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Are spark plugs used in kero-LOx engine(say J1 engines)? If so, then there are two major issues when using spark plug to ignite kerosene.

  1. Wetting of the spark plug causes spark to be smaller and the energy might be less. Sparks tend to be larger when used in gas media. Wetting of the electrode reduces spark size.
  2. Due to the above, the temperature achieved might be less and hence kerosene might not be vaporised completely before reaching flash point.

How are these issues overcome?

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    $\begingroup$ @RussellBorogove Check Launcher space, a new startup from NY. They are using spark plug based ignition for kerosene! mobile.twitter.com/launcherspace/status/933101686700179457 $\endgroup$ – karthikeyan Sep 12 '18 at 19:25
  • $\begingroup$ I don’t know how they are making it happen! $\endgroup$ – karthikeyan Sep 12 '18 at 19:25
  • $\begingroup$ What do you do with the spark plug after a successful ignition? I should not melt and burn through the combustion chamber wall. If the wall needs liquid cooling, the spark plug would need it too. The spark plug should not disturb the cooling of the surrounding wall. $\endgroup$ – Uwe Sep 12 '18 at 21:12
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    $\begingroup$ @karthikeyan I think there are some interesting questions and/or issues here. If you rewrote this question it could be reopened, but the better way would be to ask a new one. If you gave a specific example (link and possibly image as well) of a company, product, or research within the question itself (rather than in a comment) and asked something like "What exactly are they doing here?" or better yet "What would be the technical challenges to getting this to work?" there's a better chance for the question to stay open. $\endgroup$ – uhoh Sep 13 '18 at 2:16
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    $\begingroup$ @uhoh as you suggested. I will gather my materials and get back soon. Thanks $\endgroup$ – karthikeyan Sep 13 '18 at 8:36
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Spark igniters are commonly used for hydrogen-fueled engines, but chemical igniters are preferred for kerosene engines, largely because of the concerns you mention.

There's more detail in this Q & A.

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  • $\begingroup$ ah! Even I had commented! But still I a, seeing a lot of spark plug IC engine designs and precombustion chamber design. Wonder if larger voltage could kick in a kerosene spark ignition? $\endgroup$ – karthikeyan Sep 12 '18 at 19:19
  • $\begingroup$ I don't think ICE engine design is generally comparable to rocket engine design even if the fuel remains the same, due to the rather huge volume/flow differences. They would seem to exacerbate the wetting concerns pointed out in the question. $\endgroup$ – Saiboogu Sep 12 '18 at 19:45
  • $\begingroup$ @russell please do check this space.stackexchange.com/q/30668/511. Put up a new question based on @uhoh’s suggestion. $\endgroup$ – karthikeyan Sep 14 '18 at 0:17

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