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Full-Text Articles in Mechanical Engineering

Shock Compaction Of Graphene Doped Yttria Stabilized Zirconia: An Experimental And Computational Study, Christopher Rueben Johnson Apr 2019

Shock Compaction Of Graphene Doped Yttria Stabilized Zirconia: An Experimental And Computational Study, Christopher Rueben Johnson

Master's Theses (2009 -)

Yttria stabilized zirconia (YSZ) is a broadly used ceramic due to its impeccable hardness and thermal stability. Limitations of the material, however, subsist within its fracture toughness. Literature indicates that shock consolidation may enable production of composite YSZ and graphene mixtures with improved fracture toughness and other material properties while maintaining the material’s nanostructure dimensionality. Therefore, investigation of the compaction phenomena at non-equilibrium states will provide informative results to be used in the fabrication of bulk graphene-YSZ composites. Computational molecular dynamics (MD) simulations and impact experiments are conducted to explore and characterize the dynamic response of the YSZ variants ...


Control Design And Implementation Of An Active Transtibial Prosthesis, Joseph Klein Jul 2018

Control Design And Implementation Of An Active Transtibial Prosthesis, Joseph Klein

Master's Theses (2009 -)

Prior work at Marquette University developed the Marquette Prosthesis, an active transtibial prosthesis that utilized a torsional spring and a four-bar mechanism. The controls for the Marquette Prosthesis implemented a finite state control algorithm to determine the state of gait of the amputee along with two lower level controllers, a PI moment controller to control the moment during stance and a PID position controller to control the position during stance. The Marquette Prosthesis was successful in mimicking the gait profile presented by Winter. However, after completing human subject testing, the Marquette Prosthesis was insufficient in trying to match the gait ...


Geometric Construction-Based Realization Of Spatial Elastic Behaviors In Parallel And Serial Manipulators, Shuguang Huang, Joseph M. Schimmels Mar 2018

Geometric Construction-Based Realization Of Spatial Elastic Behaviors In Parallel And Serial Manipulators, Shuguang Huang, Joseph M. Schimmels

Mechanical Engineering Faculty Research and Publications

This paper addresses the realization of spatial elastic behavior with a parallel or a serial manipulator. Necessary and sufficient conditions for a manipulator (either parallel or serial) to realize a specific elastic behavior are presented and interpreted in terms of the manipulator geometry. These conditions completely decouple the requirements on component elastic properties from the requirements on mechanism kinematics. New construction-based synthesis procedures for spatial elastic behaviors are developed. With these synthesis procedures, one can select each elastic component of a parallel (or serial) mechanism based on the geometry of a restricted space of allowable candidates. With each elastic component ...


A Degradation Function Consistent With Cocks–Ashby Porosity Kinetics, John A. Moore Jan 2018

A Degradation Function Consistent With Cocks–Ashby Porosity Kinetics, John A. Moore

Mechanical Engineering Faculty Research and Publications

The load carrying capacity of ductile materials degrades as a function of porosity, stress state and strain-rate. The effect of these variables on porosity kinetics is captured by the Cocks–Ashby model; however, the Cocks–Ashby model does not account for material degradation directly. This work uses a yield criteria to form a degradation function that is consistent with Cocks–Ashby porosity kinetics and is a function of porosity, stress state and strain-rate dependence. Approximations of this degradation function for pure hydrostatic stress states are also explored.


Construction And Characterization Of A Single Stage Dual Diaphragm Gas Gun, Nathaniel Steven Helminiak Oct 2017

Construction And Characterization Of A Single Stage Dual Diaphragm Gas Gun, Nathaniel Steven Helminiak

Master's Theses (2009 -)

In the interest of studying the propagation of shock waves, this work sets out to design, construct, and characterize a pneumatic accelerator that performs high-velocity flyer plate impact tests. A single stage gas gun with a dual diaphragm breach allows for a non-volatile, reliable experimental testing platform for shock phenomena. This remotely operated gas gun utilizes compressed nitrogen to launch projectiles down a 14 foot long, 2 inch diameter bore barrel, which subsequently impacts a target material of interest. A dual diaphragm firing mechanism allows the 4.5 liter breech to reach a total pressure differential of 10ksi before accelerating ...


