A New Electrode Design for Constant Volume Combustion Chamber

2021 ◽  
Author(s):  
James Shaffer ◽  
Omid Askari
Keyword(s):  
Combustion Chamber ◽  
Constant Volume ◽  
Electrode Design ◽  
Constant Volume Combustion ◽  
Constant Volume Combustion Chamber

A New Electrode Design for Constant Volume Combustion Chamber

2020 ◽  
Author(s):  
James Shaffer ◽  
Omid Askari
Keyword(s):  
Combustion Chamber ◽  
High Speed ◽  
Combustion Engine ◽  
Side Wall ◽  
Constant Volume ◽  
High Speed Photography ◽  
Electrode Design ◽  
Spark Plug ◽  
Constant Volume Combustion ◽  
Constant Volume Combustion Chamber

Abstract The current method of achieving center chamber ignition in the Plasma Combustion Research Laboratory’s (PCRL) Constant Volume Combustion Chamber (CVCC) utilizes either a standard or modified spark plug. The standard spark plug achieves a representation of side wall ignition (similar to a combustion engine) while modified sparkplugs have an extended electrode to allow for a center camber ignition. Two of these modified spark plugs are placed on both sides of the chamber and can effectively seal and isolate the chamber from the electrode. However, the process of welding electrode material to the spark plug is time consuming and requires a large number of modified electrodes to effectively test multiple different spark gap sizes. Also, the process of cleaning the electrode after experimentation shortens the electrode over time with no method of compensation other than creating a new electrode. The new electrode design aims to reduce the structural weakness by removing the welded joint as well as allowing for linear adjustment between testing while remaining firm during testing. The new design presented utilizes high-temperature epoxy, ceramic and grafoil seals to make adjustments easy and precise. The design was analyzed, prior to building and testing, based on the stress induced from the sealant, the total rated voltage, the rated temperature, and the fracture stress of the ceramic material. The stress induced in the electrode device was analyzed with FEA and the results were found to be within the limits of the material in terms of the compressive and fracture strength. The maximum voltage was found to be around 30 kV. The design is tested with 3 different electrode sizes where the largest electrode of 1.3 mm (0.05 in) has the same diameter as the current experimental set up. Two smaller electrodes 1 mm and 0.5 mm (0.04 in and 0.02 in) are tested as well to show the range and capabilities of the new system. The voltage and current data of the new and old system are compared and are found to be statistically similar within a 90 percent confidence level. The new electrodes is also compared to the previous system in terms of electrical resistance, the peak power each system can provide to the plasma, the visual shape and duration of the plasma through high speed photography. The range of operation for a successful design includes pressures from 20 mTorr to 40 atm, temperatures up to 280 C, and voltages up to 25 kV.

Electrode Design for Thermal and Non-Thermal Plasma Discharge Inside a Constant Volume Combustion Chamber

2021 ◽  
pp. 1-9
Author(s):  
James Shaffer ◽  
Omid Askari ◽  
Saeid Zare
Keyword(s):  
Combustion Chamber ◽  
Thermal Plasma ◽  
Plasma Discharge ◽  
Constant Volume ◽  
Electrode Design ◽  
Gap Size ◽  
Spark Plug ◽  
Constant Volume Combustion ◽  
Constant Volume Combustion Chamber ◽  
The Creation

Abstract Previous methods of achieving ignition in the Plasma, Combustion and Fluid imaging (PCFi) Laboratory's Constant Volume Combustion Chamber (CVCC) utilizes either a standard or modified spark plug. The standard spark plug achieves a representation of side wall ignition (similar to a combustion engine) while modified spark plug has an extended electrode to allow for a center camber ignition used for laminar burning speed (LBS) measurements. The creation of the modified spark plug required welding a stainless-steel wire to the electrode of the plug. The creation of these electrodes is time consuming and requires a large quantity to effectively test a wide range of parameters such as gap size or electrode geometry. Two custom-design electrodes are presented in this paper which extend the experimental range of the PCFi's CVCC system. Electrode Design A, gives the ability to test thin wire electrode with adjustability of gap size and different diameters through use of a compression fitting. This electrode design (i.e., tip-to-tip) is utilized with a traditional style of automotive ignition system (i.e., capacitive discharge) to study ignition process (i.e., thermal plasma) and spherical flame propagation. Electrode Design B, adds the ability to change tip geometry (i.e., plate-to-plate, tip-to-plate, tip-to-sphere, plate-to-sphere, etc). In this paper the plate-to-plate configuration is demonstrated to study uniform low-temperature nanosecond plasma discharge. Both electrode designs reduce structural weakness by removing the welded joint and allow for linear gap size adjustment. The electrode utilizes high-temperature epoxy, ceramic and grafoil seals to make parameter adjustments easy and precise. The design was analyzed, prior to building and testing, based on the stress induced from the sealant, the total rated voltage, the rated temperature and the fracture stress of the ceramic material. The stress induced in the electrodes was analyzed with Finite Element Analysis (FEA) and the results were found to be within the limits of the material in terms of the compressive and fracture strengths. The maximum voltage was found to be around 30 kV. Design A is presented with 3 different electrode diameters of 1.3, 1 and 0.5 mm and Design B which utilizes a threaded connection for adjustable tip geometry. A sample of data, visual and electrical, is presented for the newly created electrode with a 0.5 mm diameter as well as combustion images for up to 10 atm of initial pressure for methane-air mixture. The new electrode design was able to survive several months of experimental use with few issues compared with the previous welded design.

scholarly journals Development of a Constant Volume Combustion Chamber for Material Synthesis

2018 ◽  
Author(s):  
Mohammadrasool Morovatiyan ◽  
Martia Shahsavan ◽  
John Hunter Mack
Keyword(s):  
Combustion Chamber ◽  
Adaptive Mesh Refinement ◽  
Experimental Testing ◽  
Adaptive Mesh ◽  
Constant Volume ◽  
Operating Conditions ◽  
Materials Synthesis ◽  
Material Synthesis ◽  
Constant Volume Combustion ◽  
Constant Volume Combustion Chamber

A constant volume combustion chamber (CVCC) was constructed to enable material synthesis procedures that are sensitive to temperature, pressure, and ambient species concentrations. Material synthesis processes require specific operating conditions in order to carry out the desired chemical reactions and property transformations, including the creation of paper-templated metals and nanoparticles. The 1.13 liter combustion chamber includes a test stand for conducting the material synthesis experiments. A premixed fuel-air mixture is ignited at a desired equivalence ratio in order to produce the required synthesis conditions. In comparison to furnaces and ovens, this approach provides greater flexibility for materials synthesis procedures. Computational modeling using adaptive mesh refinement, alongside preliminary experimental testing results, confirms that the CVCC can provide the appropriate conditions to synthesize paper-templated metals. The approach demonstrates that the CVCC can be a viable alternative to a furnace for use in materials synthesis applications.

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