Investigation on the Shock Control Using Grooved Surface in a Linear Turbine Nozzle

2017 ◽  
Author(s):  
Xinguo Lei ◽  
Mingxu Qi ◽  
Harold Sun ◽  
Leon Hu
Keyword(s):  
Shock Wave ◽  
Numerical Simulations ◽  
Smooth Surface ◽  
Engine Performance ◽  
Engine Emissions ◽  
Wave Characteristics ◽  
Grooved Surface ◽  
Rotor Stator Interaction ◽  
Nozzle Configuration ◽  
The One

Radial flow Variable Nozzle Turbine (VNT) enables better matching between a turbocharger and engine, and can improve the engine performance as well as decrease the engine emissions, especially when the engine works at low-end operation points. With increased nozzle loading, stronger shock wave and clearance leakage flow may be generated. The shock wave consequently introduces strong rotor-stator interaction between turbine nozzle and impeller, which is also a key concern of impeller high cycle fatigue failure. With the purpose of developing a shock wave free or low shock wave intensity turbine nozzle, the influence of grooved vane on the shock wave characteristics is investigated in present paper. A Schlieren visualization experiment was first carried out on a linear turbine nozzle with smooth surface and the behavior of the shock wave was studied. Numerical simulations were also performed on the turbine nozzle. The predicted shock wave shape, position and intensity were compared against the Schlieren images. Guided by the visualization and numerical simulation, grooves were designed on the nozzle surface where the shock wave was originated and numerical simulations were performed to investigate the influence of grooves on the shock wave characteristics. Results indicate that for a smooth nozzle configuration, the intensity of the shock wave increases as the expansion ratios increase, while the onset position is shifted downstream to the nozzle trailing edge. For a nozzle configuration with grooved vane, the position of the shock wave onset is shifted upstream compared to the one with a smooth surface configuration, and the intensity of the shock wave as well as the static pressure distortion at the nozzle vane exit plane are significantly depressed.

Investigation on the Shock Control Using Grooved Surface in a Linear Turbine Nozzle

2017 ◽  
Vol 139 (12) ◽  
Author(s):  
Xinguo Lei ◽  
Mingxu Qi ◽  
Harold Sun ◽  
Liangjun Hu
Keyword(s):  
Shock Wave ◽  
Numerical Simulations ◽  
Smooth Surface ◽  
Engine Performance ◽  
Engine Emissions ◽  
Wave Characteristics ◽  
Grooved Surface ◽  
Rotor Stator Interaction ◽  
Nozzle Configuration ◽  
The One

Radial flow variable nozzle turbine (VNT) enables better matching between a turbocharger and engine and can improve the engine performance as well as decrease the engine emissions, especially when the engine works at low-end operation points. With increased nozzle loading, stronger shock wave and clearance leakage flow may be generated and consequently introduces strong rotor–stator interaction between turbine nozzle and rotor, which is a key concern of rotor high-cycle fatigue (HCF) failure. With the purpose of developing a low shock wave intensity turbine nozzle, the influence of grooved vane on the shock wave characteristics is investigated in the present paper. A Schlieren visualization experiment was first carried out on a linear turbine nozzle with smooth surface and the behavior of the shock wave was studied. Numerical simulations were also performed on the turbine nozzle. Guided by the visualization and numerical simulation, grooves were designed on the nozzle surface where the shock wave was originated and numerical simulations were performed to investigate the influence of grooves on the shock wave characteristics. Results indicate that for a smooth nozzle configuration, the intensity of the shock wave increases as the expansion ratios increase, while the onset position is shifted downstream to the nozzle trailing edge. For a nozzle configuration with grooved vane, the position of the shock wave onset is shifted upstream compared to the one with a smooth surface configuration, and the intensity of the shock wave and the static pressure (Ps) distortion at the nozzle vane exit plane are significantly depressed.

Three-dimensional shock tube flows for dense gases

2007 ◽  
Vol 583 ◽  
pp. 423-442 ◽  
Author(s):  
ALBERTO GUARDONE
Keyword(s):  
Shock Wave ◽  
Shock Tube ◽  
Shock Front ◽  
Numerical Simulations ◽  
Three Dimensional ◽  
Dense Gas ◽  
Complex Flow ◽  
The Many ◽  
The One ◽  
Rarefaction Shock

The formation process of a non-classical rarefaction shock wave in dense gas shock tubes is investigated by means of numerical simulations. To this purpose, a novel numerical scheme for the solution of the Euler equations under non-ideal thermodynamics is presented, and applied for the first time to the simulation of non-classical fully three-dimensional flows. Numerical simulations are carried out to study the complex flow field resulting from the partial burst of the shock tube diaphragm, a situation that has been observed in preliminary trials of a dense gas shock tube experiment. Beyond the many similarities with the corresponding classical flow, the non-classical wave field is characterized by the occurrence of anomalous compression isentropic waves and rarefaction shocks propagating past the leading rarefaction shock front. Negative mass flow through the rarefaction shock wave results in a limited interaction with the contact surface close to the diaphragm, a peculiarity of the non-classical regime. The geometrical asymmetry does not prevent the formation of a single rarefaction shock front, though the pressure difference across the rarefaction wave is predicted to be weaker than the one which would be obtained by the complete burst of the diaphragm.