The Effects Of A Reduced Force Aerial Bucket Control On Upper Extremity Muscular Demands As Assessed With Surface Electromyography, Casey D. Garces Oct 2017

The Effects Of A Reduced Force Aerial Bucket Control On Upper Extremity Muscular Demands As Assessed With Surface Electromyography, Casey D. Garces

Master's Theses (2009 -)

A common control for operating aerial bucket trucks for utility companies in North America is called a pistol grip control. Based upon many anecdotal reports of forearm muscle fatigue from workers using this control, Prof. Richard Marklin began an EPRI-sponsored study in 2016 using EMG to determine muscle fatigue of workers while they used the pistol grip. Muscle activity recorded by EMG is a measure of the magnitude of muscle force under controlled conditions. This study confirmed the reports of muscle fatigue in extensor digitorum communis (EDC) muscle in the right forearm. The next phase of the study was to ...


Performance Analysis Of Constant Speed Local Abstacle Avoidance Controller Using A Mpc Algorithym On Granular Terrain, Nicholas Haraus Oct 2017

Performance Analysis Of Constant Speed Local Abstacle Avoidance Controller Using A Mpc Algorithym On Granular Terrain, Nicholas Haraus

Master's Theses (2009 -)

A Model Predictive Control (MPC) LIDAR-based constant speed local obstacle avoidance algorithm has been implemented on rigid terrain and granular terrain in Chrono to examine the robustness of this control method. Provided LIDAR data as well as a target location, a vehicle can route itself around obstacles as it encounters them and arrive at an end goal via an optimal route. This research is one important step towards eventual implementation of autonomous vehicles capable of navigating on all terrains. Using Chrono, a multibody physics API, this controller has been tested on a complex multibody physics HMMWV model representing the plant ...


Design Of A Passive Ankle Prosthesis With Energy Return That Increases With Increasing Walking Velocity, Alexander J. Folz Oct 2017

Design Of A Passive Ankle Prosthesis With Energy Return That Increases With Increasing Walking Velocity, Alexander J. Folz

Master's Theses (2009 -)

Patients who undergo a transtibial (below the knee) amputation are often met with a difficult decision: selection of a prosthesis. Limitations of currently available prostheses motivate work on a new solution, the EaSY Walk, a passive device that mimics two key aspects of the natural ankle: non-linear rotational stiffness through implementation of a stiffening flexure mechanism and rotational work output that varies as a function of walking velocity to propel the user forward. To achieve the latter, a strategy to convert the maximum available translational energy acquired from deflection along the leg into rotational energy about the ankle joint through ...


Applied Force And Semg Muscle Activity Required To Operate Pistol Grip Control In An Electric Utility Aerial Bucket, Richard W. Marklin Jr., Jonathaon E. Slightam, Mark L. Nagurka, Trent M. Wolff, Casey D. Garces, Lovely Krishen Sep 2017

Applied Force And Semg Muscle Activity Required To Operate Pistol Grip Control In An Electric Utility Aerial Bucket, Richard W. Marklin Jr., Jonathaon E. Slightam, Mark L. Nagurka, Trent M. Wolff, Casey D. Garces, Lovely Krishen

Mechanical Engineering Faculty Research and Publications

Electric utility line workers report high levels of fatigue in forearm muscles when operating a conventional pistol grip control in aerial buckets. This study measured the applied force and surface electromyographic (sEMG) signals from four upper extremity muscles required to operate the pistol grip control in two tasks. The first task was movement of the pistol grip in six directions (up/down, forward/rearward, clockwise/counter-clockwise), and the second task was movement of the bucket from its resting position on the truck bed to an overhead conductor on top of a 40 ft tall pole. The force applied to the ...


Run-Out Based Crossed Roller Bearing Life Prediction By Utilization Of Accelerated Testing Approach And Fe Numerical Models, Luca Quagliato, Dongwook Kim, Nara Lee, Soyoung Hwang, Joseph P. Domblesky, Naksoo Kim Sep 2017

Run-Out Based Crossed Roller Bearing Life Prediction By Utilization Of Accelerated Testing Approach And Fe Numerical Models, Luca Quagliato, Dongwook Kim, Nara Lee, Soyoung Hwang, Joseph P. Domblesky, Naksoo Kim

Mechanical Engineering Faculty Research and Publications

Surface wear and spalling phenomena are the most important factors affecting roller bearing performance and operational lifetime, in terms of number of cycles the bearing can operate. Although bearing life has been traditionally defined by the onset of spalling, as specified by international standard ISO 281, this definition does not always reflect the real operational conditions, since bearing wear can also represent a failure criterion when excessive run-out occurs. In such cases, bearing life needs to be predicted according to the amount of bearing run-out resulting from wear due to load and number of cycles. In the current study, the ...


