrication system Oil temperature in C Total oil flow rate in L/min Total oil pressure drop in bar rel Modification Modification

13 Cam shaft torque in Nm Cam shaft torque in Nm VVT simulation using Amesim Valve train Valve train model in Amesim Cam shaft torque Cam shaft speed Cylinder 1 Cylinder 2 Cylinder 3 Cam shaft torque at 1000 rpm Multi-body simulation AMESim simulation Cam shaft torque at 6000 rpm VVT is hydraulically connected to lubrication system and mechanically to cam shaft. Engine oil pressure and cam shaft torques are two most important parameters which drives the VVT. Hilite also simulates valvetrain along with VVT system, to have continuous physical exchange of parameters between them. Cam shaft angle in Cam shaft angle in 13

14 Phasing speed in Crank angle/s VVT simulation using Amesim Cam phasing speed or shifting speed Phasing speed or shifting speed is the speed with which cam phaser phases to achieve the target angle. To estimate correct phasing speeds, all the internal and external influencing parameters of VVT have to be rightly modelled. Amesim gives the possibility to create once own submodels, with which it is possible to consider the physics in as detail as required. Thanks to a very detailed modelling, it is possible to achieve the phasing speeds similar to measurements. + Towards retard direction Measured AMESim Towards advance direction - Engine speed in 1/min 14

15 VVT simulation using Amesim Cam phaser unlocking and locking Cam phaser should get locked at one fixed position, if there is less than required pressure in the system. Figure in below left shows a wear caused by lock pin during phaser locking and unlocking. Figure in right shows the Amesim animation, which helps to understand the pin behavior during unlocking, phasing and locking. Wear Lock pin Ring 15

16 Phaser angle in cam angle VVT simulation using Amesim Cam phaser parameter analysis example The figure on right, shows the influence of one of the phaser damping design on phaser angle with Without damping With 1 cam angle damping With 3 cam angle damping Target angle respect to time. Damping helps the rotor to come in contact with its stator with reduced velocity, transferring less force to the stator. As seen in the figure, more the damping, more the Time in s time phaser will take to reach the target angle. More damping is good from structure point of view Rotor Stator but not from functional point of view. These kind of simulations helps to have better understanding of the system. 16

17 Thank you very much for your kind attention!