Reddit mentions of Gas Dynamics, Volume 1

I will assume you have a pretty solid background in mathematics and physics. I would recommend a touch-up on thermodynamics/gas dynamics and combustion -

• [https://www.amazon.com/Gas-Dynamics-Maurice-J-Zucrow/dp/047198440X]
  
• [https://www.amazon.com/Introduction-Combustion-Concepts-Applications-ebook/dp/B005LIYP98/ref=sr_1_1?s=books&ie=UTF8&qid=1484792327&sr=1-1&keywords=turns+combustion]
  
  For hobby-level devices, I would look to your budget first for your propellants. Since you're doing petrol/GOX as liquid-gas, I would try looking into shear-coax or swirl-coax injectors. Swirl coax was popular among Russian designs due to their lack of precision manufacturing capabilities early on. This translates to cheaper manufacturing today. Eventually they evolved the injectors into very solid designs. A good guideline is available from the many AIAA papers of Bazarov such as [http://arc.aiaa.org/doi/pdf/10.2514/6.2007-5684].