Investigation of the Shock Wave Formation and Intensity in Wave Rotor

2021 ◽  
Vol 143 (11) ◽  
Author(s):  
Peiqi Liu ◽  
Xiang Li ◽  
Xinyu Liu ◽  
Jun Yang ◽  
Mingyu Feng ◽  
...  
Keyword(s):  
Shock Wave ◽  
High Pressure ◽  
Rotational Speed ◽  
Expansion Ratio ◽  
Wave Intensity ◽  
Dynamics Simulation ◽  
Wave Rotor ◽  
Compression Waves ◽  
The Difference ◽  
The One

Abstract Actual formation and intensity of shock wave generated during gradual opening and closure between each port and passages of wave rotor are studied by means of experiment and computational fluid dynamics simulation. The results show that the intensity of shock wave increases with the distance from high-pressure inlet, and the reason for the variation tendency is the superposition of compression waves. By changing the rotational speed and the expansion ratio, the shock wave intensity can be adjusted, but the position where the intensity reaches maximum stays constant basically and keeps the distance near 300 mm from high-pressure inlet. Comparing with the one-dimensional simplification result, the actual intensity of shock wave is lower. The difference between the fact and simplification increases with the rotational speed and expansion ratio. The internal mechanism has been analyzed from the aspect of intake mass. Then, the maximum shock wave intensity is found approximately linear to the intake mass of each rotor passage in each cycle.

Influence of Skewing of Contact Face on Performance of Wave Rotor Refrigerators and Superchargers

2013 ◽  
Author(s):  
Yuqiang Dai ◽  
Fengxia Liu ◽  
Jintao Wu ◽  
Wei Wei ◽  
Dapeng Hu ◽  
...  
Keyword(s):  
High Pressure ◽  
Mach Number ◽  
Shock Waves ◽  
Rotational Speed ◽  
Channel Width ◽  
Wave Rotor ◽  
Coriolis Forces ◽  
Local Loss ◽  
Expansion Waves ◽  
Pressure Port

As a novel generation of rotational gas wave machines, wave rotor machines such as wave rotor refrigerators (WRR) and wave rotor superchargers (WRS) are unsteady flow devices. In their passages two gas streams (with different pressure or even different phases) comes into direct contact can exchange energy due to the movement of shock waves and expansion waves. A detailed study shows that, when rotor channels open to the high pressure port gradually, the contact face in rotor channels inevitably skews, which is always accompanied with reflection of shockwaves. This causes very large energy dissipation and influences adversely on the refrigeration performance of WRR or the supercharging performance of WRS. In this work, factors such as centrifugal forces, Coriolis forces, gradual channel opening and gradual channel closing, etc, which influence the wave transportation and skewing of shock waves and contact faces are studied by means of computational fluid dynamics and experiments. The skewing of contact faces causes uneven distribution of velocity and large local loss. With rotation Mach number smaller than 0.3, the skewing of contact face can be alleviated. To reduce the adverse influence of rotation Mach number, a smaller rotor channel width or higher rotational speed is necessary. The rotation effect plays an important role for the skewing of gas discontinuities. Both the centrifugal and Coriolis forces of wave rotor cannot be ignored with the Rossby number of 1.3∼3.5. To reduce the skewing loss of contact face, a lower rotational speed seems necessary. The rotation speed of wave rotors has dialectical influences on the skewing of shock waves and contact faces. The jetting width of high pressure port is the key factor of the gradual opening of rotor channels. A feasible way to reduce skewing losses of gas waves is to optimize the ratio between high pressure port width and channel width. The validation experiments have got at least 3∼5% rise of isentropic efficiency for WRRs.

Multiphase Flow in a Liquid-Ring Vacuum Pump

2020 ◽  
Vol 143 (1) ◽  
Author(s):  
Ashutosh Pandey ◽  
Sajid Khan ◽  
Rick Dekker ◽  
Tom I-P. Shih
Keyword(s):  
Multiphase Flow ◽  
Rotational Speed ◽  
Computational Study ◽  
Critical Role ◽  
Expansion Ratio ◽  
Navier Stokes ◽  
Compression And Expansion ◽  
Acceleration And Deceleration ◽  
The Difference ◽  
Liquid Ring

