Jonathan M. Protz

Experimental results for a microscale ethanol vapor jet ejector

A microscale jet ejector driven by ethanol vapor is designed and tested to induce a suction draft using a supersonic converging–diverging micronozzle. A three-dimensional axisymmetric nozzle is fabricated using electro-discharge machining to produce a throat diameter of 187 µm with an expansion ratio of 3:1. The motive nozzle achieves a design mass flow efficiency of 93% compared to isentropic calculations. Two different ejector area ratios are compared using ethanol vapor and nitrogen gas separately to motivate and entrain ambient air. The experimental data indicate that the ejector can produce a sufficient suction draft to satisfy both microengine mass flow and power off-take requirements to enable its substitution for high-speed microscale pumping turbomachinery.

Modeling of the Decomposition and Combustion of Hydrogen Peroxide and Ethanol for Design of a Bipropellant Microrocket Engine

Analytic, one-dimensional studies of the microscale catalytic and thermal decomposition of hydrogen peroxide and the lean, catalytic combustion of ethanol are presented. The models include basic conservation laws, droplet heating and evaporation, droplet dynamics, and diusion-limited decomposition kinetics. Simplifying assumptions are made that allow the explicit solution of distinct transient processes, providing a basic method for sizing microscale reaction chambers. Results are implemented in the detailed design of a Giard injector-pumped microrocket engine.

A MEMS fabrication approach for a 200GHz microklystron driven by a small-scaled pseudospark electron beam

High performance terahertz (THz) radiation sources hold great promise for a variety of military and space applications. With micro-electro-mechanical systems (MEMS) fabrication techniques, it is possible to attain the smaller, more precisely machined resonant structures required by Vacuum Electronic Devices (VEDs) to function in these frequencies. The research presented here proposes a design and fabrication process for a micro-klystron with a targeted operating frequency of 200 GHz; being developed jointly by Duke University, the University of Strathclyde, UK, and Logos Technologies. It also analyzes the use of a pseudospark (PS) discharge as a novel electron beam source to drive the klystron. Dimensional tolerances are investigated using both analytic and numeric techniques. The incorporation of alignment structures into the fabrication process that utilize kinematic and elastic averaging effects, along with clever stacking techniques, allows submicron alignment tolerances yielding an expected power output of approximately 5W per klystron with an overall efficiency of 20%. The device proposed here, with a volume on the order of 0.01 cc, should be capable of output power densities of up to 1kW/cc. A fabrication run recently completed at MITs Microsystems Technology Laboratories yielded promising results and 32 silicon die were successfully bonded into a stack 1.4cm tall. Difficulties remain, however, in controlling surface roughness and integrating a klystron with alignment features for parallel processing. Several alternative fabrication schemes have been proposed and another fabrication run based on these modifications is currently underway.

Investigation of a 200GHz microklystron driven by a small-scaled pseudospark electron beam

Based on previous experimental investigations on pseudospark (PS) discharges, a small-scaled PS electron beam source was conceived to drive a 200GHz microklystron. Recent PS e-beam experiments producing a beam of 1mm in diameter and klystron interaction simulations will be presented. The microklystron will be fabricated using micro-electro-mechanical systems (MEMS) construction techniques.

Investigation of Heat Transfer and Scale Effects on the Performance of a Giffard Injector-Pumped Microrocket

A novel approach to propellant pressurization for microscale rocket engines is introduced. The Giffard injector is shown to be a viable alternative to turbomachinery for pressurizing the liquid propellants on board a microrocket, offering a design free of moving parts. Extending the authors’ previous work, the engine performance is computed for several fuel/oxidizer combinations. A large-scope study of the heat transfer throughout the regenerative cooling engine cycle examines the effects of combustion chamber pressure and engine size on performance. A boiler is designed that facilitates the heat transfer required for adequate cooling and is modeled using the effectiveness-number of transfer units method. The computed specific impulse and thrust-to-weight ratio of the design for the propellants considered are roughly 250 s and 2000, respectively. The power density of the proposed injector-pumped design is seen to behave like that of turbopumped microrockets up to a critical nozzle throat diameter of approximately 1 cm, beyond which the advantages of an entirely static structure are outweighed by decreasing performance.

