Diesel Generator Handbook
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the RIC engine may have its cylinders arranged in one of several ways. In the context of generating plants, the most commonly used engines are those in which the cylinder axes are either perpendicular (vertical) and in-line; or are arranged in a vee-form.
The general definition of the single bank, or in-line engine, is one 'having a number of working cylinders all located on one side of the crankshaft, and in which all the cylinder centre lines lie in one and the same plane, which usually contains the crankshaft' (BS5673:1979/ISO 1205-1972). This form of construction may be used for engines of up to 9 cylinders.
The opposed-piston engine described in Section 1.4 would be classified as an in-line engine. The cooler (or wet-type tower) of Figure 1.13(d)uses evaporative cooling. Its coils, which form a water-to-water heat exchanger for the engine's closed circuit, have a large surface area. Evaporation of the secondary cooling water is then achieved by either producing water droplets (by spray), or by forming thin films.
A motor driven fan pulls the air through the top of the tower, or forces it from the bottom. The draught so created removes the evaporated water molecules. Because there will be roughly 2 % loss of water through evaporation, make-up facilities must be provided. Special precautions are necessary in order to reduce the risk of
legionellae (Legionnaires' disease). See Sub-section 15.4.4 of Chapter 15.
Since most modern medium and high-speed engines are designed for high temperature coolant conditions, they employ pressurized closed circuit cooling systems. System pressures may vary from O.3-O.7kg/cm2 • These equate to water boiling points at sea level of 107°Cand 115°C, respectively. Engine makers would then design for corresponding operating temperatures at engine outlet of 80°C and 90°C.
Whatever the system, it is always advisable to use a high rate of jacket circulation, with a small temperature difference between engine inlet and outlet, rather than a slow circulation and a large temperature rise.
Since most modern medium and high-speed engines are designed for high temperature coolant conditions, they employ pressurized closed circuit cooling systems. System pressures may vary from O.3-O.7kg/cm2 • These equate to water boiling points at sea level of 107°Cand 115°C, respectively. Engine makers would then design for corresponding operating temperatures at engine outlet of 80°C and 90°C.
Whatever the system, it is always advisable to use a high rate of jacket circulation, with a small temperature difference between engine inlet and outlet, rather than a slow circulation and a large temperature rise.
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