Fiber-coupled Picosecond Pulse Train Initiated Microwave Ignition for Lean-burn High-pressure Combustion Air Heaters in AEDC

ABSTRACT: The objective of the Phase-I effort proposed by Spectral Energies LLC is to demonstrate feasibility of highly reliable fiber-coupled picosecond laser initiated microwave-enhanced ignition technology to satisfy strict requirements for the ignition system in Aerodynamic and Propulsion Test Unit (APTU) at AEDC. The concept is based on the combination of two state-of-the-art techniques: using actively-controlled, low-energy, ultrashort laser pulses to efficiently generate weakly ionized plasmas and meanwhile using high-power microwave to enhance the laser-induced plasmas into a guaranteed ignition of ultralean fuel air mixture. The use of ultrashort laser pulses can significantly reduce the required laser energy for plasma generation and make it possible for reliable fiber delivery. Microwave enhancement of the laser-induced plasmas guarantees successful ignitions in ultralean, high flow speed conditions in combustion air heaters (CAH) and significantly broaden application conditions. Single and/or multiple points and possible homogeneous ignitions can be achieved by using fiber multiplexer delivery. The proposed techniques and an integrated ignition system will overcome the major problems of current flame ignition system in AEDC, possibly generate new test conditions, and have great potential to being commercially available for a wide variety of internal combustion and gas turbine engines. BENEFIT: Improvement on combustion air heater (CAH) ignition system will greatly help lower the costs, increase the efficiency, and decrease possible safety concerns of the wind tunnel test in AEDC. Additionally the improvement on the lean-burn combustion ignition may be used to significantly increase efficiency of the internal combustion and gas turbine engines and reduce NOx emissions. Under the current program, a novel ignition concept based on fiber-coupled ps laser pulse initiated microwave-enhanced ignition system will be developed, enabling an array of new marketable products and technologies for lean-burn high-pressure combustion ignition system. Specifically, 1. Immediate benefits to AEDC test facilities: Implement of novel ps laser initiated microwave ignition system in the CAH of AEDC will greatly help increase the efficiency and reliability of ignition system by depositing the laser pulse and microwave energy without overdriving the gas mixture, decrease safety concerns by eliminating the pilot flame ignition system involving unsafe hydrogen gases, generate deeper penetration into the combustion chamber by multiple points and even near homogeneous ignitions, and simplify the operation procedure of current ignition system by using an all-solid-state turnkey system. 2. Scientific discovery Understanding the fundamental behavior of laser and microwave induced plasmas ignition at fuel-lean, poor quality, and high-pressure conditions is a rich field of intellectually stimulating scientific challenges, which can quickly translate into technologies that provide societal benefits into internal combustion and gas turbine engines. 3. Energy and environmental security New concept of the proposed technology will also be viable on reciprocating natural gas engines, industrial engines, and gas turbines for power-generation or aircraft etc. It will greatly help the relight processes for aircraft gas turbine engines at the high altitude in the event of a flameout. The emission reduction by applying the advanced ignition methods to gasoline internal combustion engines will have a huge impact on the environments. 4. Economic security and prosperity The enormous roles of gasoline and gas turbine engines in the modern life are overwhelming. Even slight efficiency improvement by advanced laser and microwave ignition on the traditional gasoline and gas turbine engines will have huge impacts on almost every corner of the US economy. The successful development of the commercial products will extend the global leadership of US on manufacturing and R & D in engines manufacturing.