Oxygen Mass Flow Research Articles

A semi-empirical model for online real-time control of NOX generation in diesel engines

Diesel NOX emission control is the main control content of diesel engines. Real-time high-precision NOX emission prediction model is the basic guarantee for (1) Diesel combustion management, (2) SCR after-treatment control, (3) OBD system. Existing models that rely exclusively on physical processes or data-driven artificial intelligence models fail to meet real-time requirements, while MAP look-up table-based models are poorly adapted and require extensive experiments for calibration. In this study, a new semi-empirical model for NOX emission prediction was developed, and the variables of the model were identified as exhaust temperature, engine speed, injected fuel mass flow rate, air intake mass flow rate, and exhaust oxygen mass flow rate, taking into account the mechanism of NOX generation in diesel engines as well as the requirement of real-time and direct measurability of the variables for on-line control. The influence of each variable on NOX was analyzed, the model structure of the NOX prediction model was determined, and the parameters of the prediction model were identified by least squares. The model is applied to real operating vehicles for validation and compared with a previous semiempirical model taken from the literature, and the results show that the overall accuracy of the proposed model is improved. Finally, the effect of variable uncertainty on the proposed model was assessed and it was found that the relative uncertainty in predicting NOX emissions ranged between 0 and 8% for sensor accuracies of [Formula: see text] and [Formula: see text] for exhaust temperature and intake air mass flow, respectively, suggesting that the sensor accuracy has a significant effect on the uncertainty of the model.

Investigation on spray and flame stabilization of a LOX/methane swirl coaxial injector

Variable-thrust cryogenic propellant rocket engines are gaining significant research interest in space exploration. However, low-frequency unstable combustion is still a challenging scenario, especially in fuel-rich preburner and low-thrust operating conditions of deep variable thrust. To deeply understand the mechanism of low-frequency unstable combustion, chemiluminescence images of CH* and background light images of the spray were obtained synchronously by chemiluminescence imaging and laser background light imaging, respectively. Both the spray and flame stabilization of liquid oxygen/methane swirl coaxial injector were studied through the continuous regulation of liquid oxygen mass flow rate. The results showed that low-frequency unstable combustion occur in both the start-up stage and the throttled stage under the fuel-rich condition at a frequency of 39.1∼48.1 Hz and an amplitude of 30% of the average combustor pressure. It is found that the two-phase flow instability of liquid oxygen is likely to induce spray and flame instability, resulting in low-frequency unstable combustion. The dimension subcooling degree of liquid oxygen is an important factor affecting unstable combustion. When the dimensionless subcooling degree is larger than 0.7, the low-frequency unstable combustion is suppressed. On the other hand, as the mixing ratio decreases, the flame oscillation mode gradually transforms from the longitudinal oscillation mode to contraction/expansion mode. Flame filling up and flashback processes can be observed in both flame oscillation modes, and the entropy coupling mechanism of the oscillation mode is explained in detail. Furthermore, an oscillation period is determined to include four processes: propellants filling up and flame liftoff; heat release of the combustion products and entropy disturbance; acceleration of the entropy wave through the nozzle creating an acoustic disturbance; and flame flashback, in which the heat release time of combustion products and entropy disturbance is the longest.

Titanium oxynitride thin films by the reactive sputtering process with an independent pulsing of O2 and N2 gases

Titanium oxynitride thin films are deposited by DC reactive magnetron sputtering. A pure titanium target is sputtered in a reactive atmosphere composed of argon, oxygen and nitrogen gases. The oxygen mass flow rate as well as that of the nitrogen gas are both pulsed during the deposition time using an independent and rectangular signal for each reactive gas. A constant pulsing period T = 45 s is applied for both reactive gases and a delay time δ of 34 s between N2 and O2 injection times is set for all depositions. Oxygen and nitrogen duty cycles are systematically and independently changed from 0 to 100 % of their pulsing period. From real time measurements of the Ti target potential and total sputtering pressure, it is shown that the reactive process alternates between oxidized, nitrided and elemental sputtering modes as a function of the oxygen and nitrogen injection times. The full poisoning of the Ti target surface by oxygen and/or nitrogen can be avoided for some given ranges of O2 and N2 duty cycles. Deposition rates of titanium oxynitride films are substantially enhanced and can be adjusted between that of pure Ti and TiN films with a gradual transition of their electrical conductivity and optical transmittance in the visible range. These results support that titanium oxynitride compounds exhibiting absorbent to transparent behaviors can be precisely sputter-deposited by means of a two reactive gases pulsing process.

