F2008-06-123
Research of Test Methods of Waterīs Separating Efficiency for Fuel-Water Separation
The water in diesel fuel is the biggest destroyer of the modern dieselīs operating reliably. Its ill effect is: makes exact coupling parts in cemi-dry friction state, course the exact coupling parts to be worn and rusted intensively; dissolving salts into acid pollutant, it cause exact coupling parts and cylinder to be corroded; in the process of fuel injection, water would rapidly expand after being heated, it causes injector orifice to be deformed, with the result that fuel supply regulation is deteriorated, it causes the performance of the diesel to be reduced, and the automobile emission to be out of the standard. Therefore the fuel-water separating function is prerequisite to modern diesel fuel supply system.
Base on different operating principle, such as gravity sedimentation, inertial separation, centrifugal separation, or utilizing some special filter material with close to fuel and against to water characteristic, develop many types fuel-water separators for diesel. How to determine the waterīs separating efficiency of the those different fuel-water separators accurately is the problem which should be quickly resolved.
Authors adopt test procedures from the 6.5 item of ISO4020-2001, the 7.8 item of JIS D1617-1998, and SAE J1839-1997, the CD72 sedimentor was tested repeatedly. All the results of the test procedures are short of stability, repeatability and reproducibility.
We found the reasons are: 1. At the fuel-inlet side of the tested fuel-water separators, it is difficult to control the consistency of water dropīs dispersing on the fuel; 2. The precision of the flowmeter for minim water flow is too small, could hardly control the added water with 0.25% precisely; 3. The distribution of the small water drops, on the pipe section is misproportion, so it is difficult to get an exact sample.
After analysis and research, we study out a new test procedure: base on the method of the SAE J1839, improve the test equipment, and implement the test procedure strictly. Thus, control the equivalent diameter of the water drop on the fuel at 180～260 μm; Adopt the servo injector instead of microflowmeter; Adopt bulk sampling method instead small sampling method. After improving the test procedure, the CD72 sedimentor was tested altogether 10 times, the error of the results isnīt exceeding 0.89%. the stability, repeatability, and reproducibility are good enough.
Poster presentation: Future powertrain solutions