Abstract A computational study based on unsteady Reynolds-averaged Navier–Stokes that resolves the gas–liquid interface was performed to examine the unsteady multiphase flow in a liquid-ring pump as a function of its inlet pressure (10, 40, and 80 kPa) and its impeller's rotational speed (1150, 1450, and 1750 rpm). Results obtained show the shape of the liquid ring to play a critical role in creating the expansion ratio needed to draw air into the pump and the compression ratio needed to expel air out of the pump. The dominant processes that determine the shape of the liquid ring was found to be the centrifugal force from rotation, the acceleration and deceleration due to the difference in pressure at the pump's inlet and outlet, and the eccentricity of the impeller relative to the pump's housing. Results are presented to show how the rotational speed of the impeller and the pressure at the pump's inlet affect the nature of the multiphase flow in the pump as well as the pump's effectiveness in creating a vacuum. The effects of heat transfer on the gas phase during the compression and expansion processes were found to be approximated well by polytropic processes. This computational study was validated by comparing computed with measured volumetric flowrates ingested through the suction port and the torque exerted on the pump's impeller.

Unsteady Heat Transfer Between Gas and Tube in a Wave Rotor Refrigerator

2020 ◽  
Vol 12 (5) ◽  
Author(s):  
Dapeng Hu ◽  
Jingxian Wang ◽  
Mei Wu ◽  
Tingjiang Liu ◽  
Yiming Zhao ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Shock Wave ◽  
High Pressure ◽  
Wave Propagation ◽  
Wall Temperature ◽  
Great Influence ◽  
Longitudinal Direction ◽  
Heat Absorption ◽  
Wave Rotor ◽  
Unsteady Heat Transfer

Abstract The performance of a wave rotor refrigerator (WRR) is strongly affected by unsteady heat transfer between gas and tubes. In this work, the mechanism of the heat transfer and its effects on WRR were investigated numerically and experimentally. Results show that the heat absorption of wave rotor occurs in the process of shock wave propagation, and heat release happens in other processes. The unsteady heat transfer causes an uneven wall temperature. The temperature varies along the longitudinal direction, while the time variation can be neglected. Furthermore, the position of the bolts, which link the wave rotor and the shaft, has a great influence on WRR gaps. The closer the position of bolts to the high-pressure (HP) nozzle is, the less effect of gaps would be. The research is an important guiding significance to the improvement of WRR refrigeration performance and WRR design.

scholarly journals The Pressure Control of High-Pressure Tubing Based on Difference Equation

2020 ◽  
Vol 2020 ◽  
pp. 1-9
Author(s):  
Yang Zhang ◽  
Rongjun Li ◽  
Linhai Zou
Keyword(s):  
High Pressure ◽  
Difference Equation ◽  
Fuel Injection ◽  
Control Method ◽  
Pressure Control ◽  
Needle Valve ◽  
Oil Pump ◽  
Pressure Tubing ◽  
The Difference ◽  
The One

The situation where fuel enters and exits the high-pressure tubing is one of the important factors that affect the working efficiency of the engine. Based on the simplified high-pressure tubing model, this paper studies the control problems of high-pressure tubing injection and fuel supply under certain circumstances. According to the idea of the difference equation, the paper obtains the opening time of the one-way valve when the pressure value of the high-pressure tubing is kept constant or rises to a specific value by enumerating the opening time of the one-way valve. By establishing the physical model of the high-pressure tubing and the fuel injection nozzle, and then using the enumeration method, the angular velocity of the high-pressure oil pump cam when the pressure of the high-pressure fuel pipe is kept constant can be obtained. Under the more complicated injector model, the control method of the injector is solved by the double enumeration method. The results show that the above model can quickly calculate the optimal working time of the high-pressure fuel pump and needle valve when the accuracy meets the requirements.

scholarly journals Experimental Research about Shock Wave in a 1+1/2 Counter-Rotating Turbine

2018 ◽  
Vol 151 ◽  
pp. 02005
Author(s):  
Chao Li ◽  
Huo-Xing Liu ◽  
Zhi-Hong Zhou
Keyword(s):  
Shock Wave ◽  
High Pressure ◽  
Flow Field ◽  
Experimental Research ◽  
Guide Vane ◽  
Wave Structure ◽  
Expansion Ratio ◽  
Shock Wave Structure ◽  
Supersonic Wind Tunnel ◽  
Unsteady Effect

To investigate the internal distribution regularities of shock wave structure in 1+1/2 counter-rotating turbine, numerical simulation and experimental research about the shock wave structure were conducted by using the schlieren apparatus under different working conditions.From the point of the unsteady results, the unsteady effect has few influence on the flow field of high pressure guide vane, but the wake of the high pressure guide leaves periodically sweeps through the front edge of the high pressure blade and there presents strong unsteady effect on flow field of high pressure rotor. Because of periodic influence of external wake and shock wave, the unsteadiness of flow in low pressure rotor is still strong but not that drastic compared to the high pressure rotor. 50% height section of the blade of the three types of blades are extracted respectively to make plane cascades which are conducted blowing experiments in supersonic wind tunnel. The final photograph were analyzed by comparing with the CFD results. Results show that with the increase of expansion ratio, the wave structures in blade channel move toward the exit and the caudal interference between the outer tail wave and is strengthened gradually.

