Direct numerical simulations of turbulent premixed CH4/air flames were carried out using an inflow-outflow configuration to study the effects of equivalence ratio on the turbulent flame speed in lean mixtures. The inflow velocity was dynamically adjusted at a run-time to stabilize the flame brush location within the computational domain. Linear forcing was applied to maintain the turbulent intensities at desired levels. Numerous equivalence ratios near the lean limit were selected for the same turbulence properties and the normalized turbulent flame speed was shown to be a function of the equivalence ratio. Simulations were performed for over 80 eddy turnover times with the turbulent flame speed obtained by averaging the inflow velocity. Results revealed that the equivalence ratio does not have an explicit effect on the normalized turbulent flame speed over the lean limit. Analysis of flame surface area showed that the surface wrinkling produced by eddies of varying scales was not influenced by the change in equivalence ratios when the Karlovitz and Damkohler numbers are fixed. Finally based on the flame surface statistics flame surface normal is preferentially parallel to the most compressive strain rate direction for all equivalence ratios.

Uncertainties about the efficacy of influenza vaccination for populations with heart failure (HF) in preventing cardiovascular outcomes, as well as lack of effective vaccination strategies, may contribute to low vaccine coverage rate (VCR) in China and globally. We assessed the feasibility of a strategy to promote influenza vaccines in patients hospitalized with acute HF in China and to inform the design of a hybrid effectiveness-implementation cluster randomized trial to evaluate this strategy on mortality and hospital re-admission. We conducted a cluster randomized pilot trial involving 11 hospitals in Henan Province in China, with mixed-methods evaluation between December 2020 and April 2021. A process evaluation involved interviews with 51 key informants (patients, health professionals, policy makers). The intervention included education about influenza vaccination and availability of free vaccines administered prior to hospital discharge for HF patients, while usual care included attending community-based points of vaccination (PoV) for screening and vaccination. Implementation outcomes focused on reach, fidelity, adoption, and acceptability. Recruitment rates were assessed for trial feasibility. Effectiveness outcomes were influenza VCR, HF-specific rehospitalizations and mortality at 90 days. A total of 518 HF patients were recruited from 7 intervention and 4 usual care hospitals (mean of 45 participants per hospital per month). VCR was 89.9% (311/346, 86.1-92.8%) in the intervention group and 0.6% (1/172, 0.0-3.7%) in the control group. The process evaluation demonstrated reach to patients with lower socioeconomic and education status. There was good fidelity of the intervention components, with education and PoV set up processes being adapted to local hospital workflow and workforce capacity. Intervention was acceptable and adopted by patients and health professionals. However, outside of a trial setting, concerns were raised around vaccination reimbursement costs, workforce accountability and capacity. The intervention strategy appears feasible and acceptable for improving VCR in HF patients at county-level hospitals in China. Trial registration: This pilot trial is registered with the acronym PANDA II Pilot (Population Assessment of Influenza and Disease Activity) at ChiCTR.org.cn (ChiCTR2000039081).