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).
Analysis of fuel injection systems, comparing pump types and discussing the physics of injection phenomena like pressure waves.
| Identifier | ExFiles\Box 179b\3\ img105 | |
| Date | 1st February 1933 | |
| -15- He/Td.6/ATR.2.33 contd. So far, observations have been confined almost entirely to the R.R. combined pump and injector and the sharpness of the beginning of injection (except with 6 of the suction chamber holes unplugged) has been a marked feature. With a Bosch pump and injector and a fuel line, 1.6 mm. bore and 24 inches long, preliminary observations have shown that the beginning of injection is not so clearly defined. The end of injection with the R.R. pump at maximum injection is also less distinct than at normal injection. This is probably due to spill port opening at normal injection while the plunger is moving with a uniform velocity whereas at maximum injection the spill port is never open and the injection ends by virtue of the plunger coming to rest. The oscilloscope clearly shows any inequality in the sprays issuing from the various holes and also phenomena such as valve bounce and discontinuous injection. The occurrences of these have already been noted at maximum injection. DISCUSSION OF THE FOREGOING TESTS. In the present state of knowledge it is not possible to give a full explanation of all the occurrences in the injection system but the following brief sketch may indicate the type of action that goes on and throw some light on the factors governing the three fundamental quantities, injection quantity, injection period and pump lag. Consider first the simplest possible form of injection system consisting of a fuel pipe having at one end a differential type injector and at the other a plunger of the same bore as the pipe. Now let the plunger move with a uniform velocity V.{VIENNA} If the fuel was incompressible it would be equivalent to a rigid inelastic bar and the effect of the plunger motion would be instantaneously felt at the injector and it would immediately open. Actually, owing to the compressibility of the fuel the immediate effect of the plunger motion is to compress the fuel just in front of the plunger, setting up a pressure wave which travels through the fuel until it reaches the injector. If the wave is not of sufficient amplitude to lift the needle it is totally reflected at the fuel pipe, is reflected at the plunger and again returns to the injector. If it is now of sufficient magnitude to lift the injector needle, injection commences and the wave is partially reflected, returns to the plunger and is reflected again. As this process continues the | ||