Considerations and complications with "first principles" dynamic modelling of industrial compressors

Readily available processing hardware and "off-the-shelf" (OTS) simulation software has made "high fidelity" first principles models of both steady and transient states, for both axial and centrifugal industrial compressors, relatively easy to construct. These high-fidelity models are finding their way into "real-time. digital twin" performance monitors, front-end engineering design, and post-design – pre-construction compressor performance evaluation. The compressor models are useful for reliably demonstrating the compressor and – to some degree, based on the complexity of the model – process response to various operating conditions. Once the model is constructed, it is trivial to run a "what-if" analysis of compressor performance to answer questions related to (a) recommendations or validation of the recycle/vent valve size and actuation speed, (b) general piping layout and sizing around the compressor, (c) and hot gas bypass requirements, to name a few. This paper takes a practical approach in discussing the compressor and process parameters necessary for building these dynamic "high-fidelity" industrial-compressor models. We identify compressor inputs and compressor responses that are faithfully modeled by first-principle equations available in the simulation software and those that typically require a compromise between an "ab initio" and data-fitting approximation. We discuss the simulation's tendency to overstate pressure excursions during surge events and understate the compressor operation in the "stonewall" region. We also discuss using the simulator software's compressor-stage enthalpy calculations to predict and quantify the compressor train reverse rotation. We use our broad experience and understanding of the compressor operation and simulation and our experience with the AVEVA™ Dynamic-Simulation "OTS" simulation software as the basis for this discussion.

Fabrication and Testing of the Cold Gas Propulsion System Flight Unit for the Adelis-SAMSON Nano-Satellites

Adelis-SAMSON is a nano-satellite mission aimed at performing geo-location of target signals on Earth using a tight three-satellite formation in space. To maintain formation, each nano-satellite is equipped with a cold gas propulsion system. The design, qualification, and integration of the Adelis-SAMSON nano-satellite propulsion system is presented in this paper. The cold gas propulsion system mass is approximately 2 kg, takes a volume of 2U, and generates a thrust of 80 mN from four thrusters using krypton as a propellant. We first present the propulsion system requirements and corresponding system configuration conceived to meet the mission requirements. Subsequently, we present the system architecture while listing all the components. We overview the particular role and qualification process of four of the propulsion system’s components: the propellant tank, thruster assembly, pressure regulators, and fill and vent valve. We detail the tests performed on each component, such as proof pressure tests, vibration tests, and external leak tests. Finally, we present the propulsion system level tests before delivery for satellite integration and discuss the propulsion system’s concept of operations.

Simulation Based Process Optimization for Additive Manufacturing

Additive manufacturing is finding increasing applications in industries ranging from electronics to aerospace and even medical sectors. However, these machines are very expensive which hinders researcher investigations. Thus it is important to have an alternative data source for such machines. A probable solution is to develop a simulator to replicate such machine based on same input parameters and thus obtain results similar to that from an actual machine. This would help developers and researchers investigate several aspects of additive manufacturing without using the actual machine. This paper reports an investigation conducted to study the behavior of a selective laser melting machine under different scenarios. Influences due to components such as vacuum pump, reciprocating pump, gas inlet valve, vent valve, elevator and wiper have been included. Experimental result data has been used to build codes in C# software to program the PLC simulator. Validation experiments confirmed simulation output. The present work helps the end user to inspect real time simulations such as vacuum creation, inert gas atmosphere progression. Thus, simulation results offer time and resource savings to an additive manufacturing end user by him/her make informed decisions by supplying exact parameter settings suitable to his/her manufacturing requirements.

Evaluation of Evaporative Emission and Feasibility of an Onboard Refueling Vapor Recovery System for Scooters

This paper aims at the development of a novel onboard refueling vapor recovery (ORVR) system for scooters. The corresponding feasibility and evaporative emission are evaluated so that this preliminary study may offer important contributions for developing an effective ORVR system in Taiwan. A survey of research is initially conducted to compare the evaporative emission of the ORVR systems mounted on vehicles with that of the vapor recovery systems of Stage II installed at gas stations. The results show that the ORVR technology possesses better controllability and lower cost. Then, a novel ORVR system for scooters consisting of a self-made fuel tank, a self-made carbon canister, a vapor pipe, a fuel limit vent valve, and a surge protector etc. is developed and tested. The proposed self-made carbon canister possesses the storage capacity of fuel vapor large enough to perform the adsorption tests of diurnal and hot soak for as long as three consecutive days. Finally, the designed ORVR system is installed on a scooter and tested for evaporative emission under the regulation of Taiwan so as to check if it fulfills the requirements. The results are further compared with those with the evaporative emission control system (EVAP). A significant improvement on the leaking problem of fuel vapor is gained by using the proposed ORVR system. Consequently, the study can offer a valuable reference for developing an economical and effective ORVR system in the future.