From the Rolls-Royce experimental archive: a quarter of a million communications from Rolls-Royce, 1906 to 1960's. Documents from the Sir Henry Royce Memorial Foundation (SHRMF).
Page from a report detailing the calculations for determining the static injection period.
| Identifier | ExFiles\Box 179b\3\ img109 | |
| Date | 1st February 1933 | |
| He/M 4.6/AR.2.33 contd. -19- APPENDIX. DETERMINATION OF THE STATIC INJECTION PERIOD. The Discharge-Control position curves have all been plotted to a base of notches on the control wheel. It is now required to convert this to a base of static injection periods. Since at maximum injection the delivery stroke ends 47°, measured on pump cam, after suction port seals, the static injection period at maximum injection is 47°. Since the angle of the helical relief port is 45° we have that for any plunger lift w the arc moved through by a point on the surface of the plunger when following the helix, is also w measured horizontally. Since the plunger diameter is 10 mm. the angular rotation of the plunger for any lift w cms. is (57.3 / .5) * w degrees The angular movement of the plunger for one revolution of the control wheel = 28.125 degrees. There are 12 notches on the wheel. Since the effective stroke at maximum injection is 7 mm, we find from the above relations that the number of notches corresponding to 7 mm. stroke is ((57.3 / .5) * .7 / 28.125) * 12 = 34.2 Hence at notch 34.2 the static injection period is zero. For 29.5° (pump) after the sealing of the suction ports the plunger displacement is directly proportional to the pump angle i.e. plunger displacement-pump angle curve is a straight line. 1° of rotation of pump corresponds to 0.202 mm. lift. ∴ 1° of rotation of cam corresponds to ((57.3 / .5) * .0202 / 28.125) * 12 = 0.987 notches. ∴ Straight line portion of cam corresponds to 29.5 x .987 = 29.1 notches. Hence end of straight line portion of cam corresponds to 34.2 - 29.1 = 5.1 notches from maximum injection position. Between 0 and 5.1 notches the scale is not uniform owing to cam form but from 5.1 to 34.2 notches it is uniform. The scale is set out on Fig.6. from which the static injection period for any injection quantity can be read. For normal injection quantity (0.235 ccs/cycle) this is seen to be approximately 19°. He/Od. | ||