|Acquisition Program: ||PM Future Combat Systems Brigade Combat Team|| Objective: ||Develop a sulfur sensor system to measure total content of sulfur in JP-8 fuel tank on combat vehicles for system control of on board fuel cell based auxiliary power unit (APU). The sensor system should be compact and light weight, and be installed either in the vicinity of fuel tank or in a suitable location between the fuel tank and the engine of the vehicle. The sulfur detection range should be from zero ppm up to 3000 ppm as specified in MIL-STD-83133F, and this system is expected to have similar degree of reliability and durability to the vehicle engine.
|| Description: ||A JP-8 fueled APU consisting of fuel reforming and a fuel cell is a highly desired and urgently needed technology for deployment onto combat vehicles. It is an enabling technology to ensure continued/continuous supply of electricity in critical silent mode for the duration of mission operations with additional benefit of increasing fuel efficiency and reducing logistics burden. Since the sulfur content of JP-8 fuel is detrimental to a fuel cell based APU and it varies in a wide range up to 3000 ppm, the concentration of the sulfur in the fuel must be closely monitored to allow the APU to fully function within specification. Without this information, the desulfurization system will be over designed and take up precious allocated space. A sulfur sensor would also allow for more predictable maintenance intervals, and thus a smaller overall system, by allowing the APU control system to compute when the desulfurization system needs to be cleaned or changed. Two approaches may be explored for a suitable solution, which includes innovative direct sensing of sulfur content in the liquid fuel, or indirect sensing of sulfur content after all the sulfur in the fuel is converted to SO2 gas form and subsequently detected optically/spectroscopically[1-3] at appropriate temperature. The goal of this topic is to develop a reliable, compact, and light weight SO2 sensor that is able to constantly measure the sulfur content in the JP-8 fuel in the combat vehicle fuel tank. The sulfur concentration of the incoming fuel stream, in real time, and the accumulative sulfur amount in the consumed fuel sent to the desulfurizer will be provided to the APU control system for operational parameter adjustment. Important issues such as sensor calibration, measurement interference, vibration resistance, and overall sensor system size should be considered. Using the engine exhaust as a target for measurement is allowed, but other innovative ways to convert liquid fuel to a gas mixture for better detection is encouraged.
|| ||PHASE I: Demonstrate that suitable materials, detection approach, and system design for SO2 detection. The sensor should be able to respond to SO2 at minimum 1 ppmV or below with sufficient signal strength within 30 seconds in an environment similar to automotive exhaust. Present and discuss the strategy to design the sensor that will be compact and light weight, and able to be integrated with a combat vehicle in hardware and the electronic system control of the APU with sensor fail-evident feature.
|| ||PHASE II: Design, construct, and evaluate a prototype of the complete SO2 sensor system. At the minimum, the sensor system should be demonstrated to have a lifetime of 1000 hours MTBF (Mean Time Between Failures). Deliver one complete sulfur sensor system to the Army.
|| ||PHASE III: Successful development of this sulfur sensor system for fuel cell based APU technology will enable higher fuel efficiency and less environmental footprint. This will have impact on a wide range of military power applications and will enhance the Army’s fighting capability and survivability in the battlefield with reduced logistic burden and lower thermal and acoustic signatures. The technology is also applicable to commercial power and energy applications such as fuel cell based electric power generation, mobile or stationary, fueled with fossil fuels such as natural gas, gasified coal, or liquid hydrocarbons.
|| References: ||
1. Rawlins, W.T; Hensley, J.M; Sonnenfroh, D.M. Appl. Optics 2005, 44, 6635-6643.
2. Xu, F; Zhang, Y.G; Somesfalean, G. Appl. Optics 2007, 46, 2503-2506.
3. Dooly, G; Fitzpatrick, C; Lewis, E. Energy, 2008, 33, 657-666.
|Keywords: ||Sulfur sensor, JP-8 fuel, sulfur dioxide, auxiliary power unit (APU)|
Questions and Answers:
Q: In reference to the range/precision requirements. You have given a range of 0 - 3000 ppm in the description, in the Phase 1 task you listed a 1ppmV or below within 30 seconds.
1. Could you clarify the measurement need in terms of resolution, repeatibility, reproducibility.
2. Can you also context these requirements in terms of expected stability in longer term field operations.
A: 1, The ability to detect sulfur content at lower level is desired for the situation of any batch of low sulfur fuel stock filled into the fuel tank. The accuracy will be a few percents plus/minus in the range of 10 to 3000 ppm.
2, The longer term stability of field operation will be about at least 6 months (or longer), and the sensor system can take one data point every 10 minutes in programmed interval.
Q: Your solicitation states a desire to detect sulfur in the fuel not in the exhaust stream. However, you also refer to detecting SO2 in both Phase I and Phase II objectives. It is unlikely that the sulfur in the fuel is in the form of SO2...more likely to be H2S or some other species. The sulfur in the exhaust gas will be in the form of SO2. Yet you specifically exclude detecting the sulfur in the exhaust gas. Can you provide some clarification of this? Thanks.
A: 1, The hot exhaust from internal combustion engine will be the target if SO2 is measured.
2, Direct detection in liquid fuel is desired in the first place, but may be more challenging.
Either approach will be acceptable.
Q: Are there any particulates such as soot present in the APU exhaust gas stream, and if so do you have an estimate of the particle size and amount? Thanks
A: The measurement was aimed at vehicle engine exhaust, not the APU exhaust. Combat and tactical vehicles running on JP-8 may have some soot but we don't expect very much. They are not a diesel engine. You are also welcome to search available information to get exact answer for yourself. Thank you.
Q: What are the maximum weight, power and size requirements?
A: About one pound and one liter overall.
Power consumption should be below 10W for sensor component.
Q: 1. Which specific organosulfur compounds are typically found in highest concentrations in JP-8?
2. Is H2S also a significant JP-8 contaminant?
A: 1. The sulfur compounds in JP-8 are not uniformly distributed and vary with the locations of the crude oil production and the refinery process plant.
2. H2S is not in liquid JP-8.
Q: In your answer to the first question you listed a lower detection limit of 10 ppm, whereas in the text it is 1 ppm.
1. Is 10 ppm acceptable?
2. What is the lowest concentration you would like to detect?
A: 10 to 15 ppm would be acceptable as the lowest detection limit, which is close to the requirement of EPA for low sulfur diesel (15 ppm).
Q: Would a sensor that measures hydrogen sulfide gas in the JP-8 reformate gas be responsive to this topic?
A: The answer would be NO.
Q: Is it possible to give an estimate of the JP-8 fuel volume to be measured, both in consumption rate in a Gallon Per Minute (GPM) basis and an estimate of the total volume in the desired 6 month or greater operational period.
A: During the use of a full tank of JP-8 fuel, it may only need to measure ten times for the sulfur content and that will be sufficient for the purpose of this topic. You may estimate how many full tanks of fuel are going to be needed if you drive a truck every day for delivery of goods. Thank you.
Q: Would a technology that works predominantly as a "batch" composition detector on the fuel as it is being loaded into the tank and/or after it is loaded into the tank be acceptable?
A: The sensor can be located either inside or outside the fuel tank and the measurement of sulfur content in liquid fuel in interval of every ten minutes will be accepted. Thank you.