Discussion Overview
The discussion revolves around determining the voltage required to create a spark in a car engine's combustion chamber, specifically focusing on a stoichiometric fuel mixture and a 1mm spark plug gap. Participants explore the relationship between gas pressure, temperature, and the necessary voltage for ignition without considering additional variables like gas turbulence.
Discussion Character
- Exploratory
- Technical explanation
- Debate/contested
Main Points Raised
- One participant inquires about an algorithm to calculate the required voltage for sparking based on gas pressure and temperature, explicitly excluding other variables.
- Another participant notes that a simple formula for low pressures may not apply to internal combustion engine conditions, suggesting that pressures before combustion are around 150 psi.
- A participant mentions that approximately 5000 volts are needed for sparking over a 1mm gap at standard atmospheric pressure, questioning the voltage needed for a fuel/air mixture under similar conditions.
- It is stated that the breakdown voltage of dry air at standard temperature and pressure (STP) is 32MV/m, equating to 32kV/mm, but actual breakdown occurs at lower voltages influenced by environmental factors like moisture and dust.
- One participant humorously relates the voltage needed for lightning arcs to the discussion, estimating that cloud-to-cloud lightning could require significantly higher voltages if not for the presence of water in clouds.
- A suggestion is made to expect a voltage range between 10 and 30 kV for the spark.
- A participant expresses difficulty in finding relevant information or research on the topic.
Areas of Agreement / Disagreement
Participants express various estimates and considerations regarding the voltage needed for sparking, but there is no consensus on a specific value or formula applicable to the conditions described. Multiple competing views and uncertainties remain evident throughout the discussion.
Contextual Notes
Participants acknowledge that environmental factors, such as humidity and particulates, can significantly affect the breakdown voltage, indicating limitations in their estimates. The discussion also highlights the complexity of modeling ignition in engine conditions.