Effect Of Multiphase Radiation On Coal Combustion In A Pulverized Coal Jet Flame, Bifen Wu, Somesh Roy, Xinyu Zhao, Michael F. Modest Aug 2017

Effect Of Multiphase Radiation On Coal Combustion In A Pulverized Coal Jet Flame, Bifen Wu, Somesh Roy, Xinyu Zhao, Michael F. Modest

Mechanical Engineering Faculty Research and Publications

The accurate modeling of coal combustion requires detailed radiative heat transfer models for both gaseous combustion products and solid coal particles. A multiphase Monte Carlo ray tracing (MCRT) radiation solver is developed in this work to simulate a laboratory-scale pulverized coal flame. The MCRT solver considers radiative interactions between coal particles and three major combustion products (CO2, H2O, and CO). A line-by-line spectral database for the gas phase and a size-dependent nongray correlation for the solid phase are employed to account for the nongray effects. The flame structure is significantly altered by considering nongray radiation and the ...


A Parametric Investigation And Optimization Of A Cylindrical Explosive Charge, Logan Ellsworth Beaver Jul 2017

A Parametric Investigation And Optimization Of A Cylindrical Explosive Charge, Logan Ellsworth Beaver

Master's Theses (2009 -)

Explosive device design has a wide impact in the space, manufacturing, military, and mining industries. As a step toward computer assisted design of explosives, an optimization framework was developed using the Design Analysis Kit for Optimization and Terrascale Applications (Dakota). This software was coupled with the hydrocode CTH. This framework was applied to three exploding cylinder models, two in 1D and one in 2D. Gradient descent, dividing rectangles, and a genetic algorithm were each applied to the one-dimensional models. Parametric studies were performed as a basis for comparison with the optimization algorithms, as well as qualifying the 1D model's ...


Pore Resolved Simulations Of Char Particle Gasification, Greg Hingwah Fong Jul 2017

Pore Resolved Simulations Of Char Particle Gasification, Greg Hingwah Fong

Master's Theses (2009 -)

Coal is a significant source of energy in today’s world and many studies have been conducted in order to better understand and optimize its use. To address greenhouse effects associated with coal combustion, cleaner methods for harnessing its energy are being explored. One such method is gasification, a process which converts coal into syngas, a mixture consisting primarily of H2 and CO. Syngas can be used to generate electricity or to produce hydrocarbons that can be used as fuels. To better understand and optimize the process, simulations can be used to study the gasification of individual porous char particles ...


An Analysis Of Testing Variables In Rapid Compression Machine Experiments, Jenna Ezzell Jul 2017

An Analysis Of Testing Variables In Rapid Compression Machine Experiments, Jenna Ezzell

Master's Theses (2009 -)

There have been discrepancies noted with regards to experimental data from rapid compression machines (RCM). When data is compared from different RCM facilities, the ignition delay times are inconsistent when inspecting any particular temperature. Currently in publications, if these datasets are compared, the discrepancy is said to be due to heat loss, however this issue has yet to be examined more thoroughly. To determine what the root cause of this discrepancy is, four different fake RCM facilities were created and simulated. There were also different sets of initial conditions used to determine how this may affect the data. They were ...


Adaptive Control Of Joystick Steering In Recreational Boats, John Bayless Jul 2017

Adaptive Control Of Joystick Steering In Recreational Boats, John Bayless

Master's Theses (2009 -)

This thesis addresses the challenge of commissioning recreational boats with joystick control when the boat’s physical parameters are not known. The research was conducted by following a model-based, systems engineering approach which leveraged MATLAB simulations and scale-model physical testing. The outcome of the research is a working methodology using L1 Adaptive Control which provides fast adaption in a way that could reduce the cost of commissioning recreational boats with joystick control, improve the robustness of the final design, and potentially expand the accessible market to new boat types.


