Abstract
Emission measurements from unsteady combustion systems such as Pulse Detonation Combustion (PDC) are challenging due to the inherently large variations in pressure, temperature, composition, and flow velocity of the exhaust gas. Comparison of experimental data is additionally complicated by differences in operating conditions and gas sampling setup between different facilities. Qualitative considerations with regard to the sampling process from PDC, based on one-dimensional simulations, indicate a systematic influence of the sampling setup and extraction process on the resulting concentration measurements. Therefore, operating frequency, sample time, fill time, as well as PDC outlet and probe geometry were varied experimentally in order to assess the degree to which each of these parameters impact the resulting measured {rm NO}_{rm x} in order to better inform researchers of these effects when making measurements. It was shown that measured {rm NO}_{rm x} emissions can vary significantly depending on the choice of these parameters and therefore care must be exercised in order to reduce the influence of the sampling technique when aiming for comparable results.
Highlights
Combustion systems are required to become increasingly more efficient, while at the same time allowing for compact and maintained designs suitable for a more decentralized energy infrastructure
Conventional combustion by means of a spark plug is initiated (3). This is followed by a rapid deflagration to detonation transition (DDT), which is usually enhanced by constricting the tube’s inner diameter or supporting shock focusing by geometry alterations
Due to the differences in operational time scales discussed in the previous section, the interaction of a fluctuating pulse detonation combustion (PDC) exhaust gas flow with a subsequent continuous emissions monitor (CEM) is to a certain extent unknown
Summary
Combustion systems are required to become increasingly more efficient, while at the same time allowing for compact and maintained designs suitable for a more decentralized energy infrastructure. Its main feature is the consumption of a premixed fuel-oxidizer mixture by a supersonic detonation wave traveling through the combustion chamber. The leading shock wave is reflected as a rarefaction wave that initiates the blowdown or exhaust stage of the cycle During this phase, the combusted gases are expanded and further accelerated towards the tube exit (6). The final pressure of the combustion products ( p3 ) before the arrival of the first expansion wave from the tube exit depends on the upstream boundary conditions but typically ranges in between 5 bar and 10 bar
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