Impacts of the Split Conjugated Pistons in Conjugated Cylinders of a Multiple Stage Reciprocating Compressor in Start Duration

1999 ◽  
Author(s):  
Jianqiang Deng ◽  
Zhaolin Gu ◽  
Yongzhang Yu
Keyword(s):  
Mathematical Model ◽  
High Pressure ◽  
Material Selection ◽  
Threshold Value ◽  
Discharge System ◽  
Pressure Stage ◽  
Multi Stage ◽  
Start Up ◽  
High Pressure Stage ◽  
The Impact

Abstract Split pistons allow more precise manufacturing and easier assembly of conjugate-piston multi-stage reciprocating compressors. Their disadvantage is that during start up, the high pressure stage piston may impact with both its cylinder head and the low-pressure stage piston. To determine the magnitude of these impacts and how they can be minimized, a simple mathematical model was constructed to analyze the pressure build-up within the compressor and the movement of the high-pressure stage piston. It is shown that above a minimum threshold value of pressure in the high-pressure stage, the pistons remain attached and move together without impact. The calculation of this minimum pressure along with the contact stresses, during rounds of impacts when the forces are greatest is demonstrated. A mathematical model is also provided to help minimize the impact stresses involved in such an arrangement. It is shown that by appropriate piston design and choice of piston material, selection of the optimum stroke and volume of the discharge system as well as the electric motor, split-conjugate pistons can be used in high-pressure multi-stage compressors.

scholarly journals Nonlinear Analysis of the Dynamics of Criminality and Victimisation: A Mathematical Model with Case Generation and Forwarding

2019 ◽  
Vol 2019 ◽  
pp. 1-17
Author(s):  
Chikodili Helen Ugwuishiwu ◽  
D. S. Sarki ◽  
G. C. E. Mbah
Keyword(s):  
Mathematical Model ◽  
Numerical Simulations ◽  
Nonlinear Analysis ◽  
Deterministic Model ◽  
Positive Impact ◽  
Threshold Value ◽  
Dynamical Analysis ◽  
Viable Option ◽  
Effective Implementation ◽  
The Impact

In this paper, a system of deterministic model is presented for the dynamical analysis of the interactional consequence of criminals and criminality on victimisation under two distinguishable forms of rehabilitation—the behavioural reformation of criminals and the emotional psychotherapy of victims. A threshold value, R0=maxRK,RV, responsible for the persistence of crime/criminality and victimisation, is obtained and, using it, stability analyses on the model performed. The impact of an effective implementation of the two forms of rehabilitation was found to be substantial on crime and criminality, while an ineffective implementation of same was observed to have a detrimental consequence. The prevention of repeat victimisation was seen to present a more viable option for containing crime than the noncriminalisation of victims. Further, the removal of criminals, either through quitting or death, among others, was also found to have a huge positive impact. Numerical simulations were performed for a variety of mixing criminal scenarios to verify the analytical results obtained.

Dual-Stage Turbocharger Matching and Boost Control Options

2008 ◽  
Author(s):  
Byungchan Lee ◽  
Dohoy Jung ◽  
Dennis Assanis ◽  
Zoran Filipi
Keyword(s):  
High Pressure ◽  
Diesel Engines ◽  
Pressure Ratio ◽  
Boost Pressure ◽  
High Pressure Turbine ◽  
Multi Stage ◽  
Bypass Valve ◽  
Dual Stage ◽  
Engine System ◽  
The Impact

Diesel engines are gaining in popularity, penetrating even the luxury and sports vehicle segments that have traditionally been strongly favored gasoline engines as the performance and refinement of diesel engines have improved significantly in recent years. The introduction of sophisticated technologies such as common rail injection (CRI), advanced boosting systems such as variable geometry and multi-stage turbocharging, and exhaust gas after-treatment systems have renewed the interest in Diesel engines. Among the technical advancements of diesel engines, the multi-stage turbocharging is the key to achieve such high power density that is suitable for the luxury and sports vehicle applications. Single-stage turbocharging is limited to roughly 2.5 bar of boost pressure. In order to raise the boost pressure up to levels of 4 bar or so, another turbocharger must be connected in series further multiplying the pressure ratio. The dual-stage turbocharging, however, adds system complexity, and the matching of two turbochargers becomes very costly if it is to be done experimentally. This study presents a simulation-based methodology for dual-stage turbocharger matching through an iterative procedure predicting optimal configurations of compressors and turbines. A physics-based zero-dimensional Diesel engine system simulation with a dual-stage turbocharger is implemented in SIMULINK environment, allowing easy evaluation of different configurations and subsequent analysis of engine system performance. The simulation program is augmented with a turbocharger matching program and a turbomachinery scaling routine. The configurations considered in the study include a dual-stage turbocharging system with a bypass valve added to the high pressure turbine, and a system with a wastegate valve added to a low-pressure turbine. The systematic simulation study allows detailed analysis of the impact of each of the configurations on matching, boost characteristics and transient response. The configuration with the bypass valve across high pressure turbine showed better results in terms of both steady state engine torque and transient behavior.

