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Mark Hofacker, PhD, PE

Hi, I'm Mark! I'm a mechanical engineer that spends most of his time making cool stuff at work. When I am home I like making things (like furniture) out of wood. Sometimes I read books and feel accomplished. Sometimes I watch YouTube and feel less accomplished. I secretly wish that the internet never advanced beyond its perfect condition in 1998. This is me:

Mark on a boat with a cell phone (not shown)

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Portfolio

Education

Vanderbilt University Nashville, TN (2007-2013) - PhD Mechanical Engineering Dissertation

South Dakota School of Mines and Technology Rapid City, SD (2002-2007) - BS Mechanical Engineering

Work Experience - Schlumberger Limited - Sugar Land, TX

Mechanical Engineer New Service Development (2019-Present)

Working on an exciting new product. I will post links and more detailed descriptions when the products and services are publicly announced.

Mechanical Engineer ACTive Power (2016-2021) Link

I was the primary mechanical engineer on new product development team that received the World Oil Best Well Intervention Technology Award in 2020 (link to award) For this project I traveled to field locations in Saudi Arabia, Qatar, Norway, and Gulf Coast to implement new product. I developed new hardware and processes for installing cables into coiled tubing, designed new surface and downhole equipment to support new cables, and designed new electrical connectors to resist corrosion in contaminated environment

Mechanical Engineer ACTive Xtreme(2014-2018) Link

For Schlumberger's flagship coiled tubing service, I designed new downhole tools and performed stress calculations. I tested these tools for resistance to downhole conditions and lead manufacuring efforts to build new tools for field locations.

Research - Vanderbilt University - Nashville, TN

Propane Powered Air Compressor (2010-2013) Read here or here

During this project we designed and built a functional a free-piston engine compressor. By combining the engine and compressor, the device is capable of efficiently producing low temperature air at high pressures. This in turns translates into a high-energy density power supply with an energy density three to five times greater than that of a battery/motor combination. By injecting compressed air and exploiting the dynamic loading of a high inertance, low mass liquid piston, this device is capable of an inject-and-fire operation that avoids traditional intake and compression strokes. The engine-compressor is capable of self balancing with a single cylinder due to the figure eight arrangement of the liquid piston. Due to an integrated, low weight, low stiffness check valve, air is compressed into a high pressure reservoir with low amounts of blow back. The design along with experimental and theoretical results are shown for the engine compressor.

Stirling Thermocompressor (2010-2013) Read here

I designed and built a Stirling Thermocompressor intended for use with powered ankle-foot orthosis. The thermocompressor utlized novel heat exchangers to efficiently convert thermal energy from propane into pneumatic power.

Bridge Vibration Energy Harvester (2010-201q) Read here

For this project I designed vibration energy harvester is designed to power a node of a bridge condition monitoring sensor network. A control law for the harvester was derived using the maximum power transfer theorem. The derived controller possesses the novel feature of canceling the complex part of harvester’s impedance by eliminating inertial and stiffness elements. This enables the collection of the maximum amount of available power across a broad spectrum of frequencies. The controller does not contain the delay or the computational overhead of a fast Fourier transform because the excitation frequency is never explicitly calculated. This control approach was validated in simulation and experimentally using a prototype bridge energy harvester.

Free Piston Stirling Engines (2007-2010) Read here or here

While working on this project, we modeled and built several different free piston Stirling Engines. To validate the models, an experimental apparatus to simulate the performance of different engines was constructed using linear actuators, sensors, and a free-piston Stirling engine. The behavior of the experimental apparatus was compared to the behavior predicted by the linear models. The operating characteristics of the experimental apparatus are compared to the dominant poles of the closed loop models. Relations are described between the imaginary component of the dominant poles and the operating frequency of the engine and between the real component and the ability of the engine toenter sustained oscillation.

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Publications