Homogeneous charge compression ignition (HCCI) combustion: Mixture preparation and control strategies in diesel engines

Homogeneous charge compression ignition (HCCI) combustion in diesel engines can provide cleaner operation with ultralow NOx and soot emissions. While HCCI combustion has generated significant attention in the last decade, however, till date, it has seen very limited application in production diesel engines. HCCI combustion is typically characterized by earlier than top-dead-center (pre-TDC) phasing, very high-pressure rise rates, short combustion durations, and minimal control over the timing of the combustion event. To offset the high reactivity of the diesel fuel, large amounts of exhaust gas recirculation (EGR) (30–60%) are usually applied to postpone the initiation of combustion, shift the combustion toward TDC, and alleviate to some extent, the high-pressure rise rates and the reduced energy efficiency. In this work, a detailed analysis of HCCI combustion has been carried out on a high-compression ratio (CR), single-cylinder diesel engine. The effects of intake boost, EGR quantity/temperature, engine speed, injection scheduling, and injection pressure on the operability limits have been empirically determined and correlated with the combustion stability, emissions, and performance metrics. The empirical investigation is extended to assess the suitability of common alternate fuels (n-butanol, gasoline, and ethanol) for HCCI combustion. On the basis of the analysis, the significant challenges affecting the real-world application of HCCI are identified, their effects on the engine performance quantified, and possible solutions to overcome these challenges explored through both theoretical and empirical investigations. This paper intends to provide a comprehensive summary of the implementation issues affecting HCCI combustion in diesel engines.

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

International Journal of Engine Research ◽

10.1243/146808703322223306 ◽

2003 ◽

Vol 4 (3) ◽

pp. 163-177 ◽

Cited By ~ 53

Author(s):

P. A. Caton ◽

A. J. Simon ◽

J. C. Gerdes ◽

C. F. Edwards

Keyword(s):

Compression Ratio ◽

Equivalence Ratio ◽

Homogeneous Charge Compression Ignition ◽

Compression Ignition ◽

Single Digit ◽

Hcci Combustion ◽

Actuation System ◽

Order Of Magnitude ◽

No Emissions ◽

Homogeneous Charge

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.

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Chemiluminescence Measurements of Homogeneous Charge Compression Ignition (HCCI) Combustion

10.4271/2006-01-1520 ◽

2006 ◽

Cited By ~ 21

Author(s):

R. Augusta ◽

David E. Foster ◽

J. B. Ghandhi ◽

J. Eng ◽

P. M. Najt

Keyword(s):

Homogeneous Charge Compression Ignition ◽

Compression Ignition ◽

Hcci Combustion ◽

Homogeneous Charge

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Characterizing the cyclic variability of ignition timing in a homogeneous charge compression ignition engine fuelled with n-heptane/iso-octane blend fuels

International Journal of Engine Research ◽

10.1243/14680874jer01408 ◽

2008 ◽

Vol 9 (5) ◽

pp. 361-397 ◽

Cited By ~ 72

Author(s):

M Shahbakhti ◽

C R Koch

Keyword(s):

Equivalence Ratio ◽

Homogeneous Charge Compression Ignition ◽

Coolant Temperature ◽

Cyclic Variation ◽

Compression Ignition ◽

Ignition Timing ◽

Compression Ignition Engine ◽

Hcci Combustion ◽

Cyclic Variations ◽

Homogeneous Charge

The cyclic variations of homogeneous charge compression ignition (HCCI) ignition timing is studied for a range of charge properties by varying the equivalence ratio, intake temperature, intake pressure, exhaust gas recirculation (EGR) rate, engine speed, and coolant temperature. Characterization of cyclic variations of ignition timing in HCCI at over 430 operating points on two single-cylinder engines for five different blends of primary reference fuel (PRF), (iso-octane and n-heptane) is performed. Three distinct patterns of cyclic variation for the start of combustion (SOC), combustion peak pressure ( Pmax), and indicated mean effective pressure (i.m.e.p.) are observed. These patterns are normal cyclic variations, periodic cyclic variations, and cyclic variations with weak/misfired ignitions. Results also show that the position of SOC plays an important role in cyclic variations of HCCI combustion with less variation observed when SOC occurs immediately after top dead centre (TDC). Higher levels of cyclic variations are observed in the main (second) stage of HCCI combustion compared with that of the first stage for the PRF fuels studied. The sensitivity of SOC to different charge properties varies. Cyclic variation of SOC increases with an increase in the EGR rate, but it decreases with an increase in equivalence ratio, intake temperature, and coolant temperature.

