Who makes gas turbines (onsite / behind-the-meter) & hrsgs for AI data centers

Gas turbines convert natural gas into rotating mechanical energy that drives a generator, either as a simple-cycle unit or paired with a heat-recovery steam generator (HRSG) in a combined-cycle plant for higher efficiency. In the data center context they sit upstream of the utility interconnection or, for behind-the-meter builds, upstream of the facility's own switchgear and transformers (Layer 7), providing firm power where grid interconnection queues or capacity are constrained. Aeroderivative turbines (adapted from jet engines) are favored for faster startup and modularity at campus scale, while heavy-frame industrial turbines suit larger, grid-connected combined-cycle plants. An investor should watch order-book length at the handful of OEMs that build new units, the smaller pool of specialists that refurbish older units and broker turbine "slots," and the HRSG makers whose capacity is a separate, often overlooked constraint on how fast a combined-cycle plant can actually be built.