Power system diesel generator room design

Rated power of generator set

The definition of the rated power of a generator varies with the mode of operation (reserve, constant load, and continuous basic power) and varies with temperature rise and insulation.

Installed, normally loaded and continuous basic power

The loading is suitable for most emergency / standby conditions, and the rated power is not allowed to overload. Therefore, in the design, overload capacity should consider more equipment costs, more operating costs and greater maintenance work.

Reserve power. When the city power is out of power, the standby power supply is provided, the power supply of the city power supply is reliable, and the operation of the 80% load is carried out. The running time is 200H per year. Some manufacturers are used for peak power compensation, with virtually no overload capacity.

Constant load power. For no city power supply situation, can be used continuously, 70% load operation, each 12h allows 10% overload 1H, the annual running time, load > 100%, do not allow more than 500h.

Continuous basic power. For a long time and electric bus in parallel or manufacturers and power plant basic load requirements, 100% basic rated power continuous operation (70% load), no overload capacity.

Temperature rise, insulation rating and rated carrying capacity of generator sets

The rated power of generator sets varies with the temperature rise and insulation level of the generator, and its nominal carrying capacity will also change.

Class H - 155oC, standby. 155oC refers to the ambient temperature 40oC basis, allowing temperature rise of 130oC, that is, the maximum winding temperature is 170oC.

Class F - 105oC, standby. 105oC means the temperature rise of 40oC is allowed on the basis of the ambient temperature 105oC.

Class B - 80oC, standby. 80oC means the temperature rise of 40oC is allowed on the basis of the ambient temperature 80oC.

At higher ambient temperature, the rated power of generator is attenuated, and the traditional insulation grade is H.

The temperature rise is defined as the extreme value of the winding temperature above the ambient temperature.

The insulation level of diesel generator set of Cummins electric power system is H, and the standby temperature rise is 125oC, which is usually 105oC.

Computer room cooling / ventilation system

The poor cooling / ventilation system of the engine room will affect the rated power of the generating set. The cooling system can limit the power output of the engine and release the heat which is converted to the effective power output through the coolant. The ventilation system can increase the temperature of the combustion air and reduce the cooling effect of the cooling system.

Cooling system of generator set

A generator is an electromechanical device that converts chemical energy (fuel) into electrical energy. The ventilation of the engine room should be balanced. Otherwise, the temperature will be higher and higher, and the pressure will be more and more big. Cooling water tank cooling system design should consider: maximum cooling temperature, expected operating temperature, power attenuation, expansion volume of coolant. In order to ensure the normal starting and loading of the minimum coolant temperature, monitoring / safety shutdown, the engine manufacturer data correctly and the radiator cooling fan / data correctly and operation parameters on the environment, body heat, heater, coolant flow rate.

Calculation of unit heat dissipation

It is assumed that diesel produces 140 000Btu/Gal of heat with a conversion efficiency of 35%. Fast fuel consumption estimation method:

Engine fuel consumption = using rated power (kW) * 0.07 (U.S.gal) = (kW) * 0.0185 (L) (1) type, using rated power (kW), first converted to

Btu.min-1= (kW) * (57) Btu.min-1

Usually, the engine is cooled by a liquid air heat exchange cooling system, which generates about 25% of the heat for fuel consumption (if required, please calculate it accurately). Liquid air heat exchange (radiator water tank) is the most common radiator.

Other rapid calculation of heat dissipation: exhaust system 30%, radiation heat 10%, power output 35%.

Ventilation system air calculation

The ventilation system provides engine combustion air, takes out the engine room heat, provides the generator cooling air, cools the engine (through the radiator water tank).

When air flows through the system, a greater temperature rise occurs. The design requirements of the cooling system of the generating set are actually measured and the manufacturer's data is for reference only. Poor design makes it difficult for generators to operate at full load in a high temperature environment.

Q=MCP (2)

Q emission heat

M fluid quality

The temperature change CP at constant temperature and pressure to allow room T

Air demand (CFM) = (58) (heat dissipation) / (Wen Sheng) (3) air demand (CFM) = (58) (B.min-1) / (Fo) (4)

Formula (3) and formula (4) should pay attention to unit unification.

Quick estimation. The effective ventilation area is approximately equal to the area of the radiator. The area of the effective air inlet is about 1.5 times the area of the radiator.

Exhaust return circulation system. In the low temperature environment, before the cold air enters the engine room, the exhaust air is allowed to flow back and the temperature of the unit is increased. Normally designed to be normally closed (to prevent the return of cold air outside the unit), the power supply is supplied by the generator set AC (AC) output or direct current (DC).

Summary of ventilation system. The ventilation system directly affects the rated power output and long-term safe and reliable operation of the generating set. Adequate intake and exhaust area, avoid short circuit of intake and exhaust air, straighten out air flow direction, exhaust air return area, straight in and out design room, other heat sources (i.e. no heat insulated smoke exhaust pipe and boiler).

Note that different engine requirements are different, and the 2 stroke requires more air.

Isolation and noise elimination in computer room

The generator swing needs complete isolation and prevents premature damage. The cables should be soft connected.

The main sources of noise are intake system, exhaust turbocharger, combustion noise, cooling fan and secondary vibration.

Noise generation

Noise