Crossover Tube Research Articles

Shock-Initiated Combustion in an Airbreathing, Pulse Detonation Engine-Crossover System

An airbreathing pulse detonation engine-crossover system is developed to characterize the feasibility of shock-initiated combustion within an airbreathing pulse detonation engine. A shock wave is transferred through a crossover tube that connects a spark-ignited driver pulse detonation engine to the airbreathing, driven pulse detonation engine. Detonations in the driven pulse detonation engine develop from shock-initiated combustion caused by shock wave reflection. The pulse detonation engine-crossover system increases system efficiency through decreased deflagration-to-detonation transition distance while employing a single spark source to initiate a system consisting of multiple detonation tubes. The initiation effectiveness of shock-initiated combustion is compared to spark discharge initiation and detonation injection through a predetonator. Increasing the Reynolds number enhances combustion wave acceleration. However, for all initiation methods, the system requires a device to transition the combustion wave to a detonation. Shock-initiated combustion and predetonator initiation produce comparable detonation transition runup lengths. With an incident shock wave Mach number of , the runup length is decreased by up to 61% compared to the spark discharge method. Similar combustion evolution is observed for an incident shock wave of strength .

Optimization of a multiple pulse detonation engine-crossover system

A University of Cincinnati experimental study is conducted on a Pulse Detonation Engine (PDE)-Crossover System to investigate the feasibility of repeated, shock-initiated combustion as a means to generate detonation within an annular array of detonation tubes. An optimization study of the system finds that reducing driver PDE length increases auto-ignition failures in the driver PDE due to undesirable feedback of hot products from the driven PDE. Initiation performance in the driven PDE is strongly dependent on initial driven PDE skin temperature in the shock wave reflection region. The optimum initiation performance is achieved within the driven PDE by filling the driver PDE with reactants past the crossover tube entrance. Increasing operating frequency negates the detrimental effect of increased nitrogen dilution. An array of detonation tubes connected with crossover tubes is developed using optimized parameters. Successful operation utilizing shock-initiated combustion through shock wave reflection is achieved and sustained. Results from this array show that if initially driven PDE tubes are operating successfully, all subsequently driven PDE tubes also operate successfully.

Characterization of Shock Wave Transfer in a Pulse Detonation Engine–Crossover System

Shock wave propagation within a pulse detonation engine–crossover system is investigated, examining the properties and mechanisms of the transfer process. A shock wave is transferred through a crossover tube that connects a spark-ignited driver pulse detonation engine to a secondary, driven pulse detonation engine. Detonations in the driven pulse detonation engine develop from shock-initiated combustion, as strong shock wave reflection can cause ignition within a reactive mixture. A pulse detonation engine–crossover system can decrease deflagration-to-detonation transition length while employing a single spark source to initiate a system consisting of multiple detonation engines. Visualization of a shock wave propagating through a clear channel reveals a complex shock train behind the leading shock wave. Transverse waves connect with the leading shock wave to form a triple point that oscillates through the leading shock wave. The shock wave Mach number and decay rate remain constant for varying crossover tube geometries and operational frequencies. A temperature gradient forms within the crossover tube due to forward flow of high-temperature ionized gas into the crossover tube from the driver pulse detonation engine and backward flow of ionized gas into the crossover tube from the driven pulse detonation engine. This communication results in intermittent autoignition of the driver pulse detonation engine for higher-frequency large-crossover-tube-diameter cases. However, small-diameter crossover tubes prevent these autoignition events at higher frequencies.

Shock Transfer and Shock-Initiated Detonation in a Dual Pulse Detonation Engine/Crossover System

An experimental investigation was carried out to study the propagation of a shock wave through a crossover tube for the purpose of causing shock-initiated detonation. A pulse detonation engine was used as a driver source to propagate a shock wave through a crossover tube into a second, adjacent detonation tube (that is, driven). Results showed a transferred shock wave achieved shock-initiated detonation, and for specific crossover tube geometries, there was a maximum effective crossover tube length for which the event was possible. This maximum effective length was strongly correlated to the strength of the transferred shock. Initiation performance in the driven detonation tube declined when the incident shock strength decreased below . Introducing a bend to the end of the crossover tube increased the driven detonation tube initiation performance by enhancing the strength of the transferred planar shock wave by an average of 20%. A numerical investigation on shock wave planar attenuation in a crossover tube corroborated the experimental results.

해양레저산업 활성화를 위한 아이디어 상품 디자인개발 사례

With the recent rapid growth in the number of people who enjoy marine and leisure activities in Korea, the marine leisure industry faces good opportunities for development. Korean brands are in between them. In this situation, new and innovative products related to an inflatable tube, which is one of the most popular marine leisure items, will help to increase sales of domestic companies and to pioneer a new market. Research methods are largely divided into 4: investigation, analysis & synthesis, development and evaluation. This paper introduces a which is an inflatable tube covered by fabrics. It can be functioned at home 365 days a year as a cushion or a children`s plaything. Tactile fabrics, neoprene and air-mesh, are used as the cover with a zipper, making it easy to open and close. Moreover, by putting together tubes and connecting them with snap fastener attached straps, the cushion can be transformed into a chair, a table, a tunnel, a train, and so on, serving as a creative plaything for children. With this paper, it is expected that new and innovative items differentiated from others, like this crossover tube cushion, will help to create a `Blue Ocean` market for the marine leisure industry from the long-term perspective.

Failure analysis of an aero-engine combustor liner

The paper presents a failure case of an aero-engine combustor liner. Macroscopic and microscopic observations, microstructure investigation, chemical analysis and hardness measurement have been performed to investigate the damage mechanism and failure causes of notches and cracks. The results show that the failure modes of notches, axial-direction crack along the combustor liner and crack at the edge of welding spot are respectively attributed to high-temperature ablation, mixed crack of ablation and thermal fatigue crack. The bad configuration of crossover tube is the main reason for the failure of combustor liner.

Multimegavolt Laser-Triggered Gas Switching With a Green Laser and Beam Transport Through Water

Ultraviolet (UV) laser-triggered gas switching using beams at 266 nm has greatly improved the simultaneity of many large multimodule accelerators. This UV beam however cannot be transmitted significant distances through water or oil. Since the switches in these accelerators are typically submerged in water or oil, the beams are often conveyed to the switches through gas-filled laser crossover tubes. These crossover tubes are difficult to field grade properly and are subject to frequent mechanical and electrical failures in the pulse-power environment. We have demonstrated that a 4.6-MV multistage gas switch insulated with SF6 can be triggered with a jitter of less than 10 ns using 110-mJ pulses of a green (532-nm) beam that has been transported through 67 cm of 1-MOmega-cm water on its way to the switch. These results may allow elimination of the crossover tubes in future accelerators.