High-pressure Combustion Gases Research Articles

Oxidation Behavior of Atmospheric Plasma Sprayed NiAl Coating at High Pressure Oxygen Atmosphere

The high-temperature and high-pressure oxygen-rich combustion gases often cause the high temperature gas conduit in rocket engine to suffer severe oxidation, resulting in a reduced service life. The present study deposited a dense NiAl coating on GH4202 superalloy using atmospheric plasma spraying and investigated its oxidation behavior in a high temperature and high-pressure oxygen atmosphere. The results showed that the NiAl coating presented excellent bonding with the superalloy substrate throughout tests. The uncoated GH4202 substrate was severely oxidized during high pressure oxygen atmosphere. It was found that only a continuous very thin Al2O3 oxide scale evolved on the NiAl coating surface and no oxidation was observed at the interface between the NiAl coating and GH4202 substrate. Moreover, no significant inner oxidation occurred to NiAl coating. Therefore, the present APS NiAl coating can provide effective protection of superalloy from oxidation at high pressure oxygen combustion gas atmosphere.

Ultrafast-laser-absorption spectroscopy in the mid-infrared for single-shot, calibration-free temperature and species measurements in low- and high-pressure combustion gases.

This manuscript presents an ultrafast-laser-absorption-spectroscopy (ULAS) diagnostic capable of providing calibration-free, single-shot measurements of temperature and CO at 5 kHz in combustion gases at low and high pressures. Additionally, this diagnostic was extended to provide 1D, single-shot measurements of temperature and CO in a propellant flame. A detailed description of the spectral-fitting routine, data-processing procedures, and determination of the instrument response function are also presented. The accuracy of the diagnostic was validated at 1000 K and pressures up to 40 bar in a heated-gas cell before being applied to characterize the spatiotemporal evolution of temperature and CO in AP-HTPB and AP-HTPB-aluminum propellant flames at pressures between 1 and 40 bar. The results presented here demonstrate that ULAS in the mid-IR can provide high-fidelity, calibration-free measurements of gas properties with sub-nanosecond time resolution in harsh, high-pressure combustion environments representative of rocket motors.

Numerical and experimental study on high-speed hydrogen–oxygen combustion gas flow and aerodynamic heating characteristics

The need to increase the payload capacity of the rockets motivates the development of high-power rocket engines. For a chemical propulsion system, this results in an increasing thermal load on the structure, especially the combustion chamber and nozzle must be able to withstand the extreme thermal load caused by high-temperature and high-pressure combustion gas. In order to protect the structure from the effect of increasing heat flux, it is necessary to counteract such effect with more advanced thermal management technology. This requires us to accurately predict the aerodynamic heating of the structure by high-temperature and high-speed combustion gas. In this study, a high-temperature combustion gas tunnel developed in the laboratory is used to produce high-speed combustion gas. Combined with the results of numerical calculation, the flow and aerodynamic heating characteristics of air and hydrogen–oxygen combustion gas under the same total temperature and pressure are analyzed and compared. The comparison revealed that the combustion gas flow in the nozzle has higher static temperature, velocity, and smaller Mach number. When the combustion gas flows around the sphere, the shock standoff distance and stagnation pressure are smaller than those of air, and the wall heat flux is much larger than that of air. The active chemical reaction in the combustion gas makes the aerodynamic heating of the structure more severe. Finally, through the analysis of a large amount of data, a semi-empirical formula for the heat flux of the stagnation point heated by a high-speed hydrogen and oxygen equivalent ratio combustion gas is obtained.

Fatigue failure and launch safety assessment of gun barrel

Hundreds or thousands of projectiles have been fired through a gun barrel. Catastrophic fatigue failure of gun barrel due to cyclic loadings by the stresses induced by the combination of high pressure and temperature combustion gas, and projectile with the rotating band interaction with the bore surface, has not yet been understood. In this paper, laboratory hydraulic fatigue tests on simulated gun barrel were performed on MTS Land. The experimental results show that there is an inherent relation between crack propagation in thick-walled tube and the external surface hoop and axial strains. This fact suggests that fatigue failure of gun barrel should be likely prevented by monitoring the external surface strains of the gun barrel and stopping continued firing before a major crack growing up to the critical size.

