Residual-effected homogeneous charge compression ignition at a low compression ratio using exhaust reinduction

Abstract

Studies have been conducted to assess the performance of homogeneous charge compression ignition (HCCI) combustion initiated by exhaust reinduction from the previous engine cycle. Reinduction is achieved using a fully flexible electrohydraulic variable-valve actuation system. In this way, HCCI is implemented at low compression ratio without throttling the intake or exhaust, and without preheating the intake charge. By using late exhaust valve closing and late intake valve opening strategies, steady HCCI combustion was achieved over a range of engine conditions. By varying the timing of both valve events, control can be exerted over both work output (load) and combustion phasing. In comparison with throttled spark ignition (SI) operation on the same engine, HCCI achieved 25–55 per cent of the peak SI indicated work, and did so at uniformly higher thermal efficiency. This was accompanied by a two order of magnitude reduction in NO emissions. In fact, single-digit (ppm) NO emissions were realized under many load conditions. In contrast, hydrocarbon emissions proved to be significantly higher in HCCI combustion under almost all conditions. Varying the equivalence ratio showed a wider equivalence ratio tolerance at low loads for HCCI.

Physics-based closed-loop control of phasing, peak pressure and work output in HCCI engines utilizing variable valve actuation

“…Physics-based closed-loop control has also been implemented on a single cylinder research engine (for engine details see [4]). For these preliminary experiments, IVC is held constant, resulting in a fairly constant combustion phasing as long as the IVO/EVC timings lie along a particular linear map (see [8] and [4] for details on this map).…”

“…For these preliminary experiments, IVC is held constant, resulting in a fairly constant combustion phasing as long as the IVO/EVC timings lie along a particular linear map (see [8] and [4] for details on this map). Peak pressure control was realized by synthesizing a Linear Quadratic Regulator (LQR) controller from a linearization of Equation 19 [8].…”

“…This process leads to a low post-combustion temperature, which significantly reduces N O x emissions. There are several methods used to initiate HCCI, such as heating or pre-compressing the intake air ( [1], [2]), trapping exhaust gases from the previous cycle by closing the exhaust valve early [3], modulating intake and exhaust flows using variable valve actuation (VVA) to re-induct exhaust from the previous cycle ( [4], [3]) or some combination of these ( [5], [6]). …”

Real-time control oriented HCCI engine cycle-to-cycle dynamic modelling

“…First, the sensitivity of HCCI combustion makes it difficult to control. Inaccurate control leads to misfiring or knocking, which is very harmful to the engine [3,4] . Second, the operation range of HCCI engines is relatively limited [5] .…”

Contraction and sum of squares analysis of HCCI engines

“…Residual-affected homogeneous charge compression ignition holds great promise as a means to reduce N O x emissions and increase efficiency in internal combustion engines (Caton et al, 2003). During an engine cycle, fresh reactant charge and exhaust products from the previous cycle are inducted through the intake and exhaust valves, respectively.…”