The armed helicopter is in the blind area of radar detection when performing low-altitude missions, but more attention should be paid to the threat of infrared guided weapons. Integrated into the rear fuselage of the helicopter, the infrared suppressor offers excellent stealth capabilities due to its small spatial footprint and the ability of rapid mixing and cooling at short distances. Over the past decades, significant progress has been made in understanding the mechanisms of infrared suppression, enhancing the performance of the suppressor in the areas such as cold-air injection, cold-hot flow mixing, and obscuration of high-temperature components. However, the infrared stealth effectiveness of the suppressor from the top and bottom perspectives has always been suboptimal, necessitating the search for optimal suppressor structures for further improvement. Furthermore, during the helicopter cruising, the suppressor exhaust is inevitably affected by the forward flow. Therefore, it is essential to study the performance of the infrared suppressor under the coupled conditions of forward flow, thermal exhaust, and rotor downwash. In this study, an integrated physical model of the infrared suppressor is constructed, which includes the outer skin and the exhaust system (Fig.1). On the basis of the verification of ground model experiment, the simulation of forward flow and variations in the exhaust flow angle are added to assess how these changes affect the flow dynamics, heat transfer, and spatial distribution of infrared radiation intensity within the suppressor. The infrared radiation intensity was calculated using forward-backward ray-tracing method. The results of ground experimental measurement and simulation calculation meet the error requirements, proving the calculation method in this paper is feasible. The increase of the forward flow velocity will increase the ejection coefficient of the lobed nozzle (Fig.10), but will reduce the total pressure recovery coefficient of the exhaust system (Fig.12), and the exhaust of the suppressor is blocked at higher forward flow velocity (Fig.11). Reducing the backward deflection angle γ can solve the problem of poor exhaust, thereby increasing the flow area and improving the total pressure recovery coefficient. However, when the outlet area of the exhaust lobe is constant, its cross-sectional area decreases with the decrease of γ, resulting in a decrease in the ejection coefficient of the exhaust system, an increase in the static pressure in the mixing tube, and a decrease in the total pressure recovery coefficient. When the forward flow velocity increases, the infrared radiation of each band is mainly reduced by reducing the exhaust and internal wall temperature. The installation of a curved deflector at the downwash flow inlet of the suppressor can block the internal high-temperature mixing tube and effectively reduce the infrared radiation intensity at the top of the suppressor (Fig.18). The radiation shielding baffle at the downstream of the exhaust on the longitudinal section makes the suppressor show a high radiation level only in a small range of 30° (Fig.19). The balance of the advantages and disadvantages brought by changing the backward deflection angle γ of the exhaust lobe determines its influence on the aerodynamic performance of the mixing tube. The external skin downstream of the suppressor exhaust will form a high temperature zone higher than the ambient temperature of about 20 K, and the area of the high temperature zone decreases first and then increases with the decrease of γ. The infrared radiation intensity in the 3-5 μm band is mainly derived from the internal high temperature wall, while the 8-14 μm band is determined by the internal high temperature wall and the external skin. When the forward flow velocity increases from 15 m/s to 55 m/s, the peak infrared radiation intensity of the suppressor decreases by about 50% in the 3-5 μm band and about 20% in the 8-14 μm band. In general, when γ is 60°, the mixing tube has good aerodynamic performance, the local high temperature zone of the external skin is the smallest, and it has good infrared stealth performance at all detection angles.