NASA Technical Memorandum 102581

TiC14 as a Source of TiO 2 Particles for Laser

Anemometry Measurements in Hot Gas

Donald H. Weikle, Richard G. Seasholtz,

and Lawrence G. Oberle

Lewis Research Center

Cleveland, Ohio .....

April 1990

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TiCl 4 AS A SOURCE OF TiO_ PARTICLES FOR LASER RNEMOMETRY

MEASUREMENTS IN HOT GAS

Donald H. Weikle, Richard G. Seasholtz, and Lawrence G. Oberle

National Aeronautics and Space Administration

Lewis Research Center

Cleveland, Ohio 44135

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SUMMARY

A method of reacting TiC14 with water saturated gaseous nitrogen (GN2) at

the entrance into a high-temperature gas flow is described. The TiO 2 particles

formed are then entrained in the gas flow and used as seed particles for making

laser anemometry (LA) measurements of the flow velocity distribution in the hot

gas. Scanning electron microscope photographs of the TiO 2 particles are shown.

Data rate of the LA processor was measured to determine the amount of TiO 2

formed. The TiCI 4 and mixing gas flow diagram is shown. This work was performed in an open jet burner at NASA Lewis Research Center.

INTRODUCTION

The reaction of TiCI 4 with water in GN2 to form TiO 2 was investigated as

a method to generate seed particles for high-temperature gas flow in turbine

hot section LA measurement applications. This reaction is a simple low cost

method to generate large numbers of small TiO 2 particles. TiCI 4 reacts with

water in air as shown.

TiCl 4 + 2H20-*TiO2 + 4HCl

As shown in the reaction equation there is a 4 to 1 ratio of HCI to TiO 2

formed. The total amount is small, however, because small amounts of TiCl 4 are

used. The HCf could be neutralized, such as with ammonia or sodium bicarbonate as shown.

NH3 + HCI*NH4C1 (ammonia chloride salt)

or

NaHCO 3 + HCI÷NaCI + H20 + CO2

Other reactions are also possible.

neutralize the HCf.

In this experiment we did not attempt to

The general method of particle generation we used was similar to that

used by R.R. Craig et al. (ref. 1) to form TiO 2 for ambient temperature LA

applications. We used GN2 as a carrier gas and mixed the TiCI 4 gas and water

saturated GN2 at the entrance into the hot gas stream.

The experiment was part of a general investigation of various seed particles that would be suitable for high-temperature applications. Dry TiO 2 and

Al203 (1 pin in diam) have been selected as satisfactory but not ideal for
our application. The dry particles were injected into the combustion chamber

from a fluidized bed particle generator. Because of the difficulty of breaking

up the agglomerates, generally the dry particles were 1 _m or larger. However,

large numbers of 1 _m or smaller particles are desired to increase the measurement accuracy of highly accelerated/decelerated flows and turbulent flows.

TiCI 4 as a source of small particles appeared to be a good selection except for

the large amount of HC1 formed. In this application, the gaseous HC1 formed

was not a problem because the exhaust gas was cooled and cleaned by a water

spray system directly downstream from the burner.

An open jet burner as shown in figure 1 was used for the experiment

(ref. 2). This burner has a wide range of temperature and velocity performance. The fuel/oxidizer used is Jet A and air from NASA Lewis Research

Center' s Central air supply system. The temperatures in the combustion chamber

run up to 1426 °C which is below the melting point of A1203 and TiO 2. LA measurements of the exhaust flow velocity distribution were made by an LA fringe

system that is used for development of LA hardware and software systems for

high-temperature applications, The total system is automated (ref. 3).

The injection System used is shown schematically in figure 2. We decided

to use a dry GN2 carrier gas for the TiC14 to prevent particle formation in the

feed line. The feed line was 3/8-in. i.d. The TiC14 was heated to increase

the vapor pressure, but the temperature was not controlled. Additional GN2

also was run through a water bath to pick up moisture and then mixed with the

TiC14 in a concentric mixer inside the burner. Using the GN2 instead of air

to carry the water vapor was not necessary; it was just more convenient to use

one source,of gas. In the concentric mixer, the TiCI 4 gas was the inside tube

and the water vapor was in the outside which extended 1 in. beyond the inside

tub_i This allowed mixing to form particles inside the burner but protected

them from the flame until mixed. The water bath insured Sufficient water in

the GN2 to react to all of the TiC14 being injected.

• TEST RESULTS

: During test runs to evaluate particle generation, the TiC14 carrier gas

pressure was set to 48 N/m 2 (7 psig) and the GN2 moisture carrier gas pressure

was set to 10 N/m2 (1.5 psig). This mixture gave a 50 kHz data rate as measured on an LA data processor. The temperature of the burner gases was measured at 850 °C. Primary and secondary air pressure to the burner were

255 N/m 2 (37 psia) and 138 N/m 2 (and 20 psia), respectively. During a period

of approximately 30 min, the data rate was varied from 1 to 50 kHz by adjusting the TiC14 carrier gas pressure and the water carrier gas pressure. Since

the TiC14 container was loaded with only about 100 ml of liquid, the amount of

TiC14 gas picked up varied significantly with pressure. Since this was a test

configuration to determine feasibility of the method, no attempt was madeto

improve the performance; however, it was evident that several improvements

(listed below) could be made if long term use of this method were desired.

