Nozzle Chamber Research Articles

Technological Change from Analog to Digital

Abstract: Brusoni, Prencipe, and Pavitt (2001) posited that the digitization of aircraft engine control systems in the early 1980s caused loose organizational coupling. During this period, the number of control parameters indeed increased significantly with the introduction of full authority digital engine control (FADEC). However, during the period categorized by Brusoni et al. (2001) as the (analog) generation, digital technologies such as analog electronic and supervisory controls were gradually introduced. Moreover, with regard to technological changes in aircraft turbofan engines and control systems, technological improvements in engine power systems were evident in the 1960s and 1970s in terms of the bypass ratio, overall pressure ratio, and turbine inlet temperature. Although engine power systems witnessed negligible technological innovation in the 1980s, control systems improved as the number of control parameters increased due to the advent of FADEC. Subsequently, in the 1990s, great technological strides were made in engine power systems. Hence, technological changes in engine power systems and control systems always occurred alternately. Brusoni et al.'s claim that the decline in organizational coupling was due to the even rate of technological change in engines and control systems or the predictability in their interdependence miss the mark in light of the transition history of engine and control systems.Keywords: analog (hydromechanical), digital, aircraft engine control system, technological imbalance1. IntroductionBrusoni, Prencipe, and Pavitt (2001) categorized aircraft engine control systems from the 1950s to the 1970s as hydromechanical (analog) and those from the 1980s to the 1990s as digital. Brusoni et al. (2001) described the scope for change in the organizational structure and knowledge of three companies1 from the perspective of the evolution of control system technology. However, they barely mentioned the change in control system technology from analog to digital, nor did they focus on the changes in the engine power systems, which are associated with changes in control system technology. Referencing Brusoni et al.'s arguments, this study focuses on the transition of engine control systems from analog to digital and the associated technological changes in the power systems in order to review the technologies analyzed by Brusoni et al.2. Technological Change of Engine Control System:From Hydromechanical to DigitalBrusoni et al. (2001) focused on the control systems of aircraft turbofan and turbojet engines. A turbojet engine comprises an air intake, a fan/compressor, combustion chamber, turbine, afterburner, and tail nozzle. The pilot adjusts the position of the throttle lever to achieve the required thrust. The engine control system provides the necessary thrust by receiving the lever position as input and adjusting the fuel flow, thereby accelerating or decelerating the engine's revolutions per minute (RPM). Furthermore, it confirms whether the thrust corresponds with the pilot's intention and maintains the required thrust levels (Yoshinaka, 2010).Compared with the digital system, the analog system could control only a limited number of items. The following section discusses the evolution of jet engine control technologies based on Endoh (2004), Sugiyama (2004), Sono (2008), and Yoshinaka (2010).2.1. Hydromechanical controlThe jet engine was first adopted as a source of thrust in aircrafts in the 1930s. Simple mechanical fuel controls comprising cams and levers were used in reciprocating engines, which constituted the majority at the time. The control required by jet engines was comparatively complex, and the existing technology was inadequate. Even in the case of early post-war turbojet engines, variables of fuel flow or bleed valve could only be controlled. Subsequently, advances in the level of precision and miniaturization in the areas of mechanics and oil hydraulics led to progress in the control technologies of aircraft engines. …

Modeling of gas flow in the cylindrical channels of high-voltage plasma torches with rod electrodes

The article is devoted to the calculation of gas dynamic parameters of gas flow in various areas of low-temperature plasma generator, therefore, target area's grid was built for the simulation of plasma gas flow in channels of studied high-voltage AC plasma torches and calculations of three-dimensional gas flow was made using GAMBIT and FLUENT soft-ware and Spalart-Allmares turbulence model, air flow was simulated in the tangential feed's areas, in the cylindrical channel, in the tapering nozzle chamber and in the mixing chamber of plasma torches and outside (in the environment); thus, 3D-modelling of the cold plasma-forming gas flow was performed in cylindrical channels of studied high-voltage AC plasma torches with rod electrodes for the first time.

