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The absence of combustion information continues to be one of the key obstacles to the intelligent development of engines. Currently, the cost of integrating cylinder pressure sensors remains too high, prompting attention to methods for extracting combustion information from existing sensing data. Mean-value combustion models for engines are unable to capture changes of combustion parameters. Furthermore, the methods of reconstructing combustion information using sensor signals mainly depend on the working state of the sensors, and the reliability of reconstructed values is directly influenced by sensor malfunctions. Due to the concentration of operating conditions of hybrid vehicles, the reliability of priori calibration map has increased. Therefore, a combustion information reconstruction method based on priori calibration information and the fused feature deviations of existing sensing signals is proposed and named the "Deviation-based Centroid Displacement Method" (DCDM).

Two-stroke cycle is one of the most effective methods to increase the torque and power output of a four-stroke engine due to the doubled firing frequency compared to four-stroke cycle at the same engine speed. As the two-stroke cycle lacks separate intake and exhaust strokes, the positive pressure difference between intake and exhaust ports is required to drive fresh charge into the cylinder, and is affected by intake port structures due to the different amounts of short-circuited fresh charge during scavenging process. To evaluate the effects of intake port structures on the high-load performance of a boosted poppet-valved two-stroke diesel engine, one-dimensional gas dynamic model and three-dimensional computational fluid dynamics model were established and used to predict the high-load performance of the boosted two-stroke diesel engine with top-entry intake ports, inclined side-entry intake ports, and side-entry intake ports, respectively.

This study aims to improve the dual fuel combustion for low/zero carbon fuels. Seven cases were tested in a single cylinder optical engine and their ignition and combustion characteristics are compared. The baseline case is the conventional diesel combustion. Four cases are diesel-gas (compressed natural gas) dual-fuel combustion operations, and two cases are diesel-hythane combustion. The diesel fuel injection process was visualized by a high-speed copper vapour laser. The combustion processes were recorded with a high-speed camera at 10000 Hz with an engine speed of 1200 rpm. The high-speed recordings for each case included 22 engine cycles and were postprocessed to create one spatial overlapped average combustion image. The average combustion cycle images were then further thresholded and these images were then used in a new method to analyze the cycle-to-cycle variation in a dimensionless, for all cases comparable value.

An appropriate energy management strategy can further reduce the fuel consumption of P2 hybrid electric vehicles (HEV) with simple hybrid configuration and low cost. The rule-based real-time energy management strategy dominates the energy management strategies utilized in commercial HEVs, due to its robustness and low computational loads. However, its performance is sensitive to the setting of parameters and control actions. To further improve the fuel economy of a P2 HEV, the energy management strategy of the HEV has been re-designed based on the globally optimal control theory. An optimization strategy model based on the longitudinal dynamics of the vehicle and Bellman’s dynamic programming algorithm was established in this research and an optimal power split in the dual power sources including an internal combustion engine (ICE) and an electric machine at a given driving cycle was used as a benchmark for the development of the rule-based energy management strategy.

Pumping Mean Effective Pressure (PMEP) is the main factor limiting the improvement of thermal efficiency in a spark-ignition (SI) engine under low load. One of the ways to reduce the pumping loss under low load is to use Cylinder DeActivation (CDA). The CDA aims at reducing the firing density (FD) of the SI engine under low load operation and increasing the mass of air-fuel mixture within one cycle in one cylinder to reduce the throttling effect and further reducing the PMEP. The multi-stroke cycles can also reduce the firing density of the SI engine after some certain reasonable design, which is feasible to improve the thermal efficiency of the engine under low load in theory. The research was carried out on a calibrated four-cylinder SI engine simulation platform. The thermal efficiency improvements of the 6-stroke cycle and 8-stroke cycle to the engine performance were studied compared with the traditional 4-stroke cycle under low load conditions.

A 2-stroke boosted uniflow scavenged direct injection gasoline (BUSDIG) engine was researched and developed at Brunel University London to achieve higher power-to-mass ratio and thermal efficiency. In the BUSDIG engine concept, the intake scavenge ports are integrated to the cylinder liner and controlled by the movement of piston top while exhaust valves are placed in the cylinder head. Systematic studies on scavenging ports, intake plenum, piston design, valve opening profiles and fuel injection strategies have been performed to investigate and optimise the scavenging performance and in-cylinder fuel/air mixing process for optimised combustion process. In order to achieve superior power performance with higher thermal efficiency, the evaluation and optimisation of the boost system for a 1.0 L 2-cylinder 2-stroke BUSDIG engine were performed in this study using one dimensional (1D) engine simulations.

