RFI 80GRC021RFI0005 QA.pdf

Answer to Submitted Questions:

Q1. Is heat shielding suggested (concern for bulk fuel temp or internal varnishing/coking)? What is the life expectancy? How long will the parts be at temperature?

There will be only one experimental campaign at high T3 (air temperature up to 1300 F), which is expected to be less than 100 hours of total testing time at these high air temperatures

We are expecting the fuel circuit designs to keep fuel temperature below values where fuel coking may occur.

Q2. NASA asking for quotes, indicating that they will pay for the parts? Is the timeline very important? Is it ideally delivered in 2021?

NASA intends to pay for design, fabrication and parts. Deliver of a completed injector(s) by March 2022 is acceptable.

Q3. May additive be used (assuming material compatible with x-ray)?

Additive manufacturing is acceptable.

Q4. How many design configurations are acceptable/required? Is a Design of Experiment intended to be used (for different air swirlers for example)? Who defines the DOE?

Ideally, a single design would meet x-ray transmission and operating condition requirements, but modular designs or multiple designs are acceptable and of interest. We had not considered a design of experiments approach for the aero-spray program.

Q5. Is there a need for “blank” fuel swirlers to reserve the spacing that a prefilmer would require?

For testing with the prefilmer fueled, the swirlers should remain. The interior wall between the two swirling flow paths should be the only modified component for testing the prefilming option.

Q6. Similarly, with the primary/secondary, is a blank required for that spacing when just measuring with the prefilmer?

A blank is not necessary for the centerbody (primary/secondary nozzle). For any testing with the prefilmer fueled, the centerbody would remain and the secondary fuel circuit would be turned off.

Some testing with the prefilmer fueled may also include fueling the primary fuel circuit (pressure swirl nozzle).

Q7. Is this just a one-off delivery (1 piece only)? Or will the order be for 10 pieces of each configuration (amortize set up)?

There is a possibility of requesting more than one complete injector, but we do not anticipate more than three complete injectors being made.

Q8. Is the 30um SMD just for the primary? At what pressure? Is the measurement equipment important (i.e. TSi versus Malvern)

The 30 microns SMD for the primary fuel circuit should apply at injection into 1 atm quiescent air. We anticipate smaller SMD may occur at higher pressures. We are not imposing an SMD requirement for the secondary fuel circuit (jet-in-crossflow).

Q9. Is there a secondary flow rate required? Is there a jet form required (i.e. “laser sharp” or can it be frayed)? Is there a required/suggested l/Ø?

Secondary flow should have a flow number of approximately 18. Jet orifices should be simple for the sake of modeling validation and fabricated with sharp outlet corners with no burrs.

Q10. Is there a flow rate required for the prefilmer variant?

The prefilmer option would be an alternative to the secondary circuit and should have a comparable flow number (approximately 18).

Q11. What do the upstream connections need to look like? Will there be Swagelok tubes/sizes? Internal leakage concerns?

Upstream connections are to be determined but will likely interface with ¼” Parker or Swagelok tube fittings.

Q12. Is there material data available for other materials (alloys of beryllium, stainless, etc.) that could be used for x-ray requirements?

At first order, the mass attenuation coefficient of alloys (or compounds) can be determined by summing the component mass attenuation coefficients scaled by their weight percentages. The expression is μ/ρ = Σ wi (μ/ρ)i, where μ/ρ is the mass attenuation coefficient for the alloy, wi is the weight fraction of the ith element in the alloy, and (μ/ρ)i is the mass attenuation coefficient of the ith element. The values of (μ/ρ)i may be found in tables available from NIST < http://physics.nist.gov/PhysRefData/XrayMassCoef/tab3.html > where the photon energy range of interest is between 8 keV and 21 keV. The effect of material density should be included by multiplying by the mass density of the alloy (ρ) to obtain the linear attenuation coefficient (μ), which should be minimized for improved x-ray transmission.

Q13. Page 1, Paragraph 3 of the RFI states the use of an optional third fuel circuit. Is this third circuit due to the impinging jets coming off the prefilmer lip or is the intent a third circuit of fuel, and if so, how is the fuel expected to be injected into the outer circuit?

The optional third fuel circuit is not due to the impinging jets coming of the prefilmer lip. The optional third fuel circuit is envisioned as a thin film of fuel injected from the wall between the two swirler flow paths. The current draft design did not consider this fuel injection concept in any detail.

Q14. Page 4, paragraph 1 states “Fuel Injector will be designed to fit into a bulkhead that is contained in a 3” diameter chamber. Is this design meant to be a “tip on a stick” or does a mounting flange need to be developed that can orient the nozzle per the “rotational indexing of the central liquid nozzle” that is requested in page 4 paragraph 3. Are there requirements for the fuel inlet design upstream of the nozzle shown or is this open to our needs/design?

The fuel injector mounting is currently unconstrained as the upstream plenum has not been specified. A “tip on a stick” design can be utilized, but a method of indexing would be preferred to ensure repeatable orientations and relationships between parts and the greater rig.

Q15. Page 4 Figure b – no requirements listed on where the fuel needs to exit for both the jets along the conical face, as well as the primary jet. This would seem to be critical for X-ray diagnostics.

There is not a strict requirement on the location of the jets along the conical face, as long as all four secondary jets are positioned symmetrically in the circumferential direction (i.e., around the conical face). The exact length of the conical face is left to the design requirements for wall thickness of the internal passages.

Q16. There is no concentricity requirement for the nozzle – with the L/D and no supportive features down the length of the swirler, this design will be very difficult, and it may affect performance.

For the sake of model validation, the concentricity of the nozzle, and thus the relative position of the fuel orifices with the walls should be repeatable and precisely controlled. The L/D of the concept is not a strict requirement if a tighter concentricity tolerance can be achieved with a lower L/D while maintaining uniformity of the swirling air flow at the liquid introduction locations. Support stings/structure of the nozzle may not be desired as they would create wakes in the swirling flow upstream of the liquid introduction. Additional support of the fuel nozzle upstream of the swirler should be designed to ensure repeatable positioning of the nozzle concentrically within the confinement.

Q17. The wall thickness for the outer air swirler looks to be the same as the inner, but the inner is specified at .040” in Figure b., while the outer can be calculated from the Max OD specified in the design parameter table (1.34”) and the ID of the outer wall in Figure b (1.220”) which leads to a thickness of .120”. Additionally the design parameter table does not list tolerances for any of the dimensions, but states “flexible tolerance, but more strict on wall thicknesses”. What is the required “strict” wall thickness tolerance? What is the desired/required wall thickness for the outer wall? Should it be the same as the inner wall?

There is no restriction on the outer wall thickness in the region of the swirlers and the outer wall can be used for mounting, etc.

Both inner and outer wall thicknesses in the x-ray transparent region should be designed to be as thin as manufacturing permits and mechanically stable to improve x-ray transparency. The thickness of the walls upstream of this x-ray visible region is less of a concern.

Q18. Can the two swirler circuits be one unit or do both have to be modular?

They can be one unit.

Q19. Is there any concern with surface finish? Additive manufacturing will be the optimal way to successfully fabricate and meet the L/D and wall thickness requirement.

Additive manufacturing is acceptable. We not are currently placing any requirements on surface finish.