The document summarizes research into wear of automotive engine valves and seats. Two test rigs were developed to simulate valve wear: a bench test rig and a motorized cylinder head rig. Tests showed wear results from both the impact of valve closure and sliding under combustion pressure. Wear increases with higher closing velocity, combustion load, and valve misalignment. Lubrication reduced wear significantly. A model was created to predict valve recession based on these factors.

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RESEARCH PROJECT
Wear of Automotive Engine Valves and Seats
Tom Slatter, University of Sheffield
Maik Broda, Ford Motor Company
Dr Roger Lewis, University of Sheffield
Dr Rob Dwyer-Joyce, University of Sheffield
The drive for reduced emissions from diesel exhausts has led to a reduction in the
amount of oil present in the air stream in automotive diesel engines. This, in turn,
has led to an increase in the wear of inlet valves and seat inserts in diesel engines.
Three types of valve/seat insert failure occur in internal combustion engines. These
are valve recession, guttering and torching. The most prevalent failure mechanism
in diesel engines is valve recession. This is caused by material removal from the
valve and/or the seat insert.
Two test-rigs have been developed (bench test-rig and motorised
cylinder-head) that are capable of providing a valid simulation of the
wear of both inlet valves and seat inserts used in automotive diesel
engines. The bench test-rig, designed to be mounted in a hydraulic test
machine, is able to simulate both combustion loading and impact of the
valve on the seat on valve closure. It is not possible, however, to vary the
closing velocity significantly. The motorised cylinder-head can be used
to investigate impact wear of valve and seats over a range of closing
velocities. Test methodologies developed for the bench test-rig have
isolated the effects of impact and sliding.
Investigations have shown that the valve and seat insert wear problem involves two distinct mechanisms; impact of the valve on
the seat insert on valve closure and sliding of the valve on the seat insert under the action of the combustion pressure. Both have a
large influence on valve recession. It is in combination, however, that they have the largest effect. In tests run on the bench test-rig
using impact and sliding in combination it took a few thousand cycles to achieve wear attained in several hundred thousand cycles
in the frictional sliding tests.
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2. Resultados Google para Imagen http://www.shef.ac.uk/mecheng/tribology/research/projects/images/VALVES.JPG
The pictures illustrate; a series of ridges and valleys on a valve seating face
formed by a deformation/gouging process as a result of impact on valve closure;
radial indentations on an insert seating face caused by the valve sliding against
the insert under the effect of combustion loading and surface cracking and
subsequent material loss on an insert seating face as a result of impact on valve
closure.
Radial Indentations on a
Seat Insert Seating Face
Ridges and Valleys on a Surface Cracking on a
Valve Seating Face Seat Insert Seating Face
Wear has been shown to increase with valve closing velocity, combustion load and misalignment of the valve relative to the seat
insert. Lubrication of the valve/seat interface reduced valve recession, on the material combination tested, by a factor of ten.
A semi-empirical wear model for predicting valve recession
has been developed based on the fundamental mechanisms of
wear determined during test work. Model predictions were
compared with engine tests as shown in the graph to the right.
The model can be used to give a quantitative prediction of the
valve recession to be expected with a particular material pair or
a qualitative assessment of how parameters need to be altered
in order to reduce recession.
Software called RECESS has been developed to run the semi-
empirical valve recession model.
Flow charts have also been developed, based on the review of literature, failure analysis and modelling carried out, to assist in
diagnosing and rectifying valve/seat failures and to help in reducing valve recession by design.
Sponsor
We are grateful to Ford Forschungszentrum Aachen GmbH for sponsorship of this work.
Publications
1. Slatter, T., Lewis, R., 2006, “Valve Recession - The Importance of Impact Wear”, Proceedings of the IMechE Conference on
Tribology 2006: Surface Engineering & Tribology for Future Engines & Drivelines.
2. Slatter, T., Lewis, R., Dwyer-Joyce, R.S., 2006, “Valve Recession Modelling”, SAE Paper 2006-01-0365.
3. Lewis, R., Dwyer-Joyce, R.S., Slatter, T.J., Brooks, A.C., 2004, “Valve Recession: From Experiment to Predictive Model”,
Proceedings of the VDI Conference on Ventriltrieb und Zylinderkopf, pp79-93. (ISBN 3 18 091813 6)
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3. Resultados Google para Imagen http://www.shef.ac.uk/mecheng/tribology/research/projects/images/VALVES.JPG
4. Lewis, R., Dwyer-Joyce, R.S., 2002, quot;Design Tools for Predicting Inlet Valve Recession and Solving Valve Failure Problemsquot;,
Journal of Engines, Transactions of the SAE 2001, pp105-114. (ISBN 0 7680 1099 3)
5. Lewis, R., Dwyer-Joyce, R.S., 2002, quot;Wear of Diesel Engine Inlet Valves and Seat Insertsquot;, Journal of Automobile
Engineering, Proceedings of the IMechE Part D., Vol. 216, pp205-216.
6. Lewis, R., Dwyer-Joyce, R.S., 2001, Automotive Engine Valve Recession, Engineering Research Series No. 8, Professional
Engineering Publishing Ltd., London. (ISBN 1 86058 358 X)
7. Lewis, R., Dwyer-Joyce, R.S., 2001, quot;Design Tools for Predicting Inlet Valve Recession and Solving Valve Failure Problemsquot;,
SAE Paper 2001-01-1987, in SP-1624, pp105-114. (ISBN 0 7680 0788 7)
8. Lewis, R., Dwyer-Joyce, R. S., and Josey, G., 2001, quot;An Experimental Approach to Solving Valve and Seat Wear Problemsquot;,
Proceedings of the 27th Leeds-Lyon Symposium on Tribology, Elsevier Tribology Series No. 39, pp629-640. (ISBN 0 444
50581 4)
9. Lewis, R., Dwyer-Joyce, R.S., Josey, G., 2000, quot;Investigation of Wear Mechanisms Occurring in Passenger Car Diesel Engine
Inlet Valves and Seat Insertsquot;, Journal of Fuels and Lubricants, Transactions of the SAE 1999, pp610-618. (ISBN 0 7680
0695 3)
10. Lewis, R., (2000), quot;Wear of Diesel Engine Inlet Valves and Seatsquot;, University of Sheffield PhD Thesis.
11. Lewis, R., Dwyer-Joyce, R. S., and Josey, G., 1999, quot;Investigation of Wear Mechanisms Occurring in Passenger Car Diesel
Engine Inlet Valves and Seat Insertsquot;, SAE Paper 1999-01-1216. (ISSN 0148 7191)
12. Lewis, R., Dwyer-Joyce, R.S., Josey, G., 1998, quot;Design and Development of a Bench Test-Rig for Investigating Diesel Engine
Inlet Valve and Seat Insert Wearquot;, Proceedings of the 5th International Tribology Conference in Australia, Institution of
Engineers, Australia, pp365-370. (ISBN 1 86445 001 0).
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