Development Of An Optimal Controller And Validation Test Stand For Fuel Efficient Engine Operation, Jack G. Rehn Iii Jul 2017

Development Of An Optimal Controller And Validation Test Stand For Fuel Efficient Engine Operation, Jack G. Rehn Iii

Master's Theses (2009 -)

There are numerous motivations for improvements in automotive fuel efficiency. As concerns over the environment grow at a rate unmatched by hybrid and electric automotive technologies, the need for reductions in fuel consumed by current road vehicles has never been more present. Studies have shown that a major cause of poor fuel consumption in automobiles is improper driving behavior, which cannot be mitigated by purely technological means. The emergence of autonomous driving technologies has provided an opportunity to alleviate this inefficiency by removing the necessity of a driver. Before autonomous technology can be relied upon to reduce gasoline consumption on ...


Investigation Of The Scanning Microarc Oxidation Process, Linqin Xia, Jianmin Han, Joseph P. Domblesky, Zhiyong Yang, Weijing Li Jun 2017

Investigation Of The Scanning Microarc Oxidation Process, Linqin Xia, Jianmin Han, Joseph P. Domblesky, Zhiyong Yang, Weijing Li

Mechanical Engineering Faculty Research and Publications

Scanning microarc oxidation (SMAO) is a coating process which is based on conventional microarc oxidation (MAO). The key difference is that deposition in SMAO is achieved by using a stainless steel nozzle to spray an electrolyte stream on the substrate surface as opposed to immersing the workpiece in an electrolyzer. In the present study, SMAO discharge characteristics, coating morphology, and properties are analyzed and compared to results obtained from MAO under similar conditions. Results show that MAO and SMAO have comparable spark and microarc lifetimes and sizes, though significant differences in incubation time and discharge distribution were evident. Results also ...


Characterization Of The Shock Wave Structure In Water, Emilie Teitz Apr 2017

Characterization Of The Shock Wave Structure In Water, Emilie Teitz

Master's Theses (2009 -)

The scientific community is interested in furthering the understanding of shock wave structures in water, given its implications in a wide range of applications; from researching how shock waves penetrate unwanted body tissues to studying how humans respond to blast waves. Shock wave research on water has existed for over five decades. Previous studies have investigated the shock response of water at pressures ranging from 1 to 70 GPa using flyer plate experiments. This report differs from previously published experiments in that the water was loaded to shock pressures ranging from 0.36 to 0.70 GPa. The experiment also ...


Developing A Low-Cost Force Treadmill Via Dynamic Modeling, Chih-Yuan Hong, Lan-Yuen Guo, Rong Song, Mark L. Nagurka, Jia-Li Sung, Chen-Wen Yen Jan 2017

Developing A Low-Cost Force Treadmill Via Dynamic Modeling, Chih-Yuan Hong, Lan-Yuen Guo, Rong Song, Mark L. Nagurka, Jia-Li Sung, Chen-Wen Yen

Mechanical Engineering Faculty Research and Publications

By incorporating force transducers into treadmills, force platform-instrumented treadmills (commonly called force treadmills) can collect large amounts of gait data and enable the ground reaction force (GRF) to be calculated. However, the high cost of force treadmills has limited their adoption. This paper proposes a low-cost force treadmill system with force sensors installed underneath a standard exercise treadmill. It identifies and compensates for the force transmission dynamics from the actual GRF applied on the treadmill track surface to the force transmitted to the force sensors underneath the treadmill body. This study also proposes a testing procedure to assess the GRF ...


Direct Quadrature Method Of Moments With Delumping For Modeling Multicomponent Droplet Vaporization, Simcha L. Singer Dec 2016

Direct Quadrature Method Of Moments With Delumping For Modeling Multicomponent Droplet Vaporization, Simcha L. Singer

Mechanical Engineering Faculty Research and Publications

A multicomponent droplet vaporization model which combines the computational efficiency of continuous thermodynamic approaches with the detailed species information provided by discrete component models has been developed. The Direct Quadrature Method of Moments (DQMoM) is used to efficiently solve for the evolution of the nodes and weights of the equivalent liquid-phase mole fraction distribution without assuming any functional form. The novelty of the approach is an inexpensive delumping procedure that is used to reconstruct the time-dependent mole fractions and fluxes for all discrete species. When applied to a vaporizing kerosene droplet, agreement between the full discrete component model, which solves ...


