Design of integrated scanning laser Doppler velocitmeter using arrayed waveguide gratings

AbstractAn integrated scanned differential LDV has been proposed using planar lightwave circuit (PLC) technology. By using the proposed LDV, the measurement position can be scanned in depth direction without any mechanical movement. The PLC technology is utilized in the proposed design for achieving a compact optical circuit. The characteristics of the proposed LDV are simulated with a design model based on grating equations for AWGs. The simulation result reveals that the measurement position can be changed over the range of 46 mm in the depth direction without mechanical movement when the displacement between output sides of two waveguide arrays is 30 mm

LDA Flow Rate Measurements Applied for Analysis of Transient Injection Characteristics

In the present study an LDA-based technique was applied to analyze details of a transient pipe-flow induced upstream by a fuel ingector. Due to highly accurate measurements of the instantaneous time series of velocity, fuel flow rate and pressure gradient were achieved. The pipe flow has been driven under an injection pressure of 0.6MPa at high injection frequencies of 25 and 50 Hz. The influence of the outflow orifice diameter, varid in range from 100 to 500 μm, on the transient pipe flow dynamics has also been described. The results show that transient behavior of rapid oscillating pipe flow is remarkably and systematically dependent on injection frequency and duration as well as on the orifice diameter

Visualization and Measurements of Sub-Millisecond Transient Spray Dynamics Applicable to Direct Injection Gasoline Engine : Part 2:PDA Measurements and Analysis of Instantaneous Spray Patterns

A high-pressure swirl type spray has been experimentally analyzed by using a phase Doppler anemometer(PDA). The experiment was performed with an injection pressure of 5 MPa and an injection frequency of about 46 Hz. The PDA data was obtained in a two-dimensional plane and arranged with the injection phase angle. The arranged data of mean velocity, Sauter mean diameter, and droplet number density were visualized by using commercial software. In this paper, the data were compared with the results of visualization. It is indicated by the experiment that the large velocity and large size droplets initiated from the injector with small spray angle at the beginning of the valve opening duration. This stage was called core jet. In the next stage called quasi umbrella spray, the spray developed with large spray angle. After closing the valve, the spray remains increasing its velocity and diameter. This was caused by the "post injection". Using PDA, the detailed feature of the spray can be discussed with high temporal resolution

Measurement of Axial Flow Velocity in Cylinder of Reciprocating Engine by Single Incidence-Beam Reference-Mode LDA

In order to measure flow velocity in the swirl and radial directions of a cylinder of an engine in practical use by means of a laser Doppler anemometer(LDA)through a small measuring window on the cylinder head, a back scattering fringe mode LDA is used. This LDA, however, can not be used to measure the velocity component in the axial direction of the cylinder. A single incidence-beam reference-mode LDA is developed to measure the velocity component along the optical axis of the LDA and is applied to measure the fluctuating flow velocity in the axial direction of the cylinder. Ensemble-averaged mean velocity and fluctuation intensity of the velocity as measured using the LDA show good agreement with those measured using the conventional fringe-mode LDA. Based on these results, it can be concluded that the reference-mode LDA is applicable to measurements of the flow velocity in the axial direction of the cylinder through the amall window on the cylinder head

Visualization and Measurements of Sub-Millisecond Transient Spray Dynamics Applicable to Direct Injection Gasoline Engine : Part3:Measurements of Instantaneous and Integrated Flow Rates in High Pressure Injection System Using LDA-Based Meter

Time-dependent centerline velocity is measured using LDA-flow meter. Swirl injector at frequencies of 22 and 46 Hz generates oscillated flow under high-pressure from 4 up to 7 MPa. The encoded time-series of velocity is used to reconstruct the time-variable series of instantaneous flow rate and pressure gradient. Transient injection dynamics are analyzed to obtain basec characteristics of an injection system that will be able to be used for real time monitoring or active controlling of high-pressure gasoline injectors. The results obtained through analyzing the integrated mass rates within a cycle, indicate that a certain injection system is characterized by the flow rate constant γ which independent on injection duration and can be obtained from only accurate measurement of centerline velocity in the fuel transport pipeline. The present technique allows us to simplify the injection model and can be effectively adopted for practical employment on active and passive control with respect to gasoline direct injection engines