A piston assembly consists essentially of the piston crown, the skirt, a gudgeon pin and a number of...
piston rings. The crown is subject to the highest combustion pressure and thermal load. It may also suffer
from impingement by the combustion flame if the atomizer spray is defective. Piston crowns are of the
dished type to provide a combustion chamber between the piston crown and the cylinder head. To give the
desired combustion, the shape of the bowl formed in the crown depends on many factors, including the
choice of atomizer spray. The fiat rim of the piston surrounding the dished combustion chamber generally
contains cut-out sections to prevent the piston from hitting the inlet and exhaust valves. The piston crown is
generally made from high quality, deformation resistant forged steel and contains internal cooling surfaces
and the provision for a number of piston rings. The crown may taper slightly in order to allow for thermal
expansion while in service. During operation the upper part of the crown becomes hotter than the lower
part so it will expand more. Tapering allows a narrow clearance between piston and liner to be maintained.
参考解析:
1. In the elements of a piston assembly, who is subjected the highest thermal and combustion pressure load?
A. The piston crown.
B. The piston rings.
C. The gudgeon pin.
D. The piston skirt.
2. What type is the piston crown is designed to provide a combustion chamber?
A. Dish type.
B. Fork type.
C. Dished type.
D. Forked type.
3. What is the intention to cut-out the fiat rim of the piston?
A. For providing a larger combustion chamber.
B. For providing more heat transfer surface.
C. For saving the high quality material.
D. For preventing the piston from hitting the inlet and exhaust valves.
4. Why the crown may taper slightly?
A. The crown is difficult to make in cylinder.
B. The crown is not important part, so the requirement is not strict.
C. The slight taper can provide more expand space for the upper part of the piston.
D. The slight taper can provide more expand space for the lower part of the piston.