How LASERDYNE® Machines are Enabling Greater Use of Shaped Cooling Holes

Modern gas turbines include a large number of small (less than 1 mm diameter) laser drilled holes to provide cooling in jet engine components. The majority of holes used for this purpose have been cylindrical. However, recently the benefits of using shaped holes have been recognized.

There are several reasons why laser drilling of shaped holes has become increasingly popular. First, shaped holes can provide superior cooling for a turbine engine component. Film cooling holes increase efficiency of cooling air by 30%, reducing the amount of air required for cooling. Proper design of cooling components with shaped holes can result in fewer holes to accomplish a superior result.

A second reason for the increasing popularity of shaped holes is that fewer holes mean shorter production cycle times, lower production costs, and a lower cooling air requirement. This results in a more efficient and cost effective engine.

The specific interest in laser processing comes from its speed relative to competitive methods and its ability to produce shaped holes in parts with thermal barrier coatings (TBC).

Work has been carried at Prima Power Laserdyne to develop laser and processing parameters to produce shaped holes with both coated and uncoated nickel based superalloys.

Drilling tests were carried out using ShapeSoft™, an S94P feature that supports drilling different shape holes. Some of the drilling results are highlighted in the pictures within this article.

ShapeSoft helps to create programs for producing cone, oblique cone, fan, racetrack (Figure 1) and a variety of other shaped holes in a wide range of turbine engine components including blades, nozzle guide vanes and combustors for aero-engine and industrial gas turbine applications.

Figure 1: Different types of laser drilled shape holes

Cone Shape	Oblique Cone
Fan Shape	Racetrack Shape

Figure 2 shows the geometry of a fan shaped hole and the cross section of the hole which was drilled at 30 degrees to the surface. The shape can be varied by changing the laser and processing parameters as well as the angle of incidence.

Figure 2: CAD model of a fan shaped hole (left) and crossection of holes drilled perpendicular to the surface (center) and at 30 degrees to the surface (right).