Page:Investigation of the discharge rate of a fuel-injection system.djvu/3

 3 N.A.O.A. Technical Note No. 373 The rate of fuel injection continued to increase for 7 de- grees after the pump "by-pass valve opened. Calculations show that this interval is required for the pressure wave in the fuel to travel from the by-pass valve to the injection nozzle. Introduction The interpretation of indicator cards taken from compres- sion-ignition engines is difficult because of the variation in the weight and heat contents of the mixture during the engine cycle due to the injection of the fuel. The interpretation requires, among other things, a knowledge not only of the time of start and cut-off of the fuel spray, but also of the rate of fuel injection. De Juhasz (Reference 1) developed an apparatus for deter- mining the rate of fuel discharge using a constant-pressure injection system. He utilized a stationary receiver located opposite a cam-aotuated injection valve. Between the receiver and the valve was a rotating disk with a slot. By means of this apparatus De Juhasz obtained some valuable results on the angular rate of fuel discharge. He found that by increasing the oil pressure the period of injeotion was increased and that the maximum rate occurs earlier in the period; and that the rate of discharge was more uniform at higher camshaft speed and with smaller orifices.