Coordination and polyamorphism of aluminium silicate under high pressure: insight from analysis and visualization of molecular dynamics data

2014 ◽  
Vol 92 (12) ◽  
pp. 1573-1580 ◽  
Author(s):  
N.V. Hong ◽  
N.V. Yen ◽  
M.T. Lan ◽  
P.K. Hung
Keyword(s):  
Molecular Dynamics ◽  
High Pressure ◽  
Pressure Range ◽  
Microphase Separation ◽  
Random Network ◽  
Structural Phase ◽  
Dynamics Simulation ◽  
Structural Units ◽  
The Difference ◽  
Aluminium Silicate

The amorphous aluminium silicate (Al2O3)·2(SiO2) (abbreviated as AS2) is investigated using a molecular dynamics simulation with the Born–Mayer potential. The models of amorphous AS2 are constructed in a wide pressure range. The results show that the structure of AS2 mainly consists of the basic structural units TOx (T is Al or Si; x = 4, 5, 6). The topology of basic structural units at different pressures is identical. Two adjacent units TOx are linked to each other through common oxygen atoms and form a continuous random network of basic structural units TOx. The different aluminium silicate states result from the difference of the fraction of units TOx and their spatial distributions. The coordination units (triclusters) OAl3 and OSi3 and (tetraclusters) OAl4 and OSi4 result in AlOx-rich and SiOx-rich regions, and this is the origin of the microphase separation. Regarding the polymorphism, it can be seen that the structure of AS2 comprises three structural phases: TO4, TO5, and TO6 structural phases. The size of TO4 structural phase regions decreases and the size of TO6 structural phase regions increases as pressure increases. Inversely, the size of TO5 structural phase regions increases to a maximum value and then decreases as pressure increases. In the considered pressure range, with increasing pressure, there is a transformation from TO4 structural phase (at low pressure) to TO6 structural phase (at high pressure).

scholarly journals Investigation of Coalescence-Induced Droplet Jumping on Mixed-Wettability Superhydrophobic Surfaces

Processes ◽  
2021 ◽  
Vol 9 (1) ◽  
pp. 142
Author(s):  
Ming-Jun Liao ◽  
Li-Qiang Duan
Keyword(s):  
Contact Angle ◽  
Simulation Method ◽  
Strip Width ◽  
Superhydrophobic Surfaces ◽  
Dynamics Simulation ◽  
Periodic Strip ◽  
Mixed Wettability ◽  
Potential Applications ◽  
The Difference ◽  
The One

Coalescence-induced droplet jumping has received more attention recently, because of its potential applications in condensation heat transfer enhancement, anti-icing and self-cleaning, etc. In this paper, the molecular dynamics simulation method is applied to study the coalescence-induced jumping of two nanodroplets with equal size on the surfaces of periodic strip-like wettability patterns. The results show that the strip width, contact angle and relative position of the center of two droplets are all related to the jumping velocity, and the jumping velocity on the mixed-wettability superhydrophobic surfaces can exceed the one on the perfect surface with a 180° contact angle on appropriately designed surfaces. Moreover, the larger both the strip width and the difference of wettability are, the higher the jumping velocity is, and when the width of the hydrophilic strip is fixed, the jumping velocity becomes larger with the increase of the width of the hydrophobic strip, which is contrary to the trend of fixing the width of the hydrophobic strip and altering the other strip width.

