1. Center for Innovation in Gas Research and Utilization (CIGRU), Department of Mechanical and Aerospace Engineering, West Virginia University, Morgantown, West Virginia 26506, USA
2. Center for Combustion Energy, Key Laboratory for Thermal Science and Power Engineering of the Ministry of Education of China, Department of Energy and Power Engineering, Tsinghua University, Beijing 100084, China
3. Department of Applied Physics and Electronics, Umeå University, 901 87 Umeå, Sweden