Microstructural Transformation of Cold-Sprayed GRCop-42 for Rocket Engine Combustion Chamber Liners

Rocket engines have always relied on high-conductivity copper liners to protect structural components from extreme thermal loads produced by combustion. Forged NARloy-Z has been the material of choice for decades but increasing cost of its constituent silver and high waste in the machining process has reduced the alloy’s cost effectiveness. Aerojet Rocketdyne wants to determine the viability of cold-spray additively manufactured GRCop-42 as a replacement alloy to reduce liner cost. Screening tests were performed to observe the microstructural development and microhardness changes of cold-sprayed GRCop-42 after being subjected to multiple stages of the typical heat treatment of a combustion chamber liner. Two batches of samples with different cold-spray parameters were given one of four treatments: as-sprayed, HIPed, HIPed and annealed at 1700℉, and HIPed and annealed at 1800℉. Statistical analysis of hardness data concluded a reduction in mean hardness from 197HV to 119HV after HIPing and an additional reduction to 86HV after the annealing treatment. The temperature of the annealing was statistically insignificant. Optical microscopy revealed ‘healing’ of former powder boundaries after annealing treatment, indicated by the boundaries no longer being preferentially etched. These heat treatment effects suggest an increase in yield strength and low-cycle fatigue life, with fewer crack propagating, high-energy boundaries present. No reliable data could be collected on particle coarsening due to natural particle size variance

Design of PI controller with input constraint: application on blending process

Because of their simplicity, reliability and effectiveness, proportional–integral–derivative (PID) controllers remain the most widely used controllers in the process industries. Actuator saturation is among the most common and significant problem in control systems design. Normal PID controller does not take this into consideration. Normally, an anti‐windup compensator is employed in the system to overcome the problem. In this contribution, a new set of controller tuning relations is developed to tune the PI controller when the system is under saturation. The blending process was described as first order plus time delay (FOPTD) process and an expression is developed for saturation level, U as a function of controller gain, Kc with the range of R 0.4–2 (ratio of time delay to time constant). The proposed tuning rule relate the parameters of the controller to the parameters of a FOPTD model of the plant to a step change in the set point. The proposed method was applied to PI controller and tested on the process of blending system of sweetened condensed milk. The performance of the controller with various tuning formulae incorporated with classical anti‐windup strategies has been compared. The simulation results showed that the proposed method could give satisfactory performance in controlling the process

The contradictions of the film welfare economy, or, For the love of Treme

In the snarky atmosphere of the Twitterscape, the short but public tiff between director David Simon (The Wire, Treme), celebrity chef Anthony Bourdain, and Bravo Television's programming executive Andy Cohen looked like it had all the makings of a street game of the dozens..