Dynamic behavior of high-pressure arcs near the flow stagnation point

1989 ◽  
Vol 17 (3) ◽  
pp. 524-533 ◽  
Author(s):  
J.F. Zhang ◽  
M.T.C. Fang
Keyword(s):  
High Pressure ◽  
Stagnation Point ◽  
Dynamic Behavior ◽  
Flow Stagnation

A Model for the Estimation of Pressure Ripple in Tandem Gear Pumps

2015 ◽  
Author(s):  
Mattia Battarra ◽  
Emiliano Mucchi ◽  
Giorgio Dalpiaz
Keyword(s):  
High Pressure ◽  
Dynamic Behavior ◽  
Low Pressure ◽  
Variable Pressure ◽  
Geometrical Parameters ◽  
Gear Pump ◽  
Helical Gears ◽  
Pressure Stage ◽  
Outlet Pressure ◽  
Pressure Ripple

The present paper addresses the development of a lumped parameters model used to analyze the dynamic behavior of a so-called tandem gear pump. The pump is composed of two coaxial stages, both with external gears: a high pressure stage with spur gears and a low pressure one with helical gears. In particular, the paper deals with the modelling and the analysis of the phenomena bound to the pressure distribution around the gears, since they have the most important effect in the dynamic behavior of the pump. The pressure variation in the inlet and outlet chambers, the variable pressure in the trapped volume as well as the pressure evolution from the low to the high pressure chamber is estimated based on the Euler’s approach. The model is developed in Matlab environment. Attention is particularly focused on the description of the methodology adopted for modelling the low-pressure stage, constituted by helical gears, and its influence on the calculation of the pump geometrical parameters. The results provided by the numerical model are compared with experimental measurements in terms of outlet pressure ripple and volumetric efficiency under different working conditions. The results of the validation can be considered satisfactory. Predicted pressure ripple is shown and the effects of interconnections between stages are analyzed studying the outlet pressure ripple in the frequency domain as well.

Comparison of Two Methods for Flame Transfer Function Measurements: MOOG Valve or Siren and the Impact of Results on the Instability Analysis in a High Pressure Combustor

2012 ◽  
Author(s):  
M. Kapucu ◽  
J. B. W. Kok ◽  
P. R. Alemela
Keyword(s):  
High Pressure ◽  
Transfer Function ◽  
Dynamic Behavior ◽  
Limit Cycle ◽  
Network Model ◽  
Thermal Power ◽  
Absolute Pressure ◽  
Viscous Damping ◽  
Instability Analysis ◽  
Damping Effects

Thermoacoustic instabilities may occur in every gas turbine combustor and could be hazardous to the flame stability and the structural integrity. It is important to be able to predict how hazardous the instabilities are: at what frequencies will they occur and will they develop into high amplitude limit cycle oscillations? The former question can be answered with the help of the Flame Transfer Function (FTF). The FTF establishes the coupling between burner passage aerodynamics and combustion dynamics and can be used as an input to an acoustic model to predict the eigenfrequencies and their growth rate. In the present research two methods to measure the FTF are used with different signal excitation instruments: a MOOG Valve and a Siren. Both the methods are based on data from pressure transducers only. The FTF is measured here by determining the combustor pressure response of the flame to fluctuations in the fuel mass flow at the burner exit. A siren unit has been developed and mounted at the upstream end of the fuel supply line of a pressurized combustor and is designed to have a harmonic excitation. The experimental method to measure the FTF by means of factorization in known or measurable sub-functions is briefly explained. Subsequently the Siren method is demonstrated by means of extracting the FTF at elevated pressure and as a function of thermal power. The results are compared with the results obtained in previous work of a MOOG valve excitation unit. The experimental investigation of the FTF is carried out in a high pressure combustor rig named DESIRE which is able to perform thermoacoustic measurements up to 500 kW thermal power at 5 bar absolute pressure. The results are compared and discussed. Subsequently a 1-D acoustic network model is presented which predicts the onset of the limit cycle pressure oscillations in the DESIRE combustor, using the FTF as an input. Thermo viscous damping effects and measured reflection coefficients are also included into the network model to improve the model predictions. Finally, the measured and predicted dynamic behavior of the combustor are compared. The results indicate that the network modeling approach is a promising design tool as it gives good agreement between measured and predicted dynamic behavior of the combustor and instability analysis. Well-defined boundary conditions and thermo viscous damping effects are important for the accuracy of the acoustic network models.

Dynamic Behavior of an Intruder in a Granular Couette Flow

2002 ◽  
Vol 759 ◽  
Author(s):  
Jian Liu ◽  
Anthony D. Rosato
Keyword(s):  
High Pressure ◽  
Dynamic Behavior ◽  
Couette Flow ◽  
Depth Profile ◽  
Three Dimensional ◽  
Discrete Element ◽  
Granular Temperature ◽  
Uniform Particles ◽  
Discrete Element Simulations ◽  
Large Spherical

ABSTRACTThis paper reports on three-dimensional, steady discrete element simulations of a single large spherical intruder in a gravity-free granular Couette flow of uniform particles with diameter d. The non-equilibrium nature of the flow is characterized by the depth profile of granular temperature, which decreases inwards toward the center. An intruder of size φ = D/d migrates away from the walls at a rate that increases with φ and wall velocity U. Computations indicated that the intruder's motion is induced by the high pressure near the wall.

Dynamic Analysis of Diesel Engine Common Rail Injection System: Part II — Four-Cylinder Injection System

2001 ◽  
Author(s):  
M. Borghi ◽  
M. Milani ◽  
M. Piraccini
Keyword(s):  
High Pressure ◽  
Diesel Engine ◽  
Dynamic Behavior ◽  
Common Rail ◽  
Injection System ◽  
Common Rail System ◽  
Common Rail Injection System ◽  
Rail System ◽  
Common Rail Injection ◽  
The Common

Abstract The paper is aimed at studying the overall dynamic behavior of the Common Rail Injection System actually used on a 4 cylinder industrial Diesel engine. Firstly, the paper introduces the main characteristics of a lumped and distributed parameters model of the high pressure branch of an actual Common Rail System, and the main hypotheses assumed to model it using a multi-port approach code for the analysis of the dynamic response of hydraulic systems submitted to fast transients. The model of the Common Rail System is then used to study its dynamic behavior when involved in the handling of the engine injection cycle for medium values of the crankshaft regime and for different pressure levels in the Rail. The analysis is performed applying to the injectors, to the pressure control valve and to the high-pressure pump the control strategies imposed by the Electronic Central Unit (ECU), as actually implemented into an industrial ECU for Diesel engine management. The model reliability and accuracy are evidenced through a numerical vs. experimental data comparison, mainly in term of rail pressure dynamic behavior. The analysis successively outlined in the paper allows to state how the hydraulic behavior of the Common Rail System interact with the electro-hydraulic injectors dynamics, and to determine the influence of this interaction on the total injected mass per cycle.

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