Numerical investigation on unstable oscillation of oxygen jet condensation in cryogenic liquid rocket

Oxygen jet condensation always occurs with intense unstable oscillation in the cryogenic delivery pipe of a space launch vehicle. This phenomenon threatens the safety of the propulsion pipeline. It is essential to explore the transient physical features of oxygen jet condensation precisely, including the spectrum of pressure oscillation. Aiming at a deeper understanding of the thermal hydraulic characteristic of oxygen jet condensation, abundant simulations are carried out using a modified phase change method. In this model, the height function method is introduced to capture the interfacial curvature to reveal the mechanism of periodic fluctuation. The simulation proves that three typical flow patterns are found at variant operating conditions in oxygen jet condensation: chugging, oscillation, and swinging. The condensation regime diagram is summarized according to the flow pattern distribution. The chugging flow, along with the phenomenon of liquid oxygen sucked-back flow, shows the most intense pressure oscillation with a maximum amplitude of 133 kPa. In the oscillation flow, the oxygen vapor plume shrinks periodically with a low frequency of about 10 Hz. The swinging flow is a stable flow pattern with a slight pulsation of oxygen vapor plume wake. Its amplitude of pressure oscillation is approximately 1–3 kPa. The influence of liquid oxygen mass flow rate and subcooling on the unstable characteristic is also obtained. These findings offer ample theoretical direction for the development of the space launch vehicle.

Throttling simulation and control of liquid oxygen/liquid methane rocket engine pressurized by the electric pump

This article presented simulation and control of a liquid oxygen/liquid methane variable thrust rocket engine pressurized by the electric pump in the throttling process. To get a proper injection pressure drop, the variation of the injection area was investigated and determined. In the control scheme, the combustion pressure and mixture ratio were the targets. To simplify the control scheme, the pressure and mixture ratio were correlated to the oxygen mass flow rate and methane mass flow rate, respectively. By controlling the propellant mass flow rate, the target engine thrust was reached. In addition, the influence of mass flow rate measurement points on the control effect was analyzed. The simulation results showed that the designed controller can reduce the overshoot of the critical engine parameters. Therefore, the maximum temperature of the thrust chamber wall after the regenerative cooling was decreased. Consequently, the thrust control errors were within 3% except for the points where the thrust changed suddenly, which can meet the mission requirements.

Transition from smouldering to flaming combustion of pine needle fuel beds under natural convection

Smouldering transition to flaming combustion (StF) of forest fuels can rekindle wildfires, possibly causing the suppression effort to be useless or the firefighters to be stuck in danger. However, the StF mechanism of forest fuels remains to be elucidated. In this work, the StF of pine needle fuel beds with different bulk densities was investigated experimentally. Two modes of transition are identified: Middle- and Trailing-StF, which occur at the middle and trailing edges of the char region in the fuel bed, respectively. The conditions for the occurrence of both modes include (1) the length of the char region exceeding a critical value and (2) a hot glowing area (strong secondary char oxidation area) appearing before StF. An overhang structure is also necessary to induce Trailing-StF. These conditions are interpreted in terms of the permeability of fuel beds, which affects the diffusion and convection supply of oxygen for smouldering. Middle-StF occurs due to sufficient oxygen diffusion and convection supply in the middle of the char region with large pores. In Trailing-StF, the overhang structure forms a region with high permeability, which significantly enhances the convection mass flow rate of oxygen and provides a favorable space for the accumulation of mixed combustible gases. The oxygen mass flow rate leading to both StF modes is in the order of 10−2 g/s.

Thermal and Air Management of an Open Cathode Proton Exchange Membrane Fuel Cell Using Sliding Mode Control

Abstract The paper presents a simplified nonlinear model for an open cathode proton exchange membrane fuel cell (PEMFC) and its control using three different control strategies. The model presented uses four state variables. The mass flow of oxygen, hydrogen flow, water flow, and temperature were taken to be the critical dynamics in the system. The unknown parameters were estimated using the experimental data of a 1.2 kW PEMFC. The simplified model showed good agreement with experimental results. Control schemes were implemented to control the stack temperature and the oxygen excess ratio of the PEMFC. The proportional (P) and proportional–integral (PI) control performed well but had a poorer response compared to the sliding mode control (SMC) scheme. The study of the different control schemes reveals the dangers of solely controlling either the oxygen excess ratio or the temperature. Results show that the best control is achieved when the excess ratio is controlled together with the reference temperature. The study also compares the parasitic losses from the fans caused by the different controllers. Overall, the results provide a good insight into designing a robust control system for an open cathode PEMFC for faster response and greater durability of the PEMFC.

