Example combustion engine control

Notwithstanding the intellectual challenges posed by the subject, the main impetus behind the development of computational models for turbulent reacting flows has been the increasing awareness of the impact of such flows on the environment. For example, incomplete combustion of hydrocarbons in internal combustion engines is a major source of air pollution. Likewise, in the chemical process and pharmaceutical industries, inadequate control of product yields and selectivities can produce a host of undesirable byproducts. Even if such byproducts could all be successfully separated out and treated so that they are not released into the environment, the economic cost of doing so is often prohibitive. Hence, there is an ever-increasing incentive to improve industrial processes and devices in order for them to remain competitive in the marketplace. 

In many processes (such as oil recovery, blood flow, underground water), one encounters liquid flow through thin (micrometer diameter), noncircular-shaped tubes, or pores. In the literature, one finds studies that address these latter systems. In another context of liquid drop formation, for example, in an inkjet nozzle, this technique falls under a class of scientifically challenging technology. The inkjet printer demands such quality that this branch of drop-on-demand technology is much in the realm of industrial research. All combustion engines are controlled by oil drop formation and evaporation characteristics. The important role of capillary forces is obvious in such systems. 

A good example is the control of the Space Shuttle engines, where each of the three engines generates 200,000 kgf (400,000 lbf) lifting force and each weighs 3,200 kg (7,000 lb). These engines can operate at extreme temperatures as the LH2 fuel is at -253°C (-423°F), and when burned, its combustion temperature reaches 3,300°C (6,000°F). Yet, the controls used are not that sophisticated at all. 

Often we want a reaction to take place rapidly enough to be practical but not so rapidly as to be dangerous. The controlled burning of fuel in an internal combustion engine is an example of such a process. On the other hand, we want some undesirable reactions, such as the spoiling of food, to take place more slowly. 

By this standard bus bars are summarized in an airplane. Consumers of the cabin are, for example, less important than the cockpit devices. Of utmost importance is of coiu e the flight cmitrol. Even at a total failure all internal combustion engines, such as the main engines and the auxiliary power unit (APU), during flight at maximum cruise height the controllability of the aircraft and safe landing at an alternative airport must be ensured. 

Some controlled explosions are very useful. For example, explosions occur inside cylinders of internal combustion engines. Blasting materials are common to certain mining, tunneling, and quarrying activities. 

This air/fuel mixture ratio can be and is exploited in the control of internal combustion engines. For example, cars fitted with catalytic converters can operate with adjustable air/fuel ratio X, which allows the air/ fuel mixture to be optimized during the running of the engine, thus minimizing CO and hydrocarbon emissions. On the other hand, one should note that nitrogen oxides are not directly related to the air/fiiel mixture ratio, and thus cannot be controlled in this way. 

In the chemical engineering domain, neural nets have been appHed to a variety of problems. Examples include diagnosis (66,67), process modeling (68,69), process control (70,71), and data interpretation (72,73). Industrial appHcation areas include distillation column operation (74), fluidized-bed combustion (75), petroleum refining (76), and composites manufacture (77). 

We have previously encountered examples of chemical autocatalysis, where the reaction accelerates chemically such as in enzyme-promoted fermentation reactions, which we modeled as A + B 2B because the reaction generates the enzyme after we added yeast to initiate the process. The other example was the chain branching reaction such as H. -I-O2 —> OH - -0 just described in hydrogen oxidation. The enzyme reaction example was nearly isothermal, but combustion processes are both chain branching and autothermal, and therefore they combine chemical and thermal autocatalysis, a tricky combination to maintain under control and of which chemical engineers should always be wary. 

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