Since 1998, the Honeywell Engines & Systems, Combustion & Emissions Group has been developing an advanced, CFD-based, parametric, detailed design-by-analysis tool for gas turbine combustors called Advanced Combustion Tools (ACT). ACT solves the entire flow regime from the compressor deswirl exit to the turbine stator inlet, and can be used for combustor diagnostics, design, and development. ACT is applicable to can, through-flow, and reverse-flow combustors, and accommodates features unique to different combustor designs. The main features of ACT are: 1. Reduction of Analysis Cycle Time: Geometry modeling and grid generation are fully parametric and modular, using an inhouse feature-based technology. Each geometrical feature can be deleted, replaced, added, and modified easily, quickly, and efficiently. 2. Elimination of Inter-Feature Boundary Assumptions: All the complex combustor features, such as wall cooling configuration, details of the air swirler assemblies and fuel atomizer systems, dome-shroud/cowl wall, and splash cooling plate, are considered and fully coupled into the CFD calculations. This allows the plenum and annulus aerodynamics to interact directly with the combustor internal flow. 3. Ease of Use: To reduce setup time and errors and to facilitate parametric studies, ACT is highly customized for engineers. 4. Accurate and Efficient CFD Solutions: Advanced physical submodels of combustion and spray have been implemented. This paper provides an overview and development experiences of ACT. Application of ACT to a through-flow combustor system is presented to illustrate the approach as applied to real-world combustors. Validation of the ACT system, by comparison to test cell data, is in-progress and will be the subject of a future paper.