DAKIN - WEST Acylation


From a moulder s viewpoint, then, the ideal wheel has an almost constant wall thickness, and no sharp corners. In place of spokes, the area between the hub and the rim can be made a solid web to give even flow of polymer to the rim and to avoid weld lines (places where polymer flowing down one channel meets polymer which has flowed down another). The wheel shown in Fig. 28.14 typifies this type of design. It replaces a die-cast part, saving both cost and weight. While the web is solid, axial stability is provided by the corrugated surface. The web is a better solution than ribs attached to a flat disc because the changes in section where the ribs meet the disc give shrinkage problems.  [c.310]

Resins of higher molecular weight demonstrate higher tensile strength, whereas high fumarate resins have higher flexural modulus. Formulations containing diethylene glycol and adipic acid produce resins that have higher residence reflected in enhanced tensile and flexural strength but lower flexural modulus. Isophthalic resins provide better mechanical properties than OfXv o-phthalic resins and are consequently preferred in laminate appHcations requiring higher stmctural performance. Resins that have exceptional tensile performance are formulated from the bisphenol A epoxy dimethacrylates. These resins demonstrate superior fracture resistance properties beneficial in filament-wound stmctures such as tanks and pipes, which ate subjected to cycHc stresses that can result in fatigue failure. The strength of all polyester resins is enhanced significantly by glass and other fibrous reinforcements. Laminates are usually fabricated from glass fiber mat, having individual fibers 5 cm in length. The stmctural properties increase in proportion to the glass fiber content, which can be varied from 25—40%. Increased reinforcement levels can be achieved by using woven glass roving in alternating pHes with chopped strand glass mat. Higher strength can be realized from continuous glass fiber rovings used in filament-wound stmctures in the form of pipes or tanks. Heflcal wind angles ate varied to achieve design requirements in hoop or axial directions a wind angle of 55° can generate twice the strength in the hoop direction. Continuous glass fiber roving used at reinforcement levels of 65% in pultmded products provides composites that have the highest flexural and tensile properties. Carbon fiber can be useful in developing composites that have higher modulus characteristics, but economics have reduced their wider attractiveness in combinations with polyester resins. Kevlar cloth can be used in combination with bisphenol epoxy dimethacrylates to produce light weight, high strength composite plastics for spotting equipment such as kayaks and skis.  [c.320]

The gas turbine was designed shortly after World War II and introduced to the market in the early 1950s. The early heavy-duty gas turbine design was largely an extension of steam turbine design. Restrictions of weight and space were not important factors for these ground-based units, so the design characteristics included heavy-wall casings split on horizontal centerlines, hydrodynamic (tilting pad) bearings, large-diameter combustors, thick airfoil sections for olades and stators, and large frontal areas. The overall pressure ratio of these units varied from 5 1 for the earlier units to 30 1 for the units in the 1990s. Turbine inlet temperatures have been increased and run as high as 2300° F (1260° C) on some of these units. Projected temperatures approach 3000° F (1649° C) and, if achieved, would make the gas turbine even more efficient. The industrial heavy-duty gas turbines most widely used employ axial-flow compressors and turbines. In most U.S. designs combustors are can-annular combustors. Single-stage side combustors are used in European designs. The combustors used in industrial gas turbines have heavy walls and are veiy durable.  [c.2507]

Striving for improved energy usage, refiners eurrently favor axial flow eompressors for the FCC proeess. Axials are physieally smaller and lighter weight than eorresponding eentrifugals. Flowever, sinee only relatively small pressure ratios per stage are attainable, axials for FCC applieations typieally eonsist of 9-13 stages, depending on regenerator pressure requirements. With eonstant speed operation to deliver eonstant mass flow at eonstant diseharge pressure with varying ambient temperatures, approximately half of the stationary blades are made adjustable. A more vertieal pressure rise is typieal of axial flow eompressors. Constant pressure flow turndown to about 75% of design flow is possible with only modest effieieney deeay (Figure 4-104). The operating eharaeteristies of axial eompressors ean be tailored to meet proeess needs and ean provide operating effieieneies up to 12% higher dian obtainable with typieal eentrifugal eompressors. Axial flow units are also readily matehed to optimum speeds for turbines and power reeovery expanders.  [c.211]

Loads ean be both internal and external. They ean be due to weight, meehanieal forees (axial tension or eompression, shear, bending or torsional), inertial forees, elee-trieal forees, metallurgieal forees, ehemieal or biologieal effeets due to temperature, environmental effeets, dimensional ehanges or a eombination of these (Carter, 1986 Ireson et al., 1996 Shigley and Misehke, 1989 Smith, 1976). In faet some environments may impose greater stresses than those in normal operation, for example shoek or vibration (Smith, 1976). These faetors may well be as important as any load in eonventional operation and ean only be formulated with full knowledge of the intended use (Carter, 1986). Additionally, many meehanieal systems have a duty eyele whieh requires effeetively many applieations of the load (Sehatz et al., 1974), and this aspeet of the loading in serviee is seldom refleeted in the design ealeu-lations (Bury, 1975).  [c.167]

Frequently, no visible smoke and no carbon deposition are design parameters. Smoke is an environmental concern, while excessive carbon can impair the fuel spray quality and cause higher liner temperatures due to the increased radiation emissivity of the carbon particles as compared to the surrounding gases. Smoke and carbon are a fuel-related property. The hydrogen saturation influences smoke and free carbon. The less-saturated fuels like benzene (CglTg) tend to be smokers the better fuels like methane (CH4) are saturated hydrocarbons. This effect is shown in Figure 12-8. Boiling temperature is a function of molecular weight. Heavier molecules tend to boil at a higher temperature. Since a less-saturated molecule will weigh more (higher molecular weight), one can expect residuals and heavy distillates to be smokers. This expectation is founded in practice. The design solution pioneered by General Electric on its EM 2500, which has an annular combustor as shown in Figure 12-9, was to increase flow and swirl through the dome surrounding the fuel injector. The increased flow helped to avoid rich pockets and promoted good mixing. The axial swirler achieved a no-smoke condition and reduced liner temperature.  [c.452]

The last column in Tables 4-110 and 4-111 show the thrust load associated with each circulation floWrate (i.e.,-pressure drop). This thrust load is the result of the pressure drop across the turbine motor rotor and stator blades. -The magnitude. of this pressure drop, depends. on the individual internal design details of the turbine motor (i.e., blade angle, number of stages, axial height of blades and The radial width of the blades) and the operating conditions. The additional pressure. drop results in thrust, T (lb), whicit is  [c.873]


See pages that mention the term DAKIN - WEST Acylation : [c.246]   
Organic syntheses based on name reactions and unnamed reactions (1994) -- [ c.84 ]