Projects and Publications

Vertical Axis Wind Turbines

Vertical Axis Wind Turbines (VAWT) have great potential for suburban applications because of their easiness of installation and low maintenance cost. Due to low installation height, VAWT is limited to operate at lower wind speed environments and they have a tendency to stall under gusty winds. Active blade pitch and camber control by incorporating controllable flaps at the trailing edges of blades have been proposed for improving VAWT’s efficiency, and experimental tests have shown promising results.
A systematic Finite Element Method (FEM) based computational fluid dynamics (CFD) numerical analysis will be conducted to study how the following three parameters would affect efficiency of individual blade with trailing edge flap as well as VAWT systems: (i) pitching pattern of individual blades in a VAWT system consisting multi-blades; (ii) pivoting pattern of the flaps at the trailing edges of individual blade; (iii) size of trailing edge flap. The ultimate goal is to find an optimized blade control profile so that low cost mechanism can be developed to control the blades for maximum efficiency.

Physical to mathematical model:

FEM model based on COMSOL:

FEM simulation results:

Evacuated Solar Thermal Collector

Single ended evacuated tubular solar thermal collectors are widely used in solar heating applications. Exchange and transfer of heat is accomplished by a thermosyphon process. The flow pattern of the working fluid within the collector is determined by a combination of gravity forces and the fluid's buoyancy forces which are due to varying density at varying temperature. This paper reports on a finite element method (FEM) based numerical study of the dependence of the working fluid flow pattern on the collector design and installation parameters. This fluid flow pattern determines the heat exchange between the working fluid and the selective coating and thus the efficiency of the collector. A solar water heating system made with five commercial evacuated tubular collectors was also built and tested to verify the simulation results. 

Physical to mathematical model:

FEM model based on COMSOL

Experimental tests and measurements

Powder Material Processing and Powder Metallurgy

Self-propagating High-temperature Synthesis (SHS) and Quasi-Isostatic Pressing (QIP)

In the attempt to achieve maximum densification and least distortion for near-net-shaped manufacturing, quasi-isostatic pressing (QIP) is studied. In QIP, self-propagating high-temperature synthesis (SHS) and subsequent consolidation are conducted in a rigid die where the SHS body is located at the center of the surrounding granular pressure-transmitting medium (PTM). Following the SHS, a uniaxial load is applied to the PTM, which builds up a quasi-isostatic stress in the die. The constitutive behaviors of both the post-SHS body and the PTM are determined based on theoretical and experimental studies. By incorporating them into a finite element model, the densification and deformation behaviors of the post-SHS body are simulated and the results are compared to the experimental data with satisfactory agreement. To obtain desired final shape, the optimized initial shape of the pre-QIP porous body is also designed based on a special iterative simulation approach.

Physical to mathematical model:

FEM model based on custom code and Marc.Mentet

Experimental tests and measurements

Microwave heating and sintering of porous metals

A systematic study of the absorption, heating behavior, and microstructure evolution of porous copper powder metal compacts subjected to 2.45 GHz microwave radiation and explain our observations using known physical mechanisms. Using a single-mode microwave system, we place the compacts in pure electric E or magnetic H fields and compare the heating trends. We also investigate the effect of particle size on the same. The observed trends and the differences between E- and H-field heating are reflected in the dramatic changes in the conductivity, permittivity, and permeability of the samples. These property changes are effected by the microstructure evolution during heating in the two types of fields. We also find that the observed dependence of the initial microwave heating on particle size is suggestive of single-particle behavior.

Student Design Project

Easy load pneumatic Trailer

The focus of this project is to design and construct a utility trailer that is easier and more convenient to the end user. The final product will consist of a utility trailer that will use no ramps for the loading process and eliminates the fear that is experienced when riding utility equipment or motorcycles up a ramp (fear of heights). The main deck of the trailer will lower to the ground when the operator wants to load or unload the trailer making the process easier. This trailer will operate on a fully pneumatic system that will all be contained within itself. Once the trailer is loaded, it will be set to a ride height that will match that of the hitch of the tow vehicle. Matching the height of the trailer to the hitch will provide for a level load that will not cause vehicle sway or loss of traction during heavy braking, strong winds, or turning.

Concept design

Design based on SolidWorks CAD software

Strength analysis

Final design rendering using SolidWorks CAD software

Sample publications:

J. Ma, K. Cris, Fluid Flow and its Effects on the Efficiency of Single Ended Evacuated Tubular Solar Thermal Collector, Engineering Journal, (2015) (in review)

J. Ma, A. Parker, K. Kuan, Thermal Properties of Copper Tungsten with Copper Via Composite, International COMSOL 2011 Conference, Boston, MA, October, (2011).

J. Ma, E.A. Olevsky, Numerical Simulation of Densification and Deformation of Porous Bodies in a Granular Pressure-Transmitting Medium, Advances in Sintering Science and Technology, Ceramic Transactions, Vol. 209, Pages 113-124 (2009).

K. Kuang, D. Zhu, J. Ma, Development of Super Copper Tungsten IMAPS ATW on RF/Microwave Packaging, San Diego, CA, September, (2009).

J. Ma, G.J. Weisel, B.L. Weiss, N.M. Miskovsky, D.T. Zimmerman, Systematic Study of Microwave Absorption, Heating, and Microstructure Evolution of Porous Copper Powder Metal Compacts, J. of Applied Physics, 101, 074906 (2007).

E.A. Olevsky, J. Ma and M.A. Meyers, Densification of Porous Bodies in a Granular Pressure-Transmitting Medium, Acta. Materialia, Vol. 55, Issue 4, Pages 1351-1366 Feb., (2007).

J. Ma, C.T. Smith, G.J. Weisel, B.L. Weiss, N.M. Miskovsky, D.T. Zimmerman, Single Mode Microwave Heating of Copper Powder Metal Compacts, COMSOL User Conference, Boston, Oct. (2006).

J. Ma, E.A. Olevsky, and M.A. Meyers, Synthesis of dense TiC-Ti based cermets via self-propagating high temperature synthesis and quasi-isostatic pressing, Proc. 36th International SAMPE Technical Conference (2004).

J. Ma, E.A. Olevsky, and M.A. Meyers, Modeling of pressure transmission during post-reactive-sintering quasi-isostatic pressing, Sintering 2003, Eds. R.M. German, G.L. Messing, R.G. Cornwall, 6 p. (2003).

H. Shi, J. Ma, X. Qing, Distribution of Elastic-Plastic Field on Circular Rings Containing a Rounded Tip V-Notch under Incline Compressive Load, Chinese Journal of Applied Mechanics, Page 13, No2, (1999).

Vertical Axis Wind Turbines

Evacuated Solar Thermal Collector

Powder Metallurgy

Student Design Projects

Sample Publications