Study of low speed flow cytometry for diffraction imaging with different chamber and nozzle designs

Achieving effective hydrodynamic focusing and flow stability at low speed presents a challenging design task in flow cytometry for studying phenomena such as cell adhesion and diffraction imaging of cells with low-cost cameras. We have developed different designs of flow chamber and sheath nozzle to accomplish the above goal. A 3D computational model of the chambers has been established to simulate the fluid dynamics in different chamber designs and measurements have been performed to determine the velocity and size distributions of the core fluid from the nozzle. Comparison of the simulation data with experimental results shows good agreement. With the computational model significant insights were gained for optimization of the chamber design and improvement of the cell positioning accuracy for study of slow moving cells. The benefit of low flow speed has been demonstrated also by reduced blurring in the diffraction images of single cells. Based on these results, we concluded that the new designs of chamber and sheath nozzle produce stable hydrodynamic focusing of the core fluid at low speed and allow detailed study of cellular morphology under various rheological conditions using the diffraction imaging method.

Launch Dynamic Characteristic of High Initial Velocity Grenade Launcher with Low Recoil

In order to reduce the recoil of High Initial Velocity Grenade Launcher (HIVGL) and obtain better firing precision, two reduction recoil structures - short recoil barrel structure and laval nozzle structure were used for HIVGL. Virtual prototype simulation model of HIVGL were established, the dynamics curves of automatic mechanism of HIVGL and human shoulder force curves were obtained when HIVGL was launched by dynamic simulation software - ADAMS. The motion characteristics of automatic mechanism and the variation regulation of the maximum shoulder force were analyzed with different combinations of HIVGL structures and nozzle chamber charge amount. The barrel floating spring stiffness, pre-pressure and the effect of barrel stroke on spring energy storage were also analyzed. As proved by the research results, the maximum recoil of HIVGL can be greatly reduced by introducing short recoil barrel structure and laval nozzle structure. This result provides a beneficial reference for structure design and optimization of HIVGL.

Simulation of Airflow Motion in Jet Nozzle with Different Geometric Parameters

Jet nozzle with tangentially injected airflow has been applying into spinning technology due to the tangential force produced by swirling airflow. In order to understand the airflow motion trajectory in jet nozzle, modify the nozzle structure and dimension, FLUENT software program is used. Some parameters which are closely related the airflow motion profiles are studied, such as the diameter of nozzle chamber, the diameter and angle of the orifice. The results showed that the intensity of air swirling is more strong in a smaller nozzle chamber; a larger orifice diameter is helpful for producing strong yarn and improving production efficiency, but it requires a larger nozzle chamber, therefore, a reasonable rate of orifice and nozzle chamber diameter is important; as the orifice angle increases, the tangential velocity decreases, which decreases the intensity of airflow swirling, and a small orifice angle will cause a larger reverse jet, which is bad to draw the fibers into the nozzle.

A Modular Explosive Ordnance Disposal Disrupter System

This work describes a recently-patented modular explosive ordinance disposal (EOD) disrupter system (also called MODS). The MODS replicates three caliber .50 disrupters currently used by EOD teams of all military services in the United States. Having a design that includes interchangeable tubes, a muzzle nozzle and a chamber nozzle, the MODS has the capacity to launch 1” metal slugs, 1” water slugs and 40mm fin-stabilized slugs.

Effects of superheat on characteristics of flashing spray and snow particles produced by expanding liquid carbon dioxide

This research experimentally investigates influences of superheat on flashing spray characteristics and on the snow formation of liquid CO2. Results show that liquid, two-phase flow or even three-phase flow can be found upon the release of liquid CO2 from high pressure to atmospheric pressure. This is due to complicated phase transition processes that involve hydrodynamic instabilities and thermal non-equilibrium conditions. Results also show that the spray pattern transfers from jet spray to cone spray, and then to a bowl spray configuration with the increase of superheat. The drastic changes in spray angle and mass flow rate indicate onset conditions from external-flashing to internal-flashing atomization mode. This is due to bursts of bubbles inside the nozzle chamber that result in the choking of the two-phase flow. Moreover, a few microns of CO2 snow size are measured in this research, which is consistent with records from literature on this topic. The narrower size distribution of snow particles and a critical spray angle resulting from two competing phenomena under internal-flashing atomization mode are also discussed in this research.

