REVIEW ON CRITICAL SPEED IMPROVEMENT IN SINGLE CYLINDER ENGINE VALVE TRAIN

Novateur Publication’s
International Journal of Innovation in Engineering, Research and Technology [IJIERT]
ICITDCEME’15 Conference Proceedings
ISSN No - 2394-3696
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REVIEW ON CRITICAL SPEED IMPROVEMENT IN SINGLE CYLINDER
ENGINE VALVE TRAIN
Sagar Gade
Department of Mechanical Engineering, Pravara Rural Engineering College , Loni, Savitribai Phule Pune University, India
R. R. Kharde
Department of Mechanical Engineering, Pravara Rural Engineering College , Loni, Savitribai Phule Pune University, India
Jagrit Shrivas
Sr. Manager-R & D, Greaves Cotton Limited, Aurangabad
ABSTRACT
The purpose of valve train is to operate the inlet and outlet valves of the engine. The valve train mainly consists of rocker
arm, push rod, cam, poppet valve and spring for keep the valves closed position. The Greaves G400WG engine valve train is
operated at the maximum speed of 3600 rpm. The main objective of this project is to improve the valve train speed up to safe
speed limit that is up to 5000 rpm.
The valve spring parameters are optimized based on space availability, stress limit, stiffness, buckling of pushrod 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. 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. Design improvements include detail study on following topics:
1. Valve Spring Stiffness.
2. Push rod buckling.
3. Valve closing Velocity.
4. Contact stress between cam and follower
KEYWORDS: Valve train, Computer Aided Engineering, ADAMS, Stiffness, Buckling, Valves, Valve Spring, Push rod, Valve
Cam shaft.
INTRODUCTION
The function of the valve train mechanism is to use the intake and exhaust valves to control in a timely way the entry of
charge and the exit of the exhaust gas in each cylinder following each cycle of engine operation. The valves must respond quickly
to the valve train and they must seal against the combustion pressures and temperatures. The poppet type of valve has a low
lubrication requirement, low friction, simplified sealing, easy adjustment, and low cost. Therefore, it has been the most commonly
used valve in four-stroke engines.
The valve train system should be optimally designed so as to avoid an abnormal valve movement, such as valve jumping
or bounce up to the maximum engine speed. In earlier valve train systems, valve lash used to be set manually during initial
installation and readjusted at regular maintenance intervals by means of adjusting screws and shims. When the engine is in
motion, the dynamic forces like normal reaction forces, frictional forces, Impact forces on the timing chain may cause
considerable effect on the function of the valve train & hence on valve. The effect is prominent when the engine is at high speed.
In this project work, the dynamic analysis of valve train system insights on design and optimization of the speed of opening and
closing of valves.
Fig Valvetrain schematic and nomenclature
OBJECTIVE OF WORK

