Experimental Study On Temperature Change by Cavitation Accompanying Self-Pressurization of Propellant for Small Rocket Engines

Journal of Fluids Engineering ◽

10.1115/1.4051729 ◽

2021 ◽

Author(s):

Kazuki Yasuda ◽

Daisuke Nakata ◽

Masaharu Uchiumi

Keyword(s):

Saturated Vapor ◽

Temperature Drop ◽

Flow Characteristics ◽

Rocket Engines ◽

Discharge Process ◽

Fluid Temperature ◽

Hybrid Rocket ◽

Two Phase ◽

Liquid Rocket ◽

Pressurized Fluids

Abstract As a propellant for hybrid rocket engines using liquid oxidizer and solid fuel and for liquid rocket engines, the use of self-pressurized fluids such as nitrous oxide has become widespread. Since these fluids can be self-pressurized by their high saturated vapor pressure, the propulsion system becomes smaller and simpler. However, this self-pressurization generally forms a gas-liquid two-phase flow by flashing or cavitation. This flow is considered highly unsteady because the temperature and pressure greatly change with the discharge process. In this study, unsteady flow characteristics due to self-pressurization were experimentally obtained by conducting many cold flow tests with carbon dioxide as self-pressurizing fluids. As a result, it was clarified that the fluid temperature dropped about 10-15 K with the pressure drop due to feed line pressure loss during the discharge process. From these experimental results, we estimated the bubble growth and void fraction change that would satisfy the temperature drop. In this paper, the obtained test results and estimated temperature drop are reported.

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Fundamental Study on Injector Flow Characteristics of Self-Pressurizing Fluid for Small Rocket Engines

Volume 3A: Fluid Applications and Systems ◽

10.1115/ajkfluids2019-5625 ◽

2019 ◽

Author(s):

Kazuki Yasuda ◽

Daisuke Nakata ◽

Masaharu Uchiumi ◽

Kugo Okada ◽

Ryoji Imai

Keyword(s):

Nitrous Oxide ◽

Two Phase Flow ◽

Saturated Vapor ◽

Flow Characteristics ◽

Chamber Pressure ◽

Rocket Engines ◽

Phase Flow ◽

Two Phase ◽

Fundamental Study ◽

Upstream Pressure

Abstract Nitrous oxide (N2O) is a suitable propellant for small rocket engines (mostly kN class), and has been widely used in various countries given its high saturated vapor pressure (i.e., 6 MPa at 300 K), which enables self-pressurization. Because nitrous oxide exists with gas-liquid equilibrium in tanks, cavitation occurs when the pressure in the tanks and feed lines drops slightly, which easily forms a gas-liquid two-phase flow. Since accurately estimating the performance of rocket engines requires ascertaining the characteristics of their propellant flows, flow tests with self-pressurization using nitrous oxide were conducted, as were firing tests of hybrid rocket engines using nitrous oxide as a liquid oxidizer and acrylic as a solid fuel. This paper presets the results of those tests, along with findings obtained regarding the characteristics of the gas-liquid two-phase injector flow with self-pressurization. In the N2O flow test, the injector upstream pressure was approximately 1.5 MPa, while the injector downstream pressure was approximately 0.1 MPa. At 0.070, the ratio of upstream to downstream pressure of the injector was thus extremely large, which suggested that the gas-liquid two-phase flow was choked with the injector. By contrast, in the firing test with a chamber pressure of approximately 1.0 MPa and a thrust of approximately 650 N, the ratio of the injector downstream pressure (i.e., chamber pressure) and its upstream pressure was approximately 0.56. Although that ratio was relatively large, because the injector upstream pressure is relatively low (i.e., approximately 1.8 MPa) and the backpressure fluctuated due to combustion, it remains unclear whether the gas-liquid two-phase flow was choked.

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Study of Thermodynamic Effect On the Mechanism of Flashing Flow Under Pressurized Hot Water by a Homogeneous Model

Journal of Fluids Engineering ◽

10.1115/1.4051972 ◽

2021 ◽

Author(s):

Anh Dinh Le

Keyword(s):

Numerical Method ◽

Saturated Vapor ◽

Homogeneous Model ◽

Temperature Drop ◽

Numerical Data ◽

Hot Water ◽

Two Phase ◽

Suppression Effect ◽

Flow Parameters ◽

Thermodynamic Effect

Abstract The flashing flow in a Moby_Dick converging-diverging nozzle under pressurized hot water from 460.5 K to 483.5 K is simulated using a homogeneous compressible water-vapor two-phase flow model. The kinematic and thermodynamic mass transfer are accessed using the cavitation model based on the Hertz-Knudsen-Langmuir equation. Our simplified thermodynamic model is coupled with the governing equations to capture the phase-change heat transfer. This numerical method proved its reliability through a comparison with available experimental data of flow parameters inside the nozzle. Consequently, the present numerical method shows good potential for simulating the flashing flow under pressurized hot water conditions. The satisfying prediction of averaged flow parameters with a slight improvement compared to reference numerical data is reproduced. The results confirm a noticeable impact of the thermodynamic effect on the mechanism of flashing flow, resulting in a considerable decrease in the flow temperature and the saturated vapor pressure. The flashing non-equilibrium is significantly decreased, forcing the flashing flow to be classified as the usual cavitation behavior and better suited to homogeneous model. While the temperature drop is highly dependent on evaporation, the thermodynamic suppression is influenced by the condensation. The suppression effect, unobserved in water at a lower temperature in previous studies, is noticeable for the pressurized hot water flow characterized by the cavitation mechanism. The vapor void fraction decreased considerably in the radial and axial directions as the water temperature rose to 483.5 K in this study.

