Investigation of scaling criteria and matching method of overall cooling effectiveness with thermal radiation

Ever-improving gas temperature and infrared stealth requirements for aero engines will make thermal radiation become a vital contribution to total heat transfer. To evaluate the cooling performance in laboratory conditions, the corresponding scaling criteria, and matching methods of overall cooling effectiveness (Φ) considering thermal radiation need to be studied. In this paper, a one-dimensional, simplified heat transfer analysis expression with thermal radiation was derived based on the principle of heat flux conservation. The scaling criterion about radiation (radiation Biot number: Bi_r) was proposed. The scaling criteria of Φ were established to guide experiments conducted reveal the Φ in actual engine condition. These criteria were well verified with an impingement-effusion model applied afterburner heat shield by conjugate radiation simulations. Two matching methods of Bi_r in scaling criteria were proposed and investigated in detail, which include adjusting the power of the radiation source alone and coating high emissivity paint combined with a lower power radiation source. The results indicate that thermal radiation has a very remarkable effect on Φ of the film plate. The area-average Φ decreased by 22.8%, 15.9%, 12.5% and 10.4% for blowing ratio M = 0.2, 0.4, 0.6 and 0.8, respectively. The Bi_r and Φ can be accurately matched under laboratory conditions using the two matching methods. The relative matching deviation of Φ between the laboratory and the engine conditions is less than 3%.