Investigation on Measurement of Diesel Spray Breakup Length by Using Doppler Signals 2001-01-0533
New measuring methods of diesel spray characteristics were investigated by using laser Doppler signals, when diesel spray was injected into a high pressure vessel at room temperature(Injection under the high pressure means the simulation of injection atmosphere of diesel engine). We describe two methods of breakup length measurement, and these have great advantage compared with the conventional method using spray photographs.
First, spray tip penetration was measured by the delay time of Doppler signals from injection start to spray tip arrival at each measuring point (measuring volume of Laser Doppler Velocimeter (LDV)), traversing the measuring point along the spray axis center line or offset line of the center line from nozzle hole towards downstream. Spray breakup length was measured as the inflection point of the curve drawing the delay time of Doppler signals versus the measuring points. Each measured data of diesel spray was compared with the data estimated from spray photographs. Finally, we found that the result of this method is well agreeing with the conventional one.
Second, we found that spray breakup length was estimated by measuring standard deviation of the delay time of Doppler signals which indicated spray tip arrival time, because spray tip arrival time was of uneven after spray was broken up. This measuring method about breakup length was also verified to be adequate.
Moreover, while concerning the residual spray at downstream of the breakup length, we found that spray droplets number density and spray droplets number flux could be estimated by measuring the data-rate of Doppler signals.