喷雾腔压力及喷嘴孔径对相变喷雾冷却性能的影响

喷雾腔压力及喷嘴孔径对相变喷雾冷却性能的影响

Continuous nanofiber yarns twisted through three-dimensional high-speed swirling airflow

A new method is proposed to fabricate continuous twisted nanofiber yarns. Nanofibers are bunched by a double conjugate electrospinning, and then twisted through a three-dimensional high-speed swirling airflow. Its principle and process are analyzed theoretically, and the airflow field inside the nozzle chamber is studied numerically, and mechanical properties of nanofiber yarns at different spinning conditions are systematically discussed.

Boundary element analysis of the droplet dynamics induced by spark-generated bubble

Abstract Spark bubble droplet generation (SBDG) method is the most recently developed drop-on-demand droplet generation technique where the oscillation of a spark-generated bubble near a circular aperture causes a single droplet quite smaller than the aperture to form and break off. This paper investigates the fluid dynamics of the droplet generated through a flat plate aperture as well as through the nozzle of an axisymmetric chamber using boundary element method and high-speed photography. The results revealed that the bottom wall of the chamber would strongly influence the behavior of the bubble oscillating inside. In addition, it was found that with the same normalized nozzle size and bubble distance from air–liquid interface, a relatively smaller and faster droplet is generated from the chamber nozzle as compared with that formed through the flat plate aperture. Furthermore, although the droplet size decreases, its pinch-off time was found to increase by increasing the size of chamber feeder canal.

Physical model of fluid flow characteristics in RH-TOP vacuum refining process

To understand the characteristic of circulation flow rate in 250-t RH-TOP vacuum refining process, the l:4 water model test was established through the bubble behavior and gas holdup in the up-leg to investigate the effects of different processes and equipment parameters on the RH circulation flow rate. With the increases of lifting gas flow rate, lifting bubble travel, and the internal diameter of the up-leg, and the decrease of nozzle diameter, the work done by bubble floatage and the circulation flow rate increase. The expression of circulation flow rate was derived from the regression analysis of experiment data. Meanwhile, the influences of vacuum chamber pressure and nozzle blockage situation on the circulation flow rate were discussed in detail by the bubble behavior and gas holdup in the up-leg. It is necessary to maintain a certain vacuum chamber liquid level in the molten steel circulation flow. Compared with a nozzle with symmetrical blockage in the up-leg, when a nozzle with non-symmetrical blockage is applied, the lifting gas distribution is non-uniform, causing a great effect on the molten steel circulation flow and making the circulation flow drop largely.

Parametric investigation of the pintle-perturbed conical nozzle flows

Thrust variation, flow structures and geometric factors of pintle-perturbed conical nozzle are studied experimentally and numerically under the condition of constant mass flow rate. Regulators and choking orifice are installed for constant mass flow rate and static pressure distributions along the nozzle wall, chamber pressure and thrust are measured. In order to prevent transfer of non-linear load to the load cell by the flexible tubes, the load cell for thrust measurement is calibrated. Roeʼs flux-difference splitting scheme is applied to resolve the flow discontinuities such as the lip shock, trailing shock and oblique shock typical in the pintle-perturbed nozzle flows. Three different turbulent models of k–ε, k–ω SST and Spalart–Allmaras are examined to assess their validity for resolving the turbulence. The predicted thrust by empirical method, which includes influence of deliverable thrust coefficient by flow separation, showed good agreement with measured thrust at the minimum and maximum throat area. Spalart–Allmaras model and k–ω SST model showed good agreement with experiment on predicting the thrust especially in the case that the flow separation occurs in the nozzle diverging section, and the Spalart–Allmaras model predicted wall separation point more accurately than the other models. Shock impinging point and the flow separation point induced by shock wave separation occur and move in the nozzle flow as the pintle inserted into the nozzle throat. Because, the dominant factor which determines thrust is chamber pressure, the pintle shape must be considered essentially in view of minimizing the force acting on the pintle.

