Dr. Joseph Lefkowitz is an Assistant Professor at the Technion, where he heads the Combustion and Diagnostics Laboratory in the Faculty of Aerospace Engineering. With new concepts in the fields of reacting flows and optical diagnostics, the lab focuses on ignition, plasma-assisted combustion, and fuel conversion for alternative fuels. 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.
Please describe your current research, the focus of your lab, and the practical implications of your research.
Our Combustion and Diagnostics lab applies advanced diagnostics techniques and novel approaches to combustion science with a focus on plasma-assisted ignition and combustion diagnostics in an attempt to solve today’s limitations of efficiency, high-speed operation, and pollutants (including GHGs) in combustion devices. Our diagnostic methods research focuses 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” that are not possible with any other technique. In our work on fuel conversion, we focus on zero-carbon alternative fuels, and selectively optimize fuel conversion into a mixture that is more suitable for current and future engines. We work on enabling alternative fuels, such as using ammonia for combustion engines. Ammonia is an energy carrier for storage of hydrogen with high energy density, and it can be burned as ammonia or converted back to hydrogen on-site. It can be created from renewable sources and creates no greenhouse gasses. Ammonia is the second most produced chemical on earth, it can be synthesized from hydrogen from renewable sources combined with nitrogen from the air to create a liquid fuel stable under storage for long periods. 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, making it suitable for use in combustion engines.
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. 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. Our application of this technology are diverse, ranging from internal combustion engines to scramjets.
Our lab recently discovered the existence of something called “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.
What do you enjoy most about your research?
As a kid I was really into model rockets. I would buy small engines and set them in flight. And now I enjoy conducting exciting combustion experiments and lighting things on fire. We have a very high level of safety awareness and know what we’re doing at all times! Combustion is a quantitative science – we can’t say that it’s a random phenomenon. Exacting diagnostics and very developed methods require a certain amount of adventure while keeping an eye on the method of measurement. With these diagnostics the goal is to quantify properties of the reactive flow, such as temperature, velocity, or many of the chemicals involved, so we can model it numerically. We do this with high-speed cameras and infrared cameras and lasers, which are really cool to work with. The experiments are always fun and interesting.
What inspired you to pursue this area of research?
Growing up I was always fascinated with flight. I studied thermodynamics and jet propulsion as an undergraduate and seeing how the mechanics worked fascinated me. I was headed towards working in the aerospace field – both my PhD at Princeton and postdoc at the Air Force research lab were pointing in that direction. They are world leaders in this area, and its where I became interested in the field.
What does it mean to you to be part of the Zuckerman Faculty Scholars Program?
I wouldn’t have been able to build my lab without funding from the Zuckerman Program, and for that I am very grateful. The Zuckerman Program is a wonderful vehicle for supporting US-Israel collaboration. Until I came to Israel, I worked on strengthening those bonds while in the US. The Faculty Scholars Program is great initiative and smart philanthropy that supports scientists and allows us to compete. So much philanthropy today is targeted to specific research areas, and the Zuckerman Institute is an independent body that gives grants across all areas of scientific research rather than bloating certain fields. This opens so much opportunity across the board, especially when we never know where the next big innovation is coming from. The innovation community in Israel is great and I’m happy to be a part of it.
Where do you hope your research will have the greatest impact?
I hope that it will be transformative in terms of the energy makeup of the world, contributing to the wide spectrum of solutions all in the greater effort to decarbonize. To be able to say that the Zuckerman program enabled that would be great.