Instability of Detonation Wave at Downstream of Aluminum Crimped Ribbon

Natural gas is a very reactive fuel that easily causes a detonation wave, especially when the oxidizer is enriched with oxygen or pure oxygen. If the combustion wave is not controlled, a detonation wave can occur, which is dangerous for the safety of workers and industrial facilities. This study was conducted to develop a prototype of a detonation arrester to control detonation waves by using a detonation test tube with a total length of 3000 mm. The characteristics of the combustion wave were evaluated in the present study using a pressure sensor, an ion probe sensor, and a soot track record plate. Results showed that the propagation velocity of the combustion wave and the shock wave pressure increased, whereas the detonation cell size and the reinitiation distance decreased. The experiments performed were able to produce a shock wave pressure that was close to the Chapman–Jouguet pressure. The use of a detonation arrester model could reduce the shock wave pressure and the velocity of the combustion wave. At the initial pressure of the gas mixture of natural gas–oxygen of 10 kPa, the observed combustion phenomenon was deflagration. By contrast, when the initial pressure of the gas mixture of natural gas–oxygen was increased to 20 kPa, the observed combustion phenomenon was detonation quenching.  Furthermore, increasing the initial pressure of the natural gas-oxygen mixture to 30 kPa or higher led to detonation wave propagation as the observed combustion phenomenon.

Arrester model; Detonation quenching; Detonation reinitiation; Detonation wave

Natural gas, which mainly consists of methane gas, is a fuel that is often used in industrial processes (Faramawy, Zaki, and Sakr, 2016). The use of natural gas as a fuel is also considered to fulfill energy needs in various applications, including transportation sectors, industries, and households (Supriyanto et al. 2022; Farizal, Dachyar, and Prasetya 2021; Rosyidi et al. 2020). Natural gas plays a crucial role as a transition fuel for sustainable energy systems toward a cleaner environment (Ediger and Berk, 2023; Bugaje et al., 2022; Mohammad et al., 2021; Safari et al., 2019). Meanwhile, to meet the safety standard, the design of an industrial system should consider any hazardous aspects, for example, a spontaneous fire (Thabari et al. 2023), and high propagation flame which may cause severe accidents (Hou et al., 2022; Zardasti et al., 2017; Sovacool, 2008). Interestingly, natural gas easily reacts and causes a detonation wave, particularly when the oxidizer is enriched with oxygen or pure oxygen, such as in glass-forming industries. worse conditions, the natural gas mixture may induce detonation during transport and storage (Sun and Lu, 2020b).

Detonation is a combustion wave that propagates at supersonic velocity and increases when the pressure reaches 20 to 30 times the initial pressure (Zhang et al., 2020). In more detail, it is also defined as a reactive shockwave that propagates at a nearly ideal Chapman-Jouguet (CJ) velocity, trailed by chemical reactions (Lee, 2008). Consequently, the compression and ignition of the air-fuel mixture by the shockwave lead to an energy release, supports the shockwave propagation (Pan et al., 2017). The detonation wave created in a combustible gas mixture can be very dangerous if it interacts with human bodies or artificial structures due to the high pressure and temperature behind the wave. The detonation behavior can be the detonation wave was quenched, and the detonation wave was initially quenched behind the block but then re-initiated again due to the focusing mechanisms of a reflected shock wave on a central axis (Obara et al. 2006a; 2006b). Detonation control can be applied by converting the detonation wave into the deflagration wave, which has less energy, to prevent damage caused by the detonation wave (Sun et al., 2022; Ciccarelli, Johansen, and Parravani, 2011). A simple method to reduce the detonation wave is to reduce the channel diameter. The study was conducted by Gholamisheeri, Wichman, and Toulson (2017) using experiments and simulations where the detonation propagation can also be controlled in tube and obstacle geometries.

Furthermore, one of the methods that can be used to convert detonation into deflagration is to absorb the wave energy, which can be absorbed by installing the orifice or arrester in the detonation track. This method is supported by experiments using the channel geometry that can affect the flame acceleration and deflagration to detonation transition (DDT) in a detonable mixture (Azadboni et al., 2017; Ettner, Vollmer, and Sattelmayer, 2014) and can be adapted without disturbing the gaseous fuel flow.