Experimental Investigation of a Swirling-Oxidizer-Flow-Type Hybrid Rocket Engine Using Low-Melting-Point Thermoplastic Fuel and Oxygen

Hybrid rockets are safe and inexpensive; however, boundary-layer combustion poses a problem in achieving a fuel regression rate equivalent to that of solid propellants. The fundamental combustion conditions, such as the fuel regression rate of LT421, a paraffin-based low-melting-point thermoplastic fuel, were investigated using a swirling-flow combustion method. Firing tests were conducted using the oxygen mass flow rate and burn time parameters. The LT fuel exhibited an ignition delay compared to polypropylene, and the pressure increased slowly relative to the thrust. The combustion pressure increased or remained constant with time, suggesting that the fuel regression rate was more dependent on the oxygen mass flow rate than the oxidizer mass flux. The shear force generated in the grain owing to the swirling flow caused fuel-grain separation when the oxygen mass flow rate exceeded 100 g/s. Fuel-grain separation was prevented by modifying the case geometry. The maximum fuel regression rate obtained in the tests was 4.88 mm/s at an oxygen mass flow rate of 190 g/s and mass flux of 72.4 kg/(m2s), which was four times higher than that of polypropylene at the same oxidizer mass flux. The fuel regression rate correlation was obtained using the oxygen mass-flow-rate-based parameter, although further modification was necessary to apply this correlation when the burning time was varied.

The effects of flow field design on PEMFC

The flow field design plays a crucial role in the performance of proton exchange membrane fuel cells (PEMFCs). An efficient flow field design enhances electrochemical reactions in catalyst layers and facilitates the water removal process at the cathode. This study evaluates two PEMFC designs, rectangular and semicircle baffle flow fields, using computational fluid dynamics modeling. The models incorporate mass, heat and energy transport, electrode kinetics, and potential fields in PEMFCs. The research analyzes the hydrogen and oxygen mass flow rates and water distributions in PEMFCs at operating voltages of 0.3–1 V to determine the effect of the flow field design on performance. According to the results it is clear that flow field design has an important influence on PEMFC power density and performance. The calculated power density at 0.3 V and at 80°C for semicircle and rectangular baffle flow field PEMFCs respectively are 0.37 and 0.23 W cm−2, which indicates that PEMFC with semicircle baffle flow field has better performance in this study.

Simulation of a solid-phase oxygen control scheme in lead-bismuth eutectic system

It is known that solid-phase oxygen control scheme is one of the important methods to solve the corrosion problem when we choose lead–bismuth eutectic (LBE) as coolant in lead-cooled fast reactor (LFR) or Accelerator Driven System (ADS). The mass-exchanger (MX), a porous chamber filled with mechanically stable lead oxide (PbO spheroids), is the key component of solid-phase oxygen control. In order to study the characteristics of oxygen mass transfer, pressure drop, flow field and oxygen concentration field in MX, a randomly packed bed model is established using DEM method. The fluid domain is meshed with computational fluid dynamics (CFD) code STAR-CCM +. The particle–particle and wall–particle contact points are modified with short cylinder bridges to improve the cell qualities. The mass transfer boundary layer theory is applied to explain the oxygen supply process of PbO sphere dissolution to LBE. The results of the average porosity, radial porosity distribution and pressure drop match the previous literature pretty well. The CFD results related to Sherwood number (Sh) are validated by CRAFT experimental data with an acceptable error. The law of oxygen transfer and distribution is obtained by studying the CFD contours and the spatial distribution of oxygen concentration and velocity data. The temperature dependence and velocity dependence of Sherwood number are obtained through multiple linear regression processing of CFD data. Finally, the effects of different temperatures and mass flow rates on oxygen concentration and pressure drop are evaluated to determine the suitable operating domain for MX.

