Computational Optimization of Pressure Wave Reflection on the Piston Surface for Single Point Autoignition Gasoline Engine with Colliding Pulsed Supermulti-Jets Leading to Noiseless-High Compression and Nearly-Complete Air-Insulation 2019-01-0235
Our previous research (Naitoh, patents, 2011, 2012) proposed a new engine concept based on pulsed supermulti-jets colliding at a small area around the chamber center. It was expected to provide high thermal efficiencies for two reasons. One reason is nearly-complete air-insulation due to the effect of the jets encasing the burned gas around the chamber center. The other reason is noiseless high compression around the collision point leading to less exhaust gas energy. We have done primitive combustion experiments for three prototype engines based on the supermulti-jets colliding with pulse (Naitoh et al., SAE paper, 2016). However, optimizations on engine geometry and components are necessary for improving performance and stability of combustion. Thus, in our previous reports (Yamagishi et al. SAE papers, 2014, 2016), three-dimensional computations for the unsteady compressible Navier-Stokes equation with the Cubic-interpolated pseudo-particle (CIP) method were qualitatively conducted on the latest prototype engine. We here developed a new numerical code to quantitatively simulate the compression level caused by the jets colliding with pulse. This is achieved by adding a staggered grid method for improving conservativity of physical quantities, and also by comparing with theoretical values or experiments. In addition, we examine which has larger effect on overall compression ratio, (1) first compression around the chamber center due to the supermulti-jets colliding with pulse or (2) secondary effect of pressure wave reflection on the piston surface, while varying conditions of engine. This optimization study is important in order to achieve higher compression ratio leading to lower exhaust energy.
Aya Hosoi, Remi Konagaya, Sota Kawaguchi, Yasuhiro Sogabe, Yuya Yamashita, Ken Naitoh