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TECHNICAL PAPERS

# Experimental and Numerical Investigation on the Effects of the Seeding Properties on LDA Measurements

[+] Author and Article Information
Angelo Algieri1

Dipartimento di Meccanica, Università della Calabria - 87036 Arcavacata di Rende (CS)

Sergio Bova2

Dipartimento di Meccanica, Università della Calabria - 87036 Arcavacata di Rende (CS)

Carmine De Bartolo3

Dipartimento di Meccanica, Università della Calabria - 87036 Arcavacata di Rende (CS)

The axial velocity is positive if directed toward the trumpet entrance; the radial velocity is positive if directed toward the trumpet axis.

1

a.algieri@unical.it

2

s.bova@unical.it

3

c.debartolo@unical.it

J. Fluids Eng 127(3), 514-522 (Mar 01, 2005) (9 pages) doi:10.1115/1.1899167 History: Received November 25, 2003; Revised December 06, 2004; Accepted March 01, 2005

## Abstract

The characteristics of the seeding particles, which are necessary to implement the laser Doppler anemometry (LDA) technique, may significantly influence measurement accuracy. LDA data were taken on a steady-flow rig, at the entrance of the trumpet of the intake system of a high-performance engine head. Five sets of measurements were carried out using different seeding particles: samples of micro-balloons sieved to give three different size ranges ($25–63μm,90–200μm$, and standard as received from the manufacturer $1–200μm$), smoke from a “home-made” sawdust burner (particle size $⩽1μm$), and fog from a commercial device (particle size around $1μm$). The LDA data were compared with the results of two-phase computational fluid dynamics simulations. The comparison showed a very good agreement between the experimental and numerical results and confirmed that LDA measurements with particle dimensions in the order of $1μm$ or less represent the actual gas velocity. On the contrary, quite large particles, which are often used because of their cost and cleanliness advantages, introduce non-negligible errors.

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## Figures

Figure 1

Scheme of the steady-flow test rig: (1) blower, (2) engine head, (3) cylinder, (4) bypass valve for flow regulation, (5) flow meter, and (6) differential manometer.

Figure 4

Size distribution of the fog droplets, as provided by the manufacturer

Figure 5

Measurement location at the entrance of the intake trumpet. (a) Location of the measuring points along the trumpet axis (b). Location of the measuring points along lines orthogonal to the trumpet axis. (c) Experimental setup.

Figure 6

Axis-symmetric geometric model

Figure 7

LDA measurements taken using micro-balloons and smoke

Figure 8

Comparison of the LDA data and CFD simulation results (trumpet axis)

Figure 9

Comparison of the LDA data and CFD simulation results (radial direction).

Figure 10

Effect of the sieving procedure

Figure 11

Absolute and relative differences in the axial component of the velocity along the trumpet axis between micro-balloons (LDA measurements) and air (model)

Figure 12

Comparison of the LDA data (smoke and fog) and CFD results (air) along the trumpet axis

Figure 13

Comparison of the velocity distributions by using smoke and fog particles

Figure 14

Axial velocities comparison by using fog and smaller micro-balloons

Figure 15

Radial velocities comparison by using fog and smaller micro-balloons

Figure 16

Axial pressure gradient as a function of the velocity difference between the continuous and discrete phase along the trumpet axis

Figure 17

Percentage velocity differences as function of the axial pressure gradient (25 and 63μm particles)

Figure 2

Microscope photograph of micro-balloons

Figure 3

Cumulative distribution and logarithmic density of micro-balloons

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