A unique, three-part undergraduate gas turbine engine design project was developed to acquaint students, working in teams of two or three, with the process of engine cycle selection. The design application is a low-flying, Close Air Support (CAS) aircraft using a separate exhaust turbofan engine. Both spreadsheets and commercial software are used. The commercial software is included with the course textbook, “Elements of Gas Turbine Propulsion” by Dr Jack D. Mattingly. Using commercial software, reinforced by classroom lectures, allows the students to focus on the design decisions. The first part of the project is Mission Analysis which introduces the student teams to the design problem. A spreadsheet template is given to each student team that includes aircraft and mission profile specifications. The students must complete the spreadsheet and develop the relationships for lift, drag, thrust required, and fuel burn to calculate a useable fuel remaining at the end to the mission. The spreadsheet allows the students to obtain an average specific fuel consumption that results in 1500 lbm of fuel remaining at the end of the mission. This target value is used in the second part of the design process, on-design Parametric Cycle Analysis (PCA), as a basis for engine cycle selection. Parametric Cycle Analysis is accomplished using the program PARA.EXE. PARA.EXE generates a carpet plot of possible engine design choices by varying the compressor pressure ratio, bypass ratio, and fan pressure ratio. From these carpet plots the students must identify three possible engine cycles that meet the target value for specific fuel consumption found during the mission analysis. Tradeoffs between thrust and fuel consumption are discussed and the students are required to justify their choices for the engine cycle. The last part of the project is the off-design Engine Performance Analysis (EPA) using the program PERF.EXE. The chosen engines must fly the mission and meet the required performance and mission constraint. Based on the overall mission performance, the students narrow the field of three possible engine cycles to one. Each student team then does a sensitivity study to determine if there is an additional benefit for slight changes in the design choices. The result of this sensitivity study is the students’ final engine cycle. With this cycle, an additive drag calculation is made using the program DADD.EXE to account for losses (off-design) and these losses are then factored back into the performance spreadsheet to check the engine’s capabilities for completing the mission. The iterative nature of the design process is emphasized throughout but only one pass through the process is accomplished. Units are given in English Engineering, as that is what is required for the project. Both SI and English Engineering units are taught in the course.
Investigation of Micro Gas Turbine Systems for High Speed Long Loiter Tactical Unmanned Air Systems