Lean-burn combustion is an effective method for increasing the thermal efficiency of gasoline engines fueled with stoichiometric fuel-air mixture, but leads to an unacceptable level of high cyclic variability before reaching ultra-low nitrogen oxide (NOx) emissions emitted from conventional gasoline engines. Multi-point micro-flame ignited (MFI) hybrid combustion was proposed to overcome this problem, and can be can be grouped into double-peak type, ramp type and trapezoid type with very low frequency of appearance. This research investigates the micro-flame ignition stages of double-peak type and ramp type MFI combustion captured by high speed photography. The results show that large flame is formed by the fast propagation of multi-point flame occurring in the central zone of the cylinder in the double-peak type. However, the multiple flame sites occur around the cylinder, and then gradually propagate and form a large flame accelerated by the independent small flame in the ramp type.

Two-stroke engines have to face the problems of insufficient charge for short intake time and the loss of intake air caused by long valve overlap. In order to promote the power of a two-stroke poppet valve diesel engine, measures are taken to help optimize intake port structure. In this work, the scavenging and combustion processes of three common types of intake ports including horizontal intake port (HIP), combined swirl intake port (CSIP) and reversed tumble intake port (RTIP) were studied and their characteristics are summarized based on three-dimensional simulation. Results show that the RTIP has better performance in scavenging process for larger intake air trapped in the cylinder. Its scavenging efficiency reaches 84.7%, which is 1.7% higher than the HIP and the trapping ratio of the RTIP reaches 72.3% due to less short-circuiting loss, 11.2% higher than the HIP.

Engine downsizing is an effective technology to lower automotive CO2 emissions. However, the high load low speed regions are plagued with knocking combustion that are usually overcome by retarding the ignition. This interferes with the efficiency gains due to very late combustion. This paper reports the use of Exhaust Gas Recirculation (EGR) on a Ford Ecoboost 1l downsized gasoline turbocharged direct injection (GTDI) engine to improve efficiency by optimising combustion phasing unlocked by the improved knock resistance with EGR dilution. Further ignition system upgrades are tested for impact towards further efficiency improvements. 75mJ (standard) and 120mJ (high energy) ignition systems were compared. The experimental results showed that the brake specific fuel consumption (BSFC) can be improved by 5.6% with EGR dilution at 25%. When considering combined effects of EGR and high energy ignition upon engine fuel economy, the BSFC gain improves to 7.9%.

This paper deals with the experimental and numerical investigation of a 2.0 litre single cylinder Heavy Duty Diesel Engine fuelled by natural gas and diesel oil in Dual Fuel mode. Due to the gaseous nature of the main fuel and to the high compression ratio of the diesel engine, reduced emissions can be obtained. An experimental study has been carried out at three different load level (25%, 50% and 75% of full engine load). Basing on experimental data, the authors recreated a 45° mesh sector of the engine cylinder and performed CFD simulations for the cases at 50% and 75% load levels. Numerical simulations were carried out on the 3D code Ansys FORTE. The aim of this work is to study combustion phenomena and, in particular, the interaction between natural gas and diesel oil, respectively represented by methane and n-dodecane. A reduced kinetic scheme for methane auto-ignition was implemented while for n-dodecane two set of reactions were utilised.

Controlled Auto-Ignition (CAI), also known as Homogeneous Charge Compression Ignition (HCCI), can improve the fuel economy of gasoline engines and simultaneously achieve ultra-low NOx emissions. However, the difficulty in combustion phasing control and violent combustion at high loads limit the commercial application of CAI combustion. To overcome these problems, stratified mixture, which is rich around the central spark plug and lean around the cylinder wall, is formed through port fuel injection and direct injection of gasoline. In this condition, rich mixture is consumed by flame propagation after spark ignition, while the unburned lean mixture auto-ignites due to the increased in-cylinder temperature during flame propagation, i.e., stratified flame ignited (SFI) hybrid combustion.

The two-stroke operation is one of the most effective approaches to significantly increase the torque and power of a 4-stroke engine without the necessary requirement of intensifying the engine. Scavenging process is one of the key factors determining the performance of the two-stroke engine. In this work, a structure of top entry intake ports with poppet valves was employed on a 2-stroke single cylinder diesel engine with the conventional horizontal intake ports replaced. By this way, the reversed tumble flows in the cylinder were formed during the intake process to improve the scavenging performance of 2-stroke operation. In the meanwhile, the effects of valve timings and intake port structures on scavenging processes were estimated respectively through the1D and 3D simulation of the gas exchange process.

Poppet-valve two-stroke gasoline engines can increase the specific power of their four-stroke counterparts with the same displacement and hence decrease fuel consumption. However, knock may occur at high loads. Therefore, the combustion with stratified lean mixture was proposed to decrease knock tendency and improve combustion stability in a poppet-valve two-stroke direct injection gasoline engine. The effect of intake pressure and split injection on fuel distribution, combustion and knock intensity in lean mixture conditions at high loads was simulated with a three-dimensional computational fluid dynamic software. Simulation results show that with the increase of intake pressure, the average fuel-air equivalent ratio in the cylinder decreases when the second injection ratio was fixed at 70% at a given amount of fuel in a cycle.

