Question

When does relay’s 1 and 2 come into operation?

(a) When there are changes in steam pressure

(b) When there is change in forced draught

(c) When there is change in steam flow rate

(d) When there is change in induced draught

I have been asked this question by my college professor while I was bunking the class.

My query is from Principle of Automatic Control of Combustion topic in division Steam Power Plant of Energy Engineering

Answer 1

Correct answer is (d) When there is change in induced draught

For explanation I would say: When there are variation made in induced draught by air dampers opening due to coupling of motor that’s when relay 1 and 2 comes into operation. Relay 1 operates and adjusts the forced draught fan vanes till stability is restored in the combustion chamber. This result in an increased flow rate of air through the passage P. Due to increased flow rate, relay 2 is actuated which speeds up the stoker motor to supply extra fuel.