PARTICLE SIZE

, TiO 2 particle samples were collected on polished stainless steel plates

inserted into the hot exhaust stream approximately 30 cm downstream from the

2
burner outlet. Exhaust temperature at the outlet was 850 °C and the velocity

was approximately 300 m/sec. The plates were held in the exhaust at least

30 sec. For analysis the sample plates were coated with 100 _ of gold to

increase particle contrast. Scanning electron microscope photographs of the

plates are shown in figures 3(a) and (b). Figure 3(a) shows a fairly uniform

covering of small particles and also some TiO2-coated large carbon particles.

The gEM photograph of an area of small particles is shown in figure 3(b). This

photograph shows large numbers of particles 1 _m and smaller.

CONCLUSIONS

Large numbers of small particles can be formed by mixing TiCI 4 and watersaturated GN2 at the entrance to a hot gas flow. The HC1 also formed would

need to be neutralized for most applications. In applications where the HC1

can be tolerated or neutralized, the use of TiC14 is a good source of hightemperature particles for hot flow LA measurements.

Some advantages of using TiC14 are: (1) large number density of particles, (2) small size, (3) in-situ generation, and (4) constant rate of generation. Some disadvantages are: (1) toxic source liquid and gas, (2) HC1 to

neutralize, and (3) necessary use of special container materials (glass,

ceramic, or stainless steel) for TiC14. Many improvements could be made to the

injection system used in this experiment. Some suggestions are given below.

1. An injector with an HC1 neutralizer input downstream from the TiC14 and

GN2 mixing volume.

2. A heater and temperature controller for the liquid-TiC14 supply.

3. A controller to maintain a constant pressure differential between the

injector gas and the burner pressure.

4. Water purge to clean lines and GN2 to dry the TiC14 lines before

operation.

REFERENCES

1. Craig, R.R., et al.: A General Approach for Obtaining Unbiased LDV Data in

Highly Turbulent Non-Reacting and Reacting Flows. AIAA Paper 84-0366,

Jan. 1984.

2. Laboratory Combustor System LCS-1, Data Sheet 2, Becon Incorporated,

E. Hartford, CT.

3. Seasholtz, R.G.; Oberle, L.G.; Weikle, D.H.: Laser Anemometry for Hot

Section Applications. Turbine Engine Hot Section Technology 1983, NASA

CP-2289, 1983, pp. 57-68.

3
FUEL _,,-EXHAUST

NOZZLE__ NOZZLE

FUEL __ _'_._

NO_ZTZTEL__S X" _ _t_., ,u. _t=t;, cECO_N_D* ,UNA RY--Lli ENoH2AUST

J _STRUMENTAT'ONL PLATE

Figure 1. - Cross section of Becon open jet burner.

FILL TUBE FOR TiCI4

0-30 pslg ¥

(_ / TiCl, LIQUID

GN2 _ 1 _L / _ _

100 psi- I v _

I o I

(I '_ U I1-11 I1_ OPEN

....... II II I1 11J JET

_wAl_ _ BURNER

Figure 2. - TiO 2 particle generation system for combusting flows.

ORIGINAE PAGE

BLACK AND .WHITE PHOT.OGRAJ_.H

ORIGINAL PAGE IS

OF POOR QUALITY

(a) Larger area.

(b) Small area of figure 3(a) at higher magnification to show TiO2 particles

1 p.m and smaller.

Figure 3. - SEM photographs of an area of TIO2 particles and "rio2 covered

carbon particles on a stainless steel plate,
NationalAeronautics and Report Documentation Page

SpaceAdministration

1. Report No. 2. Government Accession No. 3. Racipient's Catalog No.

NASA TM-102581

4. Title and Subtitle

TIC14 as a Source of TiO2 Particles for Laser

Anemometry Measurements in Hot Gas

7. Author(s)

5. Report Date

April 1990

6. Performing Organization Code

8. Performing Organization Report No.

Donald H. Weikle, Richard G. Seasholtz, and Lawrence G. Oberle

9. Performing Organization Name and Address

National Aeronautics and Space Administration

Lewis Research Center

Cleveland, Ohio 44135-3191

12. Sponsoring Agency Name and Address

National Aeronautics and Space Administration

Washington, D.C. 20546-0001

E-5412

10. Work Unit No,

505-60-01

11. Contract or GrantNo.

13. Type of Report and Period Covered

Technical Memorandum

14. Sponsoring Agency Code

15. Supplementary Notes

16. Abstract

A method of reacting_ with water saturated gaseous nitrogen (G--"N2)at the entrance into a high-temperature

gas flow is described. The TiO2 particles formed are then entrained in the gas flow and used_ as seed particles for

making laser anemometry (LA) measurements of the flow velocity distribution in the hot gas. Scanning electron

microscope photographs of the-TiO2 particles are shown. Data rate of the LA processor was measured to determine the amount of TiO2 formed. The TiCI4 and mixing gas flow diagram is shown. This work was performed in

an open jet burner, at NASA Lewis Research Center.

18. Distribution Statement

Unclassified - Unlimited

Subject Category 35

22. Price"

A02

17. Key Words (Suggested by Author(s))

TiO2 seed

Laser anemometry

High temperature

TiCh

19. Security Classif. (of this report) 20. Security Classif. (of this page) 21. No. of pages

Unclassified Unclassified 6

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