Operating Principles of CCEC Cummins Diesel Engines

As we know that Cummins is in the world’s largest company in designing, manufacturing, selling diesel engines and compressed natural gas engines. The most famous Cummins company in China is DCEC Cummins and CCEC Cummins (a Sino-American joint venture which founded in Oct, 1995, located in Chingqing city.).  As the engine industry's biggest foreign investor in China, Cummins own eight joint ventures and sole-funded manufacturing enterprises in China. Dongfeng Cummins produce B, C and L series diesel engines, and Chongqing Cummins mainly manufacture M, N and K series diesel engines.

In this article, we mainly talk about CCEC Cummins diesel engines operating principle.

NOTE: Dependable service can be expected from a Chong Qing-Cummins Diesel Engine when the operating procedures are based upon a clear understanding of the engine working principles. Each part of the engine affects the operation of every other working part and of the engine as a whole. Ching Qing-Cummins Diesel Engines treated in this manual are four-stroke-cycle, high-speed, full-diesel engines.

Chong Qing- Cummins (CCEC Cummins) diesel engines differ from spark ignited engines in a number of ways. Compression ratios are higher, the charge taken into combustion chamber during the intake stroke consists of air only with no fuel mixture. Cummins injectors receive low pressure fuel from the fuel pump and deliver it into individual combustion chambers at the proper time, in equal quantity and atomized condition for burning. Ignition of fuel is caused by heat of compressed air in the combustion chamber.

It is easier to understand the function of engine parts if it is known what happens in the combustion chamber during each of the four pistons strokes of the cycle. The four strokes and order in which they occur are: Intake Stroke, Compression Stroke, Power Stroke and Exhaust Stroke.

In order for the four strokes to function properly, valves and injectors must act in direct relation to each of the four strokes of the piston. The intake valves, exhaust valves and injectors are camshaft actuated, linked by tappets or cam followers, push rods, rocker levers and valve crossheads. The camshaft is gear driven by the cranshaft gear, thus rotation of the cranshaft directs the action of the camshaft which in turn controls the opening and closing sequence of the valves and the injection timing (fuel delivery).

Intake Stroke

During intake stroke, the piston travels downward; intake valves are open, and exhaust valves are closed. The downward travel of the piston allows air from the atmosphere to enter the cylinder. On turbocharged engines the intake manifold is pressurized as the turbocharger forces more air into the cylinder through the intake manifold. The intake charge consists of air only with no fuel mixture.

Compression Stroke

At the end of the intake stroke, intake valves close and piston starts upward on compression  stroke. The exhaust valves remain closed.

At the end of compression stroke, air in combustion chamber has been forced by piston to occupy a smaller space (depending upon engine model and one-fourteenth to one-sixteenth as great in volume) than it occupied at beginning of stroke. Thus, compression ratios is the direct proportion in the amount of air in the combustion chamber before and after being compressed.

Compressing air into a small space causes temperature of that air to rise to a point high enough for ignition of fuel.

During last part of compression stroke and early part of power stroke, a small metered charge of fuel is injected into combustion chamber.

Almost immediately after fuel charge is injected into combustion chamber, fuel is ignited by the existing hot compressed air.

Power Stroke

During the beginning of the power stroke, the piston is pushed downward by the burning and expanding gases; both intake and exhaust valves are closed. As more fuel is added and burns, gases get hotter and expand more to further force piston downward and thus adds driving force to crankshaft rotation.

Exhaust Stroke

During exhaust stroke, intake valves are closed, exhaust valves are open, and piston on upstroke.

Upward travel of piston forces burned gases out of combustion chamber through open exhaust valve ports and into the exhaust manifold.

Proper engine operation depends upon two things – first, compression for ignition; and second, that fuel be measured and injected into cylinders in proper quantity at proper time.

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