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Fast-Response Flow Meters for Onboard Systems (Harsh Chemicals)


OUSD (R&E) CRITICAL TECHNOLOGY AREA(S): Integrated Sensing and Cyber


OBJECTIVE: To develop a fast-time-response, low flow-impedance, flow meter compatible with a pyrophoric fluid such as Tri-ethyl Aluminum (TEA) that has a small form factor and is easily integrated with standard stainless-steel tubing for use as flight hardware.


DESCRIPTION: Pyrophoric liquids such as triethylaluminum are currently being used in the Towed Airborne Plume Simulator (TAPS) to simulate the plumes of surface to air missiles in order to test aircraft missile warning systems. The flow rate of the pyrophoric liquid is controlled to simulate the temporal behavior of the intensity of a missile plume. The radiometric intensity produced by TAPS burner is strongly proportional to the flow rate of the pyrophoric fuel controlled through a specialized valving system. The system currently is lacking an accurate method of measuring the pyrophoric liquid flow rate during the TAPS burner operation. Measuring this flow rate during a burn will allow control system improvements and provide valuable diagnostic and health information. Flow sensors are unavailable that meet the requirements for time response, flow rate range, and compatibility with pyrophoric fuels which ignite upon the presence of oxygen. The viscosity of the target fluids is 2-3 centipoise. It is preferred that the solution be non-intrusive, having no effect on the flow; otherwise, having minimal impedance to the flow. Digital and analog outputs are desired to provide maximum flexibility with control and data systems.


The sensor must be repeatable and have sufficient linearity to be capable of being absolutely calibrated.

The flow meter must meet current turbine flow meter specifications using low pressure-drop methods and with a relatively small form factor. The flow meter must be capable of being non-destructively operated with gaseous (typically air or nitrogen) flow when the liquid is not present. The flow meter must be able to withstand harsh vibration and temperature (roughly -40 °F to 120 °F) environments without significant degradation in performance. The flow meter must be designed with modular replacement and installation in mind.


The desired performance characteristics include:

-Repeatability of ±0.2% of reading (threshold), ±0.04% of reading (objective), ±0.02% of reading (stretch goal)

-Linearity of ±0.5% and ±0.1% using software (threshold), ±0.2% and ±0.05% using software (objective), ±0.05% and ±0.01% using software (stretch goal)

-Calibration Uncertainty of ±0.5% of reading (threshold), ±0.2% of reading (objective), ±0.05% of reading (stretch goal)

-Accuracy of ±0.4% of reading + 0.2% of full scale (threshold), ±0.2% of reading + 0.2% of full scale (objective), ±0.1% of reading + 0.1% of full scale (stretch goal)

-Response Time to Step Change in Flow Rate of ≤ 4 millisecond (threshold), ≤ 1.0 millisecond (objective), ≤ 0.2 millisecond (stretch goal)

-Flow Range of 0.05 to 5 gal/min (threshold), 0.05 to 10 gal/min (objective), 0.05 to 30 gal/min (stretch goal)

-Power Supply Voltage to be fixed input in the range of 5 to 30 VDC (threshold), uses any arbitrary voltage in the range from 5 to 24 VDC (objective), uses arbitrary voltage in the range from 303 to 52 VDC (stretch goal)

-Effective output Resolution of 2048 levels (threshold), 4096 levels (objective), 8192 levels (stretch goal)

-Maximum Power Usage of 100 Watts (threshold), 10 Watts (objective), 1 Watt (stretch goal)

-Size of 6”x3”x1” (threshold), 4”x2”x1” (objective), 2”x2”x0.5” (stretch goal)

-Maximum Operating Pressure of 130 psi (threshold), 160 psi (objective), 180 psi (stretch goal)

-Tubing Size of 0.5” to 1.0” (threshold), 0.25” to 2.0” (objective), 0.25” to 3” (stretch goal)

-Materials of Construction of 304/306 stainless steel (threshold), 304/306 stainless steel (objective), Performance alloy (stretch goal)

-Performance Life of 10,000 hours (threshold), 50,000 hours (objective), 100,000 hours (stretch goal)


PHASE I: Awardee(s) will develop a proof of principle design concept that satisfies the aforementioned requirements. Awardee(s) will research current methodologies and COTS components to conceptualize a prototype flowmeter. Awardee(s) will verify any potential high technical risk elements through analysis or empirical demonstration and assess potential points of failure and uncertainty of the measurement.


PHASE II: Awardee(s) will develop of a flow meter that meets the space, power, and packaging requirements of the flight-ready TAPS system. Awardee(s) will demonstrate flow meter performance in a relevant environment for up to 100 hours or until failure. Awardee(s) will sequentially evaluate three additional working prototype systems incorporating lessons learned to achieve a sufficiently robust and reliable flow meter technology that meets all objective requirements and/or stretch goals.


PHASE III DUAL USE APPLICATIONS: Awardee(s) can expect to formalize the production process and design the appropriate machinery/infrastructure to support full-scale commercial production.



  1. Clark C, Zamora M, Cheesewright R, Henry M, “The dynamic performance of a new ultra-fast response Coriolis flow meter”, Flow Measurement and Instrumentation 17 (2006), pp391-98, doi:10.1016/j.flowmeasinst.2006.07.002;
  2. Coriolis Flowmetering Technology: Theory and Practice:;
  3. Commercial Flow Meter (less than 4 ms response time, gaseous flow only);
  4. Commercial Flow Meter (20 ms response time, liquid flow, measures line pressure and temperature as bonus feature);


KEYWORDS: flow meters; pyrophoric; flow measurement; turbine meter; positive displacement meter; vortex shedding meter; magnetic meter; ultrasonic flow meter; Coriolis type; thermal meter

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