Influence of the inlet channel flow of a steam turbine on solid particle erosion of the control stage nozzles

Based on experiments and numerical simulation, the influence of the inlet flow channel of a steam turbine on the solid particle erosion of nozzle segments was investigated systematically. The results indicate that the upstream channels of the nozzle segment, such as the regulating valve, nozzle chamber and connection pipe, concentrate the solid particle erosion to a small number of nozzles or local regions of the nozzle, which greatly reduces the time for nozzle damage. Compared with the present erosion situation, measures adopted to distribute particles at the inlet of a nozzle chamber uniformly can double the service life of a nozzle segment, while the service life can be increased by eight to ten times through measures to distribute particles uniformly at the inlet of a nozzle segment. This article shows that the service life of a nozzle segment can be doubled through substituting a nozzle chamber with a tangential steam intake for one with a normal steam intake. Moreover, a boride layer with 0.04 mm effective thickness or a CrN layer with 0.01 mm effective thickness can further double the service life of a nozzle segment. In addition, a pocket-trap arranged in the particle-aggregated area after an elbow can reduce the weight loss at nozzle sites with the most serious erosion by over 85%. These investigations are of great significance to the long-term, safe and high-efficiency running of a steam turbine.

Automated MALDI Matrix Coating System for Multiple Tissue Samples for Imaging Mass Spectrometry

Uniform matrix deposition on tissue samples for matrix-assisted laser desorption/ionization (MALDI) is key for reproducible analyte ion signals. Current methods often result in nonhomogenous matrix deposition, and take time and effort to produce acceptable ion signals. Here we describe a fully-automated method for matrix deposition using an enclosed spray chamber and spray nozzle for matrix solution delivery. A commercial air-atomizing spray nozzle was modified and combined with solenoid controlled valves and a Programmable Logic Controller (PLC) to control and deliver the matrix solution. A spray chamber was employed to contain the nozzle, sample, and atomized matrix solution stream, and to prevent any interference from outside conditions as well as allow complete control of the sample environment. A gravity cup was filled with MALDI matrix solutions, including DHB in chloroform/methanol (50:50) at concentrations up to 60mg/mL. Various samples (including rat brain tissue sections) were prepared using two deposition methods (spray chamber, inkjet). A linear ion trap equipped with an intermediate-pressure MALDI source was used for analyses. Optical microscopic examination showed a uniform coating of matrix crystals across the sample. Overall, the mass spectral images gathered from tissues coated using the spray chamber system were of better quality and more reproducible than from tissue specimens prepared by the inkjet deposition method.

Characteristics of Carbon Nanotubes Based Micro-Bubble Generator for Thermal Jet Printing

We propose a conceptional thermal printhead with dual microbubble generators mounted parallel in each nozzle chamber, where multiwalled carbon nanotubes are adopted as heating elements with much higher energy efficiency than traditional approaches using noble metals or polysilicon. Tailing effect of droplet can be excluded by appropriate control of grouped bubble generations. Characteristics of the corresponding micro-fabricated microbubble generators were comprehensively studied before the formation of printhead. Electrical properties of the microheaters on glass substrate in air and performance of bubble generation underwater focusing on the relationships between input power, device resistance and bubble behavior were probed. Proof-of-concept bubble generations grouped to eliminate the tailing effect of droplet were performed indicating precise pattern with high resolution could be realized by this kind of printhead. Experimental results revealed guidance to the geometric design of the printhead as well as its fabrication margin and the electrical control of the microbubble generators.

Exergetic Destruction Effects of Operating Conditions on the Turbojet Engine Components

The minimization of exergy destruction brings the design as closely as permissible to the theoretical limit. This study presents exergy destruction analysis of a turbojet engine for different flight Mach number and altitudes. Turbojet engine being considered consists of an inlet, a centrifugal compressor, reverse flow combustion chamber, axial-flow turbine and exhaust nozzle. The flight Mach number and altitude are examined on the exergetic destructions of compressor, combustion chamber, turbine and exhaust nozzle. The results of component-based destruction analysis are given as three dimensional exergetic-destruction response surface plots related to altitude and flight Mach number.

