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    The mechanics of valve cooling in internal-combustion engines. Investigation into the effect of VSI on the heat flow from valves towards the cooling jacket.

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    Yahia-Abdel-Fattah-PhD-Thesis.pdf (10.85Mb)
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    Publication date
    2010-06-14T14:41:12Z
    Author
    Abdel-Fattah, Yahia
    Supervisor
    Rosala, George F.
    Wright, Steve
    Keyword
    Engine valve cooling
    Thermal interfaces
    Valve / seat thermal conductance
    Seat / cylinder head thermal conductance
    Heat flow analysis
    Finite Element
    Exhaust valves
    Internal-combustion engine
    Institution
    University of Bradford
    Department
    School of Engineering Design and Technology
    Awarded
    2009
    
    Metadata
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    Abstract
    Controlling the temperature of the exhaust valves is paramount for proper functioning of engines and for the long lifespan of valve train components. The majority of the heat outflow from the valve takes place along the valve-seat-cylinder head-coolant thermal path which is significantly influenced by the thermal contact resistance (TCR) present at the valve/seat and seat/head interfaces. A test rig facility and experimental procedure were successfully developed to assess the effect of the valve/seat and seat/head interfaces on heat outflow from the valve, in particular the effects of the valve/seat interface geometry, seat insert assembly method, i.e. press or shrink fit, and seat insert metallic coating on the operating temperature of the valve. The results of tests have shown that the degree of the valve-seat geometric conformity is more significant than the thermal conductivity of the insert: for low conforming assemblies, the mean valve head temperature recorded during tests on copper-infiltrated insert seats was higher than that recorded during tests on noninfiltrated seats of higher conformance. The effect of the insert-cylinder head assembly method, i.e. shrink-fitted versus press-fitted inserts, has proved negligible: results have shown insignificant valve head temperature variations, for both tin-coated and uncoated inserts. On the other hand, coating the seat inserts with a layer of tin (20-22¿m) reduced the mean valve head temperature by approximately 15°C as measured during tests on uncoated seats. The analysis of the valve/seat and seat/head interfaces has indicated that the surface asperities of the softer metal in contact would undergo plastic deformation. Suitable thermal contact conductance (TCC) models, available in the public domain, were used to evaluate the conductance for the valve/seat and seat/cylinder head interfaces. Finally, a FE thermal model of the test rig has been developed with a view to assess the quality of the calculated TCC values for the valve/seat and seat/head interfaces. The results of the thermal analysis have shown that predicted temperatures at chosen control points agree with those measured during tests on thermometric seats with an acceptable level of accuracy, proving the effectiveness of the used TCC models.
    URI
    http://hdl.handle.net/10454/4333
    Type
    Thesis
    Qualification name
    PhD
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