Showing papers on "Total pressure published in 2022"

Preliminary Criterion for Positive Total Pressure Gain in Kerosene/Air Rotating Detonation Combustor

Abstract: The rotating detonation combustor is promising to be a total pressure gain combustor and receives considerable attention in the past decade. Many studies have pointed out that the pressure gain performance is significantly related to the inlet area ratio, whereas no criterion for obtaining positive total pressure gain has been established until now. This study performed a series of numerical simulations to investigate the idealized total pressure gain performance of vapor kerosene/air rotating detonation combustor by varying the inlet area ratios and injection total pressures. A preliminary criterion for obtaining positive total pressure gain in vapor kerosene/air rotating detonation combustor is established and then validated with simulation cases and existing research. The results indicate that the total pressure gain increases with the increase of the inlet area ratio and chamber diameter, whereas it decreases with the increase of the injection total pressure. The established criterion can serve as a reference value for the design of the vapor kerosene/air rotating detonation combustor, above which a positive total pressure gain can be obtained.

Combined Methodology for Conceptual Design of 2D External Compression Inlet and Dual Serpentine Diffuser

Abstract: Jet engines in fighter aircraft require a certain amount of air to reach the Aerodynamic Interface Plane (AIP) at a given flight condition. In the conceptual and preliminary design stages of the aircraft, the inlet size and performance need to be estimated for the integration of the propulsion system and overall aircraft performance evaluation. There is plenty of research published individually on inlet and diffuser, however, a combined design methodology for supersonic inlet and subsonic diffuser for given design conditions (i.e. design Mach, altitude, and engine required mass flow rate) is rarely found in the literature. This study presents the complete design methodology of a two-dimensional supersonic external compression inlet and dual serpentine subsonic diffuser for the initial design stages of the aircraft. Analytical sizing of the two-dimensional external compression inlet was done at Mach 1.8 and an altitude of 11,000 m. The transverse and stream-wise pressure gradients in the diffusing duct were controlled using centerline and area distribution equations obtained through mathematical modeling of the diffuser. A total of nine configurations were considered for the subsonic diffusion of the flow through numerical optimization and the best configuration in terms of pressure recovery, flow distortion, and swirl angle was determined by CFD analysis. The centerline with modest turning at the entrance and exit, and the area distribution with sharp diffusion at the entrance and slow diffusion at the exit gave a maximum pressure recovery of 95.51% and minimum flow swirl of 2.48° with an acceptable distortion coefficient (DC60) of 0.54. Results proclaim the diffuser performance as a complex function of its shape and prone to any slight change in the geometric variables.

Design and Aerodynamic Performance Estimation of an Axial Fan according to the Total Pressure Ratio of Blade Span Length

Abstract: This study deals with the design method of an axial fan that can make a blade by parameterizing the blade outlet angle as a function of the hub ratio, assuming that the optimal total pressure distribution in the span direction is a non-free vortex flow. In addition, the performance of the designed axial fan was obtained by analyzing it with large eddy simulation (LES) in a three-dimensional, incompressible flow. As a result, the exponent of the total pressure ratio function that satisfies the diffusion factor 0.6 or less ranges from 0.49 to 1.0 for each radius. The static pressure, the total and respective efficiencies of the axial fan analyzed by LES have similar sizes to those of the existing axial fan. On the other hand, it can be designed while predicting the total pressure according to the geometric size of the axial fan at the operating point if this design method is combined with the Cordier diagram. It is judged that the design method of this axial fan can be very usefully used as a general axial fan or ducted axial fan.

