SELECTION OF APPROPRIATE FLUID DELIVERY TECHNIQUE FOR GRINDING TITANIUM GRADE-1 USING THE ANALYTIC HIERARCHY PROCESS

<p class="abstract">Grinding is commonly used in industry for the finishing or semi-finishing of different mechanical components. In this process, a wheel is rotated at a high speed. The wheel is made of abrasive particles known as grits. During grinding, high grinding zone temperature is experienced leading to several grinding defects. To control these thermal defects grinding fluid is usually employed mainly to cool and lubricate the grinding region. However, most of the applied grinding fluid cannot reach the grinding zone as it is deflected by the stiff air layer formed around the wheel periphery. Several attempts have been made in the past to overcome this problem in order to guarantee better fluid delivery. In this paper, two newly developed methods, a pneumatic barrier and a compound nozzle are considered to serve this purpose. Grinding experiments are conducted on titanium grade-1 specimens under four environmental conditions, which include dry, flood cooling, flood cooling with pneumatic barrier set up and cooling using a compound nozzle. Under each environment, 10 grinding passes are undertaken using 10, 20 and 30 mm infeed. Data obtained are used to optimize the grinding performance by employing the Analytic Hierarchy Process (AHP). The AHP results show compound nozzle fluid delivery at 20 mm infeed to be the appropriate condition for grinding titanium grade-1 within this experimental domain. This condition is supposed to deliver grinding fluid deep into the grinding zone thereby controlling grinding temperature effectively and may be recommended to the industry. </p>

Methodology for the Evaluation of Double-Layered Microcapsule Formability Zone in Compound Nozzle Jetting Based on Growth Rate Ratio

Double-layered microcapsules, which usually consist of a core (polymeric) matrix surrounded by a (polymeric) shell, have been used in many industrial and scientific applications, such as microencapsulation of drugs and living cells. Concentric compound nozzle-based jetting has been favored due to its efficiency and precise control of the core-shell compound structure. Thus far, little is known about the underlying formation mechanism of double-layered microcapsules in compound nozzle jetting. This study aims to understand the formability of double-layered microcapsules in compound nozzle jetting by combining a theoretical analysis and numerical simulations. A linear temporal instability analysis is used to define the perturbation growth rates of stretching and squeezing modes and a growth ratio as a function of the wave number, and a computational fluid dynamics (CFD) method is implemented to model the microcapsule formation process in order to determine the good microcapsule forming range based on the growth ratio curve. Using a pseudobisection method, the lower and upper bounds of the good formability range have been determined for a given materials-nozzle system. The proposed formability prediction methodology has been implemented to model a water-poly (lactide-co-glycolide) (PLGA)-air compound jetting system.

Study of Double-Layered Microcapsule Formation in Compound Nozzle Jetting

Double-layered microcapsules, which usually consist of a core (polymeric) matrix surrounded by a (polymeric) shell, have been used in many industrial and scientific applications such as microencapsulation of drugs and living cells. Compound concentric nozzle-based jetting has been favored due to its efficiency and precise control of the core-shell compound structure. Thus far, little is known about the underlying formation mechanism of double-layered microcapsules in compound nozzle jetting. This study aims to understand the formability of double-layered microcapsules in compound nozzle jetting by coupling a theoretical analysis with numerical simulations. A linear temporal instability analysis is used to define the perturbation growth rate and its ratio as a function of the wavenumber; and a computational fluid dynamics (CFD) method is implemented to model the microcapsule formation process in order to determine the good microcapsule forming range based on the growth ratio curve. Using a pseudo-bisection method, the lower and upper bounds of the good formability range have been determined for a given materials-nozzle system. The proposed formability prediction methodology has been implemented and validated in modeling a water-poly (lactide-co-glycolide) (PLGA) – air compound jetting system with satisfactory prediction results.

Primary Atomization and Spray Analysis of Compound Nozzle Gasoline Injectors

This work addresses primary atomization modeling, multidimensional spray prediction, and flow characteristics of compound nozzle gasoline injectors. Compound nozzles are designed to improve the gasoline spray quality by increasing turbulence at the injector exit. Under the typical operating conditions of 270-1015 kPa, spray atomization in the compound nozzle gasoline injectors is mainly due to primary atomization where the flow turbulence and the surface tension are the dominant factors. A primary atomization model has been developed to predict the mean droplet size far downstream by taking into account the effect of turbulent intensity at the injector exit. Two multidimensional spray codes, KIVA-2 and STAR-CD, originally developed for high-pressure diesel injection, are employed for the lower-pressure gasoline injection. A separate CFD analysis was performed on the complex internal flows of the compound nozzles to obtain the initial and boundary conditions for the spray codes. The TAB breakup model used in KIVA-2 adequately facilitates the atomization process in the gasoline injection.