The final engine design is a low-bypass, axial turbofan, with a BPR of 0.2 and an OPR of 22.87. The final engine length is 166.266 in, 12 in. larger than that specified in the RFP. This was necessary in order to achieve realistic thrust values and to meet other parameters necessary for a successful mission. The final diameter of the engine, 48.1907 inches, came in under the desired maximum of 49.2 inches.
Figure 2: Design Point Input
Pressure recovery at the inlet is modeled using a standard formula for military flight specifications. For Mach numbers below 1, no pressure losses are considered. However, for all supersonic flights, the Intake Pressure Ratio (IPR) is calculated using the formula
where M is the flight Mach number. Because the engine is optimized at Mach 1.15, the design point IPR is set to 0.9942.
The mechanical efficiencies shown in Table 3 are provided in the RFP and can be assumed to be realistic. Deviations from these values require CFG computations for validation; however, no CFG models were found during the research into trade studies. The engine has a gear ratio of 1, effectively removing the gearbox from the analysis.
Figure 3: Parametric Evaluation for Off-Design Points
Figure 4: Mission Breakdown
The final engine’s thrust output and specific fuel consumption values for given Mach speeds and flight altitudes can be seen in Figure 3. The mission output in Table 4 for cruise at Mach 1.15 shows the net thrust for one engine at just under 10,000 lbf. The projected total in-flight requirement from the RFP is just above 20,000 lbf. This suggests that the design engine will meet the thrust requirements in the RFP up to Mach 1.15. The Thrust Specific Fuel Consumption for the same off-design point is 1.0836, comparable to current models in the market.
Figure 5: Flight Envelope
The flight envelope shows the operating space of the engine running on the F-104 Starfighter aircraft, as specified in the RFP. The envelope is constrained by a Turbine Inlet Temperature of 2840 R, a range of equivalent airspeed of 90-1220 knots, and Mach numbers from 0 – 2.1. The contour lines of the envelope show the net thrust provided by the AIAA engine.
The Monarch Engine 