Аналіз впливу кривизни S-подібного каналу та умов польоту на ефективність ковшового вхідного пристрою

Abstract: When creating a modern aircraft, the principle of optimal integration of the power plant and the aircraft is used to ensure the maximum target function, determined by its functional purpose. The specific fuel consumption and specific thrust of the power plant depend significantly on the loss of the total air pressure in the inlet device, which is characterized by the total recovery factor. The change in pressure along the diameter of the propfan affects the efficiency of the inlet of the power plant. When using the inlet ring device, its efficiency decreases, due to low pressure in the area of the root part of the propfan blades. The use of a bucket inlet allows air to be supplied to the channel from the area located near the middle part of the blade height and this is the main factor influencing the reduction of pressure losses in the air supply channel. When using a bucket inlet, curvature and constriction are important factors influencing the effectiveness of S-channels. The influence of the curvature of the S-shaped channel on the total pressure recovery coefficient at a constant value of its narrowing is studied in this work. The study S-shaped channel in its geometric parameters is equivalent to the channel of the annular inlet device of a power plant with a turbofan engine. The total pressure recovery coefficient of an S-shaped channel is calculated from the flow parameters in the sections of the S-shaped channel by solving the Navier-Stokes equations using the Florian Menter two-layer turbulence model (SST Transitional No. 4 Gamma Theta) and the combined finite element model at the entrance to the channel and in the channel itself - hexahedral, at the exit tetrahedral. An analysis of the dependence of the total pressure recovery coefficient of the S-shaped channel on the M number and the channel curvature shows that, up to a curvature of 0.002, the total pressure recovery coefficient is not significantly affected. A further increase in the channel curvature has a significant effect on the change in the total pressure recovery coefficient, which is associated with flow separation and losses from the vortex formation.

Impact investigation of inlet environmental changes on the rated condition performance of a high-pressure compressor

Abstract: Abstract The variations of inlet environment parameters can make significant effects on the compressor performance. This paper aims to investigate the effects of inlet total pressure and total temperature changes on the rated condition performance of a nine-stage HPC. Different cases of total pressure and total temperature boundary conditions at this compressor inlet are studied by 3-D numerical simulations with experimental validations. The numerical results confirm that the variations of inlet total pressure and total temperature make different effects on the rated condition performance of compressor. The overall performance parameters, such as the corrected mass flow and isentropic efficiency, will increase with inlet total pressure increasing and decrease with inlet total temperature increasing by different change rules. The flow similarity is also investigated by comparing the calculated results of critical quantities in different cases. The results indicate that the rising inlet total pressure can increase the Reynolds number and it is beneficial to reduce the viscous influence so that it is available to improve the performance; the rising inlet total temperature can decrease both the specific heat ratio and Reynolds number so that it will lead to the compressor performance decline inevitably.

Research on Wind Tunnel Test of the Total Pressure Probe Layout for Civil Aircraft

Abstract: AbstractThe total pressure probe of civil aircraft plays an important role in the atmospheric data system. It is used to measure the total pressure of the incoming flow during flights. The total pressure probe should be installed at a correct position on the nose which local angle can be covered by local angle requirement of the total pressure probe in all flight envelope. According to the above wind tunnel tests of the total pressure probe with part model and full model were designed. The characteristics of total pressure loss of total pressure probe were obtained in the full model wind tunnel test. In the full model wind tunnel test a simplified fuselage with two types of miniature probe was designed to carry out the aerodynamic layout test of total pressure probe. Two types of miniature probes include a similar shaped probe and a seven-hole probe which measure the local total pressure and the local angle of the probe respectively. The variation characteristics of the local angle and the total pressure loss coefficient with the altering fuselage angle of attack and sideslip angle were obtained in the full model test. From the two aspects above, the satisfaction of the local angle and the total pressure loss coefficient for the probe installation position on the aircraft nose can be determined. The design of the miniature probe fills the technical blank of the total pressure probe wind tunnel test model. This type of wind tunnel test can accurately examine the reasonability of the layout of the total pressure probe for civil aircraft.KeywordsTotal pressure probeLocal angleWind tunnel testMiniature probeTotal pressure loss coefficient

Effects of total pressure on carbon nanotube synthesis, independent of feed pressure

Abstract: While the effects of partial pressure of carbon feed on the growth of carbon nanotubes (CNTs) are well documented, the effects of total pressure in the growth chamber are not well understood. To shed some light, we investigated the growth of CNTs at different total pressures and a constant partial pressure using catalytic chemical vapour deposition method. It was observed that the growth height and diameter of CNTs decreased as the total pressure increased, probably due to the dilution of carbon feed, the increase in the boundary layer thickness and the decrease in the gas diffusion coefficient. Furthermore, the growth quality of the CNTs was found to be highest at intermediate total pressures. This can provide clues as to where the best temperature concentration is for high-quality CNTs.

