If the compensating needle valve of a hydraulic governor is

On a diesel engine equipped with a hydraulic speed control governor, hunting in many cases can be corrected by adjusting the______.

A.accumulator spring compression

B.balance piston

C.compensating(补偿) needle valve

D.proportional piston

The major cause of trouble in a mechanical-hydraulic governor is contamination of the hydraulic fluid by ______.

A.dirt

B.fuel oil

C.governor cooling water

D.fuel oil tar(焦油)

If the compensating needle valve of a hydraulic governor is opened more than necessary the governor will .

A.have a larger than normal dead band

B.produce excessive speed response to a load change

C.respond slowly to any change in engine load

D.stabilize engine speed at the new governor setting

材料：

A typical example of a hydraulic governor is the Woodward. This has adjustable droop for parallel operation and it is fitted with a speed-adjusting control . If required it can be fitted with a synchronizing motor to provide remote control from a switchboard.

A gear pump driven from the engine supplies oil under pressure to accumulator pistons under which is a by-pass to regulate maximum pressure. One branch supplies oil which acts on top of the power piston, the pressure always tending to turn the terminal shaft to shut off fuel, while the other branch supplies oil to the pilot valve which is operated by the linkage from the fly weights above.

Should the speed of the engine decrease due to increased load the flyweights will move towards their center of rotation and lower the position of the pilot valve plunger, admitting oil pressure from the bottom of the power piston. Since, however, the area on the bottom is much greater than the top the net resultant force causes the piston to move upwards. This operates the power lever turning the terminal shaft which varies the cut-off point in the fuel pump through linkage, but as the power piston moves up, the actuating compensating piston moves down.

Oil under this piston is now forced through the needle valve to the receiving compensating piston, raising the outer end of the floating lever and the pilot valve plunger until it has returned to its normal position. This stops further movement of the terminal shaft so that the fuel control is now set in a position corresponding to the increased fuel required to run the engine at normal speed under the increased load.

问题：

This passage is mainly about ___.

A.what type of governor should be provided when the engine is used for electric power generation

B.why the speed of the engine fluctuates

C.how the governor works

D.how the fuel pumps work

The oil from the gear pump will ___. ① be supplied to the accumulator ② act on the power piston ③ be supplied to the pilot valveA.①

B.①②

C.②③

D.①②③

Which of the following is true about the Woodward discussed?A.It is a kind of mechanical governor.

B.It can not be used for parallel operation.

C.It has speed droop.

D.It may only be manually controlled from a switch boar

E.

When the speed of the engine decreases due to increased load, which of the following will NOT happen?A.The flyweights move towards their center

B.The pilot valve plunger moves towards its normal position

C.The power piston moves downwards until it returns to its normal position

D.The terminal shaft moves to a new position

请帮忙给出每个问题的正确答案和分析，谢谢！

A large change in ambient temperature, or using an oil of a viscosity different than the one recommended by the manufacturer in a mechanical hydraulic governor, will result in the need to adjust the

A.pilot valve opening

B.compensating needle valve

C.compensating spring tension

D.accumulator spring tension