Exergetic and Energetic Response Surfaces for Small Turbojet Engine

Exergy analysis permits meaningful efficiencies to be evaluated for a system or process, and the sources, causes and locations of thermodynamic losses to be determined. This study presents exergetic modeling of a small turbojet engine via exergetic response surfaces. Turbojet engine consists of an inlet, a centrifugal compressor, reverse flow combustion chamber, axial-flow turbine and exhaust nozzle. The flight Mach number and altitude are examined on the exergetic efficiencies of total engine performance. The results of analysis are given as three dimensional exergetic response surface plots related to these operating parameters.

Investigation on the Dynamic Behavior of the Fiber in the Vortex Spinning Nozzle and Effects of Some Nozzle Structure Parameters

Vortex spinning, which adopts high speed airflow to insert twist into the yarn, is one of the most promising technological innovations in the textile industry. In vortex spinning, the dynamic behavior of the fiber inside the nozzle, which involves fiber-airflow interaction and fiber-wall contact, plays an important role in the twist insertion process. This paper investigates the airflow characteristics and the fiber dynamic behavior inside the vortex spinning nozzle via a two-dimensional numerical model with the fiber-airflow interaction and fiber-wall contact included. The fiber is assumed to be isotropic, elastic material. The airflow inside the nozzle is assumed to be turbulent, viscous and incompressible. The numerical results show that two vortices with momentarily changed sizes are created upstream of the jet orifice outlets. The imbalance of the pressure around the fiber causes the fiber to move and deform. The trailing end of the fiber rotates with wave shape within the nozzle chamber for several periods to insert twist into the yarn. Based on the model, the effects of three nozzle structure parameters – the jet orifice angle, jet orifice diameter, distance between the nozzle inlet and the hollow spindle, on the dynamic behavior of the fiber, and in turn, the yarn structure and tensile property are investigated. The results show that the appropriate jet orifice angle for obtaining the best yarn tenacity is 70°. The optimal jet orifice diameter is 0.4 mm. The spun yarn has the highest tenacity when the distance between the nozzle inlet and the hollow spindle is 14 mm.

Numerical simulation of fiber motion in the nozzle of Murata vortex spinning machine

In this paper, a two‐dimensional model for rationally describing the physical and mechanical characteristics of a flexible fiber is presented. The arbitrary Lagrangian–Eulerian technique is adopted to solve the fluid–structure interaction between the fiber and the airflow in the nozzle of a Murata vortex spinning (MVS) machine. The contact problem arising between the fiber and the nozzle wall is also solved. The motion and deformation of the fiber in the airflow inside the MVS nozzle are successfully simulated. The results show that with the action of the airflow, the fiber shows helical movement with wave shape. During its downstream motion, the fiber contacts the inner wall of the spindle frequently. The trailing end of the fiber whirls within the nozzle chamber with great amplitude. The separation and wrapping motion of the fiber take place and twists are inserted into the fiber strand before the trailing end of the fiber enters the spindle entirely. The intensity of the twists inserted into the yarn can be evaluated by the amplitude and the frequency of the periodical rotation of the trailing end of the fiber.

Research on Swirl-Core Nozzle with Adjustable Spray Angle Based on Vortex Theory

According to Vortex Theory, the fluid flow in a swirl-core nozzle was analyzed, and an equation of spray angle was presented. The fluid in this nozzle was simulated by Volume of Fluid Model through CFD. The fluid dynamic simulation results show that diameters of nozzle opening and swirl chamber, area of spiral groove, and helix angle of the spiral groove affect the spray angle. There are optimum structural parameters for a swirl-core nozzle, and the spray angle can be adjusted by changing the depth of the swirl chamber with fixed structural parameters of the nozzle.