Augmented Spark Igniter (Yale Project Liquid)

Augmented Spark Ignitor (Yale Project Liquid)

May 2023 - Present

My Role: Fluid Supply Sub-team Lead, head of full feed system design, construction, and testing processes

Skillsets: CAD modeling, P&ID development, fluid mechanics, thermodynamics, hardware familiarity and construction

Objective:

Design and build a feed system to deliver desired quantities of Ethane and Nitrous Oxide to a bi-propellant rocket engine injector and augmented spark igniter (ASI), taking into account design changes from Yengine 1.0.

Results:

Successful design, construction, and testing of the feed system for a gaseous Ethane/gaseous Nitrous Oxide ASI, delivering an inlet pressure of 200 psi, capable of running in 1s, 2s, and 3s intervals, with effective venting and emergency shutoff/vent capabilities. Successful testing of ASI system components (leak tests, flow control tests).

CAD model of Yengine 2.0 Augmented Spark Igniter Feed System

Process:

The feed system’s new design has begun with the development of an Augmented Spark Igniter (ASI)-only feed system, as the full engine will involve an ASI as its source of ignition. A notable deviation from the Yengine 1.0 is that the propellant (ethane) and oxidizer (nitrous oxide) will exist at their vapor pressure during testing and will have resultant self-pressurizing capabilities, eliminating the need for external nitrogen pressurant. Redesigned CAD models and P&IDs were created with several iterations, based on new understanding of these propellants and standard safety procedures. In addition to those processes from the Yengine 1.0, additional considerations have been taken:

Flow Control - Needle valves are used to control flow and pressure through the system in addition to restriction orifices, and check valves are used to ensure flow is in the correct direction. Needle valves were tested to ensure their efficacy for providing a desired flow (see below).

Venting Mechanisms - New venting systems, such as relief valves and burst disks, have been added to accommodate differences in the new system’s design, ensuring safety during testing.

Cleaning and Handling - New procedures were developed for the proper cleaning and storage of individual parts of the system at every point of construction for the prioritization of safety with propellants.

Ease of Assembly - A switch from NPT piping to tubes with compression fittings reduces constraints and challenges which arose during construction, such as twisting instruments and wires in small spaces.

Testing:

Needle Valve Characterization - Needle valves serve as the fine flow control mechanism in the ASI system during testing in order to make small changes to flow in the system. When the needle valves are adjusted so that the ASI is functional, they can be replaced by a permanent orifice which corresponds to the flow coefficient of the needle valve. Therefore, we needed to determine the relationship between the flow coefficient (Cv) of our needle valve and how open/closed the valve is. The supplier of our needle valves (Swagelok) claims a fully open flow coefficient of 0.37 with a linearly proportional drop to 0 as the valve is closed. I tested this claim by flowing filtered air through the needle valve at different amounts of turns open from one pressurized closed tube into a tank of known volume while measuring the pressure on each side of the valve. Using the change in pressure across the valve over time, along with ideal gas assumptions and equations describing flow coefficient for systems with compressible flow, I determined the flow coefficients of the valve at various amounts of turns open to develop a curve. While not completely linear, the club’s professional advisors concluded that the results suggested that we could use a linear model to predict the flow coefficient of the needle valves.

Leak Testing - Standard leak testing procedures using pressurized nitrogen were employed based on the recommendations of the Friends of Amateur Rocketry (FAR), who hosts the in which our rocket will compete.

Static Fire Testing - Static fire tests of the ASI were successfully conducted in February and May of 2024 at Stony Creek Quarry. I operated the test stand alongside other sub-team leaders and Yale Environmental Health and Safety representatives while providing adjustments using a model which I developed to predict Oxidizer-Fuel ratios based on live pressure readings. The video below was filmed and produced by a member of our team.

Results & Discussion:

An ASI system and full engine have been fully designed, with the ASI system components costing ~$2000 total. The ASI system has completed construction and has been successfully tested multiple times with propellants. The ASI, in its design, construction and testing, acts as a functional learning experience and its success in completion will continue to dictate our approach to a full engine.

The experience of designing the Augmented Spark Ignitor as the leader of the feed system team has been formative. In addition to technical knowledge, this position has given me the opportunity to develop skills in project management, communication, and leadership.