Use of a Lyophilized Reference Plasma to Compare Coagulation Test Procedures

1975 ◽  
Vol 34 (02) ◽  
pp. 426-444 ◽  
Author(s):  
J Kahan ◽  
I Nohén
Keyword(s):  
Oral Anticoagulant Therapy ◽  
Repeated Measurements ◽  
Test Procedures ◽  
Coagulation Activity ◽  
Close Relationship ◽  
Measured Activity ◽  
Test Materials ◽  
The Difference ◽  
The Stability ◽  
The One

SummaryIn 4 collaborative trials, involving a varying number of hospital laboratories in the Stockholm area, the coagulation activity of different test materials was estimated with the one-stage prothrombin tests routinely used in the laboratories, viz. Normotest, Simplastin-A and Thrombotest. The test materials included different batches of a lyophilized reference plasma, deep-frozen specimens of diluted and undiluted normal plasmas, and fresh and deep-frozen specimens from patients on long-term oral anticoagulant therapy.Although a close relationship was found between different methods, Simplastin-A gave consistently lower values than Normotest, the difference being proportional to the estimated activity. The discrepancy was of about the same magnitude on all the test materials, and was probably due to a divergence between the manufacturers’ procedures used to set “normal percentage activity”, as well as to a varying ratio of measured activity to plasma concentration. The extent of discrepancy may vary with the batch-to-batch variation of thromboplastin reagents.The close agreement between results obtained on different test materials suggests that the investigated reference plasma could be used to calibrate the examined thromboplastin reagents, and to compare the degree of hypocoagulability estimated by the examined PIVKA-insensitive thromboplastin reagents.The assigned coagulation activity of different batches of the reference plasma agreed closely with experimentally obtained values. The stability of supplied batches was satisfactory as judged from the reproducibility of repeated measurements. The variability of test procedures was approximately the same on different test materials.

The Demand For Money in Pakistan: Reply (Notes and Comments)

1975 ◽  
Vol 14 (3) ◽  
pp. 370-375
Author(s):  
M. A. Akhtar
Keyword(s):  
Interest Rates ◽  
Money Demand ◽  
Strong Support ◽  
Physical Capital ◽  
Careful Examination ◽  
Demand For Money ◽  
Weak Support ◽  
Complementarity Hypothesis ◽  
The Difference ◽  
The One

I am grateful to Abe, Fry, Min, Vongvipanond, and Yu (hereafter re¬ferred to as AFMVY) [1] for obliging me to reconsider my article [2] on the demand for money in Pakistan. Upon careful examination, I find that the AFMVY results are, in parts, misleading and that, on the whole, they add very little to those provided in my study. Nevertheless, the present exercise as well as the one by AFMVY is useful in that it furnishes us with an opportunity to view some of the fundamental problems involved in an empi¬rical analysis of the demand for money function in Pakistan. Based on their elaborate critique, AFMVY reformulate the two hypo¬theses—the substitution hypothesis and the complementarity hypothesis— underlying my study and provide us with some alternative estimates of the demand for money in Pakistan. Briefly their results, like those in my study, indicate that income and interest rates are important in deter¬mining the demand for money. However, unlike my results, they also suggest that the price variable is a highly significant determinant of the money demand function. Furthermore, while I found only a weak support for the complementarity between money demand and physical capital, the results obtained by AFMVY appear to yield a strong support for that rela¬tionship.1 The difference in results is only a natural consequence of alter¬native specifications of the theory and, therefore, I propose to devote most of this reply to the criticisms raised by AFMVY and the resulting reformulation of the two mypotheses.

Effect of leakage and blockage on the acoustic behavior of particle filters

2019 ◽  
Vol 67 (6) ◽  
pp. 483-492
Author(s):  
Seonghyeon Baek ◽  
Iljae Lee
Keyword(s):  
Transfer Matrix ◽  
Particle Filters ◽  
Acoustic Analysis ◽  
Transmission Loss ◽  
One Dimensional ◽  
Filter System ◽  
The Difference ◽  
The One ◽  
Analytical Approaches ◽  
Good Agreement

The effects of leakage and blockage on the acoustic performance of particle filters have been examined by using one-dimensional acoustic analysis and experimental methods. First, the transfer matrix of a filter system connected to inlet and outlet pipes with conical sections is measured using a two-load method. Then, the transfer matrix of a particle filter only is extracted from the experiments by applying inverse matrices of the conical sections. In the analytical approaches, the one-dimensional acoustic model for the leakage between the filter and the housing is developed. The predicted transmission loss shows a good agreement with the experimental results. Compared to the baseline, the leakage between the filter and housing increases transmission loss at a certain frequency and its harmonics. In addition, the transmission loss for the system with a partially blocked filter is measured. The blockage of the filter also increases the transmission loss at higher frequencies. For the simplicity of experiments to identify the leakage and blockage, the reflection coefficients at the inlet of the filter system have been measured using two different downstream conditions: open pipe and highly absorptive terminations. The experiments show that with highly absorptive terminations, it is easier to see the difference between the baseline and the defects.

Sign in / Sign up

Export Citation Format

Share Document