GENERATION AND SHOCK WAVE CHARACTERISTICS OF UNSTEADY PULSED SUPERSONIC LIQUID JETS

2003 ◽  
Vol 13 (5-6) ◽  
pp. 475-498 ◽  
Author(s):  
K. Pianthong ◽  
B. E. Milton ◽  
M. Behnia
Keyword(s):  
Shock Wave ◽  
Liquid Jets ◽  
Wave Characteristics

scholarly journals State of Art of Using Biofuels in Spark Ignition Engines

Energies ◽  
2021 ◽  
Vol 14 (3) ◽  
pp. 779
Author(s):  
Ashraf Elfasakhany
Keyword(s):  
Engine Performance ◽  
Spark Ignition ◽  
Pollutant Emissions ◽  
Spark Ignition Engines ◽  
Engine Emissions ◽  
Cold Starting ◽  
Starting Conditions ◽  
Unburned Hydrocarbons ◽  
Scientific Attention ◽  
State Of Art

Biofuels are receiving increased scientific attention, and recently different biofuels have been proposed for spark ignition engines. This paper presents the state of art of using biofuels in spark ignition engines (SIE). Different biofuels, mainly ethanol, methanol, i-butanol-n-butanol, and acetone, are blended together in single dual issues and evaluated as renewables for SIE. The biofuels were compared with each other as well as with the fossil fuel in SIE. Future biofuels for SIE are highlighted. A proposed method to reduce automobile emissions and reformulate the emissions into new fuels is presented and discussed. The benefits and weaknesses of using biofuels in SIE are summarized. The study established that ethanol has several benefits as a biofuel for SIE; it enhanced engine performance and decreased pollutant emissions significantly; however, ethanol showed some drawbacks, which cause problems in cold starting conditions and, additionally, the engine may suffer from a vapor lock situation. Methanol also showed improvements in engine emissions/performance similarly to ethanol, but it is poisonous biofuel and it has some sort of incompatibility with engine materials/systems; its being miscible with water is another disadvantage. The lowest engine performance was displayed by n-butanol and i-butanol biofuels, and they also showed the greatest amount of unburned hydrocarbons (UHC) and CO emissions, but the lowest greenhouse effect. Ethanol and methanol introduced the highest engine performance, but they also showed the greatest CO2 emissions. Acetone introduced a moderate engine performance and the best/lowest CO and UHC emissions. Single biofuel blends are also compared with dual ones, and the results showed the benefits of the dual ones. The study concluded that the next generation of biofuels is expected to be dual blended biofuels. Different dual biofuel blends are also compared with each other, and the results showed that the ethanol–methanol (EM) biofuel is superior in comparison with n-butanol–i-butanol (niB) and i-butanol–ethanol (iBE).

Crashworthiness Performance of Mass-Efficient Extruded Structures

2002 ◽  
Author(s):  
Robert R. Mayer ◽  
Weigang Chen ◽  
Anil Sachdev
Keyword(s):  
Numerical Simulations ◽  
Single Cell ◽  
Experimental Testing ◽  
Experimental Studies ◽  
Nonlinear Material ◽  
Dynamic Strain ◽  
Cell Design ◽  
Explicit Finite Element ◽  
The One ◽  
Crushing Behavior

Theoretical, numerical and experimental studies were conducted on the axial crushing behavior of traditional single-cell and innovative four-cell extrusions. Two commercial aluminum alloys, 6061 and 6063, both with two tempers (T4 and T6), were considered in the study. Testing coupons taken from the extrusions assessed the nonlinear material properties. A theoretical solution was available for the one-cell design, and was developed for the mean crushing force of the four-cell section. Numerical simulations were carried out using the explicit finite element code LS-DYNA. The aluminum alloy 6063T4 was found to absorb less energy than 6061T4, for both the one-cell and four-cell configurations. Both 6061 and 6063 in the T6 temper were found to have significant fracture in the experimental testing. Theoretical analysis and numerical simulations predicted a greater number of folds for the four-cell design, as compared to the one-cell design, and this was confirmed in the experiments. The theoretical improvement in energy absorption of 57% for the four-cell in comparison with the one-cell design was confirmed by experiment. The good agreement between the theoretical, numerical and experimental results allows confidence in the application of the theoretical and numerical tools for both single-cell and innovative four-cell extrusions. It was also demonstrated that these materials have very little dynamic strain rate effect.

scholarly journals Relativistic shock waves induced by ultra-high laser pressure

2014 ◽  
Vol 32 (2) ◽  
pp. 243-251 ◽  
Author(s):  
Shalom Eliezer ◽  
Noaz Nissim ◽  
Erez Raicher ◽  
José Maria Martínez-Val
Keyword(s):  
Shock Wave ◽  
Shock Waves ◽  
Laser Irradiance ◽  
Compression Pressure ◽  
Relativistic Shock ◽  
Electron Positron ◽  
High Laser ◽  
Wave Compression ◽  
The One ◽  
First Time