Engine downsizing is one of the most effective means to improve the fuel economy of spark ignition (SI) gasoline engines because of lower pumping and friction losses. However, the occurrence of knocking combustion or even low-speed pre-ignition at high loads is a severe problem. One solution to significantly increase the upper load range of a 4-stroke gasoline engine is to use 2-stroke cycle due to the double firing frequency at the same engine speed. It was found that a 0.7 L two-cylinder 2-stroke poppet valve gasoline engine equipped with a two-stage serial boosting system, comprising a supercharger and a downstream turbocharger, could replace a 1.6 L naturally aspirated 4-stroke gasoline engine in our previous research, but its fuel economy was close to that of the 4-stroke engine at upper loads due to knocking combustion.

In this paper, an experimental study was performed to investigate characteristics of flame propagation and knocking combustion of hydrous (10% water content) and anhydrous ethanol at different air/fuel ratios in comparison to RON95 gasoline. Experiments were conducted in a full bore overhead optical access single cylinder port-fuel injection spark-ignition engine. High speed images of total chemiluminescence and OH* emission was recorded together with the in-cylinder pressure, from which the heat release data were derived. The results show that under the stoichiometric condition anhydrous ethanol and wet ethanol with 10% water (E90W10) generated higher IMEP with at an ignition timing slightly retarded from MBT than the gasoline fuel for a fixed throttle position. Under rich and stoichiometric conditions, the knock limited spark timing occurred at 35 CA BTDC whereas both ethanol and E90W10 were free from knocking combustion at the same operating condition.

Controlled Auto-Ignition (CAI), also known as Homogeneous Charge Compression Ignition (HCCI), has the potential to improve gasoline engines’ efficiency and simultaneously achieve ultra-low NOx emissions. Two of the primary obstacles for applying CAI combustion are the control of combustion phasing and the maximum heat release rate. To solve these problems, dimethyl ether (DME) was directly injected into the cylinder to generate multi-point micro-flame through compression in order to manage the entire heat release of gasoline in the cylinder through port fuel injection, which is known as micro-flame ignited (MFI) hybrid combustion.

In order to meet increasingly stringent emissions standards and lower the fuel consumption of heavy-duty (HD) vehicles, significant efforts have been made to develop high efficiency and clean diesel engines and aftertreatment systems. However, a trade-off between the actual engine efficiency and nitrogen oxides (NOx) emission remains to minimize the operational costs. In addition, the conversion efficiency of the diesel aftertreatment system decreases rapidly with lower exhaust gas temperatures (EGT), which occurs at low load operations. Thus, it is necessary to investigate the optimum combustion and engine control strategies that can lower the vehicle’s running costs by maintaining low engine-out NOx emissions while increasing the conversion efficiency of the NOx aftertreament system through higher EGTs.

Modern heavy duty diesel engines can well extend the goal of 50% brake thermal efficiency by utilizing waste heat recovery (WHR) technologies. The effect of an ORC WHR system on engine brake specific fuel consumption (bsfc) is a compromise between the fuel penalty due to the higher exhaust backpressure and the additional power from the WHR system that is not attributed to fuel consumption. This work focuses on the fuel efficiency benefits of installing an ORC WHR system on a heavy duty diesel engine. A six cylinder, 7.25ℓ heavy duty diesel engine is employed to experimentally explore the effect of backpressure on fuel consumption. A zero-dimensional, detailed physical ORC model is utilized to predict ORC performance under design and off-design conditions.

Mechanical load and thermal load are the two main barriers limiting the engine power output of heavy duty (HD) diesel engines. Usually, the peak cylinder pressure could be reduced by retarding combustion phasing while introducing the drawback of higher thermal load and exhaust temperature. In this paper, Miller cycle with late intake valve closing was investigated at high speed high load condition (77 kW/L) on a single cylinder HD diesel engine. The results showed the simultaneous reduction of mechanical and thermal loads. In the meanwhile, higher boosting pressure was required to compensate the Miller loss of the intake charge during intake and compression process. The combustion temperature, cylinder pressure, exhaust temperature and NOx emission were reduced significantly with Miller cycle at the operating condition. Furthermore, the combustion process, smoke number and fuel consumption were analysed.

As the emission regulations for internal combustion engines are becoming increasingly stringent, different solutions have been researched and developed, such as dual injection systems (combined port and direct fuel injection), split injection strategies (single and multiple direct fuel injection) and different intake air devices to generate an intense in-cylinder air motion. The aim of these systems is to improve the in-cylinder mixture preparation (in terms of homogeneity and temperature) and therefore enhance the combustion, which ultimately increases thermal efficiency and fuel economy while lowering the emissions. This paper describes the effects of dual injection systems on combustion, efficiency and emissions of a downsized single cylinder gasoline direct injection spark ignited (DISI) engine. A set of experiments has been conducted with combined port fuel and late direct fuel injection strategy in order to improve the combustion process.