Damage and fracture of gun barrel under wear-fatigue interaction

Gun, projectile and propellant are three fundamental components of a launching system. Generally, a barrel has to be condemned after a number of rounds have been fired. During the total useful life of gun barrel, it bears severe damage induced from erosion by high pressure and high temperature propellant combustion gas, and wear due to high speed friction between projectile and gun bore. Meanwhile, the gun barrel undergoes a dynamic loading of gas pressure, mechanical stress and thermal stress when firing a round. Thousands of firing cycles lead to gun barrel fatigue. Interaction of wear, including erosion, and fatigue damages the gun barrel and eventually the gun will become inaccurate because of wearing away gun bore materials. However, a gun barrel will fracture in a sudden manner because of fatigue. It is found that microcracks form on the bore surface after only a few rounds have been fired, which lays the foundation for growth and propagation of cracks under fatigue loading. In this paper, laboratory hydraulic fatigue tests were carried out on a tube with pre-machined crack on its inner surface by using an MTS 809. Strain gauges were adhered to the outer surface of the tube to monitor strain during testing process. The hydraulic oil pressure was measured by a pressure sensor. The experimental results show that there are three stages of outer surface strain variation, namely stable increase, fast increase and abrupt increase, which corresponds to the history of crack evolution. Crack grew stably in the initial stage under cycle of loading and a major crack is gradually formed. When the major crack size reaches a certain value, the propagation velocity of crack is accelerated fast and the critical size is reached in a short time. Eventually the tube fractured suddenly. The experimental findings will help us to gain new insight into the physical mechanism of fatigue and fracture of gun barrel and provide a possible method to evaluate health of gun barrel in service.

Cylinder Head Gasket Fretting Simulation for High Horse Power Engine

<div class="section abstract"><div class="htmlview paragraph">The head gasket of an internal combustion engine acts as a critical seal between its cylinder block and heads. Typically, and ideally, a high horse power engine head gasket will be composed of elastomer fluid sealing elements in a carrier and combustion seal body composed of aluminum, brass, carbon steel, copper, nickel, and/or stainless steel etc. The head gaskets purpose is to seal high pressure combustion gases, coolant, and oil and to ensure no leakage of gases or fluids out of the block to head joint.</div><div class="htmlview paragraph">Three major failure modes [<span class="xref">1</span>] for cylinder head gasket joint are; 1. Fluid or gas leakage due to low sealing pressure. 2. Head gasket (bead) cracking due to high gap alternation and 3. Gasket scrubbing/fretting due to pressure and temperature fluctuations causing relative movement in the joint. During engine operation, the head gasket design should be robust enough to prevent all failure modes and provide acceptable performance. Sealing analysis method to address low sealing pressure failure mode is well developed and common within the industry. This paper is focused on the development and utilization of an analytical method for the 3<sup>rd</sup> failure mode mentioned above i.e., scrubbing/fretting. Single layer metal gasket is considered during the scope of mentioned method. Single layer metal gasket gets locally yielded due to the design feature provided on the cylinder liner, called as bite ring.</div><div class="htmlview paragraph">During the scope of work, head gasket fretting mechanism is investigated. Based on the understanding of the fundamental fretting mechanism, considering Ruiz model [<span class="xref">2</span>], an analysis procedure is developed and finite element analysis results are correlated with actual failures and measured data. Finite element analysis results shows very good correlation in terms of relative sliding magnitude and failure location prediction. Commercial software ANSYS is used here. Actual gasket crushing is simulated by using 3D solid elements with non-linear material and geometric non linearity captured.</div></div>

Failure simulation of connecting rods without pistons using finite element method

The combustion of fuel takes place inside the cylinder with the oxygen of the air, producing a very high-pressure combustion gas. The combustion gas does work on the piston and then passes through the connecting rod to the crankshaft. The reciprocating translational motion of the piston may damage the connecting rod. A simulation using ANSYS was performed on each of the three connecting rod materials. Results showed that the maximum deformation occurred in the connecting rod made of structural steel, aluminium alloy, and titanium alloy was 0.239 mm, 0.672 mm, and 0.496 mm, respectively.