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Active valvetrain for homogeneous charge compression ignition

International Journal of Engine Research ◽

10.1243/146808705x30396 ◽

2005 ◽

Vol 6 (4) ◽

pp. 377-397 ◽

Cited By ~ 10

Author(s):

N Milovanovic ◽

J G W Turner ◽

S A Kenchington ◽

G Pitcher ◽

D W Blundell

Keyword(s):

Homogeneous Charge Compression Ignition ◽

Cold Start ◽

Smooth Transition ◽

Engine Management System ◽

Compression Ignition ◽

Load Range ◽

Hcci Combustion ◽

Particulate Matter Emissions ◽

Mode Transitions ◽

Homogeneous Charge

Homogeneous charge compression ignition (HCCI), also known as controlled autoignition (CAI) or the premixed charge compression ignition (PCCI) engine concept, has the potential to be highly efficient and to produce low NOx, carbon dioxide, and particulate matter emissions. However, it experiences problems with cold start in a gasoline HCCI engine, running at idle and at high loads, which, together with controlling the combustion over the entire speed/load range, limits its practical application. A way to overcome these problems is to operate the engine in ‘hybrid mode’, where the engine operates in HCCI mode at low, medium, and cruising loads and can switch to or from spark ignition (SI) or diesel (CI) mode for a cold start, idle, and higher loads. Such an engine will have frequent changes in engine load and speeds and therefore frequent transitions between HCCI and SI combustion modes. The valvetrain and engine management system (EMS) have to provide a successful control of HCCI mode and a fast and smooth transition keeping all relevant engine parameters within an acceptable range. Consequently, this leads to high demands on the valvetrain and therefore a need for a very high degree of flexibility. The aim of this paper is to present the potential of a fully variable valvetrain (FVVT) system, the Lotus active valvetrain (AVT™), for controlling HCCI combustion and enabling fast and smooth mode transitions in a HCCI/SI engine fuelled with commercially available gasoline (95 RON) and in a HCCI/DI engine fuelled with diesel (50 CN) fuel.

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A physics-based approach to the control of homogeneous charge compression ignition engines with variable valve actuation

International Journal of Engine Research ◽

10.1243/146808705x30512 ◽

2005 ◽

Vol 6 (4) ◽

pp. 361-375 ◽

Cited By ~ 48

Author(s):

G M Shaver ◽

M J Roelle ◽

P A Caton ◽

N B Kaahaaina ◽

N Ravi ◽

...

Keyword(s):

Internal Combustion Engines ◽

Homogeneous Charge Compression Ignition ◽

Control Strategies ◽

Combustion Process ◽

System Control ◽

Compression Ignition ◽

Variable Valve Actuation ◽

Variable Valve ◽

Homogeneous Charge ◽

Valve Actuation

Homogeneous charge compression ignition (HCCI) is a promising low-temperature combustion strategy for reducing NOx emissions and increasing efficiency in internal combustion engines. However, HCCI has no direct combustion initiator and, when achieved by reinducting or trapping residual exhaust gas with a variable valve actuation (VVA) system, becomes a dynamic process as the temperature of the residual gas couples one cycle to the next. These characteristics of residual-affected HCCI present a challenge for control engineers and a barrier to implementing HCCI in a production engine. In order to address these challenges, this paper outlines physics-based control strategies for both the VVA system and the HCCI combustion process. The results show that VVA system control can provide arbitrary valve timings on a cycle-to-cycle basis, enabling tight control of HCCI. By abstracting these valve timings further into an inducted gas composition and an effective compression ratio, model-based controllers can be developed to control simultaneously load and combustion timing in an HCCI engine.

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Analysis of Homogeneous Charge Compression Ignition (HCCI) Engines for Cogeneration Applications

Journal of Energy Resources Technology ◽

10.1115/1.2131883 ◽

2005 ◽

Vol 128 (1) ◽

pp. 16-27 ◽

Cited By ~ 10

Author(s):

Salvador M. Aceves ◽

Joel Martinez-Frias ◽

Gordon M. Reistad

Keyword(s):

Diesel Engines ◽

High Efficiency ◽

Homogeneous Charge Compression Ignition ◽

Utilization Efficiency ◽

Small Scale ◽

Compression Ignition ◽

Hcci Engines ◽

Si Engines ◽

Prime Movers ◽

Homogeneous Charge

This paper presents an evaluation of the applicability of homogeneous charge compression ignition (HCCI) engines for small-scale cogeneration (<1MWe) in comparison to five previously analyzed prime movers. The five comparator prime movers include stoichiometric spark-ignited (SI) engines, lean burn SI engines, diesel engines, microturbines, and fuel cells. The investigated option, HCCI engines, is a relatively new type of engine that has some fundamental differences with respect to other prime movers. The prime movers are compared by calculating electric and heating efficiency, fuel consumption, nitrogen oxide (NOx) emissions, and capital and fuel costs. Two cases are analyzed. In case 1, the cogeneration facility requires combined power and heating. In case 2, the requirement is for power and chilling. The results show that HCCI engines closely approach the very high fuel utilization efficiency of diesel engines without the high emissions of NOx and the expensive diesel fuel. HCCI engines offer a new alternative for cogeneration that provides a combination of low cost, high efficiency, low emissions, and flexibility in operating temperatures that can be optimally tuned for cogeneration systems. HCCI is the most efficient engine technology that meets the strict 2007 CARB NOx standards for cogeneration engines, and merits more detailed analysis and experimental demonstration.

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