Several researchers have conducted studies of detonation propagation and control using a plate with an orifice for the hydrogen-oxygen gas mixture. Their results showed that the orifice with small holes caused the detonation quenching phenomenon. Otherwise, the presence of an obstacle in the pipeline ensured the easy and rapid development of flame acceleration from the deflagration wave to the detonation wave (Sun and Lu, 2020a; Wang et al., 2018a; Rainsford, Aulakh, and Ciccarelli, 2018; Cross and Ciccarelli, 2015; Teodorczyk, Drobniak, and Dabkowski, 2009). The reinitiation of detonation is influenced by the detonation instability, which is affected by the size of the orifice or obstruction and flow velocity. Examples in this field include the reinitiation process of detonation waves behind slit-plates (Obara et al., 2008), notably influenced by initial test gas pressure (Obara et al., 2006b) and slit-plate configuration (Sentanuhady et al., 2007). Visualization of re-initiation and quenching processes of detonation wave behind slit-plate was conducted by Obara et al., (2007).

Meanwhile, metal is the best material to absorb the detonation energy since it has a high thermal conductivity. Increasing the detonation energy absorption area and thermal conductivity of the arrester can affect the effectivity of detonation quenching. These parameters can increase the heat transfer in the arrester because one of the factors that can influence detonation quenching is heat transfer (Thomas, Oakley, and Bambrey, 2020). A study using a crimped ribbon flame arrester was conducted by several scientists, and they varied the length of the arrester (see a brief review from Wang et al., 2018b). Sun et al. (2018) numerically investigated detonation wave propagation and quenching in an in-line crimped-ribbon flame arrester, offering key insights into initiation, quenching rules, and the impact of structural parameters on propagation. Moreover, the parameters used to assess the flame arrester's effectiveness are the propagation velocity of the combustion wave, shock wave pressure, reinitiation distance, and detonation cell size.

This study aimed to observe and analyze the characteristics and combustion phenomena of natural gas–oxygen mixture with an equivalence ratio of unity through a detonation arrester model with various initial pressures (i.e., between 10 kPa and 100 kPa). The arrester was made from an aluminum sheet with a crimped ribbon configuration. Furthermore, insights obtained from this study are expected to improve the current understanding of detonation quenching and the development of flame arrester devices. 

This study used a detonation test tube with an inner diameter of 50 mm and a total length of 3,000 mm. The detonation test tube consisted of three parts, namely, the driver section tube, driven upstream tube, and driven downstream tube where each section has a length of 1,000 mm, respectively. The details of experimental facility can be found in our previous paper (Sentanuhady et al., 2021) and only the main features are presented here. Figure 1 illustrates the schematic diagram of the detonation test equipment. 

The combustion process in the driver section tube was initiated by a spark plug installed in the upstream part of the driver section. One pressure sensor (P₁; PCB Piezotronics S111A26 series) was mounted on the driven upstream tube 1,900 mm from the spark plug, and two pressure sensors (P₂ and P₃) were mounted on the driven downstream tube 2,100 and 2,200 mm from the spark plug. The pressure sensor mounted on the driven upstream tube was used to measure the amount of shock wave pressure, whereas the ion probe sensor mounted opposite the pressure sensor was used to detect the arrival time of the combustion wave.

Detonation waves can be visualized as a detonation cell structure placed along the driven downstream tube and recorded using the soot track record plate. The soot track record plate was made of 0.3 mm-thick aluminum, whose surface had a layer of film from kerosene-burning soot. Mylar film with a thickness of 0.03 mm was inserted between the driver section tube and the driven upstream tube and between the driven downstream tube and the dump tank. The arrester model was installed in a housing that was placed between the driven upstream tube and the driven downstream tube. The housing of this arrester model was 100 mm long with an inner diameter of 50 mm. In this study, a crimped ribbon flame arrester model with a length of 25.4 mm was used. The arrester model used in this study is made of aluminum with a thickness of 0.2 mm and BR = 34.6%. Here, BR (blockage ratio) is defined as the ratio of the covered metal area to the cross-sectional area of the tube used.  Figure 2 shows the photograph of arrester model used in the present study.

Figure 1 Schematic of the detonation test equipment

Figure 2 Arrester model (a) design and (b) postproduction

The experimental conditions applied in this study are shown in Table 1. The fuel used in the driver section tube was a stoichiometric mixture of hydrogen-oxygen at a pressure of 100 kPa, whereas the fuel used in the tube was a gas mixture of natural gas–oxygen with an equivalence ratio of unity and various initial pressures. The gas pressure used for the mixing process of both hydrogen–oxygen and natural gas–oxygen in the mixing tank, as well as the injection of the gas mixtures into the detonation test tube, is regulated and controlled using a high-precision pressure sensor. The natural gas used in this experiment is natural gas sourced from Indonesian wells that have a methane number of 96.7. In the present study, we ensure that the equipment and tools used are calibrated by the manufacturer. Thus, all the parameter testing is in the range of the equipment specification of the tools.