Field Testing of the Flowback Technology for Multistage-Fractured Horizontal Wells: Generalization to Find an Optimum Balance Between Aggressive and Smooth Scenarios

2021 ◽  
Author(s):  
Albert Vainshtein ◽  
Georgii Fisher ◽  
Gleb Strizhnev ◽  
Sergei Boronin ◽  
Andrei Osiptsov ◽  
...  
Keyword(s):  
Mathematical Model ◽  
Pressure Drop ◽  
Hydraulic Fracture ◽  
Fracture Length ◽  
Well Production ◽  
Drop Dynamics ◽  
Start Up ◽  
Cumulative Production ◽  
Fluid Rheology ◽  
The Impact

Abstract We present the results of field experiments campaign on start-up of wells located in a sandstone oilfield of Western Siberia and history matching of coupled "wellbore-hydraulic fracture" model describing well start-up and fracture clean-up. The conclusion is made about the impact of rheological and geomechanical factors on the well cumulative production andfracture conductivity.The results are generalized for four wells of the field experiment and 30 wells of the retrospective analysis. Calculations of well startup are carried out using standalone fracture cleanup model and the coupled model, which includes models for filtration inside closed hydraulic fracture and flow in the wellbore. The data obtained during field tests on well startup is used to history match the fracture clean-up model. The adaptation allows to evaluate the sensitivity of well production to various physical parameters and find the safe operating envelope of operational parameters during well startup. Numerical simulations allow take into account geomechanics effectsand rheology properties of fracturing fluid, study the dynamics of effective (cleaned) fracture length as well as evaluate the influence of pressure drop dynamics on filtration properties of the fracture and cumulative well production. We extended the number of wells to study the impact of flowback scenarios on production andgeneralized the results of our previous study.Key parameters affecting the history match process of the mathematical model are determined,the uncertainty associated with fluid rheology is reduced. Using the history-matched model, we evaluated geomechanics effects on fracture degradation depending on bottom-hole pressure drop dynamics. Based on the obtained dynamics of dimensionless parameters, such as pressure and fracture productivity, we propose an optimized well start-up strategy aimed at maximizing effective fracture length and cumulative production. Additionally, we visualized the dynamics of fracture conductivity distribution along its length. The obtained results are consistent with interpretation of physical processes accompanying well start-up and fracture clean-up. Dimensionless productivity index is chosen to quantify the effects of geomechanics and fluid rheology on well production.On the basis of matched mathematical model, we predict a potential increase in production of the well with optimized start-up.The recommendations are presented in the form of the dynamics of wellhead choke opening and a sequence of choke diameters. We propose an integrated approach for planning a well flowback strategy after multi-stage hydraulic fracturing. The proposed decision-making algorithm considers the effects of geomechanics and yield-stress hydraulic fracturing fluid rheology on cumulative production. It allows to develop a design for the well start-up and fracture cleanup in terms of dynamics of wellheadchoke opening.

The Influence of Roughness on a High-Pressure Steam Turbine Stage: An Experimental and Numerical Study

2014 ◽  
Author(s):  
Juri Bellucci ◽  
Filippo Rubechini ◽  
Michele Marconcini ◽  
Andrea Arnone ◽  
Lorenzo Arcangeli ◽  
...  
Keyword(s):  
High Pressure ◽  
Steam Turbine ◽  
Numerical Study ◽  
Practical Interest ◽  
Numerical Approach ◽  
Fine Tuning ◽  
High Pressure Steam ◽  
Pressure Steam ◽  
High Pressure Stage ◽  
The Impact

This work deals with the influence of roughness on high-pressure steam turbine stages. It is divided in three parts. In the first one, an experimental campaign on a linear cascade is described, in which blade losses are measured for different values of surface roughness and in a range of Reynolds numbers of practical interest. The second part is devoted to the basic aspects of the numerical approach, and consists of a detailed discussion of the roughness models used for computations. The fidelity of such models is then tested against measurements, thus allowing their fine-tuning and proving their reliability. Finally, comprehensive CFD analysis is carried out on a high-pressure stage, in order to investigate the influence of roughness on the losses over the entire stage operating envelope. Unsteady effects that may affect the influence of the roughness, such as the upcoming wakes on the rotor blade, are taken into account, and the impact of transition-related aspects on the losses is discussed.

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