P1–1: Study of a 200GHz microklystron using a small-scaled pseudospark electron beam

Based on previous experimental investigations on pseudospark (PS) discharges, a small-scaled PS electron beam source was conceived to drive a 200GHz microklystron. Recent PS e-beam experiments producing a beam of 1mm in diameter and klystron interaction simulations will be presented. The microklystron will be fabricated using micro-electro-mechanical systems (MEMS) construction techniques.

Study of a 200GHz microklystron using apseudospark-sourced electron beam

Summary form only given. In recent years much interest has been shown in radiation sources in the terahertz region (0.1 to 10THz) because of the demands in plasma diagnostics, radiotherapy, medical research and advanced communications. The Klystron is an ideal choice for THz generation due to its operation mechanism, efficiency and robustness as well as the fact that it may be scaled in size in order to achieve higher frequency operation. Due to the decrease in size as the frequency is increased, there is a need for the electron beam current density to increase in order to achieve reasonable output powers. The pseudospark (PS) discharge is an ideal electron beam source because it can produce a suitable high current density and small diameter (<;1mm) electron beam.A 200 GHz microklystron was designed and simulated using the particle-in-cell (PIC) code MAGIC. MAGIC-2D results revealed a strong amplification signal as will be presented. Based on previous PS experiments using a small-scaled single gap PS an 1mm diameter electron beam of 4 A at 6 kV was generated. This allowed the possibility to further scale down the PS into the micron range to drive a microklystron to be demonstrated. The fabrication of the designed microklystron will be achieved by using the process based on microelectromechanical systems (MEMS).

Microscale ethanol vapor ejector and injector

Two non-rotating pumping components, a jet ejector and injector, were designed and tested. Two jet ejectors were designed and tested to induce a suction draft using a supersonic micronozzle. Three-dimensional axisymmetric nozzles were microfabricated to produce throat diameters of 187 μm and 733 μm with design expansion ratios near 2.5:1. The motive nozzles achieved design mass flow efficiencies above 95% compared to isentropic calculations. Ethanol vapor was used to motivate and entrain ambient air. Experimental data indicate that the ejector can produce a sufficient suction draft to satisfy both microengine mass flow and power off-take requirements to enable its substitution for high speed microscale pumping turbomachinery. An ethanol vapor driven injector component was designed and tested to pressurize feed liquid ethanol. The injector was supplied with 2.70 atmosphere ethanol vapor and pumped liquid ethanol up to a total pressure of 3.02 atmospheres. Dynamic pressure at the exit of the injector was computed by measuring the displacement of a cantilevered beam placed over the outlet stream. The injector employed a three-dimensional axisymmetric nozzle with a throat diameter of 733 μm and a three-dimensional converging axisymmetric nozzle. The experimental data indicate that the injector can pump feed liquid into a pressurized boiler, enabling small scale liquid pumping without any moving parts. Microscale injectors could enable microscale engines and rockets to satisfy pumping and feedheating requirements without high speed microscale turbomachinery.

Experimental demonstration of lossy recording of information into DNA

Non-coding DNA comprises the majority of an organisms DNA and has the potential to store massive amounts of information. We hypothesize that information can be stored into non-coding DNA using a noisy mechanism comprised of thermally sensitive liposomes as sensors and measuring transport state variable information through DNA release and binding in response to stimuli. To test our hypothesis, we performed experiments that demonstrated the in situ, de novo synthesis of information-encoding DNA using natural biomaterials. Our results were compared to a lumped-parameter model designed to simulate the experiments. We found promising correlation between the DNA sequences generated by the simulations and those generated experimentally, suggesting that the in situ, de novo synthesized DNA does store recoverable information by the mechanism proposed.

Experimental investigation and modeling of scale effects in jet ejectors

Three microscale jet ejectors were designed and tested to induce a suction draft using a supersonic micronozzle. Each axisymmetric nozzle was fabricated using three-dimensional electro-discharge machining to create throat diameters of 64, 187 and 733 µm with design expansion ratios of 2.5:1 and design ejector area ratios of 8. The experimental data using nitrogen gas for the motive fluid indicate that the ejector can produce a sufficient suction draft to enable its substitution for high-speed turbomachinery in micro engine applications. A pumping power density of 308 kW L−1 is observed experimentally, which agrees well with a theoretical model including losses associated with the suction flow inlet and viscous effects in the motive nozzle and mixing regions. The present theoretical model further predicts a maximum achievable power density of 1 MW L−1 for microscale ejectors with a throat diameter of 10 µm and throat Reynolds number of 1300.