유한요소 해석을 통한 열 차폐 코팅의 열구배 피로 특성 평가

A gas turbine is a power plant unit that converts thermal energy into rotational energy by rotating a blade using hightemperature and high-pressure combustion gas. A gas turbine blade is directly exposed to a high-temperature flame. Various studies have aimed to improve the durability of the blade in harsh conditions. One proposes coating the blade with a thermal barrier to protect it from the flame, using a ceramic material with better thermal insulation. Another proposes using internal cooling, by creating an air flow path inside the blade to lower its temperature. Because both these techniques create a thermal gradient in the cross section of the blade, they amplify the difference in thermal expansion, thereby producing thermal stress in the blade and the thermal barrier coating. This study investigates the internal cooling effect on thermal gradient fatigue by using finite element analysis.

The interaction between multiple high pressure combustion gas jets and water in a water-filled vessel

A static experimental system based on the background of the underwater gun firing process is designed to simulate the expansion of conical-distributed multiple gas jets in a water-filled vessel. The gas is generated from the gunpowder combustion and injected into water through five orifices on a mock bullet. A high-speed digital camera is taken in experiment to record such expansion and the Euler-Euler multiphase model is utilized in simulation to describe the gas-liquid flow. Results show that the contraction of Taylor cavity in liquid and the gas-liquid entrainment both affect the shock structure in gas. The expansion zone near the orifice shrinks and the gas speed downs when the central gas jet has a contraction, but lateral jets have no contractions due to the obstruction from the wall. The contraction has a greater impact on the shock structure than the gas-liquid entrainment and occurs earlier under a higher injection pressure.

Thermo-mechanical analysis of first-stage-adjustment thruster propelled by explosive pressure

A lateral jet thruster operates at high temperature and high pressure, which causes ablation at the nozzle neck and malfunction of the nozzle system. The function of the solid propulsion system's nozzle is to provide thrust to the system by effectively utilising the high temperature gas that is generated in the combustion chamber. The requirements of the lateral propulsion system have to be taken into account in nozzle design, as well as the structural safety of the nozzle itself. An accurate stress analysis therefore needs to be conducted beforehand, simultaneously taking into account the thermal stress caused by the heat transfer between the high temperature gas and the wall, and the mechanical stress resulting from the pressure in the flow path. This study examined nozzle safety according to thruster operating time, where high temperature and high pressure combustion gas explodes to propel the prototype lateral thruster.

Quantum cascade laser absorption sensor for carbon monoxide in high-pressure gases using wavelength modulation spectroscopy

A tunable quantum cascade laser sensor, based on wavelength modulation absorption spectroscopy near 4.8 μm, was developed to measure CO concentration in harsh, high-pressure combustion gases. The sensor employs a normalized second harmonic detection technique (WMS-2f/1f) at a modulation frequency of 50 kHz. Wavelength selection at 2059.91 cm⁻¹ targets the P(20) transition within the fundamental vibrational band of CO, chosen for absorption strength and relative isolation from infrared water and carbon dioxide absorption. The CO spectral model is defined by the Voigt line-shape function, and key line-strength and line-broadening spectroscopic parameters were taken from the literature or measured. Sensitivity analysis identified the CO-N₂ collisional broadening coefficient as most critical for uncertainty mitigation in hydrocarbon/air combustion exhaust measurements, and this parameter was experimentally derived over a range of combustion temperatures (1100-2600 K) produced in a shock tube. Accuracy of the wavelength-modulation-spectroscopy-based sensor, using the refined spectral model, was validated at pressures greater than 40 atm in nonreactive shock-heated gas mixtures. The laser was then free-space coupled to an indium-fluoride single-mode fiber for remote light delivery. The fiber-coupled sensor was demonstrated on an ethylene/air pulse detonation combustor, providing time-resolved (~20 kHz), in situ measurements of CO concentration in a harsh flow field.

燃焼による高圧空気を駆動源とする船舶用推進装置の開発

燃焼による高圧空気を駆動源とする船舶用推進装置の開発

노즐 후방부의 Radiative Heat Flux 측정

In rocket systems, somtimes special devices or equipments are installed near the nozzle exit area where high temperature and pressure combustion gas flows. To pretect these subsystems from severe thermal environment, it is necessary to have accurate thermal data measured from the experimental liquid rocket firing test. Test variables were combustion pressure (200, 300, 400 psi) and mixture ratio (1.5, 2.0, 2.5) and quartz was used as a heat probe. Measurement technique used in this research can be also applied to measure the radiative heat flux inside the combustion chamber which is important imput data for the liquid rocket regenerative cooling system design.

