85.In some modern large diesel engines, which of the followingis used as the support for the main bearings?
86.Turbulence in the cylinder of a two-stroke/cycle main propulsion diesel engine is mainly created by _____________.
A.directional intake valve ports
B.masked intake valves
D.intake port design
87.In an internal combustion engine, which of the devices listed will force the compression rings to seal the compression gases in the space above the piston?
A.Use of bimetallic piston rings
B.Ring gap pretensioning
C.Thermal increase in ring-end clearance
D.Gas pressure acting against the back of the ring
88.The theoretical minimum compression ratio necessary to ensure compression ignition in a direct injection diesel engine is _____________.
89.The size of the exhaust valve opening is ____________.
A.most critical in a four-stroke/cycle diesel engine
B.most critical in a two-stroke/cycle diesel engine
C.most critical in a four-stroke/cycle diesel engine if it is turbocharged
D.of equal importance in a two-stroke/cycle diesel engine as in a four-stroke/cycle diesel engine
90.Provision is to be made for ventilation of an enclosed diesel engine crankcase by means of a small ________.
A.aperture not exceeding 25mm diameter
B.fan to develop a slight suction not exceeding 25mm of water
C.vent line attached to the upper most area of the crankcase near the center of the engine
D.breather or by means of a slight suction not exceeding 25mm of water
91.Which of the general advantages listed does the electrical pyrometer have over the mechanical pyrometer?
A.When heated, it will move proportional to the amount the metal has lengthened or expanded.
B.The pointer associated with the pyrometer scale can be made to also measure engine RPM
C.It can be utilized in exhaust manifolds and heat exchangers interchangeably.
D.It can indicate temperature at a distant point from the source of heat.
92.In a large slow-speed propulsion diesel engine, the force applied to the crosshead is ______________.
A.against the crosshead during power stroke and away from the crosshead during the compression stroke
B.against the crosshead during the compression stroke and away from the crosshead during the power stroke
C.against the crosshead during the power and compression strokes
D.away from the crosshead during the power and compression strokes