A device (100; 200; 300; 400) for projecting a treatment liquid, comprising: - means (180; 280; 380) for supplying treatment liquid, - a rotary member (140; 240; 340) which is rotatably driven (Rx) about a central axis by driving means (110, 120, 170; 210, 220; 390) and which is configured to project the treatment liquid as a centrifugal liquid stream, and - means (103, 130, 170; 203, 230; 303, 330) for conveying a central air stream (F120, F140; F220, F240; F320, F340) to the rotary member (140; 240; 340), this central air stream being capable, on the one hand, of driving the centrifugal liquid stream along at least one spraying direction (Dp) as a sprayed liquid stream (Fp) and, on the other hand, of feeding an exhaust chamber (107; 207; 307) located upstream and radially about the rotary member (140; 240; 340) along the spraying direction (Dp), - the means (103, 130, 170; 203, 230; 303, 330) for conveying the central air stream (F120, F140; F220, F240; F320, F340) to the rotary member (140; 240; 340) comprising a partitioning member (130; 230; 330) which delimits, on the one hand, a first chamber (106; 206; 306) in which the central air stream circulates and, on the other hand, the exhaust chamber (107; 207; 307) configured to convey a central air stream to the interface with the centrifugal liquid stream, - the partitioning member (130; 230; 330) comprising means (137; 237; 337) for circulating the central air stream (F120, F140; F220, F240; F320, F340) from the first chamber (106; 206; 306) to the exhaust chamber (107; 207; 307), characterised in that: - these air circulation means (137; 237; 337) are unevenly distributed about the central axis, on two sides (Yg, Yd) of the partitioning member (130; 230; 330) which are diametrically opposite on either side of a plane comprising the central axis and a longitudinal axis perpendicular to the central axis, the partitioning member (130; 230; 330) being devoid of air circulation means (137; 237; 337) along the longitudinal axis, so that the spraying direction (Dp) of the sprayed liquid stream (Fp) defines an ogive-shaped profile which is based on the rotary member (140; 240; 340) and which is substantially flattened on both sides (Yg, Yd) diametrically opposite on either side of the plane. - means (180; 280; 380) for supplying treatment liquid, - a rotary member (140; 240; 340) which is rotatably driven (Rx) about a central axis by driving means (110, 120, 170; 210, 220; 390) and which is configured to project the treatment liquid as a centrifugal liquid stream, and - means (103, 130, 170; 203, 230; 303, 330) for conveying a central air stream (F120, F140; F220, F240; F320, F340) to the rotary member (140; 240; 340), this central air stream being capable, on the one hand, of driving the centrifugal liquid stream along at least one spraying direction (Dp) as a sprayed liquid stream (Fp) and, on the other hand, of feeding an exhaust chamber (107; 207; 307) located upstream and radially about the rotary member (140; 240; 340) along the spraying direction (Dp), - the means (103, 130, 170; 203, 230; 303, 330) for conveying the central air stream (F120, F140; F220, F240; F320, F340) to the rotary member (140; 240; 340) comprising a partitioning member (130; 230; 330) which delimits, on the one hand, a first chamber (106; 206; 306) in which the central air stream circulates and, on the other hand, the exhaust chamber (107; 207; 307) configured to convey a central air stream to the interface with the centrifugal liquid stream, - the partitioning member (130; 230; 330) comprising means (137; 237; 337) for circulating the central air stream (F120, F140; F220, F240; F320, F340) from the first chamber (106; 206; 306) to the exhaust chamber (107; 207; 307), characterised in that: - these air circulation means (137; 237; 337) are unevenly distributed about the central axis, on two sides (Yg, Yd) of the partitioning member (130; 230; 330) which are diametrically opposite on either side of a plane comprising the central axis and a longitudinal axis perpendicular to the central axis, the partitioning member (130; 230; 330) being devoid of air circulation means (137; 237; 337) along the longitudinal axis, so that the spraying direction (Dp) of the sprayed liquid stream (Fp) defines an ogive-shaped profile which is based on the rotary member (140; 240; 340) and which is substantially flattened on both sides (Yg, Yd) diametrically opposite on either side of the plane. - these air circulation means (137; 237; 337) are unevenly distributed about the central axis, on two sides (Yg, Yd) of the partitioning member (130; 230; 330) which are diametrically opposite on either side of a plane comprising the central axis and a longitudinal axis perpendicular to the central axis, the partitioning member (130; 230; 330) being devoid of air circulation means (137; 237; 337) along the longitudinal axis, so that the spraying direction (Dp) of the sprayed liquid stream (Fp) defines an ogive-shaped profile which is based on the rotary member (140; 240; 340) and which is substantially flattened on both sides (Yg, Yd) diametrically opposite on either side of the plane.