Cool Burning Gas Generant Composition for Inflatable Restraint Systems
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Solution Overview
Problem
Current gas generant formulations for automotive inflatable restraint systems face challenges in achieving high gas output with low flame temperatures to minimize burns and thermal damage, while also reducing filtration and heat sink requirements, and maintaining performance specifications for particulate matter expulsion.
Innovation Solution
A cool burning gas generant composition comprising a bismuth-containing compound, such as bismuth citrate, bismuth subsalicylate, or copper bismuth hydroxy nitrate, combined with a copper-containing oxidizer and fuel, which generates combustion products in a liquid phase at a maximum flame temperature of less than 1700K, allowing for reduced filtration and heat sink components without compromising safety or performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If high gas output is achieved with conventional gas generant formulations, then sufficient gas mass flow is provided to achieve required work impulse, but high flame temperatures result causing burns and thermal damage
Solution Approach 1:
The patent changes the chemical composition parameters of the gas generant by incorporating bismuth-containing compounds (such as bismuth suboxide, bismuth oxide, or bismuth metal) combined with copper-containing compounds. This compositional parameter change fundamentally alters the combustion characteristics, reducing flame temperature from conventional high temperatures to below 1700K while maintaining high gas output through optimized fuel-oxidizer ratios and selection of specific compounds like guanidine nitrate, tetrazole derivatives, and metal nitrates.
Solution Approach 2:
The patent employs composite material strategy by creating a multi-component gas generant formulation that combines bismuth-containing compounds, copper-containing compounds, fuels, and oxidizers into a synergistic composition. The bismuth and copper compounds work together to control flame temperature, while the fuel-oxidizer system provides high gas generation. This composite approach allows simultaneous achievement of low temperature combustion and high productivity that cannot be realized with single-component systems.
2Weight of stationary object
If filtration systems are reduced to mitigate heat sink requirements, then inflator weight is reduced, but particulate matter expulsion specifications may not be met
Solution Approach 1:
The patent converts the potential harm of particulate matter into a beneficial outcome by formulating the gas generant to produce combustion products that naturally aggregate into large, filterable particles. The bismuth and copper compounds form molten slags during combustion that solidify into particulates of controlled size and morphology. These particulates, rather than being harmful fine dust, become easily filterable matter that meets emission specifications while allowing for reduced filtration systems and lower inflator weight.
3Object-affected harmful factors
If flame temperature is reduced to below 1700K, then burns and thermal damage are minimized, but gas mass flow and work impulse may be insufficient
Solution Approach 1:
The patent optimizes multiple parameters simultaneously: selects fuels with high gas yield characteristics (guanidine nitrate, tetrazole compounds), adjusts oxidizer-to-fuel ratios to maximize gas production at lower temperatures, incorporates bismuth and copper compounds in specific proportions to control flame temperature, and modifies particle size and density parameters of the composite formulation. These coordinated parameter changes ensure that gas mass flow and work impulse requirements are met even at reduced flame temperatures below 1700K.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The composition achieves a high gas yield and linear burn rate while minimizing particulate output and thermal damage, enabling filterless inflator designs that provide effective restraint and protection without burns, with a tank residue of less than 1 gram post-deployment.
Implementation Method 1
a cool burning gas generant composition... has a maximum flame temperature at combustion (Tc) of less than or equal to about 1700K
Implementation Method 2
generates combustion products in a liquid phase at a maximum flame temperature of less than 1700K
Data Source
AI summary
Cool burning gas generant compositions for an automotive inflatable restraint system are provided that include a bismuth-containing compound selected from the group consisting of: bismuth citrate, bismuth subsalicylate, bismuth hydroxide, copper bismuth hydroxy nitrate, bismuth subcarbonate, bismuth suboxalate, and combinations thereof. The gas generant comprises at least one copper-containing component. The gas generant includes at least one oxidizer, fuel, and optional coolant. The maximum flame temperature at combustion (Tc) of less than or equal to about 1700K (1,427° C.). The cool burning gas generant composition generates liquid phase combustion products making it suitable for use in a filterless inflatable restraint system. Copper and bismuth present in the cool burning gas generant composition react to form an alloy having a melting point at or near the maximum flame temperature at combustion (Tc).