Experimental study on design and operational performance of solar-powered venturi aeration system developed for aquaculture – A semi-floating prototype

Venturi-type injectors have been used usually due to the practical use and modular design that allows for quick configuration, ready-to-use, and low-cost solutions in the last years. This study aims to design a solar-powered venturi aeration system (SVAS) and determine its flow characteristics, standard, and real-time operational performance parameters. SVAS has a design providing the maximum vacuum and air velocity at air inlets and allowing for all technical measurements. Moreover, a solar-powered experimental apparatus having a weather station, a pool station, and a data logger station was constructed. Experiments were carried out using a plastic pool with a capacity of 4000 L, a diameter of 3 m and a depth of 0.75 m, four venturi injectors, and a submersible pump of 0.3 kW operated at the constant water flow regime of 4.1 m3 h-1. According to flow tests, the oxygen mass flow rates ranged from 2.77 to 2.84 kg h−1. The specific energy consumption values are 263.2 kJ per cubic meter for water flow and 380 kJ per kg for oxygen transfer.Standard performance experiments were repeated four times. The maximum overall oxygen mass transfer coefficient obtained during the experiments was 5.58 h−1. The maximum values of standard oxygen transfer rate (SOTR), standard aeration efficiency (SAE), and standard oxygen transfer efficiency (SOTE) were 0.206 kgO2 h−1, 0.681 kgO2 kWh−1, and 7.32%, respectively. The pool conditions were simulated using de-oxygenation and mixing systems to determine the operational performance. For simulation experiments, six procedures and two processes were applied. Throughout operational experiments of four days, real-time dissolved oxygen levels fluctuated between 1.05 mg L−1 and 6.65 mg L−1. The maximum performance values were 0.143 kgO2 h−1 for the actual oxygen-transfer rate, 0.474 kgO2 kWh−1 for aeration efficiency, and 5.1% for oxygen transfer efficiency.

Thermodynamic Characterization of Grease Oxidation–Thermal Stability via Pressure Differential Scanning Calorimetry

This study investigates and characterizes, via thermodynamic laws, a widely employed standard for measuring oxidation-thermal stability of lubricating greases—ASTM 5483—based on first-order chemical kinetics, using pressure differential scanning calorimetry (PDSC). Steps and active mechanisms in the controlled test are analyzed and modeled using energy and entropy transformations. Applying the degradation-entropy generation (DEG) theorem, oxidation induction time is related to accumulated oxidation entropy and entropy transfer by mass flow to obtain characteristic degradation coefficients. These DEG coefficients are calibrated using available measured data from the literature and subsequently used to predict induction times at various temperatures. DEG elements—trajectories, planes, and domain—presented here consistently characterized all greases studied. Results show that the high-pressure entropy transfer by oxygen mass flow in the final step of the ASTM 5483 procedure is the primary contributor to oxidation induction time, verifying the significance of this process in accelerating antioxidant depletion, which would otherwise take months to years under atmospheric conditions. DEG-predicted induction times at various temperatures are compared to induction times predicted by the first-order chemical kinetics model, revealing a close match. The new DEG model is also herein used to predict induction times at atmospheric pressure, whereas the first-order kinetics model is independent of pressure and limited to the specific conditions in ASTM 5483. The DEG approach has useful implications for the accelerated and unaccelerated evaluation of grease oxidation stability and grease useful life.

The Regression Rate-Based Preliminary Engineering Design of Hybrid Rocket Combustion System

The paper presents a useful engineering model for the design of preliminary hybrid rocket engines. This model involves the experimentally obtained equation regarding the speed of the burning interface between solid fuel and gaseous phase, called the regression rate. This regression rate characterizes the mass rate of the burning fuel and additionally the mass rate of the oxidizer through the imposed ratio of these mass rates during combustion. The preliminary design is applied to combustion using pure HTPB and gaseous oxygen and was developed for three cases, constant regression rate, constant oxygen mass flow rate and constant O/F (ratio of mass rates of oxygen and of fuel). The design evaluates the initial fuel port geometry, the initial mass of fuel and oxygen, the combustion time, the thrust at sea level, and the time-dependent functions of regression rate, of fuel and oxygen mass rates, and of thrust. It was assumed that the regression rate formula applies at any time of combustion. These evaluations can also be applied for other fuel/oxygen couples by knowing the correct formula for the regression rate.

