Highlights:1. It was the first time 7 operating modes were achieved on the same engine.2. 7 operating modes covers conventional spark ignition and advanced controlled autoignition in two-stroke and 4-stroke cycles.3. The thermodynamic cycle, combustion process and efficiencies are analysed and presented. ABSTRACTIn order to develop more efficient and cleaner gasoline engines, a number of new engine operating strategies have been proposed and researched on different engines, including the spark ignition (SI) and controlled autoignition (CAI) or HCCI in both 2-stroke and 4-stroke cycles in a poppet valve engine. In this work, a single cylinder direct injection gasoline engine equipped with an electro-hydraulic valve-train system has been commissioned and used to achieve seven different operating modes, including: 4-stroke throttle-controlled SI, 4-stroke intake valve throttled SI, 4-stroke positive valve overlap SI, 4-stroke negative valve overlap CAI, 4-stroke exhaust rebreathing CAI, 2-stroke CAI and 2-stroke SI. Their performance and emission characteristics were analysed and compared at a typical engine calibration operating condition of 1500rpm and 3.6bar IMEP in 4-stroke or 1.8bar IMEP in 2-stroke. Results show that 4-stroke positive valve overlap SI, 4-stroke NVO CAI and exhaust rebreathing CAI modes have better fuel economy and lower NOx emissions than the conventional throttled 4-stroke SI operation. The 2-stroke CAI operation was found to produce higher combustion efficiency and lower ISFC but lower brake efficiency than the 4-s-stroke operations at the same power output due to the supercharger's efficiency. But, at the same IMEP as the 4-stroke operation, the 2-stroke CAI operation results in 29% reduction in BSFC, indicating its potential synergy with highly downsized direct injection gasoline engines for much better fuel economy and performance.

This paper describes the London Site Specific Air Temperature prediction model, which comprises of a suite of artificial neural network (ANN) models to predict site-specific hourly air temperature within the Greater London Area (GLA). The model was developed using a back-propagation ANN model based on hourly air temperature measurements at 77 fixed temperature stations (FTS) and hourly meteorological data (off-site variables) from Heathrow; it also includes six on-site variables calculated for each FTS. The temporal and spatial validity of the model was tested using data measured 7 years later from the original dataset, which include new FTS locations. It was found that site-specific hourly air temperature prediction is within accepted range and improves considerably for average daily and monthly values. Therefore, the model can be used with confidence to predict daily and seasonal variations of air temperature within the GLA and in particular for the calculation of monthly and annual heating degree days (HDD) and cooling degree hours (CDH). It was found that as expected HDD increase and CDH decrease with distance from the urban heat island centre point; however, all variations cannot be explained with distance and six key on-site variables namely aspect ratio, surface albedo, plan density ratio, green density ratio, fabric density ratio and thermal mass have been identified to explain the remaining variation. Practical applications: Research studies have confirmed the extent of Urban Heat Island (UHI) within many cities in Europe. Studies have also confirmed the impact of the UHI on energy demand by buildings. There is therefore need to consider this in the design of building by using site-specific external temperatures in the energy calculations for urban buildings. This paper describes the development of a model, which can generate site-specific air temperature in a large number of locations in London. The model's predictions can be used for the calculation of HDD and CDH for any base temperature across London using any Heathrow weather file for a specific year, design years or future climate years; such values can be used for the calculation of site specific building heating and cooling loads.

To reduce the mechanical property variation of A380 alloy produced by high pressure die casting, high shear melt conditioning (HSMC) technology was developed and applied to the melt prior to pouring into shot sleeve. Experimental results show that with application of HSMC, the variation of elongation was decreased from 21.8% to 13.9%, and yield strength variation was reduced from 5.5% to 3.6%. The improved property variation is attributed to enhanced nucleation both in the shot sleeve and the die-cavity, and to the improved distribution of porosity and secondary phases as a benefit of high shear induced grain refinement. With application of high shear, large number of the Spinel phase (MgAl2O4) particles with double size distribution in average diameter of 80nm and 300nm were formed. Due to the good orientation relationship and small misfit between (alpha)-Al and MgAl2O4, the particles act as effective nuclei in shot sleeve and die cavity respectively.

No abstract

No abstract