Table 1 Experimental conditions

The experimental results on the propagation of the gas mixture are presented. Without an arrester model, the natural gas-oxygen combustion wave showed two observable characteristics: deflagration waves and detonation waves. During testing with an initial pressure of 10 kPa, a deflagration wave was observed. Increasing the starting pressure to 20 kPa accelerated the combustion process, resulting in the formation of a detonation wave. Similarly, a detonation wave was formed at initial pressures above 20 kPa. The detonation waves produced within the range of 20-100 kPa can be classified into two types: unstable and stable.

An unstable detonation wave was observed at initial pressures ranging from 20 to 50 kPa, while a stable detonation wave was detected at pressures higher than 50 kPa. This is attributed to the rapid combustion reaction caused by the high initial pressure of the gas mixture (Song et al. 2018; Miao et al. 2008). Furthermore, a substantial quantity of heat energy was created, resulting in a rapid DDT formation process. The response velocity fluctuated with an unstable detonation wave, causing the detonation wave's propagation velocity to vary or be unstable. This phenomenon can be attributed to the formation of a detonation cell structure on the surface of the soot track record plate, with the instability of the detonation cell size occurring under unstable detonation wave conditions. The combustion wave propagation mechanisms of both deflagration and detonation waves at various initial pressures are shown in Table 2.

Table 2 The propagation mechanism of combustion wave without an arrester model

The installation of the detonation arrester model between the driven upstream tube and the driven downstream tube resulted in different characteristics and combustion at the downstream tube of the arrester model compared with the conditions without an arrester model. The combustion experiments using a detonation arrester model resulted in three characteristics of the combustion wave, namely, deflagration, detonation quenching, and detonation reinitiation, as listed in Table 3.

The classification of combustion wave propagation is based on the changes in the combustion wave propagation pattern that can be observed on the soot track record plate both without and with an arrester model. The detonation quenching phenomenon, which only occurred under the conditions with the arrester model, was formed because of the quenching process of the detonation waves due to heat loss through the arrester model. Thus, the combustion wave that occurred downstream of the arrester model was a deflagration wave. Along the driven downstream section of the tube, no DDT phenomenon occurred. The DDT phenomenon is the transition of the combustion wave from subsonic velocity to supersonic velocity. Furthermore, when the velocity of the detonation wave at the driven upstream tube was sufficiently high, as generally occurs at high initial pressures of the gas mixture, the combustion wave that emerges from the arrester model was a deflagration wave. This deflagration wave immediately propagated and interacted with the inner wall of the tube, converting into a detonation wave. This phenomenon is known as detonation reinitiation.

Table 2 and Table 3 indicate different propagation mechanisms because by using arrester, combustion energy will be absorbed by the arrester material. Thus, the propagation velocity of the flame is reduced. For the cases when the arrester was used, stable and non-stable detonations were not be observed. The deflagration phenomena can only be observed in the detonation quenching and detonation reinitiation in the initial pressure.

Table 3 Mechanism of the propagation of combustion wave with an arrester model

Deflagration wave propagation without the arrester model occurred at low initial pressures. This phenomenon was observed in the experiment at a pressure of 10 kPa, as shown in Figure 3a. Notably, the combustion wave propagation occurred at all observation points (i.e., P1, P2, and P3) under the deflagration wave condition. This is characterized by the propagation of the combustion wave several microseconds after the shock wave. In experiments conducted under this condition, the shock wave pressure increased approximately 23 times from the initial pressure. Meanwhile, the velocity in positions P₂ and P₃ was 1,786 m/s, which was smaller than the Chapman–Jouguet (CJ) theoretical velocity of 2,361 m/s.

Figure 3 Pressure and ion profiles of the combustion wave with at an initial pressure of 10 kPa: (a) without and (b) with an arrester model

The representation of the conditions of this phenomenon is shown in Figure 4a, i.e., the pressure profile of the combustion wave along the detonation test tube without an arrester model with an initial pressure of 20 kPa. These findings show that, at position P1, which was 1,900 mm from the spark plug, the combustion wave that could be observed was the detonation wave. Furthermore, this wave would propagate downstream toward positions P2 and P3. Figure 4a shows the combustion waves at positions P2 and P3 were detonation waves.