Influence of momentum ratio and its throttling method on spray characteristics of pintle injector

Abstract

The spray characteristics of a liquid-liquid pintle injector under different momentum ratios are investigated experimentally in this paper. Water is used as a simulant medium for both the fuel and the oxidizer. By increasing the mass flow rate of the oxidizer or reducing the mass flow rate of the fuel, the local momentum ratio is increased from 0.16 to 0.99, wherein the responding total momentum obtained by the former throttling method is relatively high due to the higher mass flow rate of the fluid. The outer and inner spray boundary, droplet size distribution and the velocity field are studied by high-speed camera and phase Doppler anemometry (PDA). It is indicated that the spray pattern is affected by the operating conditions directly. The spray pattern is divided into the solid cone and the hollow-solid cone, generally. Furthermore, the spray pattern influences the other spray characteristics. Under the same local momentum ratio with different throttling methods, the spray angle is almost consistent, while the spray boundary in the far field is wider under the higher total momentum. With the increase of the mass flow rate of the outer injector, a hollow structure is generated in the near field of the spray, and its range expands with the increase of the local momentum ratio. The value of SMD increases with the local momentum ratio increasing. Under the same local momentum ratio, the variation range of SMD is wider under the higher total momentum. The variation trend of SMD in the radial direction differs from the spray pattern, too. The SMD of the hollow-solid spray displays as an " N” shape along the radial direction, and reaches its peak at the outer boundary. By contrast, the SMD of the solid spray decreases slightly in the radial direction and varies on a small scale. The value of the resultant velocity is determined by the total momentum, and the curves of all the resultant/axial/radial velocity display as an inverted " V” in the radial direction. Nevertheless, the trend of axial velocity in the radial direction is mainly decreasing, and the increasing stage only exists at the central spray. However, the radial velocity undergoes a slight decrease or levels off directly after reaching the peak. The higher the local momentum ratio, the larger the radial velocity is, while the lower the axial velocity. In addition, the velocity field below the hollow field is dominated by the liquid film, which is explained by analyzing the impinging process of the neighboring cloaks in this paper.

Numerical Investigation on Spray Characteristics With Upstream Flow Pulsation of a Pintle Injector

“…In liquid rocket engines, the atomization of the liquid propellant can promote evaporation, mixing, and combustion. Since the 1980s, researchers from the United States (Dressler and Bauer, 2000;Gamertsfelder et al, 2020), South Korea (Son et al, 2015;Son et al, 2016a;Radhakrishnan et al, 2018), China (Zhang et al, 2014;Fang and Shen, 2017;Chen et al, 2019;Wang et al, 2020), Japan (Sakaki et al, 2015;, and other countries have carried out a lot of investigations on the spray characteristics of pintle injectors, mainly focusing on the angle and the breakup process of the spray, together with size, velocity, mixing features, and other aspects of the droplets.…”

“…Two different spray patterns were observed. Chen et al (2019) studied the spray boundary, droplet size distribution, and flow field characteristics under different momentum ratios and found that the spray characteristics were also affected by the local momentum ratio. Fang and Shen (2017) obtained the effects of the structure parameters on SMD, droplet size distribution uniformity index, and spray angle.…”

Effects of LOX Particle Diameter on Combustion Characteristics of a Gas-Liquid Pintle Rocket Engine

“…Besides, the coupling between the heat release rate and the combustion chamber acoustics occurs with the chamber acoustic natural frequencies when TMR is smaller than unity. Cheng et al [7,[25][26][27][28] researched the spray characteristics of pintle injector through cold tests and theoretically derived the prediction formula of its spray cone angle. Fang and Shen [29] adopted the D SMD obtained in cold tests as the initial condition for two-dimensional numerical simulations and studied the effects of various structural parameters on the combustion performance of the LOX/GCH 4 pintle rocket engine thoroughly.…”