Numerical investigation of an aggressive s-shaped compressor transition duct with boundary layer suction

Abstract: Aggressive s-shaped compressor transition ducts are important components in the connection between upstream boosters and downstream high-pressure compressors. The flow path is an s-shaped channel with struts and a large radial drop length ratio, which breaks through the limitations of traditional design and has a large aerodynamic loss. Therefore, this paper considers an aggressive s-shaped compressor transition duct in a geared turbofan engine and creatively proposes a method for controlling the flow separation through boundary layer suction. The results show that hub suction reduces the losses of the aggressive s-shape transition duct. As the mass flow rate of hub suction increases, the total pressure loss coefficient decreases and the rate of reduction in the total pressure loss slows down. Combined boundary layer suction reduces the total pressure loss to a greater extent. On the premise that the location of blade suction remains unchanged, the optimal location for the circumferential slot of hub suction is at 20% of the axial chord length of the strut, whereby the total pressure loss coefficient decreases by about 30% compared with the case of no suction. When the mass flow rate of suction is fixed at 3% of the inlet mass flow rate, a distribution of 0.5% from blade suction and 2.5% from hub suction reduces the total pressure loss by 1.6% compared with the case where all 3% comes from hub suction. The distribution of the mass flow rate for combined boundary layer suction has an optimal ratio.

Numerical simulation of S-shaped inlet under the intake total pressure distortion

Abstract: During the development of the stealth fighter, the S-shaped inlet enters the designer’s vision because it has better stealth than bump inlet and straight inlet. During the use of the S-shaped inlet, due to its structural reasons, secondary flow is likely to occur in the curved section, which directly causes the flow state to be changeable and complicated. Therefore, this paper takes the S-shaped inlet as the research object to analyzes the steady flow field simulation under uniform inlet condition and distortion inlet condition and analyze the flow field of the airflow and the total pressure of each section under the S-shaped inlet by changing the intake distortion conditions with CFX software. The results show that although the S-shaped inlet will occur total pressure distortion under uniform intake. However, when the S-shaped inlet work under certain flight conditions, the level of total pressure distortion will be smaller than the uniform inlet condition, which can improve the air intake performance. Finally, it can be inferred that with use of the S-shaped intake port, the deterioration of distortion may be prevented under certain specific intake conditions.

Influence of single-point total pressure probe installation position on the flow field and measurement results of the inlet stage outlet of the compressor

Abstract: The measurement accuracy of a single-point L-type total pressure probe in the inlet stage outlet flow path of a vortex engine compressor and the influence of the probe on the flow field were investigated via numerical simulation. The change pattern of probe measurement results with flow rate under three typical operating conditions of cruise, maximum continuous and takeoff were analyzed, as well as the influence of the installation position on the probe measurement results. The present results show that the measurement error of the probe gradually increases with the increasing of inlet flow rate. The relative measurement error of total probe pressure is the smallest and the measurement error is linear with the flow rate at a ratio(D/d) of 6.5. The relative measurement error of the total probe pressure is greatest when the installation position is located near the leaf basin compared to the leaf back. As the probe is installed closer to the back of the leaf, the total pressure loss coefficient downstream of the probe decreases more slowly and the probe has a greater range of influence on the flow field in the flow direction. When the installation position is located near the leaf basin and leaf back, the velocity uniformity between 5 mm and 24 mm downstream of the probe is smaller.

