Control fuel change

The soot formation and its control was studied in an annular diffusion flame using laser diagnostics and hot wire anemometry [17, 18]. Air and fuel were independently acoustically forced. The forcing altered the mean and turbulent flow field and introduced coherent vortices into the flow. This allowed complete control of fuel injection into the incipient vortex shedding process. The experiments showed that soot formation in the flame was controlled by changing the timing of fuel injection relative to air vortex roll-up. When fuel was injected into a fully developed vortex, islands of unmixed fuel inside the air-vortex core led to... 

Both diffusional flame calculations and detailed spatial mapping indicate that the nondispersed injection mode produces a vapor cloud that is characterized by diffusionally controlled combustion and bulk heating while subjecting the droplets to near isothermal conditions. The soot produced in this cloud is strongly influenced by bulk diffusion limitations and as such represents a bulk soot formation extreme. It was found that fuel changes had little effect on the overall soot yield due to this diffusion control. Lower gas temperatures and richer conditions were found to favor soot formation under bulk sooting conditions, probably due to a decrease in the oxidation rate of the soot. 

Thus, four-zone refueling permits attainment of 60 percent more bumup than simple batch refueling, with only 40 percent as much poison needed to control reactivity changes. The time between successive fuel replacements is only 40 percent as long in four-zone refueling as in batch, however. 

Many functions of an automobile are controlled electronically or with electromechanical-electrohydraulic controls. This change in vehicle design has made a wide variety of options available for people who require advanced vehicle controls. Many automobiles use electronic fuel injection. Electronic fuel injection systems convert the position of the accelerator pedal to a serial digital signal which is used by a microcontroller to inject the optimal fuel-air mixture into the automobile at the proper time during the piston stroke. The electronic signal for the accelerator position can be provided by another control device (e.g., joystick, slide-bar). 

Reactivity control for normal operations (bumup compensation and load following) is accomplished by six control rods which constitute two individual shutdown systems (3+3). Each system has its own trip parameters and can independently shutdown the reactor to the fuel changing temperature. 

Control rods are used primarily for power distribution shaping and for shim control of long-term reactivity changes, which occur as a result of fuel irradiation. The flow control function, which is used to follow rapid load changes, reduces requirements on speed of control rod response and thus improves plant safety. Every 2-3 months, the control rod patterns are altered to provide more uniform fuel and control rod burnup. In normal daily operation, little control rod movement is required for depletion of reactivity. The resulting low frequency of control rod changes reduces the possibility of operator error. 

The fuel-changing operation is based on the combined use of two remotely controlled fueling machines, one operating at each end of a fuel channel. Either machine can load or receive fuel. New fuel bundles, from one fueling machine, are inserted into a fuel channel in the same direction as the coolant flow—flow direction alternates between adjacent channels—and the displaced irradiated fuel bundles are received into the second fueling machine at the other end of the fuel channel. 

In this example fuel A is a gas over which we have no control. Fuel B is a liquid and its flow may be manipulated to control the heater outlet temperature. The scheme includes a bias feedforward scheme so that changes in fuel A are immediately compensated for by adjusting the flow of fuel B. For this to succeed we have to convert the units of measure of fuel A to be consistent with those of fuel B. By including the heating value of fuel B (NHVi,) in Equation (10.5) we get... 

With an in-cylinder oxygen concentration based fueling controller, the changes to the oxygen concentration caused by the air path actuator biases are correctly compensated. Based on the... 

Power output is controlled, not by adjusting the quantity of fuel/air mixture as in the case of induced spark ignition engines, but in changing the flow of diesel fuel introduced in a fixed volume of air. The work required to aspirate the air is therefore considerably reduced which contributes still more to improve the efficiency at low loads. 

---