Design of a diode-laser sensor to monitor water vapor in high-pressure combustion gases

The design of a diode-laser sensor to monitor water vapor in high-pressure combustion gases is described. The sensor, which employs a multiple-fixed-wavelength absorption strategy, has the potential to simultaneously monitor the water mole fraction and the temperature and pressure in high-pressure and high-temperature environments. The conventional scanned-wavelength strategy, employed in previous diode-laser sensors, is shown to be ill-suited for high-pressure applications. The application of impact and additive approximations in the modeling of H(2)O absorption features at high pressures is validated experimentally for number densities as high as 18 amagats. Criteria to select optimum wavelength combinations for the fixed-wavelengths strategy are discussed. Optimum wavelength combinations that meet these criteria are identified for different temperature and pressure ranges of interest to combustion applications. The proposed sensor configuration and a strategy to obtain the baseline (zero absorption intensity) in high-pressure environments are also described. Line-shape models that are appropriate for different temperature and pressure regimes are identified.

Blow-by through Exhaust Valve Seats in Diesel Engines. (2nd Report. Temperature Rise in Exhaust Valve Seats.).

This paper presents a systematic study regarding the durability of exhaust valve of diesel engines burning heavy fuel oil. This study has been conducted with the aim of clarifying the mechanism of blow-by in order to estimate the temperature of exhaust valve seat in operating engines. It is necessary to treat the relationship between the corrosion of the exhaust valve seats in onboard operating conditions and surface temperature of the valve seats. It has been confirmed that although the temperature of the normal exhaust valve seats is low for hot corrosion during engine operation, the seating surface temperature in the onboard operating conditions exceeds the critical temperature for hot corrosion by taking into consideration the temperature rise caused by the high temperature and high-pressure combustion gas blowing at a high velocity through local gaps of the valve seats.

Combustor and Seal System for a Water Piston Propulsor

The Water Piston Propulsor (WPP) is an advanced in-water propulsion system for Marine Corps amphibious vehicles. Significant weight and volume reductions are the primary advantages of the WPP system versus the more conventional propulsion technologies used today. WPP thrust is produced by porting high-pressure combustion gases into the water-filled channels of a rotor. Gas expansion results in the expulsion of water from the downstream end of the rotor channel. Solar Turbines Incorporated, a subsidiary of Caterpillar Inc., is currently under contract to the David Taylor Research Center for the development of the high-temperature, high-pressure combustor and rotor seal systems. Details of combustor and rotor seal design, performance, and development test are discussed.

Technology Status of Particulate Removal from High-Temperature High-Pressure Combustion Gases

The adoption of coal-fired pressurized fluidized-bed combined-cycle combustion systems by utilities for electric power generation depends to a large extent on the development of an efficient and economic cleanup system between the combustor and gas turbine. To accomplish particulate removal from a dust-laden gas stream, a number of separation devices have been developed. These include conventional and augmented cyclones; porous metal, fabric, and ceramic membrane filters; fixed-, continuously moving-, and fluidized-bed granular filters; electrostatic precipitators; as well as several other novel separation devices. The results of tests of these devices are discussed in relation to pressurized fluidized-bed combustion applications.

Erosive Effects of High-Pressure Combustion Gases on Steel Alloys

Covers advancements in spacecraft and tactical and strategic missile systems, including subsystem design and application, mission design and analysis, materials and structures, developments in space sciences, space processing and manufacturing, space operations, and applications of space technologies to other fields.

Erosion of Metals by High Pressure Combustion Gases: Inert and Reactive Erosion

An experimental and theoretical investigation of the erosion of various metals by high temperature, high pressure flows of combustion gases is described. The erosion process was categorized as either inert or a combination of inert and reactive erosion. Experimental results indicated the existence of two thresholds, the first represents the onset of erosion and the second the transition from purely inert to inert plus reactive erosion. Inert erosion was modeled by means of the melt and wipe-off theory. Experimental results are presented to demonstrate various erosion regimes and to identify the conditions for inert and reactive erosion.