Joseph Lefkowitz

Joseph Lefkowitz
Joseph Lefkowitz
Inter-pulse coupling: A recently-discovered phenomenon
Technion - Israel Institute of Technology

Zuckerman Faculty Scholar Joseph Lefkowitz joined the program at the Technion in 2018. After completing his postdoctoral research at Princeton University, he worked at the Air Force Research Laboratory at Wright-Patterson Air Force Base in Ohio, where he served as a National Research Council Associate, part of a government-run program promoting excellence in scientific and technological research. The past two years have been busy for Joseph: among his many accomplishments are a newborn son and the establishment of his own lab.

Joseph Lefkowitz Lab

Dr. Lefkowitz’s research in the Combustion and Diagnostics Laboratory at the Technion involves new concepts in the fields of reacting flows and optical diagnostics, with a focus on ignition, plasma-assisted combustion, and fuel conversion. Ignition is the central topic, where researchers explore methods to optimally ignite near-limit mixtures, relevant for ultra-lean combustion engines, high-speed air-breathing propulsion, alternative fuels, and hybrid rockets. As engine technologies continue to advance towards increased efficiency and reduced greenhouse gas emissions, and use of high-speed propulsion expands, ignition becomes an ever-increasing challenge.

“By studying the fundamental phenomena governing the formation of ignition kernels, we can understand how to best deposit energy in near-limit conditions, enabling engines which until now have been unachievable,” explains Dr. Lefkowitz. The lab’s focus is on plasma-assisted ignition using nanosecond-pulsed high-frequency discharges, which targets deposition of energy to selectively excite and dissociate gas molecules without excessive thermal heating. This allows unprecedented control over the energy deposition process.

“In our recent work, the lab discovered the existence of “inter-pulse coupling,” a phenomena in which discreet regions of non-equilibrium plasma may overlap to constructively or destructively activate a flowing reactive mixture, determining ignition probability. This formerly-unknown phenomena breaks the rules of the established “minimum ignition energy,” and introduces a “minimum ignition power,” in which the total energy deposition is no longer the determining factor in successful ignition.

In our work on fuel conversion, we focus on carbon-neutral alternative fuels, and selectively optimize fuel conversion into a mixture more suitable for modern and future engines.  In the case of ammonia, we use low temperature plasma to reform the fuel molecules into a mixture containing ammonia, hydrogen, high energy radicals, and excited species, which decreases the ignition energy and increases the flame speed such that it is suitable for use in combustion engines.

The emerging area of cold plasma reforming takes advantage of targeted energy deposition to excite electronic states of molecules leading to non-Boltzmann energy distribution, allowing conversion routes not possible by other reforming methods. By probing the intermediate and product species concentrations and comparing to kinetic models developed by our group, we can formulate predictive tools. We can then optimize the reforming process to alter yield ratios and produce the reformed fuel with the desired properties for a combustion engine of interest.

For all of our efforts on reacting flows, we apply cutting edge diagnostic techniques for insight into the time-dependent and multi-species environments. Our focus is on infrared techniques, including hyper-spectral imaging, high-speed multi-spectral imaging, and tunable diode laser absorption spectroscopy. Hyper-spectral imaging techniques being developed in our group collect simultaneous spatially- and spectrally-resolved “data cubes” not possible with any other technique.”

Stay tuned for the next big discovery by our Zuckerman Scholars!

Joseph Lefkowitz Team

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