Experimental investigation of a water electrolysis Hall effect thruster

We conceptualise an electric propulsion system in which water is utilised as a propellant for a Hall effect thruster using in situ electrolysis. By supplying the generated oxygen to the thruster anode and the hydrogen to the neutralising cathode, poisoning of the cathode emitters is mitigated. Not only does such a system benefit from the low cost, high storability and in situ resource utilisation potential of water, but synergies with water electrolysis chemical propulsion systems allow for multi-mode chemical-electrical propulsion architectures. The water electrolysis Hall effect thruster (WET-HET) has been optimised to operate on oxygen as a proof of this concept. We perform direct thrust measurements on the WET-HET using a hanging pendulum thrust balance. The thruster was operated using oxygen mass flow rates ranging from 0.96 mgs−1 to 1.85 mgs−1, and discharge powers ranging from 490 W to 2880 W. The cathode used in this test was supplied with krypton rather than hydrogen, due to laboratory restrictions preventing compressed hydrogen and oxygen cylinders being used in close proximity. Two channel wall materials were investigated — alumina and boron nitride. It was found that the wall material had a significant impact on the thrust, with an increase of approximately 40% for boron nitride. Reconfiguration of the magnetic components of the WET-HET allows us to alter the thickness of the magnetised region within the thruster channel. We test the device in three different magnetic configurations, ranging from a traditionally thin magnetic region to complete magnetisation of the discharge channel. We find that increasing the thickness of the magnetic region reduces thrust, specific impulse, and thrust efficiency of the device. We assess the change in performance as we change the discharge channel depth of the thruster. The best performance was achieved with the shallowest channel of depth 35 mm. We find the that thrust, specific impulse and anode thrust efficiency increases linearly with power for all configurations with no obvious plateau. Greatest specific impulse and efficiency was found when mass flow was lowest. Although discharge voltage increases linearly with magnetic field strength, thrust, specific impulse and efficiency peaks at 480 Gauss. The greatest thrust measured was 38.63 ± 0.25 mN, with a maximum specific impulse of 4112 ± 36 s and a maximum anode thrust efficiency of 15.50 ± 0.27%.

Multi-hollow surface dielectric barrier discharge: an ozone generator with flexible performance and supreme efficiency

This contribution investigates the effects of duty cycle and mass flow of synthetic air and oxygen on the efficiency of ozone generation in multi-hollow surface dielectric barrier discharge (MSDBD). It discloses that the efficiency of ozone generation in MSDBD is significantly higher compared with standard coplanar DBD, surface DBD and volume DBDs. Ozone production yield reached 205.5 ± 29.1 g (kW h)−1 (40% duty cycle, 8 slm) and 413.91 ± 58.7 g (kW h)−1 (100% duty cycle, 8 slm) at an energy cost of 8.7 and 4.3 eV/molecule for synthetic air and oxygen, respectively. Such high ozone yields arose out of the intrinsic characteristics of MSDBD ceramics, which were efficiently cooled by the flow of the working gas. The amplitude modulation of low-frequency 5 kHz high-voltage sine waveforms facilitates controlled O3 production at a nearly constant rate of yield. Since the correct evaluation of ozone production yield requires precise determination of the discharge power, the concentration of ozone and working gas-flow, considerable attention was paid to measurements of these parameters. It is confirmed and experimentally demonstrated herein that correct determination of discharge power lies with Lissajous figure methods, while the determination of power through the direct integration of product u(t)i(t), where i(t) is measured by Pearson current probe, leads to systematically lower values of calculated power with consequent overestimation of the ozone production yield. The correct determination of discharge power is clearly the key to the proper calculation of ozone production yield and efficiency. Under the DBD discharge conditions presented herein, ozone production yield and efficiency achieved figures as high as 19.5% and 35.2% of theoretical limits recently established for air and oxygen, respectively.

Numerical Investigation on Coal Combustion in Ultralow CO2 Blast Furnace: Effect of Oxygen Temperature

The cooling effect of room-temperature oxygen in oxygen blast furnaces with top gas recycling (TGR-OBF) delays the coal combustion process. To further explore the oxygen–coal combustion mechanism and intensify coal combustion in TGR-OBF, the effect of oxygen temperature on coal combustion was investigated using computational fluid dynamics (CFD). A three-dimensional model was developed to simulate the lance–blowpipe–tuyere–raceway of TGR-OBF. The effect of oxygen temperature at the same oxygen velocity and mass flow on coal combustion was investigated. Results showed the cooling effect of room-temperature oxygen was weakened, and the coal burnout was greatly increased with the increase in oxygen temperature. In particular, the coal burnout increased from 21.64% to 81.98% at the same oxygen velocity when the oxygen temperature increased from 300 to 500 K. The results provide useful reference for the development of TGR-OBF and coal combustion technology.