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Numerical Study of Cavitating Flow in Two-Phase LNG Expander

Volume 9: Oil and Gas Applications; Supercritical CO2 Power Cycles; Wind Energy ◽

10.1115/gt2016-56780 ◽

2016 ◽

Author(s):

Peng Song ◽

Jinju Sun ◽

Kaiqiang Li ◽

Ke Wang ◽

Changjiang Huo

Keyword(s):

Design Optimization ◽

Numerical Study ◽

Temperature Drop ◽

Flow Analysis ◽

Flow Characteristics ◽

Cavitating Flow ◽

Cavitation Model ◽

Two Phase ◽

Hydraulic Turbines ◽

Liquefaction Process

LNG expander is developed and used as a replacement of a J-T valve in liquefaction process of natural gas to reduce significantly the energy consumption in the LNG plant. Similar to conventional hydraulic turbines, the unexpected cavitation also occurs in the LNG expander. In the present study, cavitating flow in two-phase LNG expander is investigated. With the justified Rayleigh-Plesset cavitation model, cavitating flow characteristics is investigated for the LNG expander in the entire stage environment including an annular bend, nozzle ring, and radial inflow impeller. On the basis of cavitating flow analysis, a coaxial rotating exducer is developed and fitted downstream to the impeller, so as to reduce the cavitation in impeller and subsequently prevent impeller damage. The following are demonstrated: (1) without exducer, significant cavitating flow is encountered at the impeller trailing edge and also in half streamline-wise region, and they are resulted from the viscous dissipation and flow separation; (3) with exducer, the impeller cavitation has diminished entirely but it has occurred in the successive exducer; (3) a use of exducer enhances the energy conversion capability of the rotors, but reduces the overall temperature drop and efficiency of the expander; (4) the design optimization of exducer is required to suppress the exducer cavitation, which also needs to be incorporated with the impeller design to achieve a better match between rotor/stator, so as to maximize the design optimization benefits.

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Two-phase flow characteristics of liquid oxygen flow in low pressure liquid rocket engine

Cryogenics ◽

10.1016/j.cryogenics.2004.02.009 ◽

2004 ◽

Vol 44 (6-8) ◽

pp. 493-500 ◽

Cited By ~ 3

Author(s):

Namkyung Cho ◽

Seunghan Kim ◽

Youngmog Kim ◽

Sangkwon Jeong ◽

Jeheon Jung

Keyword(s):

Two Phase Flow ◽

Rocket Engine ◽

Flow Characteristics ◽

Low Pressure ◽

Oxygen Flow ◽

Liquid Oxygen ◽

Liquid Rocket Engine ◽

Phase Flow ◽

Two Phase ◽

Liquid Rocket

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Fundamental Study on Injector Flow Characteristics of Self-Pressurizing Fluid for Small Rocket Engines

Journal of Fluids Engineering ◽

10.1115/1.4048688 ◽

2020 ◽

Vol 143 (2) ◽

Author(s):

Kazuki Yasuda ◽

Daisuke Nakata ◽

Masaharu Uchiumi ◽

Kugo Okada ◽

Ryoji Imai

Keyword(s):

Nitrous Oxide ◽

Two Phase Flow ◽

Flow Characteristics ◽

Acoustic Oscillation ◽

Chamber Pressure ◽

Rocket Engines ◽

Phase Flow ◽

Two Phase ◽

Firing Test ◽

Flow Test

Abstract Nitrous oxide is a suitable propellant for rocket engines and has been widely used in various countries, given its high saturated vapor pressure, which enables self-pressurization. Because nitrous oxide is in a state of vapor–liquid equilibrium in tanks, it is easy to form a gas–liquid two-phase flow by cavitation in feed line. Since accurately estimating the performance of rocket engines requires evaluating the characteristics of propellant flows, tests reported in this paper were conducted using hybrid rocket engines under three conditions: cold flow test, hot firing test at low back pressure, and hot firing test at high back pressure. With consideration to the subcooling degrees, nitrous oxide may be in an unsteady superheated state in the upstream flow of the injector. In a comparison of the pressure ratios between the injector in each test condition, it is observed that a critical two-phase flow was formed in the injector in the cold flow test and in the low backpressure firing test. In the high backpressure hot firing test, the injector flow may be choked, but the large oscillations were observed in chamber pressure and thrust. According to the FFT analysis results, these oscillations were caused by chugging and acoustic oscillation. In light of these experimental results, it is suggested that when the chamber pressure fluctuates due to combustion instability such as chugging and acoustic oscillation, it may affect the injector flow characteristics and the critical two-phase flow.

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