Fluidic Injection Thrust Reverser System for High Bypass Ratio Turbofan Engines: Experimental Model

Conventional thrust reversers involve the usage of mechanical blockers which are very bulky as they are designed to sustain heavy loads. As a result, they account for 30% of the nacelle weight (excluding the engine core). This added engine weight results in a 0.5%-1% increase in the specific fuel consumption of the aircraft adding a significant operational and maintenance cost over the service of the aircraft. Fluid injection based Blockerless Engine Thrust Reversers are proposed as a possible alternative for this bulky design. A continuous radial high momentum fluid jet is used to block and reverse the fan flow into the cascade vanes. The fluid used for the radial jet is sourced from the compressor and therefore the design and the operation need to be optimized so as to bring the injection requirements as low as possible. Previous computational investigations have shown that effective thrust reversal can be achieved using this method. Eliminating the mechanical blockers results in a massive weight reduction accompanied with lesser wear and tear, pressure losses and leakages culminating in an overall reduction in operating costs. This paper advances our investigation of “Blockerless Engine Thrust Reversers” and uses it as an inspiration to optimize the system by designing an injection module (depicting an injection as a bleed from the core flow), conducting a computational analysis and demonstrating the viability of the process by building an experimental model of a 1:40 scale of a GE90 - 115B engine. A detailed analytical and computational analysis is performed for the novel thrust reverser design. A control volume based analysis is first used to generate design and operation points, which are then used to perform a more detailed computational analysis. A 3D printed experimental model was built after conducting an extensive parametric analysis. This model is used to demonstrate the viability of the “Fluidic Injection Thrust Reverser” (FITR) qualitatively and quantitatively. Three main components of the model are: air supply (fan flow and fluidic injection), force sensing and assembly mounting. As mentioned earlier, for simulating the main fan flow, an electric ducted fan (EDF) is used. For the fluidic injection, the compressed air inlets provided in the engineering labs of the Experimental Research Building at NYU Abu Dhabi are used. The final parameters for the experimental model were as follows: θ = 50 (angle of injection), i = 8.5mm (injection location), W_f = 0.0017 kg/s (fan flow rate), W_c= 0.0005 kg/s (injection rate), W_ne = 0.0004 kg/s (exhaust flow rate). Force-sensitive resistors (FSRs) are used for measuring the thrust in the experimental setup. The engine model presses against these FSRs and reports the required readings for thrust computations. The FSRs are programmed using an Arduino Uno and are coded to give us the analog reading as well as the force measurement in Newtons. Further, to make the sensing system more sensitive, a higher value resistor (33,000 Ω) is used in the circuit. The sensor is then calibrated and used as per requirements. The assembly is suspended via suspension wires on a custom-made suspension frame.A net negative thrust force reading proved that thrust reversal is successfully achieved using this fluid injection based thrust reversal mechanism. It is observed that ∼71.5% of the fan flow (mass flow rate) and ∼78% of the total flow is deflected out of the cascade vanes.