FABRICATION AND TESTING OF A PINTLE INJECTOR

The material chosen for the fabrication of pintle injector is SS-304. The Injector is made of two parts. the outer body and the inner pintle. The pintle is screwed inside the outer body so that the pintle opening distance can be varied for the different experiments.

Figure 6 .2-D drawing of the injector with dimensions in millimeter.

In the outer body of the injector. two inlets are placed diametrically opposite to each other. The diameter of these inlets are 5 mm each. One inlet leads to the outer annular gap and the second one to the center of the injector. The pintle angle is 25°.

Figure 7. Different views of the injector

Figure 8. Sectional view of the outer body 

The spray images from the injector is given below:

Atomization was seen insufficient for the combustion of liquid kerosene and Liquid Oxygen. For kerosene to burn, the mean drop size should be less than 30 to 50 microns.

The challenge with the injector was to achieve the proper propellant distribution through the annular orifice.

Pintle opening (mm)	Pressure (Kg/cm2)	Time (s)	Flow rate Kg/s	Area of Discharge (mm2)	Velocity (m/s)	Reynolds Nu	Webber nu
0.55	1.5	10	0.132	30.549	4.31	2360.438	140.003
0.63	1.5	7.6	0.156	34.992	4.46	2798.799	171.837
0.95	1.5	9.5	0.172	52.766	3.25	3079.86	137.991
1.33	1.5	9.8	0.185	73.873	2.51	3324.432	114.841
1.6	1.5	9.8	0.189	88.869	2.13	3397.698	99.716
1.89	1.5	7.9	0.197	104.977	1.88	3544.577	91.872

The diamter of pintle minimum opening was 8.84 mm. Pintle was screwed to the first part. Some leak was seen in testing.

Annular gap data is given below:

The spray from a  pintle injector with water and air can be seen below:

Radial flow can be seen below: 

 Another thing to notice is the material selection, the material chosen was stainless steel. However welding stainless steel need TIG welding and it was very difficult to find compared to oxyacetylene. It required traveling and extra cost for welding. If the material can be welded with oxyacetylene it would have been time saver. More details of the spray tests will be updated soon.