The main concern to achieve ongoing rotorcraft challenges is to provide an efficient and operational needs oriented engine concept. Significant progress towards development and validation of the last generation of SAFRAN Helicopter Engines combustion chamber is presented in this article : the spinning flame combustor. This new combustion chamber concept will enter in service for the first time on the Airbus H160 helicopter, early 2018. This entry in service is the outcome of 40 years of research and development performed at SAFRAN Helicopter Engines, focused on the global optimization of a widened combustion perimeter, considering all parts from the low pressure fuel pump to the combustion chamber exhaust, including valves, fuel pipes, injectors and actuators, and all components involved in the fuel management of the combustor and the combustor itself. The rotorcrafts operational needs, applied to the combustor have not drastically evolved during these last 40 years: in the 80's, the combustor efficiency was already close to 97% and the cold-soaked lighting envelope reaching 6000m and -50°C. Since then, the engine efficiency gains could not be reached through combustor modification (already topping 97% efficiency) and the lighting envelope has not evolved, considering the rare opportunities to soak a helicopter at 6000m and -50°C. Thus, two ideas have driven the research and development of the spinning flame combustor: Simplification providing reduction of mass, cost and unavailability of the engine, with the same operational needs as exposed above Improvement of operational needs, anticipating future applications including hybrid propulsion systems and new power management strategies. To achieve these goals, this technology has been inspired by two existing ones, the benefits of which have been combined : The sling combustor technology invented by TURBOMECA in the early 50's, and still existing in state of the art applications like ARRIEL and MAKILA Turbomeca turboshaft engines, but as well in Williams FJ44 turbojet engines for example. Due to its original rotating fuel injection wheel, the fuel system of such engines is very simple and the resulting combustor and casing are cheap and light. The localization of fuel swirlers and injectors around the combustor, rather at its end, allowing easy maintenance and reducing coking. Such a technology exists on many applications like Pratt and Whitney 206 family engines, as well as APS2000/3000 APU family, etc.... This technology will be called tangential injection in the following chapters. The spinning flame combustor technology combines the simplicity of the fuel system, the low mass and cost of the combustor and casing of the sling combustor, with the maintainability of the tangential injection. To achieve this, the whole airflow will be injected tangentially into the combustor, as well as the fuel through the injectors. Thus, the combustion generated by a fuel injector will be directed toward the next one and so one, creating a unique flame ring spinning into the annular combustor, being beneficial for ignition, compacity and homogeneity. In order to develop and bring into service such a new technology, the most advanced innovative concepts regarding design, technologies and manufacturing process have been used in order to reach a very high level of optimization. In particular, it requires a deep knowledge of several complex phenomena. Combining advanced CFD simulation and experiments provide a clear understanding of the way to optimize the integrated concept. As a result, the presented technological breakthrough brings an extended operational range of use thanks to an improved flame stability combined with an optimized gas temperature homogeneity at the combustor exit. Moreover, additive laser manufacturing and components combination induces drastic weigh reduction of more than 30% compared to previous turboshaft generation combustion chamber. Customer will take immediately advantage of the spinning combustor technology in term of mass, reliability, security and cost of operation. Due to the design choices, easy repair solutions for inspections accessibility are provided. The improvement of stability performances achieved will be used in future rotorcrafts applications in order to develop new hybrid or innovative propulsion strategies that may generate new engine operational needs like fast restart or automatic inflight relight for example.
展开▼