AbstractThis paper analyzes the one dimensional shock wave created in a planar target by the ponderomotive force induced by very high laser irradiance. The laser-induced relativistic shock wave parameters, such as compression, pressure, shock wave and particle flow velocities, sound velocity and temperature are calculated here for the first time in the context of relativistic hydrodynamics. For solid targets and laser irradiance of about 2 × 1024 W/cm2, the shock wave velocity is larger than 50% of the speed of light, the shock wave compression is larger than 4 (usually of the order of 10) and the targets have a pressure of the order of 1015 atmospheres. The estimated temperature can be larger than 1 MeV in energy units and therefore very excited physics (like electron positron formation) is expected in the shocked area. Although the next generation of lasers might allow obtaining relativistic shock waves in the laboratory this possibility is suggested in this paper for the first time.

Investigation on the Influence of a Core Chevron Nozzle on the Performance of a Modern Bypass Engine

2004 ◽  
Author(s):  
Matthias Weißschuh ◽  
Stephan Staudacher
Keyword(s):  
Engine Performance ◽  
Ambient Air ◽  
Performance Comparison ◽  
Turbine Engines ◽  
Gas Streams ◽  
Discharge Velocity ◽  
Chevron Nozzle ◽  
Nozzle Configuration ◽  
Chevron Nozzles ◽  
Considerable Work

In light of intensifying environmental concerns, the noise in aircraft gas turbine engines needs to be reduced significantly. Considerable work has been conducted to reduce jet noise produced by the mixing of high velocity gas streams with ambient air. Various nozzle designs such as lobed nozzles, serrated nozzles or chevron nozzles have been used and proposed to control and modify the velocity pattern of exhaust gas streams. This paper presents investigations on the influence of a core chevron nozzle on the performance of a modern bypass engine. The characteristic discharge, velocity and specific thrust coefficients of the chevron and non-chevron nozzles are determined by numerical calculations and are verified with experimental data. The nozzle coefficients form the basis for an engine performance comparison between the two hot nozzle configurations of the bypass engine. The effect of the nozzle configuration on overall engine performance and component working points has been investigated by applying an engine performance synthesis tool. The thrust loss and the corresponding SFC increase which has been observed by using the chevron nozzle have been related to engine internal rematching and changes in nozzle performance.

Flow With Shock Waves in a Transonic Centrifugal Compressor With a Low-Solidity Cascade Diffuser Using PIV

2004 ◽  
Author(s):  
Hiroshi Hayami ◽  
Masahiro Hojo ◽  
Norifumi Hirata ◽  
Shinichiro Aramaki
Keyword(s):  
Shock Wave ◽  
Shock Waves ◽  
Centrifugal Compressor ◽  
Gas Flow ◽  
Pressure Ratio ◽  
Transonic Centrifugal Compressor ◽  
Image Velocimetry ◽  
Rotor Stator Interaction ◽  
Rotating Impeller ◽  
Low Solidity Cascade Diffuser

A single-stage transonic centrifugal compressor with a pressure ratio greater than six was tested in a closed loop with HFC134a gas. Flow at the inducer of a rotating impeller as well as flow in a stationary low-solidity cascade diffuser was measured using a double-pulse and double-frame particle image velocimetry (PIV). Shock waves in both flows were clearly observed. The effect of flow rate on a 3D configuration of shock wave at the inducer and a so-called rotor-stator interaction between a rotating impeller and a stationary cascade were discussed based on a phase-averaged measurement technique. Furthermore, the unsteadiness of inducer shock wave and the flow in a cascade diffuser during surge were discussed based on instantaneous velocity vector maps.

DROPLET FEEDBACK ON VAPOR IN A WARM CLOUD

2009 ◽  
Vol 23 (28n29) ◽  
pp. 5434-5443 ◽  
Author(s):  
ANTONIO CELANI ◽  
ANDREA MAZZINO ◽  
MARCO TIZZI
Keyword(s):  
Numerical Simulations ◽  
Droplet Size ◽  
Cloud Droplet ◽  
Direct Numerical Simulations ◽  
Cloud Droplets ◽  
Size Spectra ◽  
New Model ◽  
Warm Cloud ◽  
Local Reduction ◽  
The One

A new model to study the effect of turbulence on the cloud droplets in the condensation phase is proposed and its behavior investigated by direct numerical simulations. The model is a generalization of the one by Celani, Mazzino, Tizzi, New J. Phys.10, 075021 (2008), where the droplet feedback on vapor is now explicitly taken into account. Physically, it amounts to considering the fact that when a cloud droplet increases its size, vapor is subtracted from the ambient with the net result of a local reduction in the supersaturation field. It is shown how this effect plays to reduce the broadening of droplet size spectra in the condensation stage and thus to produce results in closer agreement with observations.

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