This article is intended to be a guide to address engine room ventilation considerations that apply to the successful installation, operation, and maintenance of diesel engines, generator sets, compressor units, and other such packaged units.
The primary aspects of a properly designed engine room ventilation system are cooling air and combustion air. Cooling air refers to the flow of air that removes radiant heat from the engine, generator, and other engine room components. Combustion air describes the air that the engine requires to burn fuel.
Cooling and combustion air directly impact engine and package unit performance and dependable service life; these must be considered in the design of an engine room ventilation system. It is also important to consider all engine room equipment in the design of a ventilation system and provide a comfortable environment for service personnel to perform maintenance.
VENTILATION FANS
Except for special applications, natural ventilation is too bulky for practical consideration. Adequate quantities of fresh air are best supplied by powered ventilation systems. The selection of fan type is usually determined by ventilation air volume and space requirements in the engine room. Ideal engine room ventilation systems will utilize both supply and exhaust fans. (See Figure 1).
Fan sizing involves much more than just selecting a fan that will deliver the airflow volume needed to meet the cooling air and combustion air requirements. It requires an engineering understanding of fan performance characteristics and ventilation system design parameters. Exhaust air systems should maintain a slight positive pressure. This prevents ingress of dust and dirt, which can harm the equipment in the room.
COOLING AIR
A portion of fuel consumed by an engine is lost to the environment in the form of heat radiated to the surrounding air. In addition, heat from generator inefficiencies and exhaust piping can easily equal engine radiated heat. Any resulting elevated temperatures in the engine room may adversely affect maintenance, personnel, switchgear, and engine or generator set performance. Engine room ventilation air (cooling air) has two basic purposes.
- To provide an environment that permits the machinery and equipment to function properly with dependable service life.
- To provide an environment in which personnel can work comfortably and effectively.
It is important to note that cooling air is needed for more than just the engine; the generator intake also requires cool, clean air. The most effective way to do this is to provide a ventilation air source low to the ground at the rear of the engine package.
The use of insulation on exhaust pipes, silencers, and jacket water pipes will reduce the amount of heat radiated by auxiliary sources. Radiated heat from engines and other machinery in the engine room is absorbed by engine room surfaces. The remaining radiated heat must be carried away by the ventilation system. Table 1 gives data on the heat losses of exhaust pipes.
In many cases combustion air is drawn from the outside separately; this air has little impact on the engine room ventilation. Maximum engine room temperatures should not exceed 120 degrees F. Proper ventilation is heavily dependent on the path of the ventilation air. Proper design should carefully look at the entire room equipment layout as to maximize the ventilation effectiveness.
This article was written by Norm Grusnick Engineer | Product Development, ECCO Manufacturing