Hierarchical model predictive control via deep learning vehicle speed predictions for oxygen stoichiometry regulation of fuel cells

Fuel cells are a promising solution for increasing driving range of electric vehicles. To guarantee the high efficiency and stable operation of fuel cells, the effective regulation of oxygen and hydrogen reactants is needed. During varied driving conditions, in which the drastic current demand changes may result in insufficient reactant, the fuel cell can even be damaged. In this paper, a hierarchical model predictive control (HMPC) strategy is proposed based on the deep learning for vehicle speed predictions. Speed variation predictions are considered by the MPC to regulate the air supply system and preventing oxygen starvation in the fuel cell stack. The problems of fuel cell oxygen stoichiometry control are, first, stated with the preliminary energy management description as well as with the limitations of the traditional MPC. The deep learning Back Propagation (BP) neural network was then designed as the first-level predictor to forecast the vehicle speed by training with integrated driving cycles, and predict the fuel cell current based on its cathode flow model. Subsequently, the second-level MPC used the current disturbance prediction and filling is introduced to regulate the oxygen mass flow. The simulation results for the MANHATTAN drive cycle demonstrated that the root mean square error (RMSE) for speed predictions was less than 1 km/h. Compared with the conventional MPC, HMPC offers better robustness in the face of influence from current changes induced by speed-variations, and the RMSE of the oxygen stoichiometry control was decreased by 63.37%.

Reconstructed Ballistic Data Versus Wax Regression-Rate Intrusive Measurement in a Hybrid Rocket

Burning tests of a laboratory-scale hybrid rocket engine were carried out with gaseous oxygen and a microcrystalline-wax-based fuel to look into the feasibility of using an intrusive resistor-based sensor for measuring the fuel regression rate. This initial screening was driven by the need for real-time control of the oxidizer-to-fuel ratio in altering-intensity swirling-flow-type hybrid rocket engines aiming at performance optimization. A traditional ballistic reconstruction technique was critically revised in order to build up a framework for comparison with the measured data; with the measured aft-chamber pressure and oxygen mass flow rate time histories, the fuel regression rate and port diameter were reconstructed over the firing by estimating the combustion efficiency with the constraint that calculated and measured fuel mass consumed are equal. This technique invariably suffers from the issue of presenting multiple solutions for the fuel mass flow rate in the proximity of the optimum mixture ratio, for which a novel variable-efficiency approach is proposed. Reconstructed data show that regression rate is nearly constant in each firing, yielding dependence upon the port diameter other than the mass flux. Resistor-sensor raw data displayed large deviation from the ballistic results for the slower burning rate of the sensor support. A detailed analysis is presented.

Analysis of Equivalence Ratio in an Oxygen Acetylene Mixture

The paper presents an exclusive approach to analyze the oxygen and acetylene mixture in a Pulse Detonation Engine setup at PEC. The experiment was carried out by varying the amount of mass flow of acetylene and oxygen into the tube at different pressures in the settling chamber. The equivalence ratio of the acetylene-oxygen mixture with respect to the valve opening time of acetylene and oxygen was plotted. The analysis of equivalence ratio also defines the procedure which involved the cycle of valves and pressure supply to attain different values of filling fraction of the tube. The results experimentally predicted the feasible range of operation at different pressures in the settling chamber of the pulse detonation engine.

Flame oscillation characteristics in a kerosene fueled dual mode combustor equipped with thin strut flameholder

Flame oscillation characteristics in a strut-equipped dual mode combustor fueled with liquid kerosene were observed and discussed in this paper. A series of experiments and numerical simulations were carried out in the combustor both in lower inflow enthalpy condition (Ma = 2.0) and in higher inflow enthalpy condition (Ma = 2.8). The methods of high-speed photography and pressure measurement were used to record the basic data, and based on the basic data, the variation of flame area and the distribution law of wall pressure in different experimental conditions were analyzed to get the flame oscillation characteristics. Results indicated that the phenomenon of flame oscillation was caused by the variation of pilot flame strength and the adverse pressure gradient near the combustion region. Flame oscillation was distinguished into different status according to oscillation frequency and oscillation amplitude, and both the mass flow of oxygen and equivalence ratio could make a deep influence on the flame oscillation status. Flame oscillation characteristics were also closely related to the flowing state, and the difference of flame propagation process in supersonic and subsonic flowing conditions resulted in the distinction of flame oscillation characteristics. With the investigations in this paper, a depth understanding on flame oscillation in the dual mode combustor is achieved.