Fabrication of load compressor scroll housing

Abstract

A method of fabricating a load compressor scroll housing includes the steps of forging near net shape parts that are machined and subsequently welded together. The forged portions are machined to define specific features of the scroll housing along with the mating surfaces. An interface between top and bottom portions is defined within the volute chamber. The weld joint at the interface provides a finished surface within the volute chamber such that airflow is not adversely affected and additional machine process are not required within the volute chamber after formation of the weld joint.

What is claimed is: 
     
         1 . A load compressor for an auxiliary power unit comprising:
 a scroll housing including a top portion welded to a bottom portion defining a volute chamber having an outer wall and a annular passage open to an inner cavity, a welded interface between the top portion and the bottom portion disposed on the outer wall within the volute chamber; and   an impeller supported for rotation within the inner cavity.   
     
     
         2 . The load compressor for an auxiliary power unit as recited in  claim 1 , including a bearing arrangement supported within the scroll housing for supporting rotation of a shaft, the shaft supporting rotation of the impeller. 
     
     
         3 . The load compressor for an auxiliary power unit as recited in  claim 2 , wherein the outer wall of the scroll housing includes a boss at the location of the welded interface. 
     
     
         4 . The load compressor for an auxiliary power unit as recited in  claim 1 , wherein the volute chamber comprises an outer wall with the interface between top and bottom portions being at the outer wall. 
     
     
         5 . The load compressor for an auxiliary power unit as recited in  claim 4 , wherein the outer wall comprises an inner surface that is part of the volute chamber and an outer surface that forms an outer surface of the scroll housing. 
     
     
         6 . The load compressor for an auxiliary power unit as recited in  claim 5 , including a finished surface within the volute chamber at the interface of the first and second mating surfaces. 
     
     
         7 . An auxiliary power unit comprising:
 a turbine engine driving a shaft; and   a load compressor driven by the shaft, the load compressor including a scroll housing including a top portion welded to a bottom portion defining a volute chamber having an outer wall and a annular passage open to an inner cavity, a welded interface between the top portion and the bottom portion disposed on the outer wall within the volute chamber, and an impeller supported for rotation within the inner cavity.   
     
     
         8 . The auxiliary power unit as recited in  claim 7 , including a bearing arrangement supported within the scroll housing for supporting rotation of a shaft, the shaft supporting rotation of the impeller. 
     
     
         9 . The auxiliary power unit as recited in  claim 8 , wherein the outer wall of the scroll housing includes a boss at the location of the welded interface. 
     
     
         10 . The auxiliary power unit as recited in  claim 7 , wherein the volute chamber comprises an outer wall with the interface between top and bottom portions being at the outer wall. 
     
     
         11 . The auxiliary power unit as recited in  claim 10 , wherein the outer wall comprises an inner surface that is part of the volute chamber and an outer surface that forms an outer surface of the scroll housing. 
     
     
         12 . The an auxiliary power unit as recited in  claim 7 , wherein the impeller is driven by the shaft. 
     
     
         13 . The auxiliary power unit as recited in  claim 7 , wherein the turbine engine includes a compressor impeller communicating compressed air to a combustor surrounding a turbine section, the combustor communicating a high energy gas stream to the turbine to drive the shaft. 
     
     
         14 . The auxiliary power unit as recited in  claim 13 , wherein the shaft comprises a common shaft driving the compressor impeller and the impeller of the load compressor supported within the inner cavity.