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• To improve the speed of engine valve train without any failure of contact between cam tappet and cam.
LITERATURE REVIEW
After the study of SAE paper it is found that there is Andrew J G Whitehead (1) proposed the best method to improve the
critical speed of engine valve train. The valve spring parameters are varied 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 kinematic and dynamic properties are analyzed by using ADAMS software.
METHODOLOGY
The existing valve train of engine is center pivot OHV type of valve train, a flat face or roller hydraulic lifter can be used
as a cam follower. It is a single cylinder engine with rated output range from 7-7.7 kw at 3600 rpm for CNG, LPG, and Gasoline.
The maximum torque obtained should be 23-27 Nm at 2700 rpm. The dimensions of engine are 86 x 68 x 395 mm. The
orientations of crank shaft horizontal, with liquid cooling of engine. The maximum operating speed of valve operation is 3600
rpm.
The Royal Enfield engine is considered as the bench mark for the contact stresses. The maximum value of contact
stresses between cam and roller tappet should not exceed 1200 Mpa. The engine valve train operation speed i.e. the speed of cam
shaft shall be improved from 3600 rpm to 5000 rpm without failure of pushrod, rocker arm, valve, and the contact stresses should
be less.
By referring Phil Carden(1)
paper to improve the valve train speed i.e. speed of cam shaft. The speed is changed by
adjusting the valve spring stiffness, the current valve spring stiffness is 23.05 N/mm2
at 3600 rpm. According to the valve spring
stiffness the forces comes to 7.8 mm valve lift on the pushrod, cam, cam tappet, rocker arm, valve etc. should be calculated
analytically and by using ADAM software speed should be calculated on different values of the spring stiffness.
The contact stresses between the cam and roller follower having cylindrical to cylindrical contact present, the pushrod
and rocker arm having sphere to sphere contact present, and the rocker arm and valve head having sphere to sphere contact, the
contact stresses should be calculated by using Hertz contact stresses theory. The force required to lift valve upto 7.8 mm it
depends upon the stiffness value of the spring. The force come on the pushrod should be calculated by using rocker ratio. The
pushrod buckling should be checked for different spring stiffness values. To find the natural frequency of the valve train the
overall valve train stiffness and effective mass of the system. The effective mass of system should be depends upon the mass of
valve, spring, retainer, pushrod, rocker arm, and tappet. The overall stiffness depends upon the stiffness of cam/ tappet, pushrod,
rocker arm, and cylinder head pedestal fulcrum. After completing the analytical calculations the cross verification of the forces,
pressure, stresses, deflection and speed should be checked by using software solution.(2-10)
EXPERIMENTAL VALIDATION
The experimental validation of finalized spring and other valve train components is done by replacing the old
components with the modified parts. The validation includes effect on emission, valve train speed and the rated output of engine
should be studied.
RESULT AND DISCUSSION
Flexible multi-body engine valve train dynamic analysis is carried out to predict engine speed at which the valve train
components lose their contacts and optimized the valve spring design. In order to capture the dynamic behavior of the valve train
system closely, each coil of the nested valve springs is modeled as separate flexible body and the contacts between coils of these
flexible bodies are also established. A comparative valve train dynamics analysis is also carried out with the existing and
optimized valve spring combinations. The comparative study reveals that the proposed optimized valve spring configuration
works properly even beyond the engine speed of 5000 rpm where the valve train component separation will be observed in case of
existing valve spring combination.
ACKNOWLEDGEMENT
The Author would like to express sincere thanks all the members who are directly or indirectly part of this work
REFERENCES
1) Heath, A.R., "Valve train design for multivalve automotive gasoline engines", SAE 885133, 1988
2) Yushu Wang, "Engine Valve Train Design", SAE International.
3) Saeid M. Baniasad, Michael R. Emes, “Design and Development of Method of Valve-T rain Friction Measurement”,
SAE International, 23-26 February 1998, paper no. 980572.
4) Robert L. Norton, Ronald L. Stene, James Westbrook III, David Eovaldi, “Analyzing Vibrations in an IC Engine Valve
Train”, SAE International, 23-26 February 1998, paper no. 980570.
5) Evandro de Almeida Leme, Alfons R. Wagner, Anderson Gutierres, Gilson Santos, Henrico Gouvea da Silva, “Friction
Torque Measurement and Analysis of Influence Factors on Engine Valve train”, SAE International, 30 October 2014,
paper no. 2014-36 0286.
6) Thiago Teixeira de Paula Pignatti, Roberto Esteves da Cunha, Wilson Miziara, “Reduced Friction for a Four Cylinder
Two Valve Otto Engine Valve Train”, SAE International, 4-6 October 2011, paper no. 2011-36-0208.

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7) Dumitru M. Beloiu, “Modeling and Analysis of Valve Train, Part I -Conventional Systems”, SAE International, 04
December 2010, paper no. 2010-01-1198.
8) Robert Huber, Peter Klumpp, Heinz Ulbrich, “Dynamic Analysis of the Audi Valve lift System”, SAE International, 04
December 2010, paper no. 2010-01-1195.
9) Tao (Tom) Xu, Chungyao (Alex)Tang, Huihua (Harry) Shen, Michael King and Mark Nowak, Qianfan (Harry) Xin,
“Modeling, Validation and Dynamic Analysis of Diesel Pushrod Overhead Bridged Valve Train”, 16-19 April 2007,
paper no. 2007-01-1256.
10) Kushwaha H, Rahnejat H and Jin Z M, “Valve-Train Dynamics: a Simplified Tribo-Elasto-Multi-Body Analysis”, Proc.
Instn. Mech Engrs Part K, 214, 95-110, 2000

REVIEW ON CRITICAL SPEED IMPROVEMENT IN SINGLE CYLINDER ENGINE VALVE TRAIN

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REVIEW ON CRITICAL SPEED IMPROVEMENT IN SINGLE CYLINDER ENGINE VALVE TRAIN