Yuvaraj
Batch Requestor works similarly to the Browser Requestor. When you log in through Browser, Pega identifies the web nodes based on the balancer and creates your requestor in any one of the nodes. In the same way, if you have 2 Background processing nodes, Pega creates a requestor in any one of the nodes (Random) during every Job Scheduler execution.
To make it run on one node consistently out of two available nodes, Please add your background processing node to a secondary node type (Say Custom1) and configure your Job Scheduler to run on the newly configured node type.
A node can be tagged to more than one node type. Please refer to our article to see how we can associate a node to multiple node types.
We would also like to understand why you want to make it run only on Node1 and not on Node2 when both are of the same type?