OCR Text |
Show The principle of measuring control is shown in Fig. 5. Where, the re I at ion with 0 (flow rate), N (burner flow rate character ist ic value) and P2 (burner inlet pressure) can be expressed in the following equation. In this case, burner is considered the fixed throttle. Q = NX(P2),2...(1) The relation with Q, P0 (valve inlet pressure) and P2 (burner inlet pressure) can be expressed in the following equation. In this case, adjustable value is considered the variable throttle. Q=VX(P0-PJJ"...(2) From (1) = (2), P2 can be expressed with P, N, V as follows. Q = {P/(1/V2 + 1/N2)}12... (3) Q can be determined by calculation. It is possible to know the current flow rate from the measured value of each sensor. At the same time, required control va I ve open i ng i s ca I cu I ated, and then the actuator i s contro I I ed to obta i n target f low rate. I n other words, stable f low rate control can be poss ible by the control valve opening-degree presetting system. Furthermore, the preset control system permitted forecast control based on open-close speed of flow control valve and, even in the course of flow rate variation, enabled to insure specific flow rate ratio of fuel to combustion air - so called - to realize high accuracy and high response of the cross limit function. In fact air and gas temperatures are measured at valve inlet and the flow rates are converted to standard state. Usua I ly va I ve i nlet pressure P0 is always secured at h i gh va I ue i r respect i ve of combust i on rate. So th i s revea I s that good accuracy could be achieved even by using low price sensors. This is one of outstanding features of this system. Introducing the multi-side diagnosis functions, the slave controller is provided with the self-diagnosis functions of control devices such as internal diagnosis of micro processor, decision of signal errors from sensors (pressure sensors, temperature sensors, valve opening degree sensors), detection of actuator faulty follow ability, etc. In addition, the slave controller is installed with functions to detect troubles of burner and flow control valve such as blocking and other failures. |