1995年世界上l5～60岁人口数约为同期发达地区人口的（）。

A.less fuel will enter the cylinder

B.higher the cylinder combustion temperature

C.more complete the fuel combustion

D.more rapid the rise in combustion pressure

A.less fuel will enter the cylinder

B.lower will be cylinder compression temperatures

C.more complete will be fuel combustion

D.more rapid will be the rise in combustion pressure

n the cylinder has more air than is needed for complete combustion. Lean combustion reduces peak temperatures and therefore NOx emissions. Efficiency is increased and higher output is reached while avoiding knocking. Combustion of the lean air-fuel mixture is initiated by injecting a small amount of LFO (pilot fuel) into the cylinder. The pilot fuel is ignited in a conventional diesel process, providing a high-energy ignition source for the main engine. To obtain the best efficiency and lowest emissions, every cylinder is individually controlled to ensure operation at the correct air-fuel ratio and with the correct amount and timing of pilot fuel rejection. Wartsila has developed a special electronic control system to cope with the demanding task of controlling the combustion in each cylinder, and to ensure optimal performance in terms of efficiency and emissions under all conditions by keeping each cylinder within the operating window. Stable and well-controlled combustion also contributes to less mechanical and thermal load on the engine components. Current stringent emission regulations demand the reduction of NOx emissions. In an internal combustion engine this means controlling peak temperature and residence time, which are the main parameters governing NOx formations. In the Wartsila 50DF engine, the air-fuel ratio is very high (typically 2.2). Since the same specific heat quantity released by combustion is used to heat up a larger mass of air, the maximum temperature and consequently NOx formation are lower. The mixture is uniform. throughout the cylinder since the fuel and air are premixed before introduction into the cylinders, which helps to avoid local NOx formation points within the cylinder. Benefiting from this unique feature, NOx emissions from the Wartsila 50DF are extremely and comply with the most stringent existing legislation.

What is the combustion feature of the Wartsila 50DF？

A.Lean air in the cylinder

B.Excessive fuel in the cylinder

C.Excessive air in the cylinder

D.Spark ignition

The term diesel engine scavenging means_____________.

A.delivering more air into the cylinder than it would normally receive during an ordinary charging process

B.forcing the products of combustion out of the cylinder with the fresh air charge

C.collecting the air charge at the cleaner

D.combustion and expansion of hot gas

Which statement about diesel engine combustion is true？

A.Combustion does not begin until the piston starts down on the power stroke

B.Maximum combustion pressure is reached before TDC

C.Turbulence in the cylinder causes a delay in ignition

D.Maximum cylinder firing pressure is not developed until the piston passes TDC

The cylinder head, cylinder liner and () form. the combustion chamber.

A.frame

B.crankcase

C.piston

Air scavenging of a diesel engine cylinder__________.

A.blows out the exhaust gases

B.supplies oxygen for combustion

C.cools the valves and cylinder walls

D.all of the above

The cylinder head, cylinder liner and _____ form. the combustion chamber.

A.frame.

B.piston

C.crankcase

D.explosion plate

ll enter into the cylinder _____ and the gases exhaust _____, there being an adequate overlap between the inlet opening and the exhaust closing.

A.downwards/upwards

B.upwards/downwards

C.downwards/downwards

D.upwards/upwards