Valve Research Papers - Academia.edu (original) (raw)

The four stroke, spark ignition (SI) engine pressure–volume diagram (p–V) contains two main parts. They are the compression–combustion–expansion (high pressure loop) and the exhaust-intake (low pressure or gas exchange loop) parts. The... more

The four stroke, spark ignition (SI) engine pressure–volume diagram (p–V) contains two main parts. They are the compression–combustion–expansion (high pressure loop) and the exhaust-intake (low pressure or gas exchange loop) parts. The main reason for efficiency ...

This article considers the configuration of modular and temporary organization designs. By drawing on two prominent developer firms, namely,Valve Inc. and Linden Lab, respectively,“cabals” and “studios” are explored.The results of... more

This article considers the configuration of modular and temporary organization designs. By drawing on two prominent developer firms, namely,Valve Inc. and Linden Lab, respectively,“cabals” and “studios” are explored.The results of interviews conducted with employees of these firms are used as evidence. The article demonstrates that, to various extents, these organization designs organize, facilitate, and maintain how work is accomplished and coordinated within the boundaries of a permanent firm. It extends our understanding of how these designs provide a structure to how tasks are constituted in conjunction with the nature of the product.

Although stuffing boxes are old systems used to ensure stem valve sealing, the analytical developments of the stresses and the displacements generated during assembly and operation are very limited and seldom verified and the studies... more

Although stuffing boxes are old systems used to ensure stem valve sealing, the analytical developments of the stresses and the displacements generated during assembly and operation are very limited and seldom verified and the studies carried out on these devices are either restricted or not accessible. Moreover, even with the evolution of calculation and simulation means, studies based on numerical

This paper explores the controlling characteristics of a first-principles model-based controller specially developed for vapor compression refrigeration systems. Mathematical sub-models were put forward for each of the system components:... more

This paper explores the controlling characteristics of a first-principles model-based controller specially developed for vapor compression refrigeration systems. Mathematical sub-models were put forward for each of the system components: heat exchangers (condenser and evaporator), variable-speed compressor and variable-orifice electric expansion device. The dynamic simulation model was then used to design a multivariable controller based on the linear-quadratic-Gaussian technique using a Kalman filter for the estimator design. A purpose-built testing apparatus comprised of a variable-speed compressor and a pulse-width modulated expansion valve was used to collect data for the system identification, and model and controller validation exercises. It was found that the model reproduces the experimental trends of the working pressures and power consumption in conditions far from the nominal point of operation (±30%) with a maximum deviation of ±5%. Additional experiments were also performed to verify the ability of the controller of tracking reference changes and rejecting thermal load disturbances. It was found that the controller is able to keep the refrigeration system running properly when the thermal load was changed from 340 to 580 W (460 W nominal), and the evaporator superheating degree was varied from 9.5 °C to 22 °C (16.6 °C nominal).

In this article it is sought to deal with the flow analysis of base valve designs for twin tube shock absorbers. To obtain the valves, a top down approach was adopted and an existing shock absorber was torn down. The base valve of the... more

In this article it is sought to deal with the flow analysis of base valve designs for twin tube shock absorbers. To obtain the valves, a top down approach was adopted and an existing shock absorber was torn down. The base valve of the same was obtained and reverse engineered. Coordinate acquisition was done for the various parts using a Coordinate Measuring Machine (CMM). Flow analysis was carried out using FLUENT integrated into ANSYS Workbench 15.0 on solid models of the base valve generated using PTC Creo 2.0. The results show that the velocity of the fluid in the system allows the system enough time for the fluid in the reserve chamber to enter the compression chamber of the pressure tube preventing aeration of the fluid. The results also show that the net forces acting on the system generate stresses lower than the yield strength of the material (structural Steel) used. The flow of the hydraulic fluid (SAE20W) is such that enough energy is dissipated by the system for effective damping to take place without raising the temperature of the hydraulic fluid beyond its auto ignition temperature hence validating the design in tune with its application in a automobile shock absorber.

In present study, A spark ignition and a compression ignition engine with uniflow valve scavenging of the cylinder and a transfer valve in the piston crown have been described. A great disadvantage of two-stroke engines is ports which are... more

In present study, A spark ignition and a compression ignition engine with uniflow valve scavenging of the cylinder and a transfer valve in the piston crown have been described. A great disadvantage of two-stroke engines is ports which are made in the cylinder bearing surface. Under the heat which is realised during the combustion, the thermal extension of the range in proximity of the ports and other parts of the cylinder is different and so the distortion of the geometry of the cylinder liner surface force the designer to make the clearance between the piston and the cylinder liner bigger. This paper presents the critical review to study the effect of fuel injection timing and scavenging using diesel on the combustion and emission characteristics of a single cylinder, two stroke, air cooled direct injection diesel engine. It is well known that injection strategies including the injection timing and pressure play the most important role in determining engine performance, especially in scavenging emissions. However, the injection timing and pressure quantitatively affect the performance of the diesel engine.

Assemblance of bivalve and univalve molluskan shells occur due to the eustatic and tectonic changes as well as by coastal hazards. They are a geoscientitic tool in the study of former sea-levels. Along the southern coast of Sri Lanka, the... more

Assemblance of bivalve and univalve molluskan shells occur due to the eustatic and tectonic changes as well as by coastal hazards. They are a geoscientitic tool in the study of former sea-levels. Along the southern coast of Sri Lanka, the bulk of the shell valves on the "Dry Zone" between Tangalle and Bundala have been piled up by severe storm wave action on mounds, in lagoon and lake bottoms, on sand dunes and headlands. Furthermore, the shell valves of lagoon, lake and channel beds (floors of marine and brackish pools) mostly accumulated in situ due to the lowering of sea level. The deposition sequences of some shell patches of the mounds at Udamalala and on dune deposits help to infer that the valves have been discarded by early inhabitants and animals. The stratigraphy of the shell deposits had been intermittently covered by vast quantities of coral and/or shelly sand and various types of debris moved by severe monsoon waves. The colour and the materials of the shell l...

One of the major consequences of climate change is the increase of ultraviolet radiation, especially UVB (280-315 nm). This has important consequences for organisms and ecosystems. In surface freshwater ecosystems with transparent water,... more

One of the major consequences of climate change is the increase of ultraviolet radiation, especially UVB (280-315 nm). This has important consequences for organisms and ecosystems. In surface freshwater ecosystems with transparent water, UV can easily penetrate deeply. Here, we used three different experimental approaches to examine the response of non-marine ostracods and cladocerans to UVB radiation: estimating lethal doses, determining how much UVB is blocked by the valves, and analysing valve chemical compositions. For most investigated crustaceans, we found a strong correlation between the amount of UVB that is blocked by the valves and the lethal UVB doses. Most ostracod valves blocked between 60% and 80% of UVB radiation, thus providing effective shielding. Pigmented species from temporary habitats were best protected. These species also showed high lethal UVB doses of 110 kJ m 2 to 214 kJ m 2. In the waterflea Daphnia magna, valves only stopped ca 35% of UVB radiation, and t...

Objective: Pulmonary regurgitation is the predominant problem in the long-term follow-up of tetralogy of Fallot (TOF) patients after primary repair. Apart from standard homograft implantation, a percutaneous valve delivery approach has... more

Objective: Pulmonary regurgitation is the predominant problem in the long-term follow-up of tetralogy of Fallot (TOF) patients after primary repair. Apart from standard homograft implantation, a percutaneous valve delivery approach has been described recently. A right ventricular outflow tract (RVOT) diameter of greater than 22mm, however, precludes percutaneous valve delivery. We describe a novel technique with a transventricular implantation of