Development of Optimized Combustors for Palm Power Generation

The Team, see below

A 2.4 M$ research grant will be awarded by DARPA to the combustion group at Yale, lead by Professor Gomez (ME), to advance the technology for power generation in miniaturized systems using liquid hydrocarbons. The grant is part of the Palm Power program of DARPA (www.darpa.mil/baa/baa01-18.htm) to address the need for lighter and more compact electrical power sources for soldier, robotic, and other emerging applications. At present, batteries are used for these systems. Small energy conversion devices that convert high-energy content fuels to electricity will be required to address the anticipated energy shortfall for many DoD missions

The large power density (power/volume) offered by liquid and solid fuels, up to two orders of magnitude larger than the best batteries available on the market today, suggests that combustion may be attractive for power generation at scales much smaller than previously explored, with overall system dimensions on the order of millimeters or, at most, centimeters (mesoscale).

While the initial goal is to meet DoD mission needs, it is anticipated that applications of this technology may be much broader. In fact, leaps in power density consistently had a great socio-economic impact in the past three centuries. For example, the development of steam engines in the early 1700s, at power densities on the order of 0.005 W/g (Watts/gram), contributed to the onset of the industrial revolution. The development of steam turbines, Diesel and Spark-ignition engines (1890-1960), at power densities in the range 0.05-1.0 W/g, introduced a veritable transportation revolution. Similar considerations apply to the impact of turbojets and turbofans on aviation, with power densities on the order of 10 W/g. The proposed development of micro-combustors could lead to power levels on the order of 100 W/g, comparable to those of rocket engines.

As in the past, this leap could usher in yet another technological revolution. Consider the analogous situation in which the introduction of the personal computer was accepted with skepticism two decades ago by the scientific community, as some kind of sophisticated typewriter. Yet, properly networked, a few years later PCs could even compete with, and often replace, mainframes. A program on a small scale combustion-based power generator would lead to the development of the ultimate distributed power source that may replace batteries in all kinds of applications, including non-military ones. Charging, say, a laptop the same way as a cigarette lighter, without being hampered by short-lived and heavy batteries, could be a reality in the not too distant future.

The program has two goals/deliverables: i) to develop optimized mesoscale combustors for the clean and efficient burning of the small liquid fuel flow rates of interest; ii) to integrate the optimized devices with an energy conversion system that will be concurrently developed by other research groups. Numerous challenges will be faced. Clean and efficient combustion in a small volume is hampered by problems associated with short residence times in the combustor (incomplete conversion), efficient delivery of a liquid fuel, and with a large surface/volume ratio (coking, quenching). In light of these difficulties, brute force empiricism will not be successful. The Yale team brings in a unique combination of design, experimental, computational and theoretical expertise that, used in a complementary way, can advance the state-of-the-art.

The Yale group is complemented by Precision Combustion (PCI), Inc. (North Haven, CT) that will receive a subcontract of 300K$. PCI will focus upon catalytic combustor design and prototype manufacturing opportunities within the Yale combustor.

The program starts 7/1/2001 and will last three years.

The Yale team

Alessandro Gomez (ME) will act as Principal Investigator. He will coordinate all aspects of the project and will maintain contacts with the counterparts at PCI. Professor Gomez will be specifically involved in the design, testing and optimization of the micro-combustor systems. Marshall Long (ME) will be in charge of the development and application of laser-diagnostic techniques to these systems. Lisa Pfefferle (CE) will implement the catalytic approach and the application of molecular beam mass-spectrometry to the combustion effluents. Daniel Rosner (CE) will be involved in issues related to the effect of large surface area on chemical kinetics (heterogeneous versus homogeneous) and with heat transfer optimization. Mitchell Smooke (ME) will be in charge of the computational part of the proposed program. Mark Reed (EE) and Jim Klemic (EE) will deal with the micro-fabrication and prototype development. The assembled team has recognized expertise in the areas of: computational combustion, catalytic combustion, chemical kinetics and reaction engineering, combustion diagnostics, spray combustion, transport theory, multiphase flows, molecular beam and mass spectrometry techniques, and microfabrication.