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).
Series of tests on a fuel injector, including modifications and analysis of performance.
| Identifier | ExFiles\Box 179b\3\ img208 | |
| Date | 1st February 1933 | |
| -18- SERIES 4. The big end failed and was replaced by a lead bronze bearing and at the same time a separate water supply was fitted to the injector jacket as it was thought that the improvement noted above in performance might be pushed still further by increasing the supply of water to the injector. A thermo couple was attached to the injector body to record the temperature on the surface at a point 2.600" above the nozzle tip. Greater clearance around the nozzle was also provided. Using Anglo Persian Airship Oil, a 2 hr. test (4a) was run and the results are shown in Fig.15. In the first hour the separate water supply to injector (see Fig.14) was shut off and the injector body temperature was 76°C. In the second hour the maximum amount of water was supplied to the valve jacket and the injector temperature reduced to 63°C. The power was but slightly affected, this change being 92.6 lbs/sq.in. and 91 lbs/sq.in. during the first and the second hour respectively. It is concluded, therefore, that the cooling of the injector with copper tube and two 1/2" holes in the walls to allow water circulation, is adequate and that there is no gain by increasing this rate of flow. In this particular test there was actually some falling off in power. This result is in agreement with test 2k (Fig.7) in which the jacket temperature was varied. Reducing the jacket temperature caused a slight falling off in power. A further test (4b) was now conducted on the cause of the needle valve discolouration. Laboratory examination showed that the hardness of the needle was not affected and that discolouration could be readily removed chemically. Moreover, heating the needle valve in fuel oil did not produce discolouration although this could be done by alternately heating it in oil and exposing it to air. It was therefore suggested that air might in some way be finding its way into the nozzle. This must either come in with the fuel supply or enter at some time after injection due to valve bounce. There appeared no evidence of air entering the fuel and hence a series of fuel line pressure diagrams were taken at the injector end. These diagrams are given in Figs. 16 to 19. Two were taken with a static injection setting of 1500 lbs/sq.in. and two at 3000 lbs/sq.in. and at each pressure one diagram was taken with the Bosch unloading delivery valve in the pump and one with a simple ball valve. These conditions were chosen as it was thought that if air was entering the injector from the cylinder the effects would be increased by these changes. | ||