Effects of Tip Clearance on Internal Flow and Loss Generation Mechanism in an Axial Compressor at Windmilling Conditions

Abstract: The internal flow structure and loss generation mechanism of a single-stage compressor during windmilling were investigated through experimental and computational analyses. The windmilling state occurs when the air flowing through an unlit engine drives the compressor rotor blades, similar to a turbine. This study focused on the effect of tip clearance size on the internal flow during windmilling operations. Therefore, detached eddy simulations were conducted at three tip clearance conditions: without clearance, design clearance, and wide clearance. Consequently, the total pressure loss decreased when the size of the tip clearance was expanded under windmilling conditions. In the windmilling state, separation on the pressure side due to the high negative incidence was generated, which was the main reason for the total pressure loss. When the size of the clearance increased, the size of the separation decreased because of the tip leakage flow. According to the detailed numerical results for the windmilling state, the leakage flow held the separation to the blade surface near the tip area. In addition, the tip leakage flow formed a blockage in the midchord, so the tip side of the separation vortex was moved to the midchord and formed a significant loss region. Thus, the tip leakage flow reduced the loss region, and the overall loss was reduced.

Numerical simulation of a two-dimensional S-shaped inlet

Abstract: In order to solve the problem that different operation conditions affect the performance of S-shaped inlet, we have carried out a numerical study on a two-dimensional S-shaped inlet and analysed the influences of incoming Mach number, attack of angle α and the outlet pressure on the performance parameters of the inlet, such as the total pressure recovery coefficient, total compression ratio and the steady-state total pressure distortion index at the exit of inlet. The results show that Ma number and the outlet pressure are the main factors affecting inlet performance. With the increase of Ma number, the total pressure recovery coefficient of inlet decreases from 0.975 to 0.793, the total compression ratio decreases from 1.212 to 1.146, and the steady-state total pressure distortion index increases from 0.0536 to 0.377. The flow energy loss in the inlet increases, the flow uniformity decreases, and the inlet performance becomes worse. With the increase of the outlet pressure, the total pressure recovery coefficient of inlet rises from 0.875 to 0.931, the total compression ratio rises from 1.101 to 1.216, and the steady-state total pressure distortion index decreases from 0.219 to 0.123. The mass flow rate of inlet and airflow loss decrease, and the performance of the inlet improves. We study the influence of different operation conditions on the inlet performance, which provides a certain reference for the performance evaluation of S-shaped inlet.

Effect of the distribution of the upstream probe support on performance of compressor cascade

Abstract: Abstract Aiming at the problem of aerodynamic coupling interference between disturbance of the built-in measurement probe and internal flow of high load compressor, the experiment of axial position and structure dimension of cylindrical probe support effect on the performance of the compressor cascade was carried out on the transonic plane cascade test facility. The effect characteristics of the distribution of probe support on aerodynamic performance of downstream cascade under different inlet Mach numbers were analyzed through the experimental data. The experimental results show that the axial position of probe support has little impact on the total pressure loss coefficient of cascade under the low-speed inlet flow condition. However, the variety of the axial position of probe support has a great impact on the total pressure loss coefficient of cascade under the high-speed inlet flow condition. With the decrease of the axial distance between probe support and cascade, the total pressure loss coefficient of cascade increases. Under different inlet flow conditions, the variety of the structure dimension of probe support has a significant impact on the total pressure loss coefficient of cascade. With the increase of the structure dimension of probe support, the total pressure loss coefficient of cascade increases.

Settlement and Capacity of Piles Under Large Number of Cyclic Loads

Abstract: This study reports a group of field tests on cyclically loaded piles installed in soft clay in Huzhou, China. Two 29.5 m long pipe piles were instrumented with transducers to measure the accumulated settlement at the pile-head, the pore water pressure and total pressure at the pile-soil interface, and axial load at the pile end, respectively. The major objective of the field testing is to gain a better understanding of the evolution of the pile-head settlement and the effective stress at the pile-soil interface. The results of cyclic loading tests under different combinations of static load and cyclic load are discussed with reference to changes in the pile capacity, the permanent settlement, and the radial stresses. It is found that the permanent settlement of piles can be characterized as quickly stabilized (QS), progressively developing (PD), and dramatically failed (DF) patterns. Under low-level loading (QS pattern), the pile-shaft earth pressure is nearly undisturbed, final gains in effective stress are observed due to slight dissipation of pore pressure. For intermediate-level loading (PD pattern), significant reductions in pore pressure, earth pressure, and effective stress are observed after cyclic loading. Regarding high-level loading (DF pattern), the quick accumulation of pore water pressure leads to a slight increase in earth pressure, resulting in a continuous decrease in effective stress.