Structured Porous Material Design for Passive Flow and Noise Control of Cylinders in Uniform Flow

Cylindrical bodies in uniform flows can be coated with a porous medium as a passive flow and noise control method in an effort to reduce the acoustic effects of vortex shedding. To date, the employed open-cell porous materials typically possess a randomized internal structure. This paper presents the design and validation of a novel 3-D printed structured porous coated cylinder that has significant flexibility, in that the porosity and pores per inch of the porous coating can be modified independently and relatively easily. The performance of the structured porous coating design is compared against porous polyurethane and metal foam with the same coating dimensions and similar pores per inch and porosity via an experimental acoustic investigation, revealing strong similarity in the passive noise control performance of each material type. A numerical comparison illustrates the similarities of the wake structure of the 3-D printed porous coated cylinder to an equivalent Darcy–Forchheimer model simulation that represents a randomized internal porous structure. The performance similarities of these different porous material types indicate that a structured porous geometry can be used to understand the internal flow behavior of the porous medium responsible for reducing the cylinder vortex shedding tone that is otherwise extremely difficult or impossible with typical randomized porous structures. Moreover, significant potential exists for the porous structure to be further optimized or smartly tailored by architectural design for different control purposes, coating geometries and dimensions, and working conditions.

Performance and Emission Characteristics of Diesel Engine Using Thermal Barrier Coated Cylinder Liner and Piston

Improvement in thermal efficiency and reduction in emission from diesel engines are major thrust research work in all around the world. This research work is on the performance and emission characteristics of diesel engine using Low Heat Rejection (LHR) techniques of thermal barrier coated cylinder liner and piston. A piston was coated as 100 micron thickness and three cylinder liners were coated in the thickness of 100,150 and 200 micron. Piston and cylinder liners were coated with equal percentages of Alumina and Yittria Stabilized Zirconia powder using the plasma spraying coating method. The test results compared with base engine showed reduction in the performance parameter of specific fuel consumption (SFC) on an average by 6.11%, 12.78% and 16.89%, while the brake thermal efficiency increased by 1.68%,3.75% and 5.19% in 100,150 and 200 micron thickness coated cylinder liner used engine respectively. There was reduction in Carbon monoxide (CO), unburned hydrocarbon (HC) and smoke emissions levels while Nitrogen Oxide (NOx) emission was slightly higher in the coated engine compared with the uncoated engine in all load conditions. Overall, 200 microns thickness coated cylinder liner showed a better performance parameter and low emission compared with other cylinder liner coated engine.