Modeling Pyrolysis Of Large Coal Particles With Many Species, Jianqing Li Oct 2016

Modeling Pyrolysis Of Large Coal Particles With Many Species, Jianqing Li

Master's Theses (2009 -)

Coal currently supplies 40% of the world’s electricity needs, and is one of the most important energy sources. As the initial stage of coal combustion, pyrolysis is a thermal decomposition process which converts coal into light gases and tars, which are subsequently consumed in combustion reactions, as well as solid char. Recently there has been interest in using slow pyrolysis as a stand-alone process for the production of chemicals and fuels from large (mm-scale) coal particles. Simulations can be used to efficiently study the impact of pyrolysis conditions on gas, tar and char yields, as well as gas and ...


Analysis Of Fatigue Crack Propagation In Welded Steels, Roberto Angelo Demarte Oct 2016

Analysis Of Fatigue Crack Propagation In Welded Steels, Roberto Angelo Demarte

Master's Theses (2009 -)

This thesis presents the study of fatigue crack propagation in a low carbon steel (ASTM A36) and two different weld metals (AWS A5.18 and AWS A5.28). Fatigue crack propagation data for each weld wire is of interest because of its use for predicting and analyzing service failures. Fatigue crack growth test specimens were developed and fabricated for the low carbon steel base metal and for each weld wire. Weld specimens were stress relieved prior to fatigue testing. Specimens were tested on a closed-loop servo hydraulic test machine at two different load ratios. Fatigue test data was collected to ...


Realization Of Point Planar Elastic Behaviors Using Revolute Joint Serial Mechanisms Having Specified Link Lengths, Shuguang Huang, Joseph M. Schimmels Sep 2016

Realization Of Point Planar Elastic Behaviors Using Revolute Joint Serial Mechanisms Having Specified Link Lengths, Shuguang Huang, Joseph M. Schimmels

Mechanical Engineering Faculty Research and Publications

This paper presents methods for the realization of 2 × 2 translational compliance matrices using serial mechanisms having only revolute joints, each with selectable compliance. The link lengths of the mechanism and the location of the compliant frame relative to the mechanism base are arbitrary but specified. The realizability of a given compliant behavior is investigated, and necessary and sufficient conditions for the realization of a given compliance with a given mechanism are obtained. These realization conditions are interpreted in terms of geometric relationships among the joints. We show that, for an appropriately sized 3R serial mechanism, any single 2 × 2 ...


Analysis And Synthesis Of A Planar Reconfigurable Mechanism With A Variable Joint, Peter William Malak Jul 2016

Analysis And Synthesis Of A Planar Reconfigurable Mechanism With A Variable Joint, Peter William Malak

Master's Theses (2009 -)

Currently, there is a demand for mechanisms with variable topology that can perform multiple tasks with the least amount of actuators. These devices have the ability to provide numerous motion profiles within one device. In the following thesis, a specific planar reconfigurable mechanism with a kinematic reconfigurable joint was mathematically modeled. This mechanism functions as a RRRP mechanism in one configuration and as a RRRR in the other and is known as a RRRR-RRRP Mechanism. The kinematics and kinetics of the RRRR-RRRP Mechanism were analyzed with a Lagrangian approach. The models are simulated and verified using a trajectory planner and ...


On The Importance Of Displacement History In Soft-Body Contact Models, Jonathan A. Fleischmann, Radu Serban, Dan Negrut, Paramsothy Jayakumar Jul 2016

On The Importance Of Displacement History In Soft-Body Contact Models, Jonathan A. Fleischmann, Radu Serban, Dan Negrut, Paramsothy Jayakumar

Mechanical Engineering Faculty Research and Publications

Two approaches are commonly used for handling frictional contact within the framework of the discrete element method (DEM). One relies on the complementarity method (CM) to enforce a nonpenetration condition and the Coulomb dry-friction model at the interface between two bodies in mutual contact. The second approach, called the penalty method (PM), invokes an elasticity argument to produce a frictional contact force that factors in the local deformation and relative motion of the bodies in contact. We give a brief presentation of a DEM-PM contact model that includes multi-time-step tangential contact displacement history. We show that its implementation in an ...


