Power plants FG WILSON
Engine cooling
Some diesel engines are air-cooled, but most are cooled by circulating liquid refrigerant through the oil cooler, if fitted, and through the engine’s cylinder head cavities. The hot refrigerant leaves the engine, cools and passes back through the engine. Usually, cooling devices are either of the refrigerant-air type (radiator) or of the refrigerant-cold water type (heat exchanger).
In most installations of the general type, the refrigerant is cooled in a radiator installed on the generator unit, through the working chamber of which air is blown by means of a fan driven by the engine. In some cases, a remotely installed radiator is used, cooled by a fan with an electric motor. Where it is possible to use clean running cold water, a heat exchanger can be used instead of a radiator; in this case, the refrigerant circulates through the heat exchanger and is cooled by running water.
An important advantage of a cooling system with a radiator is its autonomy. If, as a result of a storm or any other factors, there is an interruption in the mains supply, this can also lead to interruptions in the water supply by disrupting the operation of the generator, which is cooled by flowing water.
Regardless of whether the radiator is installed on the generator set or remotely, it is necessary to provide access to the cooling system for its maintenance. For proper maintenance, the radiator filler cap, cooling system drain cocks, and fan belt tension adjuster must be readily accessible to the operator.
The radiator installed on the generator
The radiator mounted on the generator is installed in front of the engine on the frame (Fig. 9.1.) The fan driven by the engine drives air through the working chamber of the radiator, cooling the liquid refrigerant flowing through the radiator.
Radiators installed on the generator can be of two types. One is used with a cooling fan mounted on the engine. The fan is driven by a belt drive from the crankshaft pulley. The position of the fan bracket, fan spindle and drive pulley is adjusted relative to the crankshaft to provide the required belt tension. The fan blades go behind the radiator shroud, which has a gap to provide tilt when adjusting the belt tension.
Another type of generator-mounted radiator consists of the radiator itself, a fan, a drive pulley, and an adjustable idler pulley to adjust belt tension. The fan is mounted with a fixed center in the casing and minimal clearance to ensure high efficiency characteristics. The fan guide pulley, intermediate pulley and crankshaft pulley are precisely aligned and connected by belts in a three-point system. This second type of generator-mounted radiator typically uses an impeller fan with a close-mounted shroud.
The necessary radiator and fan combinations are supplied by F.G.Wilson and supplied with the generator set. Air flow parameters for cooling the F.G. generator. Wilson are listed in the table of technical characteristics. The air for cooling the radiator must be relatively clean to avoid clogging of the working chamber of the radiator. The necessary cleaning of the air entering the room should be carried out by a filter system. However, if the air in the installation area contains a high concentration of dust, fluff, sawdust or other materials, the use of a remote radiator located in a clean environment can solve the problem of clogging the radiator’s working chamber.
It is recommended that the air coming out of the radiator installed on the generator passes directly to the outside through the duct connecting the radiator to the opening in the outer wall. To reduce the length of the air duct, the engine should be located as close as possible to this wall. If the duct is too long, then a more economical solution would be to use a remote radiator. The resistance of the outgoing air flow and the inlet openings should not exceed the allowable static pressure of the fan.
When connecting the radiator installed on the generator, it is necessary to select an adapter for the exhaust duct. The length of the flexible duct (made of rubber or other suitable material) from the radiator to the stationary exhaust pipeline must ensure vibration isolation and freedom of movement between the generator unit and the stationary pipeline.
Figure 9.1. A radiator mounted on the generator to exhaust air through the outer wall
Portable radiator
A remote radiator with a fan driven by an electric motor can be installed in any convenient place at a distance from the generator set. (Fig. 9.2.) The design of the remote radiator has many useful features and advantages that provide great flexibility when installing the generator unit in houses. A more efficient venturi casing and fan provide a significant reduction in power consumption for engine cooling. The fan can be driven by a thermostat-controlled motor that draws power from the generator only when the motor is needed to cool. A remote radiator can be located outside the building, where there is little resistance to air flow and the ambient air temperature is usually lower than the air temperature in the generator room, resulting in greater efficiency with a smaller radiator size, and fan noise does not penetrate into the house.
Outboard radiators must be connected to the engine cooling system by means of a refrigerant line that includes flexible sections between the engine and the line.
Figure 9.2. An external radiator connected directly to the engine cooling system
Remote radiator/heat exchanger
Another type of system with an external radiator uses a heat exchanger. See figures 9.3 and 9.4. In this application, the heat exchanger acts as an intermediate link to isolate the engine coolant system from the high hydrostatic head of the radiator’s remote coolant. The engine pump circulates the refrigerant through the engine and heat exchanger.
A separate pump circulates the refrigerant between the external radiator and the heat exchanger tank.
Heat exchangers are also used to cool the engine without a radiator, as described in the next section.
Figure 9.3. Remote radiator isolated from the engine cooling system by means of a heat exchanger
Figure 9.4. A typical installation of a heat exchanger
Cooling using a heat exchanger
The heat exchanger can be used where there is a possibility of continuous supply of clean cold running water. In areas where excessive retention of foreign materials in the air can lead to permanent clogging of the radiator, for example, in places where there is sawdust in the air, it is logical to use cooling with the help of a heat exchanger. The heat exchanger cools the engine by transferring the heat of the engine coolant through the heat exchanger elements to the cold running water. Engine coolant and cooling water flow in separate, isolated systems, each with its own pump and never mix.
The heat exchanger completely replaces the radiator with a fan (Fig. 9.5). It is usually supplied as part of the generator set and installed on the engine, although it can be installed remotely. Since the motor is not used to drive the fan, there is no additional power consumption.
A suitable economical cold water supply is required for the circulating water circuit of the heat exchanger. To maintain the working conditions of the heat exchanger, soft water is required. For backup mode, it is preferable to use water from a well, lake or water tower, as opposed to water from the city water supply network, since the latter can work intermittently during power outages, making it impossible to use the generator.
Figure 9.5. Cooling system with a heat exchanger
Protection against freezing
If the engine is exposed to low temperatures, the cooling water must be protected from freezing. In the case of cooling with a radiator, you can add antifreeze to the water. For diesel engines, it is recommended to use antifreeze based on ethylene glycol. It contains a corrosion inhibitor that can be added later.
Only a colorless inhibitor should be used with ethylene glycol.
The content of ethylene glycol primarily depends on the degree of protection against freezing and the ambient temperature. The concentration of ethylene glycol should be at least 30% to achieve corrosion protection and not more than 67% to maintain adequate heat transfer.
For cooling with a heat exchanger, antifreeze does only half the job because it can only be used in the water circuit. It is necessary to ensure that the source of water does not freeze either.
Setting the required water composition
Regardless of whether the engine is cooled by a radiator or a heat exchanger, soft water must be used. The simplest and most economical way to soften water is to add an industrial softener. You can find out about the appropriate softeners from the distributor of F.G. WILSON. The manufacturer’s instructions must be strictly followed.