Analytical Modeling Of A Novel Microdisk Resonator For Liquid-Phase Sensing: An All-Shear Interaction Device (Asid), Mohamad Sadegh Sotoudegan Jul 2016

Analytical Modeling Of A Novel Microdisk Resonator For Liquid-Phase Sensing: An All-Shear Interaction Device (Asid), Mohamad Sadegh Sotoudegan

Dissertations (2009 -)

Extensive research on micro/nanomechanical resonators has been performed recently due to their potential to serve as ultra-sensitive devices in chemical/biosensing. These applications often necessitate liquid-phase sensing, introducing significant fluid-induced inertia and energy dissipation that reduces the resonator’s performance. To minimize the detrimental fluid effects on such devices, a novel microdisk resonator supported by two tangentially-oriented, axially-driven “legs” is investigated analytically and effects of the system parameters on the resonator/sensor performance are explored. Since the device surface vibrates primarily parallel to the fluid-structure interface, it is referred to here as an “all-shear interaction device,” or ASID. Analytical ...


Effect Of Original Layer Thicknesses On The Interface Bonding And Mechanical Properties Of Ti-Al Laminate Composites, Minyu Fan, Joseph P. Domblesky, Kai Jin, Liang Qin, Shengqiang Cui, Xunzhong Guo, Naksoo Kim, Jie Tao Jun 2016

Effect Of Original Layer Thicknesses On The Interface Bonding And Mechanical Properties Of Ti-Al Laminate Composites, Minyu Fan, Joseph P. Domblesky, Kai Jin, Liang Qin, Shengqiang Cui, Xunzhong Guo, Naksoo Kim, Jie Tao

Mechanical Engineering Faculty Research and Publications

It is of great significance in high-temperature aeroengine applications for large-surface-area TiAl laminate composites to be fabricated into Ti-Al3Ti parts by plastic forming and subsequent vacuum hot pressing. Then the original layer thicknesses have an important influence on the interface bonding and mechanical properties of TiAl laminate composites, but only few reports about it have been published so far. In the present study, vacuum hot pressing was employed to fabricate TiAl laminate composites using Ti and Al foils of different thickness. The resulting interface bond and mechanical properties of TiAl laminate composites were then studied to determine the ...


Application Of A Multi-Zone Model For The Prediction Of Species Concentrations In Rapid Compression Machine Experiments, David Wilson Apr 2016

Application Of A Multi-Zone Model For The Prediction Of Species Concentrations In Rapid Compression Machine Experiments, David Wilson

Master's Theses (2009 -)

Accurate chemical kinetic models, which predict species evolution and heat release rates in chemically reactive systems, are essential for further advancements in fuel and combustion technology. An experimental facility that is widely used for evaluating the accuracy of kinetic models is a rapid compression machine (RCM), which creates a well-defined reaction environment by compressing a reactive mixture inside a chamber. Generally, RCM experiments are conducted in order to obtain ignition delay data. However, chemical speciation data provides greater insight into reaction pathways, and is therefore a more rigorous benchmark for validating kinetic models. In order for a chemical kinetic model ...


Ramifications Of Projectile Velocity On The Ballistic Dart Penetration Of Sand, Peter Anthony Sable Apr 2016

Ramifications Of Projectile Velocity On The Ballistic Dart Penetration Of Sand, Peter Anthony Sable

Master's Theses (2009 -)

With the advent of novel in-situ experimental measurement techniques, highly resolved quantitative observations of dynamic events within granular media can now be made. In particular, high speed imagery and digital analysis now allow for the ballistic behaviors of sand to be examined not only across a range of event velocities but across multiple length scales. In an attempt to further understand the dynamic behavior of granular media, these new experimental developments were implemented utilizing high speed photography coupled with piezo-electric stress gauges to observe visually accessible ballistic events of a dart penetrating Ottawa sand. Projectile velocities ranged from 100 to ...


Modeling And Investigation Of Refrigeration System Performance With Two-Phase Fluid Injection In A Scroll Compressor, Rui Gu Apr 2016

Modeling And Investigation Of Refrigeration System Performance With Two-Phase Fluid Injection In A Scroll Compressor, Rui Gu

Master's Theses (2009 -)

Vapor compression cycles are widely used in heating, refrigerating and air-conditioning. A slight performance improvement in the components of a vapor compression cycle, such as the compressor, can play a significant role in saving energy use. However, the complexity and cost of these improvements can block their application in the market. Modifying the conventional cycle configuration can offer a less complex and less costly alternative approach. Economizing is a common modification for improving the performance of the refrigeration cycle, resulting in decreasing the work required to compress the gas per unit mass. Traditionally, economizing requires multi-stage compressors, the cost of ...